Kelvin probe force microscopy measurements of gold nanoclusters (0.04–1.5 ML) deposited on (001) surfaces of UHV-cleaved NaCl and KCl are presented. Groups of clusters exhibit a uniform bright contrast, which varies, however, from group to group. These phenomena are most likely due to charges in the clusters, which got charged from charges of the clean surface produced by the cleavage. The uniform contrast in cluster groups might be due to tunneling processes of charges between clusters. Measurements after a charge injection into a cluster show indeed a possible exchange of charges in cluster rows, which the authors evaluate with simple calculations.
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The cantilevers were not treated by an ion bombardment or by flashing in UHV so that the end of the tips carried a native oxide layer (insulating). A charge exchange between tip and cluster can be rouled out.
