This letter reports, diamond field emitters, Cs treated, air stable, that emit electrons at the lowest reported field, <0.2 V μm−1. Field emission from B‐, Li‐, P‐, and N‐doped diamonds and carbonized polymer was characterized as a function of surface treatment. A treated with an O2 plasma, coated with Cs, heated, and exposed to O2 exhibited increased emission for all samples except for B‐doped diamond. The best emission was obtained from N‐doped diamond samples, followed by carbonized polymer, the Li‐doped, and polycrystalline P‐doped diamond. Li‐ and N‐doped samples treated with Cs were stable in laboratory air for several days. This stability of the surface‐activated diamond is believed to be due to the formation of a diamond–O–Cs salt. If the sample is treated with a H2 plasma instead of an O2 plasma, the Cs‐enhanced emission degrades with heat and exposure to O2. Subbands formed by Li and N impurities are believed to be responsible for this enhanced emission. The surface treatment on N‐doped diamond results in emission at fields as low as 0.2 V μm−1. © 1995 American Institute of Physics.