Nanostructuring graphene by dense electronic excitation

Abstract

The ability to manufacture tailored graphene nanostructures is a key factor to fully exploit its enormous technological potential. We have investigated nanostructures created in graphene by swift heavy ion induced folding. For our experiments, single layers of graphene exfoliated on various substrates and freestanding graphene have been irradiated and analyzed by atomic force and high resolution transmission electron microscopy as well as Raman spectroscopy. We show that the dense electronic excitation in the wake of the traversing ion yields characteristic nanostructures each of which may be fabricated by choosing the proper irradiation conditions. These nanostructures include unique morphologies such as closed bilayer edges with a given chirality or nanopores within supported as well as freestanding graphene. The length and orientation of the nanopore, and thus of the associated closed bilayer edge, may be simply controlled by the direction of the incoming ion beam. In freestanding graphene, swift heavy ion irradiation induces extremely small openings, offering the possibility to perforate graphene membranes in a controlled way.

Creating nanoporous graphene with swift heavy ions

“…Only a few experimental studies have addressed the effect of SHI irradiation in graphene [26,27,28,29,30,31,32,33]. Most of these experiments were performed on supported graphene and under oblique incidence.…”

Highly active single-layer MoS2 catalysts synthesized by swift heavy ion irradiation

“…This can be achieved by either highly charged or by very fast (swift) heavy ions. For both it has been shown that they can be used for defect engineering of 2D materials such as carbon nano-membranes, 26,27 graphene, [28][29][30][31][32][33] hexagonal boron nitride, 34 and MoS 2 . [35][36][37] Swift heavy ions (SHI) excite target atoms along their trajectory and the corresponding energy deposited per track length into the target material is usually given in terms of electronic stopping power S e = dE/dx.…”

On the threshold for ion track formation in CaF2

“…Due to the existence of the velocity effect, medium sized accelerators can provide important complementary data at energies below 1 MeV amu −1 which are not easily accessible to large accelerators. In particular, the threshold for ion track formation constitutes an important experimental quantity (often needed for testing various ion-solid interaction models) that can be in many cases easily accessible to medium sized accelerators [1,9,11,16,19,25,26]. Similar to ion tracks in the bulk, there is always a threshold for nanohillock formation on the surface.…”