UV‐Vis Spectroscopic and NEXAFS Studies of Polycrystalline Zinc Ferrite Films

Abstract

In this study, zinc ferrite films with thicknesses about 270 nm are deposited using radio frequency sputtering method on fused quartz substrates under a base pressure of 5 × 10−6 Torr and an oxygen pressure of 40 mTorr during deposition. Films are annealed at 200, 400, and 600 °C for 1 h. X‐ray diffraction studies envisage the polycrystalline nature of as‐grown film. With the increase of annealing temperature, the crystallinity of these films improves. The optical band‐gap of these films increases with the increase of annealing temperature. Fe L‐edge and Zn L‐edge near‐edge X‐ray absorption fine‐structure (NEXAFS) measurements envisage that Fe and Zn ions remain in 3+ and 2+ state, respectively, in the deep of these films, however, the valence state of Fe ions at the surface of these films is modified. O K‐edge NEXAFS measurements reveal the improvement of metal–oxygen hybridized states. Therefore, it can be proposed that the optical band‐gap of these films is influenced by the improved crystallization and metal–oxygen hybridization with annealing temperature.

A Sensitive Visible Light Photodetector Using Cobalt-Doped Zinc Ferrite Oxide Thin Films

“…The ZnFe 2 O 4 thin films with 5 at % Co show higher absorbance than those with 10 at % Co at 350–750 nm. The optical band gap of the samples can be evaluated from the Tauc’s plot, with the absorption coefficient (α) calculated from the absorbance spectra using eq where Abs and t stand for the absorbance and thin film thickness, respectively. The graph of (α h ν) 2 versus h ν was also plotted, and the extrapolation of these curves (shown by gray dotted lines) to the hν -axis was used to determine the optical band gap, as shown in Figure c.…”