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 an in-situ combination of ultraviolet photoelectron spectroscopy (UPS) and scanning tunneling spectroscopy (STS). For both techniques we obtained an energy resolution in the range of 10 meV employing low sample temperatures. Dynamic final-state effects together with averaging over a cluster-size distribution result in characteristic spectral shapes in UPS, which can be understood referring to STS data taken on individual clusters. Finally, directions for future experiments are pointed out. Received: 13 April 2000 / Accepted: 6 November 2000 / Published online: 9 February 2001