Vapor-trapping growth of single-crystalline graphene flowers
A method for growing a graphene layer on a metal foil includes placing a vessel into a chemical vapor deposition chamber, the vessel having a metal foil positioned therein. The method includes evacuating the chemical vapor deposition chamber, introducing hydrogen gas into the chamber to achieve a first pressure less than atmospheric pressure, heating the atmosphere in the chamber to anneal the metal foil, introducing methane and hydrogen into the chamber to achieve a second pressure less than atmospheric pressure.
1. A method comprising:
placing a vessel comprising a quartz tube having an open end into a chemical vapor deposition chamber, wherein metal foil is positioned into the vessel, and wherein the open end of the vessel is directly facing and closer to a first opening of the chemical vapor deposition chamber than a closed end of the vessel is to the first opening;
evacuating the chemical vapor deposition chamber;
flowing hydrogen gas through the chamber from the first opening of the chamber to a second opening of the chamber to achieve a first pressure less than atmospheric pressure;
heating the atmosphere in the chamber to anneal the metal foil;
flowing methane and hydrogen through the chamber from the first opening of the chamber to the second opening of the chamber to achieve a second pressure less than atmospheric pressure; and
depositing carbon on the metal foil to yield a single-crystalline graphene layer on the metal foil.
2. The method of claim 1 , wherein the methane and hydrogen introduced into the chamber do not flow through the vessel.
3. The method of claim 2 , wherein the methane and hydrogen introduced into the chamber diffuse into the vessel.
4. The method of claim 1 , wherein a local environment between the metal foil and an interior of the vessel is different from an environment inside the chamber, and wherein the metal foil is a copper foil.
5. The method of claim 4 , wherein the vessel reduces a supply of carbon to the metal foil and creates a quasi-static reactant gas distribution.
6. The method of claim 1 , wherein the graphene layer is in a shape of a four-lobed flower, a six-lobed flower, or a combination thereof.
7. The method of claim 1 , wherein a dimension of the graphene layer on the metal foil is less than or about 100 μm.
8. The method of claim 6 , wherein lobes of the four-lobed flower, the six-lobed flower, or the combination thereof are a single-layer graphene.
9. The method of claim 6 , wherein a center of the four-lobed flower, the six-lobed flower, or the combination thereof is a bilayer graphene.
10. The method of claim 1 , further comprising adjusting a total pressure, a methane to hydrogen flow rate ratio, or both to obtain a desired morphology.
11. The method of claim 1 , wherein a ratio of a flow rate of the methane to a flow rate of the hydrogen is between 1:10 to 1:20.
12. The method of claim 1 , wherein a total pressure of the methane and hydrogen is less than 200 mTorr.
13. The method of claim 1 , further comprising removing the graphene layer from the metal foil.
14. The method of claim 1 , wherein the graphene layer produces one set of symmetric six-fold electron diffraction patterns oriented in a same direction.
15. A method of forming a field effect transistor, the method comprising:
providing a silicon substrate;
providing a thermal oxide layer on the silicon substrate;
transferring the graphene layer formed by the method of claim 1 from the metal foil onto the thermal oxide layer to form a graphene channel;
depositing a source electrode at one end of the graphene channel; and
depositing a drain electrode at another end of the graphene channel.