Charge exchange and energy loss of slow highly charged ions transmitted through 2D materials

Slow highly charged ions carry a large amount (several 10 keV) of potential energy, which gets released by target excitation and secondary particle emission upon impact on a solid surface. The energy release can trigger permanent material modifications on semi-conducting and insulating materials [1]. To understand the energy release mechanism and get information on it’s time scale, we use freestanding 2D materials, limiting the interaction time of the ions upon transmission to a few femtoseconds. We detect the ions after the interaction by means of charge state, energy, and angle resolved detection techniques. Further, we detect emitted secondary electrons in coincidence with a particular charge exchange.
Using freestanding single layer graphene, our experimental findings revealed an ultrafast charge exchange and projectile de-excitation mechanism [2,3]. We also determined the in-plane current density in the material, which is transiently active to supply electrons to the ion, to be in the order of 1012A/cm2. Still, graphene is able to sustain these large current densities for a fs-time-scale without rupture. Here we go one step further and present results of ion transmission spectroscopy of single layer hBN and MoS2, which are insulating and semi-conducting, respectively.