Photon-stimulated field emission from semiconducting (10,0) and metallic (5,5) carbon nanotubes

Abstract

~Received 30 October 2001; published 2 May 2002! We present three-dimensional simulations of field emission through an oscillating barrier from ideally open ~10,0! and ~5,5! carbon nanotubes without adsorption, by using a transfer-matrix methodology. By introducing pseudopotentials for the representation of carbon atoms and by repeating periodically a basic unit of the nanotube, band-structure effects are manifested in the energy distributions. The total-energy distributions also exhibit oscillations, which are related to stationary waves in the structure. The current enhancement due to the photon-stimulation process reaches a saturation plateau for photon energies larger than 5 eV and decreases when the photon energy exceeds 9 eV. The results indicate a maximal current enhancement at a photon energy of 8.4 eV. This maximum may correspond to the best compromise between increasing width of the energy distribution and decreasing efficiency of the photon stimulation. In addition, a resonant photon-stimulation process seems associated with the maximum. For a power flux density of 5.96 310 12 W/m 2 and a local field of 2.5 V/nm, a relative current enhancement up to 10 9 is achieved with the semiconducting ~10,0! nanotube while it is only of 140% for the metallic ~5,5!, this large difference being explained by the semiconducting ~10,0! nanotube having an intrinsic emission ~without photonic stimulation! 5310 8 times lower than that of the metallic ~5,5!. These results indicate that photon-stimulated field emission from semiconducting carbon nanotubes may lead to important technological applications, like THz amplifiers ~if a femtosecond modulation of the radiation can be achieved!.