Ne⁺, Ar⁺ and Xe⁺ ion bombardment induced and suppressed topography on Si

The topographic evolution of Si irradiated at room temperature with Ne⁺, Ar⁺ and Xe⁺ ions in the energy range 5-40 keV at 45° to the substrate normal at high ion fluences has been studied. Other than isolated etch pits no topography results from Ne⁺ bombardment at all energies or from Ar⁺ bombardment at 5 and 10 keV. Ar⁺ bombardment at 20 keV, however, initially produces transverse low-amplitude waves which transform, with increasing erosion, into larger amplitude corrugated and facetted wavelike structures. The present data do not conform to existing model predictions but do suggest that, technically, light low energy gas ions can be used to inhibit roughening during sputtering erosion. Xe⁺ ion bombardment, on the other hand, produces clearly-defined transverse wave structures on the surface, which are inimical to sputter-profiling applications. However, Xe⁺ bombardment-induced morphology, when exposed to further 20 keV Ne⁺ or 10 keV Ar⁺ bombardment loses its rippled habit, indicating that such irradiation can be employed to cure the deleterious roughening processes as well as inhibit roughening.