All-Optical High-Resolution Nanopatterning and 3D Suspending of Graphene

We introduce a laser-based technique capable of both imaging and patterning graphene with high spatial resolution. Both tasks are performed in situ using the same confocal microscope. Imaging graphene is based on the recombination of a laser-created electron-hole plasma yielding to a broadband up- and down-converted fluorescence. Patterning is due to burning graphene by local heating causing oxidation and conversion into CO(2). By shaping the laser beam profile using 1D phase-shifting plates and 2D vortex plates we can produce graphene dots below 100 nm in diameter and graphene nanoribbons down to 20 nm in width. Additionally, we demonstrate that this technique can also be applied to freely suspended graphene resulting in freely suspended graphene nanoribbons. We further present a way of freely hanging graphene vertically and imaging it in 3D. Taking advantage of having vertically hanging graphene for the first time, we measure the out-of-plane anisotropy of the upconversion fluorescence.