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 ass isted deposition (IBAD) on Pt(111) have been studied by scanning tunne ling 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 e qual to 200 K. The increase is due to nucleation at ion impact induced adatom clusters. As a consequence of the increased island number dens ity, the lateral dimensions of the film microstructure are decreased. In contrast, at T less than or equal to 70 K where the adatom diffusio n is thermally inhibited the simultaneous ion bombardment leads to a d ecreased island number density due to ion impact induced adatom mobili ty. Thin Pt-films grown with ion assistance at T = 50 K exhibit an imp roved epitaxy compared to the rather amorphous Pt-films grown by conve ntional vapor phase deposition at this temperature.