Zooming in on clusters: novel behaviour of supported metal nanocrystals

Nanoparticles are of both fundamental and technological importance since a variety of novel phenomena may be observed when characteristic length scale s approach atomic dimensions. The large surface area:volume ratio of nanocr ystals contributes to enhanced reactivity, and characterization is often co mplicated by concerns over contamination. Our studies have aimed at studyin g simple, model cluster systems under clean conditions in order to understa nd active mechanisms of materials transport and behaviour on a nanometre sc ale. We have developed an ultra-high-vacuum transmission electron microscop e with in situ magnetron sputtering permitting cluster generation and depos ition upon electron transparent samples mounted inside the microscope. Usin g this system we have observed novel interactions between supported cluster s 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.