9.5: Resonant tunneling and extreme brightness from diamond field emitters and carbon nanotubes

We report new results from field emission microscopy studies of multi-wall carbon nanotubes and from energy-spectrum measurements of beams from diamond field emitters. In both systems, we find that resonant tunneling through adsorbed species on the emitter surface is an important and sometimes dominant effect. For diamond emitters our observations include order of magnitude emission enhancement without spectral broadening, complex spectral structure, and sensitivity of that structure to the applied electric field. For carbon nanotubes we have observed electron beams from individual adsorbates which approach the maximum beam brightness allowed by Pauli exclusion.