Auger electron angular distributions from Pt(111): The effect of adsorbed iodine monolayers

AbstractComplete Auger electron angular distributions have been measured from a Pt(111) substrate in the presence and absence of three distinct iodine adlattices in order to investigate the effect of adsorbate layer structure on substrate emission. The adlattices investigated were Pt(111)(□3 × □3) R30°‐I, Pt(111)(□7 × □7)R19.1°‐I and Pt(111)(3 × 3)‐I. Three Pt Auger transitions were employed (65, 258 and 1968 eV) to explore the effect of Auger electron kinetic energy. For each kinetic energy investigated, the qualitative features of the substrate angular distributions were the same in the presence and absence of the iodine overlayer, although small quantitative differences were observed. An energy‐dependent quantitative effect was also observed, in which the absolute intensities of the distributions were attenuated substantially at lower kinetic energies but were relatively unaffected at higher kinetic energies. These results show that lower kinetic energy Auger electron angular distributions (<300 eV) are relatively sensitive to the presence of the adlattice, although careful quantitative measurements and analyses are required to observe the differences in the distributions. The origin of attenuation features in the distributions is not yet fully understood, and further experimental and theoretical development is required to relate the observed attenuation features to the surface structure.