A comprehensive study of opto-electrical and nonlinear properties of Cu@CdS thin films for optoelectronics

Abstract

Good quality cadmium sulfide (CdS) thin films were deposited on substrates of glass with different Cu concentrations using a sophisticated spray pyrolysis technique. Structural study confirms the formation of hexagonal phase CdS films with good crystallinity. The crystallite size was calculated to be in range from 19 to 21 nm and the texture coefficient was found to be higher along (110) plane for 1.0 wt.% CdS:Cu film. Further confirmation of hexagonal phase with improved crystallinity was approved by vibrational spectroscopy analysis. SEM mapping/EDX spectra shows the homogeneous presence of Cu in final film. SEM signify the nanostructured thin films fabrication with nanocrystallites formations. The optical transparency of fabricated films was noticed in range of 60 to 80%. The absorption and refractive indices values were estimated and found in range of 0.03 to 0.24, 1 to 3. The direct energy gap was noticed to reduce from 2.44 to 2. 31 eV by Cu doping. The PL spectra contains a single peak in range from 502 to 532 nm for pure and Cu doped CdS films, which is assigned to green emission and noted to be shifted towards lower wavelength. Dielectric constant, loss. loss tangent and conductivity were also determined and discussed. Moreover, the third order nonlinear susceptibility and nonlinear refractive index were calculated and found to be of high orders. The optical limiting study was also carried and shows noticeable effect of Cu doping. All results suggest that the CdS:Cu films are of good quality hence can be employed in opto-nonlinear devices.