Local structure of CuInSe2 thin film studied by extended X-ray absorption fine structure

The local structure of CuInSe2 thin films has been studied by extended X-ray absorption fine structure 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 α(0.29<α<1.13). The results show that the local structure of the thin film CuInSe2 is quite similar to that of the bulk crystal over a wide range of α. However, it is found that with decreasing α, the Cu-Se and In-Se bond lengths deviate systematically from those of the stoichiometric bulk CuInSe2 crystal, which is attributed to the chemical disorder of the cation sites and the formation of anion vacancies in the chalcopyrite lattice. The temperature dependences of mean square relative displacements indicate that the In-Se bond is stronger than the Cu-Se bond. (author)