(Sub)surface mobility of oxygen vacancies at the TiO2 anatase (101) surface

P. Scheiber, M. Fidler, O. Dulub, M. Schmid, U. Diebold, W. Hou, U. Aschauer, A. Selloni

Institut für Angewandte Physik, Technische Universität Wien, 1040 Wien, Austria
Department of Physics, Tulane University, New Orleans, LA, 70118, U.S.A.
Department of Chemistry, Princeton University, Frick Laboratory, Princeton NJ 08544, U.S.A.

Phys. Rev. Lett. 109 (2012) 136103

Anatase is a metastable polymorph of TiO2. In contrast to the more widely-studied TiO2 rutile, O vacancies (VO's) are not stable at the anatase (101) surface. Low-temperature STM shows that surface VO's, created by electron bombardment at 105 K, start migrating to subsurface sites at temperatures ≥ 200K. After an initial decrease of the VO density, a temperature-dependent dynamic equilibrium is established where VO's move to subsurface sites and back again, as seen in time-lapse STM images. We estimate that activation energies for subsurface migration lie between 0.6 and 1.2 eV; in comparison, DFT calculations predict a barrier of ca. 0.75 eV. The wide scatter of the experimental values might be attributed to inhomogeneously-distributed subsurface defects in the reduced sample.

Full text (PDF)

Users with online access to Physical Review B can also access the article at the publisher.

Corresponding author: Ulrike Diebold. (diebold< encoded email address >).