Experimental and computational study of field emission characteristics from amorphous carbon single nanotips grown by carbon contamination -: I.: Experiments and computation

Some properties of electron field emitters based on various types of carbon are difficult to measure and are not well known. This is particularly true for amorphous carbon films, for nanotubes and for nanotips grown by carbon contamination in a scanning electron microscope. We show that by combining together experimental data (i.e. emitter geometry from electron microscopy observations, and field emission current and applied voltage measurements), numerically computed values of the electric field at the tip surface and the Fowler-Nordheim (F-N) equation, it is possible to estimate values of parameters such as the work function, the enhancement factor, the tip radius and the effective emitting area. The general applicability of this approach and corresponding results are emphasized. We also show that, when the experimental parameters that are known are superfluous in number (i.e. more than the minimum number needed), a discrepancy exists, firstly, between the value of the emitter radius worked out through the F-N equation and that derived from electron microscopy and, secondly, between the calculated work function and that independently obtained by Kelvin probe microscopy. Possible reasons for these discrepancies are put forward and discussed.