Influence of Cd salt concentration on the photoconductivity of CdS thin films prepared by chemical bath technique

Abstract

Herein, a comparative study of the photodetection properties of CdS thin films deposited via the CBD method at different cadmium chloride concentrations of Cd (0.008) M, Cd (0.02) M, and Cd (0.08) M has been reported. The increase in cadmium salt concentration dominated the cluster deposition mechanism of the chemical bath deposition (CBD) method, leading to the cubic crystal phase and the thicker CdS thin films. Also, with the increase in cadmium salt concentration, the photosensivity decreased. After all investigations, it was concluded that the value of photosensivity strongly depends on the film thickness and the quantum confinement effect, as well as the amount of sulfur vacancy of samples grown by the CBD method. The quantum confinement effect of sample Cd (0.008 M) was proved by the blue shift of the optical band gap and the grain size of this sample shown by Transmission Electron Microscope (TEM). The structural properties, surface morphology, compositional properties, film thickness and optical properties of CdS thin films were studied by X-Ray Diffractometer (XRD), Field Emission-Scanning Electron Microscopy (FE-SEM), TEM, Energy Dispersive X-ray Spectroscopy (EDXS), Cross-Section Microscopy (CSM), UV–Vis Spectroscopy, and Photoluminescence Spectroscopy (PL), respectively. Besides, the optical sensor characteristics of these samples were analyzed by the I–V curves at a bias voltage of 5V. The results showed more than 200 times the photosensivity of sample Cd (0.008 M) compared to the sample Cd (0.08 M); 265 vs.1.3.