Towards simple methods for mass production of suspended graphene

This paper reports simple fabrication approaches that can be used to generate a suspended graphene sheet with the desired thickness, while eliminating the need for a crytical point dryer. Two methods have been developed to achieve a large suspended area of graphenes. In the first approach, SF₆ plasma was used to make holes or channels with specific dimensions. Then micromechanical exfoliation was applied to deposit the graphene sheet suspended over these channels or holes. In the second method, we used SF₆ plasma to make suspended graphenes by undercutting planar graphenes. To tune the number of graphene layers, thick graphene samples was etched layer by layer until the desired thickness was obtained. Additionally, the effect of using various plasmas etching (SF₆ or O₂) on the layer-by-layer graphene removal has been studied. Raman spectra of plasma-treated graphenes have shown higher amount of defects in case of SF₆, specially for thin graphene sheet. However, these surface defects could be recovered by annealing the samples in an argon environment at about 1000 °C.