Effect of TiO 2 Film Thickness on the Stability of Au 9 Clusters with a CrO x Layer.

Radio frequency (RF) magnetron sputtering allows the fabrication of TiO 2 films with high purity, reliable control of film thickness, and uniform morphology. In the present study, the change in surface roughness upon heating two different thicknesses of RF sputter-deposited TiO 2 films was investigated. As a measure of the process of the change in surface morphology, chemically -synthesised phosphine-protected Au 9 clusters covered by a photodeposited CrO x layer were used as a probe. Subsequent to the deposition of the Au 9 clusters and the CrO x layer, samples were heated to 200 ℃ to remove the triphenylphosphine ligands from the Au 9 cluster. After heating, the thick TiO 2 film was found to be mobile, in contrast to the thin TiO 2 film. The influence of the mobility of the TiO 2 films on the Au 9 clusters was investigated with X-ray photoelectron spectroscopy. It was found that the high mobility of the thick TiO 2 film after heating leads to a significant agglomeration of the Au 9 clusters, even when protected by the CrO x layer. The thin TiO 2 film has a much lower mobility when being heated, resulting in only minor agglomeration of the Au 9 clusters covered with the CrO x layer.