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 physica status solidi (c)   [SJR: 0.392]   [H-I: 39]   [1 followers]  Follow         Hybrid journal (It can contain Open Access articles)    ISSN (Print) 1862-6351 - ISSN (Online) 1610-1642    Published by John Wiley and Sons  [1612 journals]
• Analysis of the experimental data for impurity-band conduction in Mn-doped
InSb
• Authors: Yasutomo Kajikawa
Abstract: The experimental data of the temperature-dependent Hall-effect measurements on Mn-doped p -type InSb samples, which exhibit the anomalous sign reversal of the Hall coefficient to negative at low temperatures, have been analyzed on the basis of the nearest-neighbor hopping model in an impurity band. It is shown that the anomalous sign reversal of the Hall coefficient to negative can be well explained with assuming the hopping Hall factor in the form of Ahop = (kBT /J3) exp (KNNHT3/T) with the negative sign of J3. (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-11-14T05:52:56.084104-05:
DOI: 10.1002/pssc.201600215

• Influence of Urbach tail on the refractive index of p-SnS thin films
• Authors: Yashika Gupta; P. Arun
Abstract: Tin sulphide thin films of p-type conductivity were grown on glass substrates. The refractive index of the as grown films were calculated using both transmission and spectroscopic ellipsometry (SE) data. The SE data was fit using Tauc Lorentz model which showed that the films did not absorb for λ > 700 nm. The variation in all the films refractive index with respect to wave- length, i.e. the dispersion behaviour of the films in region 700 < λ < 1000 nm were found to follow the Wemple-Dedomenico (WDD) single oscillator model. The optical properties of the films were found to be closely related to the structural properties of the films. Intrinsic crystal disorders, tin vacancies in p-SnS thin films leads to ap- pearance of defect levels (Urbach tail) within the band- gap. The band-gap and the band tail's spread, intimately controls the refractive index of the films. (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-11-14T05:52:55.012211-05:
DOI: 10.1002/pssc.201600207

• Single crystalline SnO2 thin films grown on m -plane sapphire substrate by
mist chemical vapor deposition
• Authors: Zenji Yatabe; Takaaki Tsuda, Junya Matsushita, Takehide Sato, Tatsuya Otabe, Koji Sue, Shoji Nagaoka, Yusui Nakamura
Abstract: Tin dioxide (SnO2) thin films, as a candidate for realizing next-generation electrical and optical devices, were grown on 2-inch diameter m -plane sapphire substrates by mist chemical vapour deposition at atmospheric pressure. The SnO2 thin films were characterized by scanning electron microscope (SEM), atomic force microscope (AFM), X-ray diffraction (XRD) in θ–2θ and ϕ scanning modes, and electron backscatter diffraction (EBSD). Although the SEM and AFM images showed a relatively rough surface morphology, it was found from the XRD and EBSD measurements that SnO2 films were epitaxially grown on the substrates under optimised growth condition. Epitaxial growth of SnO2 thin film growth at three typical areas on the substrate was confirmed by the EBSD measurements. It is likely that the single crystalline SnO2 (001) thin film was formed across the 2-inch sapphire substrate. Finally, the second SnO2 layer was overgrown on the above single crystalline SnO2 thin film, which functioned as a buffer layer. This method which drastically improved surface roughness of the second SnO2 layer. (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-11-14T05:52:54.020985-05:
DOI: 10.1002/pssc.201600148

• Hall factor for hopping conduction in n- and p-type GaN
• Authors: Yasutomo Kajikawa
Abstract: The experimental data of the temperature-dependent Hall-effect measurements on a Si-doped n -type and a Mg-doped p -type sample of GaN, both of which exhibit the characteristic of hopping conduction among impurity sites, have been analyzed. For the n -GaN sample, Efros-Shklovskii variable-range hopping among donor sites has been proved to be the dominant hopping mechanism, where the hopping drift mobility can be described as μhop ∝ T–1 exp [–(TES/T)1/2]. It is shown that the anomalous increase of the absolute value of the Hall coefficient with decreasing temperature below 25 K can be well fitted with assuming the hopping Hall factor in the form of Ahop ∝ –exp [KES(TES/T)1/2]. For the p -GaN sample, on the other hand, nearest-neighbor hopping among acceptor sites has been proved to be the dominant hopping mechanism, where the hopping drift mobility can be described as μhop ∝ T–3/2 exp (–T3/T). It is shown that the anomalous sign change of the Hall coefficient to negative below 110 K can be well explained with assuming the hopping Hall factor in the form of Ahop ∝ T exp (KNNHT3/T) with the negative sign. (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-11-14T05:52:52.923459-05:
DOI: 10.1002/pssc.201600129

• Design of all-fiber thulium laser in CW and QCW mode of operation for
medical use
• Authors: Debasis Pal; Ranjan Sen, Atasi Pal
Abstract: Fiber laser below 2000 nm is required for effective urological applications because of strong water absorption. Design of all-fiber thulium laser at this wavelength under pumping at 793 nm, utilizing cross relaxation mechanism, demands rigorous optimization of parameters as highly concentrated thulium doped silica has maximum gain at around 2010 nm. Length of the active fiber and the reflectivity of the output coupler have been optimized for maximum slope efficiency and output power. Counter propagating pumping scheme has been considered for better thermal management and good lasing efficiency. Spectral property and time domain response of the laser have been studied at different levels of output power. Lasing characteristics at 1910 nm, 1950 nm, 2000 nm and 2100 nm have also been investigated. The continuous wave lasing at 1950 nm with output power of 16.1 W having slope efficiency of 65.6% has been demonstrated. In quasi-continuous wave mode of operation, pulse energy in the range of 400 µJ to 5 mJ has been measured for the peak power of 16 W. The designed laser has been used successfully in human kidney stone breaking. (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-11-14T05:52:51.723509-05:
DOI: 10.1002/pssc.201600127

• Applying high-throughput computational techniques for discovering
next-generation of permanent magnets
• Authors: P. Nieves; S. Arapan, G. C. Hadjipanayis, D. Niarchos, J. M. Barandiaran, S. Cuesta-López
Abstract: The uncertainty in rare-earth market resulted in worldwide efforts to develop rare-earth-lean/free permanent magnets. In this paper, we discuss about this problem and analyse how advances in computational and theoretical condensed matter physics could be essential in the development of a new generation of high-performance permanent magnets via high-throughput computational technique for material design. Additionally, we show that an adaptive genetic algorithm based methodology could be a useful tool for finding new magnetic phases. In particular, we apply such approach to Fe0.75Sn0.25 compound recovering well-known experimental results and also finding new low-energy magnetic metastable structures. (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-11-14T05:52:50.49461-05:0
DOI: 10.1002/pssc.201600103

• Infrared defect dynamics – radiation induced complexes in silicon
crystals grown by various techniques
• Authors: Naohisa Inoue; Takahide Sugiyama, Yasunori Goto, Kaori Watanabe, Hirofumi Seki, Yuichi Kawamura
Abstract: Radiation induced point defect-light element impurity complexes, basically CiOi, are used widely for lifetime control in power devices for hybrid cars. Recently, not only CZ, but also FZ and epitaxial wafers have been examined as candidates. It has been suggested by luminescence study that CiOi behaved differently during annealing in crystals from different origins. The behavior of CiOi (and VO) during annealing was examined by highly sensitive infrared absorption spectroscopy (IR). CiOi concentration ([CiOi]) after irradiation depended strongly on the growth techniques and as-grown carbon ([C]) and oxygen ([O]) concentrations. In the basic C-rich MCZ case, CiOi and VO reacted with each other and decreased steadily with annealing temperature increase. They mostly disappeared at 400 °C. In low [C] CZ case, CiOi residual ratio (RR = α400°C/αRT, α is the absorption coefficient) was higher, probably due to low reaction probability of much lower [CiOi] with VO. In FZ silicon, CiOi residual ratio was low, probably due to rapid break. Thus, IR made systematic and quantitative analysis compared to the luminescence study. In nitrogen-doped FZ silicon, NV was observed in as-grown crystals. N2 was modified by irradiation and complicated reaction took place with V or I by annealing. This would affect the CiOi behavior. (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-11-14T05:52:49.277758-05:
DOI: 10.1002/pssc.201600067

• On physical properties of nanoparticles: size effect and scale of
nanoobjects
• Authors: V. V. Uglov; I. L. Doroshevich, N. T. Kvasov, G. E. Remnev, V. I. Shymanski
Abstract: A transition border between macroscopic and nanoscale states of solids associated with change of its physical properties is certain to exist. The change of mechanical, magnetic, thermal and other properties of nanoparticles may be due to the surface tension, decrease in coordination number in the top-surface layer, rebuilding of the electron shell structure, change of the symmetry group of the crystal lattice and the binding energy. Different defects of the structure can also have significant influence on the physical properties of nanoparticles. A violation of the Neumann principle with decrease of the crystal sized is constant discussed in the literature. In the present work the dependence of elastic module, Debye's temperature, melting point, thermal expansion coefficient, magnetic structure on a size of metal nanoparticles (first of all iron nanoparticles) is discussed. On the basis of the obtained results the scale border between nano- and macroscopic states is justified. In the present work the peculiarity of the physical processes (melting, diffusion, defects complexes formation) occurring in nanoparticles and nanomaterials is discussed. (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-11-14T05:52:47.824086-05:
DOI: 10.1002/pssc.201600039

• Effect of surface passivation on the electrical performance of AlGaN/GaN
high-electron-mobility transistors with slant field plates fabricated
using deep-UV lithography
• Authors: Lu-Che Huang; Chia-Hua Chang, Yueh-Chin Lin, Heng-Tung Hsu
Abstract: AlGaN/GaN high-electron-mobility transistors (HEMTs) have been extensively applied for high power applications at high frequencies. To further improve the device performance, field plates and passivation layers are commonly integrated with the device technology. This paper is to investigate the effects of surface passivation thickness on the electrical performance of AlGaN/GaN HEMTs with slant field plates fabricated using deep-UV technology. As a benchmark, the device without nitride passivation exhibited a peak transconductance of 214 mS/mm and a breakdown voltage of 122 V with an output power of 5.0 W/mm at 8 GHz. For the passivated devices, it is observed that the existence of the silicon nitride passivation layer helps to improve the DC characteristics of the devices in terms of the lower drain current collapse, higher maximum DC transconductance, and higher maximum drain current. RF wise, the devices with passivation suffer from lower fT and fMAX due to the increase in the gate capacitances. However, an improvement of RF output power was observed for devices with passivation layer thickness up to 300 nm. (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-11-14T05:52:46.128551-05:
DOI: 10.1002/pssc.201600230

• Comprehensive characterization of AlGaN/GaN metal-oxide-semiconductor
high-electron mobility transistors with TiO2 gate dielectric
• Authors: Yu-Shyan Lin; Chi-Che Lu, Wei-Chou Hsu
Abstract: AlGaN/GaN metal-oxide-semiconductor high-electron mobility transistors (MOS-HEMTs) on Si substrates with TiO2 gate dielectrics are fabricated. The dc and power characteristics of AlGaN/GaN MOS-HEMTs are compared with that of metal-gate HEMTs fabricated on the same material. The gate leakage current for the MOS-HFET is more than two orders of magnitude smaller than for the HEMT at 300 K. The high-speed performance potential of the MOS-HEMT with an fT = 10.44 GHz and an fmax = 13.8 GHz is confirmed. The MOS-HEMT shows higher extrinsic transconductance, breakdown voltage, high-frequency and power characteristics relative to the HEMT. Furthermore, experimental results reveal that this studied MOS-HEMT is feasible for use at high temperatures. (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-11-03T07:30:44.730948-05:
DOI: 10.1002/pssc.201600227

• Titanium oxide films deposited by e-beam evaporation as n-type electrode
for solar cell applications
• Authors: Rosa Chierchia; Francesca Menchini, Luca Serenelli, Pietro Mangiapane, Tiziana Polichetti, Mario Tucci
Abstract: TiO2 is a n-type oxide semiconductor used in many fields of chemistry and engineering, included dye sensitized and organic solar cells. Different methods have been investigated to prepare TiO2 films, nevertheless its poor electrical and optical characteristics hampers its use as a transparent conductor oxide. In this work thin TiO2 film obtained by e-beam evaporation and thermally annealed at different temperatures were studied using different characterization techniques, in order to evaluate its use as emitter layer or back contact in silicon based heterojunction solar cells. By Raman analysis we found the TiO2 films showed mainly the presence of anatase crystal structure once thermally annealed at T > 400 °C. Electrical and optical characterization of the thermally annealed samples showed that the best results consisted in a resistivity of around 10-2 Ωcm, a mobility of 3 cm2/Vs and carrier concentration of 1019/cm3. From capacitance-voltage characteristics of TiO2 /p-c-Si, the built-in potential has been evaluated in order to assess the band alignment with crystalline silicon. Good quality titanium oxide films by using e-beam evaporation deposition technique followed by thermal annealing have been obtained with physical and electrical properties desirable for photovoltaic applications. (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-11-03T07:30:43.84762-05:0
DOI: 10.1002/pssc.201600119

• The effect of helium irradiation on the thermal evolution of the
microstructure of nc-ZrN
• Authors: Arno Janse van Vuuren; Alexander Sohatsky, Vladimir Uglov, Vladimir Skuratov, Alexey Volkov
Abstract: ZrN is a candidate material for use as inert matrix fuel host for the burn-up of plutonium and other minor actinides, waste products commonly present in spent nuclear fuel. These materials will operate within the nuclear reactor core and will therefore be subject to various types of radiation, high temperatures and a corrosive environment. Ceramics employed in the nuclear reactor environment will accumulate helium via (n, α) reactions. Nanocrystalline ZrN irradiated with 30 keV He to fluences between 1016 and 5×1016 cm–2to simulate the effects of alpha particle irradiation. The He irradiated sam- ples were annealed at temperatures between 600 and 1000 °C and were analysed using TEM and selected area diffraction. The results indicated that post irradiation heat treatment induces exfoliation at a depth that corresponds to the end-of-range of 30 keV He ions. TEM analysis of He suggests that nanocrystalline ZrN is prone to the formation of He blisters which may ultimately lead material failure. The results also suggest that the doping of nc-ZrN with He aids the transformation from a nanocrystalline to microcrystalline state during heat treatment. (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-11-03T07:30:42.969697-05:
DOI: 10.1002/pssc.201600027

• Effect of Nb doping on the structural, morphological, optical and
electrical properties of RF magnetron sputtered In2O3 nanostructured films

• Authors: R. Reshmi Krishnan; S. R. Chalana, S. Suresh, S. K. Sudheer, C. Sudarsanakumar, M. C. Santhosh Kumar, V. P. Mahadevan Pillai
Abstract: Undoped and niobium (Nb) doped indium oxide (In2O3) thin films are prepared by radio frequency magnetron sputtering technique. The effect of Nb on the structural, morphological, optical and electrical properties of In2O3films are analyzed using techniques such as X-ray diffraction (XRD), micro-Raman spectroscopy, X-ray photoelectron spectroscopy, atomic force microscopy, field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy, UV–visible spectroscopy, spectroscopic ellipsometry, photoluminescence spectroscopy and Hall effect measurements. XRD analysis reveals that the as-deposited undoped and Nb doped films are polycrystalline in nature with cubic bixbyite structure. Raman analysis supports the presence of cubic bixbyite structure of In2O3in the films. XPS analysis shows a decrease of oxygen deficiency due to Nb and the existence of Nb as Nb4+ in the In2O3lattice. The band gap energy of the films increases with increase in Nb concentration. PL spectra reveal intense UV and visible emissions in all the films. Optical constants of the films are determined using spectroscopic ellipsometry. The thickness of films estimated using FESEM and ellipsometry are in good agreement. The carrier concentration, mobility and nature of carriers are measured using Hall measurement technique in Van der Pauw configuration at room temperature. (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-11-03T07:30:41.934763-05:
DOI: 10.1002/pssc.201600095

• Electrodynamic properties of porous PZT-Pt films at terahertz frequency
range
• Authors: Gennady A. Komandin; Oleg E. Porodinkov, Igor E. Spektor, Alexander A. Volkov, Konstantin A. Vorotilov, Dmitry S. Seregin, Alexander S. Sigov
Abstract: Electrodynamics of Si-SiO2-TiO2-Pt-PZT heterostructures is studied in the frequency range from 5 to 5000 cm-1 by monochromatic BWO (backward wave oscillator) and infrared Fourier-transform spectroscopy techniques to derive the dielectric characteristics of the sol-gel porous ferroelectric PbZr0.48Ti0.52O3 films. Broad frequency band dielectric response of PZT films with different density is constructed using the oscillator dispersion models. The main contribution to the film permittivity is found to form at frequencies below 100 cm-1 depending strongly and non-linearly on the film medium density. (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-11-03T07:30:40.65731-05:0
DOI: 10.1002/pssc.201600211

• Field- and irradiation-induced phenomena in memristive nanomaterials
• Authors: A. N. Mikhaylov; E. G. Gryaznov, A. I. Belov, D. S. Korolev, A. N. Sharapov, D. V. Guseinov, D. I. Tetelbaum, S. V. Tikhov, N. V. Malekhonova, A. I. Bobrov, D. A. Pavlov, S. A. Gerasimova, V. B. Kazantsev, N. V. Agudov, A. A. Dubkov, C. M. M. Rosário, N. A. Sobolev, B. Spagnolo
Abstract: The breakthrough in electronics and information technology is anticipated by the development of emerging memory and logic devices, artificial neural networks and brain-inspired systems on the basis of memristive nanomaterials represented, in a particular case, by a simple ‘metal–insulator–metal’ (MIM) thin-film structure. The present article is focused on the comparative analysis of MIM devices based on oxides with dominating ionic (ZrOx, HfOx) and covalent (SiOx, GeOx) bonding of various composition and geometry deposited by magnetron sputtering. The studied memristive devices demonstrate reproducible change in their resistance (resistive switching – RS) originated from the formation and rupture of conductive pathways (filaments) in oxide films due to the electric-field-driven migration of oxygen vacancies and / or mobile oxygen ions. It is shown that, for both ionic and covalent oxides under study, the RS behaviour depends only weakly on the oxide film composition and thickness, device geometry (down to a device size of about 20×20 μm2). The devices under study are found to be tolerant to ion irradiation that reproduces the effect of extreme fluences of high-energy protons and fast neutrons. This common behaviour of RS is explained by the localized nature of the redox processes in a nanoscale switching oxide volume. Adaptive (synaptic) change of resistive states of memristive devices is demonstrated under the action of single or repeated electrical pulses, as well as in a simple model of coupled (synchronized) neuron-like generators. It is concluded that the noise-induced phenomena cannot be neglected in the consideration of a memristive device as a nonlinear system. The dynamic response of a memristive device to periodic signals of complex waveform can be predicted and tailored from the viewpoint of stochastic resonance concept. (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-10-21T07:20:11.857945-05:
DOI: 10.1002/pssc.201600083

• Synthesis and luminescent properties of magnesium gallate spinel doped
with Mn2+ and Eu3+ ions
• Authors: Andriy Luchechko; Oleh Kravets
Abstract: Ceramic samples of pure MgGa2O4, MgGa2O4: 0.05 mol.% Mn and MgGa2O4: 0.05 mol.% Mn, 5 mol.% Eu were synthesized via high-temperature solid state reaction method. X-ray diffraction measurements confirmed formation of spinel structure with Fd3m space group in all investigated samples. Clearly polycrystalline nature of ceramic samples with grain distribution from 1 to 5 μm was confirmed with SEM investigations. An intense broad band that excites in fundamental absorption edge has a maximum around 505 nm and corresponds to emission of Mn2+ ions. A charge transfer band (from O2– to Eu3+) with maximum at about 260 nm was found in the excitation spectra of Mn2+ and Eu3+ co-doped samples. Luminescence band around 430 nm that corresponds to emission from host defects was found in all investigated samples. Excitation and emission of Eu3+ ions is presented by sharp lines with the most intense at 393 and 617 nm which are associated with 7F05L6 and 5D07F2 transitions in Eu3+ ions, respectively. (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-10-06T05:30:13.69437-05:0
DOI: 10.1002/pssc.201600146

• Growth parameter enhancement for MoS2 thin films synthesized by pulsed
laser deposition
• Authors: Martha I. Serna; Salvador Moreno, Marissa Higgins, Hyunjoo Choi, Majid Minary-Jolandan, Manuel A. Quevedo-Lopez
Abstract: Two-dimensional materials such as graphene and MoS2 have been the main focus of intense research efforts over the past few years. The most common method of exfoliating these materials, although efficient for lab-scale experiments, is not acceptable for large area and practical applications. Here, we report the deposition of MoS2 layered films on amorphous (SiO2) and crystalline substrates (sapphire) using a pulsed laser deposition (PLD) method. Increased substrate temperature (∼700 °C) and laser energy density (>530 mJ /cm2) promotes crystalline MoS2 films < 20 nm, as demonstrated by fast Fourier transform (FFT) and transmission electron microscopy (TEM). The method reported here opens the possibility for large area layered MoS2 films by using a laser ablation processes. (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-10-06T05:20:15.098452-05:
DOI: 10.1002/pssc.201600091

• MeV ion irradiation effects on the luminescence properties of Si-implanted
SiO2-thin films
• Authors: T. Chulapakorn; I. Sychugov, S. S. Suvanam, J. Linnros, D. Primetzhofer, A. Hallén
Abstract: The effects of MeV heavy ion irradiation at varying fluence and flux on excess Si, introduced in SiO2 by keV ion implantation, are investigated by photoluminescence (PL). From the PL peak wavelength (λ) and decay lifetime (τ), two PL sources are distinguished: i) quasi-direct recombination of excitons of Si-nanoparticles (SiNPs), appearing after thermal annealing (λ > 720 nm, τ ∼ μs), and ii) fast-decay PL, possibly due to oxide-related defects (λ ∼ 575-690 nm, τ ∼ ns). The fast-decay PL (ii) observed before and after ion irradiation is induced by ion implantation. It is found that this fast-decay luminescence decreases for higher irradiation fluence of MeV heavy ions. After thermal annealing (forming SiNPs), the SiNP PL is reduced for samples irradiated by MeV heavy ions but found to stabilize at higher level for higher irradiation flux; the (ii) band vanishes as a result of annealing. The results are discussed in terms of the influence of electronic and nuclear stopping powers. (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-10-06T05:20:14.110997-05:
DOI: 10.1002/pssc.201600077

• Influence of irradiation by 60Co gamma-quanta on reliability of IR-LEDs
based upon AlGaAs heterostructures
• Authors: Alexander V. Gradoboev; Anastasiia V. Simonova, Ksenia N. Orlova
Abstract: We consider the influence of preliminary irradiation by 60Co gamma quanta on emission power decrease during the operating time of IR-LEDs based upon AlGaAs double heterostructures. Irradiation was realized in passive power mode of the LEDs prior to aging. Aging under long operating time conditions was simulated by a step-stress approach. We have determined that the emissive power decrease of LED during operating time has two stages. On the first stage, decrease of LED emissive power is due to rearrangement of original defect structure. On the second stage, emissive power goes down as the result of inducing new structural defects. We have shown identical multistage mechanisms of emissive power drop are observed during both operating time and influence of ionizing radiation. We have established that preliminary irradiation has increased reliability and operating time of LEDs. (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-10-06T05:20:12.437854-05:
DOI: 10.1002/pssc.201600035

• Physicochemical effects of amino- or sulfur-functional groups onto SBA-15
sol-gel synthesized mesoporous ceramic material
• Authors: Zulema Vargas-Osorio; Osmar Alejandro Chanes-Cuevas, Adriana Pérez-Soria, Manuel García-Hipolito, Octavio Alvarez-Fregoso, Marco Antonio Alvarez-Perez
Abstract: SBA-15 mesoporous ceramics were synthesized by a sol-gel method with some modifications and functionalized with ethylenediamine or tetrasulfide groups and using a sequential washing approach of organic solvent mixtures. The effects of the functional groups onto the physicochemical properties were characterized using XRD, TG/DTA, FTIR, N2 adsorption–desorption, TEM, SEM and NMR. These analyses showed that the SBA-15 ceramic synthesized at low temperature shows a flat two-dimensional hexagonal symmetry with pore diameters of 7.1 to 7.8 nm. In the meantime, the functionalized ethylenediamine SBA-15 presented a narrow pore-size distribution with diameter around 3.5 to 5.7 nm.A different behavior was observed on the tetrasulfide SBA-15 showing a decrease in unit-cell parameter, in pore size (∼ 2.5 nm) and an increase in pore wall size with loss in structural order and at high sulfur concentrations exhibited an amorphous structure. Results indicated that the lattice crystalline structure value of the SBA-15 increased due to the amino-functionalization process to a value of 13.48 nm respect to a value of 12.72 nm in SBA-15 and decreased to 10.12 nm as an effect of the sulfur-functionalization process, indicative of the effect of the amino and sulfur group into the well-ordered hexagonal mesoporous structure of SBA-15 ceramic materials.
PubDate: 2016-09-30T01:40:28.160316-05:
DOI: 10.1002/pssc.201600099

• Synthesis and characterization of CoxNi1-xFe2O4 samples by solution
combustion method using glycine as fuel
• Authors: P. V. Jithin; P. K. Baghya, N. Roona, Anu Thomas, Nygil Thomas, V. D. Sudheesh, Varkey Sebastain, N. Lakshmi
Abstract: Nano sized CoxNi1-xFe2O4(0≤x≤1) samples were prepared by solution combustion method using glycine as fuel, maintaining a fuel to oxidizer ratio of 0.8. PXRD and FTIR analysis confirms the formation of the spinel phase. Non spherical and highly crystalline nature of the sample was revealed by HRTEM analysis. Lattice parameters of all samples calculated after Rietveld refinement and their variation are in accordance with Vegard's law. DC magnetization study indicates a transformation from soft to hard magnetic phase on increase in Co concentration. Saturation magnetization of nickel ferrite samples match well with that of bulk samples, while the pure cobalt ferrite sample has a lower saturation magnetization compared to that of the bulk, which may be due to spin canting. Impedance measurements of the samples give general trend shown by ferrite material which is in accordance with Koop's phenomenological theory. The study shows that the magnetic and electric properties of nickel ferrite nanoparticles can be easily tailored using a simple solution combustion method in the fuel lean condition with glycine as fuel. (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-09-30T01:40:26.916266-05:
DOI: 10.1002/pssc.201600117

• Paving the way for solution‐ processable perovskite lasers
• Authors: Valerio Sarritzu; Michele Cadelano, Nicola Sestu, Daniela Marongiu, Roberto Piras, Xueqing Chang, Francesco Quochi, Michele Saba, Andrea Mura, Giovanni Bongiovanni
Abstract: Trihalide perovskites have been studied quite extensively as light‐harvesting media in photovoltaic devices and have shown a peculiar blend of optoelectronic properties, particularly remarkable carrier mobilities, diffusion lengths comparable to those of inorganic semiconductors and band gap tuneability. Only limited research effort, though, has been devoted so far to leveraging such properties for light emission, and many related processes remain unclear. Here, we identify organic‐inorganic metal halide perovskites as promising candidates for replacing a variety of raw materials at risk of supply shortage, currently used in manufacturing gain media for commercial lasers. We investigate the dynamics of light emission by transient photoluminescence spectroscopy and on the grounds of our findings we identify the challenges ahead on the way to engineering perovskite‐based lasers. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-09-21T04:10:18.002952-05:
DOI: 10.1002/pssc.201600134

• New phosphors with strongly reduced content of critical raw materials for
lighting applications
• Authors: Daniele Chiriu; Luigi Stagi, Carlo Maria Carbonaro, Pier Carlo Ricci
Abstract: Aluminium silicate crystal is proposed as new promising inert matrix as host of luminescent ions. In particular, we studied the luminescence properties of single doped and multi‐doped Al2SiO5 samples (doping elements: Ce, Tb, Cr, Fe, Zr) to explore their suitability as phosphors in modern lighting systems. The Al2SiO5 host matrix, obtained in nano‐sized crystals belonging to the high temperature phase known as sillimanite, allows to narrow down the presence of rare earth elements exclusively to the dopants, thus providing a promising solution to the critical raw material concern.The crystals doped with Fe, Ce and Zr are mainly excited in the UV range, and they are good candidate as phosphors in compact fluorescent lamp systems. Terbium single doped samples are efficient phosphors in the green region with direct excitation in the deep UV region, but their excitation spectrum can be down‐shifted to near UV range in in co‐doped Ce:Tb samples. Indeed, thanks to the efficient energy transfer from cerium ions, the green emission from Tb ions can be excited by commercial AlGaN light emitting diode, suggesting Ce:Tb doped Al2SiO5 crystals as promising phosphors for green LED system. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-09-21T04:10:17.138089-05:
DOI: 10.1002/pssc.201600115

• Combined thermionic and field emission reverse current for ideal
graphene/n‐Si Schottky contacts in a modified Landauer formalism
• Authors: Argyrios Varonides
Abstract: Fundamental understanding of carrier transport is needed for current graphene‐based devices (e.g. graphene based Schottky diodes, FET geometries, solar cells) involving single layer graphene grown directly over n‐ or p‐ type semiconductors. In an intimate (ideal) G/n‐Si junction under reverse bias, carriers may (a) tunnel through the junction and/or (b) thermionically overcome the junction barrier. Tunneling occurring at the junction is in essence thermionic field emission of carriers with energy levels below the junction barrier, with a less‐than‐one tunneling probability; thermal escape may occur as long as carriers have sufficient energy to overcome the barrier at the interface. The total current is expected to be the sum of two current components, thermionic emission (TE) and thermionic field emission (TFE), respectively, representing carriers surmounting and tunneling through the barrier, in the form I = ITE + ITFE, and is strongly dependent on temperature and doping. Specifically, we derive explicit results for both currents within the general Schottky diode current‐voltage characteristic: I = Io (eqV/kT–1). The combined current prefactor includes strong dependencies on (a) temperature as T3/2 and T5/2 for TE and TFE components, respectively, (b) junction barrier qΦB, (c) graphene layer thickness δ and (d) different Richardson constants for both components. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-09-21T04:10:16.269698-05:
DOI: 10.1002/pssc.201600096

• Technological enhancers effect on Ni0.9Co0.1 silicide stability for 3D
sequential integration
• Authors: Fabien Deprat; Fabrice Nemouchi, Claire Fenouillet‐Beranger, Philippe Rodriguez, Sylvain Joblot, Magali Gregoire, David Barge, Patrice Gergaud, Nils Rambal, Perrine Batude, Maud Vinet
Abstract: 3D sequential integration is a promising alternative to conventional scaling down approach: by stacking transistors level on top of each other, benefits on device density and performance are achieved. However, although the thermal processing of top transistors is currently restricted in order to avoid bottom CMOS degradation, it has been highlighted that Ni0.80Pt0.10 silicide source/drain (S&D) contact remains the most sensitive element to the thermal budget, especially on raised Si0.7Ge0.3:B S&D for pMOS transistors. In this context, a complete and systematic study on self‐aligned silicide (SALICIDE) process has been proposed: alternative metallization as well as source and drain surface pre‐treatments have been carried out. Indeed, a novel Ni‐based silicide, the Ni0.9Co0.1 provides a better stability on unpatterned 300 mm wafers. This stability has been further improved when combined with epitaxial silicon capping layer (Si‐Cap) and Si0.7Ge0.3:B S&D pre‐amorphization implant (PAI) using Ge beam. For the first time, a successful Ni0.9Co0.1 SALICIDE implementation has been demonstrated on pMOS planar FDSOI transistor with both PAI and Si‐Cap. Moreover, the presence of Si‐Cap contributes to reduce silicide roughness and limits Ge partition that damage Si0.7Ge0.3:B S&D. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-09-21T04:10:15.286214-05:
DOI: 10.1002/pssc.201600043

• Effect of nanocrystal geometric location on tunnel currents and
• Authors: Andrzej Mazurak; Jakub Jasiński, Bogdan Majkusiak
Abstract: In this paper, basing on a theoretical model of the ncMIS (nanocrystal metal‐insulator‐semiconductor) structure, in which nanocrystals embedded in the insulator layer are represented by traps of a continuous distribution in the energy gap, we consider the effect of geometric location of nanocrystals in the insulator on the voltage dependences of gate current and small‐signal admittance parameters.
PubDate: 2016-09-15T05:31:55.537576-05:
DOI: 10.1002/pssc.201600206

• New strategies for the synthesis of ZnO and Al‐doped ZnO films by
reactive magnetron sputtering at room temperature
• Authors: David Horwat; Martin Mickan, William Chamorro
Abstract: We review our recent findings that reactive magnetron sputtering can be operated without thermal assistance to produce epitaxial ZnO films and highly conductive and transparent aluminum‐doped ZnO (AZO) films on large surface area. The growth of epitaxial films requires working in direct current (DC) mode at large oxygen partial pressure but high power impulse magnetron sputtering (HiPIMS) is preferred to optimize the electrical and optical properties of AZO films on large surface areas. The results are interpreted by the ability of DC sputtering to easily oxidize the target surface and the HiPIMS mode cleans and returns it to metallic during pulses. Fast oxygen atoms (ions) may be emitted in large amount using DC and bring fuel to the growing ZnO film to induce epitaxy onto sapphire. The signature of oxygen interstitials is found in DC with increasing magnitude as the oxygen content is increased in the gas phase. In contrast, the discharge voltage plays a significant role in HiPIMS to adjust the sputtering rate and clean the target surface for deposition of slightly sub‐stoichiometric AZO films over the entire range of lateral positions. Thereby, transparent yet highly conductive films with resistivity in the range 4‐15×10‐4 Ωcm can be produced. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-09-15T05:31:54.599503-05:
DOI: 10.1002/pssc.201600136

• Valorizing end‐of‐life LCD scraps after indium recovery
• Authors: Maria Letizia Ruello; Alessia Amato, Francesca Beolchini, Saveria Monosi
Abstract: According to the WEEE European directives, efforts must be undertaken to reuse or safely dispose liquid crystal displays (LCD) waste, however no practical process was reported yet, although it is possible to recover glass, plastic and precious metals, in particular indium. Indium is one of the elements included by the European Commission in the list of 20 raw materials critical for economic importance and high supply risk (European Commission, https://ec.europa.eu/ growth/tools‐databases/eip‐raw‐materials/en/system/files/ged/79%20report‐b_en.pdf [1]). The work aims to valorize LCD scraps after indium recovery with low cost applications both economically and environmentally speaking. Applications have been explored by many researchers, although most focused only on the use of glass powder waste LCD to design concrete. This work deals the use of LCD scraps as it is after cross‐current leaching of indium with H2SO4. The experimental work consists of scraps characterization, washing procedure optimization to remove residual acid, mortar production, performance testing, and life cycle assessment (LCA). The results show that LCD scraps exhibit little or no pozzolanic activity. This delay on reactivity can be ascribed to organic residues that prevent the pozzolanic reaction and/or to a lower fineness than that typical of binders or fillers. For this reason the actual investigation focuses to exploit the waste as partial replacement of traditional aggregates. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-09-15T05:31:53.792964-05:
DOI: 10.1002/pssc.201600122

• High‐induction nanocrystalline soft magnetic FeXTiYBZ films prepared
by magnetron sputtering
• Authors: Elena N. Sheftel; Valentin A. Tedzhetov, Eugene V. Harin, Filipp V. Kiryukhantsev‐Korneev, Galina Sh. Usmanova
Abstract: To design films with the Fe/TiB2 nanocomposite structure, which are characterized by high saturation induction Bs, the phase and structural states and static magnetic properties of Fe‐TiB2 films prepared by magnetron sputtering and subjected to subsequent annealing have been studied. According to X‐ray diffraction data, either amorphous or nanocrystalline single‐phase structure (an α‐Fe(Ti,B) supersaturated solid solution with a bcc crystal lattice) is formed in the as‐sputtered films. Depending on the film composition, the grain size of the α‐Fe(Ti,B) phase varies from 45.6 to 6.5 nm; grains are characterized by high microstrain (0.21‐4.96%). The annealing at 200‐500 °C leads to a decrease in the lattice parameter of the α‐Fe(Ti,B) phase, i.e. to its depletion of titanium and boron and to the formation of two‐phase α‐Fe + Fe3B structure after annealing at 500 °C. The annealing at 200‐500 °C almost does not affect the grain size and microstrain of the bcc α‐Fe‐based phase. The amorphous state of the films is stable up to 500 °C. All studied films are ferromagnets; the saturation induction Bs(0.95‐2.13 T) and coercive field Hc (0.4‐5 kA/m) of the films were determined. Correlations between the Bs and Hc magnitudes and the chemical composition of the films, their phase and structural states and magnetic structure are discussed. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-09-15T05:31:52.832508-05:
DOI: 10.1002/pssc.201600107

• Effect of La doping on interface barrier between Si‐passivated Ge
and insulating HfO2
• Authors: Nadiia M. Kolomiiets; Valery V. Afanas'ev, Oreste Madia, Daire J. Cott, Nadine Collaert, Aaron Thean, Andre Stesmans
Abstract: By analyzing internal photoemission of electrons from Si/SiOx‐passivated Ge into insulating HfO2 we found that insertion of additional La interlayer between SiOx and HfO2 leads to dramatic increase (more than by factor of 20) of the barrier transparency. However, no measurable variation of the interface barrier height is observed suggesting that La induces intermixing of near‐interface oxide stack resulting in development of additional density of states corresponding to conduction band of LaOx and HfOx sub‐networks. At the same time, photoemission results indicate the presence of discrete positive charges in the near‐interface oxide layer which may explain the observed ∼1 V shift of capacitance‐voltage curves. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-09-15T05:31:51.998257-05:
DOI: 10.1002/pssc.201600105

• Conicity of latent tracks in the near surface region as a factor affecting
the correct evaluation of track size
• Authors: Maxim Saifulin; Jacques O'Connell, Vladimir Skuratov, Arno Janse van Vuuren
Abstract: The difference in track parameters recorded in some oxides at the same energy loss and different ion velocity, the so called “velocity effect”, have been corroborated by various experimental methods. Most of the corresponding data on damage cross section and then on the track radii were found by means of indirect techniques such as Rutherford backscattering spectroscopy in channelling geometry. The contribution of transmission electron microscopy results in the whole data array remains very limited. In this report we present an analysis of existing TEM results related to the “velocity effect” and consider how the conical shape of latent tracks observed in the subsurface region of swift heavy ion irradiated oxides may affect the correct determination of the track size as well as the critical electronic energy loss for track formation. The discussion is based on our cross sectional TEM studies of high energy Bi and Xe ion induced latent tracks in TiO2 and Al2O3 single crystals. To our knowledge there have been no reported cross sectional TEM analyses on Y3Fe5O12, Bi4Ge3O12 and YBa2Cu3O7‐δ in order to verify the cylindrical track assumption. If similar conicity exists in the near surface regions of these materials it may cast some doubt on the validity of the velocity effect. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-09-15T05:31:51.01038-05:0
DOI: 10.1002/pssc.201600069

• SUPERMAT – A virtual center for sustainable development of advanced
materials operating under extreme conditions
• Authors: Radu R. Piticescu; Santiago Cuesta‐Lopez, Antonio Rinaldi, Marina Urbina, Yi Qin, Peter Szakalos, Alain Largeteau
Abstract: The expertise, main experimental facilities and some selected results of the EU SUPERMAT Consortium are described, showing the importance of integrating modelling and simulation, fast sintering and coating technologies and specific characterisation techniques for obtaining high temperature ceramics, oxide dispersion strengthened (ODS) steels or Li‐ion batteries with controlled properties for extreme environmental applications. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-09-13T05:10:12.680204-05:
DOI: 10.1002/pssc.201600132

• Application of NiOx thin films as p‐type emitter layer in
heterojunction solar cells
• Authors: Francesca Menchini; Maria Luisa Grilli, Theodoros Dikonimos, Alberto Mittiga, Luca Serenelli, Enrico Salza, Rosa Chierchia, Mario Tucci
Abstract: Non‐stoichiometric nickel oxide (NiOx) is attracting growing attention due to its characteristics of p‐type transparent conductive layer and to the possibility to tailor its optical and electrical properties. NiOx could also be employed as the electron blocking layer in silicon‐based heterojunction solar cells. However, at present not much work has been done in this direction. In this paper we investigate the optoelectronic characteristics of NiOx thin films and demonstrate the usability of NiOx as emitter layer in silicon based heterostructure solar cells due to its hole collection selectivity. Test heterojunctions show a rectifying behaviour, even if their characteristics are still limited by the density of defects at the c‐Si/NiOx interface, as deduced by comparing the experimental results with numerical simulations. This suggests that the quality of the interface between NiOx and c‐Si needs to be improved, either by optimizing the deposition process of NiOx or by depositing a buffer layer able to carefully passivate the silicon surface and helpfully allow the growth of oxide layer. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-09-13T05:10:11.755253-05:
DOI: 10.1002/pssc.201600121

• Secondary indium production from end‐of‐life liquid crystal
displays
• Authors: Alessia Amato; Laura Rocchetti, Viviana Fonti, Maria Letizia Ruello, Francesca Beolchini
Abstract: In 2014, the European Union identified 20 raw materials critical for economic importance and high supply risk. Indium, used in several innovative technologies, is among such critical raw materials. Generally, it is mined as a by‐product of zinc from a mineral named sphalerite, with a concentration between 1 and 100 ppm. Currently, the largest producer of indium is China and about 84% of the worldwide indium consumption is used for liquid crystal display (LCD) production, in particular to form an indium‐tin‐oxide (ITO) film with transparent conductor properties. The fast evolution of LCD technologies caused a double effect: the growth of indium demand and an increase of waste electrical and electronic equipment (WEEE). Considering these two factors, the aim of this study is to make the end‐of‐life LCDs a secondary indium resource. With this purpose, an indium recovery process was developed carrying out an acidic leaching, followed by a zinc cementation. The first step allowed a complete indium extraction using 2M sulfuric acid at 80 °C for 10 min. The problem of low indium concentration in the scraps (around 150 ppm) was overcome using a cross‐current configuration in the leaching phase that allowed an increase of metal concentration and a decrease of reagents consumption. An indium recovery higher than 90% was obtained in the final cementation step, using 5 g/L of zinc powder at pH 3 and 55 °C for 10 min. Considering its high efficiency, this process is promising in a context of circular economy, where a waste becomes a resource. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-09-13T05:10:10.820586-05:
DOI: 10.1002/pssc.201600114

• Simulation of the disorder effects in ferroelectric phase transitions
using two‐dimensional statistical models
• Authors: R. Riesco; M. I. Marqués, A. Peláiz‐Barranco, O. García‐Zaldívar, C. Aragó
Abstract: Two‐dimensional Ising models are used to explain the disorder effects in mixed solid solutions and doped relaxor systems. On ferro‐ferro solutions like Pb(Zr1‐xTix)O3 (PZT), the composition dependence of the Curie temperature TC(x) usually deviates from the averaged linear behavior known as the Vegard's law. This deviation is mimicked by a Hamiltonian model including interactions between different types of dipoles in a two dimensional lattice. Doping PZT with lanthanum (PLZT) results in a relaxor behavior that is explained by adding a new term to 2D Ising model that takes into account the interaction between dipoles and itinerant charges. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-09-13T05:10:09.921595-05:
DOI: 10.1002/pssc.201600094

• Effects of hydrogen pressure on hydrogenated amorphous silicon thin films
prepared by low‐temperature reactive pulsed laser deposition
• Authors: A. Mellos; M. Kandyla, D. Palles, M. Kompitsas
Abstract: We deposit intrinsic hydrogenated amorphous silicon (a‐Si:H) thin films by reactive pulsed laser deposition, for various hydrogen pressures in the 0–20 Pa range, at a low deposition temperature of 120 °C, and investigate the hydrogen incorporation, structural, optical, and electrical properties of the films, as a function of the ambient hydrogen pressure. The film thickness decreases linearly as the hydrogen pressure increases. The hydrogen content of the films is determined by infrared spectroscopy and the optical bandgap from UV‐Vis‐NIR transmittance and reflectance measurements. Electric measurements yield the dark conductivity of the films. The hydrogen concentration of the films lies in the 1021–1022cm–3 range and increases with the hydrogen pressure until the latter reaches 15 Pa, beyond which the hydrogen concentration decreases. The optical bandgap and dark conductivity follow the hydrogen concentration variation of the films. The dark conductivity lies in the 10–9–10–10S/cm range. An unusually wide optical bandgap of 2.2–2.6 eV is observed. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-09-13T05:10:08.901927-05:
DOI: 10.1002/pssc.201600088

• Low‐temperature Cu‐induced poly‐crystallization of electrodeposited
germanium thin film on flexible substrate
• Authors: Yasutaka Uchida; Tomoko Funayama, Yoshiaki Kogure, Wenchang Yeh
Abstract: We investigated the low‐temperature Cu‐induced poly‐crystallization (150 °C) of electrodeposited Ge film on a flexible substrate. For a 50 nm‐electrodeposited Ge film on a flexible substrate and annealed for 1 h, a Raman shift peak due to Ge‐Ge bonding at 299 cm‐1 was not observed, but a broad amorphous Ge around 270 cm‐1. However, the Ge‐Ge bond peak was observed after 5 h of annealing. The crystallization speed of Ge on the flexible substrate was slower than on a quartz substrate. The FWHM value of the Raman shift with respect to electrodeposition current had a minimum value of 9.2.cm‐1 at a electrodeposited current of 80 mA. The main XRD observed peaks were Ge(111) at 27° and Ge(102) at 30°. The stress evaluated by Stoney’s equation was about 0.5 GPa. However, the stress increased with the electrodeposition current. The stress before and after annealing of 60 mA was weaker than those in the films at a higher electrodeposition current. We propose that the electrodeposition current dependence is related to the deposition rate.
PubDate: 2016-09-07T00:20:20.808141-05:
DOI: 10.1002/pssc.201600140

• Effect of ultrasonic treatment on the defect structure of the
Si‐SiO2 system
• Authors: D. Kropman; V. Seeman, S. Dolgov, A. Medvids
Abstract: The effect of ultrasonic treatment (UST) on the defect structure of the Si‐SiO2 system by means of electron spin resonance (ESR), metallography, MOS capacitance technique and secondary ions mass‐spectroscopy (SIMS) is presented. The non‐monotonous dependence of the defect densities on the US wave intensity has been observed. The influence of the UST frequency on the ESR signal intensity of the defect centres depended on the defects type and structure and may becaused by vibrational energy dissipation which are a functions of defect's centers type. The influence of the UST on the Si‐SiO2 interface properties depends on the oxide thickness and crystallographic orientation. The density of point defects and absorbed impurities at the Si–SiO2 interface can be reduced and its electrical parameters improved by an appropriate choice of the UST and oxidation conditions. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-09-07T00:20:19.109085-05:
DOI: 10.1002/pssc.201600052

• The effect of holding time on the size distribution of β‐Si3N4
particles and nucleation undercooling in multicrystalline silicon
• Authors: Espen Undheim; Kai Erik Ekstrøm, Lars Arnberg, Randi Holmestad, Marisa Di Sabatino
Abstract: The nucleation mechanism for directional solidification of multicrystalline silicon (mc‐Si) in silicon nitride (Si3N4) coated crucibles has been investigated. A combination of thermal and particle size analysis was used to show that the nucleation undercooling was inversely proportional to the particles size. The particle size was increased by keeping the silicon melted for increasing time periods and the growing particles were identified as β‐Si3N4. The results from the particle analysis were verified by topographical studies using scanning electron microscopy (SEM). These results indicate that β‐Si3N4 particles are the dominant nucleation substrates for mc‐Si in Si3N4 coated crucibles.
PubDate: 2016-09-07T00:20:18.100311-05:
DOI: 10.1002/pssc.201600062

• Effect of intrinsic impurities and annealing conditions on
dislocation‐related luminescence in self‐ion‐implanted Si
• Authors: Dmitry Korolev; Alexey Mikhaylov, Alexey Belov, David Tetelbaum
Abstract: The influence of intrinsic impurities (boron, phosphorus) in the original CZ‐Si on the behavior of the D1 dislocation‐related luminescence line has been investigated in the samples with dislocations introduced by Si+ ion implantation upon the change of annealing ambient. It is established that, for the phosphorus‐doped samples, the D1 line does not occur at the annealing at 1100 °C in inert ambient (N2), but its intensity increases with increasing the oxygen content. For the boron‐doped samples, this line arises in the case of annealing in an inert ambient, herewith the intensity practically does not depend on the composition of the annealing ambient. At the annealing in argon ambient at 900‐1100 °C, the maximal photoluminescence intensity is achieved for annealing at 900 °C. The results are interpreted in terms of interaction between boron and point defects as radiative recombination centers located in dislocations atmospheres. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-09-07T00:20:17.353908-05:
DOI: 10.1002/pssc.201600086

• Effects of Ga deposition rate and Sb flux on morphology of GaSb quantum
dots formed on GaAs
• Authors: Takuya Kawazu; Takeshi Noda, Yoshiki Sakuma, Hiroyuki Sakaki
Abstract: We investigate the effects of Ga deposition rate (RGa) and Sb flux (PSb) on the morphology of GaSb quantum dots (QDs). GaSb QDs are formed on GaAs at 420 °C by Stranski‐Krastanov (SK) mode under various conditions of RGa (0.13‐0.73 monolayer (ML)/s) and PSb (1.0‐4.2 × 10‐7 Torr). An atomic microscope study shows that the density nQD of GaSb QDs is markedly affected by PSb and RGa; no (or few) QDs are formed at high RGa (∼ 0.73 ML/s) and at low PSb (≤1.2 × 10‐7 Torr). As RGa (PSb) increases, nQD first increases and then decreases. nQD reaches its maximum (∼1 × 1011 cm‐2), when the V‐III ratio is about 3.6. We also analyze the experimental data by using a rate equation model and discuss the dependences of nQD on RGa and PSb. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-09-07T00:20:16.548995-05:
DOI: 10.1002/pssc.201600109

• Nanodiamonds and gold nanoparticles: a promising couple for CRM‐free
photonics
• Authors: Giacomo Reina; Silvia Orlanducci, Emanuela Tamburri, Roberto Matassa, Marco Rossi, Maria Letizia Terranova
Abstract: The design and assembling of hybrid nanomaterials formed by the controlled aggregation of nanodiamonds (DND) and gold nanoparticles (AuNP) are presently a focus of the scientific community. The AuNP@DND systems are characterized by very attractive properties and by great potentialities for applications in optics and photonics. We present a review of some interesting AuNP@DND systems produced in our labs using synthetic routes that enable to control the mutual organization and the crystalline features of the two components. The functional tests suggest that the cooperative interaction between gold and nanodiamond produce materials that represents an innovative concept for efficient, stable and biocompatible light‐related applications. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-09-07T00:20:15.698573-05:
DOI: 10.1002/pssc.201600111

• Strength and weakness of rare earths based phosphors: Strategies to
replace critical raw materials
• Authors: Daniele Chiriu; Luigi Stagi, Carlo Maria Carbonaro, Pier Carlo Ricci
Abstract: Rare earth based phosphors are largely the most applied luminescent materials in the present lightening devices. Their ubiquity in lighting system, like light emitting diodes or compact fluorescent lamps, is related to the optical high efficiency of the rare earth as luminescent ions but also to the relative easiness of growth technique as well high structural stability of rare earth based host matrices, like garnets, perovskites and oxyorthosilicatas. On the other hand, the need of new devices virtually free of any elements with high supply disruption, the ones classified by EU community and US government as critical raw materials, boosts the research for alternatives materials. In this paper, we focalize on the optical properties of the REE based phosphors with the intent to underline the performances the new materials should grant, thus addressing the possible direction for new material development. In particular the features related to the possibility of tuning the luminescence, the interaction among doping ions and with surface defects were analysed. Finally, a general model to predict the role of the REE in a host matrix is analysed. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-09-07T00:20:14.504411-05:
DOI: 10.1002/pssc.201600116

• Optical and photoacoustic investigation of AZO/Ag/AZO transparent
conductive coating for solar cells
• Authors: Gianmario Cesarini; Grigore Leahu, M. L. Grilli, A. Sytchkova, Concita Sibilia, Roberto Li Voti
Abstract: Great attention has been recently paid to transparent conductive oxides (TCOs) due to their application in optoelectronic devices, flat panel displays, solar cells, and anti‐static coatings. Concerning photovoltaic applications, the reduction of the material and processing costs are the key factors in the production process. Due to In scarcity and cost, alternative solutions to indium tin oxide (ITO) are needed. Al‐doped ZnO (AZO) meets the requirements for application in thin film solar cells, thanks to its good optoelectrical properties, low cost and higher resistance to Hydrogen‐reach plasmas. Recently many papers analyze innovative AZO based TCO structures where a thin layer of Silver is introduced in the TCO so to increase the electrical conductivity without loosing transparency. In this work we study the transparency and the electrical sheet resistance of a multilayer AZO/Ag/AZO as a function of the silver thin layer, and discuss the problem of optimizing the thicknesses of the multilayers to get the best performances. We have realized an AZO/Ag/AZO multilayer coating by radio frequency (RF) sputtering with an optimal thickness of the silver layer. Optical and photoacoustic spectroscopy (PAS) have been applied to perform the characterization of the sample. In particular PAS seems the most efficient technique to test directly the absorbance of the structure which should be reduced to avoid overheating and loss of the solar cell efficiency.
PubDate: 2016-09-07T00:20:13.507334-05:
DOI: 10.1002/pssc.201600118

• Outcoupling efficiency optimization of phosphorescent and fluorescent
based hybrid red, green and blue emitting OLED devices
• Authors: M. Vasilopoulou; D. G. Georgiadou, D. Davazoglou, S. P. Savaidis, N. A. Stathopoulos
Abstract: The outcoupling efficiency of a hybrid OLED device with a hole‐injection layer formed by either an organic semiconducting material, namely PEDOT:PSS, or an under‐stoichiometric molybdenum oxide is examined. Because the device is considered for the three primary colour emissions, the active layer is composed of a wide band‐gap blue emitting host polymer doped with either phosphorescent or fluorescent guest emitters. Critical parameters, such as the emission zone profile for the doped active layer with either the organic hole‐injection layer or the inorganic metal oxide, are studied. Contour charts have been derived providing the areas of maximum outcoupling efficiency with the corresponding thickness pairs of the active layer and the hole‐injection layer. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-09-07T00:20:12.351624-05:
DOI: 10.1002/pssc.201600123

• Are organic compounds good candidates to substitute rare earth materials
in fluorescent applications?
• Authors: Carlo Maria Carbonaro; Daniele Chiriu, Pier Carlo Ricci
Abstract: The optical properties of some organic compounds in solution or embedded within suitable host matrices are reported and discussed in terms of their performances for possible applications in lighting, photonic or biomedicine. The aim of the paper is to briefly review the presence of rare earth elements in these fields and to enlighten the possibility of their substitution because of global market cost/effectiveness considerations. The easiness of green chemical synthesis and functionalization, the fluorescence tunability over the visible spectrum range of dye molecules and their fluorescence quantum efficiency promote organic compounds as promising good candidate to substitute rare earth materials. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-09-07T00:20:11.229638-05:
DOI: 10.1002/pssc.201600130

• Luminescent point defect formation in 3C‐SiC by ion implantation
• Authors: Abdul Salam Al Atem; Lydie Ferrier, Bruno Canut, Nicolas Chauvin, Gérard Guillot, Jean‐Marie Bluet
Abstract: Optically active point defects in SiC are attracting a growing interest thanks to their prospect of emission in the near‐infrared (NIR) spectral region (application in optical fiber communications and for in vivo imaging) and also thanks to the possibility to control optically their spin. Most of the results have been obtained for the hexagonal SiC polytypes. In this work, we focus on the optical properties of point defects in the 3C‐SiC polytype after ion implantation. Different ions, fluences and post‐implantation annealing were performed to optimize the defect formation. Photoluminescence results show that the optimal conditions for intense D1 defect related PL emission in the 600‐850 nm range are high temperature annealing (up to 1200 °C) and a displacement density not exceeding 1020 cm‐3 at the projected range. The creation of Ky5 defect at 1.12 eV has also been demonstrated for lower temperature annealing (800 °C). (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-09-07T00:20:10.127595-05:
DOI: 10.1002/pssc.201600139

• Effect of thermal annealing on the luminescence of defective ZnO
nanoparticles synthesized by pulsed laser ablation in water
• Authors: P. Camarda; R. Schneider, R. Popescu, L. Vaccaro, F. Messina, G. Buscarino, S. Agnello, F. M. Gelardi, M. Cannas
Abstract: This work concerns ZnO nanoparticles (NPs), with sizes of tens of nm, produced by ablation with a pulsed Nd:YAG laser of a Zn plate in H2O. TEM images evidence the formation of nanoparticles with sizes of tens of nm. Moreover, HRTEM images and Raman spectra show that the distance between the crystalline planes and the vibrational modes are consistent with ZnO nanocrystal in wurtzite structure. Their optical properties are characterized by two emission bands both excited above the energy gap (3.4 eV): the first at 3.3 eV is associated with excitons recombination, the second at 2.2 eV is proposed to originate from a singly ionized oxygen vacancy. The green emission is independent of water pH, thus suggesting that point defects lie inside NPs rather than at the surface. Thermal annealing at 300 °C in O2 and He atmosphere, produces a reduction of the A1(LO) Raman mode at 562 cm‐1, which is related to the oxygen vacancies, and a consequent decrease of the defect luminescence, while the excitonic luminescence increases. These results indicate that the ZnO emissions can be controlled by thermal annealing, and are promising in view of optoelectronic applications.
PubDate: 2016-09-07T00:10:16.557459-05:
DOI: 10.1002/pssc.201600034

• Using MDECR‐PECVD to study the impact of ion bombardment energy on
microstructural properties of μc‐Si:H thin film grown from an SiF4/H2
chemistry
• Authors: Junkang Wang; Ileana Florea, Pavel V. Bulkin, Jean‐Luc Maurice, Erik V. Johnson
Abstract: The matrix‐distributed electron cyclotron resonance plasma‐enhanced chemical vapor deposition (MDECR‐PECVD) technique has been shown to achieve high deposition rates for hydrogenated microcrystalline silicon (μc‐Si:H) thin film. Due to the fact that plasma is sustained by a microwave discharge, by biasing the substrate holder with additional power supply, one can achieve independent control over the plasma density and the maximum ion bombardment energy (IBE). In this work, we present studies of the impact of IBE on the microstructural properties of the μc‐Si:H film deposited by MDECR‐PECVD. Insufficient ion bombardment is found to be responsible for the substantial presence of nano‐porous regions within the material, resulting in significant post‐deposition oxidation. Good agreement between transmission electron microscopy (TEM) Fresnel contrast analysis and the results of infrared absorption and hydrogen effusion measurements for the deposited films suggest that moderate IBE is of vital importance to achieve high quality μc‐Si:H. In doing so, denser films with significantly decreased nano‐porous regions and better stability are obtained, which is of great interest to optimize the process parameters for solar cell applications. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-09-07T00:10:15.736223-05:
DOI: 10.1002/pssc.201600049

• Spatially arranged chains of Ge quantum dots grown on Si substrate
prepatterned by ion‐beam‐assisted nanoimprint lithography
• Authors: Anatoly Dvurechenskii; Zhanna Smagina, Pavel Novikov, Vladimir Zinovyev, Polina Kuchinskaya, Sergey Rudin, Alexey Nenashev
Abstract: Joint experimental and theoretical study of Ge nanoislands growth on groove‐patterned Si(001) substrate prepared by ion‐beam‐assisted nanoimprint lithography is carried out. Prepatterning procedure includes ion irradiation of Si substrate through imprinted resist mask with linear mounds and subsequent multistep oxidation/etching of irradiated Si domains. It is shown that the temperature of subsequent heteroepitaxy on the groovepatterned substrate affects the location of Ge nanoislands. The effect is attributed to additional surface tensile strain formed inside grooves by residual irradiationinduced defects. The interplay of strain and surface curvature makes the critical size of 3D nanoisland larger at the concave regions in grooves than between them. At lower temperatures this results in nanoisland nucleation at the top of mounds. At higher temperatures due to the intensive migration of Ge inside grooves the formation of large nanoislands in grooves occurs. The effect of temperature on the location and size of nanoislands is described by Monte Carlo simulations. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-09-07T00:10:11.139083-05:
DOI: 10.1002/pssc.201600021

• Hybrid perovskite as substituent of indium and gallium in light emitting
diodes
• Authors: Alessandro Lorenzo Palma; Lucio Cinà, Yan Busby, Andrea Marsella, Antonio Agresti, Sara Pescetelli, Jean‐Jacques Pireaux, Aldo Di Carlo
Abstract: Solution‐processed hybrid bromide perovskite light‐emitting‐diodes (PLEDs) represent an attractive alternative to the conventional critical raw materials (CRMs) based green LEDs. In this work, we report the development and characterization of PLEDs fabricated using a mesostructured layout. We adapted and refined deposition techniques typically employed in perovskite based solar cells (PSCs) fabrication to obtain a smooth perovskite layer. The fabricated mesostructured PLEDs measured under full operative conditions showed a remarkably narrow emission spectrum, even lower than what typically obtained by nitride or phosphide green LEDs based on CRMs. An enhancement in mesoscopic PLEDs performance can be achieved optimizing the smoothness of the mesoporous layer and the thickness of the perovskite active material. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-08-19T03:10:06.993756-05:
DOI: 10.1002/pssc.201600101

by fast electrons: a thermally stable vacancy defect
• Authors: Nikolay Arutyunov; Vadim Emtsev, Reinhard Krause‐Rehberg, Mohamed Elsayed, Gagik Oganesyan, Vitalii Kozlovskii
Abstract: Temperature dependency of the average positron lifetime has been investigated for n‐type float‐zone silicon, n‐FZ‐Si(P), subjected to irradiation with 0.9 MeV electrons at RT. In the course of the isochronal annealing a new defect‐related temperature‐dependent pattern of the positron lifetime spectra has been revealed. Beyond the well known intervals of isochronal annealing of acceptor‐like defects such as E‐centers, divacancies and A‐centers, the positron annihilation at the vacancy defects has been observed in the course of the isochronal annealing from ∼ 320 °C up to the limit of reliable detecting of the defect‐related positron annihilation lifetime at ≥ 500 °C. These data correlate with the ones of recovery of the concentration of the charge carriers and their mobility which is found to continue in the course of annealing to ∼ 570 °C; the annealing is accomplished at ∼650 °C. A thermally stable complex consisting of the open vacancy volume and the phosphorus impurity atom, Vop‐P, is suggested as a possible candidate for interpreting the data obtained by the positron annihilation lifetime spectroscopy. An extended couple of semi‐vacancies, 2Vs‐ext, as well as a relaxed inwards a couple of vacancies, 2Vinw, are suggested as the open vacancy volume Vop to be probed with the positron. It is argued that a high thermal stability of the Vs‐ext PVs‐ext (or VinwPVinw.) configuration is contributed by the efficiency of PSi5 bonding. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-08-19T03:10:05.410154-05:
DOI: 10.1002/pssc.201600058

• Enhanced performance of ultraviolet organic light‐emitting diode by
using graphene oxide and MoO3 dual hole injection layer
• Authors: Liming Liu; Fengjiao You, Qinghong Zheng, Bingjie Mo, Baoqing Zeng, Honghang Wang, Xiaowen Zhang, Bin Wei
Abstract: A dual hole injection layer (d‐HIL) composed of graphene oxide (GO) and transition metal oxide MoO3 is constructed and proven to be effectively promotes the radiance and external quantum efficiency (EQE) of ultraviolet organic light‐emitting diode (UV OLED). The device with d‐HIL behaves a maximum radiance of 4.7 mW/cm2 at 237.5 mA/cm2 and EQE of 1.36% at 3.75 mA/cm2, which have been enhanced by 27% and 19%, respectively, in comparison with the coun‐ terpart using conventional MoO3single HIL. The ultraviolet photoelectron spectroscopy elucidates that GO/MoO3 modification to the greatest extent enhances work function. The current‐voltage characteristics and impedance spectroscopy of Hole‐only devices clarify that GO/MoO3 d‐HIL considerably promotes hole injection capacity. Our results indicate that the d‐HIL of GO/MoO3 paves a way for constructing efficient UV OLED. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-08-19T02:40:07.333119-05:
DOI: 10.1002/pssc.201600131

• Tetragonal Ce‐based Ce‐Sm(Fe, Co, Ti)12 alloys for permanent
magnets
• Authors: Andrés Martín‐Cid; Aleksandr M. Gabay, Daniel Salazar, José Manuel Barandiaran, George C. Hadjipanayis
Abstract: Abundance and relatively low cost of Ce provide a great incentive for its use in rare‐earth permanent magnets. It has been recently reported that the tetragonal Ce(Fe,Co,Ti)12 compounds may exhibit application‐worthy intrinsic magnetic properties. In this work the effect of the α‐Fe phase formation due to the evaporation of Sm during alloy fabrication has been studied, as a previous step in the attempt to convert the intrinsic magnetic properties into functional properties of a permanent magnet. Ce0.5Sm0.5Fe9Co2Ti alloys based on the ThMn12‐type crystal structure have been synthesized via melt‐spinning with different Sm content. Coercive fields between 2.8 and 1.4 kOe have been found for α‐Fe phase contents between 8 and 46 % in volume, showing the influence of the α‐Fe phase on the coercivity and exchange coupling between the hard and soft phase. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-08-19T02:40:06.255808-05:
DOI: 10.1002/pssc.201600102

• On the use of a localized STRASS technique to obtain highly tensile
strained Si regions in advanced FDSOI CMOS devices
• Authors: A. Bonnevialle; S. Reboh, C. Le Royer, Y. Morand, J.‐M. Hartmann, D. Rouchon, J.‐M. Pedini, C. Tabone, N. Rambal, A. Payet, C. Plantier, F. Boeuf, M. Haond, A. Claverie, M. Vinet
Abstract: Strain boosters are an effective way to improve performances in advanced CMOS FDSOI devices. Hole mobility is higher in pFETs with compressive channels. Meanwhile, electron mobility is higher for nFETs with tensile channels. We present an alternative technique to blanket sSOI substrates. The efficiency of the “Strained Silicon by Top Recrystallization of Amorphized SiGe on SOI” technique has been previously successfully demonstrated on blanket SOI (+ 1.6 GPa tensile strain achieved). Here we demonstrate a simple and efficient STRASS module integration in an advanced FDSOI route (14 nm design rules) which allows to cointegrate tensile Si for nFETs and unchanged pFETs.After pFETs have been protected (SiN), the STRASS technique has been used in the SOI nFET patterns. This process requires SiGe selective epitaxy, buried amorphization by ion implantation, recrystallization and SiGe removal. Raman spectroscopy is used to characterize the stress in Si areas with respect to process conditions (implantation, active area dimensions). Moreover, the mechanisms of SiGe relaxation will be discussed as function of device dimensions and SiGe layer properties (thickness, Ge content). We demonstrate the successful integration of localized STRASS module: tensile Si patterns (for nFETs) with a level of stress of + 1.6 GPa, cointegrated with unmodified pFETs. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-08-09T05:20:14.763766-05:
DOI: 10.1002/pssc.201600028

• Enhanced dielectric properties of thin Ta2O5 films grown on 65 nm SiO2/Si
• Authors: Vl. Kolkovsky; E. Kurth, C. Kunath
Abstract: The structural and electrical properties of Ta2O5/65 nm SiO2 structures with different thicknesses of Ta2O5 varying in the range of 0‐260 nm are investigated. We find that the stack structures grown by the magnetron sputtering technique and annealed at 1220 K in O and Ar atmosphere show one of the highest dielectric constant of Ta2O5(about 64) among those previously reported in the literature. The structure of the annealed polycrystalline Ta2O5 films is orthorhombic, as obtained from X‐ray diffraction measurements and we do not observe any preferential orientation of the annealed films. The Ta2O5 films contain positively charged defects which become mobile at around 400 K and they are tentatively correlated with the oxygen vacancies. The leakage current in the stack structures is a factor of 20 higher compared to that in thin layers with 65 nm SiO2. The conduction mechanism in the stack structures can be described by the Fowler‐Nordheim model with a barrier height that decreases slightly (
PubDate: 2016-08-09T05:20:13.819851-05:
DOI: 10.1002/pssc.201600050

• Carbon concentration measurement in silicon down to 1014 cm‐3: second
generation IR, SIMS, CPAA and standardization
• Authors: Naohisa Inoue; Takahide Sugiyama, Yasunori Goto, Kaori Watanabe, Hirofumi Seki, Masumi Obuchi, Hiroyuki Uno, Shigeru Shimada, Noriyuki Fujiyama, Yuichi Kawamura
Abstract: Carbon concentration ([C]) measurement in silicon down to 1x1014 cm‐3 was examined by infrared absorption spectroscopy (IR), secondary ion mass spectroscopy (SIMS) and charged particle activation analysis (CPAA). In IR, reference problem and phonon problem were solved. By electron irradiation, carbon substitutional Cs was converted to IR insensitive interstitial Ci. Reference with [C] about 1x1014 cm‐3 which was accurately estimated was produced. Dip and protrusion around carbon absorption line in [C] 1014 cm‐3 range were identified to be inflexion points of the phonon absorption band, and the way to cancel them was established. These techniques were transferred to most silicon crystal vendors, IR machine vendors and measurement service companies in the world. SIMS and CPAA measurement was done on the samples measured by IR. The cross calibration was done at [C] = 5x1014 cm‐3 and is continued down to 1x1014cm‐3. Electron irradiation to completely remove carbon substitutional provides the ideal reference containing effectively no carbon, new technique to measure the absolute carbon content, and standard sample for calibration. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-08-09T05:20:12.923752-05:
DOI: 10.1002/pssc.201600068

• Ab initio calculations of PbTiO3/SrTiO3 (001) heterostructures
• Authors: R. I. Eglitis; S. Piskunov, Yu. F. Zhukovskii
Abstract: We performed ab initio calculations for the PbTiO3/SrTiO3 (001) heterostructures. For both PbO and TiO2‐terminations of the PbTiO3 (001) thin film, augmented on the SrTiO3 (001) substrate, the magnitudes of atomic relaxations Δz increases as a function of the number of augmented monolayers. For both terminations of the augmented PbTiO3 (001) nanothin film, all upper, third and fifth monolayers are displaced inwards (Δz is negative), whereas all second, fourth and sixth monolayers are displaced outwards (Δz is positive). The B3PW calculated PbTiO3/SrTiO3 (001) heterostructure band gaps, independently from the number of augmented layers, are always smaller than the PbTiO3 and SrTiO3 bulk band gaps. For both PbO and TiO2‐terminated PbTiO3/SrTiO3(001) heterostructures, their band gaps are reduced due to the increased number of PbTiO3 (001) monolayers. The band gaps of PbO‐terminated augmented PbTiO3 (001) films are always larger than those for TiO2‐terminated PbTiO3 (001) thin films. The only exception is the case of 7‐layer PbO‐terminated and 8‐layer TiO2‐terminated augmented PbTiO3 (001) thin films, where their band gaps both are equal to 2.99 eV. For each monolayer of the SrTiO3 (001) substrate, charge magnitudes always are more than several times larger, than for each monolayer in the augmented PbTiO3 (001) thin film. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-08-09T05:20:11.955837-05:
DOI: 10.1002/pssc.201600074

• Stability of Y‐Ti‐O nanoparticles in ODS alloys during heat treatment
and high temperature swift heavy ion irradiation
• Authors: V. A. Skuratov; A. S. Sohatsky, J. H. O'Connell, K. Kornieieva, A. A. Nikitina, J. H. Neethling, V. S. Ageev, M. Zdorovets, A. D. Volkov
Abstract: Aim of this report is to compare the morphology of swift (167 and 220 MeV) Xe ion induced latent tracks in Y2Ti2O7 nanoparticles during post‐irradiation heat treatment and after irradiation at different temperatures in pre‐thinned TEM foils and TEM targets prepared from hundreds microns thick irradiated oxide dispersion strengthened (ODS) steel. No difference in track parameters was found in room temperature irradiated nanoparticles in pre‐thinned and conventional samples. Microstructural data gathered from pre‐thinned foils irradiated in the temperature range 350‐650 °C or annealed at similar temperatures demonstrate that amorphous latent tracks interact with the surrounding matrix, changing the track and nanoparticle morphology, while such effect is not observed in conventional ODS material treated at the same conditions. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-08-09T05:20:11.139434-05:
DOI: 10.1002/pssc.201600080

• Charged oxygen interstitials in corundum: first principles simulations
• Authors: Alexander Platonenko; Denis Gryaznov, Sergei Piskunov, Yuri F. Zhukovskii, Eugene A. Kotomin
Abstract: Combining supercell models and hybrid B3PW exchange‐correlation functionals, ab initio simulations on quasi‐stable configurations of interstitial $O_i^-$ ions in α‐Al2O3 (corundum) crystals and possible migration trajectories have been modelled. We have studied crystalline distortion around migrating $O_i^-$ including interatomic distances and the effective atomic charges, as well as redistributions of the electronic density. Unlike neutral interstitial atom Oi studied by us previously, migrating $O_i^-$ ion does not form dumbbells with the nearest regular $O_{reg}^{q -}$ oxygen ions, due to the strong Coulomb interaction with the nearest $Al_{reg}^{q+}$ cations as well as stronger repulsion between $O_i^-$ and adjacent regular $O_{reg}^{q -}$ ions. We have also estimated the energy barrier for migration between the nearest quasistable configurations of interstitial $O_i^-$ ion. One of these configurations is an octahedron formed by six nearest $O_{reg}^{q -}$ anions in the centre of which $O_i^-$ ion is located, unlike a neutral Oi atom which prefers to migrate directly towards one of adjacent $O_{reg}^{q -}$ anions with the dumbbell formation. As the result, the barrier for $O_i^-$ ion migration in corundum has been found to be by ∼70% smaller than that of Oi atom. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-08-09T05:20:10.277323-05:
DOI: 10.1002/pssc.201600081

• Issue Information: Phys. Status Solidi C 7–9/2016
• PubDate: 2016-07-26T05:23:35.72582-05:0
DOI: 10.1002/pssc.201670129

• Cover Picture: Phys. Status Solidi C 7–9/2016
• Abstract: In this work, polycrystalline n‐doped ZnO layers and n‐doped ZnO nanowires are coated with the p‐doped organic polymers polypyrrole and PEDOT by using oxidative chemical vapor deposition (oCVD). The goal of S. Bley and coworkers (pp. 614–617) is to form hybrid hetero‐junctions for developing efficient and low‐cost optoelectronic devices for applications such as LEDs and solar cells, and to show that oCVD is a versatile technique for the fabrication of inorganic/organic core–shell structures. The structural, electrical, and optical properties of polymer‐coated ZnO structures have been investigated by SEM, TSEM, EDX, electrical, and PL measurements. SEM and electrical measurements on the polypyrrole‐coated ZnO layers show that a de‐creasing amount of the used oxidizing agent (FeCl3) from 0.3 g to 0.1 g leads to thin and homogeneous coating which increases the quality of the formed pn‐heterojunction. Structural and optical investigations of the coated ZnO nanowires show that a thin and conformal polymer coating of the nanowires is achieved by using 0.1 g FeCl3 without affecting the general optical properties of ZnO. Cl doping of the polymer shell is confirmed by EDX measurements.
PubDate: 2016-07-26T05:23:30.557459-05:
DOI: 10.1002/pssc.201670128

• High performance InGaZnO‐based Schottky diodes fabricated at room
temperature
• Authors: Linlong Yan; Qian Xin, Lulu Du, Jiawei Zhang, Yi Luo, Qingpu Wang, Aimin Song
Abstract: Recently, Indium gallium zinc oxide (InGaZnO or IGZO) has attracted much attention for flexible and transparent electronics, because of its superior electric properties, optical transparency and low processing temperature. In this work, Schottky diodes with a structure of Pd/IGZO/Ti/Au were fabricated by radio‐frequency magnetron sputtering at room temperature without any thermal treatment. The optimised diode with a 66‐nm‐IGZO layer shows an extremely large barrier height (1.02 eV), a very high rectification ratio (> 8.5 × 107), and a close to unit ideality factor (1.23). Our results suggest that Pd and IGZO can form very high quality Schottky contact with a large barrier height, extremely low defects density and high uniformity. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-06-03T03:10:07.432455-05:
DOI: 10.1002/pssc.201510291

• HgCdTe p+‐n structures grown by MBE on Si (013) substrates for high
operating temperature SWIR detectors
• Authors: V. M. Bazovkin; S. A. Dvoretskiy, A. A. Guzev, A. P. Kovchavtsev, D. V. Marin, Z. V. Panova, I. V. Sabinina, Yu. G. Sidorov, G. Yu. Sidorov, A. V. Tsarenko, V. S. Varavin, V. V. Vasiliev, M. V. Yakushev
Abstract: Electrophysical properties of multilayered heteroepitaxial structures of Hg1‐xCdxTe with x=0.3‐0.4 grown by molecular beam epitaxy on silicon substrates are presented. The passivating effect of thin CdTe layers grown on top of the structures in single process is demonstrated. Comparison between experimental and theoretical temperature dependencies of reverse currents in n‐on‐p and p‐on‐n diodes fabricated by boron and arsenic ion implantation in vacancy‐doped p‐type and In‐doped n‐type Hg1‐xCdxTe films, respectively, are presented. The influence of p‐n junction position in double‐layer heterostructure on temperature dependencies of reverse currents is examined. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-05-13T06:30:15.827321-05:
DOI: 10.1002/pssc.201510259

• ZnSe:Mn aqueous colloidal quantum dots for optical and biomedical
applications
• Authors: Thiago G. Silva; Igor M. R. Moura, Paulo E. Cabral Filho, Maria I. A. Pereira, Clayton A. Azevedo Filho, Goreti Pereira, Giovannia A. L. Pereira, Adriana Fontes, Beate S. Santos
Abstract: In this study, we present the optimization of the optical properties of Mn2+ doped ZnSe QDs (also referred to as d‐dots) coated with thioglycolic acid in aqueous medium. The nanoparticles were characterized by ionic coupled plasma, electron paramagnetic resonance, transmission electron microscopy and X‐ray diffractometry. By applying a controlled dose of UV irradiation, we obtained efficient orange emitting d‐dots (4T1→ 6A1 transition centered at 580 nm). The results point out to a doping fraction in the nanoparticles smaller than 1% (0.89%), and that the Mn2+ ions are preferentially located close to the particle's surface. The UV photoactivation procedure has a definite influence on the emission intensity and on the colloidal stability of the particles. Photoactivated Mn2+ d‐dots were conjugated to Concanavalin A and labeled specifically Candida albicans yeast cells, by targeting carbohydrate residues depicting the successful use of these QDs as fluorescent probes. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-05-13T06:30:14.725451-05:
DOI: 10.1002/pssc.201510300

• Towards multifunctional heterostructured materials: ZnO nanowires growth
on mesoscale periodically patterned Si
• Authors: Anisha Gokarna; Agnieszka Gwiazda, Hind Kadiri, Anna Rumyantseva, Komla Nomenyo, Roy Aad, Gilles Lerondel
Abstract: We report the growth of ZnO nanowires on mesoscale periodically patterned silicon. The aim of this work is to go towards fabrication of multifunctional heterostructured materials for increasing the specific surface area and light absorption properties. ZnO nanowires (NWs) were grown by chemical bath deposition technique on patterned silicon. Silicon patterning was conducted by two methods, namely, laser interference lithography and nanosphere lithography. We have studied the structural and optical properties of the ZnO NWs grown on these silicon patterns. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-05-03T03:40:48.47202-05:0
DOI: 10.1002/pssc.201510295

• Structural, electronic and thermodynamic properties of SrxCa1‐xS: A
first‐principles study
• Authors: S. Labidi; M. Boudjendlia, M. Labidi, J. Zeroual, R. Bensalem, F. El Haj Hassan
Abstract: The principal purpose of this work is to further the understanding of the structural, electronic, and thermodynamic properties of the SrxCa1–xS alloys (0≤x ≤1) in Rock‐salt phase using the full potential augmented plane wave (FP‐LAPW) method within density functional theory. The exchange‐correlation potential for structural properties was calculated by the standard local density approximation (LDA) and GGA (PBE) and the new form of GGA (WC) which is an improved form of the most popular Perdew‐Burke‐Ernzerhof (PBE), while for electronic properties, the alternative form of GGA modified by Becke‐Johnson exchange correlation potential (MBJ) was also applied. It is shown that investigation on the effect of composition on lattice constant, bulk modulus, and band gap for ternary alloys shows almost nonlinear dependence on the composition. On the other hand, the thermodynamic stability of these alloys was investigated by calculating the excess enthalpy of mixing ΔHm as well as the phase diagram. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-05-03T03:40:47.247638-05:
DOI: 10.1002/pssc.201510247

• Effect of electron blocking layers on the conduction and valence band
profiles of InGaN/GaN LEDs
• Authors: Simon Hammersley; Phil Dawson, Menno J. Kappers, Fabien C.‐P. Massabuau, Martin Frentrup, Rachel A. Oliver, Colin J. Humphreys
Abstract: In this paper we investigate the effect of including an electron blocking layer between the quantum well active region and the p‐type layers of a light emitting diode has on the conduction and valence band profile of a light emitting diode. Two light emitting diode structures with nominally identical quantum well active regions one containing an electron blocking layer and one without were grown for the purposes of this investigation. The conduction and valence band profiles for both structures were then calculated using a commercially available Schrödinger‐Poisson calculator, and a modification to the electric field across the QWs observed. The results of these calculations were then compared to photoluminescence and photoluminescence time decay measurements. The modification in electric field across the quantum wells of the structures resulted in slower radiative recombination in the sample containing an electron blocking layers. The sample containing an electron blocking layer was also found to exhibit a lower internal quantum efficiency, which we attribute to the observed slower radiative recombination lifetime making radiative recombination less competitive. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-05-02T06:10:04.718911-05:
DOI: 10.1002/pssc.201510288

Al2O3 insulator
• Authors: Alexander V. Voitsekhovskii; Sergey N. Nesmelov, Stanislav M. Dzyadukh, Vladimir V. Vasil`ev, Vasiliy S. Varavin, Sergey A. Dvoretsky, Nikolay N. Mikhailov, Maxim V. Yakushev, Georgiy Y. Sidorov
Abstract: The paper presents the results of studies of the admittance of MIS structures based on heteroepitaxial MBE n (p)‐Hg0.78Cd0.22Te with insulator coating SiO2/Si3N4 and Al2O3 in the test signal frequency range 10 kHz‐1 MHz at temperatures ranging from 8 to 220 K. The main parameters of MIS structures with different insulators were determined. MIS structures with Al2O3 have a large enough insulator capacitance (compared to SiO2/Si3N4), a significant modulation capacitance on the CV characteristics, high dielectric strength and low values of the flat‐band voltage. The effective charge density found from the value of the flat‐band voltage and slow interface trap density for structures with Al2O3 comparable with the corresponding densities for structures with SiO2/Si3N4. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-04-14T04:12:17.329356-05:
DOI: 10.1002/pssc.201510227

• Electrical and optical studies of a tellurium‐related defect in
molecular‐beam epitaxy‐grown HgCdTe
• Authors: Z. Świątek; M. V. Yakushev, I. I. Izhnin, P. Ozga, K. D. Mynbaev, V. S. Varavin, D. V. Marin, N. N. Mikhailov, S. A. Dvoretsky, A. V. Voitsekhovski, H. V. Savytskyy, O. Yu. Bonchyk
Abstract: Electrical and optical studies of defects in molecular beam epitaxy (MBE)‐grown HgCdTe films, undoped and doped with arsenic, were carried out. By comparing results of ion milling‐assisted Hall‐effect measurements with micro‐Raman spectroscopy data, it was shown that the films contained electrically neutral defects related to excessive tellurium. It is suggested that these defects are Te nanocomplexes and that they are typical of the MBE HgCdTe technology. Under ion milling, they get electrically activated by interstitial mercury and form donor centers with concentration of ∼1017 cm‐3, which allows for detecting them with measurements of electrical parameters of the material. Also, it can be suggested that in films doped with arsenic with high‐temperature cracking, As2 dimers in the arsenic flux react with excessive tellurium and form As2Te3 donor complexes, thus preventing formation of Te nanocomplexes. Arsenic activation annealing may break As2Te3 complexes and release Te, which can again form the complexes under ion milling. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-04-14T04:12:16.310419-05:
DOI: 10.1002/pssc.201510234

• Photosensitive MIS structures with ultrathin dielectric based on
CdXHg1‐XTe (x ∼ 0.4)
• Authors: Valeriy G. Kesler; Alexander A. Guzev, Sergey A. Dvoretskiy, Evgeniy R. Zakirov, Anatoliy P. Kovchavtsev, Zoya V. Panova, Maxim V. Yakushev
Abstract: The work is aimed to studying a possibility of CdHgTe surface passivation and stabilization by tunnel‐thin (∼ 2 nm) native oxide formed by glow discharge plasma oxidation. Kinetics of MCT plasma treatment in two regimes has been obtained. Investigation of the stabilization effect during vacuum annealing and platinum deposition has been performed. It has been established that presence of a native oxide layer on MCT surface results in elimination of mercury out diffusion during the processes. MIS structures with platinum contacts and thin native oxide have been made. They have rectifying behaviour in contrast with structures without the native oxide layer. The barrier height and the detectivity have been determined from the capacitance‐voltage and current‐voltage dependences. The detectivity value of 4×1011cm.Hz1/2W‐1 (at 78 K) determined by dark current shot noise has been reached. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-04-14T04:12:15.186306-05:
DOI: 10.1002/pssc.201510275

• Growth of zinc sulfide by mist chemical vapor deposition depending on mist
size and thermal conditions in susceptor
• Authors: Kazuyuki Uno; Yuichiro Yamasaki, Ping Gu, Ichiro Tanaka
Abstract: Zinc sulfide (ZnS) films were successfully grown by using mist chemical vapor deposition (mist‐CVD) with fine‐channel susceptor made of quartz. For the investigation of growth dynamics, two types of mist generators and two types of susceptors were prepared and distribu¬tion profiles of film thickness were examined.Thermal efficiency of susceptor depends on heat¬penetration efficiency and line‐velocity of the mists, which are influenced by the fine‐channel gap‐height of the susceptors. Using larger size of mists requires higher thermal efficiency in susceptor to obtain a flat thickness distribution. This result indicates that the optimization of the mist size and the susceptor structure is important for the film uniformity of grown films by the mist‐CVD. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-04-14T04:12:13.791215-05:
DOI: 10.1002/pssc.201510309

• Fabrication and characterization of Au/Zn composite electrode on
p‐CdZnTe (111) B plane
• Authors: Xiao‐yan Liang; Jia‐hua Min, Liu‐qing Yang, Ji‐jun Zhang, Lin‐jun Wang, Yue Zhao
Abstract: Electrode fabrication is a key procedure for preparation of high‐performance CdZnTe detectors, and the metal–semiconductor contact contributes greatly to the performance of detectors. In the present paper, a vacuum evaporation method was used to deposit a Au/Zn composite electrode on the (111) plane of p‐CdZnTe. Based on the AFM, SEM, current–voltage testing and the barrier‐height calculations, the effects of an Au/Zn contact on CdZnTe detector properties were investigated. The results showed that a lower Schottky barrier height was attained by depositing a Au layer on p‐CdZnTe(111) A plane and a Au/Zn double layers on (111) B plane, decreasing the influence of the Te‐enriched surface on the metal–semiconductor contact, and suggesting a better ohmic contact for CdZnTe detectors. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-03-29T03:34:04.771146-05:
DOI: 10.1002/pssc.201510279

• Electronic spectrum of Bi‐related defects in crystalline CdTe
• Authors: Vladimir Krivobok; Sergey Nikolaev, Evgeny Onischenko, Anna Pruchkina, Sergey Kolosov, Yuri Klevkov, Victor Bagaev
Abstract: Using measurements of conductivity and low‐temperature photoluminescence, we have studied electronic levels in the band gap of CdTe:Bi and CdTe:Bi,Cl single crystals grown by the modified Bridgman technique. Three type of deep levels (EV+0.29 eV, EV+0.4 eV, EV+0.72 eV) and Bi‐related shallow acceptor have been observed depending on the doping conditions. Energy spectrum of a shallow Bi‐related acceptor has been measured and its low symmetry has been established. The tentative interpretation for all the levels observed has been proposed. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-03-16T06:20:15.499157-05:
DOI: 10.1002/pssc.201510274

• Growth and characterization of Mg1‐xCdxO thin films
• Authors: Lluís‐Manel Guia; Vincent Sallet, Corinne Sartel, M. Carmen Martínez‐Tomás, Vicente Muñoz‐Sanjosé
Abstract: In this paper, we study the growth of thin films of the Mg1–xCdxO alloy in the Mg‐rich range of compositions by using the metal organic chemical vapour deposition (MOCVD) method at low pressure. X‐ray diffraction (XRD) has been used to analyse the compound formation and the progressive incorporation of Cd2+ ions into the cubic MgO lattice. Both, layers with a single‐cubic phase of Mg1–xCdxO and layers with a phase separation, where Cd1–xMgxO and Mg1–xCdxO coexist, have been studied. Finally, a morphological study of the layers has been carried out by using scanning electron microscopy (SEM) and the layers' composition has been measured by energy dispersive X‐ray analysis (EDX). (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-03-16T06:20:14.563297-05:
DOI: 10.1002/pssc.201510276

• Structural, optical and magnetic characteristics of II‐VI semiconductor
nanocrystal‐graphene hybrid nanostructures
• Authors: Andriy I. Savchuk; Ihor D. Stolyarchuk, Serhii A. Savchuk, Eugeniusz M. Sheregij, Jacek Polit
Abstract: CdS, CdTe, ZnO, and ZnO:Co nanocrystals and related hybrid nanostructures, in which the nanoparticles combined with graphene, have been studied. Different chemical approaches for synthesis of II‐VI semiconductor nanocrystal‐graphene hybrids have been applied depending on chemical composition. Transmission electron microscopy characterizations proved the formation of graphene based hybrid nanostructures. Absorption spectra near band‐gap edge have shown changes due to the interaction of the nanocrystals with graphene. The revealed photoluminescence quenching effect in II‐VI semiconductor nanocrystal‐graphene hybrids can be served as evidence for electron transfer from the nanoparticles to graphene. Results of Faraday rotation measurements in doped ZnO:Co nanocrystals and their hybrids at room temperature demonstrated paramagnetic behaviour for both kinds of samples. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-03-16T06:20:13.065783-05:
DOI: 10.1002/pssc.201510283

• Structural properties and vertical transport in ZnSe/CdSe superlattices
grown on an In0.3Ga0.7As metamorphic buffer layer
• Authors: E. A. Evropeytsev; S. V. Sorokin, G. V. Klimko, S. V. Gronin, I. V. Sedova, K. G. Belyaev, S. V. Ivanov, G. Pozina, A. A. Toropov
Abstract: We report on the growth by molecular‐beam epitaxy of short‐period ZnSe/CdSe superlattices (SLs) on an In0.3Ga0.7As metamorphic buffer layer. Such SLs are considered as a promising material for a wide band‐gap photoactive p‐n junction in a hybrid monolithic Ge/InxGa1‐xAs/Iny(Al,Ga)1‐yAs/II‐VI solar cell. Lattice‐matching of the SLs to the In0.3Ga0.7As layer is confirmed by X‐ray diffractometry. Vertical transport of photoexcited carriers is investigated by means of both steady state and time‐resolved photoluminescence techniques in heterostructures containing the ZnSe/CdSe SL with an enlarged quantum well (EQW). Characteristic times of the carrier transport across the SL towards EQW are evaluated in the temperature range 120–300 K. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-03-16T06:20:11.814723-05:
DOI: 10.1002/pssc.201510305

• Influence of source transport rate upon fractions of Mg and Se in
Zn1‐xMgxSeyTe1–y layers grown by metalorganic vapor phase epitaxy
• Authors: Katsuhiko Saito; Masakatsu Abiru, Eiichiro Mori, Yasuhiro Araki, Daichi Tanaka, Tooru Tanaka, Qixin Guo, Mitsuhiro Nishio
Abstract: The growth of undoped Zn1–xMgx Sey Te1–y layers on (100) ZnTe substrates by metalorganic vapor phase epitaxy has been carried out. The fractions of Mg and Se, Raman property and surface roughness have been characterized as a function of bis‐methylcyclopentadienyl‐magnesium ((MeCp)2Mg) or diethylselenide (DESe) transport rates. It has been demonstrated that the Mg and Se fractions in Zn1–xMgx Sey Te1–y layer can be controlled successfully by these source transport rates. Furthermore, the behaviors of two Raman peaks related to ZnSeTe‐like longitudinal optical phonon mode and MgSeTe‐like one have been clarified for some Mg and Se fractions in Zn1–xMgx Sey Te1–y layers. It has been shown by varying (MeCp)2Mg or DESe transport rates that Zn1‐xMgx Sey Te1–y layer nearly‐lattice‐matched to ZnTe substrate shows low surface roughness. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-03-16T06:20:10.744695-05:
DOI: 10.1002/pssc.201510304

• A comparative study of the gas sensing properties of hierarchical ZnO
nanostructures
• Authors: Martine Capochichi‐Gnambodoe; Yamina Ghozlane Habba, Yamin Leprince‐Wang
Abstract: Two types of ZnO nanostructure have been fabricated to make a comparative study on their gas sensing performance: the conventional ZnO nanowire arrays were synthesized by hydrothermal method and the hierarchical ZnO nanowires/nanofibers nanostructures were prepared through a combination of the hydrothermal and electrospinning methods. Field emission scanning electron microscopy study showed a quiet homogeneous morphology both for both nanostructures. Three kinds of commonly used gases, such as ethanol, acetone and ammonia were chosen for ZnO nanostructure gas sensing property study. The UV‐Visible spectroscopy measurements showed a higher detection sensitivity of ZnO NWs for ammonia compared to ethanol and acetone, and an enhanced sensing performance for the hierarchical nano‐ structure, which has a higher surface to volume ratio. On the other hand, the enhancement was more obviously in the case of ethanol sensing. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-03-16T06:20:09.844942-05:
DOI: 10.1002/pssc.201510301

• 2D‐localization and delocalization effects in quantum Hall regime in
HgTe wide quantum wells
• Authors: Svetlana V. Gudina; Yurii G. Arapov, Vladimir N. Neverov, Sergey M. Podgornykh, Mikhail R. Popov, Nina G. Shelushinina, Mikhail V. Yakunin, Sergey A. Dvoretsky, Nikolay N. Mikhailov
Abstract: We have measured the longitudinal and Hall resistivities in the quantum Hall regime at magnetic fields B up to 9 T and temperatures T = (2.9–50) K for HgTe/HgCdTe heterostructure with wide HgTe quantum well. The results are analysed within the scaling concept for the conductivity on the delocalized states at the center of the Landau level and within the variable‐range hopping model for the conductivity on the localized states between the Landau levels. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-03-16T06:20:08.88983-05:0
DOI: 10.1002/pssc.201510299

• Tamm plasmon polaritons in the visible spectral region and its optical
properties in ZnSe‐based microcavities
• Authors: S. K. Shaid‐Ur Rahman; Kathrin Sebald, Jürgen Gutowski, Thorsten Klein, Sebastian Klembt, Carsten Kruse, Detlef Hommel
Abstract: We report on the formation of Tamm plasmon (TP) modes in the visible spectral region at the interface between a Ag film and a ZnSe‐based distributed Bragg reflector (DBR). The tuning of the TP eigenenergies within the stop‐band in dependence on the DBR top layer thickness is investigated by micro‐reflectivity measurements. The experimental findings are compared with calculations using the transfer matrix method. The latter calculations show that strong coupling can be achieved between quantum well (QW) excitons and the TP modes. In addition, the Rabi‐splitting energy can be enhanced in a simple TP structure by increasing the number of QWs inside the top layer of the DBR.When a metal layer is deposited on a cold MC sample, micro‐reflectivity spectra show a blue shift of the cavity resonance. The TP modes are likewise observed in the same MC sample when reducing the top layer thickness of the DBR. This shift of cavity resonance and formation of TP mode are in good agreement with calculations. These results are rather promising in order to realize a spatial confinement of the polaritons by utilizing metal strips. Such channeling of polaritons opens the way to practical demonstration of exciton‐polariton integrated circuits. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-03-16T06:20:08.001662-05:
DOI: 10.1002/pssc.201510296

• Effect of Al doping in the Ag layer of MgZnO/Ag/MgZnO
dielectric/metal/dielectric UV–visible transparent conductive films
• Authors: Yukiko Sugimoto; Kanae Igarashi, Shinya Shirasaki, Akihiko Kikuchi
Abstract: Transparent conductive films (TCFs) with dielectric/metal/dielectric (DMD) structure covering the UVA (λ = 315–380 nm) and visible wavelength region (380–780 nm) were fabricated using Al‐doped Mg0.4Zn0.6O (AMZO) dielectric and 1.7 at% Al‐doped Ag (Ag(Al)) metal layers. The AMZO/Ag(Al)/AMZO‐DMD film with a 7 nm thick Ag(Al) layer after annealing in vacuum at 400 °C showed superior performance as a TCF, i.e., average transmittance from UVA to visible region (315–780 nm) of 88.2% and sheet resistance of 7.6 Ω/sq. The effect of Al doping on optical transmission, sheet resistance, surface morphology, and thermal durability of the AMZO/Ag(Al)/AMZO‐DMD films were also investigated. The 1.7 at% Al doping suppressed the initial island growth of the thin Ag layer and the plasmon resonance absorption dipped in the optical transmission spectra. Al doping in the Ag layer also improved the thermal durability of AMZO/Ag/AMZO‐DMD films. The threshold temperature for Ag void formation caused by metal segregation increased from 300 °C (DMD with a pure Ag layer) to 400 °C (DMD with an Al‐doped Ag layer). (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-03-16T06:20:07.072077-05:
DOI: 10.1002/pssc.201510290

• Influence of the number of electronically coupled CdSe/ZnSe QD planes on
characteristics of optically pumped green lasers
• Authors: I. V. Sedova; E. V. Lutsenko, S. V. Sorokin, A. G. Vainilovich, S. V. Gronin, G. P. Yablonskii, M. Aljoheni, A. Aljerwi, A. Alyamani, S. V. Ivanov
Abstract: Structural properties and laser characteristics of true green (λ=530‐550 nm) ZnSe‐based optically pumped laser heterostructures with several (up to three) CdSe/ZnSe quantum dot (QD) planes in the active region were studied in details. Optimization of the MBE growth conditions to reduce the non‐equilibrium defect density in the active region as well as the active region design allowed obtaining nearly the same rather low laser threshold values of Ithr∼4 kW/cm2 at Lcav∼100 μm for all the samples. The internal laser parameters were determined by measuring the laser threshold and differential quantum efficiency as functions of the cavity length. The design of laser structures provides high excitation homogeneity of the active region due to strong enough carrier tunneling between QD layers spaced by 5‐nm‐thick ZnSe barriers, which is confirmed by the sub‐linear dependence of the transparency excitation intensity versus number of QD planes in the active region (IT = 0.556, 1.037, and 1.311 kW/cm2). The triple‐QD‐plane laser structure demonstrates significant increase in characteristic gain up to ΓG0=161.62 cm‐1. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-03-16T06:20:05.605287-05:
DOI: 10.1002/pssc.201510289

• Numerical modeling and simulation of ZnO nanowire devices for energy
harvesting
• Authors: Linda Serairi; Dapeng Yu, Yamin Leprince‐Wang
Abstract: Duo to their multifunctional properties, the piezoelectric ZnO nanowires are of great interest in many applications such as the energy harvesting. In this work, a numerical modelling based on the finite element method was performed to study the potential distribution inside the ZnO nanowire and the impact of the geometric parameters on the generated piezopotential both in bending and compression deformation. In this context, a nanowire discharge behavioural study was carried out in order to obtain an analytic expression which connects the piezopotential and nanowire geometrical parameters in the bending deformation. Furthermore, a heuristic algorithm Particle Swarm Optimization (PSO) has been used in order to improve the electromechanical performance of ZnO nanowire based nanogenerator. It is fount that under the same order of force applied on a nanowire, the compression mode results in a piezopotential 9 times larger than that in the bending deformation. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-03-16T06:10:17.801655-05:
DOI: 10.1002/pssc.201510270

• Electron–phonon interaction in II‐VI quantum wells
• Authors: A. Yu. Maslov; O. V. Proshina
Abstract: The theory of charge‐particle interaction with polar optical phonons is developed for II‐VI compounds‐based heterostructures in which the symmetries of the quantum well and barrier materials are different. The parameters of the electron–phonon interaction are found for the structures in which the material of hexagonal symmetry is used for creating a quantum well or barriers. It is shown that the electron–phonon interaction depends on the anisotropy of the dielectric parameters of the hexagonal material for both cases. Compared to previously obtained results for a quantum well based on the material of cubic symmetry both enhancing and weakening of polaron effects are possible. The obtained results are applied to the explanation of polaron mass magnitude in the quantum well based on ZnO‐ZnMgO. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-03-16T06:10:16.973941-05:
DOI: 10.1002/pssc.201510263

• Investigation of yellow/green II‐VI compound semiconductor laser diode
structures on InP substrates
• Authors: Ryohei Kobayashi; Shingo Takamatsu, Koji Fukushima, Katsumi Kishino, Ichirou Nomura
Abstract: II‐VI‐compound‐semiconductor laser diode (LD) structures on InP substrates were investigated using device simulations and waveguide analysis. Our simulations showed that electron injection from the n‐cladding into the active layer is hindered by the n‐side barrier layer between the n‐cladding and active layer. Consequently, holes are not injected into the active layer but instead leak to the n‐side layers. It was shown that carrier injection efficiency can be improved by removing the n‐barrier. On the contrary, no large differences were observed between the optical confinement factors of the LD structures with and without the n‐barrier layer. In experiments, we have fabricated the LD structures with and without the n‐barrier layer on InP substrates using molecular beam epitaxy. The turn‐on voltage of the device without the n‐barrier was smaller than that for the device with the n‐barrier by about 5 V. Spontaneous orange emissions around 603 nm were observed for the devices without the n‐barrier. In contrast, no emission was observed for the devices with the n‐barrier. These results prove that the carrier injection into the active layer is enhanced by the removal of the n‐barrier, leading to improved the device performances. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-03-16T06:10:16.108611-05:
DOI: 10.1002/pssc.201510255

• Effects of strontium concentration on structural, electronic, optical and
thermodynamic properties of Pb1‐xSrxS
• Authors: Jazia Zeroual; Salima Labidi, Malika Labidi, Rachid Bensalem
Abstract: Theoretical investigations of structural, electronic, optical and thermodynamic properties of Pb1‐xSrxS with rocksalt crystal structure are reported, theoretical calculations are mainly based on the full potential linearized augmented plane wave (FP‐LAPW) method within the density functional theory (DFT) the generalized gradient approximation (GGA) of Perdew et al. The dependence of the lattice parameters, band gaps, dielectric constants, refractive indices, and mixing entropies on the composition x were analyzed mainly for x = 0, 0.25, 0.50, 0.75 and 1. The lattice constant for Pb1‐xSrxS exhibits a marginal deviation from the Vegard’s law. A significant deviation of the bulk modulus from linear concentration dependence was observed for the alloy. The microscopic origins of the gap bowing were detailed and explained. The composition dependence of the dielectric constant and refractive index was studied using different models. Besides, a regular‐solution model is used to investigate the thermodynamic stability of the alloys, which mainly indicates a phase miscibility gap. In fact and since there is a good agreement between our main results and the available experimental data for the binary compounds which may be a support for the results of the ternary alloys reported here for the first time. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-03-16T06:10:14.867908-05:
DOI: 10.1002/pssc.201510237

• Comparative studies of CdSe/ZnSe quantum dot structures epitaxially grown
with or without a sub‐monolayer CdTe stressor
• Authors: M. V. Rakhlin; K. G. Belyaev, I. V. Sedova, S. V. Sorokin, S. V. Gronin, A. A. Usikova, A. A. Sitnikova, P. N. Brunkov, S. V. Ivanov, A. A. Toropov
Abstract: We report on comparative studies of the emission properties of CdSe/ZnSe quantum dots (QDs) grown by molecular beam epitaxy either with or without predeposition of a sub‐monolayer CdTe stressor, and in the latter case, either with or without in‐situ thermal annealing. The emission of a limited number of QDs was registered in all samples by micro‐photoluminescence confocal spectroscopy through 500‐nm‐size round apertures opened in a non‐transparent gold mask by ball assisted etching technique. The measurements reveal the lowest density of emitting QDs in the sample grown with the in‐situ annealing that is attributed to both ripening of the CdSe QDs and strain relaxation in the largest QDs, followed by formation of defects serving as centres of nonradiative recombination. The employment of the CdTe stressor causes narrowing of the total QDs emission band and simultaneous broadening of the single‐QD lines that is consistent with the formation of a relatively homogeneous dense array of type‐I CdSe/ZnSe QDs adjoining type‐II Zn(Cd)Te/ZnSe nanostructures. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-03-03T09:15:19.330217-05:
DOI: 10.1002/pssc.201510302

• Growth, structural and optical properties of ZnO/ZnMgO core‐shell
heterostructures
• Authors: S. A. Said Hassani; C. Sartel, C. Vilar, G. Amiri, A. Lusson, V. Sallet, P. Galtier
Abstract: ZnO nanowires have been grown by metalorganic chemical vapor deposition on sapphire substrates. The use of N2O and DEZn as oxygen and zinc precursors combined with high temperature leads to the spontaneous growth of vertical ZnO nanowires (NWs) on underlying three dimensional islands present at the bottom of each nanowire. These nanowires are grown along the c axis of the wurtzite structure, exhibit well defined m‐plane facets and are free of extended defects. This configuration is favorable to band‐gap engineering studies. Based on this, we have grown a series of radial ZnO/ZnMgO shells and quantum wells with different thicknesses and Mg concentrations. ZnxMg1‐xO alloys have been grown using O2, (MCp)2Mg and DEZn as oxygen, magnesium and zinc precursors. Low temperature photoluminescence spectroscopy and transmission electron microscopy have assessed Mg concentrations in the shell up to 20 %. Electron diffraction reveals that the ZnMgO alloyed structure is, at least partially, ordered. Micro‐photoluminescence performed on a single ZnO/ZnMgO coreshell nanowire including a quantum well exhibits luminescence properties, with a lateral quantum confined emission. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-03-03T09:15:16.824029-05:
DOI: 10.1002/pssc.201600001

• Electric field inhomogeneity in ohmic‐type CdTe detectors measured by
time‐of‐flight technique
• Authors: Kazuhiko Suzuki; Takayuki Sawada, Satoru Seto
Abstract: The bias‐induced instability of the internal electric field in Ohmic‐type CdTe gamma‐ray detectors is investigated by using the time‐of‐flight technique. Based on the solution of one dimensional Poisson equation, transient current waveforms at different delays of laser excitation from the bias application and at different temperatures are analysed It is shown that under DC bias application, the internal electric field decreases with depth because of the positive space charge buildup in the detectors. Further, the origin of the space charge is attributed to the injection and successive trapping of holes from the anode side at the early stage of evolution and then later to the thermal release of electrons from a deep donor at 0.64 eV. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-03-03T09:15:14.993931-05:
DOI: 10.1002/pssc.201510239

• Manifestation of strong d‐p hybridization in photoluminescence
spectra of ZnO:Ni and ZnO:Co
• Authors: V. I. Sokolov; N. B. Gruzdev, V. A. Pustovarov, V. N. Churmanov
Abstract: For the first time photoluminescence and photoluminescence excitation spectra for ZnO:Co and ZnO:Ni crystals were obtained at the excitation by the synchrotron radiation in the interval of energy of (3.7‐21) eV, T = 8 K. It is shown that these spectra are formed by intense radiative transitions through 3d charge transfer states in the band gap. This fact evidences about much stronger hybridization between d‐states of impurity and p‐states of anions in comparison with other II‐VI:3d compounds. It is very important for applications in optoelectronics, for visualization of ultraviolet radiation and understanding of photocatalytic activity of ZnO:3d nanocrystals in the visible region of the spectrum. From the comparison of PLE spectra for ZnO:Co and ZnO:Ni with the spectrum of calculated DOS for ZnO it is revealed a visible transformation of part of valence band states due to a strong d‐p hybridization. Obtained results allow us to consider ZnO:3d as a compounds with a strong correlations. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-03-03T09:15:08.729506-05:
DOI: 10.1002/pssc.201510241

• Dislocations in MCT heteroepitaxial structures on (013) substrates and
possibilities of dislocation density reducing
• Authors: Yury Sidorov; Ivan Loshkarev, Irina Sabinina, Evgeny Trukhanov, Vasily Varavin, Maksim Yakushev, Aleksei Kolesnikov
Abstract: Dislocations in heterostructures CdTe/ZnTe/GaAs(013) and CdTe/ZnTe/Si(013) were investigated using selective etching and transmission electron microscopy. The calculations of critical film thickness hc were fulfilled for 12 various slip systems, the experimental results were obtained for 4 of them. Misfit dislocations are introduced in a ZnTe film at the stage of formation of the first monolayers. With their introduction, the crystal lattices of the substrate and the film unfold relative each other that is confirmed by X‐ray diffraction measurements. An increase in the dislocation density into the CdTe and HgCdTe films was observed using layer‐by‐layer etching. That is testifies to the annihilation of threading dislocations during the growth of CdTe and MCT films. The dislocation annihilation rate is higher in films grown on GaAs(013) than on Si(013). Perhaps this is due to the higher proportion of gliding dislocations in CdTe films on GaAs substrates (013). It was made annealing of MCT films under cyclic temperature change in such way that activity of MCT components was changed to enhance the non‐conservative motion of dislocations. As a result, the density of penetrating dislocations in the active areas in MCT films on silicon substrates was decreased to the value of 2.5×106 cm‐2. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-03-03T09:15:05.639755-05:
DOI: 10.1002/pssc.201510243

• Development of ZnSe‐based organic–inorganic hybrid
UV‐APDs array
• Authors: Tomoki Abe; Ryoichi Inoue, Takeru Fujimoto, Kenta Tanaka, Shigeto Uchida, Hirofumi Kasada, Koshi Ando, Kunio Ichino
Abstract: Recently, we have developed organic (PEDOT:PSS)–inorganic (ZnSSe) hybrid avalanche photodiode (APD) with long life time and its array. In this article, we review the development of the organic–inorganic hybrid‐type ZnSe‐based UV‐APDs array. We used PEDOT:PSS as UV transparent hole‐transport conducting polymer window layers formed by inkjet printing technique. We have successfully fabricated low dark current ultraviolet hybrid APDs. The hybrid APD device has exhibited very low voltage APD operation at 29 V and extremely low dark current of 10‐11 A/mm2 in the avalanche breakdownregion. The hybrid APD also has shown maximum multiplication factor of 45 and high sensitivity ∼ 3 A/W at the ultraviolet region (∼ 300 nm). A stable device operation is established using polyimide passivation and sealed package with N2 atmosphere. We also demonstrated integrated devices operation in APD mode with very small photosignal cross‐talk of ‐50 dB. The tail of current‐profile was determined as 8 μm by using in‐plane electron‐beam induced current (EBIC) measurement. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-03-03T09:15:02.679457-05:
DOI: 10.1002/pssc.201510273

• The local electron interaction with crystal defects in wurtzite CdS
• Authors: Orest Malyk; Volodymyr Rodych, Hryhoriy Il'Chuk
Abstract: In the present paper the interaction of electrons with different types of defects with the potential of the limited action radius – polar and nonpolar optical phonons, piezoelectric and acoustic phonons, static strain centers, ionized and neutral impurities – in cadmium sulfide is considered. The dopant concentration in observed CdS crystals was in the limits of 5.5×1015 ÷ 1.1×1019 cm‐3. The dependences of the electron mobility and Hall factor on temperature in the interval 10 ÷ 400 K are investigated. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-03-03T09:14:59.069149-05:
DOI: 10.1002/pssc.201510281

• Peculiarities of CdS nanocrystal formation at annealing of a
Langmuir‐ Blodgett matrix
• Authors: Kirill Svit; Dmitry Protasov, Sergey Teys, Larisa Sveshnikova, Yakushev Maksim, Konstantin Zhuravlev
Abstract: Formation and assembling of CdS nanocrystals (NC) on highly‐ordered pyrolytic graphite (HOPG) and on oxidized silicon substrates have been investigated by atomic force microscopy (AFM) and scanning tunneling microscopy (STM). NC were initially formed within a Langmuir‐Blodgett (LB) matrix of cadmium behenate. The LB matrix was then removed by annealing in an ammonia atmosphere. It is shown that the NC self‐assembling is mainly determined by the LB matrix wetting properties. In case of wettable HOPG substrate homogeneous matrix evaporation occurs that leads to coarsening of the NC arrays as the main self‐assembly process. Otherwise, NC prepared on non‐wettable SiO2‐Si substrate demonstrate arrays formation determined by the LB matrix dewetting process. For the both cases, the influence of kinetic limitations connected with matrix evaporation rate on the self‐assembly process is observed. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-03-03T09:14:57.51281-05:0
DOI: 10.1002/pssc.201510285

• Observation of topological phase transition by terahertz photoconductivity
in HgTe‐based transistors
• Authors: A. M. Kadykov; C. Consejo, M. Marcinkiewicz, L. Viti, M. S. Vitiello, S. S. Krishtopenko, S. Ruffenach, S. V. Morozov, W. Desrat, N. Dyakonova, W. Knap, V. I. Gavrilenko, N. N. Mikhailov, S. A. Dvoretsky, F. Teppe
Abstract: We have found the possibility to probe the magnetic field‐driven topological phase transition in HgTe‐based transistors by measuring their Terahertz photoconductivity response. At the critical magnetic field to which zero‐mode Landau levels cross, we have observed a pronounced photoconductivity peak independent on incident frequency and carrier concentration. Our results pave the way towards terahertz topological field effect transistors. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-02-25T03:13:04.847987-05:
DOI: 10.1002/pssc.201510264

• Low pressure MOVPE growth and characterization of ZnTe homoepitaxial
layers
• Authors: Mitsuhiro Nishio; Katsuhiko Saito, Masakatsu Abiru, Eiichiro Mori, Yasuhiro Araki, Daichi Tanaka, Tooru Tanaka, Qixin Guo
Abstract: The growth rate and photoluminescence (PL) spectrum of ZnTe homoepitaxial layer grown at a reactor pressure of 500 Torr by metalorganic vapor phase epitaxy have been clarified as a function of substrate temperature. An optimum substrate temperature for obtaining ZnTe layers with better PL property is determined by taking into account the growth rate behavior. Furthermore, the growth rate, PL spectrum, surface roughness and surface morphology of ZnTe layer have also been investigated by varying reactor pressure. With increasing reactor pressure, both the PL property and surface roughness of ZnTe layer are improved and subsequently become degraded, according as the growth rate increases monotonically and then shows saturated tendency. Change in the surface morphology of ZnTe layer with the increase of reactor pressure resembles that with the decrease of substrate temperature, probably due to the change from mass‐transport regime to surface kinetics one. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-02-25T03:13:00.722975-05:
DOI: 10.1002/pssc.201510240

• Luminescence dynamics of hybrid ZnO nanowire/CdSe quantum dot structures
• Authors: Stephanie Bley; Friederike Albrecht, Sebastian Resch, Siegfried R. Waldvogel, Andreas Menzel, Margit Zacharias, Tobias Voss, Jürgen Gutowski
Abstract: Colloidal CdSe quantum dots (QDs) functionalized with different organic linker molecules are attached to ZnO nanowires (NWs) to investigate the electron transfer dynamics between dots and wires. After linking the quantum dots to the nanowires, the photo‐induced electron transfer (PET) from the QDs into the NWs becomes visible in the PL transients by a decrease of dot luminescence decay time. The different recombination paths inside the QDs and the PET process are discussed in the framework of a rate equation model. Photoconductivity studies confirm the electron transfer by demonstrating a strong enhancement of the wire photocurrent under light irradiation into the dot transition. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-02-25T03:12:59.796045-05:
DOI: 10.1002/pssc.201510253

• Photoconductive properties of undoped and nitrogen‐doped ZnO single
crystals in various ambiences
• Authors: Takami Abe; Shuzo Takahashi, Shuhei Kamada, Akira Nakagawa, Tetsuya Chiba, Michiko Nakagawa, Shigeki Chiba, Yasuhiro Kashiwaba, Masahiro Daibo, Ikuo Niikura, Yasube Kashiwaba, Hiroshi Osada
Abstract: The effects of ambiences on photoconductive properties of the Zn‐face of undoped ZnO and nitrogen‐doped ZnO (ZnO:N) single crystals are described. Oxygen (O2) gas affected the photocurrent spectra of the Zn‐face of both single crystals. The photocurrent was smallest in O2 gas and was largest in the vacuum ambience. The influence of ambience was very small in the visible light region but was large in the UV region. Regardless of the ambience, photocurrent of the Zn‐face of ZnO:N showed no sensitivity in the visible region. The decay time response of undoped ZnO and ZnO:N single crystals was also affected by the ambience. Decay time responses of both single crystals were fastest in O2 gas and were slowest in the vacuum ambience. The decay time response of the ZnO:N single crystal was faster than that of the undoped ZnO single crystal. These results showed that the effect of oxygen‐mediated surface recombination is strong in both large single crystals with very small surface‐to‐volume ratio and no grain boundary effect. The results also showed that doped nitrogen decreases the density of electron and hole traps near the surface region of the crystals. It is thought that steepness of band bending near the surface of a ZnO:N single crystal is smaller than that of an undoped ZnO single crystal. In conclusion, the Zn‐face of a ZnO:N single crystal sealed with O2 gas is useful as a photoconductive type UV sensor. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-02-25T03:12:58.907655-05:
DOI: 10.1002/pssc.201510260

• Unintentional nitrogen incorporation in ZnO nanowires detected by electron
paramagnetic resonance spectroscopy
• Authors: J. E. Stehr; W. M. Chen, N. K. Reddy, C. W. Tu, I. A. Buyanova
Abstract: Unintentional incorporation of nitrogen in ZnO nanowires (NWs) grown by rapid thermal chemical vapor deposition is unambiguously proven by electron paramagnetic resonance spectroscopy. The nitrogen dopants are suggested to be provided from contaminations in the source gases. The majority of incorporated nitrogen atoms are concluded to reside at oxygen sites, i.e. in the atomic configuration of nitrogen substituting for oxygen (NO). The NO centers are suggested to be located in proximity to the NW surface, based on their reduced optical ionization energy as compared with that in a bulk material. This implies that the defect formation energy at the NW surface could be lower than its bulk value, consistent with previous theoretical predictions. The obtained results underline that nitrogen can be easily incorporated in ZnO nanostructures which may be of advantage for realizing p‐type conducting ZnO via N doping. On the other hand, the awareness of this process can help to prevent such unintentional doping in structures with desired n‐type conductivity. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-02-25T03:12:58.007038-05:
DOI: 10.1002/pssc.201510261

• Characterization of carrier concentration in ZnO nanowires by scanning
capacitance microscopy
• Authors: Lin Wang; Sophie Guillemin, Jean‐Michel Chauveau, Vincent Sallet, Francois Jomard, Roger Brenier, Vincent Consonni, Georges Brémond
Abstract: Scanning capacitance microscopy (SCM) has been investigated on Ga doped ZnO staircase multi‐layers grown by molecular beam epitaxy (MBE) and ZnO NWs grown by chemical bath deposition (CBD). It is found that SCM data amplitude experiences a monotonic decrease with increasing Ga concentration from 2×1017 cm‐3 to 3×1020 cm‐3, indicating SCM being an appropriate technique for two dimensional dopant/carrier profiling in ZnO at nanoscale. For ZnO nanowires (NWs), a planariz‐ation process was developed based on dip‐coating of silica sol‐gel and chemical‐mechanical polishing. Then ZnO NWs were well detected from the silica matrix by SCM and the residual carrier concentration inside them was estimated through calibration method to be between 5×1017 cm‐3 and 2×1018 cm‐3. Finally, the result was compared with that obtained from conventional capacitance‐voltage (C‐V) measrement and their difference was discussed. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-02-17T04:10:06.765556-05:
DOI: 10.1002/pssc.201510268

• Role of electron‐phonon interaction in the temperature dependence of the
phonon mode frequency in II‐VI compound alloys
• Authors: Jacek Polit; Mariusz Woźny, Józef Cebulski, Claudio Marcelli, Massimo Piccinini, Eugeniusz M. Sheregii
Abstract: We present an experimental investigation of the temperature dependence of the TO‐phonon mode frequencies for the HgTe‐based II‐VI semiconductor solid solutions. In the case of the ternary Hg0.9Zn0.1Te solid solution was shown a discontinuity in the temperature dependence of the HgTe‐like TO‐mode and of the ZnTe‐like TO‐mode, similar to the Hg0.885Cd0.115Te system [Sheregii et al., Phys. Rev. Lett. 102, 045504 (2009)]. A generalization of the theoretical temperature shift of the phonon mode frequency as analytic equation is derived that includes both the anharmonic contribution and the electron‐phonon e‐p interaction which in this case is returnable the electron subsystem effect on the phonon one. Data show that our equation satisfactorily describes the temperature shift of both Hg0.885Cd0.115Te and Hg0.9Zn0.1Te containing Dirac point (Eg = Γ6–ΓΓ8 = 0) although one of the two constants describing the anharmonic shift of the HgTe‐like mode should be positive what is abnormal too. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-02-17T04:10:05.464365-05:
DOI: 10.1002/pssc.201510236

• Improvement of thermal stability of p‐type ZnO:(Al,N) fabricated by
oxidizing Zn3N2:Al thin films
• Authors: Y. F. Wang; D. Y. Song, L. Li, B. S. Li, A. Shen, Y. Sui
Abstract: The authors report the fabrication of p‐type ZnO thin films with improved thermal stability. The p‐type ZnO thin films were obtained by oxidizing Zn3N2:Al thin films in an oxygen ambient. Both Zn3N2:Al and Zn3N2 thin films were deposited on fused silica substrates at 100 °C by megnetron sputtering. X‐ray diffraction (XRD) measurements showed that the ZnO thin films obtained from by oxiding Zn3N2:Al, have preferred (002) orientation. On the other hand, ZnO films obtained by oxidizing Zn3N2 are polycrystalline. The optical band gap of ZnO (3.294 eV) obtained by annealing Zn3N2:Al thin films is narrower than that of the ZnO (3.31 eV) obtained by annealing Zn3N2. P‐type ZnO films were formed by annealing Zn3N2:Al at temperatures above 600 °C. A maximum hole density of 1.4 x 1016 cm‐3 was obtained in a film annealed at 800 °C. In contrast, only n‐type ZnO can be produced from oxidizing Zn3N2. Our results indicate that the Al can stabilize the nitrogen acceptors in ZnO thin films. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-02-09T02:40:20.636144-05:
DOI: 10.1002/pssc.201510164

• RT ZnSe‐based lasers and laser arrays pumped by low‐energy
electron beam
• Authors: M. M. Zverev; S. V. Sorokin, N. A. Gamov, E. V. Zhdanova, V. B. Studionov, I. V. Sedova, S. V. Gronin, S. V. Ivanov
Abstract: The properties of an electron‐beam‐pumped ZnSe‐based laser array consisting of 6 one‐dimensional arrays, each comprising 10 single laser elements, have been studied. The peak output power up to 80‐100 W at room temperature in “true” green (λ = 547 nm) spectral range has been demonstrated by using for pumping electrons with the accelerating energy as low as 5.6 keV. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-02-09T02:40:19.821422-05:
DOI: 10.1002/pssc.201510251

• Evidence of exchange interaction of localized carriers and transition
metals in diluted II‐VI nanostructures: ODMR study
• Authors: P. G. Baranov; N. G. Romanov, D. O. Tolmachev, A. S. Gurin, B. R. Namozov, Yu. G. Kusrayev, G. Karczewski, S. Orlinskii, C. De Mello Donega, J. Schmidt
Abstract: Optically detected magnetic resonance study of (CdMn)Te/(CdMg)Te quantum wells allowed to reveal the formation of exchange‐coupled complexes consisting of Mn ions and localized holes in quantum wells with excess hole concentration and the directional electron tunneling towards wider wells in multiple quantum well structures. The existence of a distribution of Mn‐hole complexes that differ in a number of Mn ions interacting with a localized hole is justified.In colloidal cobalt doped ZnO nanocrystals, several nm in diameter, the interaction between the magnetic ions and the shallow donor electron in the confined system of ZnO quantum dots has been revealed. Direct evidence of interaction of Co ions with the interstitial Li shallow donor in the ZnO nanocrystal core and hyperfine coupling with 1H in the quantum dot shell have been demonstrated. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-02-09T02:40:18.924974-05:
DOI: 10.1002/pssc.201510249

• p‐d charge transfer excitons in Zn1‐xNixO under inner shell
excitation
• Authors: V. N. Churmanov; V. I. Sokolov, N. B. Gruzdev, V. Yu. Ivanov, V. A. Pustovarov
Abstract: The paper presents results of the study of two narrow luminescence lines I1 and I2 at the energies of 3.339 and 3.393 eV respectively in solid state solutions Zn1‐xNixO. The luminescence spectroscopy with a sub‐nanosecond time resolution upon selective photoexcitation in the energy range of the inner shell Zn M‐edge absorption was used to promote the earlier proposed mechanism of the I1 and I2 lines origin. Photoluminescence spectra of solid state solutions Zn1‐xNixO at fast and slow time windows under soft X‐ray excitation are discussed. The doublet of I1 and I2 lines is believed to arise due to the radiative annihilation of p‐d excitons. Different possible mechanisms of emergence of two narrow luminescence lines I1 and I2 in solid state solutions Zn1‐xNixO are considered. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-02-09T02:40:18.016128-05:
DOI: 10.1002/pssc.201510245

• Neutronographic characterization of II‐VI cubic crystals highly doped by
3d ions: on possible tendencies to structure rearrangements in the
sphalerite crystal lattice
• Authors: Tatiana Surkova; Veniamin Maksimov, Sergey Dubinin, Santos Adan Lopez‐Rivera
Abstract: Fine features of the crystal structure of Zn0.9Ni0.1S, Zn0.9V0.1Se, Zn0.95Fe0.05Se semiconductor cubic single crystals have been characterized by neutron scattering at room temperature. It has been revealed that neutron‐diffraction scans of the single crystals, in addition to intense Bragg reflections of face‐centered cubic phase, contain a complex system of diffuse scattering maxima, included superstructure reflections. The superstructure diffuse maxima are found placed on reciprocal lattice knots corresponding with the wave vectors q = (1/3 1/3 1/3) 2π/ac (ac is the cubic lattice parameter), which is interpreted as a manifestation of pretransition state. It is proposed that the revealed destabilized structure state means pretransition of reconstructive structure transformation from the cubic phase to the hexagonal phase. Strong perturbations caused by 3d ions doping lead to a collective response of the cubic lattice of the II‐VI matrices, displacing atomic planes in shears, and tend to induce the transformation. Such a complicated structure state determines nonuniform deformation field supporting possibilities to form long‐wave superstructures. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-02-09T02:40:17.228333-05:
DOI: 10.1002/pssc.201510231

• Contents: Phys. Status Solidi C 7–9/2016
• Pages: 399 - 405
PubDate: 2016-07-26T05:23:36.982605-05:
DOI: 10.1002/pssc.201670130

• II‐IV Compounds and Related Materials
• Authors: Christophe Testelin; Pierre Galtier, Vincent Sallet
Pages: 406 - 407
Abstract: The 17th International Conference on II–VI Compounds and Related Materials was held at the Campus des Cordeliers, in the historical center of Paris, France, from September 13th to 18th.II–VI 2015 has followed the path of a suc‐cessful series of biennial conferences which started in Durham (UK) in 1983. Recent conferences were or‐ganized in Niagara Falls (USA, 2003), Warsaw (Po‐land, 2005), Jeju (Korea, 2007), Saint Petersburg (Russia, 2009), Mayan (Mexico, 2011), and Na‐gahama (Japan, 2013).The II–VI conference aims at providing an international forum for scientists, students and indus‐try representatives, facilitating the exchange of new ideas and establishing fructuous scientific contacts. The ambition is to report the newest developments in basic and applied research on II–VI and re‐lated compounds such as oxides and chalcopyrite semiconductors. The topics cover also novel synthe‐sis techniques, new physical properties and innova‐tive device development. Let us note that for this last edition, the scope has been extended to Related Mate‐rials like photovoltaic materials and novel 2D sys‐tems (dichalcogenides and topological insulators).Gathering 240 participants, II–VI Paris 2015 has fulfilled its mission, with a scientific pro‐gram presenting three plenary review lectures, 15 in‐vited talks, 64 contributed talks and about 200 con‐tributed poster presentations. A special session has been devoted to the memory of Prof. Fritz Henneber‐ger from Humboldt University, Berlin.Following the conference, this issue of physica status solidi offers a variety of basic and applied studies on optical, electrical and mag‐netic properties of II–VI compounds, related materials and devices. Achievements in practical ap‐plications of II–VI compounds will be found in infrared, visible and UV range detectors, optoelec‐tronic devices, photovoltaics. The proceedings edition also emphasizes new trends and pioneering directions, towards original related materials and devices. A total of 78 articles are published in pss  (b) (11), pss RRL (1) and pss  (c) (66). We wish that all participants would appreciate to redis‐cover and thoroughly read some of the nice results presented in Paris.We thank all contributors and reviewers who made the edition of II–VI Paris Proceedings a great success and hope the conference as well as the unique atmosphere of Paris will remain in your heart and memory!
PubDate: 2016-07-26T05:23:32.386499-05:
DOI: 10.1002/pssc.201670131

• Traveling heater method growth and characterization of CdMnTe crystals for
• Authors: Wenqi Wu; Jijun Zhang, Linjun Wang, Jiahua Min, Xiaoyan Liang, Xuliang Wen
Pages: 408 - 412
Abstract: In this paper, the Cd0.9Mn0.1Te (CdMnTe) crystals were grown by the self‐designed Traveling Heater Method (THM) crystal growth system. Two types of polycrystalline CdMnTe feed ingots synthesized in a traditional rocking furnace and in a vertical Bridgman furnace were adopted during the THM growth, and the as‐grown crystals were denominated as CMT1 and CMT2, respectively. The crystal and detector properties, including the Te inclusions, Mn composition, PL spectrum, electrical and energy response properties were characterized. The results showed that the CMT2 ingot had less Te inclusion and more uniform Mn composition distribution along the ingot than CMT1 ingot. During the THM growth, the polycrystalline feed material synthesized by VB technique favoured a smooth and low concave growth interface, which decreased the formation of Te inclusions and Mn variation in the ingot. The resistivity of the CdMnTe crystal grown by THM was in the range of (0.5‐4)×1010 Ω·cm. The PL spectra indicated that CMT2 crystal possesses higher crystalline quality as compared to CMT1 crystal, with lower impurity concentration and defects. The fabrication CdMnTe single element planar detectors under the 59.5 keV 241Am radiation showed that the energy resolution of CMT1 and CMT2 crystals was 17.2% and 12.7%, respectively. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-02-03T06:40:20.053808-05:
DOI: 10.1002/pssc.201510226

• Crystallographic and optical characterizations of Ag(Ga,Al)Te2 layers
grown on c ‐plane sapphire substrates by closed space sublimation
• Authors: Aya Uruno; Yuji Takeda, Tomohiro Inoue, Masakazu Kobayashi
Pages: 413 - 416
Abstract: Ag(Ga,Al)Te2 layers were grown by the closed space sublimation method on c ‐plane sapphire substrates. The source used was AgAlTe2/AgGaTe2 mixture or AgAlTe2/Ga2Te3 mixture. The crystallographic property of Ag(Ga,Al)Te2 layers was analyzed by X‐ray diffraction (XRD). XRD spectra of layers exhibited very strong 112 diffraction peaks regardless of the variation of the source material mixture. In addition to crystallographic characterizations, optical properties of the Ag(Ga,Al)Te2 layer were evaluated through transmittance measurements. The bandgap energy was decreased when the source mole ratio of Al to Ga was decreased. It was revealed that control regulation of x composition of Ag(Ga1‐x,Alx)Te2 was feasible by varying the source mole ratio Al/(Ga+Al). (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-02-03T07:10:08.461123-05:
DOI: 10.1002/pssc.201510269

• MOCVD growth of ZnO nanowires on Ni–W metallic substrates
• Authors: Gaëlle Amiri; Mohamed Halaoui, Diana Nathalie Montenegro, Pierre Galtier, Vincent Sallet
Pages: 430 - 434
Abstract: Here we investigate the possibility to grow ZnO nanowires on (100) textured Ni‐W substrates by MOCVD at 850 °C. Due to the oxidation of Ni, direct growth of ZnO nanowires on those metallic substrates was not achieved whereas it was easily obtained on sapphire in the same conditions. Therefore, a study of a ZnO buffer layer grown at low temperature was performed in order to prevent the NiO formation. The morphology and the crystallographic orientation of the as‐grown interfacial layers were characterized by scanning emission microscopy (SEM) and XRD diffraction, and are shown to depend on the growth temperature. Subsequently, the growth of ZnO nanowires was carried out on ZnO buffer/Ni‐W pseudo‐substrates. The SEM observations reveal the growth is not homogeneous and depends on the grain orientation. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-02-03T07:10:15.299919-05:
DOI: 10.1002/pssc.201510308

• ZnTe layers on R ‐ and S ‐plane sapphire substrates
• Authors: Taizo Nakasu; Shota Hattori, Takeru Kizu, Wei‐Che Sun, Fukino Kazami, Yuki Hashimoto, Masakazu Kobayashi, Toshiaki Asahi
Pages: 435 - 438
Abstract: ZnTe epilayers were grown on R ‐plane ($10 \bar 1 4$) and S ‐plane ($10 \bar 1 1$) sapphire substrates by molecular beam epitaxy, and the crystal orientation and the optical property were studied. The crystal orientation of ZnTe layers on sapphire substrates was studied using X‐ray diffraction pole figure measurements. It was confirmed that (111)‐oriented domains were formed on the R ‐plane as well as on the S ‐plane substrate. Layers grown on R ‐plane exhibited higher film quality. From the low‐temperature photoluminescence, emissions caused by ZnTe exciton were observed. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-02-09T02:40:11.005934-05:
DOI: 10.1002/pssc.201510265

• Acceptor states in HgCdTe films grown by molecular‐beam epitaxy on
GaAs and Si substrates
• Authors: M. V. Yakushev; K. D. Mynbaev, N. L. Bazhenov, V. S. Varavin, N. N. Mikhailov, D. V. Marin, S. A. Dvoretsky, Yu. G. Sidorov
Pages: 469 - 472
Abstract: A study of defects in HgCdTe films grown by molecular‐beam epitaxy on GaAs and Si substrates was performed. Variable‐temperature photoluminescence (PL) and carrier lifetime measurements were carried out on as‐grown films and films subjected to post‐growth annealings. Films grown on GaAs substrates appeared to be mostly free from defects providing energy states within the bandgap, yet specific acceptor states were generated in these films under conditions associated with mercury deficiency. The properties of films grown on Si substrates were mostly governed by two types of uncontrolled defects. Relatively deep levels with energy 40 to 70 meV were revealed with the use of PL measurements, yet their effect on the lifetime was not traced. The lifetime value was rather determined by other type of defects with energy depth of ∼30 meV. Possible relation of these defects to the specifics of MBE growth of HgCdTe on Si substrates is discussed. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-02-03T06:40:17.545016-05:
DOI: 10.1002/pssc.201510232

• Application of the difference spectroscopy for studying of complex
acceptors in CdTe
• Authors: Victor Bagaev; Vladimir Krivobok, Sergey Nikolaev, Evgeny Onischenko, Anna Pruchkina
Pages: 477 - 480
Abstract: Wavelength modulation of the excitation source combined with the analysis of the differential PL signal have been applied to studying of electronic spectra of acceptors in compensated CdTe:Cl, CdTe:Ag,Cl single crystals. For the Cl‐related complex acceptor with an activation energy of ∼121 meV (A‐center), the energies of eight excited states are measured. In the case of tetrahedral AgCdacceptor the splitting of 2P3/2 (Γ8) and 2S3/2 (Γ8) states has been revealed for AgCd centres located at a short distances (5‐7 nm) from a hydrogen‐like donor (ClTe). A method allowing a simple symmetry test for acceptors in a diverse zinc‐blende compound semiconductor is proposed. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-02-09T02:40:11.888378-05:
DOI: 10.1002/pssc.201510262

• Photoluminescence of high‐resistivity ZnTe crystals doped with
gallium and indium
• Authors: Satoru Seto; Kazuhiko Suzuki
Pages: 490 - 493
Abstract: We have measured photoluminescence spectra of high‐resistivity ZnTe crystals doped with gallium and indium in the wide energy range from near‐band‐edge energy to deep energy region up to 0.78 eV. In the near‐band‐edge energy, we detected a characteristic excitonic peak at 2.363 eV in both gallium and indium doped high resistivity ZnTe. By comparison with a similar PL peak observed in high resistivity CdTe, we identified the characteristic peak at 2.363 eV as emission from excitons bound to defects complex arising from a Zn vacancy and gallium or indium atoms (VZn‐2D). In lower energy range, a newly strong deep emission band near 1.0 eV has been observed for the first time in high‐resistivity ZnTe crystals. The intensity of the deep emission is two order magnitude stronger than that in undoped one. Furthermore, the intensity and peak position of the deep emission band are almost unchanged by Zn‐saturated anneal at 600‐680 °C. We specualte that this deep emission band is responsible for the high resistivity of ZnTe and prevent conversion of n‐type low resistivity. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-02-03T06:40:15.785471-05:
DOI: 10.1002/pssc.201510242

• Electron spin flip Raman spectroscopy of the diluted magnetic
semiconductor Zn1‐xMnxSe below the metal‐insulator transition
• Authors: A. G. Knapp; S. Petznick, F. Jansson, M. Wiemer, M. Hetterich, F. Gebhard, S. D. Baranovskii, P. J. Klar, J. Geurts
Pages: 542 - 545
Abstract: In n‐doped (Zn,Mn)Se, the (s,d) exchange influences the ground state level of the donor‐bound electrons in an external B‐field, depending on their local Mn environment. Due to the statistical Mn arrangement, this should induce a broadening of the donor energy distribution, inducing a magneto‐resistance in transport, and also a broadening of the energy distribution of donor‐bound excitons (D0,X). We have investigated this broadening for Zn0.94Mn0.06Se:Cl (n= 4.5×1017 cm‐3) by electronic spin flip Raman spectroscopy (ESFRS) on the donor electrons. Utilizing the resonant enhancement of the ESFRS intensity upon resonance of the laser light with (D0,X), we actually observe a significant broadening of the ESFRS resonance profiles with increasing B‐field, up to 11.5 meV (FWHM) for B = 5 T. Furthermore we detect a second resonance profile contribution, whose FWHM shows a much weaker B‐field dependence. We assign this contribution to a resonance mediated by the free‐exciton (X0). Our Raman results agree very well with magneto‐transport results at the same sample. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-02-09T02:40:10.240025-05:
DOI: 10.1002/pssc.201510267

• Resonant photoluminescence of a positively charged Mn‐doped quantum
dot
• Authors: A. Lafuente‐Sampietro; H. Boukari, L. Besombes
Pages: 546 - 550
Abstract: We probe the spin dynamics of an individual magnetic atom (Mn) coupled to carriers in a positively charged quantum dot using resonant photoluminescence. We demonstrate that a p‐doped CdTe/ZnTe quantum dot containing a single Mn atom forms an ensemble of optical Λ systems which can be addressed independently. Performing resonant optical pumping experiment and auto‐correlation of the resonant photoluminescence, we show that these Λ systems are connected through inefficient forbidden spin‐flips. We demonstrate that the spin dynamics of X+‐Mn under resonant excitation is mainly controlled by the electron‐Mn interaction. This coherent dynamics is directly observed in the time domain and is shown to be highly sensitive to the local strain at the Mn location. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-02-03T07:10:09.451634-05:
DOI: 10.1002/pssc.201510248

• Spin properties of localized hole and resident electron in ZnO epilayers
• Authors: Jungtaek Kim; J. Puls, S. Sadofev
Pages: 551 - 554
Abstract: The spin dynamic of the hole localized inside the donor bound exciton (D0X) and donor electrons is studied in ZnO epilayer by time‐resolved optical orientation of the D0X photoluminescence and the absorption bleaching of the spin‐sensitive D0X transition, respectively. A D0X life time of 140 ps and hole spin relaxation time of 80 ps are extracted. The comparable times allows us for an effective pumping of the donor electron spin via circularly polarized excitation.Long electron spin relaxation times in the 1 μs range are uncovered if the hyperfine interaction is suppressed by a proper longitudinal magnetic field B‖. A field strength of ≈2 mT is large enough to achieve that proving the extremely small Overhauser field BN acting on localized electrons. This is a direct result of the small abundance of magnetic nuclei interacting inside the small donor volume both specific for ZnO. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-02-03T07:10:04.6489-05:00
DOI: 10.1002/pssc.201510292

• Magnetic phase transitions in ZnO doped by transition metals
• Authors: Shavkat Yuldashev; Vadim Yalishev, Ziyodbek Yunusov, Younghae Kwon, Tae Won Kang
Pages: 559 - 563
Abstract: In this work we present the results on experimental study of magnetic phase transitions in ZnO thin films doped by Mn and Co by using the thermal diffusivity and specific heat measurements. The inverted lambda‐shaped peaks observed in the temperature dependencies of the thermal diffusivity demonstrate the existence of the second order phase transitions in these samples. The magnetic entropy derived from the specific heat gives the number of magnetic ions involved in the magnetic ordering. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-02-09T02:40:16.367901-05:
DOI: 10.1002/pssc.201510221

• Annealing of frozen‐in defects in ZnO
• Authors: T. Nirk; K. Lott, V. Seeman, L. Türn, M. Viljus, A. Öpik
Pages: 590 - 593
Abstract: High temperature electrical conductivity (HTEC) as a function of time after step‐like change of Zn vapor pressure (PZn) at fixed ZnO crystal temperature (TZnO) and after step‐like change of TZnO at fixed PZn was measured in undoped ZnO single crystal and in undoped ZnO ceramic sample. It was found a difference on HTEC relaxation curves in these measurements. Samples were cooled from temperature 1273 K to room temperature. Appearance of asymmetric spectrum with g≈1.96 and disappearance of Mn2+ spectrum were detected in EPR investigations. Then vacuum annealing was applied for these samples and intensity of g≈1.96 EPR spectrum was registered after every vacuum annealing cycles. The change in sample color, the change in g≈1.96 spectrum intensity as well as appearance again of Mn2+ EPR spectrum in the course of vacuum annealing was explained by the model of defect clusters formed during cooling of the crystal. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-02-03T06:40:11.66814-05:0
DOI: 10.1002/pssc.201510244

• Defect related emission of ZnO and ZnO Cu nanocrystals prepared by
electrochemical method
• Authors: T. V. Torchynska; B. El Filali, I. Ch. Ballardo Rodríguez, L. Shcherbyna
Pages: 594 - 597
Abstract: Photoluminescence (PL), its temperature dependence, and SEM images have been applied for the comparative study of the ZnO and ZnO Cu nanocrystals (NCs). NCs were created by the electrochemical (anodization) method with different NC sizes and annealed at 400 °C for 2 hours in ambient air. PL spectra show a near band edge (NBE) emission and three defect‐related PL bands in ZnO NCs, and four defect‐related PL bands in ZnO Cu NCs. The defect related PL band with the peak at 2.60‐2.70 eV is connected with the Cu complexes in ZnO Cu NCs. PL spectra of all PL bands in both NC types were studied in the temperature range 10‐300 K. Their integrated PL intensities and the activation energies of PL thermal decays have been estimated. It is shown that the PL intensities of defect related PL bands have been stimulated essentially at doping by the small Cu concentration (2.2%) in ZnO Cu NCs. It is revealed additionally that the Cu doping leads to decreasing the activation energies of thermal decay for the defect related PL bands in ZnO Cu NCs in comparison with those in ZnO NCs. The physical reason of this effect and the mechanisms of optical transitions for defect related PL bands in ZnO NCs have been discussed. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-02-03T07:10:06.711892-05:
DOI: 10.1002/pssc.201510277

• Anisotropic optical properties of a homoepitaxial (Zn,Mg)O/ZnO quantum
well grown on a‐plane ZnO substrate
• Authors: Mohammed J. Mohammed Ali; J.M. Chauveau, T. Bretagnon
Pages: 598 - 601
Abstract: The optical properties of homoepitaxial non‐polar (Zn,Mg)O/ZnO single quantum wells (QWs) grown by molecular beam epitaxy on a‐plane (11‐20) ZnO substrates are investigated by using reflectance and continuous wave photoluminescence spectroscopies. The reflectivity and CW‐PL spectra measured at low temperature reveal strong in‐plane optical anisotropies and clear reflectance structures. The signatures of confined excitons analogous to C‐exciton and (A, B)‐excitons in bulk ZnO, are detected using light polarized respectively along the c‐axis and perpendicular to this axis. Temperature dependence of CW‐PL has been investigated in the two polarizations. For electric field of the light perpendicular to the c‐axis the total intensity of the PL lines decreases by about an order of magnitude when the temperature increases from 8 K to room temperature. At low temperature a line associated to an excitonic complex dominates the PL spectrum. When the temperature increases the intensity of this line decreases as the intensity of the line associated to the free exciton increases. In the other polarization for temperature above 100 K a new line appears in the spectrum. Its intensity increases with temperature. This feature is associated to the c‐like free exciton. The degree of polarization of these lines is independent of temperature. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-02-03T06:40:16.654959-05:
DOI: 10.1002/pssc.201510238

• Quantum confined Stark effect of polar and non‐polar ZnO/ZnMgO
quantum wells grown by MBE
• Authors: Tomoki Abe; Tatsuya Motoyama, Masaya Yamamoto, Atsushi Yamamoto, Shohei Iwagashita, Hirofumi Kasada, Koshi Ando, Kunio Ichino
Pages: 602 - 605
Abstract: We have investigated quantum confined Stark effects of polar (O‐polar) and non‐polar ZnO/ZnMgO quantum wells (QWs) by electroabsorption (EA) spectroscopy. The ZnO/ZnMgO QWs were grown by plasma assisted molecular beam epitaxy (PA‐MBE). The ZnO/ZnMgO QWs were grown on c‐plane sapphire for polar ZnO QWs, and on r‐plane sapphire for non‐polar ZnO QWs, respectively. The polar ZnO/ZnMgO QWs exhibited a blue‐shift of 20 meV in excitonic transition energy by applying external bias at room temperature. This blue‐shift is due to reverse quantum confined Stark effect (QCSE) in a piezo electric‐field induced QW structures of wurtzite ZnO/ZnMgO QWs with c‐axis orientation. We confirmed a large red‐shift of 29 meV for non‐polar ZnO/ZnMgO QWs. This energy shift is originated from normal QCSE in the flat potential QWs without built‐in piezo electric‐field. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-02-03T07:10:07.589609-05:
DOI: 10.1002/pssc.201510272

• Gamma‐ray tolerance of CdS/CdTe photodiodes for radiation tolerant
compact image sensor with field emitter array
• Authors: Tamotsu Okamoto; Tomoya Igari, Yasuhito Gotoh, Nobuhiro Sato, Masafumi Akiyoshi, Ikuji Takagi
Pages: 635 - 638
Abstract: The effect of gamma irradiation on two types (superstrate‐ and substrate‐type) of CdS/CdTe photodiodes, which we have proposed as potential photoconducting films for compact image sensors with a field emitter array (FEA), was investigated. A 60Co gamma‐ray source was employed, and the total gamma irradiation dose was more than 500 kGy. For the superstrate‐type structure, the irradiation caused the short‐circuit current density (JSC) to decrease, probably due to the resulting decreased transmittance of the glass substrate. On the other hand, little degradation of the I ‐V characteristics or spectral response was observed after the gamma irradiation for the substrate‐type structure. These results suggest that, taking into account the decrease in transmittance of the glass substrate, the CdS/CdTe photodiodes have sufficient tolerance to high gamma‐ray exposure. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-02-03T06:40:19.140073-05:
DOI: 10.1002/pssc.201510229

• Multi‐band radiation detector based on HgCdTe heterostructure
• Authors: T. Kryshtab; R. K. Savkina, A. B. Smirnov, M. Kladkevich, V. Samoylov
Pages: 639 - 642
Abstract: We describe multi‐band radiation detector based on HgCdTe/Si heterostructure, which exhibits sensitivity in the MWIR and LWIR spectral range without cryogenic cooling to achieve useful performance. The noise equivalent power (NEP) for one of the detectors studied reached NEP296 K= 3.8×10‐13W/Hz1/2. HgCdTe‐based heterostructure is also considered as sub‐THz detector. The sensitivity of HgCdTe‐based heterostructure for sub‐THz radiation was found after the oblique‐incidence (45°) bombardment with silver ions (140 keV). The signal was detected without antenna and amplification and NEP at ν≈140 GHz and 296 K reaches 4.5×10‐8W/Hz1/2. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-02-03T07:10:05.804674-05:
DOI: 10.1002/pssc.201510278

• Application of indium tin oxide to the p‐cladding layers of yellow/green
II‐VI compound semiconductor laser diode structures on InP substrates
• Authors: Koji Fukushima; Tomohiro Shiraishi, Ryohei Kobayashi, Katsumi Kishino, Ichirou Nomura
Pages: 665 - 668
Abstract: The application of indium tin oxide (ITO) as the p‐cladding layer of II‐VI compound semiconductor laser diodes (LDs) on InP substrates was investigated. The waveguide analysis of the LD structures revealed that the optical confinement effect around the active layer was obviously improved by changing the p‐cladding layer from the conventional MgSe/BeZnTe superlattice to ITO. For example, the estimated optical confinement factors were 0.15 and 0.27 for the conventional and ITO LD structure, respectively, when the emission wavelength was 580 nm. In addition, we investigated optimum LD structures, considering the optical and carrier confinements at the active layer. In experiments, light emitting devices with an ITO layer were fabricated on InP substrates via molecular beam epitaxy and radio‐frequency (RF) magnetron sputtering. Yellow emissions at 582 nm were observed by current injections at room temperature. These results indicate that ITO is a promising p‐cladding layer material for II‐VI LDs on InP substrates. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-02-09T02:40:13.832463-05:
DOI: 10.1002/pssc.201510254

• Growth and characterization of ZnCdSe/ZnCdMgSe two‐color quantum
well infrared photodetectors
• Authors: Guopeng Chen; Yasin Kaya, Arvind Pawan Ravikumar, Maria C. Tamargo, Claire F. Gmachl, Aidong Shen
Pages: 673 - 676
Abstract: The authors report, for the first time, the new two‐color quantum well infrared photodetectors (QWIPs) from a non‐III‐V semiconductor material system. The samples were grown on InP substrate by molecular beam epitaxy. X‐ray diffraction and photoluminescence measurements showed high structural and optical quality of the samples. Two intersubband (ISB) absorption peaks in two different wavelength regions are observed in Fourier transform infrared measurements. The two‐color photodetectors can be turned on separately or simultaneously in the two spectral regions. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2016-02-09T02:40:12.681193-05:
DOI: 10.1002/pssc.201510257

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