Process for forming a hexagonal array
The present invention relates to nanopillar arrays that may have relatively large dimensions and relatively large interpillar distances. The present invention also relates to methods of forming the same. In some embodiments of the invention, methods of forming hexagonal nanopillar arrays include forming a base comprising aluminum; forming a hexagonal pattern of pits in the aluminum; anodizing the aluminum to form aluminum oxide comprising a primary hexagonal nanopore array at the positions of the pits in the aluminum; depositing a conductive material into the nanopores of the primary hexagonal nanopore array; and removing the mask and the aluminum oxide to provide the hexagonal nanopillar array.
1. A method of forming a hexagonal nanopillar array, the method comprising:
forming a base comprising aluminum, wherein forming the base comprises forming a layer of titanium on a substrate, forming a layer of gold on the titanium layer, and forming a layer of aluminum on the gold layer;
forming a hexagonal pattern of pits in the aluminum;
anodizing the aluminum to form aluminum oxide comprising a primary hexagonal nanopore array at positions of the pits in the aluminum;
depositing a conductive material into the nanopores of the primary hexagonal nanopore array; and
removing the aluminum oxide to provide the hexagonal nanopillar array.
2. The method of claim 1 , wherein the hexagonal pattern of pits has a lattice constant in a range of about 300 nm to about 100 μm.
3. The method of claim 1 , wherein each of the pits in the aluminum has a width in a range of about 10 nm to about 600 nm.
4. The method of claim 1 , wherein the titanium layer has a thickness in a range of about 1 nm to about 100 nm.
5. The method of claim 1 , wherein the gold layer has a thickness in a range of about 1 nm to about 100 nm.
6. The method of claim 1 , wherein the aluminum layer has a thickness in a range of about 1 nm to about 1 mm.
7. The method of claim 1 , wherein forming a hexagonal pattern of pits in the aluminum comprises,
pressing a stamp comprising a hexagonal pattern of projections into the aluminum, wherein the hexagonal pattern of projections forms the hexagonal pattern of pits when pressed into the aluminum.
8. The method of claim 7 , wherein the projections comprise silicon nitride.
9. The method of claim 1 , further comprising electropolishing the aluminum after forming the hexagonal pattern of pits and before anodizing the aluminum.
10. The method of claim 1 , wherein the primary hexagonal nanopore array is a mono-domain array.
11. The method of claim 1 , wherein the width of each of the nanopores of the primary hexagonal nanopore array is in a range of about 10 nm to about 400 nm.
12. The method of claim 1 , wherein the lattice constant of the primary hexagonal nanopore array is in a range of about 300 nm to about 100 μm.
13. The method of claim 1 , wherein the aluminum oxide formed by anodization further comprises a secondary hexagonal nanopore array more closely spaced than the primary nanopore array.
14. The method of claim 13 , wherein during depositing of the conductive material, the nanopores of the secondary hexagonal nanopore array that are not part of the primary hexagonal nanopore array are masked.
15. The method of claim 1 , wherein the conductive material comprises a metal.
16. The method of claim 15 , wherein depositing the conductive material comprises electrodepositing the metal in the nanopores of the primary hexagonal nanopore array.
17. The method of claim 15 , wherein the metal comprises at least one metal selected from the group consisting of aluminum, gold, silver, copper, titanium and tantalum.
18. The method of claim 1 , wherein each of the nanopillars of the primary hexagonal nanopillar array has a height in a range of about 10 nm to about 1 mm.
19. The method of claim 1 , wherein each of the nanopillars of the primary hexagonal nanopillar array has a width in a range of about 1 nm to about 450 nm.
20. The method of claim 1 , wherein the interpillar distance of the primary hexagonal nanopillar array is in a range of about 20 nm to about 100 μm.
21. A method of forming a hexagonal nanopillar array, the method comprising:
forming a base comprising aluminum;
forming a hexagonal pattern of pits in the aluminum, wherein forming the hexagonal pattern of pits comprises applying a photoresist to a surface of the aluminum, creating a photoresist pattern defining exposed regions of the surface of the aluminum at positions of the hexagonal pattern of pits, treating the exposed regions of the surface of the aluminum through the photoresist pattern to create the hexagonal array of pits in the aluminum, and removing the photoresist;
anodizing the aluminum to form aluminum oxide comprising a primary hexagonal nanopore array at positions of the pits in the aluminum;
depositing a conductive material into the nanopores of the primary hexagonal nanopore array; and
removing the aluminum oxide to provide the hexagonal nanopillar array.
22. A method of forming a hexagonal nanopillar array, the method comprising:
forming a base comprising aluminum;
forming a hexagonal pattern of pits in the aluminum;
anodizing the aluminum to form aluminum oxide comprising a primary hexagonal nanopore array at positions of the pits in the aluminum;
depositing a conductive material into the nanopores of the primary hexagonal nanopore array; and
removing the aluminum oxide to provide the hexagonal nanopillar array, wherein the method further comprises resizing widths of the nanopores of the primary hexagonal array after anodization.
23. The method of claim 22 , wherein resizing the widths of the nanopores is achieved by applying phosphoric acid to the nanopores.
24. The method of claim 22 , wherein the width of each of the nanopores of the primary hexagonal nanopore array after resizing is in a range of about 10 nm to about 600 nm.