FIELD-EMISSION ENERGY-DISTRIBUTION ANALYSIS OF WIDE-BAND-GAP FIELD EMITTERS

Field emission from diamond and cubic boron nitride coated emitters ha s been investigated by field emission energy distribution (FEED) analy sis. In order to study the mechanisms governing the emission process, we developed a modified FEED technique that consisted of measuring ele ctron energy spectra as a function of the extraction voltage applied t o the field emitter. This technique has led to a detailed study of ban d bending effects due to field penetration. Voltage drop across the em itting, wide-band-gap layers (thickness typ. 0.5 mu m) was in the orde r of 1% of the applied extraction voltage. The observed FEED spectra a nd their dependence on the extraction voltage were explained in terms of a simplified band model. In nominally undoped diamond and cubic bor on nitride samples, field emission was found to originate from the con duction band minimum. Injection of electrons from the metallic back co ntact into the wide-band-gap material has been identified as the essen tial limiting factor to the emission current. Mo2C interlayers between Mo back contacts and emitting diamond layers were formed by annealing at 500 degrees C for several hours and led to more emission currents, typically enhanced by more than one order of magnitude. (C) 1998 Amer ican Vacuum Society. [S0734-211X(98)04302-9].