STM INVESTIGATIONS ON COMPACT AU55 CLUSTER PELLETS

We have investigated the topography and the local electronic structure of compact Au55 cluster pellets by scanning tunnelling microscopy (ST M) at room temperature. Surface topography and differential conductivi ty (partial derivative I/partial derivative V) were measured simultane ously. Additionally, I(V) curves were taken at particular locations on the surface. The topographies generally show largely ideally arranged individual clusters, while also a few agglomerates of several cluster s could be observed. The surfaces exhibit a nearly homogeneous differe ntial conductivity, whereby some clusters produce a striking ''oversho ot''. I(V) curves for various probe-sample separations show a strong d ependence on the tunnelling impedance and are highly non-linear for la rge probe-sample separations.