Growth of Bilayer graphene on insulating substrates

Here we demonstrate a general transfer-free method to directly grow large areas of uniform bilayer graphene on insulating substrates (SiO₂, h-BN, Si₃N₄, and Al₂O₃) from solid carbon sources such as films of poly(2-phenylpropyl)methysiloxane, poly(methyl methacrylate), polystyrene, and poly(acrylonitrile-co-butadiene-co-styrene), the latter leading to N-doped bilayer graphene due to its inherent nitrogen content. Alternatively, the carbon feeds can be prepared from a self-assembled monolayer of butyltriethoxysilane atop a SiO₂ layer. The carbon feedstocks were deposited on the insulating substrates and then caped with a layer of nickel. At 1000 °C, under low pressure and a reducing atmosphere, the carbon source was transformed into a bilayer graphene film on the insulating substrates. The Ni layer was removed by dissolution, affording the bilayer graphene directly on the insulator with no traces of polymer left from a transfer step. The bilayer nature of as-grown samples was demonstrated by I _G/I_2D Raman mapping, the statistics of the full-width at half-maximum of the Raman 2D peak, the selected area electron diffraction patterns over a large area, and randomly imaged graphene edges by high-resolution transmission electron microscopy.