Structural properties of Zn2-2x(CuIn)xS2 (x ≤ 1) solid solution thin film obtained by EXAFS

For the solid solution system Zn2-2x(CuIn)(x)S-2 XRD measurements revealed an increase of the cell volume as a function of alloying parameter x, but did not provide selective information about the geometric structure. Therefore, EXAFS measurements were performed on thin films of Zn2-2x(CuIn)(x)S-2 at the K shells of the metal ions In, Cu and Zn. Three bond lengths corresponding to the nearest neighbour metal-sulfur distances were identified. These bond lengths remain nearly constant over the whole composition range of the solid solution system. This phenomenon, already known for binary compounds, is now observed for the first time a ternary system as well. The information gained by EXAFS was combined with electronic structure calculations to understand the highly nonlinear dependence of the band gap on x observed in the composition range 0 less than or equal to x less than or equal to 0.25.