Real-time Raman measurements were carried out on a (111) surface during bombardment with 5keV He+, Ar+ and Kr+ ions. It was found that the intensity of the optical phonon peak at 521/cm decreased with increasing fluence, and that the rate of intensity reduction increased with increasing ion mass. The reduction in the phonon-line intensity was interpreted as being dominated by the total number of vacancies within the optical penetration depth.

K.Ishioka, K.G.Nakamura, M.Kitajima: Solid State Communications, 1995, 96[6], 387-90