ANGULAR ANISOTROPY OF SURFACE MULTIPLE-SCATTERING - ANALYSIS OF CARBON CONTAMINATION ON AN IR(110) SURFACE

Multiple scattering (MS) effects resulting from the successive collisions of 4 keV Ar+ with iridium and carbon atoms were investigated on a carbon contaminated Ir{110} surface. The experimental measurements were made at different crystallographic directions. The results show that (i) detection of MS provides an extremely sensitive method for monitoring the surface contamination and (ii) the MS intensity exhibits strong anisotropies as a function of incident angle (alpha), azimuthal angle (delta), and scattering angle (THETA). Combined with Monte Carlo computer simulations, the MS angular anisotropies allow an identification of the scattering and recoiling processes and provide unique structural information regarding the location of the carbon impurities on the surface. The experimental results and simulations are consistent with carbon impurity sites located inside the [110BAR] troughs and above the surface. The carbon coverage is estimated to be approximately 0.5 ML.