Field emission measurements with μm resolution on chemical‐vapor‐deposited polycrystalline diamond films

The distribution of field emitting sites on polycrystalline diamond films at electrical surface fields has been investigated between 2.5 and 150 MV/m by means of a field emission scanning microscope with μm resolution. For the first time field emission scans were performed on broad‐area (≊cm2) diamond cathodes with in situ scanning electron microscope analysis of the localized sites. The 2–3‐μm‐thick diamond films were chemical‐vapor deposited on Mo substrates by the hot‐filament technique. Undoped and p‐type boron‐doped films with low content of sp2‐bonded carbons were studied. The highest emitter density of ∼2000/cm2 at 100 MV/m was detected on undoped diamond surfaces. A preliminary study of localized emitters indicated both sporadic particles of foreign materials at the emitting sites as well as intrinsic emission from diamond. In addition, the Fowler–Nordheim parameters β and S, the elemental composition, and the current stability of localized emitters were measured.