Optical band gap of Bi₂Te_2.8Se_0.2 thin films

Abstract

Bi₂Te_2.8Se_0.2thin films were grown using the thermal evaporation technique on a (001) face of NaCl crystal as a substrate at room temperature. The optical absorption was measured in the wave number range 500-4000 cm^-1. From the optical absorption data the band gap has been evaluated and studied as a function of the film thickness and deposition temperature. The data indicate absorption through direct interband transition with a band gap of around 0.24 eV.