- Layered Post-Transition-Metal Dichalcogenides (X?M?M?X) and Their Properties
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AIIIBVIchalcogenides are an interesting group of layered semiconductors with several attractive properties, such as tunable band gaps and the formation of solid solutions. Unlike the typically sandwiched structure of transition-metal
- Luxa, Jan,Wang, Yong,Sofer, Zdenek,Pumera, Martin
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- Thermodynamic assessment of phase diagram and concentration–temperature dependences of properties of solid solutions of the GaS–GaSe system
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Experimental data for the system GaS–GaSe were subjected to a critical assessment using the differential thermal analysis (DTA), X-ray diffraction and thermodynamic approach. The physicochemical and thermodynamic parameters of the GaS and GaSe compounds were taken from the literature and the authors’ previous assessment, respectively. To reach a self-consistent thermodynamic description for the constituent phases in the system, the experimental on the melting point, the composition of the minimum point and the univariant curves of the GaS–GaSe system were reassessed. An ideal solution model for the liquid, which included non-molecular compounds, was employed to represent phase diagram and Gibbs free energy of mixing data. To make our investigation on invariant points more accurate, a new and complementary experimental DTA determination regarding the compounds was carried out. We clarify the temperature and melting enthalpy of the compounds that are needed to calculate thermodynamic parameters of the system. Our thermodynamic description, compatible with experimental data for the GaS–GaSe system, resulted in an agreement between the calculated and experimental data. The temperature–concentration dependences of the properties (thermodynamic functions, the width of the forbidden band, the heat capacity) of solid solutions of the GaSe–GaS system are established. Optical value was obtained on single-crystal samples. Solid solutions of the GaSe 1 - xS x compounds were grown by the Bridgman method by directional crystallization.
- Asadov,Mustafaeva,Mammadov
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- Polymorphism of Ga//2S//3 and Phase Diagram of Ga-S.
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The monoclinic form ( alpha prime ) of Ga//2 S//3 is exactly stoichiometric and is stable from room temperature to the melting point. The hexagonal form ( alpha ) and the wurtzite-type form ( beta ) exist only at high temperature, above 885 degree C; their formation requires a very small sulfur deficiency and, consequently, they are obtained in the presence of GaS. The passage from the hexagonal form to the wurtzite form is progressive and depends on the proportion of GaS. The blende-type form is clearly substoichiometric (GaS//1//. //3//8) and exists only in a small temperature range. The phase diagram is described from GaS//0//. //9//6 to GaS//1//. //5//6.
- Pardo, M. P.,Tomas, A.,Guittard, M.
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- Structural and optical characterization of indium and gallium indium sulfide films prepared by modulated flux deposition
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Indium and gallium indium sulfide thin films were deposited on soda-lime glass substrates at 350°C, in a wide range of sulfur delivery conditions, by Modulated Flux Deposition (MFD). Indium sulfide films were highly crystalline β-In2S3 (tetragonal) with Eg = 2.68 eV. Depending on the availability of sulfur, gallium indium-poor sulfide films consisted on metal-rich hexagonal β-GaS layers or stoichiometric amorphous films with Eg = 3.0-3.3 eV. Finally, gallium indium-rich sulfide films formed a mixture of β-In2S3 and β-GaS that became near amorphous as more sulfur was supplied; a bandgap energy of E g = 2.44 eV was found.
- Sanz,Guillen,Gutierrez
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- Photoelectric studies of gallium monosulfide single crystals
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Photoconductivity (PC) studies were carried out on GaS single crystals prepared from melt by directional solidification. We studied the effect of light intensity, applied voltage on both the PC and the lifetime of carriers. The V-I characteristics and the
- Gamal,Azad
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- Syntheses, structures, and nonlinear-optical properties of metal sulfides Ba2Ga8MS16 (M = Si, Ge)
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Two new metal sulfides, Ba2Ga8MS16 (M = Si, Ge), have been synthesized by high-temperature solid-state reactions. They are isostructural and crystallize in the noncentrosymmetric space group P63mc (No. 186) with a = 10.866(5) ?, c = 11.919(8) ?, and z = 2 for Ba2Ga8SiS16 (1) and a = 10.886(8) ?, c = 11.915(3) ?, and z = 2 for Ba2Ga8GeS16 (2). Their three-dimensional frameworks are constructed by corner-sharing mixed (Ga/M)S4 (M = Si, Ge) and pure GaS4 tetrahedra, with Ba2+ cations filling in the tunnels. Compounds 1 and 2 are transparent over 0.42-20 μm and have wide band gaps of around 3.4 and 3.0 eV, respectively. Polycrystalline 2 displays strong nonlinear second-harmonic-generation (SHG) intensities that are comparable to that of the benchmark AgGaS2 (AGS) with phase-matching behavior at a laser irradiation of 1950 nm. Of particular interest, compound 2 also possesses a high powder laser-induced damage threshold of ~22 times that of AGS. The alternate stacking of the mixed (Ga/M)S4 (M = Si, Ge) tetrahedral layer with the pure GaS4 tetrahedral layer along the c axis and the alignment of these two types of tetrahedra in the same direction may be responsible for the large SHG signals observed.
- Liu, Bin-Wen,Zeng, Hui-Yi,Zhang, Ming-Jian,Fan, Yu-Hang,Guo, Guo-Cong,Huang, Jin-Shun,Dong, Zhen-Chao
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- Photoelectrical properties of layered GaS single crystals and related structures
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The photoconductivity of pure and Cu-doped layered gallium monosulfide (GaS) single crystals, and of Ni-GaS(Cu)-In and GaS(Cu)-ZnO structures, is investigated. The activation energies of surface states were found as 0.10 eV, 0.40 eV and 17 meV, ~400 meV for GaS and GaS(Cu), respectively. Cu acceptor levels are localized at 0.44 eV and 0.52 eV above the valence band of GaS. ZnO-GaS(Cu) heterojunctions show remarkable photosensitivity in the wavelength range of 250-700 nm.
- Caraman,Chiricenco,Leontie,Rusu
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- Structural investigations of glass ceramics in the Ga2S 3-GeS2-CsCl system
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Transparent glass ceramics have been prepared in the Ga2S 3-GeS2-CsCl pseudoternary system using appropriate heat treatment time and temperature. In situ X-ray diffraction at the heat treatment temperature and 133/su
- Ledemi, Yannick,Bureau, Bruno,Calvez, Laurent,Le Floch, Marie,Rozeì?, Mathieu,Lin, Changgui,Zhang, Xiang H.,Allix, Mathieu,Matzen, Guy,Messaddeq, Younes
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- Uniform and high-quality submicrometer tubes of GaS layered crystals
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GaS, group III-VI semiconductor compound, is known to possess a layered structure. In this letter, uniform and high-quality GaS submicrometer tubes have been synthesized via a simple high-temperature thermal reaction route. Each GaS tube is uniform in size, and has length up to tens of microns and outer diameter of ~200-900 nm; some of the tubes are partially filled with liquid metallic Ga rods. Photoluminescence spectrum reveals that the GaS tubes have two strong emission bands centered at ~585 and ~615 nm. Possible reaction processes and a rolling-up growth mechanism of as-grown GaS tubes were briefly discussed.
- Hu,Bando,Zhan,Liu,Golberg
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- Lattice vibrations of pure and doped GaSe
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The Bridgman method is used to grow especially undoped and doped single crystals of GaSe. Composition and impurity content of the grown crystals were determined using X-ray fluorescence (XRF) method. X-ray diffraction, Raman scattering, photoluminescence (PL), and IR transmission measurements were performed at room temperature. The long wavelength lattice vibrations of four modifications of GaSe were described in the framework of modified one-layer linear-chain model which also takes into consideration the interaction of the selenium (Se) atom with the second nearest neighbor gallium (Ga) atom in the same layer. The existence of an eight-layer modification of GaSe is suggested and the vibrational frequencies of this modification are explained in the framework of a lattice dynamical model considered in the present work. Frequencies and the type of vibrations (gap, local, or resonance) for the impurity atoms were calculated and compared with the experimental results.
- Allakhverdiev,Baykara,Ellialtio?lu,Hashimzade,Huseinova,Kawamura,Kaya,Kulibekov,Onari
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- Intramolecularly Coordinated Gallium Sulfides: Suitable Single Source Precursors for GaS Thin Films
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Our studies have been focused on the synthesis of N→Ga coordinated organogallium sulfides [L1Ga(μ-S)]3(1) and [L2Ga(μ-S)]2(2) containing either N,C,N- or C,N-chelating ligands L1or L2(Lsup
- ?i?ica, Tomá?,Světlík, Tomá?,Dostál, Libor,R??i?ka, Ale?,R??i?ka, Květoslav,Bene?, Ludvík,Němec, Petr,Bou?ka, Marek,Jambor, Roman
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- Synthesis, structural characterization, and physical properties of Cs2Ga2S5, and redetermination of the crystal structure of Cs2S6
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The reaction of CsN3 with GaS and S at elevated temperatures results in Cs2Ga 2S5. Its crystal structure was determined from single-crystal X-ray diffraction data. The colorless solid crystallizes in space group C2/c (no. 15) with V= 1073.3(4) ?3 and Z = 4. Cs2Ga2S5 is the first compound that features one-dimensional chains 1∞[Ga2S3(S 2)2-] of edge- and corner-sharing GaS4 tetrahedra. The vibrational band of the S22- units at 493 cm-1 was revealed by Raman spectroscopy. Cs2Ga 2S5 has a wide bandgap of about 3.26 eV. The thermal decomposition of CsN3 yields elemental Cs, which reacts with sulfur to provide Cs2S6 as an intermediate product. The crystal structure of Cs2S6 was redetermined from selected single crystals. The red compound crystallizes in space group P1 with V = 488.99(8) ?3 and Z = 2. Cs2S6 consists of S62- polysulfide chains and two Cs positions with coordination numbers of 10 and 11, respectively. Results of DFT calculations on Cs2Ga2 S5 are in good agreement with the experimental crystal structure and Raman data. The analysis of the chemical bonding behavior revealed completely ionic bonds for Cs, whereas GaS and SS form polarized and fully covalent bonds, respectively. HOMO and LUMO are centered at the S2 units.
- Friedrich, Daniel,Pielnhofer, Florian,Schlosser, Marc,Weihrich, Richard,Pfitzner, Arno
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p. 1811 - 1817
(2015/01/30)
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- RbGa3S5 und CsGa3S5 - Zwei neue strukturtypen
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The title compounds RbGa3S5 and CsGa 3S5 were synthesized by a solid state reaction starting from GaS, S and MN3 (M = Rb, Cs) as alkaline metal source. They crystallize in the space group P21/su
- Schlosser, Marc,Frettloeh, Vanessa,Deiseroth, Hans-Joerg
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- Hydrodesulfurization of dibenzothiophene and 4,6-dimethyl-dibenzothiophene: Gallium effect over NiMo/Al2O3 sulfided catalysts
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The influence of gallium on alumina-supported NiMo catalysts was investigated by correlating their physicochemical properties with the hydrodesulfurization (HDS) activity of model molecules. The Ga-γ-Al 2O3 supports were prepared by
- Altamirano, Efrain,De Los Reyes, Jose Antonio,Murrieta, Florentino,Vrinat, Michel
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p. 403 - 412
(2008/10/09)
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