Crystallization phase transition in the precursors of CIGS films by Ar-ion plasma etching process

Mixed alloy Cu-In-Ga precursors were deposited from Cu-Ga alloy and Indium targets by the DC magnetron co-sputtering method. There were four crystallization phases, In, CuIn₂, Cu₁₁In₉ and Cu₃Ga, identified in the precursor after deposition. A large grain-size CIGS film was achieved by controlling the annealing period for selenization and utilizing a two-stage selenization process for secondary crystallization during rapid thermal annealing process. As the annealing temperature increased, the phase transitions moved toward the Cu-rich inter-metallic phases. In addition, the phase transition, stoichiometric ratio and surface-morphology were modified by Ar-ion plasma etching process of the precursors. The results show that after the ion etching process, the precursors can be transferred into a single Cu₁₁In₉ crystallization phase and the number of crevices increased due to the soft texture of indium on the surface of the precursors. Finally, CIGS films with good crystalline properties were achieved after a suitable selenization process of only 1-stage.