Shadow-cone enhanced desorption with angle-resolved secondary ion mass spectrometry detection

Abstract

The shadow cone created by an incident keV bombarding ion is observed to enhance the yield of secondary ions sputtered from the target. This effect may be utilized to determine the bonding configuration of surface atoms in a manner similar to that reported for impact-collision ion scattering spectrometry (ICISS). This new method is utilized to study the bonding of Cl to Ag{110} as the coverage is increased from near zero to the p(2×1) low-energy electron diffraction structure. The results show that the Ag–Cl bond length is extended by 0.4 Å in the isolated atom limit when compared to the p(2×1) coverage due to a large amount of charge transfer between the Ag substrate and the adsorbed Cl atom. This bond length becomes shorter as the coverage increases due to dipole–dipole repulsions. Experimental results are compared to computer simulations of the ion-impact event and the possible advantages of this method over ICISS are discussed.