Substrate temperature dependent physical properties of In2S3 films

Indium sulfide (In(2)S(3)) layers were deposited on glass substrates by close-spaced evaporation of In(2)S(3) powder at various deposition temperatures in the range 200-350 degrees C. The chemical composition, structure, surface morphology, optical and electrical studies were carried out using appropriate techniques. The chemical composition of the layers analysed using x-ray photoelectron spectroscopy studies revealed that the layers prepared at a substrate temperature of 300 degrees C were sulfur deficient. These layers exhibited a broad (1 0 3) orientation, corresponding to the tetragonal structure of In(2)S(3) with an average grain size of 32 nm and an average surface roughness of 1.4 nm. The layers showed a combination of tetragonal and cubic structures at lower substrate temperatures (<= 300 degrees C) without the presence of other phases of In2S3. The layers had a high optical transmittance of 78% and the energy band gap of the films increased from 2.09 to 2.52 eV with the increase in substrate temperature. The films grown at 300 degrees C showed a conductivity of 7.81 x 10(-4) (Omega cm)(-1). The Arrhenius plots indicated two regions where the carrier transport was mainly due to thermionic emission in the temperature region 290-450 K while Mott's hopping was predominant below 290 K.