EXAFS study on MBE grown CuInSe₂ thin film

The structures of CuInSe₂(CIS) grown on GaAs(001) by molecular beam epitaxy (MBE) were characterized by extended X-ray adsorption fine structure (EXAFS) for the local structure, changing the Cu/In ratio systematically. Radial distributions around Cu and Se atoms change drastically as a function of the Cu/In ratio. The results show that the ordered chalcopyrite phase is grown within a narrow composition range near the ideal stoichiometry. It is found that deviations from the stoichiometry in either direction cause a significant change in the local structure which results from the structural disorder and/or the phase separation. The temperature dependence of mean square relative displacement indicates the Cu-Se bond in Cu-rich region is stronger than that in In-rich region. We also compare the MBE grown CIS epitaxial layer, coevaporation thin layer and bulk sample.