2D Materials Under Ion Irradiation: In-situ Experiments and the Role of the Substrate

Helium ion Microscopy (HIM) is frequently used for the fabrication of 2D nanostructures in graphene, MoS 2 and other materials. While some of the experiments are carried out with freestanding materials most of the work is done on supported material. While the defect production is understood for the former case, it is not fully understood in the latter setup. We used a combination of analytical potential molecular dynamics and Monte Carlo simulations to elucidate the role of the different damage channels, namely primary ions, backscattered atoms and sputtered substrate atoms.
Using this approach we looked at the defect production by helium and neon ions in MoS 2 and graphene supported by SiO 2 at typical energies used in HIM. We show that depending on ion species and energy defect production for supported 2D materials can be dominated by sputtered atoms from the support, rather than direct damage induced by the primary ion beam. We also evaluated the consequences of these additional damage mechanisms on the achievable lateral resolution for HIM based defect engineering and nano-fabrication in 2D materials. The obtained results agree well with experimental results obtained by in-situ and ex-situ characterization of defects in graphene and MoS 2 .