Work functions for a HV cathode in nonpolar liquids

When negative HV is applied to a needle of small radius of curvature (r/sub p/<0.2 /spl mu/m) in nonpolar liquids, a detectable field emission current (I>/spl times/10/sup -12/ A) is observed above a voltage U/sub FN/, the Fowler-Nordheim law. For larger point radii, only a regular current pulse regime is detected above a threshold voltage U/sub s/ (Trichel regime). Analysis of these voltages U/sub s/ and U/sub FN/ as a function of conduction band energy V/sub 0/ of different liquids, shows that the apparent work function for high electric field strengths in liquids is lower than the one without applied field (2.1 compared to 4.5 eV for a tungsten cathode). This difference can be explained if one assumes the existence of a plasma-like layer around the HV cathode.<
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