Ag2SeGa2Se3 pseudobinary phase diagram

The pseudobinary Ag₂Se-Ga₂Se₃ phase diagram has been redetermined by differential thermal analysis, x-ray diffraction, and crystal growth studies. A new ternary phase, Ag₉GaSe₆, has been observed, and the phase boundaries of the solid solutions based on AgGaSe₂ and Ga₂Se₃ have been measured. The optical scattering observed in slow-cooled crystals of AgGaSe₂ is due to precipitates of a Ga₂Se₃-based solid solution, which has the approximate composition AgGa₇Se₁₁. The new Ag₂Se-Ga₂Se₃ diagram differs significantly from the one given by Palatnik and Belova but is qualitatively similar to the Ag₂S-Ga₂S₃ diagram recently reported by Brandt and Krämer.     

Li2Se-As2Se3 pseudobinary join in the Li-As-Se system and properties of LiAsSe2

Phase relations in the pseudobinary system Li₂Se-As₂Se₃ have been studied using physicochemical characterization techniques. The Li₂Se-As₂Se₃ system contains one chemical compound, LiAsSe₂, which melts congruently at 808 K and undergoes a polymorphic transformation at 737 K. Some physicochemical and electrical properties of the LiAsSe₂ compound have been studied.     

Cu-intercalated (Bi0.5Sb1.5Te3)0.96(Bi2Se3)0.04 single crystals

A procedure is described for converting the conductivity type (p → n) of single crystals of the Bi_0.5Sb_1.5Te₃-4 mol % Bi₂Se₃ solid solution via copper intercalation. Using this procedure, we have produced high-performance single-crystal n-legs with a room-temperature thermoelectric power α = ?200 μV/K. This procedure facilitates the fabrication of thermoelectric coolers because the same solid solution can be used to produce p-and n-legs, the only difference being the presence of copper in the n-legs. We have fabricated thermolements and determined their characteristics in the range 100–300 K.     

Growth of CuInSe2 and In2Se3/CuInSe2 nano-heterostructures through solid state reactions

In(2)Se(3) is an essential phase change material and CuInSe(2) is the fundamental basis of the copper-indium-gallium-diselenide (CIGS) solar energy material. In this paper, we demonstrate the feasibility to transform the phase change material to the solar energy material via the solid state reaction. The In(2)Se(3) nanobelts (NBs) were synthesized via the vapor-liquid-solid mechanism. The chemical composition and the optical properties were investigated by energy dispersive spectroscopy, X-ray photoelectron spectroscopy, and reflectance and photoluminescence spectra. In the in situ observation of the solid state reaction with Cu to form the CuInSe(2) NBs with ultrahigh vacuum transmission electron microscopy, we observed the In(2)Se(3)/CuInSe(2) transformation at atomic scale in real time. The progression of the atomic layer at the interface provided the pertinent information on the kinetic mechanism. In(2)Se(3)/CuInSe(2) nano-heterostructures were also obtained in the present investigation. The approach to the CIGS nanosolar cell was also proposed. This study shall be beneficial in the development of high-performance nanowire solar cells and nanodevices with In(2)Se(3)/CuInSe(2) nano-heterostructures.     

Growth and characterization of Ni substituted Bi2Se3 single crystals

Journal of Superconductivity and Novel Magnetism - In this article, we report synthesis and magneto-transport analysis of Ni substituted Bi2Se3 crystals. Phase purity and crystalline growth are...     

Growth of Sb2S3 single crystals by chemical vapour transport

Single crystals of antimony trisulfide have been grown by a chemical vapour transport technique using iodine as the transporting agent. Single crystals were obtained at a much lower temperature when antimony and sulfur in the stoichiometric ratio were taken as the source along with iodine. However when polycrystalline antimony trisulfide was taken as the source with iodine, single crystals were not obtained even at the melting point of Sb₂S₃. This observation has been explained on the basis of bond energy values.     

Sb2Se3管状化合物的制备和表征

用固相烧结法合成了管状Sb2Se3相变材料,并通过扫描电子显微镜（SEM）、X射线衍射仪（XRD）、透射电镜（TEM）、拉曼光谱仪（Raman）、热重分析（DSC）进行表征测试,结果表明成功制备出了正交晶系的Sb2Se3,计算所得晶格常数为a：11．6445A,b=11．792A,c=3．981A,;透射电镜结果说明Sb2Se3微米管晶体结构沿[001]方向择优生长;DSC测试Sb2Se3的熔点为624．5℃。同时本试验用固相烧结法制备了不同配比的Sb—Se材料,并用XRD和Raman表征测试了晶体结构.     

Phase equilibria in the Sb2Te3-Ag2Te system

The Sb₂Te₃-Ag₂Te system has been reinvestigated and the phase relations identified by various independent techniques. An intermediate phase with Ag₁₉Sb₂₉Te₅₂ composition, through incongruently melting can be obtained as a single crystal from melts enriched in Ag₂Te. It behaves as a solid solution of narrow homogeneity range (from 42 to 44% Ag₂Te).     

Phase diagram and thermoelectric properties of Ag3−x Sb1+x Te4 system

In order to obtain better thermoelectric performance in the composition domain should be stabilized, the phase diagram of the Ag_3–x Sb_1+x Te₄ system by varying the Ag:Sb ratio. The phase diagram is investigated using the differential thermal analysis and the powder X-ray diffraction techniques. The Seebeck coefficient and the electrical resistivity of the grown bulk crystals of the system are also measured. The phase diagram of the Ag_3–x Sb_1+x Te₄ system indicates that a mixed phase of AgSbTe₂ and Ag₂Te, which is expected to show higher thermoelectric performance, exists in a wide temperature range between 600 and 830 K at a composition of Ag_2.2Sb_1.8Te₄. The maximum of Seebeck coefficient for AgSbTe₂ (x = 1) is 0.73 mV/K at about 680 K. The thermoelectric performance is lowered by the compositional deviation from Ag:Sb:Te = 1:1:2.     

Optical properties of Sb2Se3 thin films

The optical constants (the refractive index n and the absorption index k) of Sb₂Se₃ thin films deposited at room temperature on quartz have been calculated in the wavelength range (5000–2000 nm) using a transmission spectrum. Both n and k were found to be practically independent on either time, up to 6 months, or the film thickness in the range of 102–760 nm. Beyond the absorption edge, the absorption is due to allowed indirect and direct transitions with energy gaps of 1.225 and 1.91 eV, respectively. The value of the optical gap depends on the annealing temperature. X-ray analysis showed that the prepared films at room temperature had amorphous structure while the films annealed at 200°C for 1 h were verified to be crystalline.     

Constitutional diagram and physical properties of TlSeInSe pseudobinary system

In this study a physicochemical analysis of the TlSe-Inse semiconductor system has been performed, and the existence of the TlInSe₂ compound with congruent fusion at 808 ± 5°C has been established. The electrophysical properties of Tl_xIn_1−xSe (0 ? X ? 1) system single-crystals of certain compositions have also been studied.     

多元醇法制备和表征Sb2Se3纳米线

以自制的NaHSe乙醇溶液为硒源,在PEG-400无水体系中采用多元醇法,在180℃生长10h制备了直径100～200nm,长度可达十几微米的纳米线.产物通过XRD、TEM、HRTEM、FESEM、EDS和UV-Vis等手段进行了表征,并研究了不同多元醇对产物形貌的影响.研究表明,PEG-400作为结构导向剂在制备一维Sb₂Se₃纳米线中发挥着至关重要的作用,并且无水环境为纳米晶的生长提供了更加纯净的条件,有利于制备高质量的纳米晶.     

Material properties and growth mechanism of CuInSe2 prepared by H2Se treatment of metallic alloys

A fundamental understanding of the mechanism of growth of CuInSe₂ is essential for the production of device quality material. In this contribution, the growth kinetics of thin film CuInSe₂ are investigated in the special case of H_2Se/Ar treated copper-indium metallic alloys. A systematic study was conducted in which the evolution of surface morphologies by scanning electron microscopy (SEM), formation of crystalline X-ray diffraction (XRD) and variation in film composition, energy dispersive spectrometry (EDS) were evaluated during various stages of selenization. SEM and XRD studies revealed a dramatic improvement in crystalline quality with increasing selenization temperature. SEM studies indicated a substantial increase in grain size (0.2m 1m) when the reaction temperature was increased from 150 °C to 450 °C. XRD studies revealed the presence of mostly binary phases (i.e. Cu₁₁In₉, InSe, In₆Se₇ and CuSe) at selenization temperatures up to 250 °C. CuInSe₂ was found to be the dominant phase at 350 °C and the film was almost completely converted to single phase material at 450 °C. The composition of the selenized films remained virtually unchanged in the temperature range between 150 °C and 350 °C. However, reaction of the metallic alloys to H_2Se/Ar at temperatures around 450 °C resulted in a significant loss of indium from the films and subsequently to an increase in the Cu/In atomic ratio. The variation in crystalline quality of the films during various stages of selenization was also clearly reflected by low temperature photoluminescence (PL) studies. Virtually no PL response was detected from samples selenized at low temperatures below 350 °C, compared to rather strong emissions from samples selenized at higher temperatures around 450 °C. Furthermore, a significant difference in PL response was detected from samples selenized at 350 °C and 450 °C, respectively. Comparative studies indicated the presence of a free-to-bound transition (at 0.992 eV) only in the case of samples selenized at 450 °C, which indicated that these specific point defects (V_ln) are created at high selenization temperatures. This observation is consistent with EDS results, indicating a substantial loss of In from samples selenized in this high temperature range. PL spectra from samples selenized at 350 °C were also characterized by a broad peak close to the band gap value, which was attributed to the presence of point defects associated with In-rich secondary phases. The improvement in crystalline quality with increased selenization temperatures and reaction periods was also clearly reflected by the reduction in the FWHM values of the PL peaks. The information gained from this study played an important role in the production of high quality films in our laboratories.     

Microhardness anisotropy on the (010) cleavage plane of single crystals of Bi2S3 and Sb2S3

Knoop microhardnesses were measured on the (0 1 0) cleavage planes of Bi₂S₃ and Sb₂S₃ single crystals for orientations from the [0 0 1] to the [1 0 0]. The [0 0 1] hardnesses were nearly twice the level of the [1 0 0] values, about 150-75 kg mm^–2. The experimental microhardness profile was consistent with the calculated effective resolved shear stress (ERSS) diagram for the (0 1 0) [0 0 1] primary slip system. The magnitude of the hardness appears to be related to the crystal structure, particularly the metal-sulphur chains parallel to the [0 0 1], the crystal growth direction.     

Electrical and optical properties of (Sb2Se3)2 (Sb2Te3)1 thin films

A study of the synthesized (Sb₂Se₃)₂ (Sb₂Te₃)₁ glassy system has been carried out, X-ray diffraction (XRD) patterns and differential thermal analysis (DTA) of the system studied were used to obtain an insight into the structural information. An investigation of the electrical and optical properties of (Sb₂Se₃)₂ (Sb₂Te₃)₁ thin films prepared by thermal evaporation having different thicknesses (89.2, 214, 223 nm) and annealing temperatures ranging from 300 to 473 K has been carried out. The effect of the thickness and heat treatment on the activation energy E for d.c. conductivity and the density of localized states at the Fermi level N(E_F) were carried out. The electrical conductivity measurements depend on the thickness and annealing temperature, and exhibit two types of conduction mechanisms. Optical absorption measurements have been made on as-deposited and annealed films for the investigated system. The optical transition was found to be indirect. The optical energy gap (E_opt) decreases with increasing thickness and annealing temperatures (below T_g). The corresponding band is approximately twice the conduction activation energy. This effect is interpreted in terms of the density of states model proposed by Mott and Davis. © 2002 Kluwer Academic Publisher