Nanodiamond Vacuum Field Emission Integrated Differential Amplifier

The development of a novel vacuum differential amplifier (diff-amp) array employing vertically configured nanodiamond (ND) vacuum field emission transistors (ND-VFETs) on a single chip is presented. The diff-amp array is composed of a common ND emitter array integrated with partition gates and split anodes. An identical pair of ND-VFETs with well-matched field emission transistor characteristics was fabricated by using a dual-mask well-controlled microfabrication process, involving a mold-transfer self-aligned gate-emitter technique in conjunction with ND deposition into the micropatterned molds in the active layer of a silicon-on-insulator substrate followed by gate partitioning to form diff-amp array. The ND-VFETs show gate-controlled modulation of emission with distinct cutoff, linear, and saturation regions. Signal amplification characteristics of the ND-VFET diff-amp are presented. A large common-mode-rejection ratio (CMRR) of 54.6 dB was measured for the diff-amp. The variation of CMRR performance with transconductance was examined, and the results were found to agree with the equivalent circuit model analysis. The accomplishment of this basic circuit building block, consisting of an integrated diff-amp, demonstrates the feasibility of using vacuum integrated circuits for practical applications, including high-radiation and temperature-tolerant space electronics.

I. Introduction

Vacuum field emission (VFE) microelectronics, relying on ballistic electron transport in vacuum, promises for high operation speed, low energy loss, and temperature and radiation immunity performance [1], [2]. Vacuum microelectronic devices are favorable for a variety of applications ranging from sensors and field emission displays to high-performance integrated circuits (ICs). VFE devices possess better noise immunity than solid-state devices and thereby can operate at a much lower current with good noise rejection performance. VFE integrated devices and circuits are good for high-speed and high-power applications and in harsh environments including high temperature and high radiation. In the past, only few practical implementations of VFE devices at circuit level have been reported even though the concepts and modeling of vacuum ICs were described [3], [4]. Improvement in VFE device stability, particularly cathode reliability, is required for the practical implementation of vacuum microelectronic devices in ICs.