Stable field emission has been obtained in inert gas under atmospheric pressure with 100 nm characteristic size. An individual multiwalled carbon nanotube (MWCNT) mounted on an atomic force microscopy tip acted as the cathode. The field emitter could provide current of up to 1 mu A with fluctuation lower than 6%. This MWCNT was then coated with HfC to further improve its field emission current by about four times and reduce the fluctuation to 2%. With the protection of HfC, the field emitter has a high stability under atmospheric pressure inert gas; even increasing the characteristic size to 200 nm does not affect the stability. These results, combined with the state-of-the-art fabrication technology, could help create nanoscale field emission devices. (C) 2010 American Vacuum Society. [DOI: 10.1116/1.3372333]