An ultrahigh vacuum sputter source for in situ deposition of size-selectedclusters: Ag on graphite

The investigation of supported size-selected clusters by different surface science techniques requires stringent ultrahigh vacuum (UHV) conditions dur ing cluster deposition especially at low temperatures. The existing high-en ergy sputter sources used for cluster production in general do not fulfil t his demand. We therefore have developed, built and tested a new fully bakea ble ultrahigh vacuum-compatible version of the cluster source CORDIS (Cold Reflex Discharge ion Source). As a first application, we present ultraviole t photoemission spectra (UPS) of size-selected Ag, (n = 1...5) clusters gen erated by this new cluster source and deposited on highly oriented pyrolyti c graphite (HOPG). We show evidence for cluster diffusion and island format ion even down to low temperature (T = 70 K). These islands display a polycr ystalline structure. After a short annealing, they are transformed into Ag films with (111) surface orientation.