Ab initio and experimental studies of chlorine adsorption on the rutile TiO2 (110) surface -: art. no. 125411

We report a comprehensive study on the adsorption of Cl on the clean rutile TiO2 (110) (1x1) surface. STM and photoemission spectroscopy results are compared to ab initio results. At room temperature, Cl adsorbs dissociatively and binds to the fivefold coordinated Ti atoms in an on-top configuration. The calculations predict energetically more favorable adsorption on a reduced surface, where bridging oxygen atoms are missing in a (1x4) geometry. Experimental photoemission data indicate a quenching of the oxygen-vacancy-related defect state upon chlorine adsorption at room temperature, in agreement with the theoretical results. Chlorine atoms appear as bright, extended spots in experimental empty-states STM images. Calculations of density-of-states contours indicate that Ti states underneath the Cl atoms are predominantly responsible for the tunneling current. When chlorine is dosed onto a hot surface, a replacement of bridging oxygen atoms is observed in addition to features of unidentified structure and stoichiometry. The experimental results on the change in work function and shift of Cl core levels agree semiquantitatively with calculations of different test geometries.