Carbon nanotubes as cold cathodes

Abstract

To communicate, spacecraft and satellites rely on microwave devices, which at present are based on relatively inefficient thermionic electron sources that require heating and cannot be switched on instantaneously. Here we describe a microwave diode that uses a cold-cathode electron source consisting of carbon nanotubes and that operates at high frequency and at high current densities. Because it weighs little, responds instantaneously and has no need of heating, this miniaturized electron source should prove valuable for microwave devices used in telecommunications.

Self-Oscillations in Field Emission Nanowire Mechanical Resonators: A Nanometric dc−ac Conversion

“…9,10 Nanotubes and nanowires are especially useful for FE due to their high aspect ratio that creates a large field at the tip for a relatively low applied voltage. Recently the potential of FE nanosources for high frequency applications has been explored for carbon nanotube microwave diodes 11 of interest in satellite communications, nano-electro mechanical single-electron transistor, 12 and ultra fast pulsed electron sources. 13 We chose a simple single clamped configuration for its versatility, ideal in the exploration of new phenomena in NEMS.…”

Electron beam collimation with a 40 000 tip metallic double-gate field emitter array and in-situ control of nanotip sharpness distribution

“…10 Field emitter arrays (FEAs) with on-chip electron extraction gate electrodes G ext , which combine the electron emission of thousands to millions of nanotips, have been explored for high current generation with a wide variety of materials. 7,[11][12][13][14] To generate high brightness beams with a small transverse electron velocity spread, however, it is crucial to add an on-chip gate electrode G col for the collimation of individual field emission beamlets. These so-called double-gate FEAs have been proposed as high current and high brightness cathodes 15,16 and have been actively studied.…”

“…The extremely high brightness of field emission electron beams has enabled the realization of electron microscopes with single-atom resolution 1 and has stimulated high current and high current density applications such as free-electron lasers 2,3 and THz vacuum electronic devices. [4][5][6][7] Field emitters can produce high brightness electron beams via quantum tunneling by applying a strong electric field in the order of GV/m to solid surfaces. Such fields can be created by a comparatively low potential with the help of the field enhancement at the nanometer-scale tip apexes.…”

Microscopic analysis of performance variations in carbon nanotube field emission cathodes: Implications for device optimization

“…1 Introduction Electron field emission from carbon nanotubes (CNTs) has been intensively investigated for more than 15 years because of its high potential for novel applications such as field emission displays [1], microwave amplifiers [2], or cold cathodes for X-ray tubes [3]. Their intrinsic high aspect ratio, chemical and mechanical stability and electronic properties make CNTs ideal candidates for electron field emitters.…”

“…Two samples were fabricated using a combined DC plasma/thermal chemical vapor deposition (CVD) growth method referred to as ''Black Magic'' (BM) 2 . This process consists in a variant of thermal CVD that includes a 60 s conditioning of the ironbased catalyst stack prior to deposition [14] by a 75 W, 15 kHz rectangular DC pulse ammonia plasma discharge and subsequent CNT growth from an ammonia/acetylene gas mixture.…”