Clusters on surfaces: high-resolution spectroscopy at low temperatures

With controlled growth in nanometer-sized pits we produced silver and gold clusters on a graphite surface. We give a summary of the preparation method and discuss the scanning tunneling imaging and the crystalline orientation of the clusters. The electronic structure of the clusters was studied by a n in-situ combination of ultraviolet photoelectron spectroscopy (UPS) and s canning tunneling spectroscopy (STS). For both techniques we obtained an en ergy resolution in the range of 10 meV employing low sample temperatures. D ynamic final-stars effects together with averaging over a cluster-size dist ribution result in characteristic spectral shapes in UPS, which can be unde rstood referring to STS data taken on individual clusters. Finally. directi ons for future experiments are pointed out.