Carbon nanotube arrays for field electron emission and methods of manufacture and use

Abstract

A method for preparation of carbon nanotubes (CNTs) bundles for use in field emission devices (FEDs) includes forming a plurality of carbon nanotubes on a substrate, contacting the carbon nanotubes with a polymer composition comprising a polymer and a solvent, and removing at least a portion of the solvent so as to form a solid composition from the carbon nanotubes and the polymer to form a carbon nanotube bundle having a base with a periphery, and an elevated central region where, along the periphery of the base, the carbon nanotubes slope toward the central region.

1 . A carbon nanotube bundle comprising a plurality of carbon nanotubes and polymer disposed at least partially around the carbon nanotubes, the carbon nanotubes disposed on a substrate, and the bundle having a base with a periphery, and an elevated central region; wherein, along the periphery of the base, the nanotubes slope toward the central region. 
     
     
         2 . The carbon nanotube bundle of  claim 1 ,
 the bundle having a first axis substantially perpendicular to the substrate, and   each nanotube having a second axis;   
       the bundle further comprising an outer portion and an inner portion;
 the second axis of each nanotube within the outer potion being substantially perpendicular to the first axis, and 
 the second axis of each nanotube within the inner portion being substantially parallel to the first axis. 
 
     
     
         3 . The carbon nanotube bundle of  claim 1 , further comprising a catalytic metal layer disposed together with the plurality of carbon nanotubes. 
     
     
         4 . The carbon nanotube bundle of  claim 2 , wherein the outer portion and the inner portion are separated by an intermediate portion. 
     
     
         5 . A carbon nanotube array, comprising a plurality of the carbon nanotube bundles of  claim 3 . 
     
     
         6 . The carbon nanotube array of  claim 5 , wherein the catalytic metal layer defines a plurality of separate pads. 
     
     
         7 . The carbon nanotube array of  claim 6 , wherein at least one of the carbon nanotube bundles is disposed on each of the separate pads. 
     
     
         8 . The carbon nanotube array of  claim 7 , wherein the array further comprises a metal cathode in electrical communication with the carbon nanotube bundles and an anode disposed in proximity to the carbon nanotubes. 
     
     
         9 . A method of making a carbon nanotube bundle, which method comprises:
 forming a plurality of carbon nanotubes on a substrate;   contacting the carbon nanotubes with a polymer composition comprising a polymer and a solvent; and   removing at least a portion of the solvent so as to form a solid composition from the carbon nanotubes and the polymer to form a carbon nanotube bundle having a base with a periphery, and an elevated central region; wherein, along the periphery of the base, the carbon nanotubes slope toward the central region.   
     
     
         10 . The method of  claim 9 , further comprising removing at least a portion of the polymer from the bundle. 
     
     
         11 . The method of  claim 10 , wherein removing at least a portion of the polymer from the bundle comprises removing substantially all of the polymer from the bundle. 
     
     
         12 . The method of  claim 9 , wherein forming a solid composition comprises removing a majority of the solvent from the polymer composition. 
     
     
         13 . The method of  claim 9 , wherein forming a solid composition comprises removing substantially all of the solvent from the polymer composition. 
     
     
         14 . The method of  claim 9 , wherein the solvent is removed by evaporation. 
     
     
         15 . The method of  claim 9 , wherein the glass transition point of the polymer is no more than 25° C. 
     
     
         16 . The method of  claim 15 , wherein the polymer is polyvinyl methyl ether (PVME). 
     
     
         17 . A field emission device, comprising:
 a cathode;   an anode;   a carbon nanotube array disposed on the cathode, the carbon nanotube array comprising;
 a plurality of carbon nanotube bundles, each bundle comprising a plurality of carbon nanotubes disposed on a substrate; and 
 each bundle having a base with a periphery, and an elevated central region; 
 wherein, along the periphery of the base, the nanotubes slope toward the central region and, at the elevated central region, the carbon nanotubes form a star-shaped plateau with at least four points. 
   
     
     
         18 . The field emission device of  claim 17 , further comprising a catalytic metal layer between the substrate and the plurality of carbon nanotubes. 
     
     
         19 . The field emission device of  claim 18 , wherein the catalytic metal layer defines a plurality of separate pads. 
     
     
         20 . The field emission device of  claim 19 , wherein at least one of the carbon nanotube bundles is disposed on each of the separate pads.