Cu-doped CdS thin films by chemical bath deposition and ion exchange

This work presents the synthesis and characterization of nanostructured cadmium sulfide thin films obtained by an ammonia-free chemical bath deposition process. Different levels of Cu ion doping were achieved by the ion exchange method of CdS at room temperature. The main objective was to control the energy band gap adjusting the copper concentration and to gather information about Cu-doped CdS thin films. Optical absorbance measurements were performed to obtain the band gap value through Tauc’s plot method. XPS measurements were used to obtain the copper and cadmium concentration. In addition, SEM micrographs were collected to obtain information about surface and structural arrangement on Cu-doped CdS thin films. It was also found that the exchange of cadmium by Cu-ions promoted the formation of a hexagonal crystalline structure, which was different than the initial pure cubic structure. Through optical characterization, it is possible to evaluate the impact of the metallic dopant on the band gap value, finding that it can be controlled by the percentage of added copper, which opens the possibility of applying this material to the development of electronic devices such as field effect transistors. In addition, a prototype of a MOS structure was fabricated employing both the undoped and the Cu-doped CdS thin film to corroborate its possible application as a field effect transistor.