Effect of gold doping via laser ablation on the structural, morphologic, and optical properties of CdS thin films for use in optoelectronic applications

This study reports the preparation of cadmium sulfide (CdS) sol–gel doped with Gold (Au) nanoparticles synthesized using a laser ablation method and the fabrication of thin films via spin-coating. Gold nanoparticles were produced by irradiating an Au target with a Q-switched Nd: YAG laser (1064 nm) at pulse numbers ranging from 500 to 2500. X-ray diffraction analysis confirmed a hexagonal nanostructure for CdS, with an average crystal size of 11.57 nm in pure films. In comparison, Au doping resulted in crystal sizes between 6.6 and 9.3 nm, depending on pulse number. Atomic force microscopy (AFM) revealed reduced grain sizes from 72.44 nm in pure films to 25.8 nm in Au-doped films at 2000 pulses. Optical absorption spectra (300–800 nm) indicated a decrease in the band gap from 2.39 (pure films) to 2.33 eV (doped films with the highest pulse number). Nonlinear optical properties, evaluated using the Z-scan technique, showed variations in thermal refractive index (\({n}_{2}\)) and optical limiting (OL) behavior with increasing pulse number. These results highlight the tunable optical and structural properties of Au-doped CdS films, making them promising candidates for optoelectronic applications.