In an attempt to identify the fundamental processes that influence ion transport through metallic surface layers, we have studied the transmission of O
+ ions through discontinuous Au films adsorbed on TiO
2(110). A low energy (< 10 eV) O
+ ion beam is generated via electron stimulated desorption when an Au-dosed TiO
2(110) substrate is bombarded with a focused 250 eV electron beam. Low energy ion scattering data indicate that Au evaporated under ultrahigh vacuum conditions at 300 K forms three-dimensional clusters on TiO
2(110). As the Au coverage increases, the formation of Au clusters on TiO
2(110) blocks a fraction of the TiO
2 surface and the O
+ yield is attenuated. However, for high coverages (≥30% Au covered substrate) the O
+ signal decreases at a faster rate than the TiO
2 open area fraction. We attribute the attenuation of the O
+ yield for high Au coverages mainly to blocking of O
+ by Au clusters, to deflection of trajectories by the image force between ions and Au clusters, and to charge transfer between desorbing O
+ and neighboring Au clusters.
相似文献