In-situ Observation of Selenization of Cu-Ga-In Metallic Precursors

The reaction pathway of Cu(In_1-x,Ga_x)Se₂ formation by the selenization of Cu-Ga-In/Mo/glass precursors was investigated using in-situ high-temperature X-ray diffraction (HT-XRD). The room-temperature XRD pattern shows that Cu₁₁In₉, CuIn, and pure In formed during MBE-deposition of the precursor. Selenium powder was placed in wells on the HT-XRD sample holder to provide a Se ambient during selenization. The in-situ HT-XRD observation of selenization of precursors showed that the selenization process of Cu-Ga-In/Mo/glass produces an intermediate CuSe phase in the temperature range of 260 to 370degC. The formation of CIGS is initiated at approximately 260degC, which is close to the initial appearance of CuSe. MoSe₂ formation was detected at temperature above approximately 400degC. The Ga composition (x= 0.35~0.39) of the resulting CIGS as estimated by the cell refinement method of XRD data suggests partial evaporation of indium during the temperature ramp annealing