STRUCTURAL AND OPTICAL PROPERTIES OF NANOCRYSTALLINE Se0.8Te0.2

Nanocrystalline Se0.8Te0.2 films were grown on quartz substrates by using thermal evaporation technique. Structural and optical properties of as-grown and annealed samples were investigated with XRD, SEM and UV-visible spectroscopy. The x-ray diffraction pattern at room temperature shows that the sample are formed in single phase with monoclinic crystal symmetry having space group Cm. Surface morphology of the glass asgrown film was investigated via scanning electron microscopy (SEM). The typical diameter of as-grown nanocrystalline sample is found to be 50 nm, which is consistent with crystallite size calculated by XRD data using Scherrer equation. The UV-visible absorption spectra of the nanocrystals show that the optical band gap of as-grown and annealed samples are situated systematically in the range of 2.10 1.95 eV, which is quite larger than the bulk phase of the materials. The results have been explained on the basis of the close interplay between the structural and optical properties.