Effect of Cu metallic impurities on structural, optical and electrical properties of cadmium sulfide thin films

Thin films of Cadmium Sulfide have been deposited on glass substrates by thermal evaporation technique under the pressure of p= 3 × 10-6 Torr. The rate of deposition and thickness of the films were taken fixed at 3.5nm/s and 550 nm respectively. Some of the CdS specimens were selected for indirect implantation of Copper with different densities.The crystalline structure of the samples was investigated by X- ray diffractometry (XRD). It was revealed that hexagonal structure with [002] plane of reflection at 165 C° is remained the same in CdS films before and after Cu implantation. In other word, doping of Cu atoms do not change the crystal phase, but only enhance the peak intensity at [002] plane. In this paper variation of refractive index and band gap of composites (i.e CdS and CdS:Cu) with substrate temperature and copper densities were studied. It was found that, band gap of samples varies between 2.43 ev to 2.48 ev. Also, that of refractive index variation was between 1.75 to 2.51 ev. The electrical properties of CdS planes un doped and doped with Cu, examined by four point probe in which, the resistivety of CdS from 5.2 × 103 WCm was reduced to 9 × 10-3 WCm by Cu implantation.