Scanning tunneling microscopy and spectroscopy of ion-bombarded Si(111) and Si(100) surfaces

Surfaces of Si(111)-(7×{}7) and Si(100)-(2×{}1) were bombarded by 3-keV Ar⁺ ions at doses of {≤}10¹² ions cm^-2 to study the effect of individual ion impacts on the atomic structure of surfaces. Atom-resolved images show damaged regions of missing and displaced atoms. Current-imaging tunneling spectroscopy shows rest-atom states in the bombarded areas on Si(111), in agreement with line-scan measurements indicating a monatomic step-height difference between bombarded and unbombarded areas. Upon annealing to 750 ^∘{}C for 2 min, complete (7×{}7) was restored for the bombarded Si(111) surface whereas ordering of vacancies into line defects was observed for Si(100).