Fabrication and Behavior of Diamond Field Emitter Triode Utilizing

Silicon-on-Insulator (SOI) MEMS Technology and CVD Diamond

W. P. Kang, A. Wisitsora-at, and J. L. Davidson

Dept. of Electrical and Computer Engineering, Vanderbilt Univ., Nashville, TN 37235

D. V. Kerns

Olin College of Engineering, 1735 Great Plain Avenue, Needham, MA 02492-1245

ABSTRACT

This paper reports a new fabrication approach that utilizes silicon-on-insulator (SOI) micro-electro-mechanical-system (MEMS) processing technology and chemical-vapor-deposition (CVD) diamond to achieve totally monolithic diamond field emitter devices. The approach allows the core structure of field emitter device such as the gate, anode, field emitter geometry, emitter array configuration and the final physical location of the diamond cathode to be designed on the SOI wafer where precise self-alignment of diamond field emitter structures can be achieved on an integral substrate. Moreover, this technique allows the fabrication of high-density gated diamond field emitter arrays with precise uniformity and planarity over a large area. A uniform array with millions of gated diamond micro-emitters per cm² can be reproducibly achieved. Preliminary results in triode configuration demonstrate excellent transistor characteristics for vacuum microelectronic applications. The emission characteristics in triode configuration indicate that there are the three distinct regions associated with transistor operation: the cutoff region, the linear region, and the saturation region. The saturation region can be used if the diamond field emitter triode is to operate as an amplifier. For operation as a switch, the cutoff and linear regions are utilized. The triode is in cutoff mode when gate voltage, V_g is less than the threshold voltage, V_t, where V_t is the minimum gate voltage needed to start the electron emission. The diamond field emitter array, tested in triode configuration, has a low turn-on gate voltage of 10 V and high emission current of 1mA/tip. The diamond vacuum transistor shows a high voltage gain of 250 and good transconductance behavior. The device performances are considerably better than comparable metal and silicon field emitter triodes, which typically have turn-on gate voltage higher than 80 V at gate-cathode spacing of 1 mm, lower voltage gain and transconductance.

Keywords: diamond, vacuum microelectronics

corresponding author

W. P. Kang, PhD.

Associate Professor, Electrical and Computer Engineering

Vanderbilt School of Engineering

Box 1661-B

Vanderbilt University

Nashville, TN 37235

Phone: (615) 322-0952       fax: (615) 343-6614

wkang@vuse.vanderbilt.edu