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

Abstract

Surfaces of Si(111)-(7\ifmmode\times\else\texttimes\fi{}7) and Si(100)-(2\ifmmode\times\else\texttimes\fi{}1) were bombarded by 3-keV ${\mathrm{Ar}}^{+}$ ions at doses of \ensuremath{\le}${10}^{12}$ ions ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}2}$ 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 \ifmmode^\circ\else\textdegree\fi{}C for 2 min, complete (7\ifmmode\times\else\texttimes\fi{}7) was restored for the bombarded Si(111) surface whereas ordering of vacancies into line defects was observed for Si(100).