bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterization of Electronic States Using a Polarized Light and a Display Analyzer
Authors: Daimon Hiroshi , Kotsugi Masato , Okuda Taichi , Hattori Ken
Published: March 2014

The applicability of the recently-developed method (called ODAD: orbital determination from angular distribution) to analyze and assign atomic orbitals, such as p

z
or d
x
2-y
2, constituting a valence band from observed two-dimensional photoelectron angular distributions(PEAD) is discussed systematically. The two-dimensional PEAD pattern obtained by using a linearly polarized light are characteristic for the initial atomic orbital, and we can deduce the component ratio of atomic orbitals constituting the valence band by fitting the observed PEAD to the calculated patterns. When the observed region is limited by the band structure effect, it is shown that we can deduce the component ratio of atomic orbitals by rotating the sample even though the atomic orbitals have the same magnetic quantum number m.
Wavelength-Modulated Diffraction. A New Method for the Phase Determination of the Structure Factor
Authors: Iwasaki Hiroshi , Yurugi Takahiro , Yoshimura Yukio
Published: March 2014

A new diffraction method has been proposed in which Bragg reflections are recorded with changing continually the wavelength of synchrotron radiation in the vicinity of the absorption edge of an atom contained in a crystal. It is shown that the intensity gradient with the wavelength of the h
k
l reflection is in a simple relation to the real and imaginary parts of the structure factor of that re-flection and, if the positions of the anomalously scattering atoms are known or properly assumed, the phase of F(h
k
l) can be derived by solving two simultaneous linear equations. The procedure is particularly simple when the crystal is centrosymmetric. The method, called the wavelength-modulated diffraction method, is free from the problem of intensity scaling encountered in other methods of phase determination.
Experiment for X-Ray Photon Correlation Spectroscopy –Coherence of Soft X-Ray Radiation from the Undulator of KEK
Authors: Itoh Masayuki
Published: March 2014

Several photon correlation data of scattered light from nano-phase particles under thermal modulation were presented and analyzed; they were measured with a homodyne photon correlation spectroscopy with soft X-ray synchrotron radiation from the undulator of BL-2 at the Photon Factory in KEK at Tsukuba, Japan. The coherence and some problems regarding the X-ray from SR source were also discussed from the viewpoint of the possibility and applicability of X-ray photon correlation spectroscopy (XPCS) to the materials science.
The Development and Application of Imaging EXAFS Spectromicroscopy
Authors: Hwu Y. , Tsai W.-L. , Chang L.-W. , Chen C. H. , Wu C. C. , Noh D. Y. , Je J. H. , Fecher G. H. , Bertolo M. , Berger H. , Margaritondo G.
Published: March 2014

The capability to perform absorption spectroscopy with hard x-rays was added to the synchrotron imaging Spectromicroscopy technique. We present several successful test cases. First, the EXAFS (extended x-ray absorption fine structure) analysis was implemented in areas as small as few µm2 for transition-metal K edge absorption spectra. The corresponding structural information was complemented by chemical information from the near-edge region. Specifically, in the case of a cross-sectional cut steel different Fe oxidation states were found at different depths. Tests on a PVD grown TiN film revealed areas with oxidized Ti. Overall, these tests demonstrate the feasibility of combining structural and chemicals analysis with hard-x-ray absorption and high lateral resolution.
A Synchrotron Powder Diffraction Study of Na-LTA
Authors: Hasegawa Kazuhide , Nishibori Eiji , Takata Masaki , Sakata Makoto , Togashi Nozomu , Yu Jihong , Terasaki Osamu
Published: March 2014

The charge density distribution of Na-LTA is obtained by the Maximum Entropy Method (MEM) using synchrotron powder data. In the MEM map, all the components; framework, cations and absorbed water molecules, are all clearly shown even if the site occupation is very low, say less than 10%. A powder diffraction experiment is carried out by the transmission geometry with Imaging Plate (IP) detector at BL-6A2, PR In the analysis, a new method which is a iterative use of Rietveld refinement and MEM is applied in order to improve a structure model used in Rietveld refinement. An initial structure model used in Rietveld is just simple framework only. In the first Rietveld refinement, the agreement factor, RI, was very bad, i.e.37.4%. Following MEM analysis, however, gives the key information of how to improve next structure model for Rietveld refinement. Improvement of the structure model by the present method eventually lead to RI to be as low as 5.2%, which proves a great success of the method. The present method may lead a drastic change of structural studies of zeolite compounds when it is applied to high resolution and high intensity synchrotron powder data.
Soft X-ray XAFS Beamline for Advanced Materials Research at Compact Superconducting Ring
Authors: Handa Katsumi , Sakai Ichiro , Izuhara Osamu , Iwasaki Hiroshi , Yoshimura Yukio , Masui Shin , Murata Takatoshi
Published: March 2014

This paper describes a soft x-ray XAFS beamline constructed at the compact superconducting storage ring AURORA (575 MeV, 300 mA) at Ritsumeikan University. It consists of a pre-focusing torroidal mirror (located 4.5 m from the source point) and a double-crystal monochromator, 1:1 focusing geometry being adopted. Radiation of an energy in the range from 1000 to 4000 eV covered by four kinds of monochromator crystals can be used with a flux of 5×109 photons/sec/mm2 at the sample position. The beamline optics have been designed to get as high photon flux as possible from the compact ring. XAFS measurements can be made either in a transmission, total electron yield or fluorescent x-ray yield mode. The beamline is dedicated for advanced materials research but also for education of undergraduate students in the course of synchrotron radiation science.
ANKA–Service-Oriented Synchrotron Radiation Facility
Authors: Babayan Ruben Albert , Birkel Ingrid , Buth Gernot , Doyle Stephen , Einfeld Dieter , Göttert Jost , Hagelstein Michael , Hermle Stefan , Hesch Klaus , Huttel Erhard , Krüssel Alois , Lange Michael , Mathis Yves-Laurent , Mexner Wolfgang , Moser Herbert O. , Pellegrin Eric , Perez Francisco , Pont Montse , Ristau Uwe , Rossmanith Robert , Sajosch Heinrich , Schieler Harald , Simon Rolf , Steininger Ralph , Voigt Siegfried , Walter Ralf , Weimar Edmund , Weinl Andreas
Published: March 2014

ANKA is a 2.5 GeV synchrotron radiation facility under construction at Forschungszentrum Karlsruhe. ANKA is based on a 2.5 GeV electron storage ring injected from a 500 MeV booster synchrotron and a 50 MeV racetrack microtron. Nominal circulating electron current will be 400 mA. The facility is scheduled to become operational in fall 2000. ANKA will deliver photons predominantly in the hard X-ray range but it will also feature both XUV and infrared beamlines. So far, all beamlines will use bending magnets as sources, while provision is made to install appropriate insertion devices later on. ANKA has a novel mission which is characterised by giving preference to providing service to customers while maintaining a significant fraction of research work. ANKA will offer full service in X-ray lithography, mainly for micro- and nanofabrication, and in analysing and investigating non-destructively various structural, mechanical, chemical, electronic, magnetic, and molecular properties of samples and components.
High-Resolution Powder Diffractometry to Study the Phase Transition of h-BaTiO3
Authors: Noda Yukio , Akiyama Kazuyuki , Shobu Takahisa , Kuroiwa Yoshihiro , Yamaguchi Hirotaka
Published: March 2014

High-resolution powder diffraction experiments of hexagonal BaTiO3 were performed at BL02B1 of SPring-8 to determine the symmetry and the lattice form in the low temperature phases. The best resolution achieved was 0.0085° as FWHM even for the powder diffraction. The symmetry of the lowest ferroelectric phase was determined to be a monoclinic associated with small distortion. The deviation from 120° was only 0.05°. The intermediate phase was orthorhombic as was reported. Based on these analysis, both results on the high-resolution X-ray single crystal experiments performed at the home laboratory and the high-resolution powder neutron scattering experiments performed at JRR3M were interpreted.
XAFS Study on the Thermal Behavior of Nickel Species Dispersed in Brown Coals
Authors: Shirai Masayuki , Murakami Kenji , Arai Masahiko
Published: March 2014

The behavior of ion-exchanged nickel species in pyrolyzed Loy Yang brown coal was studied. C1 gas (CO, CO2, CH4) evolution was affected by the amount of nickel species loaded. XAFS analysis showed that the exchanged nickel ions aggregated to metal particles during pyrolysis and that the agglomeration temperature depended on the nickel loading. The catalysis of nickel species for the coal pyrolysis is explained by the aggregation behavior of them.
EXAFS Observation of Li Additive Effect on Structure of Rh Particles Supported on Zeolite
Authors: Bando Kyoko K. , Ichikuni Nobuyuki , Arakawa Hironori , Asakura Kiyotaka
Published: March 2014

The Rh ion-exchanged zeolite catalyst (RhY) shows extraordinarily high activity for CO2 conversion and the main product was methane. When we doped Li into RhY (Li/RhY), the main product drastically changed from methane to CO and promotion of ethanol formation was observed. In this work, we observed EXAFS spectra for RhY and Li/RhY and elucidated the structural difference between them, in order to reveal the origin of the different catalyses toward CO2 hydrogenation. We found disassembly and re-assembly of Rh particles in RhY during the reaction where Rh atoms could easily move around the pore and external surface of zeolite. On the other hand, the Rh atoms in Li/RhY were tightly bound in the Rh particles under the influence of Li additive and the Rh atoms kept their structure unchanged during the reaction. It was suggested that the difference in catalytic reactivity was due to that in the mobility of Rh particles.
Aerodynamic Levitation Studies of Ceramics at Very High-Temperature: XAFS and XRD
Authors: Landron Claude , Hennet Louis , Berthet Patrick , Coutures Jean-Pierre , Berar Jean-François
Published: March 2014

A levitation device associated with laser heating has been developed in order to measure the structure of ceramics at very high temperature by using synchrotron radiation sources. Combined X-ray diffraction and X-ray absorption measurements have been performed on spherical solid and liquid samples in a controlled atmosphere up to 2800°C. The analysis chamber was integrated with the 7-circles goniometer of the D2AM station at the ESRF. This technique presents a novel opportunity to probe the short-range and long-range properties of high-temperature oxides up to the liquid phase. By studying the local structure around cations in oxides, we have shown that the combined XAFS and XRD data, deriving from in-situ synchrotron radiation experiments, contain valuable information on phase transitions, contributing to the optimisation of the fabrication of ceramics.
Electron and Nuclear Densities of a Pyrochlore, Y2Sn2O7 Studied by the Maximum Entropy Method
Authors: Ikeda Tomohiro , Sakata Makoto , Takata Masaki , Kennedy Brendan J. , Cookson David J. , Howard Christopher J.
Published: March 2014

Electron and nuclear density distributions of the stoichiometric pyrochlore, Y2Sn2O7 are obtained by the Maximum Entropy Method (MEM) using synchrotron and neutron powder diffraction data. It is recognized from the MEM electron density distribution that there exist relatively strong covalency between Sn-O(2) atoms to form Sn2O6 sublattice and weak covalency between Y-O(1) atoms to form Y2O sublattice. There is no covalent bond linkage between these two sublattices. From the nuclear densities, it is found that the thermal vibrations of Y and Sn atoms parallel to both the Y-O(1) and Sn-O(2) bond directions are rather restricted.
Structural Aspects of Ternary Compounds - Crystal Structure, Chemical Bonding, Substitution, Defects and Semiconductivity of Multinary Compounds
Authors: Bente Klaus
Published: March 2014

Relations of stability, structure, crystal chemistry and crystal physics are of basic interest for the understanding of material properties. These relations are presented in an overview for semiconducting sphalerite types und their structure derivatives but also related for other structure types as wurtzite, NaCl and spinel. Also included are changes to metallic und superconductivity. Especially substitutional and interstitial as well as defect and vacancy phenomena and corresponding effects in mixed crystals are discussed. Due to these topcis, theories and empirical rules of different authors are compared with own results of III-V and II-VI–I-III-VI2 mixed crystal semiconductors and of peroskite mixed crystal systems. Hereby metal orderings, defects and superstructures are presented. For overview ing reasons, the paper is restricted to shortly explained tables and lists.
Characterization of Mo-doped CuAlS2 Single Crystals by PL and ESR
Authors: Nishi Takao , Ishibashi Naohiro , Katsumata Yuji , Sato Katsuaki
Published: March 2014

Near-infrared photoluminescence (PL) and electron spin resonance (ESR) spectra were measured at 6 K in single crystals of CuAlS2 doped with Mo. A fine-structure PL emission was observed around 1,600 nm (0.775 eV). The emission was assigned to the ligand-field transition in 4d3-manifold of Mo3+ ions. The ESR spectrum measured in the same crystal as used in the PL experiment showed a triplet structure around g∼2, which is characteristic of S=3/2 system. The activation energy of the temperature quenching of the ESR intensity was 4 meV, which is the same as that of the emission, suggesting that the ESR and the PL spectra originate from the same center.
Photoluminescence Properties of AgGaS2:Ho Single Crystals
Authors: Terasako Tomoaki , Hashimoto Katsuyuki , Shirakata Sho , Isomura Shigehiro , Niwa Eiji , Masumoto Katashi
Published: March 2014

Sharp photoluminescence (PL) lines related to the 5F3→5I7 transitions in Ho3+ ion (1.85∼1.93 eV) have been observed for single crystals of AgGaS2 doped with Ho prepared by thermal diffusion of Ho. The spectral shape of the series changed depending on the condition of thermal diffusion, suggesting the existence of several types of Ho-related luminescence centers. Moreover, it was found that the PL lines from the different luminescence centers exhibit different excitation and recombination mechanisms.
Sharp Photoluminescence Lines and Zeeman Effect in CuGaS2 Single Crystals
Authors: Shirakata Sho , Terasako Tomoaki , Isomura Shigehiro
Published: March 2014

Photoluminsecence (PL) studies have been carried out on the sharp zero-phonon lines at 2.461eV (H), 2.458eV (H'), 2.417 eV (R), 2.404 eV (S0), 2.397eV (Q0) and 2.295 eV (T0) in CuGaS2. The R, S0, and Q0 lines are enhanced by the thermal diffusion of Cu. The depth intensity profile showed that these sharp PL lines are related to defects created by the deviation from stoichiometry. Under high magnetic field (7T), the H line splits into three lines and the S0 and R lines split into two lines. No splitting was observed for Q0 and T0 lines and also for the bound exciton lines (2.495, 2.493, 2.490 and 2.487 eV). These Zeeman results are discussed in terms of native defects and impurities included in the luminescence centers.
Photoluminescence Excitation Spectra of CuGaSe2
Authors: Ohe Satoshi , Takata Shuichi , Wakita Kazuki , Yamamoto Nobuyuki
Published: March 2014

Photoluminescence excitation (PLE) spectra have been examined for the first time on CuGaSe2 crystals using a tunable laser as an excitation source. Free exciton peaks of PLE spectra are clearly observed on crystals grown by the iodine vapor transport method (IT) and the traveling heater method (THM). For IT crystals the activation energies for donor levels and acceptor levels are estimated to 100 meV and 65 meV, respectively, whereas for THM crystals containing 1 at% of In atoms, 80 meV and 50 meV, respectively.
Homogeneity Ranges, Defect Phases and Defect Formation Energies in AIBIIICVI
2 Chalcopyrites (A = Cu; B = Ga, In; C = S, Se)
Authors: Fiechter Sebastian , Tomm Yvonne , Diesner Klaus , Weiss Tilmann
Published: March 2014

Employing the generalization of cavity model, formation energies of point defects were calculated and compared with the self-doping behaviour and homogeneity regions of Cu BIIIC2
VI chalcopyrites. Electrical compensation as well as large off-stoichiometries, observed in chalcopyrites, can be explained by this data introducing defect arrays of VCu, VC
VI BIII
Cu and CuB
III, especially VCu - BIII
Cu pairs. The ratio of defects in such pairs can be adjusted via partial pressures of chalcogen vapor species during crystal or layer growth causing p- or n-type doping. Since the homogeneity range of CuGaSe2 along the binary cut Cu2Se - Ga2Se3 was claimed to be of about 10 mole% Ga2Se3, which is beyond the size that can be explained by point defect formation energies, the phase diagram was carefully investigated in the range from 40 to 60 mole% using Differential Thermal Analysis (DTA). The solidified samples were structurally analysed by X-Ray Diffractometry (XRD). A Cu-rich chalcopyrite phase of composition Cu1.015Ga0.956Se2 was found showing a maximum in the liquidus at 1100°C and two solid-solid phase transitions at 1056 and 987°C, respectively. Three further Ga-rich chalcopyrite defect phases were identified by careful analysis of the liquidus and the course of lattice constants vs. composition curve. As a result, the wide homogeneity range is discussed as a sequence of ordered defect chalcopyrites.
Solid Solubility in Mixed Spinels ZnMIII
2O4 - Zn2SnO4 (MIII=Al, Ga)
Authors: Garbato Andrea , Garbato Lelio , Marrocu Pasqualino , Sedda Franca
Published: March 2014

We are presenting a study on synthesis process and structural characterisation of quaternary oxides lying along the spinel line ZnMIII
2O4-Zn2SnO4 (MIII=Al, Ga) in the pseudo ternary system ZnO-MIII
2O3-SnO2. Results indicate that in the Ga-containing system the intermediate phases form a continuous series of solid solution with the cubic spinel structure. In the Al-containing system the solid solution apparently decomposes by cooling from 1550 K. The possible influence of bond distances on the behaviour of these systems is briefly discussed.
Differential Thermal Analysis of CuInxGa1-xSe2 and CuInxAl1-xSe2
Authors: Rincon Carlos Alberto Durante , Leon Máximo , Mora María Teresa
Published: March 2014

Phase diagrams for the systems CuInxGa1-xSe2 and CuInxAl1-xSe2 have been sketched using Differential Thermal Analysis (DTA) measurements performed on powder samples sealed in evacuated quartz ampoules. Coexistence of chalcopyrite, zincblende and liquid phases is proposed for both systems. In addition, the phase transformation enthalpies have been obtained from the DTA curves using an accurate numerical procedure that takes into account the heat capacity change during transformation.
Thermoelectric Properties of Some Phosphide Skutterudite Materials
Authors: Watcharapasorn Anucha , Demattei Robert C. , Feigelson Robert S. , Caillat Thierry , Borshchevsky Alexander , Snyder G. Jeffiey , Fleurial Jean-Pierre
Published: March 2014

The synthesis and thermoelectric properties of CoP3, CeFe4P12 and CeRu4P12 have been investigated. These compounds were made by recrystallization from Sn flux. The samples were analyzed by x-ray diffraction and electron microprobe analysis for phase purity. Electrical resistivity and Seebeck coefficient measurements showed that all three compounds are p-type semiconductors, in agreement with theoretical predictions and previous literature results. The large difference between the thermal conductivity of the binary and filled compounds can be primarily attributed to the additional phonon scattering by Ce atoms rattling inside the empty cages. The properties of the phosphide compounds are compared to their antimonide analogs and discussed in order to obtain further insights into the transport properties of skutterudite materials. Guidelines for optimizing thermoelectric properties of this class of compounds are also provided.
High Pressure X-ray Diffraction Study on Phase Transitions of CuInTez2
Authors: Diaz M. C. , Chalbaud L. M. de , Martin J. M. , Tinoco T. , Sagredo V.
Published: March 2014

CuInTe2 is a ternary semiconductor that crystallize in the chalcopyrite structure of space group I4̄2d. X-ray diffraction measurements up to 30 GPa were carried out on this material at the energy dispersive station DW11 of the LURE-Orsay, France. A phase transition was observed at 5.9 GPa and this high pressure phase have been indexed as cubic NaCl-type estructure. The bulk moduli are 62 GPa for the chalcopyrite phase and 85 GPa for the cubic phase. The volume reduction at the transition pressure is about 9.8 %
Electrical Properties of Mixed Phase CuInSe2-Cu2In4Se7 Bulk Crystals
Authors: Eisener Bernd , Wolf Dietrich , Müller Georg
Published: March 2014

Mixed phase bulk crystals containing the chalcopyrite CuInSe2 (α-phase) and the defect-chalcopyrite Cu2In4Se7 (β-phase) are prepared and electrically characterized. The crystals are solution grown, using InSe as a solvent and the volume fraction η = α/phase/(α-phase+β-phase) of the participant phases is determined by quantitative x-ray powder diffraction. The crystals are electrically characterized regarding the volume fraction η. The η-dependent development of the carrier density clearly shows, that α-phase chalcopyrite CuInSe2, grown from InSe solutions, is n-type conductive and heavily compensated.
Preparation of Zn Doped Cu(In,Ga)Se2 Thin Films by Physical Vapor Deposition
Authors: Nishiwaki Shiro , Satoh Takuya , Hashimoto Yasuhiro , Shimakawa Shin-ichi , Hayashi Shigeo , Negami Takayuki , Wada Takahiro
Published: March 2014

Cu(In,Ga)Se2 (CIGS) surface was modified with Zn doping using vacuum evaporation. The substrate temperature of CIGS films and exposed time during the deposition was changed to control the distribution of Zn in the CIGS films. The diffusion of Zn in CIGS film was observed at substrate temperature of over 200°C. The solar cell fabricated using the CIGS film modified with Zn showed an efficiency of 13.9 %, an open circuit voltage of 0.576 V, a short circuit current density of 34.9 mA/cm2, and a fill factor of 0.692. The effects of the amount and distribution of Zn on the performance of CIGS solar cells are discussed.
Characterization of Cu(In,Ga)Se2 Thin Films Prepared by Thermal Crystallization Using Two Kinds of Heating Rate
Authors: Yamaguchi Toshiyuki , Yamamoto Yukio , Yoshida Akira
Published: March 2014

Cu(In,Ga)Se2 thin films were prepared by thermal crystallization combining two heating rates, which were 1°C/min from room temperature to 200°C and subsequently 4°C/min above 200°C, and characterized. The crystallized thin films were transformed into single phase chalcopyrite Cu(In,Ga)Se2 above 400°C. The splitting of 112 diffraction line was observed in the XRD patterns for Cu(In,Ga)Se2 thin films treated in the range of 400-550°C, indicative of the graded Ga concentration. The resistivity and the mobility of Cu(In,Ga)Se2 thin films were increased with increasing the annealing temperature. The band gap was estimated 1.34 eV close to the optimum range for solar energy conversion.
Incorporation of the doping elements N and P in CuInS2 thin films by co-evaporation
Authors: Scheer R. , Luck I. , Kanis M. , Matsui M. , Watanabe T. , Yamamoto T.
Published: March 2014

The incorporation of doping elements N and P as well as the impact of these elements on electrical properties of co-evaporated CuInS2 thin films are studied. We show that by using a radical source, nitrogen can be incorporated up to a density of 6×1019 cm-3. N possibly replaces S atoms and should act as an acceptor. An increase in electrical conductivity, however, is not verified. The concentration of P atoms is below the detection limit of 2×1019 cm-3. Hence no clear evidence for phosphorus incorporation is achieved.
Growth and Band-gap Estimation of CuIn3Se5 Polycrystalline Thin Films
Authors: Hayakawa Akinori , Mizutani Tsutomu , Nakanishi Hisayuki , Chichibu Shigefusa F.
Published: March 2014

Structural and optical properties of nonstoichiometric CuIn3Se5 polycrystalline thin films were studied. From the XRD measurments, the lattice parameters a and c were shown to decrease with increasing In content. The result suggests that the number of Cu vacancies increase with In content. The band-gap energy increased from 1.20 to 1.25 eV with increasing In content from In/(Cu+In)=73 to 77 %. This may be caused by weakening of Sep-Cud hybridization due to substitution of VCu and/or InCu for Cu, which might lower the valence band energy maximum.
Characterization of CuGaSe2 Thin Films Prepared by RF Sputtering from Binary Compounds
Authors: Yamamoto Yukio , Yamaguchi Toshiyuki , Yoshida Akira
Published: March 2014

CuGaSe2 thin films were prepared by rf sputtering from binary compounds (Cu2Se and Ga2Se3). EPMA results showed that film composition was varied with changing the mixing ratio `x' (x = [Cu2Se]/[Ga2Se3]). The thin film sputtered from the target with the mixing ratio of x=4.5 had a single phase chalcopyrite structure. In this case, CuGaSe2 thin films showed higher optical absorption coefficient and a direct band gap of 1.7 eV.
High Substrate-Temperature (450–600°C) Fabrication of CuIn(S,Se)2 Thin Films Using Hybrid Reactive Sputtering/Sulfurization Method
Authors: Chen Kun-Hong , Cheng Yu-Han , Tseng Bae-Heng , Hwang Huey-Liang
Published: March 2014

CuInSe2, CuInS2, CuGaSe2, CuGaS2 and their multinary alloys are promising for applications in photovoltaic devices. The fabrication of I-III-IV2 thin films beyond the conventional multi-source deposition have become extremely demanding for the large scale solar modules development. Reactive sputtering and sulfurization are among the best choices that have many intrinsic advantages for very large-areas. In this work, the depositions of CuIn(S,Se)2 thin films were carried out by hybrid sputtering/sulfurization method with Culn and CuInSe2 targets and the reactive gas, H2S. The characterization results show that a nearly stoichiometric CuInSe2 thin film could be obtained with or without a post H2S annealing. The Se/S ratio of CuIn(S,Se)2 thin films could be controlled with the different growth conditions. It shows that this hybrid method could be a feasible method to fabricate the large-area I-III-VI2 based high efficiency solar cells.
Phase Formation and Growth Mechanism of Ternary and Quaternary Cu(In,Ga)S2 Chalcopyrite Layers
Authors: Víllora Encarnación García , Fiechter Sebastian , Klenk Reiner , Lux-Steiner Martha Ch.
Published: March 2014

Thin film solar cell absorbers of nominal composition CuIn1-xGaxS2 for(0 < x < 0.5) were prepared by sequential evaporation of the metals and by subsequent annealing in either a sulfur or a H2S atmosphere. The film formation was investigated experimentally and elucidated by thermochemical calculations.
In-situ Monitoring of Phase Formation in CuInSe2 Thin Films
Authors: Wolf Dietrich , Müller Georg
Published: March 2014

Reactive annealing of Cu-In-Se thin film stacks is an attractive technique to produce large area CIS absorbers for photovoltaic applications. In order to get detailed information on the mechanisms of CIS formation Thin Film Calorimetry has been used for in-situ monitoring the reaction pathway during heating. In a first step, the behaviour of binary In-Se and Cu-Se thin films is summarised as a prerequisite for the interpretation of the calorimetry spectra of ternary layers. It is shown in a second step that the information obtained exsitu by X-ray diffraction deviates from the results of the in-situ technique with respect to rapid re-transformation of Cu-selenides during cooling. The use of these complementary methods leads to a model describing qualitatively the reaction pathway of CIS-formation for a constant heating rate. In the temperature range above 380°C CIS growth proceeds by the reaction of Cu2-xSe and InSe in presence of a peritectic Se-rich liquid. This mechanism suggests an analogy with models for CIS growth during physical vapour deposition.
Growth and Structure of In2Se3 and CuInSe2 Thin Films
Authors: Grigorov Sergey N. , Kosevich Vadim M. , Kosmachev Sergey M. , Savitsky Boris A. , Taran Anton V.
Published: March 2014

The investigation of phase transformations in indium selenide films during step selenization processes at 200, 350, 400 and 580°C was carried out. It was found that the phase transformations in films are accompanied by recrystallization processes which promote the growth of large crystalline films. Large-crystalline In2Se3 films are formed at last stage of selenization. Superstructure reflections which can be explained by odered vacancy arrays and therefore indicated a Se deficiency in In2Se3 grains were observed. Large crystalline CuInSe2 films have been grown on the base of the In2Se3 films.
Formation of CuInS2 in Spray Pyrolysis Process as Simulated by Thermal Analysis
Authors: Krunks Malle , Leskelä Tuula , Niinistö Lauri
Published: March 2014

The formation of CuInS2 thin films was studied by simulating spray pyrolysis conditions through thermogravimetric experiments performed both in air and helium. The solid precursor containing Cu, In, Cl, thiourea and H2O in a ratio 1:1:5:3:2 was obtained by evaporation of the aqueous spray pyrolysis solution. Thermal degradation of the precursor was found to be a complex process where CuInS2 is formed as the main crystalline product already at 250 °C in both atmospheres. In air, however, InOCl is also readily formed and at 650 °C In2O3 and CuO appear as final products. In thin films prepared at 320 °C the Cu:In:S ratio is correct but there are 1.5 wt.% Cl residues as shown by RBS and EDS analyses, respectively.
Characterization of Cu-In-Se and CuIn(SxSe1-x)2 Thin Films Prepared by Chemical Spray Pyrolysis
Authors: Terasako Tomoaki , Uno Yuji , Inoue Seiki , Shirakata Sho , Kariya Tetsuya , Isomura Shigehiro
Published: March 2014

Polycrystalline thin films of Cu-In-Se compounds and CuIn(S
x
Se1-x
)2 alloys have been grown on glass substrate by chemical spray pyrolysis (CSP). Films are characterized by X-ray diffraction, optical absorption and Raman measurements. The Cu-In-Se films with In/(Cu+In) >0.57 exhibit a characteristic Raman peak. The optical bandgap energy of the Cu-In-Se film is approximately 1.22 eV for In/(Cu+In)<0.67, and it increases from 1.22 to 1.36 eV as the In/(Cu+In) ratio increases from 0.67 to 0.75. Controllability of alloy composition of CuIn(S
x
Se1-x
)2 films is also discussed.
A High Resolution X-ray Diffraction and TEM Study of the CuxSe Surface Phase of Cu-rich CuInSe2
Authors: Fons Paul , Niki Shigeru , Uchino Manabu , Yamada Akimasa , Oyangi Hiroyuki
Published: March 2014

Cu-rich CuInSe2 is known to phase segregate into a surface phase of CuxSe and near-stoichiometric CuInSe2. In both epitaxial CuInSe2 films grown by molecular beam epitaxy as well as in polycrystalline CuInSe2 films, growth under Cu-rich conditions is known to lead to improved crystalline quality with significantly lower concentrations of point and extended defects. To examine details of the interaction of CuxSe and the CuInSe2 matrix, we have grown CuInSe2 films under Cu-rich growth conditions on GaAs(001) substrates by molecular beam epitaxy at 450°C and have investigated the as-grown films by high resolution x-ray diffraction and transmission electron microscopy. In addition the behavior of the CuxSe surface phase under thermal effects has also been investigated.
Molybdenum Diffusion in CuInSe2 Thin Films
Authors: Dzhafarov Tayyar , Sadigov Magomed , Cingi Emel , Bacaksiz Emin , Caliskan Murat
Published: March 2014

Molybdenum diffusion in CuInSe2 (CIS) films was investigated in the temperature range 240-520°C using the energy-dispersive X-ray (EDX) and resistivity techniques. CuInSe2 thin films were deposited by single-source evaporation on glass and molybdenum-covered glass substrates. The temperature dependence of Mo diffusion coefficient is described by equation D=1.3×10-8exp
(-0.53/kT). It is shown that the diffusion doping of p-type CIS by molybdenum is accompanied by the significant decrease of resistivity. The observed results of the diffusion and electrical measurements are attributed to migration of Mo in the polycrystalline CIS films by means of both along intergrain surfaces and into grains.
Preparation of CuAlSe2/CuGaSe2 Heterostructures by Molecular Beam Epitaxy
Authors: Shirakata Sho , Watanabe Hiromasa , Terasako Tomoaki , Isomura Shigehiro
Published: March 2014

Epitaxial layers of CuGaSe2 and CuAlSe2 have been grown on the GaAs(l00) substrate by means of molecular beam epitaxy (MBE) for the purpose of the preparation of hetero- and quantum structures. The c-axis oriented epilayers have been grown and the layers were characterized by photoluminescence (PL) and photoreflectance. The double heterostructures, CuAlSe2/CuGaSe2/CuAlSe2, with various well layer thicknesses (l

z
) have been prepared. The PL measurement showed that the Cu(Al
x
Ga1-x
)Se2 alloy is formed at the CuAlSe2/CuGaSe2 interface. The feasibility of preparation of the quantum structure using the CuAlSe2/CuGaSe2 system is discussed.
Metalorganic Molecular Beam Epitaxy of CuAlSe2, CuGaSe2 and CuInSe2 on GaAs Substrate
Authors: Shirakata Sho , Terasako Tomoaki , Isomura Shigehiro
Published: March 2014

Epitaxial layers of CuGaSe2, CuAlSe2 and CuInSe2 have been successfully grown on the GaAs(100) substrate by means of metalorganic molecular beam epitaxy (MOMBE). Cyclopentadienylcoppertriethylphosphine (CpCuTEP), triethygallium (TEGa) , triisobuthylalminium (TIBAl), triethylindium (TEIn) and selenium have been used for precursors of Cu, Ga, Al, In and Se, respectively. Epilayers have been examined by X-ray diffraction, scanning electron microscopy, electron-probe micro analysis, Raman spectroscopy, photoluminescence and photoreflectance. The c-axis -oriented epilayers exhibiting good optical properties have been grown for both CuGaSe2 and CuInSe2. In spite of the poor reproducibility of the MOMBE growth of CuAlSe2, the epitaxial layer exhibiting the edge-emission at 2.64 eV at 8 K has been grown.
Twin formation in Cu-Ga-Se films grown by molecular beam epitaxy under Ga-excess conditions
Authors: Yamada Akimasa , Fons Paul J. , Niki Shigeru , Oyanagi Hiroyuki
Published: March 2014

Cu-Ga-Se films were grown on (001)-oriented GaAs substrates by molecular beam epitaxy. It was found that large number of twins were introduced into the films when they were grown to Ga-excess compositions while there was no trace of twins in films grown under Cu-excess conditions. Twins appeared dramatically in the composition region of 1>[Cu]/[Ga]>0.97 from zero to a nearly constant volume fraction. The volume fraction of twins increased monotonously with increasing film thickness. The twin type was rotated on {112} planes. The volume fraction of twins was more than one hundred times larger for (112)/(1̄1̄2) than for (11̄2)/(1̄12). The twin domains showed a certain amount of shear distortion. These investigations suggest that twin formation is not a consequence of lattice mismatch but an effect of growth mechanisms. The nucleation of the twin is attributable to anion configuration change by bond switching caused by cation defects in the growth front concerning (112)/(1̄1̄2).
Disappearance of the surface Cu-Se second phase during post-growth annealing of CuInSe2 epitaxial films grown under excess Cu-flux conditions
Authors: Uchino Manabu , Niki Shigeru , Ai Yousuke , Fons Paul J. , Yamada Akimasa , Sakaf Natsuko , Yokokawa Harumi , Oyanagi Hiroyuki , Chichibu Shigefusa F. , Nakanishi Hisayuki
Published: March 2014

When CuInSe2 samples grown under excess Cu-flux conditions were annealed at temperatures higher than 500°C (Ta>500°C), sample resistivity was observed to dramatically increase concurrently with a shift in the Cu/In ratio to a slightly In-excess composition (Cu/In∼0.9). We have already reported that KCN-etching of CIS grown under Cu-flux excess conditions causes the Cu/In ratio to revert to a slightly In-excess composition. The above results suggest that the Cu-Se second phase of CIS epitaxial films grown under Cu-flux excess conditions disappears as a result of annealing at temperatures Ta>500°C. Interdiffusion between CIS and GaAs substrate was observed for samples annealed at temperatures Ta>500°C. The results from other observations indicate that Cu-Se second phase acts via an unknown mechanism to enhance interdiffusion between the CIS layer and the GaAs substrate.
Observation of n- and p-Type Conduction of Site-selectively Zn-doped Epitaxial Layers of CuGaS2
Authors: Kumakura Hiromichi , Iida Seishi , Nakagaki Yuichiro , Uchiki Hisao , Matsumoto-Aoki Tamao , Kato Ariyuki
Published: March 2014

Site-selective Zn doping for vapor phase eptaxial CuGaS2 layers on GaP substrates was tried by adding Zn vapor to each metal source supply period under completely separated alternate source feeding condition with the sources of CuCl, dietylegalliumchloride, and H2S. For the case of simultaneous Ga and Zn supply, the grown layers were found to be of n-type, while for the case of simultaneous Cu and Zn supply the layers were of p-type. The formation of a p-n homo-junction was demonstrated using these p- and n-type layers, and electroluminescence from this p-n junction was observed under pulsed forward voltage application at 77 K. This is believed to be the first successful report of conduction type control of CuGaS2 by impurity doping.
Defect Structure of Heteroepitaxial Zn2-2xCuxInxS2 Layers Grown by Pulsed Laser Deposition on (111) Si, (001) Si and (001) GaP Substrates
Authors: Wagner G. , Oppermann D. , Schmitz W. , Bente K. , Lenzner J. , Lorenz M.
Published: March 2014

Zn2-2xCuxInxS2 (ZCIS) films might be attractive for absorbers in solar cells (band gap variation from Eg(ZnS) = 3.67 eV to Eg(CuInS2) = 1.53 eV at room temperature). Therefore, we have grown ZCIS on (001)GaP, (001)Si and (111)Si substrates at 500°C by pulsed laser deposition (PLD). Epitaxial growth on (001) GaP substrates could be proved for all compositions between ZnS and CuInS2. However, there is a striking asymmetry in twin nucleation that occurs for cubic ZCIS (CuInS2 content less than 22 mol-%) preferably on the (1̄1̄1) and (111) planes of the [1̄10] zone. In addition, beside the dislocations lying in-clined to the interface, perfect 60° misfit dislocations coexist that align parallel to [110] and [1̄10] , having b=1/2<011> and {111} slip planes inclined to the interface. Additional Cu- and/or In-sulfides could not be detected in the monocrystalline films. CuAu-I type ordering was observed for CuInS2-rich compositions as Zn0.22Cu0.46In0.32S, Zn0.044Cu0.544In0.412S and pure CuInS2 only. On (001) Si the films appear to be polycrystalline for all compositions between Zn0.2Cu0.4In0.4S and Zn0.62Cu0.19In0.19S. At Zn0.7Cu0.15In0.15S there is the transition between poly- and monocrystalline growth, i.e. the range of monocrystalline growth is strongly restricted to the lattice matched position. In these layers twins have been nucleated on all four inclined {111} planes. On chemically treated (111) Si the films grew epitaxially for compositions 0.1 ≤ x ≤ 0.7. They are monocrystalline, but consist of polysynthetically twinned column-like grains which are precisely oriented to the (111) Si sub-strate. Coherent Σ=3{111} twin boundaries exist parallel to the interface and incoherent Σ=3{112} grain boundaries are for-med perpendicular to it. Perfect dislocations that lie along <110> directions and parallel to the interface envelop the colums to form a dislocation network like a honeycomb. The films become polycrystalline for compositions x > 0.7. On non-treated (111) Si substrates, similar to the deposition on molybdenum-coated glass, the ZCIS films are polycrystalline, but a distinct <111> texture exists. Extended defects have been produced inside both the GaP and chemically treated Si substrates due to the preferred Cu out-diffusion from the layer. In the GaP substrates a Cu3P phase is formed but within the Si substrates amor-phisized regions occur exclusively. With increasing ZnS content the propensity to form these defects decreases appreciably.
Epitaxial Growth of Ag(Al,Ga)S2 on GaAs(100) Substrate by Multisource Evaporation
Authors: Tsuboi Nozomu , Kurasawa Masaki , Kobayashi Satoshi , Oishi Koichiro , Kaneko Futao
Published: March 2014

Epitaxial growth of Ag(Al,Ga)S2 layers with the [Al]/([Al]+[Ga]) ratio less than 0.3 was demonstrated on GaAs(100) substrate through multisource evaporation. The oriented domain with the a-axis normal to the substrate disappeared by stoichiometry control of the [Ag]/([Al]+[Ga]) ratio. The 180°-rotated {112} twin crystal regions slightly appeared in the range of [Al]/([Al]+[Ga])>0. Reflectance anomaly spectra due to the free exciton were observed in the layers.
Epitaxial Growth of ZnSe Films on CuGaSe2 Films
Authors: Tanaka Masahiro , Nabetani Yoichi , Kato Takamasa , Matsumoto Takashi
Published: March 2014

ZnSe epitaxial layers are grown on CuGaSe2 layers on GaAs(l00) substrates by MBE. The ZnSe/CuGaSe2/GaAs(100) structures are characterized by X-ray diffraction (XRD) and photoluminescence (PL) measurements and transmission electron microscopy (TEM). ZnSe layers are grown coherently on CuGaSe2 layers that were grown coherently on GaAs substrate. The properties of ZnSe layer are sensitive to the degree of lattice relaxation of underlying CuGaSe2 epitaxial layer. Cu-acceptor bound exciton emission are clearly seen in PL spectra from ZnSe, though Cu-related deep level emissions dominate the spectra.
Effect of Post-oxidation Annealing on GaAs Oxides Grown by Liquid Phase Chemical-Enhanced Technique
Authors: Chou Dei-Wei , Lou Ruey-Fa , Wang Hwei-Heng , Wang Yeong-Her , Houng Mau-Phon
Published: March 2014

The characteristics of GaAs native oxides grown by liquid phase chemical-enhanced oxidation technique followed by post-oxidation annealing are investigated. The refractive index of as-grown oxide films increases with increasing As/Ga ratio, which depends on many process factors such as temperature, oxidizing time and pH values of the aqueous solution. Regardless of high or low refractive index as-grown oxide films, their refractive index approaches 1.8 after post-oxidation annealing. A model is proposed to explain this observation. Crystalline β-Ga2O3 is present in the oxide when the oxide is annealed at temperatures above 600°C and when the annealing time exceeds 6h. The shrinkage of oxide film thickness has been found. 30% enhancement of breakdown field strength and an order of magnitude of reduction of leakage current have been also obtained.
Electronic Structures and Structural Transition Temperature of Shape Memory Alloys Ni2+xMn1-xGa
Authors: Sugimura Shinichi , Ishida Shoji , Fujii Shinpei , Asano Setsuro
Published: March 2014

The Heusler type alloys Ni2+xMn1-xGa are shape memory alloys and the phase transition temperature between a tetragonal and a cubic structure becomes higher with increasing Ni composition. To investigate the characteristic properties, the electronic structures of Ni2+xMn1-xGa were calculated for the cubic and the tetragonal structure. We found that the total energy difference between the cubic and the tetragonal structure becomes larger with increasing x, that is, the tetragonal structure becomes more stable. This tendency suggests the fact that the phase transition temperature becomes higher by substituting Mn with Ni in Ni2+xMn1-xGa.
Computer Modeling of Defects and Surfaces in Advanced Perovskite Ferroelectrics
Authors: Borstel Gunnar , Kotomin Eugene A. , Eglitis Roberts I. , Heifets Eugene
Published: March 2014

The (110) surface relaxations are calculated for SrTiO3 and BaTiO3 perovskites. The positions of atoms in 16 near-surface layers placed atop a slab of rigid ions are optimized. Strong surface rumpling and surface-induced dipole moments perpendicular to the surface are predicted for both the O-terminated and Ti-terminated surfaces. Calculated optical properties of basic point defects – F-type centres and hole polarons – in KNbO3 are used for the interpretation of available experimental data.
Electronic Band Structure and Bonding Nature of Ternary Compound Ni1/3TiS2
Authors: Motizuki Kazuko , Suzuki Naoshi
Published: March 2014

The nature of bonding in intercalation compound Ni1/3TiS2 is studied by calculating the bond orders on the basis of self-consistent APW band calculations. It is found that the 3dγ states of Ni atoms make covalent-like bonds with the S 3p states while the 3de states of Ni and Ti atoms form bonding and antibonding bands. The results are discussed in connection with the recent photoemmission experiments.
Valence Band Properties of Relaxed Ternary Group IV Semiconductor Alloys
Authors: Lin Chung-Yi , Liu Cheewee , Chen Wei-Zhu
Published: March 2014

We report calculations of valence band properties of ternary group IV semiconductor alloys Si1-x-yGexCy. The linear combination of atomic orbitals' Hamiltonian matrix with spin-orbit interaction terms is incorporated to obtain the analytic expression for the valence band structure for all the calculations. The anisotropy parameter Γ of the valence band, the density-of-state effective masses (d.o.s. m*) of holes are calculated as functions of alloy concentration x and y. The cyclotron resonance effective masses (CR m*) of holes are also calculated as a function of x, y, and the angle θ between the static magnetic field in (110) plane and [001] axis. A sharp rise of the values of Γ, d.o.s. m*, and CR m* for fixed θ for heavy holes are found as the alloy approaches pure diamond while the light hole values vary moderately over all the alloy concentrations. Our calculations provide a strong evidence that the interaction between the split-off hole band and the heavy hole band is responsible for the anomalous behavior of the heavy holes properties.
Electronic Band Structure of Li2CuO2 and Application to Battery Electrode
Authors: Tanaka Norikazu , Suzuki Masakatsu , Motizuki Kazuko
Published: March 2014

The electronic band calculations of Li2CuO2 and Li-deintercalated CuO2 have been performed by the fullpotential linearized augmented plane wave (FLAPW) method within the local spin density approximation (LSDA). It is found that Cu 3d states are strongly hybridized with O 2p states and that Li atom is almost ionized. On the basis of the total energy calculations, we have studied the applicability of Li2CuO2 as a cathode material of rechargeable Li-battery. The average battery voltage in the chemical reaction, Li2CuCO2 → CuO2 + 2Li, is estimated. The structural stability is also discussed.
Electronic Structure and Stability of Spinel Oxides
Authors: Wei Su-Huai
Published: March 2014

Using first-principles band structure method, we have calculated the total energies, the structural parameters, and the band gaps of the closed-shell A
I
I
B2

I
I
I
O4 and A
I
V
B2

I
I
O4 spinel oxides in both normal and inverse spinel structures. We find that a correct description of the internal atomic relaxation is crucial to predict the stability of the spinels. The preference of cations with delocalized valence d states (e.g., Zn) to form covalent tetrahedral bonds also plays a significant role in determining the cation distribution in the spinels. Furthermore, we find that the band structures of these spinel compounds depend strongly on the cation distribution. For most of the spinels studied here, the calculated band gaps for the inverse spinels are smaller than the corresponding normal spinels.