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 Physica B: Condensed Matter       (Followers: 4) physica status solidi (a)       (Followers: 1) physica status solidi (b)       (Followers: 1) physica status solidi (c)       (Followers: 1) Physica Status Solidi - Rapid Research Letters Physical Communication Physical Review C       (Followers: 16) Physical Review Special Topics - Physics Education Research       (Followers: 5) Physical Review X       (Followers: 4) Physical Sciences Data       (Followers: 1) Physics - spotlighting exceptional research       (Followers: 1) Physics and Chemistry of Glasses - European Journal of Glass Science and Technology Part B       (Followers: 2) Physics and Chemistry of Liquids: An International Journal Physics and Chemistry of the Earth, Parts A/B/C       (Followers: 3) Physics Essays Physics in Medicine & Biology       (Followers: 7) Physics in Perspective       (Followers: 1) Physics International       (Followers: 2) Physics Letters A       (Followers: 9) Physics Letters B       (Followers: 2) Physics of Fluids       (Followers: 23) Physics of Life Reviews       (Followers: 1) Physics of Plasmas       (Followers: 6) Physics of the Dark Universe Physics of the Solid State       (Followers: 3) Physics of Wave Phenomena       (Followers: 1) Physics Procedia       (Followers: 1) Physics Reports       (Followers: 1) Physics Research International       (Followers: 1) Physics Today       (Followers: 15) Physics World       (Followers: 3) Physics-Uspekhi Physik in unserer Zeit Physik Journal Plasma Physics and Controlled Fusion       (Followers: 2) Plasma Physics Reports       (Followers: 2) Pramana       (Followers: 8) Preview Proceedings of the National Academy of Sciences       (Followers: 397) Proceedings of the National Academy of Sciences, India Section A       (Followers: 3) Progress in Materials Science       (Followers: 18) Progress in Planning       (Followers: 1) Progress of Theoretical and Experimental Physics Quantum Electronics       (Followers: 2) Quantum Measurements and Quantum Metrology Quarterly Journal of Mechanics and Applied Mathematics       (Followers: 3) Radiation Effects and Defects in Solids       (Followers: 1) Radiation Measurements       (Followers: 2) Radiation Physics and Chemistry       (Followers: 1) Radiation Protection Dosimetry       (Followers: 2) Radiation Research       (Followers: 2) Radio Science       (Followers: 2) Radiological Physics and Technology       (Followers: 1) Reflets de la physique Reports on Mathematical Physics Reports on Progress in Physics       (Followers: 2) Research & Reviews : Journal of Physics Research in Drama Education       (Followers: 8) Research Journal of Physics Results in Physics       (Followers: 1) Reviews in Mathematical Physics Reviews of Accelerator Science and Technology Reviews of Geophysics       (Followers: 18) Reviews of Modern Physics       (Followers: 16) Revista Colombiana de Física Revista Mexicana de Astronomía y Astrofísica Revista Mexicana de Física Revista mexicana de física E Rheologica Acta       (Followers: 3) Russian Journal of Mathematical Physics Russian Journal of Nondestructive Testing Russian Physics Journal Samuel Beckett Today/Aujourd'hui       (Followers: 2) Science and Technology of Nuclear Installations       (Followers: 1) Science China Physics, Mechanics and Astronomy       (Followers: 1) Science Foundation in China       (Followers: 2) Scientific Journal of Physical Science Scientific Reports       (Followers: 10) Selected Topics in Applied Earth Observations and Remote Sensing, IEEE Journal of       (Followers: 15) Sensor Letters       (Followers: 1) Sensors and Actuators A: Physical       (Followers: 20) Services Computing, IEEE Transactions on       (Followers: 3) Shock and Vibration       (Followers: 7) Shock Waves       (Followers: 4) Small       (Followers: 8) Software Engineering, IEEE Transactions on       (Followers: 21) Solid State Physics Solid-State Circuits Magazine, IEEE       (Followers: 1) South African Journal for Research in Sport, Physical Education and Recreation       (Followers: 3) Space Research Journal       (Followers: 2) Space Weather       (Followers: 3) Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy       (Followers: 7) Spectrochimica Acta Part B: Atomic Spectroscopy       (Followers: 4) Spectroscopy       (Followers: 3) Spectroscopy Letters: An International Journal for Rapid Communication       (Followers: 3) Sri Lankan Journal of Physics Strain       (Followers: 2) Strength of Materials       (Followers: 4) Strength, Fracture and Complexity       (Followers: 1) Structural Dynamics
 physica status solidi (c)    [3 followers]  Follow        Hybrid journal (It can contain Open Access articles)      ISSN (Print) 1862-6351 - ISSN (Online) 1610-1642      Published by John Wiley and Sons  [1603 journals]   [SJR: 0.397]   [H-I: 27]
• Multi‐frequency electron spin resonance study of inherent Si
dangling bond defects at the thermal (211)Si/SiO2 interface
• Authors: S. Iacovo; A. Stesmans
Pages: n/a - n/a
Abstract: Multifrequency low temperature electron spin resonance (ESR) studies were carried out to atomically assess inherent point defects at the thermal ‘higher index' (211)Si/SiO2 interface. This reveals, as dominant imperfections, Pb‐type centers (generic entity Si3≡Si•, the dot representing an unpaired sp3‐like hybrid) occurring in densities of ∼1 × 1013 cm–2 for oxidation temperatures ∼400 °C. On the basis of the pertinent ESR characteristics, the inherent basic defect is typified as the Pb0(211) variant, resembling closely the Pb0 center in standard (100)Si/SiO2. At the higher index (211)Si/SiO2 interface, these defects predominantly pertain to defected Si atoms located at (111)‐face terraces. Combination of angular and frequency (ν) dependent studies show the Pb0(211) peak‐to‐peak line width ΔBpp to be composed of a residual width (ν→0) of 2.2 ± 0.1 G, to which dipolar broadening contributes an essential part, and a substantial inhomogeneous broadening component due to g distribution, predominantly in g⊥, induced by non‐uniform interface strain –also similar to the Pb0(100) properties. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2014-08-08T04:40:13.233383-05:
DOI: 10.1002/pssc.201400071

• Sol–gel deposited phosphorus and boron doped thin silica films for
diffused n+p and n+pp+ structures
• Authors: Armel Duvalier Pene; Bouchaib Hartiti, Laurent Bitjoka, Phillippe Thevenin, Cesar Kapseu
Pages: n/a - n/a
Abstract: The realization of a silicon solar cell emitter is a critical and very important step in photovoltaic technology. Indeed, the surface concentration of boron (B) or phosphorus (P) and junction depth determines the photovoltaic conversion efficiency of silicon solar cells. Several techniques are used for the realization of emitters n+p and n+pp+ among which the vapor diffusion, ionic implantation and diffusion from solid sources are the most common. This work will be devoted to the realization of emitters made by diffusion of P or B from solid doping sources developed by the sol–gel method associated to spin coating on monocrystalline and polycrystalline silicon wafers. The doping solutions were prepared by sol–gel method using methyltriethoxysilane “MTEOS” or tetramethoxysilane “TEOS” and H4PO3 or H3BO3 as precursors. The n+ junction was realized by emulsion of phosphoric acid in isopropanol while the p+ junction was obtained by emulsion of boric acid H3BO3 in isopropanol or by diffusion of aluminium at high temperatures. Our samples were annealed at temperatures ranging from 850 to 1000 °C in a classical furnace under Nitrogen atmosphere. The four point technique has been used to study the electrical properties of n+p and n+pp++ structures. The results of measurements showed values of the sheet resistance Rs comparable to those of literature and confirm the diffusion of phosphorus and boron from liquid and solid sources prepared by sol–gel method. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2014-08-08T04:40:12.172213-05:
DOI: 10.1002/pssc.201400060

• Temperature dependent switching behaviour of nickel silicided undoped
silicon nanowire devices
• Authors: Jürgen Beister; Andre Wachowiak, André Heinzig, Jens Trommer, Thomas Mikolajick, Walter M. Weber
Pages: n/a - n/a
Abstract: In this work, we investigate the temperature dependence of electrical switching properties of back‐gated, undoped Si‐nanowire field‐effect transistors with Ni‐silicided source/drain contacts. A simple, phenomenological model illustrates the leading order temperature dependence of the source‐drain current, which originates predominantly from charge carrier injection by tunneling through the Schottky junction. Drain current versus gate voltage measurements have been performed for various temperatures and several drain voltages on a single nanowire device. The temperature dependence of the drain‐source current for specific gate and drain voltages is analysed within the framework of voltage dependent effective barrier heights. As a result, the temperature dependence of the tunnelling current is not only important for the sub‐threshold region, but also plays a significant role in the transistor “on‐state”. In addition, the effective barrier heights for electrons and holes tend towards the natural Schottky barriers of the NiSi2‐Si interface, if the applied external fields generate the case of flat band condition at the injection Schottky barrier, i.e. in the deep “off‐state” region. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2014-08-08T04:40:10.98697-05:0
DOI: 10.1002/pssc.201400055

• Band engineering and absorption spectra in compressively strained
Ge0.92Sn0.08/Ge (001) double quantum well for infrared photodetection
• Authors: N. Yahyaoui; N. Sfina, J.‐L. Lazzari, A. Bournel, M. Said
Pages: n/a - n/a
Abstract: We report a theoretical investigation of strained Ge1−xSnx/Ge (001)‐oriented quantum wells as a bulding block in active region of infrared photodetector. The electronic band parameters, gaps, discontinuities and effective masses for heterointerfaces between compressively strained Ge1−xSnx and relaxed Ge have beencomputed at room temperature. From this preliminary and mendatory work, we conclude that pseudomorphic Ge1−xSnx alloys become direct band gap semiconductors at a Sn‐fraction of 15.3%, e.g. a lattice mismatch as high as 2.3%. Due to achievable critical layer thickness and mainly solid solubility limit, a type‐I compressively strained Ge/Ge0.92Sn0.08/Ge (double) quantum well is studied by solving Schrödinger equation without and applied bias voltage. A strong absorption coefficient (> 1×104 cm−1) and a Stark shift of the direct transition between 2.01 μm and 2.25 μm at large external fields (40kV/cm) are attractive characteristics for the design of infrared photodetectors (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2014-08-08T04:40:09.615156-05:
DOI: 10.1002/pssc.201400054

• Electrically detected magnetic resonance study on defects in Si
pn‐junctions created by proton implantation
• Authors: Gernot Gruber; Stefan Kirnstoetter, Peter Hadley, Markus Koch, Thomas Aichinger, Holger Schulze, Werner Schustereder
Pages: n/a - n/a
Abstract: The present study focuses on electrically detected magnetic resonance (EDMR) investigations of proton implanted silicon. The samples were prepared on n‐type silicon wafers highly doped diffused boron (B) p‐region, forming a pn‐junction. A large additional n‐type doping was introduced by proton (H+) implantation. We compare samples with implantation doses up to 1015 H+/cm–2 and investigate the effects of anneals at 350 °C. We observe different types of defects in the differently prepared samples. One doublet with 118.5 G HF splitting and a g ‐value of 2.0095(4) is only observed in the samples implanted with the highest dose and is assigned to hydrogen. The structure of the other observed defects remains unidentified and can only tentatively be assigned to hydrogen. More extensive measurements would have to be performed to get a better picture. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2014-08-08T04:40:08.136114-05:
DOI: 10.1002/pssc.201400053

• High dose proton implantations into silicon: a combined EBIC, SRP and TEM
study
• Authors: Stefan Kirnstoetter; Martin Faccinelli, Christian Gspan, Werner Grogger, Moriz Jelinek, Werner Schustereder, Johannes G. Laven, Hans‐Joachim Schulze, Peter Hadley
Pages: n/a - n/a
Abstract: Proton (H+) implantations are used in power semiconductor devices to introduce recombination centers (Hazdra et al., Microelectron. J. 32(5), 449–456 (2001)) or to form hydrogen related donor complexes (Zohta et al., Jpn. J. Appl. Phys. 10, 532–533 (1991)). Proton implantations are also used in the 'smart cut' process to generate defects that can be used to cleave thin wafers (Romani and Evans, Nucl. Instrum. Methods Phys. Res. B 44, 313–317 (1990)). However, the implantation damage resulting from H+implantations is not completely understood. In this study, protons with energies from 400 keV up to 4 MeV and doses up to 1016 H+/cm² were implanted into highly ohmic boron doped m:Cz silicon (100). Electron Beam Induced Current (EBIC) measurements were performed to locally determine the minority charge carrier diffusion length. The diffusion length decreases with increasing implantation dose and incorporated damage. Spreading Resistance Profiling (SRP) measurements were performed to analyze the charge carrier concentration profiles for different annealing procedures. The electrical activation and growth of the defect complexes varies strongly with the annealing parameters. Transmission Electron Microscopy measurements were made to investigate the microscopic structures formed by the high dose implantation processes. Due to the high local damage density resulting from low energy and high dose H+ implants, platelet structures are formed. During high‐energy high‐dose H+implantations, the implanted hydrogen generates strain in the crystal lattice resulting in changes in the distances between atomic planes. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2014-08-08T04:40:06.968116-05:
DOI: 10.1002/pssc.201400051

• Depletion of superjunction power MOSFETs visualized by electron beam
induced current and voltage contrast measurements
• Authors: Stefan Kirnstoetter; Martin Faccinelli, Moriz Jelinek, Werner Schustereder, Johannes G. Laven, Hans‐Joachim Schulze, Peter Hadley
Pages: n/a - n/a
Abstract: Electron Beam Induced Current (EBIC) measurements were used to produce cross sectional images of superjunction power transistors. These images show how the depletion width expands under reverse bias. Superjunctions are alternating p‐ and n‐type doped vertical columns placed between drain and source in a power transistor (Deboy et al., in: Proc. IEDM, 983–685 (1998); Lorenz et al., in: Proc. PCIM Europe, 250–258 (1998)). These columns allow a higher substrate doping of the drift region, resulting in a lower on‐state resistance while still maintaining a high breakdown voltage. When the device is reverse biased, the space charge region of the superjunction should expand symmetrically due to the homogeneous doping (in the n and p region) until the complete device depletes. The depletion process was also visualized using voltage contrast (VC) measurements. Here the secondary electron signal was detected when the device was reverse biased. We show that EBIC and VC measurements can provide valuable input for process tuning and process simulations, enabling the use of smaller dimensions and higher doping levels
PubDate: 2014-08-08T04:30:06.467238-05:
DOI: 10.1002/pssc.201400050

• An EBIC and SRP study on thermal donors in proton implanted p‐type
magnetic Czochralski silicon
• Authors: Martin Faccinelli; Stefan Kirnstoetter, Werner Schustereder, Johannes G. Laven, Peter Hadley
Pages: n/a - n/a
Abstract: The concentration of defects in silicon can be changed by ion implantations and thermal annealing steps. Some of the defects incorporated during these processes form complexes which can act as donors or acceptors and their concentration can even overcome the initial doping concentration of the material, and hence, cause an inversion of the doping type. One way to introduce defects and also to catalyse the formation of defect complexes is by proton implantation. For our project, a high resistivity p‐type magnetic Czochralski (m:Cz) grown silicon wafer was implanted with 4 MeV protons at an implantation dose of 2 ×1014 cm–2. The wafer was broken into pieces and these pieces were annealed at different temperatures resulting in different concentrations of defect complexes. The defects were investigated in the proton implanted region and in the substrate region beyond the penetration depth of the protons (where only the heat treatment caused a change in the defect concentrations). The local doping type and the relative change of the minority carrier diffusion length were measured using Electron Beam Induced Current (EBIC). Furthermore, resistivity profiles were measured using Spreading Resistance Profiling (SRP). The results show several changes of the doping type, the minority carrier diffusion length and the resistivity profile. In addition to donor complexes already reported in the literature, the formation of additional high temperature donor complexes has been observed. The data shows that the presence of hydrogen in silicon has a far higher influence on the changes of the electrical properties of the material at annealing temperatures between 400 °C and 510 °C than at higher annealing temperatures. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2014-08-08T04:30:05.270823-05:
DOI: 10.1002/pssc.201400045

• Electron beam silicon purification
• Authors: Anatoly Kravtsov; Alexey Kravtsov
Pages: n/a - n/a
Abstract: Purification of heavily doped electronic grade silicon by evaporation of N‐type impurities with electron beam heating was investigated in process with a batch weight up to 50 kilos. Effective temperature of the melt, an indicative parameter suitable for purification process characterization was calculated and appeared to be stable for different load weight processes. Purified material was successfully approbated in standard CZ processes of three different companies. Each company used its standard process and obtained CZ monocrystals applicable for photovoltaic application. These facts enable process to be successfully scaled up to commercial volumes (150‐300 kg) and yield solar grade silicon. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2014-08-08T04:23:33.625363-05:
DOI: 10.1002/pssc.201400031

• Determination of the single crystal Ge Young’s modulus between room
temperature and melting temperature using the impulse excitation technique

• Authors: Akhilesh K. Swarnakar; Omer Van der Biest, Jan Van Humbeeck, Jan Vanhellemont
Pages: n/a - n/a
Abstract: In the present study, the vibrational properties of single crystal Ge samples are studied between room and melt‐ing temperature using the impulse excitation technique (IET). From the IET measurements, the temperature dependent Young's moduli Eijk of single crystal Ge are extracted in the (100), (110) and (111) crystallographic directions in inert atmosphere. The results show an anomalous softening of an elastic constant around 890 °C temperature during the measure‐ment. The Young's moduli values between 88 to 132 GPa are obtained close to the melting temperature, depending on the crystallographic direction. Empiric expressions are derived for the temperature dependence of E(100), E(110) and E(111). (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2014-08-08T04:20:05.544496-05:
DOI: 10.1002/pssc.201400011

• Photoluminescence properties of Ce3+ ions in Ce‐doped SiO1.5 thin
films containing Si nanocrystals
• Authors: J. Weimmerskirch‐Aubatin; M. Stoffel, X. Devaux, A. Bouché, M. Vergnat, H. Rinnert
Pages: n/a - n/a
Abstract: We investigate the luminescence properties of Ce3+ ions in Ce‐doped SiO1.5 thin films containing Si nanocrystals (Si‐ncs) by means of steady‐state photoluminescence (PL), time‐resolved PL and PL excitation spectroscopy. Strong Ce‐related blue luminescence is observed with the naked eye at room temperature. The Ce‐related lumines‐cence is found to ncrease with the Ce content in the films while simultaneously, the Si‐nc‐related luminescence decreases. Moreover, the decay time of the Si‐nc related luminescence decreases for increasing Ce concentrations thus suggesting a possible indirect excitation of the Ce3+ ions via Si‐ncs. However, PL excitation measurements show that Ce3+ ions are mainly directly excited with only a negligible influence of the Si‐ncs. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2014-07-25T05:10:14.445674-05:
DOI: 10.1002/pssc.201400042

• Tuning optical a‐SiC/a‐Si active filters by UV bias light in
the visible and infrared spectral ranges
• Authors: M. Vieira; M. A. Vieira, I. Rodrigues, V. Silva, P. Louro
Pages: n/a - n/a
Abstract: Visible range to telecom band spectral translation is accomplished using an amorphous SiC pi'n/pin wavelength selector under appropriate front and back optical light bias. Results show that background intensity works as selectors in the infrared region, shifting the sensor sensitivity. Low intensities select the near‐infrared range while high intensities select the visible part according to its wavelength. Here, the optical gain is very high in the infrared/red range, decreases in the green range, stays close to one in the blue region and strongly decreases in the near‐UV range. The transfer characteristics effects due to changes in steady state light intensity and wavelength backgrounds are presented. The relationship between the optical inputs and the output signal is established. A capacitive optoelectronic model is presented and tested using the experimental results. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2014-07-25T05:10:13.125023-05:
DOI: 10.1002/pssc.201400020

• Comparison between experimental and simulated strain profiles in Ge
channels with embedded source/drain stressors
• Authors: R. Bühler; G. Eneman, P. Favia, H. Bender, B. Vincent, A. Hikavyy, R. Loo, J. A. Martino, C. Claeys, E. Simoen, N. Collaert, A. Thean
Pages: n/a - n/a
Abstract: Two planar Ge‐based MOSFET structures were analysed for n‐ and p‐type transistors with tensile and compressive strain implemented in the channel direction using source/drain stressors. Strain profiles measured by nano‐beam diffraction (NBD) have been compared with Sentaurus process simulations. The TCAD simulations were tuned with the actual process using NBD measurements, resulting in a more realistic simulation and, therefore, a more reliable interpretation is now possible. dark‐field scanning transmission electron microscopy images added to the strain profiles returned interesting results about the Ge virtual substrate condition and how it disturbs the NBD readings due to the presence of extended defects in strain relaxed Ge buffer layers. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2014-07-25T05:10:12.035703-05:
DOI: 10.1002/pssc.201400021

• Mediation effect of sub‐monolayer carbon on interfacial mixing in Ge
growth on Si(100)
• Authors: Yuhki Itoh; Ryo Hayase, Shinji Hatakeyama, Tomoyuki Kawashima, Katsuyoshi Washio
Pages: n/a - n/a
Abstract: The mediation effect of carbon (C) on interfacial mixing in Ge growth was studied using C‐covered Si surface (Ge/C/Si) and C over thin Ge buffer layer (Ge/C/Ge/Si) systems. The samples were prepared by solid‐source molecular beam epitaxy system with electron beam gun for C sublimation and K‐cell for Ge evaporation. The interdiffusion at the interface and deterioration in crystallinity of Ge layer was evaluated by Raman spectroscopy and X‐ray diffraction, respectively. In the case of Ge/C/Si system, the interdiffusion of Si and Ge atoms was suppressed by more than 0.3 monolayer (ML)‐C depositions while crystallinity of Ge layer was deteriorates by the formation of Si‐C at the Si surface and the incorporation of C atoms in Ge layer. In the case of Ge/C/Ge/Si system, the crystallinity of Ge layer was maintained even at C coverage of a few MLs, however, the amount of C to suppress the Ge/Si interdiffusion was more than 3 ML. From the correlation between Ge crystallinity and surface roughness, Ge/C/Ge/Si structure is considered to be more effective to take advantage of C mediation. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2014-07-25T05:10:11.101235-05:
DOI: 10.1002/pssc.201400032

• Viability of the use of an a‐SiC:H multilayer device in a domestic
VLC application
• Authors: P. Louro; V. Silva, M. A. Vieira, M. Vieira
Pages: n/a - n/a
Abstract: In this paper the viability of an integrated wavelength optical filter and photodetector for visible light communication (VLC) is discussed. The proposed application uses indoor warm light lamps lighting accomplished by ultra‐bright light‐emitting diodes (LEDs) pulsed at frequencies higher than the ones perceived by the human eye. The system was analyzed at two different wavelengths in the visible spectrum (430 nm and 626 nm) with variable optical intensities. The signals were transmitted into free space and measured using a multilayered photodetector based on a‐SiC:H/a‐Si:H. The detector works as an optical filter with controlled wavelength sensitivity through the use of optical bias. The output photocurrent was measured for different optical intensities of the transmitted optical signal and the extent of each signal was tested. The influence of environmental fluorescent lighting was also analysed in order to test the strength of the system. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2014-07-25T05:10:10.256382-05:
DOI: 10.1002/pssc.201400035

• Enhancement of IR photoluminescence of β‐FeSi2 nanocrystals by
Cu‐doping and study of its mechanism
• Authors: Yoshihito Maeda; Takahide Tatsumi, Yuki Kawakubo, Yuya Noguchi, Hiroyuki Kobayashi, Kazumasa Narumi, Seiji Sakai
Pages: n/a - n/a
Abstract: We have investigated the IR photoluminescence (PL) behavior of Cu‐doped β‐FeSi2 nanocrystals (β‐NCs) embedded in Si layers. The diffusion rate of Cu atom was controlled by annealing. The most appropriate condition brought the largest intensities of both the intrinsic A band emission at 0.803 eV by 214% and the acceptor related C band emission at ∼0.75 eV by 582% in comparison with those of non‐doped β‐NCs. Rutherford backscattering spectrometry (RBS) revealed increase of Cu atoms in the Si layer with β‐NCs with increasing the anneal duration. The C band enhancement surely is originated from increase of a density of state at acceptor levels relating to increase of Cu in β‐lattice. Photocarrier injection PL measurements (PCI‐PL) reveal that the enhancement of the A band emission may be attributed to a controlled migration process of holes with a repeated trap process due to Cu‐doping into the Si phase. This dynamic condition leads to an increase of valence band offset at the β‐NCs/Si heterointerfaces where the migration of holes from the β‐NCs to Si is prevented, so that a radiative recombination rate can be enhanced. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2014-07-25T05:10:09.416628-05:
DOI: 10.1002/pssc.201400039

• Raman analysis of gold catalyst vapor liquid solid germanium nanowires
• Authors: M. Israel; A. Moreac, R. Rogel, J. P. Landesman, L. Pichon
Pages: n/a - n/a
Abstract: Germanium nanowires (GeNWs) were synthesized in a low pressure chemical vapor deposition reactor (LPCVD) using a vapor‐liquid‐solid process (VLS). In this work, the focus is put on the characterization of these GeNWs using scanning electron microscopy (SEM) combined with Raman spectroscopy. In particular, NWs with conical shape grown at a moderate temperature (320 °C) were investigated in terms of the intensity measured for the Ge‐related Raman line. The two main observations, discussed in this paper, are the anomalous magnitude of this line, as compared to measurements under the same conditions on a Ge(100) substrate, and the oscillations observed when the Raman line intensity is measured while scanning the laser beam along the axis of the conical shaped NWs, from the tip to the bottom. These effects are discussed involving the fact that optical modes appear in such NWs (both for the incident and Raman scattered light) when conditions on the diameter, the laser excitation wavelength, and substrate (on which the NWs are transferred after growth) are fulfilled. Taking into account these specific optical modes, the effects observed can be explained. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2014-07-25T05:10:08.278128-05:
DOI: 10.1002/pssc.201400041

• Electronic structureof amorphous ZnO films
• Authors: Dieter Schmeißer; Jörg Haeberle, Pedro Barquinha, Diana Gaspar, Luís Pereira, Rodrigo Martins, Elvira Fortunato
Pages: n/a - n/a
Abstract: We use resonant photoemission spectroscopy (resPES) to study the electronic properties of amorphous ZnO (a‐ZnO) layers. We report on the core levels, the valence band (VB) PES data, and the X‐ray absorption (XAS) data which we use for the conduction band (CB) density of states. From these results we are able to derive the partial density of states (pDOS) of O2p and Zn4s4p states in the VB and CB, respectively as well as a band scheme. At the O1s resonance we observe a band of localized defect states which is located between the Fermi energy and the CBM. At the Zn2p edge the XAS data indicate that localized Zn4s4p states are involved in the DOS starting already at the Fermi energy. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2014-07-24T06:10:08.545943-05:
DOI: 10.1002/pssc.201400010

• High temperature electrical conductivity in hydrothermally grown ZnO
• Authors: K. Lott; T. Nirk, L. Türn, S. Shinkarenko, A. Öpik, E. Kortunova, P. Shvanskiy, E. Gorokhova, A. Vishnjakov
Pages: n/a - n/a
Abstract: Results of measurements of high temperature electrical conductivity (HTEC) in undoped hydrothermally grown ZnO single crystal are presented. HTEC measurements were made under the Zn component vapor pressure (up to 1 atm) and in the temperature range from 873 K to 1273 K. Reliable thermodynamic equilibrium in the ZnO crystal for HTEC measurements of isotherms and isobars was obtained at the temperatures higher than 873 K. Surprisingly slow chemical diffusion prolonged the high temperature measurement cycles continuously for several weeks. In our experiments the absolute value of HTEC in undoped hydrothermally grown ZnO was several orders of magnitude higher than HTEC in undoped ZnS. Slopes of HTEC isotherms varied with component vapor pressure and changed in the range from 0.2 to 0.4. For HTEC isobar in the temperature range from 1173 K to 1273 K it was found activation energy value 0.3‐0.4 eV at zinc vapour pressure 0.092 atm. Defect model for explanation of this high temperature experiment is discussed in connection with impurities. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2014-07-24T06:10:07.34355-05:0
DOI: 10.1002/pssc.201400009

• Cover Picture: Phys. Status Solidi C 7–8/2014
• Pages: n/a - n/a
Abstract: In their Invited Article on pp. 1267–1272, Klein et al. report on the realization of monolithic, i.e. fully epitaxial ZnSe‐based microcavities with 1λ ‐ to 3λ ‐cavities for the investigation of strong coupling phenomena. The lattice matched distributed Bragg reflectors consist of quaternary ZnMgSSe layers as the high‐index material and a MgS/ZnCdSe superlattice as the low‐index material. This microcavity design allows for the use of high‐quality ZnSe quantum wells. Strong coupling was achieved with a vacuum Rabi splitting of 19 meV for the 1λ ‐cavity (at 70 K) and of 40 meV for the 3λ ‐cavity (at 7 K). Effectively the Rabi splitting can be chosen by the sample design. Q ‐factors up to 6500 are found, exceeding state‐of‐the‐art optical quality in II–VI microcavities. Microstructures such as micropillars, waveguides, ring resonators, and molecule chains were fabricated using focused ion‐beam etching. Discrete optical modes in micropillars were observed for both cavity lengths confirming three‐dimensional optical confinement and low sidewall damage, even for small pillar radii. In summary, such microcavities offer new perspectives for the investigation of exciton‐polariton fluids: stability at elevated temperature, large Rabi splitting, comparable with optical phonon frequency, together with full control over in‐plane confinement.
PubDate: 2014-07-10T12:30:56.086763-05:
DOI: 10.1002/pssc.201470053

• Issue Information: Phys. Status Solidi C 7–8/2014
• Pages: n/a - n/a
PubDate: 2014-07-10T12:30:50.98935-05:0
DOI: 10.1002/pssc.201470054

• Effect of iron on the dielectric properties of silicate glasses prepared
by sol‐gel
• Authors: S. A. Salehizadeh; M. P. F. Graça, M. A. Valente
Pages: n/a - n/a
Abstract: The sol‐gel method is a very flexible route for producing sieving matrix such as SiO2 with pore radii in nanoscale region to embed oxide particles like Fe2O3. In this work, iron oxide nanoparticles embedded in a SiO2 glassy matrix prepared by the sol‐gel method have been investigated as a function of Fe/Si ratio. Different composition of dried gels with 1, 2, 10 and 20 mol% of Fe2O3 in the SiO2 matrix were heat‐treated (HT) in air, at temperatures from 400 ºC up to 1400 °C. The structure and morphology of the obtained glasses and glass‐ceramics were studied by X‐ray powder diffraction (XRD), Raman spectroscopy and scanning electron microscopy (SEM). Impedance spectroscopy measurements and magnetic characterization were performed as function of temperature and the results are related with the microstructure. The X‐ray diffraction patterns showed that increasing the amount of Fe2O3 oxide promotes the formation of crystalline phases, in particular silicate phases. The increase of the heat‐treatment temperature has a similar behavior. The electrical and dielectric properties were related with these structural modifications and with the sample morphology. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2014-05-26T06:10:21.942599-05:
DOI: 10.1002/pssc.201400015

• Galvanomagnetic and thermoelectric properties of Te doped
single‐crystal bismuth wires
• Authors: A. A. Nikolaeva; L. A. Konopko, T. E. Huber, A. K. Tsurkan, D. F. Meglei, D. Yu. Matveev
Pages: n/a - n/a
Abstract: We present a study of the electrical, transport and thermoelectric properties of Te‐ doped single‐ crystal Bi wires in a glass capillary. The tellurium concentration ranged up to the solubility limit. Measurements of resistance and thermopower were carried out over a wide range of temperatures (2–300 K) and magnetic fields (0–14 T). The shift of the Fermi level by Te doping of Bi wires is calculated from the Shubnikov de Haas oscillations. The effect of quantum confinement and the wire boundary scattering at low temperatures is significantly suppressed for Te‐ doped samples, which are consistent with general theoretical considerations. An anomaly of the thermopower in the form of sign inversion from negative to positive was detected at an electron concentration of ∼1×1020 cm‐3. The observed anomaly disappears after further doping. The effect is interpreted in terms of the manifestation of the features in thermopower at an electronic topological transition (2 1/2 Lifshitz impurity phase transition). (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2014-05-14T05:10:21.673676-05:
DOI: 10.1002/pssc.201300192

• Thermoelectric properties of Bi2Te3 microwires
• Authors: L. A. Konopko; A. A. Nikolaeva, T. E. Huber, D. F. Meglei
Pages: n/a - n/a
Abstract: We present here a study of electrical and thermoelectric properties of n ‐ and p ‐Bi2Te3 microwires (n ‐type Bi2Te2Se; p ‐type Bi0.5Sb1.5Te3) with different diameters (d =10–20 µm). Cylindrical Bi2Te3 crystals with glass coating were prepared by the liquid phase casting in a glass capillary. The X‐ray studies have shown that the microwire core is in general polycrystal consisting of big disoriented single crystal blocks. Measurements of resistance and thermopower were carried out over a wide range of temperatures (4.2–300 K) and magnetic fields (0–14 T). At 300 K for samples of n ‐ and p ‐type the thermopower S and power factor P.f. = S2σ were (100–140) µV/K, 1.6×10‐3 W/(K2m) and (150–300) µV/K, 4.5×10‐3 W/(K2m), respectively. Magnetic field dependences of Power factor were measured at various temperatures (T =35, 100, 270 K) and different magnetic field orientations. A broad maximum is the dominant feature of the magnetic field dependence of power factor for p‐ type samples, while power factor decreases for n‐ type samples. We have obtained maximum power factor P.f. =6.8×10‐3 W/(K2m) for p ‐type sample at longitudinal magnetic field B =3 T at T =100 K. Shubnikov de Haas oscillations with equal periods ΔB =0.038 T‐1 both in longitudinal and transverse magnetic fields for carriers with mc = 0.15m0 in p ‐type Bi2Te3 microwire were observed. These oscillations could arise from the topological surface states. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2014-05-14T05:10:20.667512-05:
DOI: 10.1002/pssc.201300202

• Contents: Phys. Status Solidi C 7–8/2014
• Pages: 1155 - 1160
PubDate: 2014-07-10T12:30:55.758174-05:
DOI: 10.1002/pssc.201470055

• II–VI Compounds and Related Materials
• Authors: Shizuo Fujita; Masakazu Kobayashi, Takashi Yasuda, Kunio Ichino
Pages: 1161 - 1165
Abstract: The present issue of physica status solidi contains papers presented at the 16th International Conference on II–VI Compounds and Related Materials (II–VI 2013) held in Nagahama, Japan, September 9–13, 2013. The papers were selected after peer reviewing and revision processes of original manuscripts. This conference is the continuation of a successful series of biennial conferences which started in Durham (UK) in 1983. The last three conferences were held in Jeju, Korea (2007), Saint Petersburg, Russia (2009), and Mayan Riviera, Mexico (2011). These conferences have contributed to review and stimulate the progress in basic and applied research on II–VI compounds. More recently, the research targets of II–VI compounds have extended or merged to those of other related materials such as a variety of oxide and chalcopyrite semiconductors, and in this view this conference covered “II–VI Compounds and Related Materials”. This conference was attended by 143 participants registered for technical sessions from 15 countries all over the world. During the course of the conference, 8 invited talks and 122 contributed papers were given as oral and poster presentation. “II–VI 2013” highlighted fundamental physics in optics and spintronics, new materials and structures contributing to emerging devices, optical devices from infrared to UV as well as X‐ and gamma‐ray regions, transparent electronic devices, and new functions in semiconductors. We would like to thank all the participants and sponsoring organizations for contributing to the success of the conference and acknowledge the diligent work of the committee members and the referees of manuscripts. A special appreciation is due to financial supporters recognizing the importance of fundamental fields in science and technology covered in this conference. The 17th conference will be organized by Dr. Christophe Testelin and held in Paris, France, 2015.
PubDate: 2014-07-10T12:30:51.72728-05:0
DOI: 10.1002/pssc.201470056

• Growth of large diameter ZnTe single crystals by the double crucible
liquid encapsulated pulling method
• Authors: Toshiaki Asahi; Kenji Sato
Pages: 1167 - 1173
Abstract: In our work, large diameter ZnTe single crystals were grown by various melt growth methods. By a liquid encapsulated vertical gradient freezing method, crystals with large grains and low dislocation density were obtained. By a liquid encapsulated Kyropoulos method, 80 mm diameter crystals were successfully grown from ZnTe seed crystals. However, crystals grown by the both methods had large strain and cracks owing to difference in coefficient of thermal expansion between an encapsulant and ZnTe. Therefore, a new crystal growth method was developed. Two crucibles were used in the new method. It was named double crucible liquid encapsulated pulling method. Crystals up to 100 mm in diameter and 40 mm in length were reproducibly obtained. Both and crystals were successfully grown. The etch pit density of the grown crystal was lower than 10,000 cm–2 and any large strain or cracks were not observed. In order to reduce Te inclusions, wafer annealing was examined. Most Te inclusions were eliminated with suitable Zn pressure and annealing temperature. Optical transparency of the ZnTe crystal increased after annealing. This is because scatter of the incident light by Te inclusions decreased. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2014-04-04T02:20:11.527624-05:
DOI: 10.1002/pssc.201300704

• Characterization of CdMnTe crystal grown with vertical Bridgman method
under Te‐rich conditions
• Authors: Jijun Zhang; Linjun Wang, Jiahua Min, Jian Huang, Xiaoyan Liang, Ke Tang, Ping Shen, Min Shen, Wei Liang, Nansen Huang, Yiben Xia
Pages: 1174 - 1177
Abstract: In this study, the Indium (In) doped Cd1–xMnx Te (xMn=0.1, CdMnTe) crystals with excess Te in the amount of 0 and 1.2 at% were grown by the Bridgman method. The segregation coefficient of In dopants distributions in the CdMnTe crystals with and without excess Te were determined to be 0.08 and 0.11, respectively. The IR transmission microscopy shown that the size of Te inclusions in CdMnTe crystal with excess Te increased to 5–13 μm with the concentrations of (2–3)×105 cm–3. The PL spectra indicated the formation of Te antisite donor and the compensation of Cd vacancies by Te antisites. The Current‐Voltage measurements were performed and the resistivity of the CdMnTe crystal with excess Te was in the range of 108–109 Ω·cm, increased by one order as compared to the crystal without excess Te. Under the radiation of 59.5 keV 241Am, The CdMnTe planar detectors fabricated from the crystal with excess Te revealed the energy resolution of 8.4%, however, no energy response is resolved in the CdMnTe detectors without excess Te. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2014-04-07T06:20:14.544211-05:
DOI: 10.1002/pssc.201300575

• Deposition of polycrystalline Cd1‐xZnx Te films on ZnTe/graphite and
graphite substrates by close‐spaced sublimation
• Authors: Tamotsu Okamoto; Sho Akiba, Kohei Takahashi, Satsuki Nagatsuka, Yohei Kanda, Satoshi Tokuda, Hiroyuki Kishihara, Toshiyuki Sato
Pages: 1178 - 1181
Abstract: The effects of a ZnTe layer on the deposition of a Cd1‐xZnxTe (CZT) layer in the initial stage of the close‐spaced sublimation (CSS) deposition were investigated. The deposition rate was almost constant in the initial stage of the CdTe deposition on the ZnTe/graphite substrates. However, the deposition rate within 1 minute was lower than that after 1 minute in the CdTe deposition on graphite substrates. This result suggests that nucleation of CdTe directly deposited on graphite substrate is difficult when compared to that with a ZnTe layer. Furthermore, the effects of CdCl2 and ZnTe additions to the CdTe sources in the CSS deposition were also investigated. Both the grain size and the intensity of donor‐acceptor pair (DAP) emission in photoluminescence (PL) spectra were decreased by the effect of CdCl2 addition. Zn content in CZT films was controlled by the ZnTe ratio in the CdTe/ZnTe powder sources. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2014-03-24T04:10:07.857168-05:
DOI: 10.1002/pssc.201300581

• MBE growth and characterization of ZnTe epilayers on m‐plane
sapphire substrates
• Authors: Taizo Nakasu; Wei‐Che Sun, Sotaro Yamashita, Takayuki Aiba, Kosuke Taguri, Masakazu Kobayashi, Toshiaki Asahi, Hiroyoshi Togo
Pages: 1182 - 1185
Abstract: ZnTe epilayers were grown on transparent (10‐10) oriented (m ‐plane) sapphire substrates by molecular beam epitaxy (MBE). Pole figure imaging was used to study the domain distribution within the layer. (211)‐oriented ZnTe domains were formed on m ‐plane sapphire. The presence of only one kind of (211) ZnTe domain formed on the 2°‐tilted m ‐plane sapphire substrates was confirmed. Thus, single domain (211) ZnTe epilayers can be grown on the m ‐plane sapphire using MBE. Although differences in the crystal structure and lattice mismatch are large, precise control of the substrate surface lattice arrangement result in the formation of high‐quality epitaxial layers. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2014-03-24T04:20:06.546005-05:
DOI: 10.1002/pssc.201300582

• Structural characterization of AgGaTe2 layers grown on a‐ and
c‐sapphire substrates by a closed space sublimation method
• Authors: Aya Uruno; Ayaka Usui, Masakazu Kobayashi
Pages: 1186 - 1189
Abstract: AgGaTe2 layers were grown on a‐ and c‐plane sapphire substrates by a closed space sublimation method with varying the source temperature. Grown films were evaluated by θ ‐2θ and pole figure measurements of X‐ray diffraction. AgGaTe2 layers were grown to have strong preference for the (103) orientation. However, it was cleared the Ag5Te3 was formed along with the AgGaTe2 when the layer was grown on c‐plane sapphire. The orientation of the film was analyzed by using the pole figure, and resulted in AgGaTe2 without Ag5Te3 layers could be grown on a‐plane sapphire. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2014-03-24T04:20:05.447272-05:
DOI: 10.1002/pssc.201300583

• Growth of CuGaTe2 based compounds by a closed space sublimation method
• Authors: Ayaka Usui; Aya Uruno, Masakazu Kobayashi
Pages: 1190 - 1193
Abstract: Chalcopyrite I‐III‐VI2 compounds are considered as novel potential materials for solar cells. Among the variety of those compounds, CuGaTe2 and AgAlTe2 films were grown by a closed space sublimation method. Crystallinity and stoichiometry of grown films were evaluated by X‐ray diffraction measurements. When CuGaTe2 powder source was used to grow CuGaTe2 films at around 840 °C of the source temperature, stoichiometric CuGaTe2could not be formed. X‐ray diffraction measurements revealed that the deposited material was Cu‐Ga compound. The desorption of Te was compensated by adding elemental Te in the source material. These stoichiometric CuGaTe2 films were achieved when the volume of additional Te was around twice weight of CuGaTe2. On the other hand, growth of AgAlTe2 films could be achieved when the source temperature was 800 °C, and no additional Te was introduced in the source. From X‐ray diffraction measurements, it was found that these two compounds films had strong preference for the (112) orientation on the quartz substrate. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2014-03-24T04:20:04.128656-05:
DOI: 10.1002/pssc.201300584

• Comparison in internal strain sensitivity between polariscopy and Raman
scattering spectroscopy in a (110)‐oriented ZnTe single crystal
• Authors: Hideo Takeuchi
Pages: 1194 - 1197
Abstract: We present the experimental fact that, in a (110)‐oriented ZnTe single crystal, polariscopy is highly sensitive to the internal strain, comparing with Raman scattering spectroscopy. We utilized X‐ray topography and X‐ray diffraction analysis to thoroughly investigate the crystal structure that is intimately associated with the internal strain. The two X‐ray structure analyses clarified that the misalignment from the [110] direction is formed in some regions. We obtained the following main result: The polariscopic analysis detects the internal strain formed by the misalignment, whereas the Raman scattering measurement is insensitive to the internal strain. We, therefore, conclude that polariscopy has the strain‐detection sensitivity higher than the Raman scattering spectroscopy. We have confirmed that the polariscopic analysis can detect the internal strain less than 0.5% in the ZnTe crystal. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2014-03-25T02:20:08.070143-05:
DOI: 10.1002/pssc.201300608

• Effect of hydrogen partial pressure on growth of Cu2ZnSnS4 films
sulfurized using diethyl sulfide
• Authors: Masahiro Tahashi; Ryota Yamada, Hiroaki Ito, Kenji Yoshino, Makoto Takahashi, Hideo Goto
Pages: 1198 - 1201
Abstract: Polycrystalline Cu2ZnSnS4 films were prepared by thermal treatment of stacked Sn/Zn/Cu metallic precursors in the presence of diethyl sulfide, which is a less hazardous sulfur source than H2S gas. The effect of the hydrogen partial pressure on the crystal phases present in the films was investigated. It was found that sulfur and carbon atoms play an important role in film growth. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2014-03-25T02:20:07.131208-05:
DOI: 10.1002/pssc.201300609

• The effect of substrate temperature upon the compositions of Mg and Se in
Zn1‐xMgx Sey Te1‐y layer grown by MOVPE
• Authors: M. Nishio; K. Saito, R. Ito, K. Tanaka, K. Urata, Y. Nakamura, T. Tanaka, Q. X. Guo
Pages: 1202 - 1205
Abstract: The growth of Zn1‐xMgx Sey Te1‐y layers was performed on (100) ZnTe substrate by metalorganic vapour phase epitaxy using dimethylzinc, bis‐methylcyclopentadienyl‐magnesium, diethyltelluride and diethylselenide. The effects of substrate temperature upon the compositions of Mg and Se have been investigated. The Mg composition in Zn1‐xMgx Sey Te1‐y layer is significantly enhanced at low substrate temperature. Although the Se composition decreases with decreasing the substrate temperature, Zn1‐xMgx Sey Te1‐y layer with a relatively high Se composition of 0.3 is obtainable at a low substrate temperature as low as 380 ºC. For all the layers, a two‐mode behaviour with ZnTe‐ and MgTe‐like longitudinal optical phonon modes is confirmed by Raman scattering. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2014-03-25T02:20:06.344132-05:
DOI: 10.1002/pssc.201300610

• Growth of metastable ZB CrSe
• Authors: Richard T. Moug; Kevin A. Prior
Pages: 1206 - 1209
Abstract: In this paper we present, for the first time, evidence of the metastable compound CrSe grown by MBE in the ZB crystal structure. Using a compound 6N CdSe source and 6N purity Cr we demonstrate the material can be grown with a growth rate of 0.06 Ås–1 in layers up to approximately 20 nm thick. Secondary ion mass spectrometry (SIMS), X‐ray reflection (XRR), RHEED and optical microscopy were used to examine the composition and morphology. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2014-03-31T02:10:14.811961-05:
DOI: 10.1002/pssc.201300622

• Direct growth of ZnSe and CdSe on (100) InAs substrates
• Authors: Silvia Butera; Richard T. Moug, Peter Vines, Gerald S. Buller, Kevin A. Prior
Pages: 1210 - 1212
Abstract: ZnSe and CdSe layers have been grown on InAs substrates using molecular beam epitaxy (MBE) without the need for a III‐V and II‐VI dual chamber system. This paper reports on the optimisation of a chemical oxide removal process using sulphur passivation. This removes the need for conventional in vacuo oxide removal under As overpressure that is used to prevent the formation of high densities of In droplets. X‐ray and photoluminescence characterisation of the samples confirms single crystal growth. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2014-03-31T02:10:15.731986-05:
DOI: 10.1002/pssc.201300624

• Wide‐range visible luminescence of ZnCdSe/BeZnTe type‐II
superlattices grown on InP substrates
• Authors: Keisuke Murakami; Ichirou Nomura, Toshiki Kobayashi, Tomohiro Shiraishi, Shingo Takamatsu, Katsumi Kishino
Pages: 1213 - 1217
Abstract: The photoluminescence (PL) characteristics of ZnCdSe/BeZnTe type‐II superlattices (SLs) with various thickness combinations of ZnCdSe and BeZnTe layers were investigated at room temperature. High PL peak intensities that were comparable to those of other direct‐bandgap materials, such as BeZnSeTe, were obtained. The PL peak wavelength was widely controlled from 508 to 739 nm by changing the layer thickness combination (ZnCdSe/BeZnTe) from 1 monolayer (ML)/5 ML to 6 ML/5 ML. The peak wavelengths were evaluated by comparison with theoretical values. Three‐primary‐color luminescence with PL peaks of 506, 530, and 617 nm was demonstrated for the SL sample with three types of monolithically stacked SLs with different layer thickness combinations (i.e., 1 ML/5 ML, 2 ML/5 ML, and 5 ML/5 ML). (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2014-03-31T02:10:17.462463-05:
DOI: 10.1002/pssc.201300634

• Fabrication of ZnO/ZnTe heterojunction by using a room temperature direct
bonding technology
• Authors: Hajime Akiyama; Katsuhiko Saito, Tooru Tanaka, Mitsuhiro Nishio, Qixin Guo
Pages: 1218 - 1220
Abstract: The ZnO/ZnTe heterojunction was fabricated by using a room temperature direct bonding (RTDB) technology. Satisfactory rectification properties were confirmed, and the forward voltage drop VF was observed to be 2.3 V. The results indicate that RTDB technology is effective for fabricating ZnO/ZnTe heterojunction. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2014-03-31T02:10:21.58826-05:0
DOI: 10.1002/pssc.201300642

• Post‐growth annealing treatment of ZnO nanowires with arsenic and
phosphorus sources
• Authors: Emir Zehani; Said Hassani, Alain Lusson, François Jomard, Pierre Galtier, Vincent Sallet
Pages: 1221 - 1224
Abstract: An attempt to incorporate dopants in ZnO nanowires grown using metal organic chemical vapour deposition (MOCVD) on sapphire substrates is presented. Diffusion of phosphorus (P) and arsenic (As) into the ZnO nanowires and ZnO substrates were carried out in vacuum sealed ampoules at temperatures ranging from 580 to 800 °C. Doping sources were Zn3P2 or Zn3sA2. The evolution of the wires morphology shows a dramatic degradation above 620–650 °C. SIMS analysis reveals the transport of P and As onto the sample surface. Mass profiling shows that the dopants do not diffuse significantly into bulk ZnO. This is confirmed by both Raman scattering and low temperature photoluminescence (PL) where no optical signatures related to the incorporation of P or As are observed. Surprisingly, PL experiments performed on nanowires processed at a temperature where the effect of annealing on the morphology start to be visible show an improved quality, and features commonly observables in high quality bulk samples. These results suggest that defects localised at the surface of the ZnO nanowires could be removed using post‐annealing in Zn rich atmosphere. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2014-04-04T02:20:14.534998-05:
DOI: 10.1002/pssc.201300648

• Ultrasonic‐assisted mist chemical vapor deposition of II‐oxide
and related oxide compounds
• Authors: Shizuo Fujita; Kentaro Kaneko, Takumi Ikenoue, Toshiyuki Kawaharamura, Mamoru Furuta
Pages: 1225 - 1228
Abstract: Basic concepts of ultrasonic‐assisted mist chemical vapor deposition (CVD), and its applications to the fabrication of II‐oxide and related oxide films are described. Fairly good thin film properties and device performance, compared to those achieved by conventional vacuum‐based processes, encourage the mist CVD as a simple, inexpensive, energy‐saving and non‐vacuum process, opening new and wide application of oxide materials for novel devices supporting the future environment. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2014-04-04T02:20:12.627702-05:
DOI: 10.1002/pssc.201300655

• First‐principles theoretical study of optical properties of
oxygen‐doped II‐VI semiconductors
• Authors: Masato Ishikawa; Takashi Nakayama
Pages: 1229 - 1232
Abstract: Doping properties of oxygen into zinc‐family II‐VI semiconductors were studied by the first‐principles calculation. We found that a large band‐gap reduction occurs for ZnS and ZnSe, while there is little reduction and appears a deep level of oxygen in the band gap for ZnTe. Such difference was shown to reflect the order of energy positions of host cation (Zn) 4s‐orbital and oxygen (O) 3s‐orbital states. We also calculated photoabsorption spectra, ε2(ω), and found that oxygen‐related transitions are strong in case of ZnTe due to localized nature of deep level, while transitions are embedded in the band‐to‐band adsorption in cases of ZnS and ZnSe due to strong hybridization of unoccupied states of O and II‐VI semiconductors. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2014-03-24T04:10:11.62344-05:0
DOI: 10.1002/pssc.201300557

• Growth of zinc oxide on pyrolytic graphite sheet by electrochemical and
mist chemical vapor depositions
• Authors: Shunsuke Kake; Kazuyuki Uno, Ikuhiro Furotani, Harutaka Makabe, Yuichiro Yamasaki, Ichiro Tanaka
Pages: 1233 - 1236
Abstract: Growth of zinc oxide (ZnO) on pyrolytic graphite sheet (PGS) by electrochemical deposition (ECD) and mist chemical vapor deposition (CVD) was investigated in the viewpoint of crystal orientations. We examined the fullwidth at half‐maximum (FWHM) of X‐ray rocking curve profiles of graphite 0002 and ZnO 0002 diffractions for the investigations. In the case of ECD, thermal annealing at 400, 800, and 1000 °C for PGS before the growth reduced the FWHM value of the grown ZnO. On the other hand, in the case of mist CVD, the growth process and an etching process which may flatten the surface roughness simultaneously occurred. As a result, the FWHM values of the grown ZnO and the PGS were almost the same. These results indicate that each ZnO grain was grown on each graphite grain along with a same c‐orientation direction. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2014-04-07T06:20:08.453572-05:
DOI: 10.1002/pssc.201300733

• Fabrication and characterization of Cu2O, ZnO and ITO thin films toward
oxide thin film solar cell by mist chemical vapor deposition method
• Authors: Takumi Ikenoue; Shin‐ichi Sakamoto, Yoshitaka Inui
Pages: 1237 - 1239
Abstract: N‐type zinc oxide (ZnO) and p‐type cuprous oxide (Cu2O) thin films were fabricated by an ultrasonic spray‐assisted mist chemical vapor deposition (mist CVD) method. The films of transparent conductive gallium‐doped ZnO (ZnO:Ga) and indium tin oxide (ITO) were also formed by the same technique. ZnO thin films have showed n‐type conductivity with carrier concentration of 3.6 × 1019 cm–3 and mobility of 8.6 cm2/V·s. Cu2O thin films showed p‐type conductivity whose carrier density and mobility were 3.3 × 1015 cm–3 and 0.20 cm2/V·s, respectively. ZnO:Ga and ITO thin films have high transmittance over 85% in visible region and low resistivity values of 2.3 × 10–3 and 1.4 × 10–4 Ω·cm, respectively. These properties are suitable for transparent electrodes of solar cells. The results encourage the successive fabrication by the same process technique of solar cell structure, that is, the multilayer structure of ITO (or conductive ZnO), n‐ZnO, and p‐Cu2O films on a glass substrate. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2014-03-31T02:10:18.393034-05:
DOI: 10.1002/pssc.201300638

• Control of density of CdSe quantum dots grown by MEE on MgS
• Authors: Akhil Rajan; Richard T. Moug, Ian A. Davidson, Kevin A. Prior
Pages: 1240 - 1243
Abstract: CdSe quantum dots were grown on MgS barrier layers by migration enhanced epitaxy. Following depositon of CdSe at 240 °C, the layers were annealed at 320 °C. In this study the annealing time was varied along with a delay time introduced between the CdSe deposition and the high temperature anneal. By varying just these two parameters the CdSe dot density measured by AFM could be varied by one order of magnitude. A short growth delay of just one minute between deposition and annealing was particularly effective and gave the lowest CdSe dot density reported so far of ∼40 × 108cm–2. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2014-04-07T06:10:08.668027-05:
DOI: 10.1002/pssc.201300567

• Energy relaxation process in exciton transfer between (Zn, Cd, Mn)Se and
(Zn, Cd)Se quantum wells
• Authors: Takashi Matsumoto; Fumiaki Iwasaki, Shuhei Konaka, Masao Hishikawa, Sakyo Fukasawa, Tsutomu Muranaka, Yoichi Nabetani, Akira Ishikawa, Kazuharu Uchiyama, Kiyoshi Kobayashi, Hirokazu Hori
Pages: 1244 - 1247
Abstract: Excitation transfer in semiconductor nanostructure is an elemental process of next generation optoelectronic devices. Energy relaxation process in exciton transfer from the lowest state of a quantum well to the lowest state of the next well was studied. The energy relaxation process is essential for the completion of the transfer. Longitudinal optical (LO) phonon assisted energy relaxation was found to be most effective for exciton injection into the lowest state of very thin quantum wells on the basis of PLE measurements. A three‐quantum‐well structure including a 0.6‐nm thick (Zn, Cd, Mn)Se well and a 1.2‐nm thick (Zn, Cd)Se well separated by a 15‐nm ZnSe barrier was prepared. Energy difference of exciton in the two wells was close to the LO phonon energy. The exciton transfer efficiency between the two wells was measured as a function of external magnetic field. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2014-03-25T02:20:03.074838-05:
DOI: 10.1002/pssc.201300599

• Observation of oscillations in energy of Aharonov–Bohm excitons in
type‐II ZnTe/ZnSe stacked submonolayer quantum dots
• Authors: Bidisha Roy; Haojie Ji, Siddharth Dhomkar, Maria C. Tamargo, Igor L. Kuskovsky
Pages: 1248 - 1251
Abstract: We report our recent experiments with type‐II ZnTe/ZnSe stacked submonolayer quantum dots that show the dependence of photoluminescence (PL) emission energy on the magnetic field. This is explained as due to the excitonic Aharonov‐Bohm (AB) effect. The AB oscillations in energy are observed for each of the contributing emission bands and are correlated with the changes in the magneto‐PL emission intensity. We propose that interplay of magneto‐excitonic behavior, the Coulomb interaction and mixing of angular momentum states are responsible for the observed behavior of the AB excitons depending on the magnetic field ranges. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2014-04-07T06:20:13.680601-05:
DOI: 10.1002/pssc.201300601

• Growth and electro‐optical characterization of ZnMgTe/ZnTe waveguide
by molecular beam epitaxy
• Authors: W. Sun; T. Nakasu, K. Taguri, T. Aiba, S. Yamashita, M. Kobayashi, H. Togo, T. Asahi
Pages: 1252 - 1255
Abstract: ZnMgTe/ZnTe/ZnMgTe thin film waveguide with high crystal quality were grown by molecular beam epitaxy (MBE). The in‐plane mismatch between the ZnMgTe cladding layers and ZnTe core layer was about 0.02% which was measured by X‐ray reciprocal space mapping (RSM). It indicated that films were grown coherently with high crystal quality. The Electro‐Optical characterization of waveguide was evaluated using 1.55µm polarized lights and bias applied on the waveguide device from –15 V to +15 V. The de‐pendence of light phase shift passed though the waveguide on the applied voltage bias was studied. The electro‐optical characterization of the waveguide device was about 7% of the theoretical calculation. It could be improved by increasing the resistance ratio between the ZnMgTe/ZnTe/ZnMgTe waveguide structure and substrate so that the electric field applied on the waveguide structure could be improved. It was indicated that the ZnMgTe/ZnTe/ZnMgTe thin film waveguide has the potential to become a high efficiency electro‐optical device. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2014-03-25T02:20:08.858909-05:
DOI: 10.1002/pssc.201300604

• Electrically driven single photon emission from a CdSe/ZnSSe/MgS
semiconductor quantum dot
• Authors: Wolf Quitsch; Tilmar Kümmell, Arne Gust, Carsten Kruse, Detlef Hommel, Gerd Bacher
Pages: 1256 - 1259
Abstract: We demonstrate electrically driven single photon emission from a CdSe/ZnSSe/MgS single quantum dot embedded in a resonant cavity light emitting diode. Patterned Pd/Au top contacts are used to inject the charge carriers locally. Single quantum dot electroluminescence is obtained at T = 4 K from nanoapertures lithographically defined in the top contacts. At low current densities, antibunching with a value of g(2)(0) = 0.16 is achieved. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2014-04-07T06:20:10.884676-05:
DOI: 10.1002/pssc.201300627

• Electroluminescence from nitrogen doped ZnO nanoparticles
• Authors: Yasuhisa Fujita; Kyota Moriyama, Yuto Hiragino, Yutaka Furubayashi, Hideki Hashimoto, Toshiyuki Yoshida
Pages: 1260 - 1262
Abstract: The first light emitting diodes using nitrogen doped ZnO nanoparticles (NPs) coated film on GZO have been demonstrated. This device showed diode characteristics in I ‐V measurement and near band edge UV electroluminescence (EL) was observed at the forward voltage of over 3 V. Only near band edge emission was observed in the EL spectrum while PL spectrum has a defect peak. This indicates the efficient exciton recombination was occurred due to the injection of high concentration holes and electrons into the NPs. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2014-03-31T02:10:20.091371-05:
DOI: 10.1002/pssc.201300645

• Bottom‐up approach to control the photon outcoupling of a
II‐VI quantum dot with a photonic wire
• Authors: T. Cremel; M. Elouneg‐Jamroz, E. Bellet‐Amalric, L. Cagnon, S. Tatarenko, K. Kheng
Pages: 1263 - 1266
Abstract: Epitaxially‐grown semiconductor quantum dots are promising as single‐photon sources due to their compatibility with manufacturing techniques and their ability to be integrated into compact devices. Efficient collection of emitted photons is required for practical use of such nano‐emitters. Here, we show the possibility to form photonic wires for efficient extraction of photons by covering nanowire quantum dots with a dielectric coating using atomic layer deposition. We experimentally obtain an Al2O3‐based photonic wire with a quantum dot precisely positioned along its axis. Using finite‐difference time‐domain (FDTD) simulations of ZnO‐based photonic structures, we calculate the optimal wire geometry which leads to maximum emitted power along the wire axis. We obtain maximum values of 74% and 52% of the total emitted power for radial and a longitudinal dipoles respectively. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2014-04-04T02:20:09.667162-05:
DOI: 10.1002/pssc.201300737

• Fabrication of ZnSe‐based microcavities for lasing in the strong
coupling regime and polariton confinement
• Authors: Thorsten Klein; Sebastian Klembt, Kathrin Sebald, Stephan Figge, Arne Gust, Carsten Kruse, Detlef Hommel, Jürgen Gutowski, Emilien Durupt, Daniel Le Si Dang, Maxime Richard
Pages: 1267 - 1272
Abstract: We report on the realization of monolithic, i.e. fully epitaxial ZnSe‐based microcavities with a 1λ‐cavity and a 3λ‐cavity for the investigation of strong coupling phenomena. A crucial building block is the fabrication of a lattice matched distributed Bragg reflector for the blue spectral region, consisting of quaternary ZnMgSSe layers as the high‐index material and a MgS/ZnCdSe superlattice as the low‐index material. Strong coupling at low temperatures was achieved with a vacuum Rabi splitting of 19 meV for the 1λ‐cavity (at 70K) and of 40 meV for the 3λ‐cavity (at 7 K). Microstructures such as micropillars, waveguides, ringresonators, and molecule chains were fabricated using focused ion‐beam etching. Discrete optical modes in micropillars were observed for both cavity lengths confirming three‐dimensional optical confinement. Q‐factors up to 6500 indicate a high optical quality. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2014-04-07T06:20:09.522648-05:
DOI: 10.1002/pssc.201300705

• Investigation of p‐contact layers for BeZnSeTe/MgZnCdSe optical
devices on InP substrates
• Authors: Shingo Takamatsu; Ichirou Nomura, Toshiki Kobayashi, Keisuke Murakami, Tomohiro Shiraishi, Katsumi Kishino
Pages: 1273 - 1277
Abstract: ZnTe and ZnSeTe p‐contact layers were investigated for use in BeZnSeTe/MgZnCdSe optical devices on InP sub‐strates. The contact resistances (Rc) of Au electrodes to N‐doped p‐ZnTe and p‐ZnSeTe contact lay‐ers were evaluated using the circular transmission line model (c‐TLM) method. A lower Rc (3.1×10‐3 Ωcm2) was obtained for the ZnSeTe p‐contact sample than for the ZnTe sample (6.3×10‐3 Ωcm2). BeZnSeTe/MgZnCdSe yellow‐light‐emitting devices with a ZnTe or ZnSeTe p‐contact layer grown on InP substrates were characterized. A comparison of the current‐voltage (I‐V) characteristics of these devices showed that the turn‐on voltage of the ZnSeTe contact device was about 4 V lower than that of the ZnTe device. From the aging characteristics of these devices under direct‐current injection at room temperature, it was shown that the lifetime of the ZnSeTe contact device was 30 times longer than that of the ZnTe contact device. These results show that a ZnSeTe contact layer is more suitable for BeZnSeTe/MgZnCdSe optical devices on InP substrates than a ZnTe contact layer. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2014-03-25T02:20:03.907616-05:
DOI: 10.1002/pssc.201300616

• Formation of indium tin oxide transparent electrodes by magnetron
sputtering for II‐VI compound semiconductor optical devices on InP
substrates
• Authors: Tomohiro Shiraishi; Ichirou Nomura, Keisuke Murakami, Shingo Takamatsu, Toshiki Kobayashi, Katsumi Kishino
Pages: 1278 - 1281
Abstract: Indium tin oxide (ITO) transparent electrodes formed on II‐VI compound semiconductor optical devices on InP substrates were characterized. Two kinds of ZnCdSe/BeZnTe p‐n diode devices with a different p‐contact layer (i.e., p‐ZnTe and p‐ZnSeTe layers) were prepared to investigate more suitable p‐contact material for ITO electrodes on the II‐VI devices. Thin ITO layers were deposited on the devices by magnetron sputtering. From injection current density versus applied voltage (J‐V) characteristics, the turn‐on voltage of the ZnTe contact device was found to be lower than that of the ZnSeTe contact device by about 2 V. The J‐V characteristic of the ZnTe device was comparable to that of the device with Au electrodes on the p‐contact instead of ITO. Using ITO electrodes, ZnCdSe/BeZnTe erlattice photovoltaic devices with ZnTe and ZnSeTe p‐contact layers were fabricated. The devices were characterized under 1.5 AM illumination at room temperature. The J‐V characteristics showed that the device performances of the ZnTe contact device were almost erior to those of the ZnSeTe device. Open‐circuit voltage, short‐circuit current density, fill factor, and maximum conversion efficiency of the ZnTe device were 0.90 V, 4.7 A/cm2, 0.35, and 1.5%, respectively. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2014-03-31T02:10:06.123927-05:
DOI: 10.1002/pssc.201300620

• Molecular beam epitaxy of p‐type ZnSTe:N and
p–n‐junction light emitting diodes
• Authors: Kunio Ichino; Takahiro Kojima, Shunsuke Obata, Takuma Kuroyanagi, Kenta Kimata, Shoichi Nakazawa, Shota Kashiyama
Pages: 1282 - 1285
Abstract: p‐type doping of ZnS1–xTex alloy with N acceptors has been studied with an idea that an upward shift of the valence band maximum due to Te incorporation could improve p‐type doping efficiency. The resistivity was found to be less than 100 Ωcm for the layers with 0.2 < x < 0.3, which are suggested to be p‐type from the currentvoltage (I – V) characteristic and the electron‐beam induced current. For further characterization, ZnSTe:N/n‐ZnS diode structures have been fabricated. It was found that the diode exhibits clear rectification in I – V characteristic, and blue‐green electroluminescence probably due to hole injection from the ZnSTe:N layer into the n‐ZnS layer. These results indicate p‐type conduction in ZnSTe:N, and thus the light‐emitting diode operation in the ZnS‐based pn‐junctions. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2014-04-07T06:20:11.756092-05:
DOI: 10.1002/pssc.201300626

• Application of solar cell using II‐III‐VI compound thin film
fabricated by conventional sputtering process
• Authors: H. Deguchi
Pages: 1286 - 1291
Abstract: In order to achieve low cost solar cells, a novel type multinary compound thin film solar cell using ZnInS (II‐III‐VI) thin film as n‐type layer and other layer fabricated by the conventional sputtering process were realized. An AgInTe/ZnInS thin film solar cell fabricated by the conventional sputtering process showed the conversion efficiency is 1.1%. In this study, p‐type materials suitable for ZnInS and doping ZnInS with additive elements such as IIa (Ca,Sr) and VIb (O) group elements were investigated to improve the characteristics of ZnInS thin film solar cell. As the results, the best conversion efficiency of 2.8% was obtained CuInGaSe/CaZnInS thin film solar cell. This value is superior to that of AgInTe/ZnInS thin film solar cell by 2.5 times. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2014-04-04T02:20:10.676362-05:
DOI: 10.1002/pssc.201300735

• Sputtering‐assisted metal‐organic chemical vapor deposition of
Yb‐doped ZnO for photonic conversion in Si solar cells
• Authors: Ryutaro Okada; Wei Miao, Yoshikazu Terai, Takahiro Tsuji, Yasufumi Fujiwara
Pages: 1292 - 1295
Abstract: We have grown Yb‐doped ZnO (ZnO:Yb) on c‐plane sapphire substrates by sputtering‐assisted metal‐organic chemical vapor deposition (SA‐MOCVD). X‐ray diffraction (XRD) revealed that these ZnO:Yb films exhibit a c‐axis orientation and that the lattice constant increases with Yb concentration. After annealing the samples at 600 °C for 0.5 h in O2, they showed a clear 980 nm emission due to the intra‐4f shell transitions of 2F5/2–2F7/2in Yb3+ ions. It turns out that Yb lu‐minescent centers with different local structures coexist, which exhibit different energy transfer processes from the ZnO host. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2014-03-25T02:20:04.724444-05:
DOI: 10.1002/pssc.201300614

• Identification of recombination centers responsible for reduction of
energy conversion efficiency in CdTe‐based solar cells
• Authors: G. Karczewski; S. Chusnutdinow, K. Olender, T. Wosiński, T. Wojtowicz
Pages: 1296 - 1299
Abstract: In this work we discuss experimental data which can explain reasons for the limited energy conversion efficiencies observed in monocrystalline, thin‐film CdTe‐based solar cells grown molecular beam epitaxy. Two kinds of samples has been investigated and discussed – p‐ and n‐type doped CdTe layers with metallic Schottky barriers and p‐i‐n heterojunctions (p‐ZnTe/i‐CdTe/n‐CdTe solar cells). Both kinds of junctions exhibit strong rectifying properties with the rectifying coefficient exceeding 105 at 300 K and +/– 1 V. Photovoltaic properties of the solar cells have been determined by I–V measurements under illumination and by spectral characteristics of photocurrent. Based on the spectral measurements it was found that the p‐ZnTe/i‐CdTe/n‐CdTe diodes are sensitive to illumination within the 550–850 nm wavelength range confirming their applicability for solar energy conversion. I–V characteristics measured at 1‐sun illumination yield relatively low energy conversion efficiencies below 4.9%. In order to determine the origin of the limited efficiency in the CdTe‐based solar cells (theoretical limit for n‐CdTe/p‐ZnTe solar cells is as high as 20%) the deep level transient spectroscopy (DLTS) technique has been applied. The results of these DLTS studies revealed the presence of deep electron and hole traps. The low‐temperature DLTS peaks can be ascribed to the hole traps in the CdTe absorber. The high‐temperature DLTS peak changes its sign depending on the sign of the filling pulses acting as a majority trap for negative filling pulses and minority trap for positive filling pulses. The estimated activation energies of the majority‐ and minority trap level are equal to 0.74–0.78 eV and 1.05 eV, respectively. The sum of these energies is close to the value of the CdTe energy gap, suggesting that this energy level can be assigned to the recombination center present in the CdTe absorber material. Basing on the logarithmic capture kinetics of the traps detected in the high‐temperature region we assign the recombination center to electronic states of extended defects, probably threading dislocations. Very similar DLTS results obtained for CdTe Schottky barriers confirm the conclusion. Thus, we conclude that not the point defects but rather extended defect are responsible for the limited energy conversion efficiency in CdTe‐based solar cells.
PubDate: 2014-04-04T02:23:05.825675-05:
DOI: 10.1002/pssc.201300743

• Low dark current and stable ultraviolet avalanche photodiode of organic
(PEDOT:PSS)‐inorganic (ZnSSe) hybrid junction structure
• Authors: Tomoki Abe; Noriyuki Ikadatsu, Ryoichi Inoue, Takeru Fujimoto, Kenta Tanaka, Akio Tazue, Yusuke Inagaki, Masahiro Ebisu, Hirofumi Kasada, Koshi Ando
Pages: 1300 - 1303
Abstract: We have developed organic‐inorganic hybrid avalanche photodiode (APD) with conducting polymer as a window layer on ZnSSe/n‐GaAs wafers. APD wafers used in this study were grown by molecular beam epitaxy (MBE). We used PEDOT:PSS as hole‐transport conducting polymer window layers formed by inkjet method. We have succeeded in fabrication of low dark current and stable ultraviolet hybrid APDs. The present device has exhibited very low voltage APD operation at 29 V and extremely low dark current of 10–11 A/mm2 in the avalanche breakdown region. The APD device 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 into package with N2 atmosphere. We also demonstrated integrated devices operation in PIN mode. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2014-03-25T02:20:09.66061-05:0
DOI: 10.1002/pssc.201300602

• Applicability of nitrogen‐doped ZnO single crystals for
photoconductive type UV sensors
• Authors: Shuzo Takahashi; Takami Abe, Akira Nakagawa, Syuhei Kamata, Tetsuya Chiba, Michiko Nakagawa, Yasuhiro Kashiwaba, Shigeki Chiba, Haruyuki Endo, Kazuyuki Meguro, Masahiro Daibo, Ikuo Niikura, Yasube Kashiwaba, Shuzo Oshima, Hiroshi Osada
Pages: 1304 - 1307
Abstract: Nitrogen‐doped (N‐doped) ZnO single crystals were prepared by the hydrothermal method. Resistivity of the N‐doped ZnO single crystal was 107–108 Ωcm, which was about 104‐times higher than that of the non‐doped ZnO single crystal. Photocurrent of the O‐face was larger than that of the Zn‐face and maximum photoresponsivity was about 4×103 A/W. Photosensitivity (light/dark current ratio) of the Zn‐face of the N‐doped single crystal was 4×104 under illumination of 15 µW/cm2, but that of the O‐face was about 7×104. The visible rejection ratio (UV/visible photocurrent ratio) was over 104 for the Zn‐face of the N‐doped ZnO single crystal. Time response of the photocurrent of the N‐doped ZnO single crystal was remarkably improved compared to that of the non‐doped ZnO single crystal. An N‐doped ZnO single crystal is useful as a material for photoconductive type UV sensors. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2014-03-31T02:10:16.571087-05:
DOI: 10.1002/pssc.201300625

• Strong sp–d exchange coupling in ZnMnTe/ZnMgTe core/shell nanowires
• Authors: Piotr Wojnar; Elzbieta Janik, Jan Suffczyński, Joanna Papierska, Małgorzata Szymura, Wojciech Zaleszczyk, Sławomir Kret, Łukasz Kłopotowski, Tomasz Wojciechowski, Lech T. Baczewski, Maciej Wiater, Grzegorz Karczewski, Tomasz Wojtowicz, Jacek Kossut
Pages: 1308 - 1311
Abstract: In this work, our recent progress in the growth and optical studies of telluride nanowire heterostructures containing a small molar fraction of magnetic Mn‐ions of only a few percent is overviewed. ZnMnTe/ZnMgTe core/shell nanowires (NWs) are grown by molecular beam epitaxy by employing the vapor‐liquid‐solid growth mechanism assisted with gold catalyst. The structures are studied by means of photoluminescence and microphotoluminescence in an external magnetic field. In the first step, however, an activation of the near band edge emission from ZnTe and ZnMnTe nanowires is described, which is achieved by coating the nanowires with shells made of ZnMgTe. The role of these shells is to passivate Zn(Mn)Te surface states. The incorporation of Mn ions into the crystalline lattice of ZnMnTe nanowires is manifested as a considerable blue shift of near band edge emission with increasing Mn concentration inside the nanowire cores, which reflects directly the increase of their energy gap. In an external magnetic field the near band edge emission exhibits a giant spectral redshift accompanied by an increase of the circular polarization of the emitted light. Both effect are fingerprints of giant Zeeman splitting of the band edges due to sp‐d exchange interaction between the band carriers and magnetic Mn‐ions. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2014-03-24T04:10:13.379453-05:
DOI: 10.1002/pssc.201300512

• Structural and magnetic characterization of (Zn,Fe)Te thin films grown by
MBE
• Authors: Satoshi Ishitsuka; Takeru Domon, Ryota Akiyama, Ken Kanazawa, Shinji Kuroda, Hironori Ofuchi
Pages: 1312 - 1315
Abstract: We investigate the structural and magnetic properties of Zn1–xFex Te with an aim of discerning the intrinsic magnetism of this ternary compounds. Thin films of Zn1–xFex Te with a high Fe composition up to x = 0.2 were grown by molecular beam epitaxy (MBE) in the excess of Te flux against Zn flux. The structural analyses using X‐ray diffraction (XRD) and X‐ray absorption fine structure (XAFS) measurements reveal that crystals of the pure diluted phase are grown at low Fe compositions less than x = 0.02, while precipitates of extrinsic phases start to be formed at higher Fe compositions. In the magnetization measurements, the films of x ≤ 0.02, which were confirmed to be of the pure diluted phase, exhibit paramagnetic behaviors down to 2 K. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2014-04-04T02:20:13.414172-05:
DOI: 10.1002/pssc.201300649

• Nonreciprocal magneto‐optical effects in quantum wells
• Authors: V. Kochereshko; V. Kats, A. Platonov, V. Sapega, L. Besombes, D. Wolverson, H. Mariette
Pages: 1316 - 1319
Abstract: In this paper we predicted and observed a new magneto‐optical effect – the “effect of parity”. The effect is manifest as a redistribution of the oscillator strengths between spatially even and odd center of mass quantized states of the exciton in the quantum well. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2014-04-04T02:23:04.04807-05:0
DOI: 10.1002/pssc.201300747

• Electric‐field modulation of ferromagnetism in hexagonal chromium
telluride thin film
• Authors: Ryota Akiyama; Haruyoshi Oikawa, Kazuma Yamawaki, Shinji Kuroda
Pages: 1320 - 1323
Abstract: We report the electric‐field modulation of magnetism of a hexagonal Cr1–δTe thin film. A gate voltage VG is ap‐plied in the field effect capacitor (FEC) structure consisting of electric double‐layer capacitor (EDLC) of an ion liquid and a 2nm‐thick Cr1–δTe layer grown by molecular beam epitaxy (MBE) and the magnetization of the layer is directly measured using a superconducting quantum interference device (SQUID) magnetometer in the both configurations with magnetic fields perpendicular or parallel to the film plane. As a result, we observe a clear change in the magnetization vs. magnetic field (M‐H) curves by applying VG at a low temperature of 15 K in the perpendicular field configuration; the magnetization increases and the coercivity decreases by applying either positive or negative gate voltage. When the temperature is increased up to 160K, slightly lower than the Curie temperature, or the magnetization was measured in the in‐plane field configuration, the magnetization increases similarly by applying either positive or negative gate voltage, but the amount of the increase becomes much smaller. A possible mechanism of the electric‐field modulation is discussed in relation to the Cr vacancies in the Cr1–δTe layer. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2014-04-07T06:20:06.376583-05:
DOI: 10.1002/pssc.201300751

• Effect of acceptor co‐doping on magnetism and electronic states in
ferromagnetic semiconductor (Zn,Cr)Te
• Authors: Ke Zhang; Ryota Akiyama, Ken Kanazawa, Shinji Kuroda, Hironori Ofuchi
Pages: 1324 - 1327
Abstract: The magnetic properties and the electronic states were investigated for a magnetic semiconductor (Zn,Cr)Te co‐doped nitrogen (N) as an acceptor impurity. A series of N‐doped Zn1–xCrxTe thin films with Cr compositions in the range of x = 0.06–0.09 and N concentrations in the range of [N] = 1018–1020 cm–3 were grown by molecular beam epitaxy (MBE), and the magnetization measurement using superconducting quantum interference device (SQUID) magnetometer and the X‐ray absorption fine structure (XAFS) measurements were performed. As a result, the disappearance of ferromagnetic behaviors and the change in X‐ray absorption near edge structure (XANES) spectra were observed at almost the same nitrogen concentration around [N] = 1 × 1020 cm–3. This correlated change in the magnetic properteis and the Cr electronic states was discussed in relation to a decrease of the electron density in the 3d impurity level due to the N co‐doping. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2014-04-04T02:23:03.335498-05:
DOI: 10.1002/pssc.201300755

• Thermo‐migration of Te inclusions in CdZnTe during post‐growth
• Authors: G. Yang; A. E. Bolotnikov, P. M. Fochuk, G. S. Camarda, A. Hossain, U. N. Roy, Y. Cui, R. Pinder, J. Gray, R. B. James
Pages: 1328 - 1332
Abstract: We studied the post‐growth annealing of CdZnTe crystals in a temperature‐gradient field and compared the changes of Te inclusions in CdZnTe crystals before and after annealing. The infrared (IR) transmission microscopy shows that Te inclusions can migrate towards the high‐temperature end and leave some smaller dark spots behind. These dark spots may be voids within the original inclusions left behind after the migration of the Terich solid. Such thermo‐migration depends on the specific locations of the Te inclusions within the CdZnTe matrix. Grain boundaries could have a strong trapping effect on the migration of Te inclusions, probablythrough the high density of dislocation networks in the grain‐ boundary region. In addition, we also observed new Te inclusions in the grain‐boundary regions, which were formed during the annealing process. This phenomenon is attributed to the fast diffusion and gettering behavior of excess Te atoms, or possibly Cd vacancies, along the grain boundaries. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2014-03-31T02:10:19.245858-05:
DOI: 10.1002/pssc.201300644

• Vapor‐phase epitaxial growth of thick single crystal CdTe on Si
substrate for X‐ray, gamma ray spectroscopic detector development
• Authors: Madan Niraula; Kazuhito Yasuda, Hayate Yamashita, Yuto Wajima, Yudai Tsukamoto, Masahiko Matsumoto, Yuta Suzuki, Noriaki Takai, Yuki Tsukamoto, Yasunori Agata
Pages: 1333 - 1336
Abstract: We investigated MOVPE growth conditions to grow large‐area and thick single crystal CdTe layers with uniform material properties directly on (211) Si substrates to develop nuclear radiation detectors. We found that group VI/II precursor flow‐ratio as well as rapid thermal annealing performed by interrupting the growth at the initial stage has marked influence on the crystal quality. By using a VI/II precursor ratio of 3.0, and a 900 °C anneal performed in flowing hydrogen, we were able to achieve 1‐sq inch sized thick single crystal CdTe that showed uniform material properties and high crystal quality throughout the wafer. We further demonstrated that the grown crystals were suitable for fabricating nuclear radiation detector. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2014-03-24T04:10:10.757309-05:
DOI: 10.1002/pssc.201300559

• Time‐of‐flight measurements on Schottky CdTe nuclear detectors
• Authors: Kazuhiko Suzuki; Yoshihiro Ichinohe, Takayuki Sawada, Kazuaki Imai, Satoru Seto
Pages: 1337 - 1340
Abstract: Temporal evolution of the time‐of‐flight current waveforms of Schottky CdTe nuclear detectors as a function of the DC bias duration has been measured at several different temperatures from 278 K to 315 K to investigate the nature of the defects responsible for the polarization phenomena. Three relaxation processes with time constants from less than a second to as long as about a thousand seconds at room temperature are involved in the evolution. Based on the observed temperature dependence, we have concluded that two out of three relaxation processes are attributed to the ionization of defects at 0.54 eV and 0.6 eV. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2014-03-24T04:10:08.838197-05:
DOI: 10.1002/pssc.201300580

• Vapor transport deposition of large‐area polycrystalline CdTe for
• Authors: Keedong Yang; Bokyung Cha, Duchang Heo, Sungchae Jeon
Pages: 1341 - 1344
Abstract: Vapor transport deposition (VTD) process delivers saturated vapor to substrate, resulting in high‐throughput and scalable process. In addition, VTD can maintain lower substrate temperature than close‐spaced sublimation (CSS). The motivation of this work is to adopt several advantages of VTD for radiation image sensor application. Polycrystalline CdTe films were obtained on 300 mm×300 mm indium tin oxide (ITO) coated glass. The polycrystalline CdTe film has columnar structure with average grain size of 3 µm ∼ 9 µm, which can be controlled by changing the substrate temperature. In order to analyze electrical and X‐ray characteristics, ITO‐CdTe‐Al sandwich structured device was fabricated. Effective resistivity of the polycrystalline CdTe film was ∼1.4×109Ωcm. The device was operated under hole‐collection mode. The responsivity and the µτ product estimated to be 6.8 µC/cm2R and 5.5×10–7 cm2/V. The VTD can be a process of choice for monolithic integration of CdTe thick film for radiation image sensor and CMOS/TFT circuitry. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2014-03-25T02:20:10.564719-05:
DOI: 10.1002/pssc.201300600

• Estimation of band gap energy of Mgx Zn1‐xO films by photocurrent
• Authors: Takami Abe; Akira Nakagawa, Tetsuya Chiba, Michiko Nakagawa, Shuzo Takahashi, Shigeki Chiba, Yasuhiro Kashiwaba, Tsutomu Ojima, Katsumi Aota, Masahiro Daibo, Ikuo Niikura, Yasube Kashiwaba, Hiroshi Osada
Pages: 1345 - 1348
Abstract: The band gap energy (Eg) of high‐quality Mgx Zn1‐xO films grown on ZnO (0001) substrates by the plasma‐assisted reactive evaporation method using a ZnMg alloy could be estimated by the photocurrent (Iph). Measurement of Iph was more useful than photoluminescence (PL), transmittance or reflectance (R) spectra measurements for determination of Eg of materials with large binding energy of the excitons. The values estimated from the relation of (αkhν)2–hv plots using optical absorption coefficient αk calculated from extinction coefficient k were close to the peak energy of PL or R of these films. The values estimated from the relation of (αphhv)2–hν plots using inter‐band absorption coefficient αph calculated from Iph spectra were larger than the values of peak energy of PL or R despite strong absorption of the excitons. Therefore, it was thought that these values are closer to Eg. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2014-03-24T04:20:10.134026-05:
DOI: 10.1002/pssc.201300598

• Effect of surface morphology on the field emission property of ZnO films
• Authors: Zurita Zulkifli; Subramanian Munisamy, Mohd Zamri Mohd Yusop, Masaki Tanemura
Pages: 1349 - 1352
Abstract: Stable and high crystalline quality of ZnO nanocones have been successfully fabricated on glass substrates at room temperature. In 3 min irradiation by argon ion on ZnO thin film surface, ZnO nanocones with a number density of 8‐15 µm‐2 can be observed from SEM images. For a high performance of field emission (FE) device, an emission current stability test was carried out at a fixed electric field of 12 V/µm for 60 min. A stable current of 2.5 µA was observed after 30 min without any obvious irregular current flow. The current density of 1 µA cm‐2 was achieved at 9.8 V/µm and 7.8 V/µm before and after stability test, respectively. Even though some of the ZnO nanocones tip were melted due to Joule heating induced by high intensity of electric field, the field enhancement factor are still comparable with other types of nanostructure emitters. The surface morphology of ZnO nanocones after the stability test showed the nanocones of shorter length are not affected by the high electric field at the emission area in which this revealed the robustness of ZnO compared to CNTs/CNFs. The ZnO nanocones at out of the emission area are also not affected by the high electric field or by any heat generated in the vacuum chamber during field emission. Thus, due to the high thermal and mechanical stability, ZnO nanocones is reliable to be as a promising field emitter. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2014-03-25T02:20:05.50704-05:0
DOI: 10.1002/pssc.201300613

• Fermi‐level pinning by carrier com‐ pensating midgap donor
defect band in homoepitaxially grown p‐type ZnO by MBE
• Authors: T. Masamoto; K. Noda, T. Maejima, R. Natsume, T. Matsuo, A. Akiyama, T. Yukue, S. Hiroe, T. Abe, H. Kasada, Y. Harada, K. Ando
Pages: 1353 - 1356
Abstract: We have performed homoepitaxial MBE growth of nitrogen (N) ‐doped ZnO and studied the postanneal effect on electrical conduction properties. A rapid postanneal after MBE growth is found to enhance the donor–acceptor (D–A) pair emission intensity, converting from n‐type (as‐grown) to p‐type conduction. The p‐type ZnO showed extremely high resistivity (>103 Ω cm) at room temperature. Carrier‐compensating donor‐like defects in N‐doped ZnO were traced by using PPC (persistent photocurrent), which is coupled with in situ Hall effect measurements. It is found that highly resistive p‐ZnO includes a high density of metastable donor‐like defects forming a deep donor band in the midgap region. This midgap donor band plays a role in Fermi‐level pinning at around the midgap position, resulting in high resistivity. Based on X‐ray photoemission spectroscopy experiments one possible origin of the deep donor band is introduced as nitrogen molecule (N2(o)) defects locating at the O atomic site. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2014-03-31T02:10:12.217146-05:
DOI: 10.1002/pssc.201300618

• Heavily n‐type ZnO: A plasmonic material at telecommunication
wavelengths
• Authors: Sascha Kalusniak; Sergey Sadofev, Peter Schäfer, Fritz Henneberger
Pages: 1357 - 1360
Abstract: Doping of ZnO by Ga allows for generation of free electrons up to concentrations of about 1021 cm–3 without significant deterioration of the crystal structure. In this way, a metallic dielectric function is formed with a negative real part tuneable from the mid infrared up to telecommunication wavelengths. The losses are about one order of magnitude lower than in traditional metals. We demonstrate surface plasmon polaritons with dispersion relations that can be engineered in a unique way by utilizing epitaxial multi‐layer structures of different doping level. In contrast to the standard air/metal excitations, the surface‐plasmon‐polariton frequency approaches a finite value in the zero‐wavevector limit at metal/metaltype interfaces. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2014-04-07T06:20:07.291639-05:
DOI: 10.1002/pssc.201300738

• Heteroepitaxial growth of non‐polar ZnO films on single crystal
NdGaO3 (001) substrates by MOCVD
• Authors: Yasuhiro Kashiwaba; Tai Yokoyama, Mio Sakuma, Takami Abe, Akira Nakagawa, Ikuo Niikura, Yasube Kashiwaba, Masahiro Daibo, Hiroshi Osada
Pages: 1361 - 1364
Abstract: High‐quality non‐polar ZnO (11$\bar 2$0) films were epitaxially grown on single crystal NdGaO3 (NGO) (001) substrates. The non‐polar ZnO (11$\bar 2$0) films were grown by metal organic chemical vapour deposition using Zn(C5H7O2)2 and O2 gas as starting materials. X‐ray diffraction (XRD) peaks of ZnO (11$\bar 2$0) plane were observed in XRD patterns of 2θ‐ω scans in all films. Rotation domains were not found in XRD φ scan patterns of ZnO (11$\bar 2$0) films grown at a substrate temperature of 650 °C or less. XRD peaks of NGO (021) and ZnO (11$\bar 2$2) planes were observed at the same angle φ in the XRD φ scan patterns. The epitaxial relationship was ZnO (11$\bar 2$0)// NGO (001) and ZnO [0001] // NGO [010]. Lattice mismatch values along the ZnO [0001] direction and along the ZnO (1$\bar 1$00) direction were 5.36% and –3.70%, respectively. Growth rate was drastically decreased at the substrate temperature over 650 °C. Striped patterns along the ZnO [0001] direction were observed in atomic force microscopy images of ZnO (11$\bar 2$0) films grown at substrate temperatures of 600 and 650 °C. Emissions due to donor‐bound excitions were observed in photoluminescence spectra of ZnO (11$\bar 2$0) films measured at 10 K. It is thought that NGO (001) substrates are useful for growth of high‐quality non‐polar ZnO (11$\bar 2$0) films. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2014-03-24T04:10:09.706291-05:
DOI: 10.1002/pssc.201300573

• Synthesis of ZnO/MgZnO multilayer films by sol‐gel dip method
• Authors: Takashi Yasuda; Takao Sakurai, Akihiro Kikawada
Pages: 1365 - 1368
Abstract: In this work we have developed a computer controlled sol‐gel dip method using Zn‐acetate and/or Mg‐acetate as sources, which is designed for fabricating ZnO/MgZnO multilayer films automatically. The film thickness can be controlled precisely, by choosing sol‐gel source concentrations, pulling speeds of substrates, and stack numbers. High quality MgxZn1–xO films (x=0.18) have been synthesized using a sol‐gel source incorporated with 20% Mg‐acetate. The Mg content can be increased up to x=0.25, which exhibits the largest bandgap of 3.760 eV. We have successfully fabricated nano‐sized structures consisted of (ZnO(9nm)/Mg0.18Zn0.88O(6nm))10 on sapphire (001) substrates. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2014-04-04T02:23:04.838636-05:
DOI: 10.1002/pssc.201300745

• Improved transport properties for ZnO films on Al2O3(11$\bar2$0) by MOCVD
• Authors: Y. Hiragino; Y. Furubayashi, K. Moriyama, Y. Fujita
Pages: 1369 - 1372
Abstract: ZnO films on Al2O3 (112$\bar2$0) with excellent transport properties were grown using metalorganic chemical vapor deposition (MOCVD) with a high speed rotating disk and a separated showerhead. Diisopropylzinc and tert ‐butanol were used as Zn and O precursors, respectively. Hall‐effect measurements revealed that the ZnO films in this work showed a high mobility of 140 cm2/Vs and a low carrier concentration of 1.5×1017 cm–3, both of which are comparable to those grown by molecular beam epitaxy or pulsed laser deposition. This report should open a way to the mass production of single crystalline ZnO films which should be usable for optoelectronic devices. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PubDate: 2014-04-07T06:20:12.76005-05:0
DOI: 10.1002/pssc.201300611

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