EXAFS in mixed defect chalcopyrite ZnGa2(SxSe1-x)4

Defect chalcopyrites of the AIIBIII2×VI4 family (tetragonal 14 space group) have a structure derived from that of chalcopyrite by the inclusion of an ordered array of vacancies. Each cation is surrounded by four anions at the corners of a regular tetrahedron whereas each anion has one A atom, two B atoms and a vacancy as first neighbours [1]. The position of the anion in the unit cell is close to the zincblende ideal site, but the anisotropic local structure displaces it by an amount described by three “free” parameters δ1, δ2, δ3, whose determination has been reported only for CdGa2S4 crystals. In defect chalcopyrites with small tetragonal distorsion (i. e. a c/a ratio close to 2) like ZnGa2S4 and ZnGa2Se4, one expects very small δi parameters and ion distances cfose to the zincblende ideal case. The study of the local distortion was the main purpose of this EXAFS work.