The complex formation of ripples during depth profiling of Si with low energy, grazing oxygen beams

Abstract

Surface roughening of Si under low-energy (0.5–2.0 keV) O2+ bombardment at incidence angles between 45° and 80° has been studied. Surface roughening occurred already at an erosion depth of only a few tens of nanometers. It was found that there were distinctly two angular ranges for sub-keV beams where roughening was strong, and two ranges where it was insignificant. The transition between the different ranges can be very sharp. These observations cannot be explained by the current models for surface roughening. Instead, it is believed that it is the combined sputtering rate dependence on both the surface topography and the oxygen content that determines the occurrence of roughening.