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Journal Cover physica status solidi (c)
  [SJR: 0.392]   [H-I: 39]   [1 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 1862-6351 - ISSN (Online) 1610-1642
   Published by John Wiley and Sons Homepage  [1605 journals]
  • Secondary ion mass spectrometry as a tool to study selenium gradient in
           Cu2ZnSn(S,Se)4
    • Authors: Sigbjørn Grini; Nils Ross, Thomas Neset Sky, Clas Persson, Charlotte Platzer-Björkman, Lasse Vines
      Abstract: Secondary ion mass spectrometry (SIMS) has been utilized to study compositional gradients in compound-sputtered and annealed Cu2ZnSn(S,Se)4 (CZTSSe). SIMS image depth profiling shows a non-uniform spatial distribution of selenium and supports a mechanism where selenization is accompanied by grain growth rather than substitution of selenium for sulfur. Furthermore, SIMS depth profiles of S and Se using O2+ primary ions and detecting molecular ions of the MCs+ type using Cs+ primary ions have been compared, where a linear relationship between the sulfur and selenium concentration suitable for compositional analysis is observed for concentrations with an Se/(S+Se) ratio in the range from 0.25 to 0.65.3D image of the spatial Se distribution in a 20 × 20 μm2 grid measured with SIMS image depth profiling.
      PubDate: 2017-02-21T09:46:20.797461-05:
      DOI: 10.1002/pssc.201600187
       
  • Yb valence state in Yb5Rh4Ge10
    • Authors: Hitoshi Sato; Yuki Utsumi, Kenichi Katoh, Kojiro Mimura, Shigenori Ueda, Hitoshi Yamaoka, Awabaikeli Rousuli, Masashi Arita, Kazunori Umeo, Kenya Shimada, Hirofumi Namatame, Masaki Taniguchi
      Abstract: Temperature- and pressure-dependent Yb valence state in Yb5Rh4Ge10 has been investigated by means of Yb 3d hard X-ray photoemission spectroscopy (HAXPES) and Yb L3 absorption spectroscopy (XAS). The mean Yb valence derived from the Yb 3d HAXPES is estimated to be ∼2.78 at 300 K and decreases to ∼2.74 at 20 K. On the other hand, the Yb valence deduced from the Yb L3 XAS at 300 K is almost constant with ∼2.81 in the pressure range between 9.2 and 34.7 GPa.
      PubDate: 2017-02-21T09:45:58.549549-05:
      DOI: 10.1002/pssc.201600164
       
  • Site selective doping of Zn for the p-type Cu(In,Ga)Se2 thin film for
           solar cell application
    • Authors: Sho Shirakata
      Abstract: Selective doping of a Zn impurity at the group III site in a Cu(In, Ga)Se2 (CIGS) film was performed by the doping of Zn at the first stage of the three-stage method. The p-type CIGS:Zn film was obtained, which is in contrast to the n-type CIGS:Zn film obtained by the Zn impurity doping at the second and third-stages. Based on excitation intensity dependence of photoluminescence (PL) at low-temperature, the change in the acceptor level was observed. The enhancement of carrier concentration as a result of Zn-doping in the p-type CIGS:Zn film was observed. The CIGS:Zn solar cells exhibited η of 14.5% and Voc of 0.658 V, which are higher than that of the corresponding solar cells using the undoped CIGS films
      PubDate: 2017-02-21T09:01:06.239851-05:
      DOI: 10.1002/pssc.201600170
       
  • Ionization effects on Cu(In, Ga)Se2 thin-film solar cells
    • Authors: Shirou Kawakita; Mitsuru Imaizumi, Shogo Ishizuka, Hajime Shibata, Shuichi Okuda
      Abstract: Cu (In, Ga) Se2 (CIGS) solar cells were irradiated with 60, 100, and 250 keV electrons to reveal the characteristics of radiation induced defects. Electrons with less than 200 keV energy cannot generate any displacement defects in CIGS materials. In addition, a low amount of the electrons can improve the roll-over behavior in current-voltage characteristics of CIGS solar cells. However, the deterioration of the electrical performance in CIGS solar cells irradiated with a high amount of electrons was observed. The deterioration rate on the cells irradiated with lower-energy electrons was higher than that induced by electrons with higher-energy. The degradation curve of JSC based on the ionizing dose estimated from the ionizing energy loss model does not depend on the energy of electrons. Therefore, it implies that the electrons can degrade CIGS solar cells due to the ionization effect.
      PubDate: 2017-02-21T08:56:10.496381-05:
      DOI: 10.1002/pssc.201600168
       
  • Phase transformation during simultaneous chalcogenization of CuIn(S,Se)2
           thin films using metalorganic sources
    • Authors: Ryuki Shoji; Yoshiki Kayama, Shigefusa F. Chichibu, Mutsumi Sugiyama
      Abstract: Simultaneous chalcogenization of CuIn(Sy,Se1-y)2 (CISSe) thin films has been demonstrated using organometallic sources such as diethylselenide [(C2H5)2Se] and ditertiarybutylsulfide [(t-C4H9)2S] to obtain homogeneous CISSe pseudobinary alloys with controlled amounts of Se and S species. Low-temperature chalcogenization at 300 °C resulted in the formation of Cu-SSe and In-SSe alloys diffused into the Cu11In9 metallic precursor. On the other hand, high-temperature chalcogenization produced CISSe thin films without additional phases. The obtained results can be used for elucidating the mechanism of simultaneous chalcogenization and development of high-performance and cost-effective commercial applications.
      PubDate: 2017-02-21T08:51:03.580264-05:
      DOI: 10.1002/pssc.201600159
       
  • Correcting for interference effects in the photoluminescence of
           Cu(In,Ga)Se2 thin films
    • Authors: Max Hilaire Wolter; Benjamin Bissig, Patrick Reinhard, Stephan Buecheler, Philip Jackson, Susanne Siebentritt
      Abstract: Photoluminescence (PL) measurements are performed on high-quality Cu(In,Ga)Se2 (CIGS) thin films with the intention of investigating their electronic structure. Due to the nature of the CIGS absorbers, notably their smooth surface and a graded band gap, the measured PL spectra are distorted by interference effects, limiting thus the information that one can gain. Here we show that, by varying the entrance angle of the laser light and the detection angle of the emitted PL, we are able to correct for interference effects. As a result, we receive interference-free PL spectra that enable us to determine quantities such as band gap energies and quasi-Fermi level splittings (QFLS). Furthermore, we show that it is possible to measure the QFLS even without correcting for interference effects and we compare the QFLS to the open circuit voltage for a particular sample.
      PubDate: 2017-02-21T08:46:04.895504-05:
      DOI: 10.1002/pssc.201600189
       
  • Synthesis and characterization of Cu2ZnSnS4 bulk polycrystalline
    • Authors: Akiko Takeuchi; Koichiro Oishi, Naritoshi Aoyagi, Genki Nishida, Wataru Shimizu, Masato Nakagawa, Makoto Yamazaki, Hironori Katagiri
      Abstract: Cu2ZnSnS4 bulk polycrystalline were synthesized by pressureless sintering (PLS) method in vacuum and spark plasma sintering (SPS) method. It was confirmed that there were no the secondary phases in a sample sintered by SPS method at 750 °C from the results of powder X-ray diffraction (XRD) patterns and Rietveld refinement. The Raman spectrum of the sample showed the strongest peak at 338 cm−1 with a shoulder at 350–370 cm−1, and the weaker peaks at about 255 and 289 cm−1, which originated from Cu2ZnSnS4. The FWHM of the strongest peak of 7.4 cm−1 was narrower than other samples. The photoluminescence (PL) spectrum measured at 15 K were observed a broad emission band with the maximum at 1.26 eV. Also, the measured photoluminescence excitation (PLE) for the band-edge emission was originated the energy transfer from the band-to-band excitation.The obtained activation energy was 62 ± 9 meV.
      PubDate: 2017-02-21T05:41:09.416373-05:
      DOI: 10.1002/pssc.201600188
       
  • Morphology of multiple-selenized Cu2ZnSn(S,Se)4 absorber layers
    • Authors: Markus Neuwirth; Jasmin Seeger, Heinz Kalt, Michael Hetterich
      Abstract: The impact of multiple-selenization of wet-chemical precursors for kesterite-type Cu2ZnSn(S,Se)4 solar cells is reported. The absorber forms a compact layer with mostly big grains. Gaps between the big grains are filled with smaller grains. Also the absorber lacks the common trilayer/multilayer structure. As a result the layer thickness is more homogeneous and the morphology is more evened out. This is the basis for a more homogeneous device parameter distribution across large samples and a better reproducibility of CZTSSe solar cells.
      PubDate: 2017-02-21T05:37:23.794821-05:
      DOI: 10.1002/pssc.201600163
       
  • Improvement of photoelectric conversion efficiencies of dye-sensitized
           solar cells consisting of hemispherical TiO2 films
    • Authors: Shogo Izumi; Ayame Mizuno, Naoki Ohtani
      Abstract: To improve the photoelectric conversion efficiency (PCE) of dye-sensitized solar cells (DSSCs), we fabricated hemispherical TiO2 films using a poly(dimethylsiloxane) mold and improved the light harvesting efficiency in DSSCs by a large light-scattering effect caused by the hemispherical structure. In addition, the amount of the adsorption density of the dye in TiO2 increased due to the larger surface area of the hemispherical structure. Consequently, the short-circuit current of DSSCs containing hemispherical TiO2 film increased even though the open-circuit voltage was not changed. As a result, the overall PCE value was improved to about 1.2 times larger than a DSSC containing a flat TiO2 film.In addition, polyethylene glycol-doping in TiO2 effectively improved the DSSC performance comprised of hemispherical TiO2 films.
      PubDate: 2017-02-21T05:36:50.700637-05:
      DOI: 10.1002/pssc.201600186
       
  • Chemical composition dependence of photoluminescence from Cu2ZnSnS4 thin
           films with potential fluctuations
    • Authors: Kunihiko Tanaka; Yoshiharu Takamatsu, Shinya Miura
      Abstract: The temperature and excitation intensity dependence of photoluminescence (PL) spectra from Cu2ZnSnS4 (CZTS) thin films with various chemical compositions was investigated. Three types of CZTS thin films were examined: Zn-rich (group A), Cu- and Zn-poor (group B), and Cu-rich and Zn-poor (group C). Groups A, B, and C gave PL spectra with peaks at around 1.2, 1.30, and 1.45 eV, respectively. These spectra exhibited large peak energy shifts to higher energies as the excitation intensity increased by more than 10 meV/decade due to potential fluctuations. The PL spectra of groups A and B can be attributed to band-to-impurity luminescence, and the origin of the spectra was found to be CuSn and VZn or [VZn + SnZn], respectively. The potential fluctuations were estimated from the lower energy side of the PL spectra, and the Cu-poor samples exhibited smaller potential fluctuations.
      PubDate: 2017-02-21T05:25:41.120508-05:
      DOI: 10.1002/pssc.201600138
       
  • Optical and magnetic properties of some XMnSb and Co2YZ Compounds: ab
           initio calculations
    • Authors: Selami Palaz; Husnu Koc, Haci Ozisik, Engin Deligoz, Amirullah M. Mamedov, Ekmel Ozbay
      Abstract: In present work, our research is mainly focused on the electronic structures, optical, and magnetic properties of XMnSb (X = Ni, Cu, Pd), Co2YZ (Y = Ti; Z=Si, Ge, Sn), and Co2YZ (Y =Mn; Z=Al, Ga, Si) Heusler compounds by using ab initio calculations within the generalized gradient approximation. The calculations are performed by using the Vienna ab initio simulation package based on the density functional theory. The band structure of these Heusler alloys for majority spin and minority spin were calculated and the majority spin states cross the Fermi level and thus have the metallic character, while the minority spin states open the band gaps around the Fermi level and thus have the narrow-band semiconducting nature. We also find that these Heusler compounds have the indirect band gaps in the minority spin channel. The real and imaginary parts of dielectric functions and hence the optical functions such as energy-loss function, the effective number of valance electrons and the effective optical dielectric constant for XMnSb and Co2YZ compounds were also calculated. In addition, we also show the variations of the total magnetic moment per f.u. and minority spin gap width of these compounds with optimized lattice constants: minority spin gap width decreases with increasing the lattice constants.
      PubDate: 2017-02-20T07:25:28.336014-05:
      DOI: 10.1002/pssc.201600182
       
  • Temperature dependence of low-frequency polarized Raman scattering spectra
           in TlInS2
    • Authors: Raul Paucar; YongGu Shim, Kojiro Mimura, Kazuki Wakita, Oktay Alekperov, Nazim Mamedov
      Abstract: In this work, we examined phase transitions in the layered ternary thallium chalcogenide TlInS2 by studying the temperature dependence of polarized Raman spectra with the aid of the Raman confocal microscope system. The Raman spectra were measured over the temperature range of 77–320 K (which includes the range of successive phase transitions) in the low-frequency region of 35–180 cm−1. The optical phonons that showed strong temperature dependence were identified as interlayer vibrations related to phase transitions, while the phonons that showed weak temperature dependence were identified as intralayer vibrations.
      PubDate: 2017-02-20T07:25:24.966134-05:
      DOI: 10.1002/pssc.201600214
       
  • Nanostructured CdS thin films deposited by spray pyrolysis method
    • Authors: A. Kerimova; E. Bagiyev, E. Aliyeva, A. Bayramov
      Abstract: Influence of solution pH on the structural and optical properties of CdS films deposited by conventional spray pyrolysis technique was studied. X-Ray Diffraction (XRD), Atomic Force Microscopy (AFM), Photoluminescence spectroscopy (PLS), and Spectroscopic Ellipsometry (SE) methods were used for the characterization of the deposited films. PL spectrum of the film deposited from the solution with pH = 10.2 shows broad-band PL emission located at 460 nm (2.7 eV), which can be attributed to the quantum size effect at grain sizes of
      PubDate: 2017-02-20T07:25:21.128414-05:
      DOI: 10.1002/pssc.201600144
       
  • AIBIIICVI2 (A = Cu, Ag; B = Ga, In; C = S, Se, Te) based
           photonic crystal superlattices: Optical properties
    • Authors: Sevket Simsek; Selami Palaz, Chingiz Akhundov, Amirullah M. Mamedov, Ekmel Ozbay
      Abstract: In this study, we present an investigation of the optical properties and band structures for the photonic structures based on AIBIIICVI2 with a Fibonacci sequence that can act as a multi-wavelength birefringent filter. The filtering wavelengths are analyzed by the indices concerning the quasi-periodicity of a Fibonacci sequence and the average lattice parameter. The transmittances of filtering wavelengths can be tuned by varying structure parameters such as the lengths of poled domains, filling factor, and dispersion relation. In our simulation, we employed the finite-difference time domain (FDTD) technique, which implies a solution from Maxwell equation.
      PubDate: 2017-02-20T07:20:39.538532-05:
      DOI: 10.1002/pssc.201600156
       
  • Annealing behaviour of photoluminescence spectra on Cu2ZnSnS4 single
           crystals
    • Authors: Satoru Seto; Hideaki Araki
      Abstract: We have measured photoluminescence (PL) spectra at 10 K for Cu2ZnSnS4 (CZTS) single crystals grown by the iodine transport method and explored the anneal changes of PL spectra under a Zn and S-saturation. All the crystals showed S- and Zn-poor composition, and nearly stoichiometric composition of Cu/(Zn + Sn). The observed PL spectra are divided into two groups; one is PL band with a peak at ∼1.3 eV (1.3-eV band), and another is PL band with a peak at ∼1.35 eV (1.35-eV band). It was found from SEM observations that the 1.35-eV band was observed in crystals with a mirror-like facet and, on the other hand, the 1.3-eV band was seen in the crystals with some small dark areas where the composition is Cu-poor. The Zn-saturated annealing at 600 °C caused the PL peak shift of ∼0.1 eV, from 1.295 to 1.185 eV. The S-saturated annealing at 550 °C caused a disappearance of PL emission. The implications of these annealing behaviour are discussed.
      PubDate: 2017-02-20T07:20:37.003253-05:
      DOI: 10.1002/pssc.201600158
       
  • The influence of phonon focusing on density of states and the Knudsen
           phonon gas flow in nanowires with different types of anisotropy of elastic
           energy
    • Authors: I. I. Kuleyev; S. M. Bakharev, I. G. Kuleyev, V. V. Ustinov
      Abstract: The influence of elastic energy anisotropy on phonon density of states (PDOS) and phonon mean free paths for acoustic modes in nanowires of cubic crystals with positive (Ge, Si, LiF, GaSb, GaAs, and GaN) and negative (CaF2, SrF2, and PbS) anisotropy of the second order elastic moduli has been investigated. The proposed calculation method allows one to determine angular distributions of the PDOS of fast and slow quasi-transverse modes in elastically anisotropic crystals for phonon focusing and defocusing regions. It has been shown that the PDOS and the phonon mean free paths in the cubic crystals take maximum and minimum values in the directions of phonon focusing and defocusing, respectively. Moreover, the anisotropy of the crystals differs qualitatively: the maxima values for the type-I crystals correspond to the minima for the type-II crystals. The heat flux directions that provide the maximum and minimum phonon thermal conductivity in the nanowires have been identified.
      PubDate: 2017-02-17T09:20:56.183386-05:
      DOI: 10.1002/pssc.201600263
       
  • Composition-ratio control of CZTS films deposited by PLD
    • Authors: Masahiro Kotani; Hiroki Miura, Yong-Gu Shim, Kazuki Wakita
      Abstract: The control of the composition of the CZTS polycrystals has been examined. CZTS poly-crystal, ZnS, and SnS powders were mixed for adjusting the composition and were sintered at temperature of 400 °C. We evaluated polycrystal with the molar ratios of Cu/(Zn+Sn) = 0.79, Zn/Sn = 1.04, and S/(Cu+Zn+Sn) = 0.95. Then, we prepared CZTS film by PLD method using the CZTS polycrystal as a target. Composition content of the film was also evaluated to be the molar ratios of Cu/(Zn+Sn) = 1.14, Zn/Sn = 1.04, and S/(Cu+Zn+Sn) = 0.69. The film indicats slightly Cu-rich, and S-poor compositions, and no change of Zn/Sn rate. Definitely, we successfully performed composition control and improvement of composition uniformity for polycrystals by using the source materials of CZTS, ZnS, and SnS. Additionally, we prepared homogeneous CZTS film with either a kesterite or a stannite structure by PLD method.
      PubDate: 2017-02-17T09:20:53.672332-05:
      DOI: 10.1002/pssc.201600212
       
  • Low band-gap CuIn(S,Se)2 thin film solar cells using molecular ink with
           9.5% efficiency
    • Authors: Yajie Wang; Xianzhong Lin, Lan Wang, Tristan Köhler, Martha Ch. Lux-Steiner, Reiner Klenk
      Abstract: Vacuum free, solution based routes to the preparation of chalcopyrite absorbers for solar cells promise options in device design and manufacturing that are not provided by the standard vacuum based approaches. In order to fully exploit these options, the precursor should contain neither nanoparticles nor hazardous chemicals, and it should be stable under ambient conditions. In this contribution we report on CuIn(S,Se)2 thin film preparation based on spin coating of an air stable molecular ink containing metal chlorides and thiourea in organic solvents. Several key parameters directly influencing the performance of the resulting solar cells have been identified. Wetting of the glass/Mo substrate has been adjusted by varying the concentration of ethylene glycol butyl ether in the ink. Before annealing in Ar/Se at atmospheric pressure, several cycles of ink deposition and drying can be used to increase the thickness of the precursor stack. Careful balancing of ink concentration, number of precursor deposition cycles, and annealing temperature profile will transform the multi-layer precursor into a sufficiently thick, continuous, large grained film as required for high quantum efficiency, and good red response of the cells. These optimizations aimed at high photo current have already led to an efficiency of 9.5%.
      PubDate: 2017-02-17T09:20:49.645152-05:
      DOI: 10.1002/pssc.201600169
       
  • Issue Information: Phys. Status Solidi C 1–2/2017
    • Abstract: No abstract is available for this article.
      PubDate: 2017-01-30T07:27:25.900893-05:
      DOI: 10.1002/pssc.201770112
       
  • Cover Picture: Phys. Status Solidi C 1–2/2017
    • Abstract: No abstract is available for this article.In order to obtain good crystallographic properties of tin dioxide, a candidate for realizing next-generation electrical and optical devices, relatively expensive film formation methods such as MOCVD or MBE are required. One alternative approach is a mist chemical vapour deposition (mist-CVD), which can form various oxide semiconductors under atmospheric pressure with a simple and less expensive technique. Yatabe et al. (article No. 1600148) have grown SnO2 thin films on 2-inch diameter m-plane sapphire substrates by mist-CVD at atmospheric pressure. From XRD and EBSD measure¬ments the authors found that the SnO2 films were epitaxially grown on the substrates under optimised growth condition. Epitaxial growth of the SnO2 thin film at three typical areas on the substrate was confirmed by EBSD measurements. Finally, a second SnO2 layer was overgrown on the single-crystalline SnO2 thin film, which functioned as a buffer layer (see cover image). This method drastically improved the surface rough¬ness of the second SnO2 layer.
      PubDate: 2017-01-30T07:27:25.178644-05:
      DOI: 10.1002/pssc.201770012
       
  • A rapid decade with pss (RRL) – and now Solar RRL is here
    • Abstract: No abstract is available for this article.
      PubDate: 2017-01-30T07:27:24.192285-05:
      DOI: 10.1002/pssc.201720112
       
  • Contents: Phys. Status Solidi C 1–2/2017
    • Abstract: No abstract is available for this article.
      PubDate: 2017-01-30T07:27:23.363562-05:
      DOI: 10.1002/pssc.201720012
       
  • Morphologies and photoluminescence properties of GaN-based thin films
           grown on non-single-crystalline substrates
    • Authors: Yuichi Sato; Atomu Fujiwara, Shota Ishizaki, Shun Nakane, Yoshifumi Murakami
      Abstract: Morphologies and photoluminescence properties of gallium nitride-based thin films grown on non-single-crystalline substrates were investigated. The films were directly grown on quartz glass and amorphous-carbon-coated graphite substrates by a molecular beam epitaxy apparatus which has dual nitrogen plasma cells. Co-supplying of indium and gallium with simultaneous operation of the dual nitrogen plasma cells brought isolated and nano-pillar-shaped structures to the films. On the other hand, such structures were not obtained when the films were grown by the single plasma cell operation. Photoluminescence (PL) properties of the films greatly depended upon the morphologies. The intensities of the PL peaks emitted from the films which have such nano-pillar shaped structures were quite intense although the peak energies shifted to lower energy sides compared with those of the films grown by the single plasma cell operation. (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2016-12-22T10:10:05.00818-05:0
      DOI: 10.1002/pssc.201600151
       
  • Structural and electrical properties of semipolar (11-22) AlGaN grown on m
           -plane (1-100) sapphire substrates
    • Authors: Masafumi Jo; Issei Oshima, Takuma Matsumoto, Noritoshi Maeda, Norihiko Kamata, Hideki Hirayama
      Abstract: Semipolar III-nitrides have attracted increasing attention because of the reduced piezoelectric field in the active layer. In particular, (11-22) plane is promising due to the small polarization field along the growth axis and the epitaxial matching on m -plane sapphire. The aim of this study was to assess the effect of growth conditions on the structural and electrical properties of Si-doped (11-22) AlGaN. Semipolar AlGaN/AlN layers were grown on m -plane sapphire by metal-organic chemical vapor deposition at different temperatures, V/III ratios, and tetraethylesilane flows. Surface morphology, crystalline quality, and electrical properties of the AlGaN layers were investigated with AFM, XRD, and by Hall measurements, respectively. (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2016-12-13T05:10:07.660439-05:
      DOI: 10.1002/pssc.201600248
       
  • Adsorption behavior of B-doped/N-doped graphene sheets toward NO2, NO and
           NH3 molecules: A first-principles study
    • Authors: Yin Wang; Jinghua Chen, Xintang Huang
      Abstract: Based on the first-principles of density-functional theory (DFT), the effects of NO2, NO and NH3 adsorption on the change in geometric stability, adsorption properties and electronic structures of B-doped or N-doped graphene are investigated. For NO/NO2-B/N-doped graphene systems, NO/NO2 have more stability on B-doped graphenes than them on N-doped graphenes. The introduction of B atom can make the adsorption of NO/NO2 on graphene much easier. The stable configuration of B-doped graphene is more likely to be gas sensor for detecting toxic gases such as NO2 and NO. This makes it possible to use B-doped graphene as sensing materials for designing novel gas sensors. The interaction between NH3 and B/N-doped graphene is rather weak. The results will provide a new direction for the adsorbed NO2, NO and NH3 on graphene by introducing B/N doping atoms into graphene. (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2016-12-13T04:51:50.424416-05:
      DOI: 10.1002/pssc.201600110
       
  • Reduction of contact resistance in V-based electrode for high AlN molar
           fraction n-type AlGaN by using thin SiNx intermediate layer
    • Authors: Noriaki Nagata; Takashi Senga, Motoaki Iwaya, Tetsuya Takeuchi, Satoshi Kamiyama, Isamu Akasaki
      Abstract: We found out the reduction of contact resistance in V-based electrode for high AlN molar fraction n-type AlGaN by using thin SiNx intermediate layer. The contact resistivity for n -type Al0.70Ga0.30N with the V/Al/Ni/Au electrode using SiNx intermediated layer reached 1.13 × 10-6 Ω cm2. Moreover, contact resistivity using SiNx intermediated layer had been reduced more than one order of magnitude in all AlN molar fractions from 0.62 to 0.87. Using this electrode, we also demonstrated UV light-emitting diodes (LEDs) on n -type Al0.70Ga0.30N underlying layer with an emission wavelength of approximately 283 nm. An operating LED voltage using a V/Al/Ni/Au electrode with SiNx intermediated layer was 3.3 V lower at 100 mA current injection than that without SiNx intermediated layer. (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2016-12-13T04:51:49.290458-05:
      DOI: 10.1002/pssc.201600243
       
  • A model of order-order transition in titanium monoxide TiO1.0
    • Authors: Maxim G. Kostenko; Sergey V. Sharf, Andrey A. Rempel
      Abstract: A new class of defect structures has been proposed, in which point defects of the crystal lattice occupy the sites of two different superstructures simultaneously. The formation of these structural modifications is due to the order-order equilibrium phase transition of the second order that does not proceed completely. Using atomic-vacancy ordering in titanium monoxide TiO1.0 as an example, we have studied the permissible ratio between the long-range order parameters in the structural modification formed by a combination of monoclinic M5X5 (mon) (space group C 2/m (A 2/m)) and cubic M5X5 (cub) (space group Pm3m) superstructures. With the use of thermodynamic calculations it was shown that the proposed structural modification is equilibrium and should exist instead of the supposed high-temperature cubic phase Ti5O5 (cub). (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2016-12-13T04:51:48.24298-05:0
      DOI: 10.1002/pssc.201600113
       
  • Analysis of low-temperature data of Hall-effect measurements on p-type InP
           using a small-polaron theory
    • Authors: Yasutomo Kajikawa
      Abstract: The low-temperature data of Hall-effect measurements on p-type InP doped with Cd, Zn, or Mg reported by Benzaquen et al., which exhibit the characteristic of nearest-neighbor hoping conduction in an impurity band, have been analyzed within the two-band model including the valence band and the impurity band. It is shown that the temperature-dependent Hall-effect data can be well fitted by assuming the hopping drift mobility expressed as μib = μib0(T0/T)3/2exp(−T0/T) and the hopping Hall factor expressed as Aib = (kBT/J)exp(−T0H/T) on the basis of a small-polaron theory. Especially, Hall-effect sign anomaly observed at low temperature in Mg-doped InP is well reproduced by assuming a negative Hall effect for hoping conduction. The sign of the Hall coefficient for hoping conduction is discussed in connection with the overlap between the upper and the lower impurity Hubbard bands. (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2016-12-13T04:51:46.392718-05:
      DOI: 10.1002/pssc.201600217
       
  • Diodes based on semi-insulating CdTe crystals with Mo/MoOx contacts for X-
           and γ-ray detectors
    • Authors: O. Maslyanchuk; V. Kulchynsky, M. Solovan, V. Gnatyuk, C. Potiriadis, I. Kaissas, V. Brus
      Abstract: This paper reports on the possible applications of molybdenum oxide (Mo/MoOx) contacts in combination with semi-insulating CdTe crystals. The electrical contacts to p-type Cl-doped CdTe crystals were formed by the deposition of molybdenum oxide and pure molybdenum thin films by the DC reactive magnetron sputtering. Electrical properties of the prepared Mo-MoOx /γ-CdTe/MoOx -Mo surface-barrier structures were investigated at different temperatures. It is shown that the rapid growth of the reverse current with increasing bias voltage higher than 10 V is caused by the space-charge limited currents. Spectrometric properties of the Mo-MoOx /γ-CdTe/MoOx -Mo structures have been also analyzed. It is revealed that the developed heterojunction has shown promising characteristics for its practical application in X- and γ-ray radiation detector fabrication. (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2016-12-13T04:51:45.318645-05:
      DOI: 10.1002/pssc.201600232
       
  • Electron beam modification of vanadium dioxide oscillators
    • Authors: Maksim Belyaev; Andrey Velichko, Vadim Putrolaynen, Valentin Perminov, Alexander Pergament
      Abstract: The paper presents the results of a study of electron-beam modification (EBM) of VO2-switch I -V curve threshold parameters and the self-oscillation frequency of a circuit containing such a switching device. EBM in vacuum is reversible and the parameters are restored when exposed to air at pressure of 150 Pa. At EBM with a dose of 3 C/cm2, the voltages of switching-on (Vth) and off (Vh), as well as the OFF-state resistance Roff, decrease down to 50% of the initial values, and the oscillation frequency increases by 30% at a dose of 0.7 C/cm2. Features of physics of EBM of an oscillator are outlined considering the contribution of the metal and semiconductor phases of the switching channel. Controlled modification allows EBM forming of switches with preset parameters. Also, it might be used in artificial oscillatory neural networks for pattern recognition based on frequency shift keying. (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2016-12-13T04:51:44.015775-05:
      DOI: 10.1002/pssc.201600236
       
  • Role of oxygen vacancies and In-doping on the sensing performance of ZnO
           particles
    • Authors: F. Montes-Fonseca; S. F. Olive-Méndez, J. T. Holguín-Momaca, G. Alonso-Núñez, F. Paraguay-Delgado
      Abstract: Pure and In-doped ZnO particles with two morphologies: rods and platelets were synthesized using hydrothermal method and tested for gas sensing. The materials were characterized by X-ray diffraction, scanning electron microscopy and Raman spectroscopy. Platelets were synthesized with zinc acetate and potassium hydroxide in a ratio 1:3, while rods were obtained for a ratio1:8. As-synthesized particles do not exhibit any sensing response. The creation of oxygen vacancies, through thermal treatments under reducing atmosphere (Ar:H2), activate the sensing properties. The best sensitivity, upon exposure of CO and propane, was obtained on the In-doped platelets with large ±(0001) surface area. The value of the contact barrier between particles after the thermal treatment is 164 µeV. (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2016-11-30T06:30:07.745166-05:
      DOI: 10.1002/pssc.201600226
       
  • Similarities and differences between two different types of the
           thermoluminescence dosimeters belonging to the LiF family
    • Authors: A. M. Sadek; F. Khamis, George S. Polymeris, E. Carinou, G. Kitis
      Abstract: The kinetic parameters of the glow-peaks of Harshaw – LiF:Mg, Ti (TLD) and Poland – LiF:Mg,Ti (MTS) dosimeters were investigated at different dose levels using the computerized glow-curve deconvolution (CGCD) algorithm. The results showed that the glow-curve structure and the kinetic parameters of the MTS – 6 and the TLD dosimeter are identical. In addition, the glow-curve structure and the kinetic parameters of the MTS – N and MTS – 7 dosimeters. However, unusual low activation energy (∼1.67 eV) and frequency factor (∼1015 s–1) values were detected for peak 5 of MTS – N, and MTS – 7 at the 50 Gy dose-level. Moreover, unlike the activation energy and the frequency factor of peak 5 of the TLD dosimeters, the activation energy and the frequency factor of peak 5 of MTS – N and MTS – 7 are substantially dependent on the absorbed dose level. The results also showed that peak 2 of the same dosimeters has also unusual low activation energy and frequency factor values. However, these values showed high stability over the different dose levels. The explanations of these unusual behaviors of peak 5 were discussed and a correlation between peak 2 and peak 5 was pointed out. (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2016-11-30T06:30:06.464743-05:
      DOI: 10.1002/pssc.201600220
       
  • 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
       
  • 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
       
  • 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
       
  • 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
       
  • 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
       
  • 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
       
  • 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
       
  • 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
       
  • 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
       
  • Enhancement of the magneto-optical effects by bismuth in Heusler compound:
           A first-principle study
    • Authors: R. D. Eithiraj; K. R. Geethalakshmi
      Abstract: The structural, magnetic and optical properties of Rh2MnAl and Rh2MnBi Heusler alloys have been studied through the full potential linearized augmented plane wave (FP-LAPW) method. The exchange-correlation potential was treated within the generalized gradient approximation (GGA). The effect of the magnetic ordering, i.e. ferromagnetic (FM) and antiferromangnetic (AFM) along [001] and [111] crystal axis on the dielectric functions is revealed. Our calculations show that the Kerr rotation and elipticity is enhanced within 0-8 eV energy range by the substitution of Al by semimet al. (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
      PubDate: 2016-08-09T05:20:09.475292-05:
      DOI: 10.1002/pssc.201600089
       
 
 
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