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Full-Text Articles in Physics
Polarization Switching At The Nanoscale In Ferroelectric Copolymer Thin Films, R. V. Gaynutdinov, S. Mitko, S. G. Yudin, V. M. Fridkin, Stephen Ducharme
Polarization Switching At The Nanoscale In Ferroelectric Copolymer Thin Films, R. V. Gaynutdinov, S. Mitko, S. G. Yudin, V. M. Fridkin, Stephen Ducharme
Stephen Ducharme Publications
The polarization switching kinetics were measured at the nanoscale in continuous thin films of a ferroelectric copolymer of vinylidene fluoride and trifluoroethylene. The dependence of the switching rate on voltage for a 54-nm thick film exhibits extrinsic nucleation and domain-growth type kinetics with no true threshold coercive field, and is qualitatively different from the behavior of an 18-nm thick film, which exhibits intrinsic switching kinetics, and a true threshold field. The results are consistent with studies of thin film capacitors of much larger area and with a recent refinement of the theory of the critical size for intrinsic switching.
Electrical Control Of Photoluminescence Wavelength From Semiconductor Quantum Dots In A Ferroelectric Polymer Matrix, Rafal Korlacki, Ravi F. Saraf, Stephen Ducharme
Electrical Control Of Photoluminescence Wavelength From Semiconductor Quantum Dots In A Ferroelectric Polymer Matrix, Rafal Korlacki, Ravi F. Saraf, Stephen Ducharme
Stephen Ducharme Publications
We report controllable tuning of the room temperature photoluminescence band of CdSe semiconductor quantum dots embedded in thin films of ferroelectric copolymer of vinylidene fluoride and trifluoroethylene made by Langmuir-Blodgett deposition. The high breakdown strength of the polymer permits the application of electric fields of up to 400 MV/m and results in a shift in the photoluminescence peak by up to 9 nm, nearly half the fluorescence band width. Moreover, we found that at these high electric fields, the Stark effect exhibits unusual fourth power dependence.
Ferroelectric Control Of Magnetic Anisotropy, Abhijit Mardana, Stephen Ducharme, Shireen Adenwalla
Ferroelectric Control Of Magnetic Anisotropy, Abhijit Mardana, Stephen Ducharme, Shireen Adenwalla
Stephen Ducharme Publications
We demonstrate unambiguous evidence of the electric field control of magnetic anisotropy in a wedge-shaped Co film of varying thickness. A copolymer ferroelectric of 70% vinylidene fluoride with 30% trifluoroethylene, P(VDF-TrFE) overlays the Co wedge, providing a large switchable electric field. As the ferroelectric polarization is switched from up to down, the magnetic anisotropy of the Co films changes by as much as 50%. At the lowest Co thickness the magnetic anisotropy switches from out-of-plane to inplane as the ferroelectric polarization changes from up to down, enabling us to rotate the magnetization through a large angle at constant magnetic field …
Efficiency Enhancement In Organic Solar Cells With Ferroelectric Polymers, Yongbo Yuan, Timothy J. Reece, Pankaj Sharma, Shashi Poddar, Stephen Ducharme, Alexei Gruverman, Yang Yang, Jinsong Huang
Efficiency Enhancement In Organic Solar Cells With Ferroelectric Polymers, Yongbo Yuan, Timothy J. Reece, Pankaj Sharma, Shashi Poddar, Stephen Ducharme, Alexei Gruverman, Yang Yang, Jinsong Huang
Stephen Ducharme Publications
The recombination of electrons and holes in semiconducting polymer–fullerene blends has been identified as a main cause of energy loss in organic photovoltaic devices. Generally, an external bias voltage is required to efficiently separate the electrons and holes and thus prevent their recombination. Here we show that a large, permanent, internal electric field can be ensured by incorporating a ferroelectric polymer layer into the device, which eliminates the need for an external bias. The electric field, of the order of 50 V μm–1, potentially induced by the ferroelectric layer is tens of times larger than that achievable by …
High-Resolution Studies Of Domain Switching Behavior In Nanostructured Ferroelectric Polymers, Pankaj Sharma, Timothy J. Reece, Stephen Ducharme, Alexei Gruverman
High-Resolution Studies Of Domain Switching Behavior In Nanostructured Ferroelectric Polymers, Pankaj Sharma, Timothy J. Reece, Stephen Ducharme, Alexei Gruverman
Stephen Ducharme Publications
We have demonstrated an effective electrical control of polarization in the individual crystalline nanomesas of the ferroelectric polymer, poly(vinylidene fluoride)-trifluoroethylene (PVDF-TrFE) and its relation to the polymer structure. The mechanism of polarization reversal has been investigated via sub-10 nm real space imaging of domain pattern evolution under an applied electric field. The domain switching behavior revealed in PVDF-TrFE nanomesas is drastically different from that observed in inorganic solid-state crystalline ferroelectrics. The nanoscale features of the switching process include remote domain nucleation and spatially nonuniform wall velocity. Local switching spectroscopy and domain dynamics studies relate the observed switching features to a …
Polarization Patterning By Laser-Induced Phase Change In Ferroelectric Polymer Films, Christina M. Othon, Stephen Ducharme
Polarization Patterning By Laser-Induced Phase Change In Ferroelectric Polymer Films, Christina M. Othon, Stephen Ducharme
Stephen Ducharme Publications
Polarization patterns were written on ferroelectric poly(vinylidene- trifluoroethylene) copolymer Langmuir–Blodgett films by heating into the paraelectric phase by laser illumination using two methods. In the first method, patterns were produced by direct writing by a focused continuouswave laser beam that was moved across the sample. This method affords the greatest flexibility. In the second method, the patterns were generated simultaneously with a pulsed laser using a beam interference method. This method produces highly regular patterns quickly over large areas and affords higher patterning resolution. The patterns produced by both methods could be erased and rewritten, making this technique useful for …
Cluster Synthesis Of Monodisperse Rutile-Tio2 Nanoparticles And Dielectric Tio2–Vinylidene Fluoride Oligomer Nanocomposites, Balamurugan Balasubramanian, Kristin L. Kraemer, Shah R. Valloppilly, Stephen Ducharme, David J. Sellmyer
Cluster Synthesis Of Monodisperse Rutile-Tio2 Nanoparticles And Dielectric Tio2–Vinylidene Fluoride Oligomer Nanocomposites, Balamurugan Balasubramanian, Kristin L. Kraemer, Shah R. Valloppilly, Stephen Ducharme, David J. Sellmyer
Stephen Ducharme Publications
The embedding of oxide nanoparticles in polymer matrices produces a greatly enhanced dielectric response by combining the high dielectric strength and low loss of suitable host polymers with the high electric polarizability of nanoparticles. The fabrication of oxide–polymer nanocomposites with well-controlled distributions of nanoparticles is, however, challenging due to the thermodynamic and kinetic barriers between the polymer matrix and nanoparticle fillers. In the present study, monodisperse TiO2 nanoparticles having an average particle size of 14.4 nm and predominant rutile phase were produced using a cluster-deposition technique without high-temperature thermal annealing and subsequently coated with uniform vinylidene fluoride oligomer (VDFO) …
Orientational Imaging In Polar Polymers By Piezoresponse Force Microscopy, Pankaj Sharma, Dong Wu, Shashi Poddar, Timothy J. Reece, Stephen Ducharme, Alexei Gruverman
Orientational Imaging In Polar Polymers By Piezoresponse Force Microscopy, Pankaj Sharma, Dong Wu, Shashi Poddar, Timothy J. Reece, Stephen Ducharme, Alexei Gruverman
Stephen Ducharme Publications
We report orientational imaging of the polarization distribution in nanostructured ferroelectric copolymer of polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE) and collagen fibrils using vertical and lateral modes of piezoresponse force microscopy (PFM). In PVDF-TrFE, detection of azimuthal variations in the lateral PFM signal is attributed to the alignment of the molecular chains along different directions. Local switching in PVDF-TrFE is shown to proceed via 120° or 180° rotation of dipoles around the molecular chain, depending upon the strength of the applied electric field. Analysis of the vertical and lateral PFM signals in collagen reveals polar anisotropy of the electromechanical properties along the axes …
Orientational Imaging In Polar Polymers By Piezoresponse Force Microscopy, Pankaj Sharma, Dong Wu, Shashi Poddar, Timothy J. Reece, Stephen Ducharme, Alexei Gruverman
Orientational Imaging In Polar Polymers By Piezoresponse Force Microscopy, Pankaj Sharma, Dong Wu, Shashi Poddar, Timothy J. Reece, Stephen Ducharme, Alexei Gruverman
Stephen Ducharme Publications
We report orientational imaging of the polarization distribution in nanostructured ferroelectric copolymer of polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE) and collagen fibrils using vertical and lateral modes of piezoresponse force microscopy (PFM). In PVDF-TrFE, detection of azimuthal variations in the lateral PFM signal is attributed to the alignment of the molecular chains along different directions. Local switching in PVDF-TrFE is shown to proceed via 120 degrees or 180 degrees rotation of dipoles around the molecular chain, depending upon the strength of the applied electric field. Analysis of the vertical and lateral PFM signals in collagen reveals polar anisotropy of the electromechanical properties along …