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.