Carbon nanotubes and methods of fabrication thereof using a catalyst precursor

Abstract

Carbon nanotubes including single-walled carbon nanotubes (SWNTS) are grown in a manner that facilitates the formation of distinct, individual nanotubes. In one example embodiment of the present invention, SWNT probe-tips for applications such as atomic force microscopy (AFM) are synthesized on silicon pyramids for integration, for example, onto AFM cantilevers. In another implementation, the growth of SWNTs involves dip coating of silicon pyramids with a liquid phase catalyst followed by chemical vapor deposition (CVD) using methane for growing SWNTs. In another implementation, SWNTs are shortened in an inert atmosphere to achieve desirable lengths, for instance, as used in AFM tips. With these approaches, large-scale arrays of nanotubes can be manufactured, for example, using contact printing for catalyst deposition and controllably shortening the nanotubes via an inert discharge.

What is claimed is:  
     
         1 . A carbon nanotube probe tip comprising: 
 a support structure comprising a tip protruding from a substrate; and    a carbon nanotube extending from the tip.    
     
     
         2 . The carbon nanotube probe tip of  claim 1 , wherein the tip is in the shape of a pyramid.  
     
     
         3 . The carbon nanotube probe tip of  claim 1 , wherein the tip is in the shape of a cone.  
     
     
         4 . The carbon nanotube probe tip of  claim 1 , wherein the support structure includes a wider base portion and a narrower tip portion above the base portion and wherein the carbon nanotube extends from the lower base portion, along the upper tip portion and extending therefrom.  
     
     
         5 . The carbon nanotube probe tip of  claim 4 , wherein the lower base portion has a catalyst material disposed thereon, the catalyst material being configured and arranged for growing the carbon nanotube.  
     
     
         6 . The carbon nanotube probe tip of  claim 1 , wherein the support structure has a catalyst material disposed thereon, the catalyst material being configured and arranged for growing the carbon nanotube.  
     
     
         7 . The carbon nanotube probe tip of  claim 6 , wherein the catalyst material comprises a metal-containing salt, a long-chain molecular compound and a solvent.  
     
     
         8 . The carbon nanotube probe tip of  claim 7 , wherein the catalyst material includes a calcined material that includes metal oxide particles and at least one of: alumina and silica.  
     
     
         9 . The carbon nanotube probe tip of  claim 1 , wherein the carbon nanotube is a single-walled carbon nanotube.  
     
     
         10 . The carbon nanotube probe tip of  claim 1 , wherein the support structure includes a cantilever and wherein the tip protrudes from the cantilever.  
     
     
         11 . The carbon nanotube probe tip of  claim 1 , wherein the support structure includes a tower and wherein the tip is disposed on the tower.  
     
     
         12 . A liquid phase precursor for fabricating one or more carbon nanotubes comprising: 
 a metal-containing salt;    a long-chain molecular compound; and    a solvent.    
     
     
         13 . The precursor of  claim 12 , wherein the metal-containing salt is selected from the group of: chloride, sulfate and nitrate.  
     
     
         14 . The precursor of  claim 13 , wherein the chloride is an inorganic chloride.  
     
     
         15 . The precursor of  claim 14 , wherein the inorganic chloride includes AlCl 3 , SiCl 4 , FeCl 3  and MoO 2 Cl 2 .  
     
     
         16 . The precursor of  claim 15 , wherein the long chain molecule is a surfactant or a polymer.  
     
     
         17 . The precursor of  claim 16 , wherein the long chain molecule is a tri-block copolymer comprising pluronic P-123 poly(alkylene oxide) HO(CH 2 CH 2 O) 20 —(CH 2 CH(CH 3 )O) 70 —(CH 2 CH 2 O) 20 OH.  
     
     
         18 . The precursor of  claim 12 , wherein the solvent is selected from the group of: 
 alcohol, acetone and water.    
     
     
         19 . The precursor of  claim 12 , wherein the metal-containing salt, the long-chain molecular compound and the solvent are configured and arranged to form a catalyst material for growing a carbon nanotube in the presence of a carbon-containing gas.  
     
     
         20 . The precursor of  claim 19 , wherein the metal-containing salt, the long-chain molecular compound and the solvent are configured and arranged to form a catalyst material when calcined.  
     
     
         21 . A method for manufacturing a single-walled nanotube (SWNT), the method comprising: 
 introducing an inert gas to the SWNT; and    applying a voltage between the SWNT and a substrate and shortening the SWNT.    
     
     
         22 . The method of  claim 21 , further comprising contacting the SWNT to the substrate.  
     
     
         23 . The method of  claim 22 , wherein the substrate is a heavily-doped silicon substrate.  
     
     
         24 . The method of  claim 22 , wherein applying a voltage between the SWNT and the substrate includes gradually increasing the voltage applied between the SWNT and the substrate until a loss of nanotube-substrate contact occurs.  
     
     
         25 . The method of  claim 21 , further comprising: 
 using a force calibration curve to detect a stiffness characteristic of the SWNT; and    in response to detecting a stiffness characteristic that indicates that the SWNT is not sufficiently stiff, repeating the steps of introducing an inert gas to the SWNT and applying a voltage between the SWNT and a substrate and shortening the SWNT.    
     
     
         26 . The method of  claim 21 , wherein the SWNT is disposed on an AFM cantilever and wherein applying a voltage between the SWNT and a substrate includes manipulating the cantilever to contact the SWNT to the substrate.  
     
     
         27 . The method of  claim 21 , wherein applying a voltage between the SWNT and a substrate includes using the voltage to align the SWNT in a direction generally normal to the substrate.