Diamond vacuum field emission devices

Abstract

Diamond for field emission has attracted considerable attention in vacuum microelectronics due to its low electron affinity for electron emission, hardness to withstand ion bombardment, and good thermal and electrical conductivity to handle high current. We have developed multiple processes to micro-pattern diamond films by mold transferring technique and achieve topologically managed diamond field emitters that optimize both the geometrical and quantum aspects of the Fowler–Nordheim governed emission. In this paper, we report the development of (a) vertical and (b) lateral diamond field emission devices. Vertically self-aligned gated diamond vacuum triodes were fabricated on a silicon-on-insulator (SOI) mold. This fabrication technique utilizes conventional silicon micro patterning and etching techniques to define the anode, gate, and cathode. The fabrication has achieved diamond field emitter triodes over practical wafer areas. The field emission of the triode array exhibits transistor characteristics with high d.c. voltage gain ∼800 and good transconductance. Also, lateral diamond vacuum diodes were fabricated with a diamond patterning technique utilizing an oxide mask and lift-off. An anode–cathode spacing of less than 2 μm between the diamond anode and cathode was achieved. The lateral diode exhibits a low turn-on voltage of ∼5 V (field approx. 3 V/μm) and a high emission current of 6 μA, from four diamond cathode ‘fingers’ configuration.