Optical Properties of Copper and Silver Ion-Activated Films of a Cds–ZnS System, Deposited at Different Temperatures

Abstract

Purpose. In this study, the infl uence of the deposition temperature and of the impurities of copper and silver ions (10–7–10–3 at. %) on the optical properties of fi lms of a CdS–ZnS system was investigated. Methods. The fi lms of a CdS–ZnS system were synthesized using the method of pyrolysis of the aerosols of thiourea solutions of [М(N2H4CS)2Br2] (М = Cd, Zn) coordination compounds within the temperature range of 350–500 °С. The absorption and refl ection spectra were obtained in the area of the fundamental absorption edge as the result of the study of fi lms of CdS–ZnS system the optical properties. The phase composition and crystal structure of the fi lms were examined using Х-ray diffraction analysis. The elemental composition of the samples was defi ned by the method of local X-ray spectral microanalysis using a scanning electron microscope. Results. The absorption and refl ection spectra of the CdS–ZnS fi lms doped with copper and silver ions were studied and their optical band gap Eg was measured. It was found that an increase in the amount of zinc sulphide in the samples results in progressive increase in the value of the optical band gap, regardless of the type and concentration of the doping impurity. Also, the infl uence of the deposition temperature and the activating impurity on the optical band gap of synthesized sulphides has been studied. It was established that the fi lms of the CdS–ZnS system are polycrystalline and they crystallize in the wurtzite structure. Conclusion. It was found that the absorption edge of all the studied CdS–ZnS fi lms shifted to the short-wave area with an increase of zinc sulphide content in them and the optical band gap expands, respectively. Increase in the impurity concentration up to 10–3 at % and temperature increase up to 500 °C led to the reduction of the optical band gap of the synthesized samples due to the changes in their defect and band structure

Keywords

• cadmium sulfi de
• zinc sulfi de
• optical band gap
• thiourea coordination compounds
• aerosol pyrolysis.