Influence of thermal annealing on CdTe thin film deposited by thermal evaporation technique

Effects of thermal annealing on the structural and optical properties of thermally evaporated CdTe thin films are presented here. Thin films of CdTe were deposited on soda lime glass substrates at room temperature by varying the deposition current ranging from 25 Amperes to 30 Amperes by thermal evaporation. The grown samples were annealed at the annealing temperature of 400°C for 15 minutes in a vacuum furnace of nitrogen ambient with pressure of 250–300 mTorr. The structural, optical and electrical properties of the grown samples were investigated by XRD, AFM and UV-VIS spectrometry. The as-deposited films prepared at deposition current 25A shows polycrystalline nature whereas the films prepared at 28A and 30A exhibit cubic crystallinity with (111) preferential orientation around 2θ=23.8°. The surface roughness of the films is also highly affected by the thermal annealing as observed from the AFM images. The band gap has been found around 1.5 eV for the as-deposited film whereas the band gap decreased approximately to 1.4 eV after thermal annealing treatment.