Microstructural characterization and optical properties of ZnSe thin films

Abstract

Zinc Selenide (ZnSe) thin films (d = 0.09–1.25 μm) on glass substrates were prepared by physical vapour deposition under vacuum, using the quasi-closed volume technique. X-ray diffraction (XRD) analysis indicated that the samples are polycrystalline, have a cubic (zinc blende) structure and that the crystallites are preferentially oriented with the (1 1 1) planes parallel to the substrates. The microstructure of ZnSe films examined by transmission electron microscopy (TEM), including electron diffraction (ED) and high-resolution electron microscopy (HRTEM), confirms the preferential orientation of crystallites. The HRTEM micrographs show that preferred orientation of crystallites, along (1 1 1) planes, increases if, after deposition, the samples are subjected to a heat treatment. The spectral dependences of the transmission and absorption coefficients were studied in the range 300–1400 nm. The values of the bandgap energy, Eg, calculated from the absorption spectra, ranged between 2.50 eV and 2.80 eV.