Preparation and Characterization of The Nanostructured Bismuth Telluride Thin Films Deposited by Thermal Evaporation Technique

Bismuth telluride-based heavily doped semiconductors are known to be one of the best thermoelectric materials, which have been applied in cooling and power generation. In this paper, we combined both zone melting and thermal evaporation techniques to prepare Bi2Te3 thin films and annealing under vacuum and N-2 atmospheres at 250 degrees C. For the bulk Bi2Te3 material, the measured atomic Bi percentage incorporated was smaller than the corresponding percentage of evaporated Bi. So, the used material was adjusted to get the stoichiometric ratio. Structural, morphological characterizations and thermoelectric investigations were carried out for the thermoelectric material as-deposited and after annealing. The X-ray diffraction patterns confirmed the formation of the nano-particles Bi2Te3 structure and showed that the prepared thin films are polycrystalline in nature. Field Emission Scanning Electron Microscopy showed its granular growth. The grains were homogenous and compact. As the samples annealed, the crystallinity and the grain size were increased. Energy-dispersive X-ray spectroscopy confirmed that the samples are stoichiometric. The power factor, Seebeck coefficient, electrical resistivity, carrier concentration and Hall mobility were measured and evaluated at room temperature with the best power factor of 25.7 mu WK(-2)cm(-1). (C) 2019 Elsevier Ltd. All rights reserved.