Nonvolatile nanotube switches with reduced switching voltages and currents
A non-volatile nanotube switch and memory arrays constructed from these switches are disclosed. A non-volatile nanotube switch includes a conductive terminal and a nanoscopic element stack having a plurality of nanoscopic elements arranged in direct electrical contact, a first comprising a nanotube fabric and a second comprising a carbon material, a portion of the nanoscopic element stack in electrical contact with the conductive terminal. Control circuitry is provided in electrical communication with and for applying electrical stimulus to the conductive terminal and to at least a portion of the nanoscopic element stack. At least one of the nanoscopic elements is capable of switching among a plurality of electronic states in response to a corresponding electrical stimuli applied by the control circuitry to the conductive terminal and the portion of the nanoscopic element stack. For each electronic state, the nanoscopic element stack provides an electrical pathway of corresponding resistance.
1. A non-volatile nanotube switch comprising:
a bottom conductive terminal;
an interface layer disposed over said bottom conductive terminal;
a carbon layer disposed over said interface layer;
a top conductive terminal disposed over said carbon layer; and
control circuitry in electrical communication with said top conductive terminal and said bottom conductive terminal;
wherein said control circuitry is capable of providing electrical stimulus to said carbon layer through said top conductive terminal and said bottom conductive terminal; and
wherein said interface layer provides a pre-selected contact resistance between said bottom conductive terminal and said carbon layer.
2. The non-volatile nanotube switch of claim 1 wherein said carbon layer is a carbon nanotube fabric.
3. The non-volatile nanotube switch of claim 2 wherein said carbon nanotube fabric is comprised of single walled nanotubes.
4. The non-volatile nanotube switch of claim 2 wherein said carbon nanotube fabric is comprised of multi-walled nanotubes.
5. The non-volatile nanotube switch of claim 2 wherein said carbon nanotube fabric is comprised of a selected combination of single walled nanotubes and multi-walled nanotubes.
6. The non-volatile nanotube switch of claim 1 wherein said carbon layer is a composite nanotube article comprising a substantially homogenous mixture of nanotubes and nanoscopic particles.
7. The non-volatile nanotube switch of claim 6 wherein said nanoscopic particles include at least one allotrope of carbon.
8. The non-volatile nanotube switch of claim 6 wherein said nanoscopic particles include at least one of silicon oxide, silicon nitride, and mixtures thereof.
9. The non-volatile nanotube switch of claim 1 wherein said interface layer is a comprised of at least one of carbon nanotubes, amorphous carbon, graphite, graphene, Buckminster-fullerenes, carbon nanotubes, or diamond.
10. The non-volatile nanotube switch of claim 1 wherein said interface layer is a comprised of a non-carbon material.
11. The non-volatile nanotube switch of claim 10 wherein said non-carbon material is one of Si, Ge, Cu, W, and Ti.
12. The non-volatile nanotube switch of claim 1 wherein said interface layer is comprised of a silicon based material.
13. The non-volatile nanotube switch of claim 1 wherein said interface layer is an ion implanted nanotube fabric.
14. The non-volatile nanotube switch of claim 13 wherein said ion implanted nanotube fabric includes atoms of Si, Ge, Cu, W, or Ti.
15. The non-volatile nanotube switch of claim 1 wherein said carbon layer is switchable among a plurality of electronic states in response to said electrical stimulus, said electronic states corresponding to the resistance of the carbon layer.
16. The non-volatile nanotube switch of claim 15 wherein said electrical stimulus comprises a voltage of less than approximately 5 volts.
17. The non-volatile nanotube switch of claim 15 wherein said electrical stimulus comprises a SET current of approximately 1-3 μA and a RESET current of approximately 10-50 μA.
18. The non-volatile nanotube switch of claim 1 wherein said interface layer provides said non-volatile nanotube switch with an initial resistance less than 1 megaohm.
19. The non-volatile nanotube switch of claim 1 wherein said interface layer provides said non-volatile nanotube switch with an initial resistance greater than 100 megaohm.