Comparison of K + and Li + ion scattering from Au nanoclusters deposited on SiOx

The scattering of low energy alkali ions is used to probe the atomic and electronic structures of Au nanoclusters grown onto an untreated silicon (111) wafer. Charge-state-resolved time-of-flight spectra were collected for 2 keV (7)Li (+) and (39)K (+) as a function of Au coverage. The shapes of the spectra are interpreted in terms of the shadow cones formed by incoming Li (+) and K (+) . The differences in neutralization are interpreted in terms of the ionization potentials. The results indicate that nanoclusters displaying quantum size effects are formed upon the initial Au deposition, and they evolve to multilayer nanoclusters after a critical coverage has been reached. When sufficient Au is deposited, a thick film is formed with the properties of the bulk metal.