Controlled growth of gallium nitride nanostructures

Abstract

A transition metal substituted, amorphous mesoporous silica framework with a high degree of structural order and a narrow pore diameter distribution (±0.15 nm FWHM) was synthesized and used for the templated growth of GaN nanostructures, such as single wall nanotubes, nanopipes and nanowires. The physical properties of the GaN nanostructures (diameter, diameter distribution, electronic characteristic) can be controlled by the template pore diameter and the pore wall chemistry. GaN nanostructures can find applications, for example, in nanoscale electronic devices, such as field-emitters, and in chemical sensors.

1 . A method for producing a GaN nanostructure, comprising: 
 providing a framework of a mesoporous siliceous structure having pores with a predetermined pore diameter and containing a catalytic metal disposed in the pores, and    exposing the framework to a gallium-containing reactant and a nitrogen-containing reactant at a predetermined temperature,    thereby producing the GaN nanostructure with a diameter or cross-sectional area that correlates with the predetermined pore diameter.    
     
     
         2 . The method of  claim 1 , wherein the catalytic metal is selected from the Group VIII of the periodic system.  
     
     
         3 . The method of  claim 1 , wherein the catalytic metal disposed in the pores has a concentration between 0.1 and 10 wt %.  
     
     
         4 . The method of  claim 1 , wherein the catalytic metal disposed in the pores has a concentration between 0.5 and 5 wt %.  
     
     
         5 . The method of  claim 1 , wherein the catalytic metal comprises at least one element selected from the group consisting of Fe, Co and Ni.  
     
     
         6 . The method of  claim 1 , wherein the catalytic metal comprises Ni.  
     
     
         7 . The method of  claim 1 , wherein the mesoporous siliceous structure comprises MCM-41.  
     
     
         8 . The method of  claim 1 , wherein the predetermined pore diameter is between 1 nm and 10 nm.  
     
     
         9 . The method of  claim 1 , wherein the reactant comprises gallium metal.  
     
     
         10 . The method of  claim 1 , wherein the reactant comprises a metalorganic compound selected from the group consisting of trimethyl-gallium, triethyl-gallium, and gallium acetyl acetonate.  
     
     
         11 . The method of  claim 1 , wherein the reactant comprises a gallium halide.  
     
     
         12 . The method of  claim 11 , wherein the reactant comprises GaCl 3 .  
     
     
         13 . The method of  claim 1 , wherein the nitrogen-containing reactant comprises ammonia (NH 3 ).  
     
     
         14 . The method of  claim 1 , wherein providing the framework includes the steps of preparing a mixture of siliceous MCM-41 with boehmite (γ-AlOOH), placing the mixture on a support, and calcining the supported mixture.  
     
     
         15 . The method of  claim 14 , wherein the support comprises a silicon wafer.  
     
     
         16 . The method of  claim 1 , wherein the nanostructure comprises at least one of nanotubes, nanowires and nanopipes.  
     
     
         17 . The method of  claim 1 , wherein the nanostructure comprises nanotubes and wherein the metal ions are dispersed in the mesoporous siliceous framework, and wherein the catalytic metal forms catalytic sites in the pores, with a size of the catalytic sites determined by a quantity of catalytic metal ions in the mesoporous siliceous framework.  
     
     
         18 . The method of  claim 1 , wherein the nanostructure comprises nanowires and the diameter or cross-sectional area of the nanowires is substantially identical to the predetermined pore diameter.  
     
     
         19 . The method of  claim 1 , further including, at a temperature less than the predetermined temperature, exposing the produced GaN nanostructure to a metalorganic indium-containing reactant, a metalorganic gallium-containing reactant and the nitrogen-containing reactant, thereby producing a GaN dendritic structure that includes one or more nanostructures originating from a site located along a free section of the produced GaN nanostructure.  
     
     
         20 . The method of  claim 1 , further including the step of exposing the framework to hydrogen before exposing the framework to the gallium-containing and nitrogen-containing reactants.