Structure and Epitaxy of Silver/Gold Microclusters on MgO

Abstract

AbstractWe report observations by high resolution electron microscopy of model catalysts produced by impregnating MgO smoke particles with inorganic clusters. With the use of very low beam currents the substrates are of sufficiently low noise that we have been able to image cleanly both single atoms and very small clusters of size l-2nm in sufficient detail to determine their atomic structure. Two types of metal structures are observed: single atoms decorating atomic steps and in a few cases two-dimensional surface rafts, and a population of mainly single crystal with a few multiply twinned particles. The single crystal particles are pseudomorphically epitaxed on the MgO substrates.