OPTICAL-PROPERTIES OF TIN-SELENID FILMS

SnSe thin films of different thicknesses were prepared by the thermal evaporation technique in vacuum of 10(-4) Pa. The structure analysis o f the films as determined from the electron diffraction pattern and X- ray diffraction indicate that the films were polycrystalline of orthor hombic structure. The transmittance and reflectance of SnSe films were measured at normal incidence in the wavelength range of 760-2200 nm. It was found that the refractive index n and the absorption index k ar e independent of the film thickness. Graphical representation of log(a lpha) as a function of (1/lambda) shows two distinct linear parts indi cating the existence of two optical transitions. The analysis of the s pectral behavior of the absorption coefficient in the intrinsic absorp tion region revealed an indirect and direct allowed transition E(g)(in d) = 0.895 eV and E(g)(d) = 1.27, respectively.