Atomic clusters supported on surfaces represent an interesting system for the study of cluster structural and electronic properties by means of scanning probe microscopies or advanced spectroscopic techniques. A great attention has been focused in particular on metal clusters deposited on atomically flat surfaces to investigate for instance the basic mechanisms of catalysis and their dependence on the structure and size of the clusters.
Among other deposition techniques, nanosecond Pulsed Laser Deposition (PLD) can be successfully employed for the synthesis of clusters and nanostructured films with a great versatility in terms of structure, chemistry and morphology of the deposits. We here report on the pulsed laser deposition and in situ Scanning Tunneling Microscopy (STM) investigation of Pd/PdO clusters on Au(111) surface. Deposition in the presence of an inert background atmosphere (Ar in the 1-100 Pa range) results in the soft landing of the ablated species. In such conditions Pd clusters self-organize on the Au(111)-22x√3 herringbone structure in aligned parallel nanostripes. The morphology of the observed patterns (cluster density, size and alignment) has been investigated as a function of deposition parameters. When increasing the deposited material, Pd clusters tend to self-organize in zig-zag structures which reproduce the underlying Au(111) herringbone structure. On the other hand, when deposition is performed in an oxygen containing atmosphere, palladium oxide clusters are obtained, as revealed by Scanning Tunneling Spectroscopy (STS) measurements. The PLD flexibility in the production of Pd/PdO clusters with different size and the possibility to realize nano patterns constituted by self-organized clusters on a surface may be of interest e.g. in view of nanoelectronic applications.
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