Method for producing SiC substrate provided with graphene precursor and method for surface treating SiC substrate
A method includes a graphene precursor formation process of: heating a SiC substrate to sublimate Si atoms in a Si surface of the SiC substrate so that a graphene precursor is formed; and stopping the heating before the graphene precursor is covered with graphene. A SiC substrate to be treated in the graphene precursor formation process is provided with a step including a plurality of molecular layers. The step has a stepped structure in which a molecular layer whose C atom has two dangling bonds is disposed closer to the surface than a molecular layer whose C atom has one dangling bond.
1. A method for producing a graphene precursor on a substrate made of 4H—SiC, the method comprising:
providing the substrate made of 4H—SiC, the substrate made of 4H—SiC having steps comprising a first step, a second step and a third step, each of the steps having an upper surface with a terrace width, a step height from the first step to the second step being the same as the step height from the second step to the third step, the terrace width of the first step, the second step and the third step being the same, each of the steps comprising:
a first molecular layer having the upper surface, the first molecular layer having a first stepped structure whose C atom has two dangling bonds;
a second molecular layer below the first molecular layer, the second molecular layer having a second stepped structure whose C atom has two dangling bonds;
a third molecular layer below the second molecular layer, the third molecular layer having a third stepped structure whose C atom has one dangling bond; and
a fourth molecular layer below the third molecular layer, the fourth molecular layer having a fourth stepped structure whose C atom has one dangling bond,
heating the substrate made of 4H—SiC to sublimate Si atoms from the first molecular layer in each of the steps to form the graphene precursor on the first molecular layer in each of the steps; and
stopping the heating before the graphene precursor on the first molecular layer in each of the steps becomes graphene, thereby producing the graphene precursor on the 4H—SiC substrate.
2. The method for producing a graphene precursor on a substrate made of 4H—SiC according to claim 1 , wherein
the substrate made of 4H—SiC is provided with an off-angle relative to <1-100> direction.
3. The method for producing a graphene precursor on a substrate made of 4H—SiC according to claim 1 , further comprising
an etching process performed prior to sublimating the Si atoms by heating the substrate made of 4H—SiC under a Si vapor pressure.
4. The method for producing a graphene precursor on a substrate made of 4H—SiC according to claim 3 , wherein
the etching process is performed under a predetermined treatment condition including at least a heating temperature and an etching rate.
5. The method for producing a graphene precursor on a substrate made of 4H—SiC according to claim 3 , wherein
the etching process is performed by adjusting at least an etching rate of 1 um/min or more and a heating temperature of 1400° C. to 2000° C.
6. The method for producing a graphene precursor on a substrate made of 4H—SiC according to claim 5 , wherein the etching process is performed to provide the substrate made of 4H—SiC in which each of the steps is formed of the first molecular layer, the second molecular layer, the third molecular layer and the fourth molecular layer.
7. The method for producing a graphene precursor on a substrate made of 4H—SiC according to claim 1 , wherein
the substrate made of 4H—SiC is heated to sublimate the Si atoms at 1400° C. or more and 2000° C. or less.
8. The method for producing a graphene precursor on a substrate made of 4H—SiC according to claim 1 , wherein
the substrate made of 4H—SiC is heated to sublimate the Si atoms at 1550° C. or more and 1650° C. or less.
9. The method for producing a graphene precursor on a substrate made of 4H—SiC according to claim 1 , wherein
the substrate made of 4H—SiC is heated to sublimate the Si atoms in a treatment container having at least its inner surface made of pyrolytic carbon.
10. The method for producing a graphene precursor on a substrate made of 4H—SiC according to claim 1 , wherein the graphene precursor has a six-membered ring structure when viewed in a thickness direction, the graphene precursor consisting of C atoms in which one out of every three C atoms of the graphene precursor is connected to a Si atom of the second molecular layer, wherein a thickness of the graphene precursor in the thickness direction is equal to a thickness of one C atom.
11. The method for producing a graphene precursor on a substrate made of 4H—SiC according to claim 1 , wherein the substrate made of 4H—SiC is heated to sublimate the Si atoms from the first molecular layer in each of the steps at a temperature of 1550 to 2200° C. to form the graphene precursor on the first molecular layer in each of the steps.