Zooming in on clusters: Novel behaviour of supported metal nanocrystals

Abstract

Nanoparticles are of both fundamental and technological importance since a variety of novel phenomena may be observed when characteristic length scales approach atomic dimensions. The large surface area:volume ratio of nanocrystals contributes to enhanced reactivity, and characterization is often complicated by concerns over contamination. Our studies have aimed at studying simple, model cluster systems under dean conditions in order to understand active mechanisms of materials transport and behaviour on a nanometre scale. We have developed an ultra-high-vacuum transmission electron microscope with in situ magnetron sputtering permitting cluster generation and deposition upon electron transparent samples mounted inside the microscope. Using this system we have observed novel interactions between supported clusters of Cu and Ag deposited on the clean (001) Cu surface. Molecular dynamics simulations of cluster:substrate impacts have been performed and we discuss the results of these simulations, and the use of electron microscope image simulation programs to interpret the complex data sets derived.