The (111)-(7 x 7) and (100)-(2 x 1) surfaces were bombarded with 3keV Ar+ ions to doses of up to 1012/cm2. Atomic-resolution images revealed damaged regions, with missing and displaced atoms. Current-imaging tunnelling spectroscopy revealed rest-atom states, in bombarded areas of (111), which agreed with line-scan measurements. It was found that there was a monotonic difference in step-height between bombarded and non-bombarded areas. During annealing (750C, 120s), a (7 x 7) structure was restored to the bombarded (111) surface, whereas the ordering of vacancies into line defects was observed on (100).

H.J.W.Zandvliet, H.B.Elswijk, E.J.Van Loenen, I.S.T.Tsong: Physical Review B, 1992, 46[12], 7581-7