This topical review focuses on recent advances in the understanding of the formation of surface nanostructures, an intriguing phenomenon in ion-surface interaction due to the impact of individual ions. In many solid targets, swift heavy ions produce narrow cylindrical tracks accompanied by the formation of a surface nanostructure. More recently, a similar nanometric surface effect has been revealed for the impact of individual, very slow but highly charged ions. While swift ions transfer their large kinetic energy to the target via ionization and electronic excitation processes (electronic stopping), slow highly charged ions produce surface structures due to potential energy deposited at the top surface layers. Despite the differences in primary excitation, the similarity between the nanostructures is striking and strongly points to a common mechanism related to the energy transfer from the electronic to the lattice system of the target. A comparison of surface structures induced by swift heavy ions and slow highly charged ions provides a valuable insight to better understand the formation mechanisms.

The way conduction electrons respond to ultrafast external perturbations in low dimensional materials is at the core of the design of future devices for (opto)electronics, photodetection and spintronics. Highly charged ions provide a tool for probing the electronic response of solids to extremely strong electric fields localized down to nanometre-sized areas. With ion transmission times in the order of femtoseconds, we can directly probe the local electronic dynamics of an ultrathin foil on this timescale. Here we report on the ability of freestanding single layer graphene to provide tens of electrons for charge neutralization of a slow highly charged ion within a few femtoseconds. With values higher than 10¹² A cm⁻², the resulting local current density in graphene exceeds previously measured breakdown currents by three orders of magnitude. Surprisingly, the passing ion does not tear nanometre-sized holes into the single layer graphene. We use time-dependent density functional theory to gain insight into the multielectron dynamics.

Total low-energy electron yields for the normal incidence interaction of slow, very highly charged ions ${(}^{136}$ ${\mathrm{Xe}}^{\mathit{q}+}$, 21≤q≤51; ${}_{}{}^{232}{}_{}{}^{}\mathrm{Th}_{}^{\mathit{q}+}{}_{}{}^{}$, 51≤q≤80) with a clean gold surface have been determined from the related measured electron emission statistics. The projectile impact energies could be reduced down to the image charge acceleration limit. The electron emission yield was found to increase proportionally with the increasing projectile charge state in all cases studied, suggesting no saturation in the ability of the Au target to provide necessary electrons within the above surface interaction time (e.g., about 280 electrons/projectile for ${\mathrm{Th}}^{79+}$ in less than ${10}^{\mathrm{-}13}$ s). Because of the relatively narrow energy distribution of the incident ions, as well as their very high charge states, the first clear measurements of the image charge acceleration from electron emission yields could be performed. Results of a quantitative study of this acceleration are in good agreement with those of a theoretical model based on classical over the barrier transitions (recently developed by J. Burgdörfer et al.).

Electron emission from clean gold under impact of ${\mathrm{H}}^{+}$ or singly charged rare-gas ions in their ground state has been investigated at the kinetic emission threshold, measuring both the emission statistics and total yields by means of counting techniques. As we are able to subtract any contribution from potential emission, we observe kinetic emission well below the threshold for sufficient energy transfer from projectiles onto quasifree metal electrons and relate this contribution to quasimolecular autoionization in close collisions between the neutralized projectiles and metal ion cores.