Simulations of the response of supported 2D materials to ion irradiation with explicit account for the atomic structure of the substrate

Abstract

Ion irradiation has routinely been used to create defects or even pattern two-dimensional (2D) materials. For efficient defect engineering, that is, choosing the proper ion fluence to achieve the desired concentration of defects, it is of paramount importance to know the probability of creating defects as a function of ion energy. Atomistic simulations of ion impacts on 2D targets can provide such information, especially for free-standing systems, but in the case of supported 2D materials, the substrate can strongly affect defect production. Here, we employ analytical potential molecular dynamics simulations to calculate the average number of defects produced by light (He) and heavy (Ar) ions in 2D MoS₂ and graphene, two archetypal 2D materials, both free-standing and supported, in a wide range of ion energies. We take explicit account of the atomic structure of the SiO₂ and Au substrates and use several approaches to choose impact points in the supercell to increase the accuracy of the calculations. We show that depending on ion type and energy, the substrate can increase or decrease defect production, and the concentration of irradiation-induced defects and sputtering yield can be quite different for different substrate types. Our simulations provide microscopic insights into different channels of defect production in free-standing and supported 2D systems, and give quantitative results on sputtering yield and defect concentration, which can directly be compared to experimental data.