Copper nanocrystals and methods of producing same

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.

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.