Influence of the chemisorption state on the charge distribution of low energy Si scattered from I adatoms

The ion fractions of 5 keV Si+ ions singly scattered from iodine adatoms adsorbed on Al(1 0 0), Si(1 1 1) and pre-oxidized Si(1 1 1) were measured with time-of-flight spectroscopy. A considerable ion yield was observed, which did not change significantly with exit angle or I coverage. The mechanism of ion formation is assigned to valence electron resonant charge transfer (RCT) assisted by promotion of the Si ionization level. The yields are smaller than those of Si scattered from Cs adatoms, however, which suggests that electron tunneling from the occupied chemisorption states of the I adatom provides an additional neutralization channel.