Synthesis of large-scale undoped and nitrogen-doped amorphous graphene on MgO substrate by chemical vapor deposition

Despite amorphous graphene (a-graphene) domains having been created and observed within crystalline graphene, large-area synthesis is still in its infancy. Here, using MgO single crystals as a catalytic substrate, large-area (10 x 5 mm) undoped and nitrogen-doped a-graphene were synthesized by chemical vapor deposition with benzene and pyridine as precursors, respectively. The dependence of the number of layers and the crystallinity of a-graphene on the growth temperature was observed by transmission electron microscopy, selected area electron diffraction and Raman spectroscopy. Few-layer (2-5 layers) a-graphene films are demonstrated to have high transmittance (>85% at 550 nm) and low conductivity (< 1 x 10(-3) S cm(-1)). When doped with nitrogen (N/C ratio = similar to 0.09), the conductivity of the a-graphene film could be increased. The preparation of large-area a-graphene films not only extends to two-dimensional carbon materials but also might provide building blocks for future all-carbon devices.