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Full-Text Articles in Physical Sciences and Mathematics
Kinetics Of Ferroelectric Switching In Ultrathin Films, G. Vizdrik, Stephen Ducharme, V.M. Fridkin, S.G. Yudin
Kinetics Of Ferroelectric Switching In Ultrathin Films, G. Vizdrik, Stephen Ducharme, V.M. Fridkin, S.G. Yudin
Stephen Ducharme Publications
The kinetics of polarization switching in ultrathin ferroelectric polymer films exhibit a critical behavior; there is a pronounced slowing just above the coercive field and just below the critical temperature. The critical slowing is observed in the switching kinetics of ferroelectric Langmuir-Blodgett films of 70% vinylidene-fluoride and 30% trifluoroethylene copolymer with thickness up to 30 ML. Thicker films exhibit an exponential dependence on the field and temperature that is normally associated with extrinsic switching by domain nucleation and growth. We show that the critical behavior arises naturally from the dynamics of homogeneous intrinsic switching in the context of mean-field theory. …
Comment On: 'Depolarization Corrections To The Coercive Field In Thin-Film Ferroelectrics', Stephen Ducharme, Vladimir Fridkin
Comment On: 'Depolarization Corrections To The Coercive Field In Thin-Film Ferroelectrics', Stephen Ducharme, Vladimir Fridkin
Stephen Ducharme Publications
The Letter by Dawber et al. [J. Phys.: Condens. Matter 15 L393 (2003)] notes that incomplete screening in the electrodes of a ferroelectric capacitor can result in an underestimate for the true coercive field in films of nanometer thickness. We show that their estimate of the magnitude of this correction it too large in the case of ferroelectric copolymer Langmuir- Blodgett films and, as a result, invalidates the claim that finite-size scaling of the ferroelectric coercive field is evident in films thinner than 15 nm.
Infrared Spectroscopic Ellipsometry Study Of Vinylidene Fluoride (70%)-Trifluoroethylene (30%) Copolymer Langmuir-Blodgett Films, Mengjun Bai, Matt Poulsen, A.V. Sorokin, Stephen Ducharme, C.M. Herzinger, V.M. Fridkin
Infrared Spectroscopic Ellipsometry Study Of Vinylidene Fluoride (70%)-Trifluoroethylene (30%) Copolymer Langmuir-Blodgett Films, Mengjun Bai, Matt Poulsen, A.V. Sorokin, Stephen Ducharme, C.M. Herzinger, V.M. Fridkin
Stephen Ducharme Publications
We report the studies of the molecular conformation and chain orientations through characterization of the vibrational modes in crystalline Langmuir–Blodgett films of the polyvinylidene fluoride/trifluoroethylene copolymer. The infrared spectra obtained by polarized reflectometry and ellipsometry showed that the ferroelectric phase has predominantly all-trans conformation and the paraelectric phase has predominantly alternating trans-gauche conformation, as in solvent-formed films of the same copolymer. The results showed that the polymer chains are predominantly parallel to the film plane with a random in-plane orientation and most of the ferroelectric phase vibrational mode behaviors are consistent with the published mode assignments. The ferroelectric phase optical …
Theoretical Study On The Optical Properties Of Polyvinylidene Fluoride Crystal, Chun-Gang Duan, Wai-Ning Mei, Wei-Guo Yin, Jianjun Liu, J. R. Hardy, Mengjun Bai, Stephen Ducharme
Theoretical Study On The Optical Properties Of Polyvinylidene Fluoride Crystal, Chun-Gang Duan, Wai-Ning Mei, Wei-Guo Yin, Jianjun Liu, J. R. Hardy, Mengjun Bai, Stephen Ducharme
Stephen Ducharme Publications
We report our first-principles studies on the linear and non-linear optical properties of ferroelectric polyvinylidene fluoride crystal. Calculated values of the refractive indices agree well with experiments. As regards the second-harmonic-generation coefficients, theoretical values are larger than experimental ones. Possible reasons for the discrepancy are discussed.
Nonvolatile Memory Element Based On A Ferroelectric Polymer Langmuir-Blodgett Film, Timothy J. Reece, Stephen Ducharme, A.V. Sorokin, Matt Poulsen
Nonvolatile Memory Element Based On A Ferroelectric Polymer Langmuir-Blodgett Film, Timothy J. Reece, Stephen Ducharme, A.V. Sorokin, Matt Poulsen
Stephen Ducharme Publications
We report the operation of a potential nonvolatile bistable capacitor memory element consisting of a metal gate, a 170 nm thick ferroelectric Langmuir–Blodgett film of vinylidene fluoride (70%) with trifluoroethylene (30%) copolymer, and a 100 nm thick silicon-oxide insulating layer, all deposited on an n-type silicon semiconductor substrate. The device exhibited clear capacitance hysteresis as the gate voltage was cycled between ±25 V, with a capacitance dynamic range of 8:1 and threshold voltage shift of 2.8 V. The results are in good agreement with the model of Miller and McWhorter [J. Appl. Phys. 72, 5999 (1992)].
Comparison Of The Theoretical And Experimental Band Structure Of Poly(Vinylidene Fluoride) Crystal, Chun-Gang Duan, Wai-Ning Mei, J.R. Hardy, Stephen Ducharme, Jaewu Choi, Peter A. Dowben
Comparison Of The Theoretical And Experimental Band Structure Of Poly(Vinylidene Fluoride) Crystal, Chun-Gang Duan, Wai-Ning Mei, J.R. Hardy, Stephen Ducharme, Jaewu Choi, Peter A. Dowben
Stephen Ducharme Publications
The electronic structure and band symmetries of the ferroelectric phase of poly (vinylidene fluoride) (PVDF) are studied by using the first-principles density-functional method. Our calculated results agree well with the angle-resolved photoemission experiments. We find that the PVDF crystal has an energy gap of about 6 eV at the Γ-point. Large dispersion of the valence band is found only along the chain direction, which is consistent with the quasi-one-dimensional nature of PVDF. In particular, the band symmetries of the valence states deduced theoretically are in good agreement with experiment. Finally, further investigations on the electronic structure of poly(trifluoroethylene) (PTrFE) …