  We report on how different cluster deposition regimes can be obtained and
observed by in situ Scanning Tunneling Microscopy (STM) by exploiting
deposition parameters in a pulsed laser deposition (PLD) process. Tungsten
clusters were produced by nanosecond Pulsed Laser Ablation in Ar atmosphere at
different pressures and deposited on Au(111) and HOPG surfaces. Deposition
regimes including cluster deposition-diffusion-aggregation (DDA), cluster
melting and coalescence and cluster implantation were observed, depending on
background gas pressure and target-to-substrate distance which influence the
kinetic energy of the ablated species. These parameters can thus be easily
employed for surface modification by cluster bombardment, deposition of
supported clusters and growth of films with different morphologies. The
variation in cluster mobility on different substrates and its influence on
aggregation and growth mechanisms has also been investigated.
