It was recalled that the performance of thin-film chalcopyrite solar cells, based upon a p-Cu(In,Ga)(S,Se)2/n-ZnO pn-junction, could be markedly improved by inserting a buffer at the interface. Such a layer was best grown by halogen-supported chemical vapour deposition at about 300C. When the buffers were grown at higher temperatures, the solar cells exhibited lower efficiencies which were blamed on thermally-activated atomic interdiffusion. Heavy-ion elastic recoil detection analysis was used to study depth-dependent atomic concentration profiles. These measurements revealed the diffusion of In from Cu(In,Ga)(S,Se)2 and into ZnSe. However, quantitative determination of the diffusion parameters was difficult because the surface and interface roughness of the polycrystalline material affected the measured energy spectra of the sample constituents. Therefore, the diffusion coefficient was deduced from separate measurements of evaporated In layers on ZnSe single crystals; annealed in an Ar atmosphere. Because the results were still largely affected by surface roughness, atomic force microscopic measurements were also performed in order to determine the surface morphology. With this additional information, it was possible to obtain the diffusion coefficient of In in

ZnSe. Thus, it was possible for the first time to analyze - qualitatively and quantitatively - atomic diffusion processes by elastic recoil detection analysis.

Investigations of Atomic Diffusion at CIGSSe/ZnSe Interfaces with Heavy Ion Elastic Recoil Detection Analysis (HI-ERDA). S.Lindner, W.Bohne, A.Jäger-Waldau, M.C.Lux-Steiner, J.Röhrich, G.Vogl: Thin Solid Films, 2002, 403-404, 432-7