Ar+-ion sputtering-induced surface topography development on aluminium

The surface topography of aluminium after bombardment with a mass-separated obliquely incident Ar+ beam while simultaneously supplying gold or tungsten seeds, as well as under unseeded conditions, was studied by scanning electron microscopy. The sputtered topography was characterized mainly by cones. It was noted that seeding did not necessarily always enhance the cone population, as is widely believed. The expression for the cone apex angle derived from the first-order erosion theory for normal cones was found to predict equally well that for oblique cones. The formation of tailed cones, coalescence of closely packed cones, bending of cones and disintegration of the cone apex were observed and are discussed. Finally, the corrugated terraced morphology developed on some grains was similar in nature to that observed on semiconductors rendered amorphous under ion bombardment. (Author)