N. N. Petukhova

Aluminum doping of poly(vinylidene fluoride with trifluoroethylene) copolymer

The interface between aluminum and crystalline copolymer thin film of vinylidene fluoride (70%) with trifluoroethylene (30%) [PVDF-TrFE] has been studied. The ratio of carbon 1s and aluminum 2p core level photoemission peak intensities changes little with increasing emission angle after deposition of 5 A aluminum on the surface of PVDF-TrFE. This indicates that the distribution of aluminum atoms in the copolymer film is quite uniform in the near surface region and that the interface between PVDF-TrFE and aluminum is not abrupt. There is evidence for changes in photohole screening with aluminum doping within the polymer film.

Comparison of aluminum and sodium doped poly(vinylidene fluoride-trifluoroethylene) copolymers by x-ray photoemission spectroscopy

The chemical interaction between the simple metals, aluminum and sodium, and crystalline copolymer thin films of vinylidene fluoride (70%) with trifluoroethylene (30%), has been studied using x-ray photoemission spectroscopy. Aluminum and sodium metalize the polymer differently and different binding sites for the two metals can be inferred from the corresponding core level shifts. Aluminum leads to enhanced screening of final photoemission states associated with the polymer, while sodium doping strongly influences the fluorine, but perturbs the carbon backbone only slightly.

Measurement of landau coefficients in ferroelectrics using nonlinear dielectric spectroscopy

A method of measuring the phenomenological Landau-Ginzburg coefficients in an expansion of the free energy of ferroelectrics near the phase transition is proposed. This method is based on simultaneously recording five Fourier components of the current response to a sinusoidal voltage as a function of temperature. An analysis is made of a specific application of the method to Langmuir-Blodgett ultrathin ferroelectric films.

Ferroelectric phase transition in Langmuir-Blodgett films of copper phthalocyanine

A ferroelectric phase transition is observed in Langmuir-Blodgett films prepared from substituted copper phthalocyanine molecules. The linear and nonlinear dielectric properties of the films and the switching of their spontaneous polarization are investigated in the temperature range of the phase transition. The observed features can be explained by the Landau-Ginzburg model of a first-order phase transition.