Mixed-valence formation in highly oriented Ti-doped iron oxide film

Abstract

Ti⁴⁺-doped α-Fe₂O₃ films have been prepared by the sol–gel method. The dispersed state of the doped Ti ions in the film was compared with a Ti-doped powder prepared by a coprecipitation method in order to examine homogeneous dispersion effects of the sol–gel method. X-Ray diffraction (XRD) showed the highly oriented structure of the sol–gel-derived Ti-doped α-Fe₂O₃ films. Ti doping can control the electrical conductivity of the film effectively. X-Ray photoelectron spectroscopy (XPS) valence band spectra evidenced the formation of the mixed valence with Ti doping. The data on electrical conductivity changes with doping indicated a distinct difference of Ti-dopant dispersion in the film and powder. The depth profile of the Ti dopants from the surface was measured with XPS using Ar-ion etching; the Ti dopants are more homogeneously distributed in the sol–gel-derived film than in the powder.