Local structure study of (In0.95−xFexCu0.05)2O3 thin films using x-ray absorption spectroscopy

Abstract

The (In0.95−xFexCu0.05)2O3 (x = 0.06, 0.08, 0.15, and 0.20) films prepared by RF-magnetron sputtering were investigated by the combination of x-ray absorption spectroscopy (XAS) at Fe, Cu, and O K-edge. Although the Fe and O K-edge XAS spectra show that the Fe atoms substitute for the In sites of In2O3 lattice for all the films, the Cu K-edge XAS spectra reveal that the codoped Cu atoms are separated to form the Cu metal clusters. After being annealed in air, the Fe atoms are still substitutionally incorporated into the In2O3 lattice, while the Cu atoms form the CuO secondary phases. With the increase of Fe concentration, the bond length RFe-O shortens and the Debye–Waller factor σ2Fe-O increases in the first coordination shell of Fe, which are attributed to the relaxation of oxygen environment around the substitutional Fe ions. The forming of Cu relating secondary phases in the films is due to high ionization energy of Cu atoms, leading that the Cu atoms are energetically much harder to be oxidized to substitute for the In sites of In2O3 lattice than Fe atoms. These results provide new experimental guidance in the preparation of the codoped In2O3 based dilute magnetic oxides.