Method of forming nano-pads of catalytic metal for growth of single-walled carbon nanotubes

Abstract

Two methods of producing nano-pads of catalytic metal for growth of single walled carbon nanotubes (SWCNT) are disclosed. Both methods utilize a shadow mask technique, wherein the nano-pads are deposited from the catalytic metal source positioned under the angle toward the vertical walls of the opening, so that these walls serve as a shadow mask. In the first case, the vertical walls of the photo-resist around the opening are used as a shadow mask, while in the second case the opening is made in a thin layer of the dielectric layer serving as a shadow mask. Both methods produce the nano-pad areas sufficiently small for the growth of the SWCNT from the catalytic metal balls created after high temperature melting of the nano-pads.

What is claimed: 
     
         1 . A method of producing the nano-pads of catalytic metal for growth of the Single Walled Carbon Nanotubes (SWCNT) using a shadow mask technique, in which the original opening in the photo-resist deposited on the substrate is used to create the nano-pad of catalytic metal of a much smaller area than that of said original opening, wherein the walls of said original opening in the photo-resist serve as a shadow mask for the angled deposition of said nano-pads of catalytic metal, when the catalytic metal source is positioned under an angle to the direction normal to the substrate plane, so that said angle and the said walls of said original opening control the area of the nano-pads. 
     
     
         2 . The method of  claim 1 , wherein said original opening in the photo-resist has a shape of the square, which is oriented toward said catalytic metal source in such a manner that the plane normal to the substrate plane goes through said catalytic metal source and intersects the substrate plane along one of the diagonals of said original square, so that the resultant nano-pad also has the shape of the square located in one of the corners of said original opening, farthest to said catalytic metal source. 
     
     
         3 . The method of  claim 1 , which includes the following processing steps: deposition of the contact pad on the substrate; deposition of a thin layer of the photo-resist and patterning; making the original opening in the photo-resist; angled deposition of said catalytic metal layer to form the nano-pad; removal of the photo-resist, so that only said nano-pad of catalytic metal remains on said contact pad; high-temperature treatment of the nano-pad layer to selectively melt the nano-pad metal and form a spherical ball. 
     
     
         4 . The method of  claim 2 , wherein the area of said square of the original opening in the photo-resist is about 20×20 nm 2 , while the walls of said original opening in the photo-resist are about 20 nm high. 
     
     
         5 . The method of producing the nano-pads of catalytic metal for growth of the SWCNT using a shadow mask technique, in which the original opening is formed in a thin dielectric layer deposited on the contact layer to create the nano-pad of catalytic metal of a much smaller area than that of said original opening, wherein the walls of said original opening in the said dielectric layer serve as a shadow mask for the angled deposition of said nano-pads of catalytic metal, when the catalytic metal source is positioned under an angle to the direction normal to the substrate plane, so that said angle and the height of the walls of said original opening determine the size of the nano-pads. 
     
     
         6 . The method of  claim 5 , wherein said original opening in the dielectric has a shape of the square, said square being oriented toward said catalytic metal source in such a manner that the plane normal to the substrate plane goes through said catalytic metal source and intersects the substrate plane along one of the diagonals of said original square, so that resultant said nano-pad also has the shape of the square. 
     
     
         7 . The method of  claim 5 , which includes the following processing steps: deposition of the contact pad on the substrate; deposition of a thin layer of the dielectric deposition of the photo-resist and patterning; making the original opening in the photo-resist; making the original opening in the dielectric; removal of the photo-resist, angled deposition of said catalytic metal layer to form the nano-pad, removal of the dielectric layer and metal lift-off, so that only said nano-pad of catalytic metal remains on said contact pad; high-temperature treatment of the nano-pad layer to melt the nano-pad metal and form a spherical ball. 
     
     
         8 . The method of  claim 5 , wherein the area of said original opening in the dielectric is about 20×20 nm 2 , while the walls of said original opening in the dielectric are about 20 nm high.