Estimation of emission field and emission site of boron-doped diamond thin-film field emitters

The electric field required to emit electrons for boron-doped diamond together with the emission site was estimated using measurement systems that can precisely control the emitter-collector gap and lateral position. Three different types of field emitters were prepared by microwave plasma chemical vapor deposition. Type A was a typical diamond film on a flat silicon substrate, type B was a heteroepitaxial diamond film that was deposited on a (111) oriented platinum substrate, and type C was a pyramidal diamond film fabricated by the transfer mold method. For all the emitters, the voltage required to extract 0.2 nA was measured as a function of the emitter-collector gap, where the device of the emitter-collector configuration is approximated by a pair of parallel plates. The results showed that a strong electric field was applied in front of the emitter. For type B, the emission current distribution was measured by a device in which the collector was an etched needle. It was found that the emission current was concentrated at some points, which would be the crystallite edge, and also that, even at a flat crystal facet, electrons were emitted by applying a similar electric field. A similar result was obtained for type C emitters. This study revealed that the electron can be emitted from any position on the film, but generally the crystallite edge is the most probable emission site due to the concentration of a high electric field there compared to other places on the film. (C) 2000 American Vacuum Society. [S0734-211X(00)03402-8].