Ab initio Study on the Field Emission from Linear Carbon Chains and Carbon Nanotubes

We have performed first-principles calculations on the field emission of linear carbon chains and carbon nanotubes. The three-dimensional character of the current source, as well as the effect of the external electric field, are explicitly considered. The calculated electron-leakage graph is quite linear in short times, giving the tunneling rate from the emitter to the vacuum. The total current from the carbon chain fits the Fowler-Nordheim formula well. The magnitude of the current associated with each electronic state is found to exponentially depend on the energy level. In case of the unpassivated carbon chains, the dangling bond states pointing to the vacuum dominate the total current. We also study the emission currents from curved and tilted carbon nanotubes and find that a significant reduction in the emission current occurs compared with the case of the straight and vertical tubes. Due to its high aspect ratio and the mechanical strength, the carbon nanotube [1] is regarded as a new material for the electron emitters to be used in the field emission display [2] as well as in the coherent electron source [3]. However, the emission mechanism of the nan