The surface structure of TiO2(110) was re-examined using scanning tunnelling microscopy, especially in terms of its temperature dependence. A dramatic topographic change was observed around 725K, which was most likely due to the oxygen desorption into the gas phase and the simultaneous diffusion of Ti into the bulk. The atomically resolved scanning tunnelling microscopic images revealed a strong dependence upon the tip composition and allow a double-bridging oxygen vacancy to be identified. The nucleation and growth of Pd on the TiO2(110) surface have also been studied at the nucleation stage with atomic resolution. Both dimer and tetramer Pd clusters were observed; however no single Pd atoms were detected. These results supported the so-called classical nucleation model which assumes that only monomers were mobile, whereas dimers were stable nuclei. A marked preferential nucleation and growth of Pd clusters at step edges have also been observed. In addition to topographic structures, the local electronic properties of the Pd clusters were studied to relate cluster structure to electronic composition.

Scanning Tunneling Microscopy Studies of the TiO2 (110) Surface: Structure and the Nucleation Growth of Pd. Xu, C., Lai, X., Zajac, G.W., Goodman, D.W.: Physical Review B, 1997, 56, 13464-82