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arXiv · 1804.04398

(Sub)surface mobility of oxygen vacancies at the TiO$_2$ anatase (101) surface

Philipp Scheiber·Martin Fidler·Olga Dulub·Michael Schmid·Ulrike Diebold·Weiyi Hou·Ulrich Aschauer·Annabella Selloni
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Abstract

Anatase is a metastable polymorph of TiO$_2$. In contrast to the more widely-studied TiO$_2$ rutile, O vacancies (V$_\mathrm O$'s) are not stable at the anatase (101) surface. Low-temperature STM shows that surface V$_\mathrm O$'s, created by electron bombardment at 105 K, start migrating to subsurface sites at temperatures $\geq$ 200 K. After an initial decrease of the V$_\mathrm O$ density, a temperature-dependent dynamic equilibrium is established where V$_\mathrm O$'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, 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.

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Philipp Scheiber, Martin Fidler, Olga Dulub, Michael Schmid, Ulrike Diebold, Weiyi Hou, Ulrich Aschauer, Annabella Selloni. 2018-04-12. (Sub)surface mobility of oxygen vacancies at the TiO$_2$ anatase (101) surface. https://doi.org/10.1103/physrevlett.109.136103

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