Impact of the thickness on the optical, electronic, and structural properties of sputtered Cu2S thin films

A successful hexagonal Cu 2 S p-type semiconductor thin film using DC magnetron sputtering is reported. Films with thickness gradients were deposited by taking advantage of deposition geometry and target dimensions. X-ray diffraction (XRD) analysis confirmed the exclusive formation of the hexagonal Cu 2 S phase. Elemental composition and thickness dependence with the sample position were determined using energy-dispersive x-ray spectroscopy. Optical properties, including the optical bandgap, refractive index, and extinction coefficient, were assessed by modeling transmittance spectra. The Tauc-Lorentz oscillator and Drude models were employed for this purpose. XRD data analysis successfully determined the film thickness ( t X R D ) as a function of the sample position, aligning well with thickness values ( t T ) derived from transmittance spectra analyses. These results were further supported by film thickness values ( t S E M ) obtained from cross-sectional SEM images. Charge carrier density and mobility, extracted from the optical models, were found to be consistent with DC electrical measurements. AC impedance curves were effectively modeled with RL-RC parallel circuits. The results indicate that the inductance (L) and capacitance (C) components of the films increase with decreasing film thickness.