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J. Balajka, U. Aschauer, S. Mertens, A. Selloni, M. Schmid, U. Diebold:
"Surface Structure of TiO₂ Rutile (011) Exposed to Liquid Water";
Journal of Physical Chemistry C, 121 (2017), 26424 - 26431.

The rutile TiO2(011) surface exhibits a (2 × 1)
reconstruction when prepared by standard techniques in
ultrahigh vacuum (UHV). Here we report that a restructuring
occurs upon exposing the surface to liquid water at room
temperature. The experiment was performed in a dedicated
UHV system, equipped for direct and clean transfer of samples
between UHV and liquid environment. After exposure to liquid
water, an overlayer with a (2 × 1) symmetry was observed
containing two dissociated water molecules per unit cell. The
two OH groups yield an apparent "c(2 × 1)" symmetry in
scanning tunneling microscopy (STM) images. On the basis of
STM analysis and density functional theory (DFT) calculations, this overlayer is attributed to dissociated water on top of the
unreconstructed (1 × 1) surface. Investigation of possible adsorption structures and analysis of the domain boundaries in this
structure provide strong evidence that the original (2 × 1) reconstruction is lifted. Unlike the (2 × 1) reconstruction, the (1 × 1)
surface has an appropriate density and symmetry of adsorption sites. The possibility of contaminant-induced restructuring was
excluded based on X-ray photoelectron spectroscopy (XPS) and low-energy He+ ion scattering (LEIS) measurements.