Total energy distribution of field-emitted electrons from Al(100) surface with single-atom terminated protrusion

We have analyzed field electron emission from Al(100) surfaces with a single-atom terminated protrusion on the basis of the density functional theory combined with real space scattering theory. We have obtained multiple peaks in total energy distribution of emission current from such a pure-metallic protrusion. Furthermore, we have also found that multiple peaks become pronounced as the size of a protrusion becomes larger, which explains the discrepancy among experiments. All the above results can be understood from two factors, the existence of localized states at the topmost Al atom and the potential barrier reduction in front of the topmost atom.