The invention concerns a method of forming a graphene layer involving: heating a support layer in a reaction chamber; and forming the graphene layer on a surface of the support layer by: a) during a first time period, introducing into the reaction chamber an organic compound gas to cause a formation of carbon atoms on the surface; b) during a second time period after the first time period, reducing a rate of introduction of the organic compound gas into the reaction chamber and introducing into the reaction chamber a further gas, wherein the further gas is a carbon etching gas; and repeating a) and b) one or more times.