Hypervelocity nanoparticle impacts on free-standing graphene: a sui generis mode of sputtering.

The study of the interaction of hypervelocity nano-particles with a 2D material and ultra-thin targets (single layer graphene, multi-layer graphene, and amorphous carbon foils) has been performed using mass selected gold nano-particles produced from a liquid metal ion source. During these impacts, a large number of atoms are ejected from the graphene, corresponding to a hole of ∼60 nm(2). Additionally, for the first time, secondary ions have been observed simultaneously in both the transmission and reflection direction (with respect to the path of the projectile) from a 2D target. The ejected area is much larger than that predicted by molecular dynamic simulations and a large ionization rate is observed. The mass distribution and characteristics of the emitted secondary ions are presented and offer an insight into the process to produce the large hole observed in the graphene.