Enhanced correlated-Charge Field Emission

Abstract : We have studied the harmonic content of current generated by a field emitter in order to determine if there is spatial or temporal coherence between the electrons. Harmonic content was observed to be identical and high (2nd harmonic/fundamental < 0.45) for both high rates (16,000 events/sec) and low rates (15 events/sec). Statistical analysis shows harmonic content cannot be attributed to the counting system response, but must be considered as true events in which multiple electrons arrive at the detector. Using a single emitted, we compared the spatial distribution of the thermal emission (TE) with that of the field emission (FE). The two profiles were identical; hence, the TE and FE sources were at the same location. Thus multiple electron emission spectra were not a result of parasitic secondary electron emission from intermediate electrodes or other surfaces. We examined the harmonic content by expanding the beam relative to the detector size. The harmonic content was larger than what one would expect if the spatial distribution of the electrons was entirely random, but not big enough to show spatial coherence. We analyzed charge confinement by van der Waals forces which showed that only large numbers of charges can be spatially correlated. Contamination of the FE surface by absorption is suggested as the origin of the multiple-electron emission.