Softlanding and STM imaging of Ag (561) clusters on a C (60) monolayer

The low energy deposition of silver cluster cations with 561 (+/- 5) atoms on a cold fullerene covered gold surface has been studied both by scanning tunneling microscopy and molecular dynamics simulation. The special properties of the C-60/Au(111) surface result in a noticeable fixation of the clusters without a significant change of the cluster shape. Upon heating to room temperature we observe a flattening or shrinking of the cluster samples due to thermal activation. Similar changes were observed also for mass selected Ag clusters with other sizes. For comparison we also studied Ag islands of similar size, grown by low temperature deposition of Ag atoms and subsequent annealing. A completely different behavior is observed with much broader size distributions and a qualitatively different response to annealing.