Growth of carbon nanotubes using metal-free nanoparticles

Abstract

The present invention provides a method for forming at least one carbon nanotube ( 16 ) by using metal-free catalyst nanoparticles ( 14 ), for example Si or Ge comprising nanoparticles. The method uses the step of decomposing a carbon source gas to form carbon fragments which then recombine at the metal-free catalyst nanoparticles ( 14 ) to grow carbon nanotubes ( 16 ). The method according to embodiments of the invention leads to carbon nanotubes ( 16 ) which do not comprise metal impurities.

1 - 18 . (canceled) 
     
     
         19 . A method for forming at least one carbon nanotube, the method comprising:
 providing at least one metal-free catalyst nanoparticle; and   growing a carbon nanotube from the metal-free catalyst nanoparticle.   
     
     
         20 . The method of  claim 19 , wherein providing at least one metal-free catalyst nanoparticle comprises providing at least one metal-free catalyst nanoparticle in a chemical vapor deposition reactor, and wherein growing a carbon nanotube comprises forming reactive carbon fragments by decomposing a carbon source gas in a chemical vapor deposition reactor and recombining the reactive carbon fragments on top of the at least one metal-free catalyst nanoparticle, whereby at least one carbon nanotube is grown. 
     
     
         21 . The method of  claim 20 , wherein the carbon source gas is a hydrocarbon gas having from one to three carbon atoms. 
     
     
         22 . The method of  claim 21 , wherein the carbon source gas is selected from the group consisting of CH 4 , C 2 H 4 , C 2 H 2 , and C 3 H 6 . 
     
     
         23 . The method of  claim 20 , wherein the carbon source gas is CO. 
     
     
         24 . The method of  claim 20 , wherein providing at least one metal-free catalyst nanoparticle in a chemical vapor deposition reactor comprises providing at least one metal-free catalyst nanoparticle on a substrate and transferring the substrate with the at least one metal-free nanoparticle on it to a chemical vapor deposition reactor. 
     
     
         25 . The method of  claim 24 , wherein providing at least one metal-free catalyst nanoparticle on a substrate comprises providing a layer of metal-free material on the substrate and annealing the layer, whereby at least one metal-free catalyst nanoparticle is formed. 
     
     
         26 . The method of  claim 25 , wherein annealing is performed at a temperature of from 500° C. to 800° C. 
     
     
         27 . The method of  claim 24 , wherein the method further comprises, before providing the at least one metal-free catalyst nanoparticle on the substrate, providing a barrier layer on the substrate, wherein the barrier layer prevents interaction of the at least one metal-free catalyst nanoparticle with the substrate. 
     
     
         28 . The method of  claim 24 , wherein, during decomposing the carbon source gas and growing the at least one carbon nanotube, a temperature of the substrate is maintained at from 800° C. to 1000° C. 
     
     
         29 . The method of  claim 20 , wherein decomposing the carbon source gas is performed by using a hot filament, by using a plasma, or by using a combination of a hot filament and a plasma. 
     
     
         30 . The method of  claim 29 , wherein decomposing the carbon source gas is performed by using a hot filament at a temperature of 950° C. 
     
     
         31 . The method of  claim 19 , wherein the metal-free catalyst nanoparticle is a semiconductor comprising nanoparticle. 
     
     
         32 . The method of  claim 31 , wherein the semiconductor comprising nanoparticle is selected from the group consisting of a SiC comprising nanoparticle, a SiO 2  comprising nanoparticle, a pure silicon nanoparticle, a GeO 2  comprising nanoparticle, and a pure Ge nanoparticle. 
     
     
         33 . The method of  claim 19 , wherein the at least one metal-free catalyst nanoparticle has a diameter of from 0.4 nm to 100 nm. 
     
     
         34 . The method of  claim 19 , further comprising pre-treating the at least one metal-free catalyst nanoparticle before growing the carbon nanotube. 
     
     
         35 . A carbon nanotube grown from a metal-free catalyst nanoparticle. 
     
     
         36 . Use of a metal-free catalyst nanoparticle to grow a carbon nanotube.