Large single-crystal monolayer graphene by decomposition of methanol

We present a novel method for the synthesis of monolayer graphene with large single-crystal domains extending over 10–30 μm², produced by the decomposition of methanol on Cu in a single process step, in a flow of pure Ar gas, without H₂. Eliminating H₂ as a process gas offers increased safety and greatly facilitates fabrication scaling. The graphene grain size and orientation were characterized by selected area electron diffraction in transmission electron microscopy. Based on analyses of effluents from the furnace during the synthesis, a possible mechanism for graphene formation from methanol, involving carbon monoxide as an intermediate, is proposed.