LOCAL-STRUCTURE OF CUINSE2 THIN-FILM STUDIED BY EXAFS

We have investigated the local structure of CuInSe2 (CIS) thin films by surface-sensitive EXAFS on the Cu K- and Se K-edges using synchrotron radiation. We estimated the Cu-Se and In-Se bond lengths as a function of In/Cu ratio. The local structure of the thin film CIS is quite similar to that of the bulk chalcopyrite over a wide range of the In/Cu ratio. It is found that with decreasing the In / Cu ratio from the stoichiometric composition, the Cu-Se and In-Se bond lengths systematically deviate from those of stoichiometric bulk CuInSe2, which is attributed to the chemical disorder of the cation site in the chalcopyrite structure.