title: (Sub)surface mobility of oxygen vacancies at the TiO2 anatase (101) surface.
abstract: Anatase is a metastable polymorph of TiO2. In contrast to the more widely studied TiO2 rutile, O vacancies (V(O)'s) are not stable at the anatase (101) surface. Low-temperature STM shows that surface V(O)'s, created by electron bombardment at 105 K, start migrating to subsurface sites at temperatures ≥200 K. After an initial decrease of the V(O) density, a temperature-dependent dynamic equilibrium is established where V(O)'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, density functional theory 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.
authors.affiliation: Institute of Applied Physics, Vienna University of Technology, Vienna, Austria.
authors.forename: Philipp
authors.initials: P
authors.lastname: Scheiber
authors.forename: Martin
authors.initials: M
authors.lastname: Fidler
authors.forename: Olga
authors.initials: O
authors.lastname: Dulub
authors.forename: Michael
authors.initials: M
authors.lastname: Schmid
authors.forename: Ulrike
authors.initials: U
authors.lastname: Diebold
authors.forename: Weiyi
authors.initials: W
authors.lastname: Hou
authors.forename: Ulrich
authors.initials: U
authors.lastname: Aschauer
authors.forename: Annabella
authors.initials: A
authors.lastname: Selloni