Incident angle dependence in the transient sputtering of an amorphous Si surface by sub-keV O₂⁺ ion bombardment

The transient sputtering of an amorphous Si surface with sub-keV oxygen ion bombardment was studied with medium energy ion scattering (MEIS) spectroscopy and dynamic Monte Carlo simulation. The indepth composition profiles of the incorporated oxygen and sputtering yield change in Si were obtained from in situ medium energy ion scattering spectroscopy. As ion doses increase, the Si surface is thickly oxidized, and the sputtering yield is rapidly reduced. At the initial stage of the sputtering, the surface is continuously swelled owing to an incorporation rate of oxygen higher than the sputtering rate of Si. A dynamic Monte Carlo calculation, which takes into account swelling and diffusion effects, describes the experimental results for the in-depth composition profiles and the transient Si sputtering yield very well. At normal incidence, the surface is swelled rather than etched due to incorporation rate of oxygen atoms higher than surface etching rate, but at grazing incidence, the transient effect can be minimized.