Abstract

The CdS thin film is a critical narrow bandgap n-type material for efficient optoelectronic applications. In this study, CdS thin films were deposited on silicon and glass substrates using the RF-magnetron sputtering technique. The effect of sputtering power (60 W, 80 W, and 100 W) on the thin film surface scaling, fractal dimension, and optical properties are extensively investigated. Autocorrelation and height–height correlation functions were applied to AFM images to extract deep insights about the thin films’ surfaces. Fractal dimension (Df) was extracted through the power spectral density function. FESEM images revealed uniform, homogeneous, and crack-free grains, while AFM topography showed an increase in surface roughness with higher sputtering power. Energy dispersive X-ray spectroscopy confirmed the elemental composition of cadmium and sulfur in the CdS thin films. Fractal dimension were extracted through power spectral density and values were in the range of 1.83 to 1.89 for all the samples. Optical analysis indicated a slight reduction in the energy bandgap from ~ 2.34 eV to ~ 2.26 eV with increasing sputtering power and the Urbach tail parameter increased. Additionally, the complex refractive index, dielectric constant, tangent loss, and both volume and surface energy loss were notably affected by the sputtering power conditions. The performance of Ag/CdS/Si/Al photodetectors was also evaluated using I-V measurements at room temperature. The significant parameters such as responsivity (R) and detectivity (D) were determined. It was observed that while responsivity increases with increasing puttering power. The R and D of the CdS films were found to be ranges from ~ 0.037 to 0.099 mAW−1 and 1.56 × 109- 4.2 × 109 Jones, respectively. Overall, sputtering power significantly influenced the optoelectrical performance of the CdS-based photodetector device.