Effects of Cs-adsorption on the scattering of low energy hydrogen ions from HOPG

The results of a study of the scattering of low energy (∼300 eV) H2+ from clean and cesium dosed highly-oriented pyrolytic graphite (HOPG) are presented. The measurements demonstrate that Cs adsorption does not result in significant structural changes to the graphite surface, but does alter the electronic properties as evidenced by a change in the work function. As a result, dissociative neutralization of the incoming molecular ions is enhanced. However, despite having a work function similar to that of Cs-dosed metal surfaces, the cesiated HOPG does not show a comparable increase in negative ion production. Comparison is made with the ion fractions observed from clean and barium dosed polycrystalline diamond samples