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

Abstract

A successful hexagonal Cu2S 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 Cu2S 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 (tXRD) as a function of the sample position, aligning well with thickness values (tT) derived from transmittance spectra analyses. These results were further supported by film thickness values (tSEM) 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.