UHV-Cleaved Single Crystal Ti2O3 (101¯2) by UPS and XPS

Abstract

Ti2O3 is a semiconducting transition-metal oxide with a 0.1 eV bandgap at room temperature and is thus fairly conducting. The conducting nature of the oxide produces a double-peaked structure of the Ti 2p1/2 and 2p3/2 XPS core-level peaks. The sample, which exposes a (101¯2) cleavage face, contains only Ti3+ cations, so the double-peaked structure does not arise from the presence of multiple valence states on the Ti cations. Caution must thus be exercised in interpreting cation 3p core-level spectra from such oxides. [See K. E. Smith and V. E. Henrich, Phys. Rev. B 50, 1282 (1994) for a discussion of the role of final-state screening in XPS core-level line shapes. See also R. L. Kurtz and V. E. Henrich, Surf. Sci. Spectra 5, 172 (1998).] The He I and He II UPS spectra of the valence band region show the large O 2p band and the smaller Ti 3d band just below the Fermi level. The titanium oxides exhibit a wide stoichiometry range (including Magneli phases); Ti2O3 is the most stable lower oxide.