Fabrication method for arranging ultra-fine particles
View Patent ↗A method and resultant device, in which metal nanoparticles are self-assembled into two-dimensional lattices. A periodic hole pattern (wells) is fabricated on a photoresist substrate, the wells having an aspect ratio of less than 0.37. The nanoparticles are synthesized within inverse micelles of a polymer, preferably a block copolymer, and are self-assembled onto the photoresist nanopatterns. The nanoparticles are selectively positioned in the holes due to the capillary forces related to the pattern geometry, with a controllable number of particles per lattice point.
1. A fabrication method for arranging ultra-fine particles into arrays of wells, comprising:
a) providing a substrate;
b) forming wells with an aspect ratio of less than 0.37 through the surface of said substrate;
c) forming micelles containing nanoparticles; and
d) self-assembling the micelles in said wells.
2. The fabrication method of claim 1 in which the wells have an aspect ratio of less than or equal to 0.3.
3. The fabrication method of claim 1 wherein the nanoparticles are metal nanoparticles.
4. The fabrication method of claim 3 wherein the metal is cobalt.
5. The fabrication method of claim 1 wherein said nanoparticles have diameters of 0.5 to 500 nm and said wells are less than 1 μm in diameter.
6. The fabrication method of claim 1 wherein the diameter of said micelles in dry condition is 0.01 to 1.0 times the diameter of said wells.
7. The fabrication method of claim 1 wherein the diameter of said micelles in solution is less than 1.5 times the diameter of said wells.
8. The fabrication method of claim 1 wherein said micelles are formed by steps comprising:
a) adding inverse micelles in a solution of hydrophobic liquid;
b) synthesizing nanoparticles within said inverse micelles; and
c) self-assembling the micelles in said wells.
9. The fabrication method of claim 8 in which the micelles are self-assembled in said wells by dipping said substrate into a solution of the micelles.
10. The fabrication method of claim 8 in which the micelles are self-assembled in said wells by spin-casting the micelles onto the surface of said substrate.
11. The fabrication method of claim 8 in which the hydrophobic liquid is toluene.
12. The fabrication method of claim 1 wherein the number of said nanoparticles within said wells is controlled by process parameters.
13. The fabrication method of claim 12 wherein the process parameters comprise a parameter selected from a group consisting of micelle concentration, time period for dip-coating, spinning speed for spin coating, temperature, solvent evaporation speed, selection of solvent, selection of micelle composition, selection of substrate, and selection of photoresist material.
14. The fabrication method of claim 1 , wherein said wells are arranged in an ordered manner.
15. The fabrication method of claim 1 , wherein said wells are arranged with periodicity.
16. The fabrication method of claim 1 , wherein said wells are arranged in a random manner.
17. The fabrication method of claim 1 wherein said wells are formed using electron beam lithography.
18. The fabrication method of claim 1 wherein said wells are formed using UV irradiation.
19. The fabrication method of claim 1 wherein said wells are formed using holographic lithography.
20. The fabrication method of claim 1 wherein said wells are in the form of periodic elongate grooves.
21. The fabrication method of claim 1 wherein said wells are 100–200 nm deep.
22. A fabrication method for arranging ultra-fine particles into an array of wells, comprising:
coating a GaAs substrate surface with a photo sensitive chemical resistant to acid;
forming wells with aspect ratios less than 0.37 through the surface of said substrate using holographic lithography; and
self-assembling micelles containing cobalt nanoparticles in said wells.
23. The fabrication method of claim 22 in which the micelles are self-assembled in said wells by dip casting.
24. The fabrication method of claim 22 in which the micelles are self-assembled in said wells by spin casting.