Molecular dynamics (MD) simulations were performed to study the formationprocess of nanopores in a suspended graphene sheet irradiated by usingenergetic ions though a mask. By controlling the ion parameters including mass,energy and incident angle, different kinds of topography were observed in thegraphene sheet. Net-like defective strucutures with carbon atom chains can beformed at low ion fluence, which provides the possibility to functionalize theirradiated sample with subsequent chemical methods; finally a perfect nanoporewith smooth edge appears as the ion fluence is high enough. We found that thedependence of ion damage efficiency on ion fluence, energy and incident angleare different from that predicted by the semi-empirical model based on thebinary-collision approximation, which results from the special structure ofgraphene. Our results demonstrate that it is feasible to fabricate controllednanopores/nanostructures in graphene via heavy ion irradiation.
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