High-resolution imaging of gold clusters on KBr(001) surfaces investigated by dynamic scanning force microscopy

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Abstract
Dynamic scanning force microscopy (dynamic SFM) images of (001) surfaces of KBr which have been prepared by cleavage and further decorated by nanometre-sized gold clusters in UHV are presented. During scanning we could achieve atomic resolution on the KBr substrate surface; however, the clusters mostly appeared as hemisphere-like or fuzzy objects exhibiting only a few details of their internal structure. We performed force spectroscopy measurements above single clusters which might point to a charging of the clusters. We anticipate that mainly a long-range electrostatic interaction between the cluster and the macroscopic tip apex determines the appearance of the clusters. Information on the interior of the clusters can be gained only for short tip–cluster distances in the presence of a short-range, chemical interaction between the cluster and the tip atoms closest to the surface.