Preparation of Ordered Vacancy Chalcopyrite Thin Films by RF Sputtering from CuInSe2 Target with Na2Se

Abstract
A new method for preparation of ordered vacancy chalcopyrite (OVC) thin films by rf sputtering is presented. From X-ray diffraction analyses, all thin films prepared from a CuInSe2 and Na2Se mixture target with [Na]/[CuInSe2] ratio above 1% show an OVC structure, and the lattice parameters of the thin films are slightly smaller than that of CuInSe2, suggestive of the OVC model. The optical absorption coefficients above the fundamental band edge exceed 3×104 cm-1 and the optical band gap increases from 1.02 eV to 1.33 eV with increasing [Na]/[CuInSe2] ratio from 0% to 10% in the target.