Preparation and Characterization of Electron-Beam Evaporated Cu-InSe Thin Films Using Two Stage Processes

CIS (Cu-InSe) thin films were prepared onto glass substrate by the two stage process—generally called bilayer process. At first, Cu layer was deposited onto glass substrate by electron beam evaporation technique and then InSe single layer was deposited on the resulting Cu layer to produce CIS thin film. XRD (X-ray diffraction) analysis revealed that deposited film has an amorphous nature. Electrical resistivity measurements were carried out as a function of temperature during heating and cooling cycles in air. The heating and cooling cycles of the sample are almost reversible after successive heat-treatment in air. In order to consider the influence of the InSe upper layer on the optical properties, the thickness of the InSe upper layer in the CIS films was varied from 50 to 150 nm. Analysis of the transmittance and reflectance spectra, recorded in the wavelength range of 400-1,100 nm, revealed that the CIS films have high absorption coefficient of ~10 cm. The direct band gap varies from 1.40 to 1.22 eV. The refractive index, the extinction coefficient and the dielectric constant of the CIS films depend on the film thickness.