Comparative study of the structural and optical properties of CIS films prepared by RF-magnetron sputtering and selenization of elemental layers

摘要

We report on a study where the properties of films obtained by RF-magnetron sputtering and by Selenization of elemental precursor layers are analysed by Raman scattering, x-ray diffraction and optical measurements. Three routes were followed to prepare CIS films on glass. CIS type-I was prepared by selenization at various temperatures, CIS type-II was prepared by RF-magnetron sputtering on room temperature substrate followed by annealing at 450°C in air for 10 mm and CIS type-III was prepared by RF-magnetron sputtering on a substrate at a temperature ranging from 200°C up to 500°C with a post-deposition annealing in the same conditions as for CIS type-II. Correlating the results from x-ray diffraction with the Raman scattering and optical measurements it was possible to establish unequivocally the formation of CIS with the chalcopyrite structure for CIS type-I at 400°C. Through the same procedure it was possible to establish a way to produce CIS type-II with the chalcopyrite structure. A high density of defects was inferred from the transmission results. Finally the growth dynamics of CIS type-III was studied. It was observed a structural/compositional transition around substrate temperature of 300°C. It was observed that all the films had a sphalerite structure even for the highest substrate temperatures. It was establish the need far a post-deposition annealing to obtain CIS type-III with the chalcopyrite structure. The Raman scattering was found to be a very sensitive technique that allowed us to uncover a difference in the CIS type-I and II with the chalcopyrite structure.