N. Petukhova

Ferroelectric Langmuir-Blodgett films

Abstract The ferroelectric Langmuir-Blodgett films are prepared and investigated for the first time The films are prepared from the ferroelectric copolymer of vinylidene fluoride with trifluorethylene The films with the thickness off 150 A show the pyroelectric effect being measured along the polar C-axis perpendicular to the substrate surface, partial remnant polarization switching and ferroelectric phase transition of the first order, characterized by the temperature hysteresis

Piezoelectric and pyroelectric properties of ferroelectric Langmuir-Blodgett polymer films

The piezoelectric and pyroelectric responses of ferroelectric Langmuir–Blodgett polymer films are less than the largest values measured with bulk films of the same composition. The films of the crystalline copolymer poly(vinylidene fluoride trifluoroethylene) fabricated by the Langmuir–Blodgett technique are 30 ML thick (15 nm) and are highly crystalline and oriented with polarization perpendicular to the film. Both piezoelectric and pyroelectric measurements show reversible ferroelectric switching. The films are suitable for use in pyroelectric infrared imaging and in piezoelectric acoustic transducers.

Novel switching phenomena in ferroelectric Langmuir-Blodgett films

We have established ferroelectric switching and observed a novel conductance switching phenomenon in ferroelectric polymer films fabricated by the Langmuir–Blodgett technique. The films consist of 10–30 monolayers (ML) of a copolymer of vinylidene fluoride (70%) and trifluoroethylene (30%), exhibiting a first‐order ferroelectric phase transition at 70 °C and nearly rectangular ferroelectric and conductance hysteresis at 24 °C. Ferroelectric switching is accompanied by switching of the conductance by three orders of magnitude. A model describing this switching phenomenon is proposed.

Lattice and electronic band structure changes across the surface ferroelectric transition

Abstract The origin of the surface ferroelectric phase transition in crystalline copolymer films of vinylidene fluoride (70%) with trifluoroethylene (30%) is explored. We report a uniaxial doubling of the surface Brillouin zone in the conduction band dispersion across the surface ferroelectric phase transition. The temperature dependent changes in the electronic structure occur primarily in the conduction band and are accompanied by a surface dipole reorientation.

Influence of dynamical scattering in crystalline poly(vinylidene fluoride-trifluoroethylene) copolymers

The effective Debye temperature of poly(vinylidene fluoride-trifluoroethylene) copolymers was measured using photoemission and neutron diffraction techniques. An effective Debye temperature of 53±11 K is obtained from the photoemission data and 69±3.5 K from neutron diffraction measurements. This effective Debye temperature is a consequence of the temperature-dependent dynamic motions perpendicular to the surface of these crystalline polymer films.

Ferroelectric langmuir-blodgett films

Abstract Ferroelectric Langmuir-Blodgett films are prepared and investigated for the first time. The films are prepared from the ferroelectric copolymer of vinylidene fluoride with trifluorethylene. Films with a thickness of 150A show a pyroelectric effect, remnant polarization switching and a ferroelectric phase transition of the first order, characterized by temperature hysteresis.

Ultrathin ferroelectric polymer films

Abstract We have established ferroelectric switching and observed a novel conductance switching phenomenon in the first ultrathin ferroelectric polymer films fabricated by the Langmuir-Blodgett technique. The films consist of up to thirty monolayers of a copolymer of vinylidene fluoride (70%) and trifluoroethylene (30%) and exhibit classic ferroelectric behavior, including a first-order ferroelectric phase transition, polarization reversal (switching), thermal hysteresis of the capacitance, field-dependent switching dynamics, pyroelectricity, and piezoelectricity. The results of polarization, capacitance, switching, spectroscopic, and pyroelectric measurements on these highly crystalline and fully oriented films provide unprecedented detail concerning the thermodynamic properties of the ferroelectric and nonferroelectric states in ultrathin polymer films. The electric field and the film thickness have a strong influence on the ferroelectric properties.