Methods for fabricating metal nanowires
View Patent ↗Methods for the preparation of long, dimensionally uniform, metallic nanowires that are removable from the surface on which they are synthesized. The methods include the selective electrodeposition of metal nanowires at step edges present on a stepped surface, such as graphite, from an aqueous solution containing a metal or metal oxide. Where a metal oxide is first deposited, the metal oxide nanowires are reduced via a gas phase reduction at elevated temperatures to metal nanowires. Alternatively, beaded or hybrid nanowires comprising a metal A into which nanoparticles of a metal B have been inserted may be prepared by first electrodepositing nanoparticles of metal B selectively along step edges of a stepped surface, capping these nanoparticles with a molecular layer of an organic ligand, selectively electrodepositing nanowire segments of metal A between nanoparticles of metal B and then heating the surface of the hybrid nanowire under reducing conditions to remove the ligand layer. In all three methods, the nanowires may be removed from the stepped surface by embedding the wires in a polymer film, and then peeling this film containing the embedded wires off of the stepped surface.
1. A method for preparing a circuit comprising metallic nanometer scale wires comprising the steps of:
providing a stepped surface comprising a common plane and step edges;
electrodepositing a plurality of wires each comprising a chain of metal grains linearly arranged along the common plane at the step edge of the stepped surface, wherein forming the electrodepositing of wires includes linearly depositing along the common plane at the step edge of the stepped surface a beaded chain of metal nuclei, and
forming first and second metal contacts coupled to first and second ends of the plurality of wires.
2. The method of claim 1 wherein the step of electrodepositing a plurality of wires includes applying a nucleation pulse to an aqueous solution including a desired metal.
3. The method of claim 2 wherein the step of electrodepositing a plurality of wires further includes applying a deposition potential to the aqueous solution.
4. The method of claim 3 wherein an over potential corresponding to the deposition potential is less than about −400 millivolts.
5. The method of claim 1 further comprising the step of coupling a second circuit to the first and second contacts, the second circuit comprising a power source.
6. The method of claim 1 wherein the metal grains have a diameter in the range of about 10 to 50 nanometers.
7. The method of claim 1 wherein the stepped surface comprises a basal-plane orientation.
8. The method of claim 1 wherein the stepped surface is comprised of graphite.