Variation of optical, structural, electrical and compositional properties of thermally evaporated CdTe thin films due to substrate temperature

Abstract

Alteration of substrate temperature of thermally evaporated CdTe thin films can cause changes to the film structure and composition, affecting its optical, electrical as well as morphological properties. In this respect, polycrystalline CdTe thin films were deposited using thermal evaporation technique under different substrate temperatures from 125 to 300 °C. The optical, structural, compositional, morphological and electrical properties were studied using UV–visible spectroscopy, GIXRD, EDX, SEM and van der Pauw method, respectively. Optical measurements revealed that the band gap of the films slightly increase with increasing substrate temperature. Structurally, the lattice parameter and the crystallite size of the CdTe films deposited under a substrate temperature of 200 °C was found to be considerably higher than the rest of the substrate temperatures investigated. Texture coefficient indicate that the (111) plane becomes preferable as the substrate temperature is elevated to 300 °C. The lowest electrical resistivity was also found for samples deposited under a substrate temperature of 200 °C. Furthermore, EDX results reveals the composition of CdTe film considerably vary with respect to the substrate temperature at which the film was fabricated.