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.