Enhanced low-temperature thermionic field emission from surface-treated N-doped diamond films

Abstract

Nitrogen-doped diamond films have been synthesized for application as a low-temperature thermionic field-emission cathode. The critical result of this study is the observation of uniform electron emission from UV photo-excitation and from thermionic field emission for films terminated with hydrogen or a 0.3-nm Ti layer. The samples were imaged with photoelectron emission microscopy (PEEM) and thermionic field-emission electron microscopy (T-FEEM) at temperatures up to 900 °C, and the electron emission current was recorded vs. the applied voltage. Hydrogen-passivated films show enhanced electron emission, but become unstable at elevated temperatures, while Ti-terminated films showed similar enhanced emission at temperatures up to 950 °C. Temperature-dependent I/V measurements show strongly increased electron emission at higher temperatures, suggesting that electron emission originates from the conduction band. These results indicate a promising new material for the production of low-temperature, high-brightness electron sources.