EHD-enhanced, space-charge-limited currents in insulating liquids

Abstract

Transient space charge limited (SCL) currents, enhanced by electrohydrodynamic (EHD) convection, have been studied using an electron beam as an injecting contact. A primary beam injects a uniform current into the free surface of the liquid film, and a second beam which is directed across the liquid surface monitors the surface potential of the sample. At low current densities the charging and discharging characteristics of the liquid follows the constant-mobility SCL equation. At higher currents, above the EHD instability onset, the surface potential in the turn-on transient exhibits a characteristic peak as the electroconvection builds up in amplitude; the liquid then settles down to a steady, enhanced-mobility SCL current. When the current is turned off the decay of surface potential is characterized at first by an enhanced mobility, and then as convection dies away the discharge merges into the constant mobility case.