Electric-Field-Induced Polarization Enhancement of Vinylidene Fluoride/Trifluoroethylene Copolymer Ultrathin Films

We investigated the polarization enhancement in 60-nm-thick vinylidene fluoride/trifluoroethylene (VDF/TrFE) films without thermal annealing by applying repeated bipolar electric pulses The remnant polarization was 8.4 mC/m(2) in as-spin-coated films and increased to up to 45 mC/m(2) when 105 pulses were applied. Although the remnant polarization was half and the coercive field twice those of annealed films, the electrically treated film had a markedly smoother surface than the annealed film Finally, a 15-nm-thick ferroelectric VDF/TrFE film with low conductivity was fabricated by electric treatment; annealed films with the same thickness experienced a severe short-circuit problem originating from the surface roughness. (C) 2011 The Japan society of Applied Physics