Effect of sputtering power on structural, cationic distribution and optical properties of Mn2Zn0.25Ni0.75O4 thin films

Abstract

•We investigate the synthesis of Mn2Zn0.25Ni0.75O4 (MZN) thin films by radio frequency (RF) sputtering method at different sputtering powers. The variation of the film morphology, the crystalline structure, the cationic distributions and the optical properties are reported and explained by the variation of the film growth rate. Scanning electron microscopy results indicate that a too fast growth rate of the film results in dense surface defects or the degradation of the film crystallinity. X-ray photoelectron spectroscopy analysis suggests that oxygen defects are almost inevitable in such thin films deposited by RF sputtering. At a moderate (120 W) sputtering power the Mn2+ content increases 10–20% and the Mn4+ content is accordingly reduced. The detailed cationic configuration is proposed, where Zn2+ ions occupy both the tetrahedral site and the octahedral site. Raman and spectroscopic results allows asserting the relation between Mn valence states and the sputtering power.