Surface structure studies of Cl adsorption on Ag{001} using energetic ion beams

Angle-resolved SIMS experiments have been employed to study the bonding geometry of Cl on Ag{001}. The procedure was to bombard the target with 2 or 3 keV Ar⁺ ions in the low dose mode at various incident angles and to measure the desorption of Ag⁺ or Cl^- ions at various detection angles. For the case of the c(2 × 2)-Cl/Ag{001} structure, azimuthal angle distributions of both Ag⁺ and Cl^- ions indicate that the Cl atom binds in the four-fold hollow site. Measurement of the polar angle distributions suggests that the Cl overlayer is above the surface plane, ruling out the formation of an epitaxial AgCl layer. The AgCl bond-length was determined to be 2.60 ± 0.04 Å using shadow-cone enhanced desorption. With this measurement the angle of incidence of the ion beam is varied until the shadow-cone created by a target Cl atom intersects a nearby Ag atom. The result is in agreement with earlier LEED experiments.