Thin alumina films on Ni3Al(111): A template for nanostructured Pd cluster growth

The growth of vapor deposited palladium on a well-ordered thin alumina film grown on a Ni3Al(111) surface was studied as a function of the sample temperature during deposition and the palladium flux. The superstructure of the oxide film turns out to be an excellent template for the growth of nanostructured palladium cluster arrays. By taking advantage of the growth steering properties of the alumina film we were able to prepare nearly perfectly ordered hexagonal arrays of palladium clusters with a uniform distance of 4.5 nm between the particles. Furthermore the dependence of the cluster height and diameter on the sample voltage as measured by STM has been investigated. In the range between 0.7 V and 2.0 V the measured cluster heights are nearly independent of the sample voltage whereas at voltages higher than 2 V they are continuously decreasing.