Graphene field-effect transistor fabrication: commercially available monolayer graphene ("Easy Transfer", Graphenea Inc.) grown by chemical vapor deposition was transferred on to a highly p-doped silicon substrate with chlorinated 285 nm dry thermal SiO2 following a wet chemical transfer process. The graphene channel was defined by electron beam lithography, electron beam assisted thermal deposition of 70 nm thick Cu protective layer, and subsequent oxygen plasma etching for 150 seconds (200 W, 1 mbar O2). While the graphene is etched beside the Cu, it remains intact underneath the Cu. In a next step the Cu was etched with a water-based ammoniumpersulfate solution (1.6 mgmL -1 ) for 5 minutes, and the electron beam lithography was repeated followed by an electron beam assisted thermal deposition of 2 nm Cr and 40 nm Au to form the electrodes.