Ab-initio simulation of helium-ion microscopy images: The case of suspended graphene

Abstract

Helium ion microscopy (HIM), which was released in 2006 by Ward et. al., provides non- destructive imaging of nano-scale objects with higher contrast than scanning electron microscopy. HIM measurement of suspended graphene under typical conditions was simulated by first-principles time-dependent density functional theory and the 30 keV He+ collision was found to induce the emission of electrons dependent on the impact point. This finding suggests possibility of obtaining a highly accurate image of the honeycomb pattern of suspended graphene by HIM. Comparison with a simulation of He0 under the same kinetic energy showed that electron emission is governed by the impact ionization instead of Auger process initiated by neutralization of He+.