The present invention relates to a field emission device comprising an anode and a cathode, wherein said cathode includes carbon nanotubes which have been treated with an ion beam. The ion beam may be any ions, including gallium, hydrogen, helium, argon, carbon, oxygen, and xenon ions. The present invention also relates to a field emission cathode comprising carbon nanotubes, wherein the nanotubes have been treated with an ion beam. 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 treated with an ion beam is further disclosed.