Nanohillock formation by impact of small low-energy clusters with-surfaces

Results on nanoscale structuring of different substrates (silicon, pyrolytic graphite, indium-tin-oxide) using clusters from 20 to 100 atoms in size formed from gaseous precursors (O2, N2, Ar) at relatively low impact energy up to 15 keV are presented. Images of the substrate surfaces after cluster collisions obtained using atomic force microscopy (AFM) show the formation of hillocks from a few to 15 nm height with a basal diameter from 50 to 300 nm depending on implantation conditions. The shape and size of the structures are found to be a function of the cluster size and species, implantation energy, impact angle and the type of substrate. A model explaining the hillock formation is discussed.