bluuebunny/crossref_metadata_2025_split huggingface dataset:
Studies of quantum levels in GaInNAs single quantum wells
Authors: Shirakata Sho , Kondow Masahiko , Kitatani Takeshi 
Published: August 2006

AbstractSpectroscopic studies have been carried out on the quantum levels in GaInNAs/GaAs single quantum wells (SQWs). Photoluminescence (PL), PL excitation (PLE), photoreflectance (PR), and high‐density‐excited PL (HDE‐PL) were measured on high quality GaInNAs SQWs, Ga0.65In0.35N0.01As0.99/GaAs (well thickness: l z = 10 nm) and Ga0.65In0.35N0.005As0.995/GaAs (l z = 3∼10 nm), grown by molecular‐beam epitaxy. For Ga0.65In0.35N0.01As0.99/GaAs (l z = 10 nm), PL at 8 K exhibited a peak at 1.07 eV due to the exciton‐related transition between quantum levels of ground states (e1–hh1). Both PR and PLE exhibited three transitions (1.17, 1.20 and 1.32 eV), and the former two transitions were assigned to as either of e1–lh1 and e2–hh2 transitions, while the transition at 1.32 eV was assigned to as the e2–lh2 transition. For HDE‐PL, a new PL peak was observed at about 1.2 eV, and it was assigned to the unresolved e1–lh1 and e2–hh2 transitions. Similar optical measurements have been done on the Ga0.65In0.35N0.005As0.995/GaAs with various l z (3∼10 nm). Dependence of optical spectra and energies of quantum levels on l z have been studied. It has been found that HDE‐PL in combination with PLE is a good tool for the study of the quantum level of GaInNAs SQW. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Urbach's tail in the absorption spectra of CuIn5Se8 and CuGa3Se5 single crystals
Authors: Arushanov E. , Levcenko S. , Syrbu N. N. , Nateprov A. , Tezlevan V. , Merino J. M. , León M. 
Published: August 2006

AbstractOptical absorption spectra of CuIn5Se8 and CuGa3Se5 single crystals grown by chemical vapour transport were investigated in the range of 10–300 K. The logarithmic variation of the absorption coefficient with photon energy observed in both compounds just below the fundamental absorption edge shows a linear dependence at different temperatures in agreement with Urbach's rule. The Urbach energy as well as the energy associated with the electron/exciton–phonon interaction related to Urbach's tail are estimated. The latter is found to be around 52 (41) meV for CuIn5Se8 (CuGa3Se5). It is lower than that {58 (60) meV} earlier reported for these compounds and confirms higher structural quality of samples studied. It is shown that the temperature of the Urbach energy can be modeled in CuIn5Se8 (CuGa3Se5) as an Einstein oscillator with the Einstein temperature equal to 222 (266) K. It is found that in the material studied structural disorder is dominant at 300 K. It may be caused by some compositional deviation from stoichiometry. The latter was observed in the studied samples by using the EDAX method. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Fundamental absorption edge in CuIn5Se8 and CuGa3Se5 single crystals
Authors: León M. , Levcenko S. , Syrbu N. N. , Nateprov A. , Tezlevan V. , Merino J. M. , Arushanov E. 
Published: August 2006

AbstractOptical absorption spectra of CuIn5Se8 and CuGa3Se5 single crystals have been investigated. The energy gap E g for CuIn5Se8 (CuGa3Se5) was found to be varied from 1.27 (1.79) to 1.21 (1.71) eV in the temperature range between 10 and 300 K. The temperature dependence of E g was studied by means of the Einstein model and the Pässler model. The Einstein temperature {222 (267) K}, the Debye temperature {310 (380) K}, a dimensionless constant related to the electron–phonon coupling {1.62 (2.65)} as well as an effective energy {20 (24) meV} and a cut‐off phonon energy {35 (39) meV} have been estimated for CuIn5Se8 (CuGa3Se5). It was also found that the major contribution of phonons to the shift of E g versus temperature in CuIn5Se8 (CuGa3Se5) is mainly from optical phonons. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Magnetic properties investigations of Mn substituted ABX2 chalcopyrites
Authors: Schorr S. , Hoehne R. , Spemann D. , Doering Th. , Korzun B. V. 
Published: August 2006

AbstractPowder samples of Mn2x Cu1–x InS2 (x = 0.03) and Mn2x Cu1–x AlS2 (x = 0.01) were studied by X‐ray diffraction and magnetization measurements. With regard to the variation of structural parameters with Mn substitution it is evident, that Mn2+ is built into the chalcopyrit structure. For both samples the field dependence of the magnetization is characterized by a dominating linear behaviour with a positive and strongly temperature dependent susceptibility as expected for paramagnets. After subtraction of the linear part the almost no temperature dependent curves are s‐formed, ferromagnetic‐like loops with no hysteresis. In the sample with BIII = Al a magnetic transition is observed at about 48 K. We conclude that the dominating paramagnetism is superimposed by a small ferromagnetic part and speculate that the effect is of intrinsic nature. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Magnetic properties of intermetallic compounds La(Ni,Co,Cu)3
Authors: Tazuke Y. , Tanikawa H. , Okano A. , Miyaji T. 
Published: August 2006

AbstractLaNi3 exhibited a metallic antiferromagnetic property with T N = 30 K. La(Ni1–x Cox )3 with x = 0.01, 0.03 and 0.05 exhibited ferromagnetic properties, T C increasing linearly with increasing x . La(Ni1–2z Coz Cuz )3 with z = 0.015 exhibited a ferromagnetic property with a small T C. A La(Ni1–y Cuy )3 sample with y = 0.01 exhibited a Pauli‐paramagnetic property; those with y = 0.02, 0.03 and 0.04 exhibited gradual metamagnetic behavior and that with y = 0.05 exhibited a ferromagnetic property. The gradual metamagnetic M –H variations are numerically simulated by using Landau‐type free energies. The results suggest that the gradual metamagnetic behavior occurs from an antiferromagnetic state to a ferromagnetic one. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Positive temperature variation of the bandgap energy in AgGaSe2
Authors: Ozaki Shunji , Sasaki Manabu , Adachi Sadao 
Published: August 2006

AbstractOptical‐absorption, photoreflectance (PR), and photoluminescence spectra have been measured on the ternary chalcopyrite semiconductor AgGaSe2 at T = 15–300 K. The direct‐bandgap energy E 0A of AgGaSe2 determined from the optical absorption measurements shows unusual temperature dependence at low temperatures. The resultant coefficient ∂E 0A/∂T is positive at T < 70 K and negative above 70 K. The PR spectra also indicate positive temperature dependence of the bandgap energies, E 0A and E 0B, at T < 70 K. These results have been successfully explained by taking into account the negative lattice thermal expansion at low temperatures. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The optimization of CdSe nanoparticles synthesis in the apoferritin cavity
Authors: Iwahori Kenji , Morioka Takuya , Yamashita Ichiro 
Published: August 2006

AbstractCadmium selenide nanoparticles (CdSe NPs) were synthesized in the cavity of the cage‐shaped protein, apoferritin, by designing a slow chemical reaction, which employs tetraamminecadmium ion and selenourea. The ammonia water concentration and solution pH were optimized and the suppression of the formation of selenium oxide was also studied by deoxydation of the reaction solution. At the concentration of 5 mM ammonia water and at pH 9.5, with N2 gas bubbling, the core formation ratio (CFR) of CdSe NPs reached 75% and yield of protein ratio (YPR) was as high as 98%. N2 gas bubbling of reaction solution was found to be critical for the high CFR and high YPR of the CdSe NPs synthesis in apoferritin cavity. Using this optimized conditions, high quality CdSe NPs were obtained by the bio‐template, apoferritin protein method. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Thermoelectric properties of Zn1–xMxSb2O6 (M = Al, In)
Authors: Katsui A. , Matsushita H. 
Published: August 2006

AbstractIn order to develop thermoelectric oxides, ZnSb2O6 with a high figure of merit and high reliability, Zn1–x Mx Sb2O6 (M = Al, In) ceramics have been prepared by using a solid phase reaction method. The phase identification during synthesis was investigated by using X‐ray diffraction measurement. The thermoelectric properties such as the Seebeck coefficient, electrical conductivity in the region from a room temperature to about 900 K were evaluated after heating for 2 h at 1073 K in air. The power factor of Zn0.95Al0.05Sb2O6 was the highest among all samples at x = 0 to 0.1 over a wide range of temperature. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Structural properties of 2(ZnSe)x(CuInSe2)1–x crystals and thin films in the two‐phase region
Authors: Gremenok V. F. , Schorr S. , Wagner G. , Bente K. , Zaretskaya E. P. , Siarheyeva V. M. 
Published: August 2006

AbstractThis paper presents the results of the structural properties of 2(ZnSe)x (CuInSe2)1–x (ZCIS) crystals and thin films in the range 0.10 ≤ x ≤ 0.36. In this composition range the tetragonal phase (domains) within their surrounding cubic matrix coexists. The crystals were prepared by the solid‐state reaction of the elements, followed by controlled cooling at different rates. ZCIS thin films were prepared by selenization of sequentally evaporated ZnSe/(Cu + In) precursors. The selenization procedure was carried at various temperatures ranging from 300 to 540 °C. The morphology of the tetragonal domains and their orientation relationship to the cubic matrix were determined by selected area diffraction (SAD), transmission electron microscopy (TEM) and high resolution TEM (HRTEM). The results reveal that the compositions of domains and matrix within the thin films agree with those measured for polycrystalline bulk material, i.e. the extension of the two‐phase range mentioned above could be confirmed. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
First‐principles study of nitridoaluminosilicate CaAlSiN3
Authors: Mikami Masayoshi , Uheda Kyota , Kijima Naoto 
Published: August 2006

AbstractAtomic and electronic structure of nitridoaluminosilicate CaAlSiN3 (Cmc 21, No. 36), a distorted AlN‐based wurtzite superstructure with Al and Si disordered on 8b site and Ca occupying 4a site, has been investigated by first‐principles pseudopotential method based on density functional theory. The random distribution of Al/Si atoms is treated in two ways: (1) virtual crystal approximation (VCA) with a mixed Al/Si pseudopotential, (2) several assumptions of Al/Si distribution order in the primitive unit cell. Geometry optimization based on the aliovalent VCA reproduces the experimental orthorhombic structure as well as the bond lengths. The calculations of Al/Si‐ordered models lead to monoclinic structures that appear sufficiently close to the experimental structure, with the averages of the optimized Al–N/Si–N bond lengths corresponding to the experimental ones. Relative stability among the Al/Si‐ordered models appears consistent with Pauling's second crystal rule. The random Al/Si distribution leading to the experimental determination of the system as Cmc 21 can be explained by crystal symmetry, energetics among the ordered models, and configurational entropy effect. The electronic structure based on the VCA appears similar with those of the Al/Si‐ordered models. All the band structures indicate that the system has indirect band gap. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Characterization of Cu(In,Ga) (S,Se)2 thin films prepared by sequential evaporation from ternary compounds
Authors: Yamaguchi T. , Hatori M. , Niiyama S. , Miyake Y. 
Published: August 2006

AbstractCu(In,Ga) (S,Se)2 thin films were fabricated by sequential evaporation from CuGaSe2, CuInSe2 and In2S3 compounds for photovoltaic device applications. From XRF analysis, the Cu:(In + Ga):(S + Se) atomic ratio in all thin films was approximately 1:1:2. As the [In2S3]/([CuGaSe2] + [CuInSe2]) mole ratio in the evaporating materials increased, the S/(S + Se) atomic ratio in the thin films increased from 0 to 0.16 determined by XRF and to 0.43 by EPMA. XRD studies demonstrated that the prepared thin films had a chalcopyrite Cu(In,Ga) (S,Se)2 structure and the preferred orientation to the 112 plane. The SEM images demonstrated that Cu(In,Ga) (S,Se)2 thin films had large and columnar grains. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effects of water vapor introduction during Cu(In1–xGax)Se2deposition on thin film properties and solar cell performance
Authors: Ishizuka S. , Sakurai K. , Yamada A. , Matsubara K. , Shibata H. , Yonemura M. , Nakamura S. , Nakanishi H. , Kojima T. , Niki S. 
Published: August 2006

AbstractThe effects of water vapor introduction during the growth of Cu(In1–xGax)Se2, specifically CuInSe2(CISe), Cu(In,Ga)Se2(CIGSe), and CuGaSe2(CGSe) thin films were studied. We have developed thus far a novel technique to improve CIGSe (x∼ 0.5) cell performance by means of water vapor introduction during CIGSe deposition. In this study, we have examined the effectiveness of water vapor introduction for otherx‐compositions (CISe and CGSe). Variations in the electrical properties observed in CIGSe (x∼ 0.5), that is, increasing hole density and conductivity with water vapor introduction, were also observed in CISe and CGSe. Water vapor introduction affected solar cell performance as well; open circuit voltages, short circuit current densities, and efficiencies were improved. The improvements in cell performance are thought to be related to annihilation of donor defects arising from Se‐vacancies by incorporation of oxygen from the water vapor. In addition to this, the sodium content in the CIGSe layers was found to depend on the partial pressure of water vapor during deposition. This result suggests that the improvement mechanism is also related with the so‐called ‘Na‐effects'. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Prediction of solid‐state reactions for the formation of the chalcopyrites CuInS2, CuGaS2, CuAlS2 and CuAlSe2 starting from binary compounds
Authors: Hergert Frank , Jost Stefan , Hock Rainer , Purwins Michael 
Published: August 2006

AbstractIn a recent work we have described the importance of epitaxy for the formation of CuInSe2 and CuGaSe2. In this article we identify epitaxial relations between binary selenide compounds serving as educts for the formation of the title compounds. From this we derive a set of possible chemical reaction equations for those solid‐state reactions, which will preferably take place. By exploiting these reactions the chalcopyrite compounds can be synthesised smartly in short annealing processes at relatively low temperatures. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optical and magnetic properties of c ‐oriented ZnCoO films
Authors: Zhou Huijuan , Knies Christoph , Hofmann Detlev M. , Stehr Jan , Volbers Niklas , Meyer Bruno K. , Chen Limei , Klar Peter , Heimbrodt Wolfram 
Published: August 2006

AbstractWe investigated ZnCoO thin films prepared via sol‐gel methods and dip‐coating techniques. The Co concentrations range from 0.5% to 5%. The films show the wurtzite crystal structure of ZnO and are highly c ‐axis oriented grown on the quartz substrates. They have a typical grain size of 20 to 50 nm and a thickness between 300 nm and 1 µm. The fine structures of the Co (3d7) internal absorptions are well resolved, all zero‐phonon lines (ZPL) and phonon replica related to the 4T1(F) → 4A2 are observed, demonstrating the good crystalline quality of the layers and the incorporation of the Co2+ on Zn2+ lattice sites. The films show paramagnetic behaviour. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Luminescence properties of YAl3(BO3)4 substituted with Sc3+ ions
Authors: Yoshida Hisashi , Fujikawa Kazuhiro , Toyoshima Hiroaki , Watanabe Shinta , Ogasawara Kazuyoshi 
Published: August 2006

AbstractLuminescence properties of YAl3(BO3)4 (YAB) and Y1–x Scx Al3(BO3)4 (YSAB) have been investigated under vacuum ultraviolet (VUV) light excitation. In YAB, two emission bands peaking at 3.2 and 3.9 eV are observed. On the other hand, there appear two emission bands at 3.2 eV and about 4.1 eV in YSAB. The origins of these emission bands are ascribed to two kinds of BO3 atomic groups. We suppose that the shift of the peak around 4 eV band is deeply related to the fact that one kind of BO3 atomic groups of YSAB are significantly distorted compared to that of YAB. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Band structure and dielectric function of TlInTe2
Authors: Wakita K. , Shim Y. , Orudzhev G. , Mamedov N. , Hashimzade F. 
Published: August 2006

AbstractThe band structure of ternary chain TlInTe2 was calculated with allowance for non‐locality of ionic pseudo‐potentials. The dielectric function, as well as the effective masses of holes and electrons, the effective number of valence electrons, and the function of characteristic losses were determined. The results of comparison between the calculated dielectric function and the one obtained ellipsometrically in the spectral range from 0.85 to 6 eV are quite favorable. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
InxGa1–xAs single crystal growth by dispersing local misfit stress
Authors: Miyata Hiroaki , Adachi Satoshi , Ogata Yasuyuki , Tsuru Tetsuya , Muramatsu Yuji , Kinoshita Kyoichi , Odawara Osamu , Yoda Shinichi 
Published: August 2006

AbstractWe succeeded in growing a single crystal by dispersing the misfit stress around an initial solid‐liquid interface in In0.3Ga0.7As ternary bulk crystal growth. We gradually increased concentration of indium arsenide so that the local misfit stress could be smaller than critical resolved shear stress. The traveling lqiuidus‐zone (TLZ) method was applied for growing crystals. To grow a single In0.3Ga0.7As crystal, an In0.1Ga0.9As single crystal region was grown first on a GaAs seed. Then the concentration of indium arsenide was gradually increased up to In0.3Ga0.7As by lowering temperature at the interface. As a result, In0.3Ga0.7As single crystals of 2 mm in thickness, 10 mm in width and more than 25 mm in length were successfully obtained. Mean value of full width half maximum (FWHM) of X‐ray rocking curves in the In0.3Ga0.7As grown crystal was 0.116°. It is not small enough but it will be improved by increasing compositional homogeneity. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
P‐type conductive CuYO2 phosphor Co‐doped with Eu, Tb or Tm rare‐earth cation and Ca acceptor cation
Authors: Tsuboi Nozomu , Hoshino Takanobu , Kobayashi Satoshi , Kato Keizo , Kaneko Futao 
Published: August 2006

AbstractIn delafossite‐type oxides of CuRx Y1–x O2 (R = Eu, Tb or Tm) and CuRx Cay Y1–x –y O2 prepared through the conventional solid state reactions, the lattice constant dependence on the composition implies doping with the Tb3+, Eu3+ and Tm3+ cations on the Y3+ site. Noticeable sharp emission lines due to the f–f transitions of Eu3+, Tb3+ and Tm3+ are observed at room temperature in CuRx Cay Y1–x –y O2 as well as CuRx Y1–x O2. P‐type conductivity of CuRx Cay Y1–x –y O2 increases with increasing Ca concentration, indicating the increase of hole concentration caused by doping with Ca2+ acceptor cation on the Y3+ site. These results indicate the controllability of the luminescence and conductivity in delafossite‐type CuYO2 oxides by co‐doping with Eu, Tb or Tm rare‐earth cation and Ca acceptor cation on the Y3+ sites. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Ferromagnetism in short‐period GaGdN/GaN superlattices grown by RF‐MBE
Authors: Choi S. W. , Zhou Y. K. , Kim M. S. , Kimura S. , Emura S. , Hasegawa S. , Asahi H. 
Published: August 2006

AbstractGaGdN single layers and GaGdN/GaN short‐period superlattices (SLs) were grown on Al2O3(0001) substrates by radio frequency molecular beam epitaxy (RF‐MBE) and their magnetic and structural properties were investigated. Both types of samples exhibited ferromagnetic characteristics at both 10 and 300 K. Clear hysteresis and clear saturation were observed in the magnetization vs. magnetic field curves at both temperatures. The GaGdN/GaN short‐period SL samples showed significantly higher saturation magnetization than the GaGdN single layer samples. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Surface potential of chalcopyrite films measured by KPFM
Authors: Sadewasser S. 
Published: August 2006

AbstractAtomic force microscopy is widely used to characterize the surface topography of a variety of samples. Kelvin probe force microscopy (KPFM) additionally allows determining images of the surface potential with nanometer resolution. The KPFM technique will be introduced and studies on surfaces of chalcopyrite semiconductors for solar cell absorbers will be presented. It is shown that operation in ultra‐high vacuum (UHV) is required to obtain meaningful work function values. Different methods for obtaining UHV‐clean surfaces are presented and KPFM studies on these are compared. Surfaces where prepared by in‐vacuum deposition, inert‐gas transfer, in‐vacuum decapping of a protective Se‐cap and a peel‐off method. Finally, a sputter‐annealing cycle also allows to obtain well‐suited surfaces for KPFM studies. Employing KPFM, variations in the local surface potential at grain boundaries of polycrystalline CuGaSe2 films were observed. A potential drop indicates the presence of charged defects at grain boundaries. Furthermore, different electronic activity was found for different grain boundaries, as concluded from studies under illumination. Using laterally resolved surface photovoltage, a Cu2–x Se impurity phase could be observed in CuGaSe2. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Thermoelectric properties of Fe‐doped Ca3Co2O6 single crystals with a pseudo‐one‐dimensional structure
Authors: Takahashi Junichi , Shimada Masahiko , Yamane Hisanori 
Published: August 2006

AbstractColumnar single crystals of Fe‐doped Ca3Co2O6 with a pseudo‐one‐dimensional structure were synthesized by a flux method using K2CO3. Seebeck coefficient (S ) and electrical resistivity (ρ ) of an Fe‐doped Ca3Co2O6 single crystal along the elongated direction were measured in the temperature range from room temperature to over 1000 K in air. The single crystal showed p‐type semiconducting behaviour and the Fe doping augmented the S, ρ, and the power factor (S 2ρ –1). (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
MBE growth and properties of GaMnAs with high level of Zn acceptor incorporation
Authors: Asubar J. T. , Sato S. , Jinbo Y. , Uchitomi N. 
Published: August 2006

AbstractGaMnAs epitaxial films with high Zn incorporation level were prepared by molecular beam epitaxy. Our results indicate an increasing hole concentration p accompanied by decreasing Curie temperature T C and transition towards metallic behavior of the epitaxial film properties with increasing level of Zn incorporation. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Characterization of Cu(In,Ga)Se2 thin films by time‐resolved photoluminescence
Authors: Shimakawa Shin‐ichi , Kitani Kimihiko , Hayashi Shigeo , Satoh Takuya , Hashimoto Yasuhiro , Takahashi Yasuhito , Negami Takayuki 
Published: August 2006

AbstractCu(In,Ga)Se2(CIGS) films were characterized by time‐resolved photoluminescence (TRPL) on performances of solar cells. Open circuit voltage and efficiency of the solar cells increased with increasing the TRPL lifetimes meausred at 77 K and room temperature. The results at 77 K show that the CIGS films with the TRPL lifetime of over 30 ns achieve an efficiency of exceeding 15% of the solar cells. Dependence of the TRPL lifetime on the photon energy was observed on the CIGS film with high efficiency at both temperatures. This dependence is discussed on localization of exited carriers and non‐radiative centres. The minority carrier lifetime which dominates the solar cell performances can be characterized by not only the TRPL lifetime but its dependence on the photon energy. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)