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537.311.322+538.9+539.2 (2) |
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SM ISO690:2012 UNTILA, Dumitru, CARAMAN, Iulia, EVTODIEV, Igor, SPALATU, Nicolae, DMITROGLO, Liliana, EVTODIEV, Silvia, SPOIALĂ, Dorin, VOLOBUJEVA, O., CARAMAN, Mihail. Structure and photoluminescence of the ZnTe-GaTe nanostructures obtained by thermal annealing of GaTe plates in Zn vapours. In: Materials Science and Condensed Matter Physics, Ed. 9, 25-28 septembrie 2018, Chișinău. Chișinău, Republica Moldova: Institutul de Fizică Aplicată, 2018, Ediția 9, p. 205. |
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Materials Science and Condensed Matter Physics Ediția 9, 2018 |
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Conferința "International Conference on Materials Science and Condensed Matter Physics" 9, Chișinău, Moldova, 25-28 septembrie 2018 | |||||
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CZU: 537.311.322+538.9+539.2 | |||||
Pag. 205-205 | |||||
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GaTe is a layered semiconductor with anisotropic physical properties that are determined by the nature of the chemical bonds between Ga and Te atoms. The GaTe single crystals consist of elementary packings of Te-Ga-Ga-Te type with strong ionic-covalent chemical bonds within elementary packings and weak polarization forces between elementary packings [1]. These structural particularities determine the anisotropy of the mechanical, electric and optical properties of the GaTe semiconductor. The weak forces between elementary packings allow the obtaining of GaTe plates with smooth parallel surfaces and thicknesses less than tens of nanometres by cleavage or exfoliation in atmosphere or in liquids [2]. The specific properties for 2D materials are well defined in these plates. They can be used for fabrication of flexible luminescent diodes and high sensitivity photodetectors for visible spectral range [3, 4]. GaTe being a direct semiconductor with band gap of 1.790 eV (at 300K) and having an absorption coefficient of 10-4 cm-1 magnitude, represents a perspective material for applications in optoelectronic devices, detectors of ionizing radiations and solar cells [5, 6]. Both GaTe bulk and thin layers of nanometric thickness are luminescent materials with narrow emission band localized at the border between the red and NIR spectral range [7]. The Ga-Te bonds, being weaker than Ga-Ga bonds, allow the obtaining of ZnTe-GaTe layered structures by thermal annealing of the GaTe plates in Zn vapours. Also, ZnTe is a material with advanced optical and luminescent properties in the yellow-red spectral range and has wide applications in optoelectronic devices [8]. The analyses provided using XRD, SEM-EDS, Raman and PL methods of the outer and inner surfaces of GaTe plates thermally annealed in Zn vapours at 1073K for 1-24 hours shows that a compound consisting of ZnTe and GaTe crystallites is formed. It was observed that GaTe plates are very active in air and oxidize very quickly. For this reason for thermal annealing have been used GaTe plates that were freshly cleaved from bulk single crystals. As a result, the pristine GaTe plates contain low quantities of tellurite (TeO2). The GaTe plates are covered with a microcrystalline ZnTe layer and, moreover, the oxygen concentration in samples decreases after thermal annealing in Zn vapours at 1073K. The structure of the ZnTe layer depends on the treatment duration. Thus ZnTe islands are present onto surface after treatment shorter than 6 hours, while after the treatment longer than 6 hours the surface of the GaTe plates is covered by a homogenous ZnTe layer. The photoluminescence spectra of ZnTe-GaTe structures at 80K cover the green-red spectral range and contain emission bands characteristic for GaTe crystals as well as ones characteristic for ZnTe compound. |
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