Field-induced migration of oxygen vacancies towards the surface of TiO2 anatase(101)

Full text: TiO2 is a material known mainly for its photocatalytical properties but it has applications in many other fields – in photoelectrochemical cells, Li-ion batteries, and, possibly, in memristors for data storing. While the rutile phase of TiO2 is well investigated in surface science, the metastable anatase phase is used in most applications and generally considered the technologically more relevant polymorph. Oxygen vacancies (VO) are more favorable in bulk than at the surface of TiO2 anatase(101). As a consequence, an as-prepared anatase(101) surface does not contain any surface VO's. These can be created at low temperature either by desorbing surface O atoms by means of electron bombardment, or by pulling subsurface VO's to the surface by means of electric field of the STM tip. We show that O2 adsorption on the anatase(101) surface also promotes migration of bulk VO's towards the surface. (author)