Selenization of CO-sputtered Cu-In alloy films

Co-sputtering of Cu and In leads to rough Cu-In layers with a bi-layer structure of the surface in which island-type crystals were formed in a small-crystalline matrix layer. The elemental composition of the island- type crystals corresponds to the compound CuIn2 and the matrix area consists of the copper-rich Cu11In9 phase. The formation of α-CuInSe2 was initiated at 300°C and resulted in films with large and densely packed crystals with sizes of about 2 μm at temperatures higher than 420°C. The selenization leads to films with a coexistence of both a-CuInSe2 and Cu-Au polymorphic phases. The formation of CuIn3S5 was promoted by a lower temperature and a lower Se vapor pressure. The films selenized at temperatures higher than 420°C showed preferred orientation along the (112) plane, which was enhanced by higher temperature.