Observation and destruction of an elusive adsorbate with STM: O${}_2$/TiO${}_2$

Abstract

When a slightly defective rutile TiO${}_2$(110) surface is exposed to O${}_2$ at elevated temperatures, the molecule dissociates at defects, filling O vacancies (\ov) and creating O adatoms (\oad) on {\tifc} rows. The adsorption of molecular O${}_2$ at low temperatures has remained controversial. Low-Temperature Scanning Tunneling Microscopy (LT-STM) of O${}_2$, dosed on TiO${}_2$(110) at a sample temperature of $\approx$ 100 K and imaged at 17 K, shows a molecular precursor at \ov as a faint change in contrast. The adsorbed O${}_2$ easily dissociates during the STM measurements, and formation of \oad's at both sides of the original \ov is observed.

Submitted to Physical Review Letters. 4 pages, 2 figures

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