Methods for the growth of a graphene layer structure on a substrate and an opto-electronic device

A method for the growth of a graphene layer structure on a substrate, the method comprising:

• providing a substrate on a susceptor in a CVD reaction chamber, wherein the substrate has a first surface for contacting the susceptor and a second surface for the formation of a graphene layer structure;
• providing a carbon-containing precursor;
• heating the susceptor to achieve a temperature of the second surface sufficient to thermally decompose the precursor and below 940° C.;
• and
• introducing the carbon-containing precursor into the reaction chamber to provide a flow of the precursor across the second surface and to thereby form the graphene layer structure on the second surface;
• wherein the substrate is a laminate wafer comprising a silicon support providing the first surface and a germanium layer providing the second surface, wherein the germanium layer has a thickness of 10 nm to 2 μm;
• wherein the substrate further comprises a barrier layer between the silicon support and the germanium layer, wherein the barrier layer is an inorganic oxide, nitride or fluoride;
• wherein the barrier layer has a thickness of less than 50 nm;
• and
• wherein the CVD reactor is a cold-walled reactor and the heated susceptor is the only source of heat in the reaction chamber.