Production and Growth Mechanisms of Pd Nanoclusters

Size-selected palladium nanoclusters have been produced by dc sputtering and inert gas condensation technique using mixtures of argon and helium gases. By controlling the source parameters, it was possible to produce Pd nanoclusters with size in the range of 2-10 nm. Transmission electron microscopy (TEM) images were used to confirm the produced sizes of nanocluster. It was found that increasing the percentage of helium to argon have two main effects: i) decreases the nanocluster size as a result of the high drift velocity of helium, and ii) decreases the number of measured nanoclusters due to the low sputtering yield of helium. Since He gas is primarily responsible for the cluster-condensation process, its partial pressure can be used to control the nanoclusters growth. The source parameters and their effects on the size and number of nanoclusters are of great importance in understanding the Pd nanoclusters growth mechanism.