Chiral and quantum size effects of single-wall carbon nanotubes on field emission

The emission current of a single-wall carbon nanotube (SWNT) in field emission is studied by the tunneling theory with the tight-binding approach. The emission current is almost independent of the chiral angle of SWNT in low fields, but increases with increase of chiral angles in very high fields. We found a room-temperature quantum size effect of SWNT on field emission. As the diameters of SWNTs increase, the current densities decrease for metallic tubes, but increase for semiconducting tubes. When the diameters of SWNTs are larger than 2nm the current densities of metallic and semiconducting tubes are very close. These chiral and quantum size effects are originated from the energy band structure of nanotubes.