Figure 8.

Folding of graphene and other 2D materials by SHI irradiation. (a) The sketch visualizes the backfolded graphene after an ion has impinged onto the surface under a grazing angle of incidence $\Theta$. © IOP Publishing. Reproduced with permission from Ref. [112]. All rights reserved. Irradiation induced foldings as imaged by AFM in (a1) single and bilayer graphene, (a2) hBN, and (a3) MoS${}_2$, from Ref. [113]. (b) The shape of the graphene folding pattern (outlines shown in (b) are taken from AFM images) depends strongly on the angle of incidence. At larger angles the pattern consist of multiple foldings oriented along low-indexed crystallographic directions of the graphene [114] as shown in the inset in (b), while under very grazing incidence the azimuthal angle determines the direction of the two foldings, which are aligned along the ion trajectory, see Ref. [112]. (c,d): The substrate also influences shape and size of the foldings. AFM images of suspended graphene show slits (c1), which in fact are small foldings as can be seen in atomically resolved TEM images (c2); (d1) SiC-substrate, (d2) SiO${}_2$-substrate, (d3) Poly(methyl methacrylate)-substrate. Scale bars are 400 nm. © IOP Publishing. Reproduced with permission from Ref. [112]. All rights reserved.