Non-stoichiometric oxide and metal interfaces and reactions

R.A. Bennett, J.S. Mulley, M. Basham, M. Nolan, S.D. Elliott, P.A. Mulheran

Research output: Contribution to journalArticle

3 Citations (Scopus)

Abstract

We have employed a combination of experimental surface science techniques and density functional calculations to study the reduction of TiO2(110) surfaces through the doping with submonolayer transition metals. We concentrate on the role of Ti adatoms in self doping of rutile and contrast the behaviour to that of Cr. DFT+U calculations enable identification of probable adsorption structures and their spectroscopic characteristics. Adsorption of both metals leads to a broken symmetry and an asymmetric charge transfer localised around the defect site of a mixed localised/delocalised character. Charge transfer creates defect states with Ti 3d character in the band gap at ∼1-eV binding energy. Cr adsorption, however, leads to a very large shift in the valence-band edge to higher binding energy and the creation of Cr 3d states at 2.8-eV binding energy. Low-temperature oxidation lifts the Ti-derived band-gap states and modifies the intensity of the Cr features, indicative of a change of oxidation state from Cr3+ to Cr4+. Higher temperature processing leads to a loss of Cr from the surface region, indicative of its substitution into the bulk.
Original languageEnglish
Pages (from-to)543-548
Number of pages5
JournalApplied Physics A: Materials Science and Processing
Volume96
Issue number3
DOIs
Publication statusPublished - Aug 2009

Keywords

  • surface science techniques
  • non-stoichiometric oxide
  • metal interfaces

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