Copper nanocrystals and methods of producing same

• US 20040089101A1
• Filed: 11/08/2002
• Published: 05/13/2004
• Est. Priority Date: 11/08/2002
• Status: Active Grant

• Current Assignee: Wayne State University
• Original Assignee: Wayne State University
• Inventors: Winter, Charles H., Dezelah, Charles L. IV, Yu, Zhengkun
• Granted Patent: US 6,887,297 B2
• Time in Patent Office: Days
• US Class Current: 75/362
• CPC Class Codes: B22F 1/054 Nanosized particles
• CPC Class Codes: B22F 1/10 Metallic powder containing lubricating or binding agents; Metallic powder containing organic material
• CPC Class Codes: B22F 1/102 Metallic powder coated with organic material
• CPC Class Codes: B22F 1/145 Chemical treatment, e.g. passivation or decarburisation
• CPC Class Codes: B22F 2998/00 Supplementary information concerning processes or compositions relating to powder metallurgy
• CPC Class Codes: B22F 2999/00 Aspects linked to processes or compositions used in powder metallurgy
• CPC Class Codes: B22F 9/24 starting from liquid metal compounds, e.g. solutions
• CPC Class Codes: B82Y 30/00 Nanotechnology for materials or surface science, e.g. nanocomposites

Abstract

The invention relates to methods of making monodisperse nanocrystals comprising the steps of reducing a copper salt with a reducing agent, providing a passivating agent comprising a nitrogen and/or an oxygen donating moitey and isolating the copper nanocrystals. Moreover, the invention relates to methods for making a copper film comprising the steps of applying a solvent comprising copper nanocrystals onto a substrate and heating the substrate to form a film of continuous bulk copper from said nanocrystals. Finally, the invention also relates to methods for filling a feature on a substrate with copper comprising the steps of applying a solvent comprising copper nanocrystals onto the featured substrate and heating the substrate to fill the feature by forming continuous bulk copper in the feature.

Claims

1. A method of making monodisperse nanocrystals comprising the steps:

(a) reducing a copper salt with a reducing agent to obtain reduced copper;

(b) providing a passivating agent to contact said reduced copper, wherein said passivating agent comprises at least one moiety selected from the group consisting of a nitrogen donor and an oxygen donor;

(c) isolating said nanocrystals comprising said reduced copper.

2. The method of claim 1, wherein the passivating agent comprises an imidazole moiety.

3. The method of claim 1, wherein the nitrogen donor is selected from the group consisting of imidazole, pyridine, bipyridine, phenanthroline, ammine, amine, nitrile, and nitride.

4. The method of claim 1, wherein the passivating agent is 1-decyl-2-methylimidazole.

5. The method of claim 1, wherein the passivating agent comprises a ammonium or alkylammonium alkylcarboxylate moiety.

6. The method of claim 1, wherein the oxygen donor is selected from the group consisting of tetraoctylammonium, alkoxides, oxides, ethers, carboxylates, acetoacenoates, sulphoxide, hydroxide, acetate, lactate, propionate, oxalate, and maltolate.

7. The method of claim 1, wherein the oxygen donor is selected from the group consisting of sodium decanoate, tetraoctylammonium octylxanthate, potassium octylxanthate and tetraoctylammonium octylxanthate.

8. The method of claim 1, wherein the passivating agent is tetra-n-octylammonium decanoate.

9. The method of claim 1, wherein said nanocrystals are about 1 to about 20 nanometers in size.

10. The method of claim 1, where the nanocrystals melt at less than about 350°

C.

11. The method of claim 1, wherein the nanocrystals are soluble in a solvent.

12. The method of claim 11, wherein the solvent is selected from the group consisting of water, acetonitrile, methanol, isopropanol, hexanes, dodecane, toluene, cyclohexanone, diethyl ether, tetrahydrofuran, ethyl lactate, dichloromethane, acetone and ethanol.

13. The method of claim 1, wherein the passivating agent volatilizes between about 125°

C. to about 250°

C.

14. The method of claim 1, wherein weight loss upon heating said nanocrystals, is in the range of about 15 to about 40%.

15. The method of claim 1, wherein the isolation of said nanocrystals takes place in the presence of a surfactant.

16. The method of claim 15, wherein said surfactant 1-heptyl-4-(4-pyridyl)pyridium bromide.