STRUCTURAL AND OPTICAL-PROPERTIES OF AMORPHOUS AND CRYSTALLINE INSE THIN-FILMS

Structural and optical properties of amorphous and crystalline InSe thin films of different thicknesses and the effect of annealing temperature on these properties were investigated. X-ray diffraction and electron microscopic techniques were used to get an insight into the structural information of the samples. It was found that for InSe films, a transition from the amorphous to the crystalline state takes place at 393 K and the degree of crystallinity increases with temperature and film thickness. The lattice constants for InSe in powder form were found to be a = 4 angstrom and c = 16.641 angstrom. The optical constants (refractive index n, absorption constant k and absorption coefficient-alpha) and the valence band density of states g1 were determined. The calculated values of the optical energy gap E(g)opt, n, k and g1 were found to be independent of film thickness, but depend markedly on annealing temperature. These results are interpreted in terms of the density of state model of Mott and Davis.