A comparative study of Cu-Se and In-Se bond length distributions in CuInSe2 with related In-rich compounds

The local atomic structure around the Cu and In atoms of CuInSe2 (CIS), Cu2In4Se7 and CuIn3Se5 was studied using Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy at the Cu and In K-edges. Room and low-temperature EXAFS measurements were performed at beamline BM29 at the European Synchrotron Radiation Facility (ESRF) and collected data were analysed using the freely available IFEFFIT package. The analysis assumed a chalcopyrite structure for the CuInSe2 samples while different structures (Cahleopyrite and P-chalcopyrite) were tried for Cu2In4Se7 and CuIn3Se5. The results show that the In-Se bond length remains constant in the CuInSe2 samples within the experimental uncertainty but slight differences are observed in the Cu-Se bond lengths. These decrease with the Cu content in accordance with previous X-ray diffraction (XRD) results on the same samples. The values obtained for the Debye-Waller factors in the CuInSe2 samples are lower for the In-Se bond compared to Cu-Se, which is consistent with a higher ionicity in the former bond. (c) 2004 Elsevier B.V. All rights reserved.