Cluster size dependence of Pt core-level shifts for mass-selected Pt clusters on TiO2(110) surfaces

Abstract

In order to examine cluster size dependence, mass-selected platinum clusters, Ptn (n=2–5, 7, 8, 10, 15), were deposited on TiO2(110) surfaces at room temperature under soft landing conditions, and their core levels were investigated by x-ray photoelectron spectroscopy. Pt core-level shifts with cluster size are observed. The binding energies of Pt 4f7/2 decrease steeply with increasing cluster size up to n=7 for Ptn and decrease gradually for n≥8. This inflection point (n=8) agrees well with the cluster size at a geometric transition (planar-to-three-dimensional) seen with scanning tunneling microscopy (STM) [N. Isomura, X. Wu, and Y. Watanabe, J. Chem. Phys. 131, 164707 (2009)]. It was found that the core-level shifts of mass-selected Pt clusters deposited on TiO2 are closely correlated with cluster geometries determined directly by atomic-resolution STM imaging.