METHOD FOR THE PRODUCTION OF A POLYMER COATED GRAPHENE LAYER STRUCTURE AND GRAPHENE LAYER STRUCTURE

Abstract

The present invention provides a method for the production of a polymer-coated graphene layer structure, the method comprising: providing a substrate on a heated susceptor in a reaction chamber, the chamber having a plurality of cooled inlets arranged so that, in use, the inlets are distributed across the substrate and have a constant separation from the substrate, supplying a flow comprising a precursor compound through the inlets and into the reaction chamber to thereby decompose the precursor compound and form a graphene layer structure on the substrate, wherein the inlets are cooled to less than 100° C. and the susceptor is heated to a temperature of at least 50° C. in excess of a decomposition temperature of the precursor, wherein the graphene layer structure has a first charge carrier density, spin-coating a composition having a second charge carrier density onto the graphene layer structure to form an air-impermeable coating, wherein the coated graphene layer structure has a third charge carrier density which is less than the first charge carrier density, wherein the composition comprises a polymer or polymer precursor.

Claims

1. A method for the production of a polymer-coated graphene layer structure, the method comprising: providing a substrate on a heated susceptor in a reaction chamber, the chamber having a plurality of cooled inlets arranged so that, in use, the inlets are distributed across the substrate and have a constant separation from the substrate, supplying a flow comprising a precursor compound through the inlets and into the reaction chamber to thereby decompose the precursor compound and form a graphene layer structure on the substrate, wherein the inlets are cooled to less than 100° C. and the susceptor is heated to a temperature of at least 50° C. in excess of a decomposition temperature of the precursor, wherein the graphene layer structure has a first charge carrier density, spin-coating a composition onto the graphene layer structure to form an air-impermeable coating, wherein the coated graphene layer structure has a second charge carrier density which is less than the first charge carrier density, wherein the composition comprises a polymer or polymer precursor.

2. The method according to claim 1, wherein the second charge carrier density is less than 5×10.sup.12 cm.sup.−2.

3. The method according to claim 1, wherein the graphene layer structure is not exposed to an oxygen-containing atmosphere before the air-impermeable coating has been formed.

4. The method according to claim 1 wherein the concentration of components in the composition is controlled by diluting the composition with deionised water before coating.

5. The method according to claim 1, wherein the air-impermeable coating has a thickness of from 1 nm to 10 μm.

6. The method according to claim 1, wherein the composition comprises a carboxylate-containing polymer.

7. The method according to claim 1, wherein the composition comprises a polymer precursor and wherein the method further comprises treating the spin-coated composition to form the air-impermeable coating.

8. The method according to claim 7, wherein the step of treating the spin-coated composition to form the air-impermeable coating comprises heating and/or UV-exposing the spin-coated composition.

9. The method according to claim 7, wherein the polymer precursor forms a carboxylate-containing polymer.

10. The method according to claim 1, wherein the graphene layer structure is removed from the substrate before the spin-coating step to provide a graphene layer structure having upper and lower exposed surfaces and wherein the spin-coating step involves coating both the upper and lower exposed surfaces to form the air-impermeable coating.

11. The method according to claim 1, wherein the coated graphene layer structure is removed from the substrate to provide a lower exposed surface and wherein the method further comprises spin-coating a carboxylate-containing polymer onto the lower exposed surface to form a second air-impermeable coating.

12. The method according to claim 1, wherein the substrate is an electronic device selected from a light-emitting or light-sensitive device.

13. The method according to claim 1, wherein the graphene layer structure is processed to form a Hall sensor before the step of spin-coating.

14. A graphene layer structure provided with an air-impermeable coating, and having a charge carrier density of less than 1×10.sup.12 cm.sup.−2.

15. A method for the production of a plurality of polymer-coated graphene layer structures, each having a target charge carrier density, the method comprising: (a) providing a graphene layer structure on a first substrate, the graphene layer structure having a first charge carrier density; (b) determining the first charge carrier density of the graphene layer structure; (c) spin-coating a composition onto the graphene layer structure to form an air-impermeable coating, wherein the components and their concentrations in the composition are selected so as to provide a polymer-coated graphene layer structure having a second charge carrier density, wherein the second charge carrier density is within 10% of the targeted charge carrier density; and (d) repeating steps (a) and (c) to provide a plurality of polymer-coated graphene layer structures on a plurality of corresponding substrates without determining the charge carrier density of each graphene layer structure.

16. The method according to claim 15, wherein in step (a), the graphene layer structure is provided by MOCVD.

17. The method according to claim 15, wherein the concentration of components in the composition is selected by dilution of the composition with a solvent before spin-coating.

18. A method for the production of a polymer-coated graphene layer structure having a charge carrier density of 1×10.sup.13 cm.sup.−2 to 8×10.sup.13 cm.sup.−2, the method comprising: (a) providing a graphene layer structure on a substrate, the graphene layer structure having a first charge carrier density; (b) determining the first charge carrier density of the graphene layer structure; (c) spin-coating a composition onto the graphene layer structure to form an air-impermeable coating, wherein the composition is selected to increase the first charge carrier density of the graphene layer structure and provide the polymer-coated graphene layer structure having a charge carrier density of 1×10.sup.13 cm.sup.−2 to 8×10.sup.13 cm.sup.−2.

Description

FIGURES

[0105] The present invention will now be described further with reference to the following non-limiting FIGURES, in which:

[0106] FIG. 1 shows a cross-section of the layers of a coated graphene structure as described herein.

[0107] FIG. 1 shows a cross-section of an exemplary graphene structure (101) comprising a graphene layer structure (103) and an air-impermeable coating (104) that is a polymer coating. The graphene layer structure (103) is provided on the surface of a substrate (102).

EXAMPLES

Example 1

[0108] PPEES is dissolved in NMP by heating a mixture at 50° C. on a hotplate for 7 hours followed by gentle agitation with a glass rod and then filtering so as to achieve a concentration of 3 wt %. To the composition is then added 2,3,5,6-tetrafluoro-7,7,8,8-tertacyanoquinodimethane (F.sub.4TCNQ) at concentrations of either 0.1 mg/mL or 1 mg/mL. The composition was then spun onto a graphene layer structure on a sapphire substrate at 1000 rpm (16.7 Hz) for 180 s followed by an annealing step at 130° C. for 5 minutes to dry the film.

[0109] Conductive Ag paint is used to contact the underlying graphene by heating at 200° C. for 30 minutes on a hotplate, thereby softening the PPEES and allowing the paint to dissolve through and form the silver contact on the graphene.

Example 2

[0110] Poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) is dissolved in anisole by heating a mixture at 50° C. on a hotplate for 7 hours followed by gentle agitation with a glass rod and then filtering so as to achieve a concentration of 3.4 wt %. To the composition is then added 2,3,5,6-tetrafluoro-7,7,8,8-tertacyanoquinodimethane (F.sub.4TCNQ) at concentrations of either 0.1 mg/mL or 1 mg/mL. The composition was spun onto a graphene layer structure on a sapphire substrate at 6000 rpm (100 Hz) for 60 s followed by annealing at 140° C. for 60 minutes to dry the film.

[0111] Next, a laser is used to ablate the polymer to expose the underlying graphene for the deposition of contacts. This is followed by electron beam deposition of Ti/Au electrode stacks on the exposed graphene.

[0112] All percentages herein are by weight unless otherwise stated or indicated by the context.

[0113] As used herein, the singular form of “a”, “an” and “the” include plural references unless the context clearly dictates otherwise. The use of the term “comprising” intended to be interpreted as including such features but not (necessarily) limited to is also intended to include the option of the features necessarily being limited to those described. In other words, the term also include the limitations of “consisting essentially of” (intended to mean that specific further components can be present provided they do not materially affect the essential characteristic of the described feature) and “consisting of” (intended to mean that no other feature may be included such that if the components were expressed as percentages by their proportions, these would add up to 100%, whilst accounting for any unavoidable impurities), unless the context clearly dictates otherwise.

[0114] The foregoing detailed description has been provided by way of explanation and illustration, and is not intended to limit the scope of the appended claims. Many variations in the presently preferred embodiments illustrated herein will be apparent to one of ordinary skill in the art, and remain within the scope of the appended claims and their equivalents.