Fabrication of high aspect ratio tall free standing posts using carbon-nanotube (CNT) templated microfabrication

1. An apparatus comprising:

a substrate; and

a micro-scale, free-standing post disposed on the substrate, the micro-scale, free-standng post having a height-to-diameter aspect ratio of greater than or equal to 25:1, the micro-scale, free-standing post including:

a plurality of nanotubes, the micro-scale, free-standing post extending substantially vertically from the substrate; and

an infiltration material that, over a height of the micro-scale, free-standing post, structurally links nanotubes of the plurality of nanotubes together.

2. The apparatus of claim 1 , wherein a diameter of the micro-scale, free-standing post is in a range of 5 micrometers (μm) to 100 μm.

3. The apparatus of claim 1 , wherein the micro-scale, free-standing post is substantially cylindrical.

4. The apparatus of claim 1 , wherein a height of the micro-scale, free-standing post is greater than or equal to 1 millimeter (mm).

5. The apparatus of claim 1 , wherein the plurality of nanotubes includes a plurality of carbon nanotubes (CNTs).

6. The apparatus of claim 1 , wherein the infiltration material includes carbon (C).

7. The apparatus of claim 1 , wherein the infiltration material includes at least one of silicon (Si) or silicon nitride (SiN).

8. The apparatus of claim 1 , wherein at least a portion of the plurality of nanotubes of the micro-scale, free-standing post are plated with a metal.

9. The apparatus of claim 1 , wherein the micro-scale, free-standing post is a first micro-scale, free-standing post, the apparatus further comprising a second micro-scale, free-standing post disposed on the substrate and laterally spaced from the first micro-scale, free-standing post, the second micro-scale, free-standing post including a plurality of nanotubes and extending substantially vertically from the substrate, the second micro-scale, free-standing post having a height-to-diameter aspect ratio of greater than or equal to 25:1.

10. The apparatus of claim 1 , wherein the substrate includes a silicon (Si) wafer having an aluminum oxide (Al 2 O 3 ) layer disposed thereon.

11. A method comprising:

providing a substrate;

forming a patterned catalyst layer on the substrate, the patterned catalyst layer defining a template for carbon nanotube growth, the template defining a pattern for formation of:

a first micro-scale carbon nanotube post;

a second micro-scale carbon nanotube post; and

a supporting structure disposed between the first micro-scale carbon nanotube post and the second micro-scale carbon nanotube post;

growing carbon nanotubes on the patterned catalyst layer to form the first micro-scale carbon nanotube post, the second micro-scale carbon nanotube post and the supporting structure, the first micro-scale carbon nanotube post and the second micro-scale carbon nanotube post each having a height-to-diameter aspect ratio of greater than or equal to 25:1, the supporting structure having height-to-width aspect ratio of greater than or equal to 200:1;

infiltrating, over a height of the first micro-scale carbon nanotube post and the second micro-scale carbon nanotube post, carbon nanotubes of the first micro-scale carbon nanotube post and carbon nanotubes the second micro-scale carbon nanotube post with an infiltration material, the infiltration material:

over the height of the first micro-scale carbon nanotube post, structurally linking carbon nanotubes of the first micro-scale carbon nanotube post together; and

over the height of the second micro-scale carbon nanotube post, structurally linking carbon nanotubes of the second micro-scale carbon nanotube post together; and

removing the supporting structure, such that each of the first micro-scale carbon nanotube post and the second micro-scale carbon nanotube post are free-standing and extend substantially vertically from the substrate.

12. The method of claim 11 , wherein, prior to removal of the supporting structure, a height of the first micro-scale carbon nanotube post, a height of the second micro-scale carbon nanotube post and a height of the supporting structure are substantially a same height.

13. The method of claim 12 , wherein the same height is greater than or equal to 1 millimeter (mm).

14. The method of claim 11 , wherein the infiltration material includes carbon (C).

15. The method of claim 11 , wherein the infiltration material includes at least one of silicon (Si) or silicon nitride (SiN).

16. The method of claim 11 , further comprising plating the first micro-scale carbon nanotube post and the second micro-scale carbon nanotube post with a metal.

17. The method of claim 11 , wherein removing the supporting structure includes:

performing a non-directional plasma etch to remove an upper portion of the supporting structure, such that a lower portion of the supporting structure remains, the lower portion of the supporting structure being disposed on the substrate;

infiltrating the first micro-scale carbon nanotube post, the second micro-scale carbon nanotube post and the lower portion of the supporting structure with carbon (C); and

performing a directional plasma etch to remove the lower portion of the supporting structure.

18. The method of claim 11 , wherein the substrate includes a silicon (Si) wafer having an aluminum oxide (Al 2 O 3 ) layer disposed thereon, the patterned catalyst layer being formed on the Al 2 O 3 layer.

19. The method of claim 18 , wherein forming the patterned catalyst layer includes forming, using photolithography, a patterned iron (Fe) layer, the Al 2 O 3 layer preventing diffusion of the patterned Fe layer into the Si wafer.

20. An apparatus comprising:

a substrate; and

an array of micro-scale, free-standing carbon nanotube posts disposed on the substrate, each micro-scale, free-standing carbon nanotube post of the array of micro-scale, free-standing carbon nanotube posts including a plurality of nanotubes and extending substantially vertically from the substrate, each micro-scale, free-standing carbon nanotube post of the array of micro-scale, free-standing carbon nanotube posts having a height-to-diameter aspect ratio of greater than or equal to 25:1, each of the micro-scale, free-standing carbon nanotube posts including an infiltration material that, over a height of a micro-scale, free-standing post of the array of micro-scale, free-standing carbon nanotube posts, structurally links nanotubes of a respective plurality of nanotubes together.