Stacked layers of CuGaSe2 and CuInSe2, grown under slightly Cu-rich conditions, were compared with the corresponding CuGaSe2 and CuInSe2 single layers by using cross-sectional scanning electron microscopy and transmission electron microscopic; as well as X-ray diffraction. All of the samples were grown onto both Mo-coated soda-lime glass substrates and onto Mo-coated glass substrates with an Al2O3 barrier to block Na out-diffusion. Differences were found in both the grain structure and the Ga–In interdiffusion behavior; depending upon whether Na was present during growth. In the Na-free case, evidence was found for recrystallization of the underlying CuGaSe2 layer during subsequent CuInSe2 growth. In this case, the interdiffusion of In and Ga was also enhanced as compared with samples grown in the presence of Na.

Re-Crystallization and Interdiffusion in CGS/CIS Bilayers. M.Bodegård, O.Lundberg, J.Lu, L.Stolt: Thin Solid Films, 2003, 431-432, 46-52