Nucleation and morphology of homoepitaxial Pt(111)-films grown with ion beam assisted deposition

The nucleation and morphology of thin Pt-films grown with ion beam assisted deposition (IBAD) on Pt(111) have been studied by scanning tunneling microscopy and low energy electron diffraction. In comparison to conventional vapor phase deposition it is found that the simultaneous ion bombardment with Ar+(400eV)- and Ar+(4keV)-ions during deposition drastically increases the island number density at T greater than or equal to 200 K. The increase is due to nucleation at ion impact induced adatom clusters. As a consequence of the increased island number density, the lateral dimensions of the film microstructure are decreased. In contrast, at T less than or equal to 70 K where the adatom diffusion is thermally inhibited the simultaneous ion bombardment leads to a decreased island number density due to ion impact induced adatom mobility. Thin Pt-films grown with ion assistance at T = 50 K exhibit an improved epitaxy compared to the rather amorphous Pt-films grown by conventional vapor phase deposition at this temperature.