Optical band gap of In0.1Bi1.9Te3 thin films

Thin films (In0.1Bi1.9Te3) 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 band gap increases with decreasing thickness, a result normally associated with quantum size effect. The deposition temperature does not seem to affect the band gap as indicated by the results. The data indicate absorption through direct interband transition with a band gap around 0.14 eV.