Jason D. Jones

On the mechanism for plasma hydrogenation of graphene

We report that hydrogenation of mono-, bi-, and trilayer graphene samples via exposure to H2 plasma occurs as a result of electron irradiation of H2O adsorbates on the samples, rather than H species in the plasma as reported by [Elias et al., Science 323, 610 (2009)]. We propose that the hydrogenation mechanism is electron-impact fragmentation of H2O adsorbates into H+ ions. At incident electron energies >60 eV, we observe hydrogenation that is significantly more stable at temperatures >200 °C than previously reported.

The Removal of Single Layers from Multi‐layer Graphene by Low‐Energy Electron Stimulation

The removal of single atomic layers from multi-layer graphene using a He plasma is reported. By applying sample biases of -60 and +60 V during He plasma exposure, layer removal is found to be due to electrons instead of He ions or neutrals in the plasma. The rate of layer removal depends on exposure time, sample bias, and pre-annealing treatments. Optical contrast microscopy and atomic force microscopy studies show that the removal of C atoms occurs approximately one layer at a time across the entire multi-layer sample with no observable production of large pits or reduction in lateral dimensions. Layer removal is proposed to arise from the electron-stimulated dissociation of C atoms from the basal plane. This process differs from plasma techniques that use reactive species to etch multi-layer graphene.