Hot electrons induced by (rather) cold ions

TL;DR

This study uses thin film metal-insulator-metal junctions to explore how multiply charged ions transfer potential energy into excited electrons and holes, revealing a linear relationship between potential energy and tunneling yield.

Contribution

It introduces a novel method to measure energy dissipation of cold ions via electron tunneling in metal junctions, highlighting the role of potential energy transfer.

Findings

Tunneling yield scales linearly with ion potential energy.

Yields of 0.1-1 electrons per ion detected in the bottom layer.

Potential energy has a significant impact on electron excitation.

Abstract

Thin film metal-insulator-metal junctions are used in a novel approach to investigate the dissipation of potential energy of multiply charged ions impinging on a polycrystalline metal surface. The ion-metal interaction leads to excited electrons and holes within the top layer. A substantial fraction of these charge carriers is transported inwards and can be measured as an internal current in the thin film tunnel junction. In Ag-AlOX-Al junctions, yields of typically 0.1-1 electrons per impinging ion are detected in the bottom Al layer. The separate effects of potential and kinetic energy on the tunneling yield are investigated by varying the charges state of the Ar projectile ions from 2+ to 9+ for kinetic energies in the range from 1 to 12 keV. The tunneling yield is found to scale linearly with the potential energy of the projectile.