Estimating the range of influence of point defects on Cu (110) surface states

By utilizing reflection anisotropy spectroscopy (RAS) and scanning tunneling microscopy (STM) measurements of the ion-bombarded Cu (110) surface at low temperatures, we have developed a simple methodology for estimating the effective surface area over which irradiation-induced defects perturb surface states, leading to a reduction in the intensity of the 2.1 eV RAS peak of this surface. Each composite defect decorating an ion-impact site quenches the RAS signal in proportion to an area equivalent to approximately 170 unit cells. We estimate that an atomic defect has an effective RAS cross section with area approximately equal to that of a circle with a radius of 0.75 nm, an area equivalent to that of around 19 unit cells. Accurate determination of the coverage and spatial distribution of surface defects is a prerequisite for a coherent analytical approach to modeling the RAS data of this system.