Electrical and optical properties of (Sb2Se3)2 (Sb2Te3)1 thin films

Abstract

A study of the synthesized (Sb2Se3)2 (Sb2Te3)1 glassy system has been carried out, X-ray diffraction (XRD) patterns and differential thermal analysis (DTA) of the system studied were used to obtain an insight into the structural information. An investigation of the electrical and optical properties of (Sb2Se3)2 (Sb2Te3)1 thin films prepared by thermal evaporation having different thicknesses (89.2, 214, 223 nm) and annealing temperatures ranging from 300 to 473 K has been carried out. The effect of the thickness and heat treatment on the activation energy ΔE for d.c. conductivity and the density of localized states at the Fermi level N(EF) were carried out. The electrical conductivity measurements depend on the thickness and annealing temperature, and exhibit two types of conduction mechanisms. Optical absorption measurements have been made on as-deposited and annealed films for the investigated system. The optical transition was found to be indirect. The optical energy gap (Eopt) decreases with increasing thickness and annealing temperatures (below Tg). The corresponding band is approximately twice the conduction activation energy. This effect is interpreted in terms of the density of states model proposed by Mott and Davis.