First-principles calculations of field emission from nano-structures

A simple yet accurate self-consistent method using the density functional formalism is introduced to study the field emission properties of the nano-structures including the nanographitic armchair ribbons and the Fe bilayer on W(001) surface. The field emission currents from the armchair ribbons are dominated by the contribution from off-zone-center states because of specific wavefunction symmetries, and there exists an anomalous current density dependence on the inter-ribbons separation due to edge dipole effects. The high minority-spin-polarization of the field emission current from the Fe bilayer on W(001) surface is found, and is due to that the emission current with majority-spin is from the W substrate states but the current with minority-spin is mainly contributed by the quantum well states localized in the Fe bilayer. These rather novel properties should be ascribed to the special electronic structures of these two nano-structures.