Growth of and Defect Reduction in Nanoscale Materials

Abstract

Methods by which the growth of a nanostructure may be precisely controlled by an electrical current are described here. In one embodiment, an interior nanostructure is grown to a predetermined geometry inside another nanostructure, which serves as a reaction chamber. The growth is effected by a catalytic agent loaded with feedstock for the interior nanostructure. Another embodiment allows a preexisting marginal quality nanostructure to be zone refined into a higher-quality nanostructure by driving a catalytic agent down a controlled length of the nanostructure with an electric current. In both embodiments, the speed of nanostructure formation is adjustable, and the growth may be stopped and restarted at will. The catalytic agent may be doped or undoped to produce semiconductor effects, and the bead may be removed via acid etching.

1 . A method of zone refining a nanostructure, comprising:
 a) providing an initial unrefined nanostructure containing an initial amount of defects;   b) providing a catalytic agent disposed about the initial unrefined nanostructure;   c) zone refining the initial unrefined nanostructure into a reformed nanostructure for a desired length by passing an electrical current through the initial unrefined nanostructure sufficient to controllably move the catalytic agent for a desired distance in a desired direction.   
     
     
         2 . The method of zone refining a nanostructure of  claim 1 , wherein the zone refining step is done on a chip. 
     
     
         3 . The method of zone refining a nanostructure of  claim 1 , wherein the initial amount of defects in the reformed nanostructure is substantially reduced. 
     
     
         4 . The method of zone refining a nanostructure of  claim 1 , wherein the reformed nanostructure is essentially defect free. 
     
     
         5 . The method of zone refining a nanostructure of  claim 1 , comprising removing the catalytic agent after the zone refining step. 
     
     
         6 . The method of zone refining a nanostructure of  claim 1 , wherein:
 a) the initial unrefined nanostructure is doped with an initial dopant;   b) the catalytic agent is doped with a dopant different than the initial dopant; and   c) the reformed nanostructure is doped with the catalytic agent dopant.   
     
     
         7 . The method of zone refining a nanostructure of  claim 6 , wherein the reformed nanostructure comprises a Schottky diode. 
     
     
         8 . The method of zone refining a nanostructure of  claim 6 , wherein the resulting nanostructure comprises a diode. 
     
     
         9 . The method of zone refining a nanostructure of  claim 6 , wherein the resulting nanostructure comprises a heterojunction. 
     
     
         10 . The method of zone refining a nanostructure of  claim 1 , comprising modifying a resonance frequency of the nanostructure by moving the catalytic agent to a specific location. 
     
     
         11 . The method of zone refining a nanostructure of  claim 1 , wherein the catalytic agent acts as one or more of the group consisting of a magnetic contact, a static oscillation resonance mass, a static rotational torque point, a means for driving the nanostructure, a means for moving the nanostructure, and a means for actuating the nanostructure. 
     
     
         12 . The method of zone refining a nanostructure of  claim 1 , wherein the catalytic agent is essentially cobalt. 
     
     
         13 . The method of zone refining a nanostructure of  claim 1 , wherein the catalytic agent disposed about the initial unrefined nanostructure in one or more positions from the group consisting of: partially or completely inside an interior region, partially or completely outside, and partially or completely at an end. 
     
     
         14 . The method of zone refining a nanostructure of  claim 1 , wherein the initial unrefined nanostructure has a chemical composition comprising one or more from the group consisting of: doped or undoped B x C y N z ., doped or undoped MoS 2 , doped or undoped TiSe 2 , and doped BN. 
     
     
         15 . The method of zone refining a nanostructure of  claim 1 , wherein the initial unrefined nanostructure has a chemical composition sufficiently conductive to allow zone refining. 
     
     
         16 . A product produced by the method of nanostructure growth of  claim 1 , comprising the reformed nanostructure product produced by the method of  claim 1 .