Angular anisotropy in ion-surface charge transfer

We have measured the charged fraction of scattered Ne atoms during the scattering of 4500-eV Ne+ by two-dimensional layers of arsenic epitaxially grown on Si(100) and Si(111) substrates. We found that the charged fraction depends on the takeoff angle of observation, and is consistent with electron transfer to and from the valence band. No azimuthal dependence was observed. The surface electron behaves like a featureless flat band in the charge transfer, in spite of the known corrugations of the charge density on the surfaces. © 1990 The American Physical Society.