FABRICATION AND CHARACTERIZATION OF BISMUTH TELLURIDE THIN FILMS BY THERMAL EVAPORATION TECHNIQUE

An interest in the study of the structural and optical properties of topological insulators, led to the selection of Bismuth telluride thin films. Among the topological insulators, Bismuth telluride is one of the promising materials that exhibit applications in the field of thermoelectric power generation. The films were prepared using the thermal evaporation method under vacuum conditions of [Formula: see text] mbar on glass substrates maintained at a temperature of 120 ∘ C. The thickness of the film samples ranges from 400 Å to 1400 Å. Pure phases of Bi 2 Te 3 with a rhombohedral structure are confirmed using X-ray Diffraction. The crystallite size was calculated using Debye–Scherrer’s formula. Structural morphology and compositions are examined using SEM and EDAX. The UV–Vis study reflects the optical behavior of the thin film samples. The absorption spectra gives the direct and allowed transition band gap of the Bi 2 Te 3 thin film samples for various thicknesses. The band gap decreases with the increase in the thickness of the Bi 2 Te 3 thin films, suggesting that the material has significant absorption towards the visible spectrum. The Photoluminescence (PL) emissions for Bi 2 Te 3 thin film samples of various thicknesses are examined and analysed. Raman study reveals the presence of two active modes.