Mechanisms of field emission from cubic boron nitride coated molybdenum emitters

A combination of classical I-V characterization and voltage-dependent field emission energy distribution (V-FEED) analysis was employed to investigate the mechanisms that dominate field emission from tip-shaped Mo emitters electrophoretically coated with nominally intrinsic, cubic boron nitride (c-BN) powders. I-V characterization of Mo emitters before and after coating showed that the c-BN coating enhanced the field emission current by 2 orders of magnitude. V-FEED analysis revealed a voltage drop proportional to the applied voltage across the c-BN coating due to field penetration. This voltage drop was typically in the order of several Volts for applied voltages of several 100 Volts, and a cathode-to-anode distance of 500 mu m. Extrapolation of V-FEED data to flat band condition identified the conduction band minimum of c-BN as the origin of field emitted electrons. At larger field emission currents, an additional voltage drop was observed and was found to be proportional to the emission current. This observation was interpreted in terms of an ohmic resistance at the Mo/c-BN interface and was estimated to be in the order of 10 M Omega.