EXAFS STUDIES ON (CU,IN)SE2

The local structure of chalcopyrite (Cu, In)Se2 has been investigated by ''tended X-ray absorption fine structure (EXAFS) measurements on the Cu K- and the Se K-edges. The values of the Cu-Se and the In-Se bond lengths were determined for various values of the Cu/In ratio, and the Se position parameter u was estimated from the obtained bond lengths and the lattice parameters. For the sample with Cu / In = 0.96, the u-values obtained from the Cu-Se and the In-Se bond lengths are consistent with each other, and it was determined as 0.223. On the other hand, the relation of these structural parameters show a deviation from the values expected for the chalcopyrite structure as the Cu / In ratio deviates from 0.96. These results indicate that the chalcopyrite single phase is obtained within a narrow range of the Cu / In ratio around 0.96 while a structural disorder due to either the compositional fluctuation or the multiphase occurs as the Cu/In ratio deviates from 0.96.