Nanotube growth and device formation

Abstract

An apparatus and method for forming catalyst particles to grow nanotubes is disclosed. In addition, an apparatus and method for forming nanotubes using the catalytic particles is also disclosed. The particles formed may have different diameters depending upon how they are formed. Once formed, the particles are deposited on a substrate. Once deposited, the mobility of the particles is restricted and nanotubes and/or nanotube portions are grown on the particles. Nanotube portions having different diameters may be formed and the portions may be connected to form nanotubes with different diameters along the length of the nanotube.

1 . A method, comprising: 
 forming a metal particle of a size suitable for use as a catalyst in forming a nanotube by an electrochemical process on a semiconductor substrate.    
     
     
         2 . The method of claim of  1 , wherein the electrochemical process comprises an oxidation-reduction reaction.  
     
     
         3 . The method of  claim 2 , wherein the forming a metal particle comprises introducing an ionic precursor of the metal particle into a bath and reducing the ionic precursor by chemical reaction.  
     
     
         4 . The method of  claim 1 , wherein forming the metal particle comprises forming an alloy.  
     
     
         5 . The method of  claim 4 , wherein forming the alloy comprises forming a Group VIII metal alloy.  
     
     
         6 . The method of  claim 4 , wherein forming the alloy comprises forming a Group VI metal alloy.  
     
     
         7 . The method of  claim 4 , wherein forming the alloy comprises forming an alloy including a Group VIII metal and a Group VI metal.  
     
     
         8 . A method, comprising: 
 forming a first portion of a nanotube with a first diameter;    forming a second portion of the nanotube with a second diameter; and    attaching the first portion to the second portion to form the nanotube.    
     
     
         9 . The method of  claim 8 , wherein the diameter of the first portion and the second portion are different.  
     
     
         10 . The method of  claim 8 , wherein forming the first portion occurs on a first metal particle of a first size.  
     
     
         11 . The method of  claim 10 , wherein forming the second portion occurs on a second metal particle of a second size.  
     
     
         12 . The method of  claim 11 , wherein the first and second particles are different sizes.  
     
     
         13 . The method of  claim 11 , wherein attaching the first portion to the second portion comprises: 
 dissolving the first particle; and    exposing the first portion to a first one of an amine functional group and a carboxyl functional group.    
     
     
         14 . The method of  claim 13 , further comprising: 
 exposing the second particle to a second one of an amine functional and a carboxyl functional group, the second one of an amine functional and a carboxyl functional group being the opposite of the first one of an amine functional and a carboxyl functional group.    
     
     
         15 . A method, comprising: 
 constraining movement of a metal particle suitable for use as a catalyst in forming a nanotube on a semiconductor substrate.    
     
     
         16 . The method of  claim 15 , wherein constraining the particle comprises: 
 depositing the particle into a via of the substrate.    
     
     
         17 . The method of  claim 15 , wherein the substrate is a first substrate and constraining the particle comprises: 
 depositing the particle on a surface of the substrate, and    fusing a patterned second substrate including vias to the surface of the first substrate to form a structure, the vias facing the first substrate surface and aligned such that the metal particle is encompassed within the vias of the second substrate when the first substrate and second substrate are fused together.    
     
     
         18 . The method of  claim 15 , further comprising: 
 removing a portion of the second substrate to define a via.    
     
     
         19 . The method of  claim 18 , further comprising: 
 forming a nanotube on the metal particle.    
     
     
         20 . The method of  claim 19 , wherein forming the nanotube comprises: 
 one of exposing the particle to a carbon-containing gas and heat process, and exposing the particle to a laser ablation process to encourage the nanotube to grow on the particle.    
     
     
         21 . The method of  claim 20 , further comprising: 
 exposing the particle to an electric field to affect a direction of growth of the nanotube.    
     
     
         22 . An apparatus, comprising: 
 a first nanotube portion with a first diameter; and    a second nanotube portion with a second diameter, the second nanotube portion coupled to the first nanotube portion to form a nanotube.    
     
     
         23 . The apparatus of  claim 22 , wherein the first diameter and the second diameter are different.  
     
     
         24 . The apparatus of  claim 22 , wherein the first nanotube portion is a single-walled nanotube portion.  
     
     
         25 . The apparatus of  claim 24 , wherein the second nanotube portion is a multi-walled nanotube portion.  
     
     
         26 . An apparatus, comprising: 
 a metal particle of a size suitable for use as a catalyst in forming a nanotube formed by an electrochemical process on a semiconductor substrate.    
     
     
         27 . The apparatus of  claim 26 , wherein the metal particle comprises an alloy.  
     
     
         28 . The apparatus of  claim 27 , wherein the alloy comprises a Group VIII metal.  
     
     
         29 . The apparatus of  claim 27 , wherein the alloy comprises a Group VI metal.  
     
     
         30 . The apparatus of  claim 27 , wherein the alloy comprises a Group VIII metal and a Group VI metal.  
     
     
         31 . A method, comprising: 
 extracting a metal particle of a size suitable for use as a catalyst in forming a nanotube from an electroless bath; and    depositing the metal particle on a substrate.    
     
     
         32 . The method of  claim 31 , wherein extracting and depositing the metal particle on the substrate comprises: 
 immersing the substrate into the bath containing the metal particle.    
     
     
         33 . The method of  claim 31 , wherein extracting and depositing the metal particle on the substrate comprises: 
 pouring the bath containing the metal particle over a surface of the substrate.    
     
     
         34 . The method of  claim 31 , wherein extracting the metal particle is performed by a method selected from the group consisting of: 
 filtering the metal particle from the bath,    extracting the metal particle by centrifugation,    evaporating the bath, and    mechanically agitating the bath.    
     
     
         35 . The method of  claim 34 , further comprising: 
 after extraction by centrification, exposing the metal particle to a volatile liquid selected from one of methanol and ethanol.