Oxide Electron Emitters: Thermionic Emission from Yttrium Oxide

We report an unexpectedly narrow energy distribution for thermal electron emission from yttrium oxide. Given the wide band gap of the material, electron transport and the observed excellent emission properties are puzzling. We present density functional theory simulations and explain the emission behavior based on the role of oxygen vacancies, which introduce narrow energy levels that may act as spatially localized electron emission sites. This approach may also help in understanding the working mechanism of other oxide cathodes.