The effect of substrate and post-annealing temperature on the structural and optical properties of polycrystalline InSe thin films

X-ray diffraction, scanning electron microscopy, compositional analysis and transmission measurements are performed on InSe thin films grown by thermal evaporation at different substrate and annealing temperatures of 150-250 degrees C and 100-200 degrees C, respectively. An analysis of structural measurements indicates that there exist three phases of In-Se system like InSe, In2Se3 and In6Se7 in the same film at low-substrate temperature, but at high-substrate temperatures, In2Se3 phase was absent. The composition of InSe films changed significantly with substrate temperature and slightly with annealing temperature because of re-evaporation of selenium. The transmission measurements were carried out at room temperature over the spectral range 0.5 to 2.5 mu m. As a result of optical energy gap studies, the direct energy band gap was found to be in between 1.21 and 1.38 eV depending on substrate and annealing temperatures. (C) 1998 Elsevier Science S.A. All rights reserved.