The use of internal field emission to inject electronic charge carriers into the conduction band of diamond films: a review

Several thin film composite metal(semiconductor) diamond cold cathode sources have recently been fabricated exhibiting high current-low power characteristics. We have modeled the field emission in these thin film diamond electron sources as a three-step process (electron injection, transport and vacuum emission). Critical to the operation of these devices is a mechanism for populating the conduction band (CB) of diamond with charge carriers. Internal field emission has been proposed for the injection of electrons by tunneling from metal (semiconductor) substrates into the diamond CB. A thin (Schottky) tunneling barrier is created at the substrate-diamond interface by heavily doping the diamond with nitrogen and roughening the metal (semiconductor) interface to enhance the internal field. In this paper we review model calculations of the internal field emission process for both metal and semiconductor substrates. The results show good agreement with experiment, implying the usefulness of the internal field emission mechanism to provide electronic charge carriers in the CB of diamond films. (C) 1999 Elsevier Science B.V. All rights reserved.