Millimeter-size Graphene Single Crystal And Device Research

A simply and reproducible way is proposed to significantly suppress the nucleation density of graphene on the copper foil during the chemical vapor deposition process. By inserting a copper foil into a tube with one close end, the nucleation density on the copper foils can be reduced by more than five orders of magnitude and an ultra-low nucleation density of ~10 nucleus/cm2 has been achieved. The structural analyses demonstrate that single crystal monolayer graphene with a lateral size of 1.9 mm can be grown on the copper foils under the optimized growth condition. The electrical transport studies show that the mobility of such single crystal graphene is around 2400 cm2/Vs.Deposition of molybdenum trioxide(MoO3) thin film by molecular beam epitaxy on graphene can significantly enhance the conductivity of graphene. In situ field effect transistor characterizations show that a strong surface transfer p-type doping effect occurs once MoO3 is deposited onto graphene. It is worth noting that the mobities of both the hole and the electron of graphene are nearly retained when the graphene conductivity is enhanced significantly. The conductivity of single crystal graphene can be increased by about 7 times when the MoO3 film with a thickness of 10 nm is coated onto the graphene, which provide a feasible way for the applications of graphene in electronic devices, transparent electrode and flexible electrode.