Ions in high charge states can store several tens of keV of potential energy composed by the sum of binding energies of all missing electrons. When approaching a material, these highly charged ions start to resonantly capture electrons into high-n shells several Ångströms above the surface. Subsequently, these electrons can deexcite through radiative and non-radiative pathways, like Auger-Meitner decay. Close to the material atoms, a two-centre Auger process also contributes to the deexcitation of the projectile, namely the interatomic Coulombic decay (ICD) [1]. ICD is a strongly distance-dependent process and highly efficient for small interatomic separations [2]. This makes the charge exchange behaviour of the ion ultrafast and results in almost complete neutralisation within a (few) monolayer(s) [3]. The ion exit charge state is thus an ideal tool to assess parameters like material thickness: Thin samples lead to higher exit charge states than thicker samples; pores in a sample lead to even higher charge states as the ion-material distance increases and ICD becomes less effective. In our setup, we, therefore, record the exit charge states of highly charged ions after transmission through atomically thin materials [4,5]. Together with a Monte-Carlo-based code simulating the exit charge state pattern for a given sample structure [6], we can use this technique for (indirect) materials analysis. In this talk, I will discuss how we can apply our technique to investigate the structures of carbon nanomembranes.