A method for the production of a graphene layer structure, the method comprising providing a substrate on a heated susceptor in a reaction chamber, the chamber having a plurality of cooled inlets arranged so that, in use, the inlets are distributed across the substrate and have a constant separation from the substrate, rotating the heated susceptor at a rotation rate of at least 300 rpm, supplying a flow comprising a precursor compound through the inlets and into the reaction chamber to thereby decompose the precursor compound and form graphene on the substrate, wherein the inlets are cooled to less than 100° C., preferably 50 to 60° C., and the susceptor is heated to a temperature of at least 50° C. in excess of a decomposition temperature of the precursor, wherein the constant separation is at least 12 cm and preferably from 12 to 20 cm.