Field emission devices using modified carbon nanotubes

Abstract

The present invention relates to a field emission device comprising an anode and a cathode, wherein said cathode includes carbon nanotubes nanotubes which have been subjected to energy, plasma, chemical, or mechanical treatment. The present invention also relates to a field emission cathode comprising carbon nanotubes which have been subject to such treatment. A method for treating the carbon nanotubes and for creating a field emission cathode is also disclosed. A field emission display device containing carbon nanotube which have been subject to such treatment is further disclosed.

1 . A field emission device comprising: 
 a cathode; and    an anode spaced from the cathode,    wherein said cathode includes emitters comprising carbon nanotubes which have been subjected to energy, plasma, chemical, or mechanical treatment.    
     
     
         2 . The field emission device of  claim 1 , wherein said nanotubes are substantially cylindrical carbon fibrils having one or more graphitic layers concentric with their cylindrical axes, said carbon fibrils being substantially free of pyrolytically deposited carbon overcoat, having a substantially uniform diameter between 1 nm and 100 nm and having a length to diameter ratio greater than 5.  
     
     
         3 . The field emission device of  claim 1 , wherein said nanotubes are in the form of aggregates selected from the group consisting of cotton candy aggregates.  
     
     
         4 . The field emission device of  claim 1 , wherein said nanotubes have a morphology resembling a fishbone.  
     
     
         5 . The field emission device of  claim 1 , wherein said nanotubes are single wall nanotubes.  
     
     
         6 . The field emission device of  claim 1 , wherein said nanotubes are in the form of a film or mat.  
     
     
         7 . The field emission device of  claim 1 , wherein said nanotubes have been treated with an ion beam.  
     
     
         8 . The field emission device of  claim 1 , wherein said nanotubes have been treated with a gallium ion beam.  
     
     
         9 . The field emission device of  claim 1 , wherein said nanotubes have been treated with a beam of ions selected from the group consisting of hydrogen, helium, argon, carbon, oxygen, and xenon ions.  
     
     
         10 . The field emission device of  claim 1 , wherein said chemical treatment is selected from the group consisting of acid treatment, metal vapor treatment, chemical vapor transport and chemical sorption.  
     
     
         11 . The field emission device of  claim 1 , wherein said chemical treatment is performed with chemical reagents selected from the group consisting of oxidizing agents, electrophiles, nucleophiles, reducing agents, strong acids, strong bases and mixtures thereof.  
     
     
         12 . The field emission device of  claim 1 , wherein said chemical treatment is performed with phthalocyanines or porphyrins.  
     
     
         13 . The field emission device of  claim 1  wherein said energy treatment is performed with an energy source selected from a group consisting of electromagnetic radiation, ionizing radiation, atomic beams, electron beams, ultraviolet light, microwave radiation, gamma ray, x-ray, neutron beam, molecular beams and laser beam.  
     
     
         14 . The field emission device of  claim 1  wherein said plasma treatment is performed with a plasma selected from a group consisting of oxygen, hydrogen, ammonia, helium, argon, water, nitrogen, ethylene, carbon tetrafluoride, sulfur hexafluoride, perfluoroethylene, fluoroform, difluoro-dichloromethane, bromo-trifluoromethane, chlorotrifluoromethane and mixtures thereof.  
     
     
         15 . The field emission device of  claim 1 , wherein said treatment results in the introduction of metal atoms onto the carbon nanotubes.  
     
     
         16 . The field emission device of  claim 1 , wherein said treatment results in the introduction of functional groups onto the carbon nanotubes.  
     
     
         17 . The field emission device of  claim 16 , wherein said functional groups have been introduced by chemical sorption.  
     
     
         18 . The field emission device of  claim 1 , wherein said treatment comprises heating the carbon nanotubes in the presence of metal vapor.  
     
     
         19 . The field emission device of  claim 1 , wherein said treatment comprises chemisorption followed by heat treatment.  
     
     
         20 . The field emission device of  claim 1 , wherein said treatment includes annealing said nanotubes.  
     
     
         21 . The field emission device of  claim 1 , wherein said cathode further includes a binder.  
     
     
         22 . The field emission device of  claim 21 , wherein said binder is a conductive carbon paste, conductive metal paste or carbonizable polymer.  
     
     
         23 . A process for treating carbon nanotubes comprising the step of bombarding carbon nanotubes with ions.  
     
     
         24 . The process for treating carbon nanotubes of  claim 23 , wherein the nanotubes are bombarded with gallium ions.  
     
     
         25 . The process of treating carbon nanotubes of  claim 23 , wherein the nanotubes are bombarded with ions selected from the group consisting of hydrogen, helium, argon, carbon, oxygen, and xenon ions.  
     
     
         26 . Carbon nanotubes formed by the process of  claim 23 .  
     
     
         27 . A field emission cathode comprising carbon nanotubes, wherein said nanotubes have been subjected to energy, plasma, chemical, or mechanical treatment.  
     
     
         28 . The field emission cathode of  claim 27 , wherein said nanotubes are substantially cylindrical carbon fibrils having one or more graphitic layers concentric with their cylindrical axes, said carbon fibrils being substantially free of pyrolytically deposited carbon overcoat, having a substantially uniform diameter between 1 nm and 100 nm and having a length to diameter ratio greater than 5.  
     
     
         29 . The field emission cathode of  claim 27 , wherein said nanotubes are in the form of aggregates selected from the group consisting of cotton candy aggregates or bird nest aggregates.  
     
     
         30 . The field emission cathode of  claim 27 , wherein said nanotubes have a morphology resembling a fishbone.  
     
     
         31 . The field emission cathode of  claim 27  wherein said nanotubes are single wall nanotubes.  
     
     
         32 . The field emission cathode of  claim 27 , wherin said nanotubes are in the form of a film or mat.  
     
     
         33 . The field emission cathode of  claim 27 , wherein said nanotubes have been treated with an ion beam.  
     
     
         34 . The field emission cathode of  claim 27 , wherein said nanotubes have been treated with a gallium ion beam.  
     
     
         35 . The field emission cathode of  claim 27 , wherein said nanotubes have been treated with a beam of ions selected from the group consisting of hydrogen, helium, argon, carbon, oxygen, and xenon ions.  
     
     
         36 . The field emission cathode of  claim 27 , wherein said chemical treatment is selected from the group consisting of acid treatment, metal vapor treatment, chemical vapor transport, and chemical sorption.  
     
     
         37 . The field emission cathode of  claim 27 , wherein said chemical treatment is performed with chemical reagents selected from the group consisting of oxidizing agents, electrophiles, nucleophiles, reducing agents, strong acids, strong bases and mixtures thereof.  
     
     
         38 . The field emission cathode of  claim 27 , wherein said chemical treatment is performed with phthalocyanines or porphyrins.  
     
     
         39 . The field emission cathode of  claim 27 , wherein said energy treatment is performed with an energy source selected from a group consisting of electromagnetic radiation, ionizing radiation, atomic beams, electron beams, ultraviolet light, microwave radiation, gamma ray, x-ray, neutron beam, molecular beams and laser beam.  
     
     
         40 . The field emission cathode of  claim 27 , wherein said plasma treatment is performed with a plasma selected from a group consisting of oxygen, hydrogen, ammonia, helium, argon, water, nitrogen, ethylene, carbon tetrafluoride, sulfur hexafluoride, perfluoroethylene, fluoroform, difluoro-dichloromethane, bromo-trifluoromethane, chlorotrifluoromethane and mixtures thereof.  
     
     
         41 . The field emission cathode of  claim 27 , wherein said treatment results in the introduction of metal atoms onto the carbon nanotubes.  
     
     
         42 . The field emission cathode of  claim 27 , wherein said treatment results in the introduction of functional groups onto the carbon nanotubes.  
     
     
         43 . The field emission cathode of  claim 42 , wherein said functional groups have been introduced by chemical sorption.  
     
     
         44 . The field emission cathode of  claim 27 , wherein said treatment comprises heating the carbon nanotubes in the presence of metal vapor.  
     
     
         45 . The field emission cathode of  claim 27 , wherein said treatment comprises chemisorption followed by heat treatment.  
     
     
         46 . The field emission cathode of  claim 27 , wherein said treatment includes  
     
     
         47 . The field emission cathode of  claim 27 , wherein said cathode further includes a binder.  
     
     
         48 . The field emission cathode of  claim 47 , wherein said binder is a conductive carbon paste, a conductive metal paste or a carbonizable polymer.  
     
     
         49 . The field emission cathode of  claim 27 , wherein the nanotubes are deposited onto a substrate.  
     
     
         50 . A method for making a field emission cathode comprising the steps of: 
 dispersing carbon nanotubes into a liquid vehicle to form a solution;    forming an electrophoresis bath, said bath including an anode and a cathode immersed therein;    applying a voltage to said anode and said cathode, thereby causing said carbon nanotubes to deposit onto said cathode;    removing said cathode from said bath; and    subjecting the nanotubes deposited on said cathode to an energy, plasma, chemical, or mechanical treatment.    
     
     
         51 . The method for making a field emission cathode of  claim 50 , wherein said nanotubes are substantially cylindrical carbon fibrils having one or more graphitic layer concentric with their cylindrical axes, said carbon fibrils being substantially free of pyrolytically deposited carbon overcoat, having a substantially uniform diameter between 1 nm and 100 nm and having a length to diameter ratio greater than 5.  
     
     
         52 . The method for making a field emission cathode of  claim 50 , wherein said nanotubes are in the form of aggregates selected from the group consisting of cotton candy aggregates or bird nest aggregates.  
     
     
         53 . The field emission display device of  claim 50 , wherein said nanotubes have a morphology resembling a fishbone.  
     
     
         54 . The method of making a field emission cathode of  claim 50 , wherein said nanotubes are single wall nanotubes. The method of making a field emission cathode of  claim 50 , wherein said nanotubes are in the form of a film or mat.  
     
     
         55 . The method for making a field emission cathode of  claim 50 , wherein said cathode is bombarded with ions.  
     
     
         56 . The method for making a field emission cathode of  claim 50 , wherein said cathode is bombarded with a gallium ions.  
     
     
         57 . The method for making a field emission cathode of  claim 50 , wherein said cathode is bombarded with ions selected from the group consisting of hydrogen, helium, argon, carbon, oxygen, and xenon ions.  
     
     
         58 . The method for making a field emission cathode of  claim 50 , wherein said chemical treatment is selected from the group consisting of acid treatment, metal vapor treatment, chemical vapor transport, and chemical sorption.  
     
     
         59 . The method for making a field emission cathode of  claim 50 , wherein said chemical treatment is performed with chemical reagents selected from the group consisting of oxidizing agents, electrophiles, nucleophiles, reducing agents, strong acids, strong bases and mixtures thereof.  
     
     
         60 . The method for making a field emission cathode of  claim 50 , wherein said chemical treatment is performed with phthalocyanines or porphyrins.  
     
     
         62 . The method for making a field emission cathode of  claim 50 , wherein said energy treatment is performed with an energy source selected from a group consisting of electromagnetic radiation, ionizing radiation, atomic beams, electron beams, ultraviolet light, microwave radiation, gamma ray, x-ray, neutron beam, molecular beams and laser beam.  
     
     
         63 . The method for making a field emission cathode of  claim 50 , wherein said plasma treatment is performed with a plasma selected from a group consisting of oxygen, hydrogen, ammonia, helium, argon, water, nitrogen, ethylene, carbon tetrafluoride, sulfur hexafluoride, perfluoroethylene, fluoroform, difluoro-dichloromethane, bromo-trifluoromethane, chlorotrifluoromethane and mixtures thereof.  
     
     
         64 . The method for making a field emission cathode of  claim 50 , wherein said treatment results in the introduction of metal atoms onto the carbon nanotubes.  
     
     
         65 . The method for making a field emission cathode of  claim 50 , wherein said treatment results in the introduction of functional groups onto the carbon nanotubes.  
     
     
         66 . The method for making a field emission cathode of  claim 65 , wherein said functional groups have been introduced by chemical sorption.  
     
     
         67 . The method for making a field emission cathode of  claim 50 , wherein said treatment comprises heating said cathode in the presence of metal vapor.  
     
     
         68 . The method for making a field emission cathode of  claim 50 , wherein said treatment comprises chemisorption followed by heat treatment.  
     
     
         69 . The method for making a field emission cathode of  claim 50 , wherein said treatment includes annealing said nanotubes.  
     
     
         70 . The method for making a field emission cathode of  claim 50 , further comprising the step of adding a binder to said solution before applying said voltage.  
     
     
         71 . The method for making a field emission cathode of  claim 70 , wherein said binder is a conductive carbon paste, a conductive metal paste or a carbonizable polymer.  
     
     
         72 . A field emission display device comprising: 
 a cathode including carbon nanotubes which have been subjected to energy, plasma, chemical, or mechanical treatment;    an insulating layer on said cathode;    a gate electrode on said insulating layer;    an anode spaced from said cathode, said anode comprising a phosphor layer, an anode conducting layer, and a transparent insulating substrate; and    a power supply.    
     
     
         73 . A method for making a field emission cathode comprising the steps of: 
 screen printing an ink onto a substrate, said ink comprising a carrier liquid and carbon nanotubes in as-made form or which have been subjected to energy, plasma, chemical, or mechanical treatment; and    evaporating said carrier liquid.    
     
     
         74 . A method for making a field emission cathode comprising the steps of: 
 ink jet printing an ink onto a substrate, said ink comprising a carrier liquid and carbon nanotubes which have been in as-made form or which have been subjected to energy, plasma, chemical, or mechanical treatment; and    evaporating said carrier liquid.    
     
     
         75 . A method for making a field emission cathode comprising the steps of: 
 spray painting an ink through a stencil onto a substrate, said ink comprising a carrier liquid and carbon nanotubes which have been subjected to energy, plasma, chemical, or mechanical treatment; and    evaporating said carrier liquid.    
     
     
         76 . A method for making a field emission cathode comprising the steps of: 
 screen printing, ink-jet printing or spray painting an ink onto a substrate, said ink comprising a carrier liquid and carbon nanotubes in as-made form; and subjecting said screen printed nanotubes to an energy, plasma, chemical or mechanical treatment.    
     
     
         77 . A field emission cathode made by the method of  claim 76 .  
     
     
         78 . A field emission display device comprising: 
 a baseplate;    an electron emitter array, said array including carbon nanotubes which have been subjected to energy, plasma, chemical, or mechanical treatment;    a gate on said baseplate;    a phosphor coated faceplate spaced from said gate;    a faceplate on said phosphor coated faceplate; and    a power supply.    
     
     
         79 . A field emission device comprising: 
 a substrate,    a porous top layer on said substrate,    a catalyst material on said layer; and    a cathode on said catalyst material, said cathode including a bundle of carbon nanotubes which have been subjected to energy, plasma, chemical, or mechanical treatment.