Effects of electric field on the molecular orientation in evaporated ferroelectric vinylidene fluoride and trifluoroethylene copolymer films

An electric field was applied during the evaporation process to obtain ferroelectric polymeric ultrathin films with uniaxial dipole orientation. The crystal structure and molecular orientation in the evaporated (VDF/TrFE) copolymer films were examined with a recently developed total reflection X-ray diffractometry, revealing that polar Form I crystals with the dipole moment oriented normal to the substrate can be formed by evaporating the samples under a high electric field (6 MV/m). Moreover, we evaluated the ferroelectric-paraelectric phase transition behavior of the evaporated films from a structural viewpoint.