Secondary ion emission from Cu(1Â 0Â 0) surfaces with atomic adsorbates (N, O, Cl, S and Br)

Several targets that consist of atomic species X (X = N, O, Cl, S, Br) adsorbed at hollow sites on the Cu(1 0 0) surface have been examined with low-fluence secondary ion mass spectrometry (SIMS). The positive and negative secondary ion (SI) abundance distributions, which show a range of characteristics, have been discussed with the aid of thermochemical data derived from ab initio calculations. In positive SIMS, CuX+ is never observed, while the only heteronuclear (mixed-atom) SI that is observed for all five systems is Cu2X+. In negative SIMS, the dominant heteronuclear species for all systems is CuX2-, except for N/Cu(1 0 0), which produces no CuNk-, ions. Cu− emission is observed only for O/Cu(1 0 0). By analogy with results from laser ablation studies of O/Cu targets, it is conjectured that Cu− is a daughter product of the gas-phase dissociation of polyatomic Cu-O anion clusters.