Carbon nanotubes exhibit extraordinary field emission properties because of their high electrical conductivity, ideal high aspect ratio whisker-like shape for geometrical field enhancement, and remarkable thermal stability. This paper will describe the PECVD growth of vertically aligned arrays of carbon nanotubes which are suitable for use as the electron emitters in a novel type of microwave amplifier capable of producing of order 10 W at 30 GHz. (C) 2004 Elsevier B.V. All rights reserved.