Carbon nanotube transistor process with transferred carbon nanotubes
During fabrication of single-walled carbon nanotube transistor devices, a porous template with numerous parallel pores is used to hold the single-walled carbon nanotubes. The porous template or porous structure may be anodized aluminum oxide or another material. A gate region may be provided one end or both ends of the porous structure. The gate electrode may be formed and extend into the porous structure.
1. A method of making a transistor device comprising:
providing a template having a top surface and a bottom surface, opposite of the top surface;
forming vertical openings in the substrate, wherein the openings extends from the top surface of the template, through the template, to the bottom surface of the template;
providing carbon nanotubes in the openings, wherein the carbon nanotubes extend from the top surface to the bottom surface of the template;
forming a first electrode region on the top surface of the template to electrically couple to first ends of the carbon nanotubes;
forming a second electrode region on the bottom surface of the template to electrically couple to second ends of the carbon nanotubes;
forming a first gate region in the template, wherein the first gate region has a first surface extending parallel to a portion of a first carbon nanotube between first and second ends of the first carbon nanotube; and
forming a second gate region in the template, wherein the second gate region has a second surface extending parallel to a portion of a second carbon nanotube between first and second ends of the second carbon nanotube, and the first carbon nanotube is positioned between the second carbon nanotube and the first gate region.
2. The method of claim 1 wherein there is no gate region between the first and second carbon nanotubes.
3. The method of claim 2 wherein the first and second gate regions are electrically coupled together to form a gate electrode of the transistor device.
4. The method of claim 1 wherein the first gate region extends from the top surface of the template into the template.
5. The method of claim 1 wherein the first surface region extends in the template from about 50 nanometers to about 1000 nanometers.
6. The method of claim 1 comprising:
forming a dielectric insulator between the first surface and the first carbon nanotube.
7. The method of claim 1 wherein the first gate region comprises polysilicon.
8. The method of claim 1 wherein the first gate region comprises a conductive material.
9. The method of claim 1 wherein the template comprises at least one of alumina, silicon, silicon germanium, gallium nitride, germanium, gallium arsenide, silicon oxide, plastic, polymer, glass, or quartz.
10. The method of claim 1 wherein the template is provided on a substrate.
11. The method of claim 10 wherein the substrate is at least one of silicon, silicon germanium, gallium nitride, germanium, gallium arsenide, silicon oxide, plastic, polymer, glass, quartz, metal, copper, molybdenum, aluminum, or tungsten.
12. The method of claim 1 wherein the template is provided on a substrate and the substrate is a different material than the template.
13. The method of claim 1 wherein the template is an insulator material and is provided on a substrate that is a conductor material.
14. The method of claim 1 wherein the providing carbon nanotubes in the openings comprises:
transferring only semiconducting carbon nanotubes into the openings.
15. The method of claim 1 wherein the carbon nanotubes provided to the openings are synthesized outside the openings of the template.
16. The method of claim 1 wherein the carbon nanotubes provided to the openings are synthesized by at least one of chemical vapor deposition, arc-discharge, or laser ablation.
17. The method of claim 1 wherein the providing carbon nanotubes in the openings comprises:
flowing a fluid comprising the carbon nanotubes through the openings.
18. The method of claim 1 wherein the providing carbon nanotubes in the openings comprises:
flowing a suspension comprising the carbon nanotubes through the openings.
19. The method of claim 1 wherein the carbon nanotubes provided comprise a mixture of semiconducting and metallic carbon nanotubes, and the method further comprises:
exposing the template with the mixture of semiconducting and metallic carbon nanotubes to a reagent, whereby the reagent renders greater numbers of the metallic carbon nanotubes ineffective for transistor operation than semiconducting carbon nanotubes.
20. The method of claim 19 wherein the reagent is an acid.
21. A method of making a transistor device comprising:
providing a template comprising a plurality of pores, each pore having a pore diameter;
transferring carbon nanotubes to the pores;
forming a first electrode region to electrically couple to first ends of the carbon nanotubes;
forming a second electrode region to electrically couple to second ends of the carbon nanotubes;
forming a first trench in the template;
forming a first gate region in the first trench, wherein the carbon nanotubes transferred comprise semiconducting and metallic carbon nanotubes; and
applying a voltage to the first gate region that results in a current flow through the carbon nanotubes, whereby the metallic carbon nanotubes are burned off in greater numbers than the semiconducting carbon nanotubes.
22. A method of making a transistor device comprising:
providing a template having a top surface and a bottom surface, opposite of the top surface;
forming vertical openings in the substrate, wherein the openings extends from the top surface of the template, through the template, to the bottom surface of the template;
providing carbon nanotubes in the openings, wherein the carbon nanotubes comprise a mixture of semiconducting and metallic carbon nanotubes that extend from the top surface to the bottom surface of the template;
forming a first electrode region on the top surface of the template to electrically couple to first ends of the carbon nanotubes;
forming a second electrode region on the bottom surface of the template to electrically couple to second ends of the carbon nanotubes;
forming a first gate region in the template, wherein the first gate region has a first surface extending parallel to a portion of a first carbon nanotube between first and second ends of the first carbon nanotube;
forming a second gate region in the template, wherein the second gate region has a second surface extending parallel to a portion of a second carbon nanotube between first and second ends of the second carbon nanotube, and the first carbon nanotube is positioned between the second carbon nanotube and the first gate region; and
applying a voltage to the first and second gate regions that results in a current flow through the carbon nanotubes between the first and second gate regions, whereby the metallic carbon nanotubes between the first and second gate regions are burned off in greater numbers than the semiconducting carbon nanotubes between the first and second gate regions.
23. The method of claim 21 wherein the current flow through a metallic carbon nanotube between the first and second gate regions is at least 15 microamps.
24. The method of claim 21 wherein the current flow through a metallic carbon nanotube between the first and second gate regions is from about 15 microamps to about 25 microamps.