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Full-Text Articles in Physics
Magnetoelectric Effects In Ferromagnetic Cobalt/Ferroelectric Copolymer Multilayer Films, Abhijit Mardana, Mengjun Bai, A. Baruth, Stephen Ducharme, Shireen Adenwalla
Magnetoelectric Effects In Ferromagnetic Cobalt/Ferroelectric Copolymer Multilayer Films, Abhijit Mardana, Mengjun Bai, A. Baruth, Stephen Ducharme, Shireen Adenwalla
Stephen Ducharme Publications
Interactions between a ferromagnet, cobalt, and a ferroelectric copolymer, poly(vinylidene fluoride with trifluoroethylene) in thin film heterostructures result in a 5% change in the ferroelectric polarization on application of a perpendicular 6 kG magnetic field corresponding to a magnetoelectric coupling coefficient of α =5.45 V/cm Oe. The effect disappears on magnetic saturation, ruling out conventional strain coupling. A simple model posits that the ferroelectric film develops in-plane strain gradients, a consequence of the coupling to strain gradients present at the domain walls in the multidomain Co layer, resulting in the measured polarization change via the flexoelectric effect.
Investigation Of State Retention In Metal–Ferroelectric–Insulator–Semiconductor Structures Based On Langmuir–Blodgett Copolymer Films, Timothy J. Reece, A. Gerber, Institut Für Festkörperforschung, Forschungszentrum Jülich, Germany, Stephen Ducharme
Investigation Of State Retention In Metal–Ferroelectric–Insulator–Semiconductor Structures Based On Langmuir–Blodgett Copolymer Films, Timothy J. Reece, A. Gerber, Institut Für Festkörperforschung, Forschungszentrum Jülich, Germany, Stephen Ducharme
Stephen Ducharme Publications
Among the ferroelectric thin films considered for use in nonvolatile memory devices, the ferroelectric copolymer of polyvinylidene fluoride, PVDF (C2H2F2), with trifluoroethylene, TrFE (C2HF3), has distinct advantages, including low dielectric constant, low processing temperature, relative low cost compared with epitaxial ferroelectric oxides, and compatibility with organic semiconductors. We report the operation and polarization retention properties of a metal– ferroelectric–insulator–semiconductor bistable capacitor memory element consisting of an aluminum gate, a P(VDF-TrFE) Langmuir–Blodgett film, a 30 nm cerium oxide buffer layer, and a moderately doped silicon wafer. The device exhibited a 1.9 …
Ferroelectric Field Effect Transistors Using Very Thin Ferroelectric Polyvinylidene Fluoride Copolymer Films As Gate Dielectrics, A. Gerber, Center Of Nanoelectronic Systems For Information Technology (Cni), Research Center Jülich, Germany, R. Waser, Timothy J. Reece, E. Rije, Stephen Ducharme, Hermann Kohlstedt
Ferroelectric Field Effect Transistors Using Very Thin Ferroelectric Polyvinylidene Fluoride Copolymer Films As Gate Dielectrics, A. Gerber, Center Of Nanoelectronic Systems For Information Technology (Cni), Research Center Jülich, Germany, R. Waser, Timothy J. Reece, E. Rije, Stephen Ducharme, Hermann Kohlstedt
Stephen Ducharme Publications
We report electrical characterization of memory elements consisting of a p-type silicon field-effect transistor incorporating a ferroelectric polymer Langmuir–Blodgett film into the gate insulator to produce bistability through polarization hysteresis. The thin gate insulator, consisting of a 10 nm thick silicon oxide layer and a 35 nm thick ferroelectric polymer film, enabled bistable operation at 4 V. Device hysteresis as a function of gate voltage was evident both in the device capacitance, which was measured between the gate and drain, and in the source-drain conductance. The ferroelectric film polarization was not saturated, even up to operating voltages of 10 V. …
Why Ferroelectric Polyvinylidene Fluoride Is Special, Matt Poulsen, Stephen Ducharme
Why Ferroelectric Polyvinylidene Fluoride Is Special, Matt Poulsen, Stephen Ducharme
Stephen Ducharme Publications
Ferroelectric polymers entail a number of constraints, which together limit the useful compositional variations. These constraints include the following: a stable molecular dipole moment, compact crystal structure, conformational flexibility, and minimal steric hindrance. They are well satisfied by the prototype ferroelectric polymer, polyvinylidene fluoride, and yet almost every other conceivable molecular structure is limited by comparison.
Vibrational Properties Of Ferroelectric Β-Vinylidene Fluoride Polymers And Oligomers, Serge M. Nakhmanson, Rafal Korlacki, J. Travis Johnston, Stephen Ducharme, Zhongxin Ge, James M. Takacs
Vibrational Properties Of Ferroelectric Β-Vinylidene Fluoride Polymers And Oligomers, Serge M. Nakhmanson, Rafal Korlacki, J. Travis Johnston, Stephen Ducharme, Zhongxin Ge, James M. Takacs
Stephen Ducharme Publications
We utilize a plane-wave density-functional theory approach to investigate the vibrational properties of the all-trans ferroelectric phase of poly(vinylidene fluoride) (β-PVDF) showing that its stable state corresponds to the Ama2 structure with ordered dihedral tilting of the VDF monomers along the polymer chains. We then combine our theoretical analysis with IR spectroscopy to examine vibrations in oligomer crystals that are structurally related to the β-PVDF phase. We demonstrate that these materials—which can be grown in a highly crystalline form—exhibit IR activity similar to that of β-PVDF, making them an attractive choice for the studies of electroactive phenomena and phase transitions …