Electrophoretic deposition method for a field emission device

Abstract

The invention provides an electrophoretic deposition method of CNTs for a field emission device. It uses a triode structure having gates and a proper arrangement of applied voltages to improve the selectivity of the conventional EPD method. The electric field around the gates repels the charged or polarized nanostructure suspension in the electrophoresis bath and prevents the charged or polarized nanostructure materials from depositing in the neighborhood of the gates. Therefore, the nanostructure materials are selectively deposited on the cathode. An electrical short circuit between the gates and the cathodes can be avoided. It does not require a masked sacrificial layer, and therefore keeps the manufacturing process simple and the cost down.

1 . An electrophoretic deposition method for a field emission device, comprising the steps of: 
 (a) preparing an electrophoresis bath containing nanostructure suspension;    (b) preparing a field emitter plate with a triode structure having gates, wherein said field emitter plate acts as a cathode plate and comprises a substrate, plural cathodes on said substrate, a dielectric film on said substrate and said cathodes, and plural gates on said dielectric film and said substrate;    (c) immersing an anode plate and said field emitter plate in said electrophoresis bath; and    (d) applying two different bias voltages from one or more power supplies for a period of time to said gates and said cathodes, respectively, to selectively deposit nanostructure materials on the surfaces of said cathodes exposed through gate holes of said dielectric film, wherein said anode plate is electrically connected to a common terminal of said power supplies.    
   
   
       2 . The electrophoretic deposition method for a field emission device as claimed in  claim 1 , wherein said power supplies are direct current power supplies.  
   
   
       3 . The electrophoretic deposition method for a field emission device as claimed in  claim 1;  wherein said power supplies are alternating current power supplies.  
   
   
       4 . The electrophoretic deposition method for a field emission device as claimed in  claim 1 , wherein a positive voltage is applied to said gates and a negative voltage is applied to said cathodes while said anode plate is kept at a common voltage.  
   
   
       5 . The electrophoretic deposition method for a field emission device as claimed in  claim 1 , wherein said nanostructure materials include nanotubes, nanowires, nanoparticles, carbon nanotubes, carbon nanowires, and carbon nanoparticles.  
   
   
       6 . The electrophoretic deposition method for a field emission device as claimed in  claim 1 , wherein said field emission device is used as an electron emitter for field emission displays.  
   
   
       7 . The electrophoretic deposition method for a field emission device as claimed in  claim 1 , wherein said anode plate is made of a mesh structure in order to homogenize the electrical field distribution.  
   
   
       8 . The electrophoretic deposition method for a field emission device as claimed in  claim 1 , wherein said cathode plate is a cross-type cathode plate.  
   
   
       9 . The electrophoretic deposition method for a field emission device as claimed in  claim 1 , wherein said cathode plate is a parallel-type cathode plate.  
   
   
       10 . An electrophoretic deposition method for a field emission device, comprising the steps of: 
 (a) preparing an electrophoresis bath containing nanostructure suspension;    (b) preparing a field emitter plate with a triode structure having gates, wherein said field emitter plate acts as a cathode plate and comprises a substrate, plural cathodes on said substrate, a dielectric film on said substrate and said cathodes, and plural gates on said dielectric film and said substrate;    (c) immersing said field emitter plate in said electrophoresis bath; and    (d) applying a bias voltage from a power supply between said gates and said cathodes for a period of time to selectively deposit nanostructure materials on the surfaces of said cathodes exposed through gate holes of said dielectric film.    
   
   
       11 . The electrophoretic deposition method for a field emission device as claimed in  claim 10 , wherein said power supplies are direct current power supplies.  
   
   
       12 . The electrophoretic deposition method for a field emission device as claimed in  claim 10 , wherein said power supplies are alternating current power supplies.  
   
   
       13 . The electrophoretic deposition method for a field emission device as claimed in  claim 10 , wherein a negative voltage is applied to said cathodes with respect to said gates.  
   
   
       14 . The electrophoretic deposition method for a field emission device as claimed in  claim 10 , wherein said nanostructure materials comprise nanotubes, nanowires, nanoparticles, carbon nanotubes, carbon nanowires, and carbon nanoparticles.  
   
   
       15 . The electrophoretic deposition method for a field emission device as claimed in  claim 10 , wherein said field emission device is used as an electron emitter for field emission displays.  
   
   
       16 . The electrophoretic deposition for a field emission device as claimed in  claim 10 , wherein said cathode plate is a cross-type cathode plate.  
   
   
       17 . The electrophoretic deposition method for a field emission device as claimed in  claim 10 , wherein said cathode plate is a cross-type cathode plate.