DIAMOND EMITTERS FABRICATION AND THEORY

The fabrication of gated diamond field-emission cathodes is described and a theory of their operation is discussed. These cathodes are made using commercial diamond grit with the addition of Ni and Ca salts to enhance emission. The resulting structure resembles a field-emission S pindt cathode with the internal metal cone replaced by a similar to 10 0 nm layer of diamond grit. Emission from these cathodes occurs at the lowest reported gate voltage of any field emission device and is unaf fected by operation at pressures of over 100 Pa of N-2. Operation in o xygen and H2S at pressures of 6x10(-4) Pa degrades emission, but the c athodes recover once the ambient pressure is reduced to below 1x10(-4) Pa. The emission current noise is 2.5% rms over an 8 h period and 1% rms over 3 ms. These cathodes suffer from high gate current that varie s from 0.2 to 1000 times the emitted current. The high gate current is known to be process dependent and not inherent to the cathodes. The e mission performance is explained by the stable negative electron affin ity of diamond, which allows for injection of electrons from diamond i nto vacuum with little to no electric field, 0-1 V mu(-1). Cathode ope ration is limited by the injection of electrons into the diamond at th e back metal-diamond interface, which depends upon the doping of the d iamond and the roughness of that interface. (C) 1996 American Vacuum S ociety.