Vertical carbon nanotube device in nanoporous templates
A modified porous anodic alumina template (PAA) containing a thin CNT catalyst layer directly embedded into the pore walls. CNT synthesis using the template selectively catalyzes SWNTs and DWNTs from the embedded catalyst layer to the top PAA surface, creating a vertical CNT channel within the pores. Subsequent processing allows for easy contact metallization and adaptable functionalization of the CNTs and template for a myriad of applications.
1. A method comprising:
providing a substrate;
placing a first layer including a first material on the substrate
stacking a layer of catalyst for synthesis of carbon nanostructures atop the first layer;
stacking a second layer including said first material atop the layer of catalyst; and then
creating a plurality of nanopores in the first layer, catalyst, and second layer;
wherein each of the nanopores serially traverses the layer of catalyst and the second layer; and then
synthesizing with the catalyst a carbon nanostructure in each of the nanopores.
2. The method of claim 1 wherein said first material includes aluminum.
3. The method of claim 2 wherein said creating a plurality of nanopores is by anodizing the aluminum.
4. The method of claim 1 wherein said synthesizing is by depositing carbon from a vapor phase.
5. The method of claim 4 wherein said synthesizing is in the presence of a plasma.
6. The method of claim 1 wherein said synthesizing is by chemical vapor deposition enhanced with plasma generated by microwave energy.
7. The method of claim 1 wherein the catalyst is in a substantially uniform layer.
8. The method of claim 7 wherein the catalyst is one of Fe, Co, Ni, and Pd.
9. The method of claim 1 wherein the substrate is electrically conductive.
10. The method of claim 9 wherein the substrate is Ti.
11. The method of claim 1 wherein the carbon nanostructure is a carbon nanotube having no more than two walls.
12. The method of claim 1 wherein the nanopores are oriented vertically.
13. The method of claim 1 wherein said creating a plurality of nanopores is after said placing a first layer, said stacking a catalyst, and said stacking a second layer;
wherein said creating serially transverses the first layer; and
wherein the carbon nanostructure grows from a position intermediate along the length of the corresponding nanopore.
14. The method of claim 1 which further comprises electrically biasing with a DC voltage the substrate relative to the walls of a chamber, wherein said synthesizing is in the chamber during said biasing.
15. The method of claim 1 wherein said stacking a catalyst is stacking a first layer of a catalytic material, and which further comprises stacking a second layer of a catalytic material atop the second layer, and said creating includes the second layer of catalytic material.
16. The method of claim 1 which further comprises embedding the catalyst into at least one of the first layer or the second layer prior to said synthesizing.
17. The method of claim 1 wherein each pore has an inner diameter, each nanostructure has an outer diameter, and the outer diameter is less than half of the inner diameter.
18. The method of claim 1 wherein each pore has a sidewall, the catalyst is embedded in the sidewall, and the carbon nanostructure grows from the embedded catalyst.
19. The method of claim 18 wherein each pore has a top and a bottom, and each carbon nanostructure grows from a location intermediate of the top and the bottom.
20. The method of claim 1 wherein said stacking a first layer is before said stacking a catalyst, and said stacking a catalyst is before said stacking a second layer.
21. A method comprising:
providing a substrate;
placing a first layer including a first material on the substrate
stacking a layer of catalyst for synthesis of carbon nanostructures atop the first layer;
stacking a second layer including said first material atop the layer of catalyst;
diffusing the layer of catalyst into at least one of the first layer or the second layer; wherein each of a plurality of nanopores serially traverses the layer of catalyst and the second layer, and
synthesizing with the catalyst a carbon nanostructure after said diffusing.
22. The method of claim 21 wherein said diffusing is by annealing the substrate, first layer, catalyst, and second layer.
23. The method of claim 22 wherein said annealing is at a temperature above about 400 degrees C.
24. The method of claim 21 which further comprises creating said plurality of nanopores in said first material before said synthesizing.
25. The method of claim 24 wherein said creating said plurality of nanopores is before said diffusing.
26. The method of claim 21 wherein said first material includes aluminum and which further comprises anodizing the aluminum to create said plurality of nanopores, wherein said synthesizing is in the nanopores.
27. The method of claim 26 wherein said diffusing is before said anodizing.
28. The method of claim 27 wherein said diffusing is by annealing.
29. The method of claim 21 which further comprises electrically biasing with a DC voltage the substrate relative to the walls of a chamber, wherein said synthesizing is in the chamber during said biasing.
30. The method of claim 21 wherein said stacking a catalyst is placing a first catalytic material, and which further comprises stacking a second catalytic material atop the second layer.
31. The method of claim 30 which further comprises diffusing the second catalytic material into the second layer including said material.
32. The method of claim 21 wherein each pore has an inner diameter, the nanostructures are carbon nanotubes having an outer diameter, and the outer diameter is less than half of the inner diameter.
33. The method of claim 21 wherein each pore has a top and a bottom, and each carbon nanostructure grows from a location intermediate of the top and the bottom.
34. The method of claim 21 wherein said stacking a first layer is before said stacking a catalyst, said stacking a catalyst is before said stacking a second layer, and the carbon nanostructures are single-walled carbon nanotubes.
35. The method of claim 21 wherein said synthesizing is by chemical vapor deposition enhanced with plasma.
36. The method of claim 21 wherein the substrate is electrically conductive.
37. The method of claim 21 wherein the substrate is Si.
38. A method comprising:
providing a substrate;
placing a first layer including a first material on the substrate;
stacking atop the first layer a catalyst for synthesis of carbon nanostructures;
stacking a second layer of said first material atop the catalyst;
creating a plurality of nanopores in the first layer, catalyst, and second layer;
placing the nanoporous substrate with the first material and the catalyst in a chamber having a second organic material in the vapor phase and a plasma;
electrically biasing the substrate relative to the walls of the chamber after said placing; and
synthesizing with the catalyst a carbon nanostructure in each of the nanopores during said biasing.
39. The method of claim 38 wherein during said synthesizing the biasing is electrically positive.
40. The method of claim 38 wherein during said synthesizing the biasing is electrically negative with a difference of more than 150 volts.
41. The method of claim 38 wherein said creating a plurality of nanopores is a plurality of vertical nanopores.
42. The method of claim 38 wherein said first material includes aluminum and said creating a plurality of nanopores is by anodizing.