Hafnium carbide films and film-coated field emission cathodes

Abstract

Summary form only given. Uses for field emitter arrays range from video displays to microwave applications. We report here on experiments with physical vapor deposition of HfC and the subsequent electron emission properties of these film surfaces. In previous work, we have reported improvements to field emission turn on voltages and stability with the addition of ZrC to individual prefabricated W and Mo emitters and of field emission arrays of Mo and Si. This work with HfC seems to better the results obtained with ZrC. We have observed high current density field emission, greater than 1/spl times/10/sup 8/ A/cm/sup 2/, from single crystal HfC and ZrC cathodes. These materials have work functions approximately 1 eV lower than W and Mo, making them attractive candidates for low voltage microelectronic field emitter arrays. However, in order to make these materials useful for practical arrays, it is necessary to be able to fabricate many identical field emitters from them. One possible way to achieve this is to deposit carbide films onto arrays fabricated from W, Mo, or Si. The challenge with this approach is the achievement of the desired properties (stability and low work function) in the deposited layers. W and Mo field emitters were individually fabricated and an appropriate quantity of HfC was evaporated onto the emitter surface from a high-purity HfC evaporation source. Several emitters prepared by this method have been tested.