We present three-dimensional simulations of field emission through an oscillating barrier from an. ideal open (10,0) carbon nanotube without adsorption by using a transfer-matrix methodology. By introducing pseudopotentials for the representations of carbon atoms and by repeating periodically a basic unit of the nanotube, band-structure effects are manifested in the distributions of energies. The total-energy distribution of the emitted electrons present features which are related essentially to the gap of the semiconducting (10,0) nanotube and to stationary waves in the structure. The current enhancement due to photon-stimulation reaches a saturation plateau for photon energies larger than 5 eV and decreases for high energies. Maximal enhancement is achieved at a photon energy around 8 eV, one electron being then emitted for every 20 photons crossing the nanotube. (C) 2003 American Vacuum Society.