Electronic and Optical Properties of Bi2Te3 Thin Film: A First Principles Calculations within Cooper’s Exchange Potentials

Abstract

Bismuth telluride (Bi2Te3) thin film has received great interests for laser photonic, optical communication, biomedical imaging, gas sensing and motion detection applications. Therefore, to expose its hidden potentials, detailed knowledge of its optoelectronic properties at the level of reliable and more efficient techniques is very essential. In this study, theoretical calculations of electronic and optical properties of Bi2Te3 thin films are presented using first principles approach based on recent developed Cooper’s exchange potentials (vdW-DFC09x) within Density Functional Theory (DFT) framework. The simulated film is in the [001] direction using supercell method with a large vacuum along z-direction so that slab and periodic images can be treated independently. The calculated values of direct energy gap at Γ point confirmed the robust surface states from 3 quintuple layer (QL). The 1 QL, 2 QL, 3 QL and 4QL films show an energy gap of 0.421, 0.122, 0.023 and 0.006 eV respectively and these values are in good agreement with experimental results. Optical properties comprising of imaginary and real parts of dielectric function, electron loses function and absorption coefficient were also investigated to understand the optical behaviour of Bi2Te3 thin films. The results of optical absorption show that Bi2Te3 thin film has strong absorption in the near infrared to ultraviolet wavelenghts, therefore, it is anticipated that these films can be used as an absorbing layer for broadband photodetector and solar cell.