Silver Growth on TiO2(110) (1 × 1) and (1 × 2)

The growth and interaction of Ag with the TiO2(110) (1 × 1) and (1 × 2) surfaces were studied by X-ray photoemission spectroscopy (XPS), low-energy ion scattering (LEIS), low-energy electron diffraction (LEED), and scanning tunneling microscopy (STM). At 300 K, both LEIS and STM data indicate that Ag grows three-dimensionally on the (1 × 1) and (1 × 2) surfaces; no strong chemical interaction between Ag and TiO2 was detected by XPS. At 0.05 ML Ag exposure (corresponding to a cluster diameter of 2.0−3.5 nm), the Ag 3d core level binding energy shifts to 1.2 eV higher than that for metallic (bulk) Ag. In addition, the Ag 3d peak width increases with decreasing cluster size. The binding energy shifts and peak broadening are attributed to both initial and final state effects. The valence band as a function of Ag exposure suggests that a metal-to-nonmetal transition occurs within the Ag clusters at exposures between 0.5 and 1 ML (3.5−4.4 nm). No change in the cluster growth mode was observed upon Ag deposition onto an Ar ion-bombarded TiO2 surface. Also no strong interaction was observed between substrate Ti3+ states (induced via ion bombardment) and the Ag clusters. Significant sintering of the Ag clusters was observed upon annealing from 100 to 300 K.