Negative Electron Affinity and Low Work Function Surface: Cesium on Oxygenated Diamond (100)

Building on analogies with low work function metal surfaces, an oxygenated C(100) surface cesiated at the half-monolayer level has been studied with self-consistent local-density-based methods. Cesiation of the surface is found to shift the 2.45 eV positive electron affinity oxygenated surface to a surface with the bulk diamond conduction band 0.85 eV above the vacuum level, in effect a 0.85 eV negative electron affinity (NEA). The resulting surface is in fact metallic due to Cs-O-C surface states and thereby also provides a low work function Φ=1.25 eV. The combination of NEA bulk material with metallic low-Φ surface promotes noncharging electron emission that makes it promising for novel diamond-based optoelectronic devices.