NOVELTY - A method (M1) of forming a graphene layer involves mixing a carbon source with a horizontally oriented molten solvent; precipitating the carbon source from the molten solvent to form a graphite layer across the molten solvent; and separating the graphite layer into several graphene layers.    USE - For forming a graphene layer, a hexagonal boron nitride layer incorporated into a device selected from molecule sensors, light emitting diodes (LEDs), liquid crystal displays (LCDs), solar panels, pressure sensors, surface acoustic wave (SAW) filters, resonators, transistors, capacitors, transparent electrodes, UV lasers, and/or DNA chips; and silicon carbide layer (claimed).    ADVANTAGE - The defects are eliminated using a gasification process. Because defects and grain boundaries in graphene layers are unstable, carbon atoms located at terminal positions are prone to dissolve, while carbon atoms with the graphene network are relatively stable. The ability to manufacture graphene and hexagonal boron nitride has a predetermined size and shape. Because the material layers are formed across the surface of a molten solvent, the size and shape of the resulting graphene or hexagonal boron nitride layers can be determined by the size and shape of the horizontally oriented molten solvent.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following:    (1) a method (M2) of forming a hexagonal boron nitride layer involving mixing a boron nitride source with a horizontally oriented molten solvent, and precipitating the boron nitride source from the molten solvent to form a hexagonal boron nitride layer across the molten solvent;    (2) an electronic device comprising a graphene layer, and a hexagonal boron nitride layer, where the graphene layer and the hexagonal boron nitride layer are incorporated into an electronic device;    (3) a method (M3) of forming a silicon carbide layer involving mixing a silicon carbide source with a horizontally oriented molten solvent, and precipitating the silicon carbide source from the molten solvent to form a silicon carbide layer across the molten solvent;    (4) a method (M4) of forming a rhombohedral graphene layer involving mixing a diamond source with a horizontally oriented molten solvent, and precipitating the diamond source from the molten solvent to form a rhombohedral graphene layer across the molten solvent;    (5) an electrical precursor material comprising a composite material comprises a graphene layer, and a hexagonal boron nitride layer disposed on the graphene layer;    (6) a method (M5) of making a graphene/hexagonal boron nitride composite material involving providing a template having a graphene layer disposed on a substrate; depositing a boron nitride source material on the graphene layer to form a hexagonal boron nitride layer on it.