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).
Zandvliet, H. J. W., Elswijk, H. B., van Loenen, E. J., & Tsong, I. S. T. (1992). "Scanning tunneling microscopy and spectroscopy of ion-bombarded Si(111) and Si(100) surfaces". Physical Review B (Condensed Matter), 0(46), 7581-7587. https://doi.org/10.1103/PhysRevB.46.7581