Field electron emission induced glow discharge in a nanodiamond vacuum diode.

The present paper extends the prior findings on self-induced heating of solid state field emission devices. It was found that a vacuum diode (base pressure  ∼10⁻⁹ Torr), that makes use of graphite-rich polycrystalline diamond as cathode material, can switch from a diode regime to a resistor regime to a glow discharge plasma regime without any external perturbation, i.e. all transitions are self-induced. Combined results of in situ field emission microscopy, ex situ electron microscopy and Raman spectroscopy suggest that it is the nanodiamond cathode of the diode heated to about 3000 K which causes self-induced material evaporation, ionization and eventually micro-plasma formation. Our results confirm that field emission, commonly called cold emission, is a very complex phenomenon that can cause severe thermal load. Thermal load and material runaway could be the major factors causing vacuum diode deterioration, i.e. progressive increase in turn-on field, decrease in field enhancement factor, and eventual failure. [ABSTRACT FROM AUTHOR]