New evidence for localized electronic states on atomically sharp field emitters

We have studied field emission from atomically sharp tungsten-carbide-coated W⟨111⟩ tips, and from atomically sharp HfC⟨100⟩ and ZrC ⟨100⟩tips. We observed multiple-peaked total energy distributions from the apex atoms. These narrow and intense peaks have strong angular anisotropy, and their relative magnitudes depend on the extraction field. They suggest the presence of localized states on the atom at the apex of the tip. © 1996 The American Physical Society.