Size-Selected Cluster Deposition and Single-Electron Tunneling, Applied to Catalyst Issues

Abstract : Two related programs of experiments are described. Size-selected metal cluster ion deposition was used to prepare model catalysts, which were then studied by a variety of chemical and physical probes, in situ. Anomalous sintering of atoms on oxide surfaces was observed, and pre-formed clusters were found to be relatively stable with respect to heating and reactant exposure. Methods using ion beam scattering to probe both metal morphology, and adsorbate binding geometry were developed. The second thrust was using single-electron tunneling to try to image and probe the electronic structure of metal clusters on insulating supports. Significant new approaches to the methodology were developed, including dynamic tunneling force microscopy, which offers STM-spatial resolution and spectroscopy capabilities, but uses only a single electron that is tunneled rapidly back and forth between the sample and the microscope tip.