HIGH-ELECTRIC-FIELD CONDUCTION MECHANISMS IN ELECTRODE POLING OF ELECTROOPTIC 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 simultan eously in poling experiments performed on samples with and without an additional inorganic poly-methyl-siloxane layer. Current densities app eared to be limited by a Schottky-type potential barrier at the electr ode/insulator interface, The field dependence of the current density w as 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 Fowl er-Nordheim tunneling at higher poling fields. In the presence of the siloxane layer, a significant suppression of tunneling current was obs erved, This leads to a reduced probability of singular dielectric brea kdown events and shifts the limit Of avalanche breakdown to higher int ernal effective poling field strengths. (C) 1996 American Institute of Physics.