Structural characterization and optical properties of ZnSe thin films

Abstract

Zinc selenide (ZnSe) thin films ( d = 0.11–0.93 μm) were deposited onto glass substrates by the quasi-closed volume technique under vacuum. Their structural characteristics were studied by X-ray diffraction (XRD) and atomic force microscopy (AFM). The experiments showed that the films are polycrystalline and have a zinc blende (cubic) structure. The film crystallites are preferentially oriented with the (1 1 1) planes parallel to the substrate surface. AFM images showed that the films have a grain like surface morphology. The average roughness, R a = 3.3–6.4 nm, and the root mean square roughness, R rms = 5.4–11.9 nm, were calculated and found to depend on the film thickness and post-deposition heat treatment. The spectral dependence of the absorption coefficient was determined from transmission spectra, in the range 300–1400 nm. The values of optical bandgap were calculated from the absorption spectra, E g = 2.6–2.7 eV. The effect of the deposition conditions and post-deposition heat treatment on the structural and optical characteristics was investigated.