Composite metal films and carbon nanotube fabrication
Embodiments of the present invention provide methods for the fabrication of carbon nanotubes using composite metal films. A composite metal film is fabricated to provide uniform catalytic sites to facilitate the uniform growth of carbon nanotubes. Further embodiments provide embedded nanoparticles for carbon nanotube fabrication. Embodiments of the invention are capable of maintaining the integrity of the catalytic sites at temperatures used in carbon nanotube fabrication processes, 600 to 1100° C.
1. A method for fabricating carbon nanotubes comprising:
depositing a film comprising an active component and an inactive component wherein the active component is capable of catalyzing the formation of carbon nanotubes at a temperature of between about 300° C. to about 1200° C. in the presence of a carbon containing precursor and the inactive component is not capable of catalyzing the formation of carbon nanotubes at a temperature of between about 300° C. to about 1200° C. in the presence of a carbon containing precursor and wherein the amount of active component in the film is above the equilibrium solubility limit but below the alloy phase formation concentration for the active component in the inactive component at a temperature between about 300° C. to about 1200° C.;
heating the film to a temperature of between about 300° C. to about 1200° C. to cause the active component to form at least one phase-separated surface-available catalytic site; and
forming carbon nanotubes by chemical vapor deposition with a carbon-containing precursor.
2. The method for fabricating carbon nanotubes of claim 1 , wherein the at least one surface-separated active component has dimensions of less than about 10 Angstroms.
3. The method for fabricating carbon nanotubes of claim 1 , wherein active component is a metal selected from the group consisting of Co, W, Ni, Fe, Pd, and Pt.
4. The method for fabricating carbon nanotubes of claim 1 , wherein inactive component is selected from the group consisting of SiO 2 , SiN, polymeric films, dielectric materials, Al, Cu, and Ti.
5. The method for fabricating carbon nanotubes of claim 1 , wherein the film is deposited by sputtering, atomic layer deposition plating, or electrolysis, pulsed laser deposition, physical vapor deposition, spin-on, evaporation, or chemical vapor deposition.
6. The method for fabricating carbon nanotubes of claim 1 , wherein the deposited film is a non-equilibrium film.
7. The method for fabricating carbon nanotubes of claim 1 , also including the electroless plating of a catalytic metal onto the phase-segregated active component prior to the formation of carbon nanotubes.
8. A method for fabricating carbon nanotubes comprising:
depositing a film comprising an active component and an inactive component wherein the active component is capable of catalyzing the formation of carbon nanotubes at a temperature of between about 300° C. to about 1200° C. in the presence of a carbon containing precursor and the inactive component is not capable of catalyzing the formation of carbon nanotubes at a temperature of between about 300° C. to about 1200° C. in the presence of a carbon containing precursor and wherein the amount of active component in the film is above the equilibrium solubility limit but below the alloy phase formation concentration for the active component in the inactive component at a temperature between about 300° C. to about 1200° C.;
heating the film to a temperature of between about 300° C. to about 1200° C. to cause the active component to form at least one phase-separated surface-available nanoparticle;
depositing a catalytic metal by atomic layer deposition;
depositing a continuous layer of a highly reducible oxide;
reducing the continuous layer of the highly reducible oxide to expose at least the first atomic layer of the metal catalyst; and
forming carbon nanotubes by chemical vapor deposition with a carbon-containing precursor.
9. The method for fabricating carbon nanotubes of claim 8 , wherein active component is a metal selected from the group consisting of Co, W, Ni, Fe, Pd, and Pt.
10. The method for fabricating carbon nanotubes of claim 8 , wherein the inactive component is an oxide selected from the group consisting of SiO 2 , TiO 2 , SnO 2 , and RuO 2 .
11. The method for fabricating carbon nanotubes of claim 8 , wherein the deposited film is a non-equilibrium film.
12. The method for fabricating carbon nanotubes of claim 8 , wherein the highly reducible oxide is TiO 2 or SnO 2 .
13. The method for fabricating carbon nanotubes of claim 8 , wherein the active component forms a plurality of surface-available nanoparticles.
14. The method for fabricating carbon nanotubes of claim 8 , wherein the atomic layer deposition deposits less than 1 ML of metal.
15. The method for fabricating carbon nanotubes of claim 8 , wherein the catalytic metal is selected from the group consisting Pd, Co, Ni, and Fe.