Selenization of (Cu, In, Ga)/Se/Mo/Glass Thin Films: A Real-Time Synchrotron X-ray Scattering Study

The precursor selenization of (Cu, In, Ga)/Se/Mo/glass thin films during annealing without additional supply of Se was studied through a real-time synchrotron X-ray scattering experiment. At a lower temperature, the crystalline CIS, Cu₂In, In₂Se₃, and Ga₂Se₃ phases were formed. By increasing the temperature, some parts of the crystalline CIS phase decomposed into Cu₂In and In₂Se₃ phases. At a higher temperature, the crystalline CIGS phase was synthesized gradually by the reaction of the crystalline Cu₂In, In₂Se₃, and Ga₂Se₃ phases, and not by direct crystallization of the amorphous precursor. The behavior of the integrated intensities and the crystal domain sizes were consistent with the changes in X-ray powder diffraction profiles. The high synthesis temperature in the CIGS phase was attributed to the high activation energy barrier for diffusion of Ga ions in the crystalline Ga₂Se₃ phase.