Real-time studies of phase transformations in Cu–In–Se–S thin films: 1. Intermetallic phase transformations

Abstract

Phase transformations of Cu x In thin films were investigated in annealing experiments using real-time in situ energy dispersive X-ray diffraction (EDXRD). Cu x In films of micrometer thickness with x = 0.7 , 1.0, and 1.8 were annealed up to 500 °C. The experiments were designed in order to form a basis for the understanding of the phase transformations relevant for chalcogenization of Cu x In films. The starting layers for the in situ study consist of CuIn 2 and Cu, i.e. all In are accumulated in an intermetallic phase. Depending on the In content in a film, the volume fraction of the CuIn 2 phase varies. The main phase transformations in the annealing cycle can be described by the following reaction schemes: (1) 11CuIn 2→Cu 11In 9+13In solid, (2) 16Cu solid+9In liq→η-Cu 16In 9 (or (2′) 7Cu solid+9In liq→Cu 7In 3), and (3) 16Cu 11In 9→11η−Cu 16In 9+45In liq. At top temperature, rapidly changing diffraction patterns point out rapid transitions between different metastable polytypes of Cu 16In 9. Metallic phases observed at room temperature after quenching are η-Cu 16In 9, Cu 11In 9, and In solid where the respective volume fractions depend on the starting film composition.