Temperature dependence of the neutralization of low energy K+ ions scattered from Au nanoclusters on SiO2

Neutralization during the scattering of 2.5 keV K+ from Au nanoclusters on SiO2/Si(1 1 1) is investigated as a function of post-deposition surface temperature. Small nanoclusters are formed by deposition at low temperature (115 K), as evidenced by a larger neutralization probability for singly scattered K+ as compared to scattering from Au metal. The neutralization probability in scattering from small clusters is found to reversibly decrease with increasing surface temperature. This contradicts the general understanding of charge exchange for alkali low energy ion scattering, however, which predicts that higher temperatures should increase the neutralization. Temperature-dependent changes in surface composition or structure are ruled out as causes, while additional experiments are proposed to resolve the discrepancy.