Non-stoichiometric oxide and metal interfaces and reactions

Bennett, R. A.; Mulley, J. S.; Basham, M.; Nolan, Michael; Elliott, Simon D.; Mulheran, Paul A.

Non-stoichiometric oxide and metal interfaces and reactions

Files

4450.pdf(1.37 MB)

Accepted version

Date

2009-01-17

Authors

Bennett, R. A.

Mulley, J. S.

Basham, M.

Nolan, Michael

Elliott, Simon D.

Mulheran, Paul A.

Publisher

Springer Verlag

Published Version

10.1007/s00339-008-5066-1

Abstract

We have employed a combination of experimental surface science techniques and density functional calculations to study the reduction of TiO(2)(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 similar to 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 Cr(3+) to Cr(4+). Higher temperature processing leads to a loss of Cr from the surface region, indicative of its substitution into the bulk.

Keywords

Scanning tunneling microscopy , Augmented-wave method , Surface structure , Titanium dioxide , Thin films , STM , TiO2(110) , CrO2 , Chromium Dioxide , Transition , Growth , Adsorption , Density functional theory

Citation

Bennett, R. A., Mulley, J. S., Basham, M., Nolan, M., Elliott, S. D. and Mulheran, P. A. (2009) 'Non-stoichiometric oxide and metal interfaces and reactions', Applied Physics A, 96(3), pp. 543-548. doi:10.1007/s00339-008-5066-1