TiO${}_x$ clusters on atomically flat Au(111) films have been investigated by means of scanning tunneling microscopy and scanning tunneling spectroscopy. We present measurements of both the morphology and the electronic properties of these clusters. First, pure Ti clusters are produced in the gas phase and are deposited onto a clean Au(111) surface under controlled ultrahigh vacuum conditions. Next, the clusters are oxidized. Then, scanning tunneling microscopy measurements are performed before and after annealing up to high temperatures (970 K), indicating a high thermal stability of the deposited clusters. Scanning tunneling spectroscopy reveals an $n$-type semiconductorlike gap in the TiO${}_x$ cluster density of states. Local influence of the clusters on the electronic surface state of the Au(111) substrate is observed, which is relevant for catalytic cycles where certain steps of the cycles take place at the metal-oxide interface.

• Received 8 December 2010

DOI:https://doi.org/10.1103/PhysRevB.83.155433