Spatial and RF power dependence of the structural and electrical characteristics of copper zinc tin selenide thin films prepared by single elementary target sputtering

The spatial variations of the structural, optical and electrical properties of Cu2ZnSnSe4 thin films grown by radio-frequency (RF) magnetron sputtering across a distance of 60 mm were investigated as a function of the discharge power. Noticeable changes in the deposition rate and elemental distribution were observed in the as-deposited films at the central and near-edge regions. After annealing in a Se atmosphere, the dependence of the phase evolution and electrical properties on the spatial position and power was also evident. Deposition at a low power of 30 W seems to be more promising in generating dominant Cu2ZnSnSe4 phase with well-packed crystallites on the surface. On the other hand, deposition at higher power tended to result in a significant portion of a secondary SnSe2 phase, which is responsible for the higher optical band gap and lower electrical resistivity, depending on the specific region of the film.