Polycrystalline CuInS 2 (CIS) films are prepared by sulfurization of CuIn metallic precursors with Cu/In=1.2 on Mo substrates. Variation of the rapid thermal processing (RTP) parameters adjusted to the low Cu surplus yielded near stoichiometric CIS films with considerably less CuS x precipitation at the surface. A start temperature and low temperature slopes were introduced to guarantee crystal quality and large grain size. XPS/UPS, XRD and SEM data show the distinct properties of the chalcopyrite phase and its morphological structure in comparison to the standard sulfurization process. A considerable improvement has been achieved by variation of the temperature profiles. The proposed process modules obtain near stoichiometric CIS films for industrial solar cell production.

We report on epitaxial growth of ZnO on polycrystalline and (112) orientated CuInS 2 and CuInSe 2 thin films.Step-by-step growth and investigation by photoelectron spectroscopy (PES) and low energy electron diffraction (LEED) provided information on the growth mode and the electronic structure of the ZnO-CuInS 2 -interface. During the initial growth no ZnO is deposited.Instead a monolayer of ZnS is formed by depletion the CuInS 2 surface of excess sulfur.Thereafter, the ZnO growth starts on the ZnS buffer layer. The band alignment derived from PES shows that the ZnS buffer layer is thin enough to provide a beneficial band alignment for photovoltaic applications. CuInSe 2 (112) samples showed a similar behaviour, but at the chosen deposition temperature of 450°C only ZnSe growth is detected. At lower temperatures ZnO growth on top of ZnSe is observed. XPEEM experiments show an inhomogeneous interface.