Low energy ion bombardment induced roughening and smoothing of SiO surfaces

Surface roughening and smoothing of SiO by low energy ion bombardment were investigated using in situ energy dispersive x-ray reflectivity. Bombardment of nominally smooth surfaces (initial roughness approx. 0.4 nm) by 1 keV Xe increases the surface roughness linearly with fluence. Bombardment of initially rough surfaces (roughness approx. 1 nm) by 0.2-1 keV H results in an exponential decrease in roughness with fluence at a rate that increases with energy. The smoothing rate has a different energy dependence than the etching rate, ruling out a simple relation between material removal and surface morphology. A H ion induced relaxation mechanism is suggested for the smoothing behavior.