Structural Properties of Cu-Se-CuSe2 Thin Films

Abstract

This paper describes the structural and optical properties of Cu-Se-CuSe2 thin films. The surface morphology of thin films was investigated by atomic force microscopy (AFM) and scanning electron microscopy (SEM). Formation of thin films is concluded to proceed unevenly, in the form of islands which later grew into agglomerates. The structural characterization of Cu-Se-CuSe2 thin film was investigated using X-ray diffraction pattern (XRD). The presence of two-phase system is observed. One is the solid solution of Cu in Se and the other is low-pressure modification of CuSe2. The Raman spectroscopy was used to identify and quantify the individual phases present in the films. Red shift and asymmetry of Raman mode characteristic for CuSe2 enable us to estimate nanocrystal dimension. In the analysis of the far-infrared reflection spectra, numerical model for calculating the reflectivity coefficient of layered system, which includes film with nanocrystallite inclusions (modeled by Maxwell–Garnet approximation) and substrate, has been applied. UV–VIS spectroscopy and photoluminescence spectroscopy are employed to estimate direct and indirect band gap of CuSe2.