Carbon nanotube probe tip grown on a small probe

Abstract

A method of fabricating a carbon nanotube probe tip and the resultant probe tip, particularly for use in an atomic force microscope. A moderately sharply peaked support structure has its tip cut or flattened to have a substantially flat end of size of about 20 to 200 nm across. The support structure may be formed by etching a conical end into a silica optical fiber. Nickel or other catalyzing metal such as iron is directionally sputtered onto the flat end and the sloped sidewalls of the support structure. The nickel is anisotropically etched to remove all the nickel from the sidewalls but leaving at least 15 nm on the flat end to form a small nickel dot. A carbon nanotube is then grown with the nickel catalyzing its growth such that only a single nanotube forms on the nickel dot and its diameter conforms to the size of the nickel dot.

What is claimed is:  
     
         1 . A method of forming a probe tip, comprising the steps of: 
 providing a member comprising a shaped tip having sidewalls and extending along an axis;    cutting a flat surface in said shaped tip;    anisotropically depositing a catalytic material onto said flat surface and onto said sloping sidewalls;    directionally etching said catalytic material to remove said catalytic material from said sidewalls while leaving a thickness of said catalytic material on said flat surface; and    growing a carbon nanotube on a portion of said catalytic material remaining on said flat surface in a process catalyzed by said catalytic material.    
     
     
         2 . The method of  claim 1 , wherein said flat surface has a minimum lateral size of between 15 and 300 nm.  
     
     
         3 . The method of  claim 1 , wherein said catalytic material comprises nickel.  
     
     
         4 . The method of  claim 1 , wherein said catalytic material comprises iron.  
     
     
         5 . The method of  claim 1 , wherein said member comprises silicon oxide.  
     
     
         6 . The method of  claim 1 , wherein said member is formed from silica fiber.  
     
     
         7 . The method of  claim 6 , wherein said member has said ends formed into said fiber and said sidewalls slope from an axis of said fiber.  
     
     
         8 . The method of  claim 6 , wherein said planar end is cut to be non-perpendicular to an axis of said fiber.  
     
     
         9 . The method of  claim 1 , wherein said cutting step cuts said sidewalls into said member to be parallel to each other.  
     
     
         10 . The method of  claim 1 , wherein said member comprises silicon.  
     
     
         11 . The method of  claim 1 , wherein said shaped tip has a pyramidal shape.  
     
     
         12 . The method of  claim 1 , wherein said anisotropic coating step comprises sputtering.  
     
     
         13 . The method of  claim 1 , wherein said cutting step comprises focused ion beam milling.  
     
     
         14 . The method of  claim 1 , further comprising cutting said carbon nanotube to reduce its length.  
     
     
         15 . The method of  claim 14 , wherein said cutting said carbon nanotube comprises focused ion beam milling.  
     
     
         16 . A probe tip, comprising: 
 a support including a shaped tip having a planar end of minimum lateral extent of between 15 and 300 nm and sidewalls sloping from said planar end;    a catalyzing layer of material capable of catalyzing growth of carbon nanotubes formed on said planar end but not on said sidewalls; and    a single carbon nanotube formed on said catalyzing layer.    
     
     
         17 . The probe tip of  claim 16 , wherein said nanotube is a multi-wall nanotube.  
     
     
         18 . The probe tip of  claim 16 , wherein said material comprises metallic nickel.  
     
     
         19 . The probe tip of  claim 15 , wherein said material comprises nickel oxide.  
     
     
         20 . The probe tip of  claim 15 , wherein said material comprises metallic iron or iron oxide.  
     
     
         21 . The probe tip of  claim 15 , wherein said sidewalls slope from said planar end by between 60° and 90°.  
     
     
         22 . The probe tip of  claim 15 , wherein said catalyzing layer has a thickness of at least 15 nm.  
     
     
         23 . An atomic force microscope including the probe tip of  claim 15  and a vertical actuator, wherein said actuator causes said probe tip to encounter a surface being probed.