Morphology of CIGS thin films deposited by single-stage process and three-stage process at low temperature

Cu(In,Ga)Se₂ (CIGS) thin films are prepared by a single-stage process and a three-stage process at low temperature in the co-evaporation equipment. The quite different morphologies of CIGS thin films deposited by two methods are characterized by scanning electron microscopy (SEM). The orientation of CIGS thin films is identified by X-ray diffraction (XRD) and Raman spectrum, respectively. Through analyzing the film-forming mechanisms of two preparation processes, we consider the cause of such differences is that the films deposited by three-stage process at low temperature evolve from Cu-poor to Cu-rich ones and then back to Cu-poor ones. The three-stage process at low temperature results in the CIGS thin films with the (220)/(204) preferred orientation, and the ordered vacancy compound (OVC) layer is formed on the surface of the film. This study has great significance to large-scale industrial production.