Structural properties of Zn2-2x(CuIn)(x)S-2 (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 d id not provide selective information about the geometric structure. Therefo re, EXAFS measurements were performed on thin films of Zn2-2x(CuIn)(x)S-2 a t the K shells of the metal ions In, Cu and Zn. Three bond lengths correspo nding to the nearest neighbour metal-sulfur distances were identified. Thes e bond lengths remain nearly constant over the whole composition range of t he solid solution system. This phenomenon, already known for binary compoun ds, is now observed for the first time a ternary system as well. The information gained by EXAFS was combined with electronic structure calc ulations 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 e qual to 0.25.