High electric field conduction mechanisms in electrode poling of electro-optic polymers

We investigated electrical conduction phenomena, which occurred during high electric field electrode poling of side chain chi((2)) polymers. Electric current and second harmonic intensity were measured simultaneously in poling experiments performed on samples with and without an additional inorganic poly-methyl-siloxane layer. Current densities appeared to be limited by a Schottky-type potential barrier at the electrode/insulator interface, The field dependence of the current density was found to be Schottky charge emission for medium field strengths (E(POL)less than or equal to 100 V/mu m) whereas it was dominated by Fowler-Nordheim tunneling at higher poling fields. In the presence of the siloxane layer, a significant suppression of tunneling current was observed, This leads to a reduced probability of singular dielectric breakdown events and shifts the limit Of avalanche breakdown to higher internal effective poling field strengths. (C) 1996 American Institute of Physics.