Optical and electrical characterizations of nanoparticle Cu sub(2)S thin films

Copper sulfide thin films are deposited onto different substrates at room temperature using the thermal evaporation technique. X-ray diffraction spectra show that the film has an orthorhombicchalcocite ( gamma -Cu sub(2)S) phase. The atomic force microscopy images indicate that the film exhibits nanoparticles with an average size of nearly 44 nm. Specrtophotometric measurements for the transmittance and reflectance are carried out at normal incidence in a spectral wavelength range of 450 nm-2500 nm. The refractive index, n, as well as the absorption index, k is calculated. Some dispersion parameters are determined. The analyses of epsilon sub(1) and epsilon sub(2) reveal several absorption peaks. The analysis of the spectral behavior of the absorption coefficient, alpha , in the absorption region reveals direct and indirect allowed transitions. The dark electrical resistivity is studied as a function of film thickness and temperature. Tellier's model is adopted for determining the mean free path and bulk resistance.