Photon Factory Activity Report 2004 #22 Part B (2005)
Electronic Structure of Condensed Matter

11D/2004G0197

Site-specific photoelectron spectroscopy of FeTiO3 by resonant x-ray excitations
Tatsuo FUJII*1, Yusuke TAKADA1, Miki YAMASHITA1, Makoto NAKANISHI1, Jun TAKADA1,Hideki YOSHIKAWA2
1
Dept. Applied Chemistry, Okayama Univ., Okayama 700-8530, Japan
2
Harima Office, Nat. Inst. for Materials Science, Mikazuki-cho, Hyogo 679-5198, Japan

Experimental
The RXPS measurements of FeTiO3 bulk crystals wereperformed at the beam line BL11D of KEK-PF. Before
the measurements the sample surface was filed in vacuum-10(6x10 Torr) to obtain the clean surface. The incident
photon energy for resonant XPS was determined from theTi LII,III and Fe LII, III x-ray absorption spectra of FeTiO3 tomeasure the secondary electron emission yields. TheRXPS were measured at room temperature by using ahemispherical electron analyzer (Scienta SES-200) withthe pass energy of 10 eV. Because of the low photon fluxof BL11D, it took two days to obtain one spectrum.
Results and discussion
Fig. 1 shows the x-ray absorption spectra of FeTiO3 forboth Ti LII,III- and Fe LII, III-edges. The photon energies in ahorizontal axis are nominal values without the energy
calibration. For the Ti 2p-3d resonant XPS, nominal
photon energies of 447 and 453 eV were applied to obtain
the off- and on-resonant condition, respectively. Whilefor the Fe 2p-3d resonant XPS, nominal photon energiesof 707 and 712 eV were applied as well.
Fig. 2 shows the XPS valence-band spectra of FeTiO3as a function of the incident photon energy. The spectrum
using the high-energy excitation source (hν=4,750 eV)
obtained at a beam line BL15XU of SPring-8 is also
indicated for the comparison. The high-energy excitation
spectrum clearly indicated the detailed structures in thevalence-band including the weak intensity close to theFermi level. However the statistics and energy-resolutionsof the obtained on- and off-resonant XPS spectra wereconsiderably wrong. The details in the valence-band werecompletely missing. A well adjusted x-ray source and an98

Users' ReportIntensity (kcount)electron analyzer are required to obtain the useful highresolution valence-band spectra.
16on Ti

Ti LII, III

128off Ti

4440

Intensity (kcount)

Introduction
Hematite (α-Fe2O3) – ilmenite (FeTiO3) solid solution
system is one of the candidates for novel magnetic
semiconductors at room temperature [1]. The electronic
structures of Fe2-xTixO3 are generally considered as themixed valence states between Fe2+ and Fe3+ if the nominal
valence states of Ti are assumed to 4+. However oursystematic study of high-resolution x-ray fluorescence
spectra of various titanium oxides suggested that thevalence states of Ti ions in FeTiO3 seemed to have someTi3+ characters [2]. In order to clarify the real electronicstructures of FeTiO3 we tried to obtain the site-specificvalence-band spectra by means of the resonant x-ray
photoelectron spectroscopy (XPS).

450
460
Photon Energy (eV)8on Fe470

Fe LII, III

6off Fe

4
2700

710
720
Photon Energy (eV)730

Fig. 1. X-ray absorption spectra of FeTiO3.
off-Ti (hν=447 eV)

on-Ti (hν=453 eV)

off-Fe (hν=707 eV)

on-Fe (hν=712 eV)

ref. (hν=4750 eV)0102030
Binding Energy (eV)40Fig.2. Resonant XPS valence-band spectra of FeTiO3.
References[1] W. H. Butler, et al., J. Appl. Phys. 93, 7882 (2003).
[2] T. Fujii, et al., Nanotechnology in SPring-8, 2004B, inpress.
* tfujii@cc.okayama-u.ac.jp