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Microstructural and vibrational properties of PVT grown Sb2Te3 crystals |
Konstantin A. Kokh 1,2,3, Victor Atuchin 4, Tatyana Gavrilova 4, Natalia Kuratieva 5, Natalia Pervukhina 5, Nikolai Surovtsev 6 |
1. Institute of Geology and Mineralogy SB RAS (IGM), Koptyuga ave., 3, Novosibirsk 630090, Russian Federation |
Abstract |
Antimony telluride, Sb2Te3, is a well-known thermoelectric material. Besides, for several recent years Sb2Te3 has been of great interest because of topological insulator properties. The formation of Sb2Te3 crystals with high-quality structure is of prime importance for comparative diagnostics of thin films and nanostructures fabricated by epitaxial and chemical synthesis techniques. In present study the high-quality Sb2Te3 microcrystals have been grown by physical vapor transport (PVT) method without using a foreign transport agent. High purity (4N) elementary Sb and Te were used in the growth experiment. An element charge of 15 g weighted in stoichiometric composition Sb:Te = 2:3 was fused in a quartz ampoule sealed at residual pressure ~10-4 bar. After synthesis the ampoule was inclined so that the melt was located in a high temperature part of the ampoule, while opposite end was under temperature below melting point of Sb2Te3. Duration of experiment was around 20 hours. Resulting PVT-grown plate-like crystals were up to 1 mm in size which may suppose relatively high vapor pressure of Sb2Te3 melt. Micromorphology of crystals formed on the ampoule walls was observed by SEM using LEO 1430 device. The microplates are well facetted. The phase composition of grown crystals has been identified by X-ray single crystal structure analysis. The X-ray intensity data were collected on a Bruker X8Apex CCD diffractometer using standard techniques (ω- and φ-scans of narrow frames) and corrected for absorption effects (SADABS). The structure was solved by direct methods and refined by full-matrix least-squares on F2 using the SHELX97 program set. The structure was defined in space group R-3m, a = 4.2706(1) Å, b = 30.4758(8) Ǻ, V = 481.35(2) Å3, Z = 3 (R = 0.029). Raman microspectrometry has been used to describe the vibration parameters of Sb2Te3 microcrystals. Raman scattering experiment was carried out in back-scattering geometry with a triple grating spectrometer TriVista 777 under illumination by a line of λ = 488 nm of argon laser at room temperature. An achromatic lens with the focal length of 40 mm was used for focusing laser beam and collecting scattering light, at the same time. The low laser power of 15 mW was used, and it was verified that, under the conditions of our focusing system, this power does not affect the sample. The representative Raman lines observed at 82, 117 and 139 cm-1 are well related to known spectrum of Sb2Te3. Thus, the PVT growth is applicable for the preparation of high-quality stoichiometric Sb2Te3 microcrystals. Acknowledgements: This study is supported by Ministry of Education and Science of the Russian Federation (Contracts 16.518.11.7091 and 2.8575.2013). |
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Presentation: Poster at 17th International Conference on Crystal Growth and Epitaxy - ICCGE-17, Topical Session 4, by Konstantin A. KokhSee On-line Journal of 17th International Conference on Crystal Growth and Epitaxy - ICCGE-17 Submitted: 2013-04-05 13:00 Revised: 2013-04-05 13:05 |