Complex roughening of Si under oblique bombardment by low-energy oxygen ions

Surface roughening of Si under bombardment with oblique O2+ beams at energi es between 0.5 and 2 keV was studied with atomic force microscopy and secon dary ion mass spectrometry. At beam energies of 1 keV and below, the genera l features of the topography and the magnitude of the roughness depended cr itically on the incidence angle. In most cases there were two angular range s where surface roughening was strong, in-between and at grazing incidence roughening was minimal. Apart from the known topographical features-ripples and irregular bumps-triangular elevations were observed. In many cases, th e local angle of incidence at the beam-facing slopes of the ripples corresp onded to the maximum in sputter rate. Furthermore, the average distance bet ween adjacent ripples increased with depth until saturation. It is conclude d that the complexity in the topographies is caused by a delicate balance b etween several roughening and smoothing mechanisms. (C) 2001 American Vacuu m Society.