Hot electrons induced by slow multiply charged ions

The dissipation of energy following the impact of multiply charged ions on a polycrystalline metal surface was studied using thin film metal–insulator–metal junctions as targets. The ions hit the top Ag layer of a Ag–AlOx–Al junction, where they excite electrons and holes. A substantial fraction of these charge carriers is transported across the insulating barrier and can be detected as an internal current in the bottom Al layer. The effects of potential and kinetic energies on this tunneling yield are investigated separately by varying the charge state of the Ar projectile ions from 2+ to 8+ for kinetic energies in the range from 1 to 12 keV. Per impinging ion yields of typically 0.1–1 electrons are measured within the thin film tunnel junction. The tunneling yield is found to scale linearly with the potential energy of the projectile. In addition, the tunneling yield shows a strong dependence on the internal barrier height which can be modified by an external bias voltage.