Continuous single crystal growth of graphene
Systems and methods for synthesizing continuous single crystal graphene are provided. A catalytic substrate is drawn through a chemical vapor deposition chamber in a first lengthwise direction while flowing a hydrogen gas through the chemical vapor deposition chamber in the same lengthwise direction. A hydrocarbon precursor gas is supplied directly above a surface of the catalytic substrate. A high concentration gradient of the hydrocarbon precursor at the crystal growth front is generated to promote the growth of a continuous single crystal graphene film while suppressing the growth of seed domains ahead of the crystal growth front.
1. A method of synthesizing graphene comprising:
heating the interior of a chemical vapor deposition chamber to a temperature above 800° C.;
drawing a catalytic substrate through the interior of the chemical vapor deposition chamber in a first lengthwise direction;
introducing hydrogen gas into the interior of the chemical vapor deposition chamber in the same first lengthwise direction such that the hydrogen gas includes a flow rate of at least 15 cm/s in the first lengthwise direction, the hydrogen gas being mixed with an inert gas; and
flowing a hydrocarbon gas through a reactive supply conduit and introducing the hydrocarbon gas into the interior of the chemical deposition chamber downwardly at an angle relative to the first lengthwise direction through an opening in the reactive supply conduit, the opening being immediately above a major surface of the catalytic substrate at a crystal growth front,
wherein the hydrocarbon gas and the hydrogen gas form a precursor gas mixture, and wherein the catalytic substrate reacts with the precursor gas mixture to form continuous single crystal graphene on the catalytic substrate while being drawn in the same direction as the flow of the hydrogen gas.
2. The method of claim 1 wherein the opening is disposed between 1 mm to 10 mm above the catalytic substrate.
3. The method of claim 1 wherein the catalytic substrate comprises a polycrystalline substrate.
4. The method of claim 1 wherein at least one of a flux of the hydrocarbon gas through the opening and a flow rate of the hydrogen gas through the chemical vapor deposition chamber is selected to produce a concentration gradient of the hydrocarbon gas at the crystal growth front of the continuous single crystal graphene.
5. The method of claim 1 , further comprising delaminating the continuous single crystal graphene from the catalytic substrate without a supporting polymer layer.
6. The method of claim 1 wherein the hydrogen gas comprises from 1.5 to 3% of hydrogen in a noble gas.
7. The method of claim 1 wherein the hydrocarbon gas comprises 0.35% or less of a hydrocarbon precursor in a noble gas.
8. The method of claim 1 , further comprising maintaining a flux at the opening at 30 sccm or less.
9. The method of claim 1 wherein the drawing rate of the catalytic substrate is between 1 cm/hr to 2.5 cm/hr.
10. The method of claim 1 , further comprising:
initiating growth of the continuous single crystal graphene on a support adjacent an edge of the catalytic substrate; and
continuing to draw the catalytic substrate through the chemical vapor deposition chamber and past the opening to form the continuous single crystal graphene on the catalytic substrate.
11. The method of claim 1 wherein the hydrocarbon gas is selected from the group consisting of methane, ethane, propane, butane, pentane, hexane, heptane, octane, benzene, toluene, and combinations thereof.
12. The method of claim 1 wherein the first lengthwise direction is perpendicular to an armchair termination edge of the continuous single crystal graphene.