A facile method for the synthesis of transfer-free graphene from co-deposited nickel-carbon layers

We report a facile synthesis method for the preparation of transfer-free graphene on dielectric substrates from co-deposited nickel-carbon (Ni-C) films. To fabricate 75-nm-thick Ni-C layers on top of dielectric substrates, DC reactive magnetron sputtering was performed at a gas pressure of 2 mTorr by flowing a gas mixture of argon (Ar; flow rate: 5 sccm) and methane (CH4; flow rate: 1 sccm), while 200 W DC input power was applied to a Ni target. Then, the sample was annealed at 1000 °C for 4 min at a pressure of 1 Torr and Ar flow rate of 200 sccm. The Ni-C layer was removed by a 0.5 M FeCl3 aqueous solution, and graphene was directly obtained on the dielectric substrate without any additional transfer process. The graphene quality was significantly influenced by annealing conditions, CH4 flow rate during co-deposition, and Ni-C thin film thickness. Furthermore, temperature modulation was conducted to decrease the graphene sheet defect coverage down to 7.2%. Sheet resistance and transmittance (550 nm) of the transfer-free graphene obtained under optimal conditions were 1.9 kΩ sq−1 and 93.9%, respectively. This facile non-transfer process will facilitate future research on graphene as well as its industrial applications.