Effect of morphology on field emission properties of carbon nanocoils and carbon nanotubes

Helical carbon nanocoils exhibit excellent field emission properties, and are thus expected to be applicable as electron emitters in field emission displays. We have synthesized carbon nanocoils with different diameters by the catalytic thermal decomposition of acetylene using iron-indium-tin-oxide catalysts. It is found that the turn-on voltage is decreased by decreasing the average diameter of the grown carbon nanocoils. The turn-on voltage of as low as 30 V at the electrode gap of 130 mu m was achieved when the coil diameter is decreased to 60 nm. The calculation for the concentration of the electric field on the coil surface has been performed using a finite element method. It is found that the strength of the electric field around the top ring of a coil is increased with the decrease of the tubular diameter of the coil and has a similar value as that at the tip of a carbon nanotube, suggesting that the efficiency of the field emission from nanocoils would be higher than that from nanotubes. These results can explain the high stability of field emission from carbon nanocoils.