Novel geometry of carbon nanotube field emitter to achieve high current densities

Abstract

One area which has generated much interest for potential use of CNT cold field emitters involves devices operating in the terahertz (THz) regime of the electromagnetic spectrum. The potential applications in astronomy, biology, medical imaging, and communications continue to motivate research in THz technology [1,2]. Viable THz sources such as backward wave oscillators (BWOs), gyrotrons, and free electron lasers (FELs) require current densities ranging from tens of milliamps to several amps. Presently, available sources rely on thermionic emitters, and thus they are prone to slow switching speeds and high power consumption. In addition, thermionic electron emitters also tend to degrade due to chemical contamination and/or sputter erosion leading to emission instability. Carbon nanotubes (CNTs) are highly attractive materials for use as cold field emitters because they have exceptional intrinsic properties such as high aspect ratio, good chemical stability, high mechanical strength, and thermal conductivity [3,4]. These attributes enable CNT cold field emitters (CNTFE) to exhibit long lifetime and high current densities at low turn-on fields [3,5].