Graphene doping by thermal poling
A method of forming a graphene device includes: providing a glass substrate with a blocking layer disposed thereon to form a stack; providing a first electrode and a second electrode; increasing the temperature of the stack to at least 100° C.; applying an external electric field (V P ) to the first electrode such that at least one metal ion of the glass substrate migrates toward the first electrode to create a depletion region in the glass substrate adjacent the second electrode; decreasing the temperature of the stack to room temperature while applying the external electric field to the first electrode; and after reaching room temperature, setting the external electric field to zero to create a frozen voltage region adjacent the second electrode.
1. A method of forming a graphene device, comprising:
providing a glass substrate with at least one blocking layer disposed thereon to form a stack, wherein the glass substrate comprises metal ions;
providing a first electrode disposed to partially cover the blocking layer;
transferring a graphene layer on the first electrode;
providing a second electrode disposed to partially cover the blocking layer without overlapping with the first electrode and the graphene layer;
increasing the temperature of the stack to at least 100° C.;
applying an external electric potential (V P2 ) to the first electrode such that said metal ions of the glass substrate migrate toward the first electrode to create a depletion region in the glass substrate adjacent the second electrode at a potential (V P1 );
decreasing the temperature of the stack to room temperature while applying the external electric potential; and
after reaching room temperature, setting the external electric potential to zero to create a frozen voltage region in the glass substrate adjacent the second electrode.
2. The method of claim 1 , wherein the stack includes the blocking layer disposed between the glass substrate and at least one graphene layer.
3. The method of claim 2 , wherein the at least one graphene layer is an n-type graphene layer.
4. The method of claim 1 , wherein the first electrode is a cathode electrode, the second electrode is an anode electrode, and the external electric potential is negative.
5. The method of claim 1 , wherein the blocking layer is disposed adjacent to the first electrode or adjacent to the second electrode.
6. The method of claim 1 , wherein the blocking layer is disposed adjacent to the first electrode and adjacent to the second electrode.
7. The method of claim 1 , wherein:
the at least one metal ion comprises at least one of sodium ions, calcium ions, lead ions, lithium ions, potassium ions, boron ions, zirconium ions, titanium ions, magnesium ions, aluminum ions, or barium ions, and
the step of applying the external electric potential further comprises:
reacting the at least one metal ion at the first electrode to form a powder complex.
8. The method of claim 7 , wherein the powder complex comprises at least one of Na 2 O, Na 2 CO 3 , CaO, PbO, LizO, K 2 O, B 2 O 3 , ZrO 2 , TiO 2 , MgO, Al 2 O 3 , or BaO.
9. The method of claim 1 , wherein the blocking layer comprises at least one of a SiO 2 layer, a hydrophobic coating, a polyimide layer, a self-assembly polymer monolayer, an ion exchanged glass, or combinations thereof.
10. The method of claim 1 , wherein a thickness of the blocking layer is in a range of 1 nm to 100 nm.
11. The method of claim 1 , wherein a thickness of the depletion region is at least 4 μm.
12. The method of claim 1 , wherein the step of applying the external electric potential to the first electrode comprises:
increasing a thickness of the depletion region.
13. The method of claim 1 , wherein the external electric potential is in a range of 100 V to 10 kV.
14. The method of claim 1 , further comprising:
after the step of setting the external electric potential to zero, annealing the stack to eliminate the frozen voltage region.
15. The method of claim 1 , wherein the step of increasing the temperature comprises:
increasing the temperature of the stack to a range of 100° C. to 300° C.
16. The method of claim 1 , wherein the potential (V P1 ) is 0 V.
17. The method of claim 1 , wherein the method further comprises providing a dielectric layer disposed on the graphene layer.
18. The method of claim 1 , wherein the first electrode comprises a Hall bar geometry area.
19. The method of claim 18 , wherein the method further comprises removing graphene beyond the Hall bar geometry area by wet etching.
20. The method of claim 1 , wherein the blocking layer comprises Al 2 O 3 , SiO 2 , a hydrophobic coating, ion exchanged glass, or combinations thereof.