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Articles 31 - 60 of 111
Full-Text Articles in Physics
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 …
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 …
Modeling Of Metal-Ferroelectric-Insulator-Semiconductor Structures Based On Langmuir–Blodgett Copolymer Films, Timothy J. Reece, Stephen Ducharme
Modeling Of Metal-Ferroelectric-Insulator-Semiconductor Structures Based On Langmuir–Blodgett Copolymer Films, Timothy J. Reece, Stephen Ducharme
Stephen Ducharme Publications
Among the ferroelectric thin films used in field-effect transistor devices; the ferroelectric copolymer of polyvinylidene fluoride PVDF –CH2–CF2–, with trifluoroethylene TrFE –CHF–CF2–, has distinct advantages, including low dielectric constant, low processing temperature, low cost, and compatibility with organic semiconductors. The operation of a metal-ferroelectric insulatorsemiconductor structure with PVDF-TrFE as the ferroelectric layer was analyzed and optimized by numerical solution of the Miller and McWhorter model. A model device consisting of 20 nm PVDF/TrFE on a 10-nm-thick high-k dielectric buffer exhibits a memory window of 5 V with an operating voltage of 15 V. The operating voltage can be reduced to …
Nanoscale Domain Patterns In Ultrathin Polymer Ferroelectric Films, Pankaj Sharma, Timothy J. Reece, Daniel W. Wu, Vladimir M. Fridkin, Stephen Ducharme, Alexei Gruverman
Nanoscale Domain Patterns In Ultrathin Polymer Ferroelectric Films, Pankaj Sharma, Timothy J. Reece, Daniel W. Wu, Vladimir M. Fridkin, Stephen Ducharme, Alexei Gruverman
Stephen Ducharme Publications
High-resolution studies of domain configurations in Langmuir–Blodgett films of ferroelectric polymer poly(vinylidene fluoride-trifluoroethylene), P(VDF-TrFE), have been carried out by means of piezoresponse force microscopy (PFM). Changes in film thickness and morphology cause significant variations in polarization patterns. In continuous films and nanomesas with relatively low thickness/grain aspect ratio (<1/10), the relationship between the average domain size and thickness follows the Kittel law. Nanomesas with high aspect ratio (>1/5) exhibit significant deviations from this law, suggesting additional surface-energy-related mechanisms affecting the domain patterns. Polarization reversal within a single crystallite has been demonstrated and local switching parameters (coercive voltage and remnant piezoresponse) have been measured by monitoring the local hysteresis loops. Reliable control of polarization at the sub-grain level demonstrates …
Dielectric Nanocomposites: An Inside-Out Approach To Storing Electrostatic Energy, Stephen Ducharme
Dielectric Nanocomposites: An Inside-Out Approach To Storing Electrostatic Energy, Stephen Ducharme
Stephen Ducharme Publications
The ability to achieve high-energy densities is the central challenge in energy storage and recovery. A promising strategy for increasing energy storage is to use highperformance dielectric materials, such as highly polarizable nanoparticles or polymers, or nanocomposites of the two. In this issue, Kim et al. use a molecular coating and clever chemistry to combine oxide nanoparticles with a polymer matrix, thereby producing an improved nanocomposite dielectric. Some advantages and challenges of using nanocomposites as improved dielectric materials are presented in this Perspective.
Polarization Switching Kinetics Of Ferroelectric Nanomesas Of Vinylidene Fluoride-Trifluoroethylene Copolymer, R. V. Gaynutdinov, O. A. Lysova, S. G. Yudin, A. L. Tolstikhina, A. L. Kholkin, V. M. Fridkin, Stephen Ducharme
Polarization Switching Kinetics Of Ferroelectric Nanomesas Of Vinylidene Fluoride-Trifluoroethylene Copolymer, R. V. Gaynutdinov, O. A. Lysova, S. G. Yudin, A. L. Tolstikhina, A. L. Kholkin, V. M. Fridkin, Stephen Ducharme
Stephen Ducharme Publications
The polarization switching kinetics of ferroelectric polymer nanomesas was investigated using piezoresponse force microscopy. The nanomesas were made by self-organization from Langmuir–Blodgett films of a 70% vinylidene fluoride and 30% trifluoroethylene copolymer. The polarization switching time exhibits an exponential dependence on reciprocal voltage that is consistent with nucleation-type switching dynamics.
Start The Presses, Stephen V. Ducharme, Alexei Gruverman
Start The Presses, Stephen V. Ducharme, Alexei Gruverman
Stephen Ducharme Publications
A simple nanoimprinting method creates arrays of ferroelectric polymer structures suitable for low-cost, non-volatile memories. With the development of nanoimprinted high-quality ferroelectric nanomesa arrays, it seems that we now have all the necessary ingredients to print inexpensive, disposable organic memory chips.
Regulating Self-Organizing Nanostructures Via External Mechanism, Jiangyu Li, Q. G. Du, Stephen Ducharme
Regulating Self-Organizing Nanostructures Via External Mechanism, Jiangyu Li, Q. G. Du, Stephen Ducharme
Stephen Ducharme Publications
Self-organizing nanostructures are ubiquitous in both natural and synthetic materials. They are not only appealing scientifically, by revealing the intrinsic atomic and molecular interactions that might be difficult to detect otherwise, but may also hold the key for the development of novel functional structures and devices. For their technological potential to be fully realized, the size, morphology, and distribution of the self-organizing nanostructures must be regulated. In this paper, we investigate the principles under which the self-organizing nanostructures can be regulated via external mechanisms. Using nanomesa and nanowell formation in polyvinylidene fluoride trifluoroethylene copolymer film as an example, we demonstrate …
Why Are Ferroelectric Polymers Difficult To Find – And Difficult To Verify, Stephen Ducharme
Why Are Ferroelectric Polymers Difficult To Find – And Difficult To Verify, Stephen Ducharme
Stephen Ducharme Publications
The field of electrets encompasses a wide range of materials that maintain an external electric field due to alignment of internal electric dipoles or trapped charge, or both [1]. Polymers incorporating molecular dipoles constitute an important class of electrets, and so it is fitting that we consider the conditions under which such a polymer can also be considered a ferroelectric [2]. Further, because ferroelectric polymers have many uses, it is fruitful to consider how their properties depend on molecular structure [3].
Local Probing Of Relaxation Time Distributions In Ferroelectric Polymer Nanomesas: Time-Resolved Piezoresponse Force Spectroscopy And Spectroscopic Imaging, Brian J. Rodriguez, Stephen Jesse, Jihee Kim, Stephen Ducharme, Sergei V. Kalinin
Local Probing Of Relaxation Time Distributions In Ferroelectric Polymer Nanomesas: Time-Resolved Piezoresponse Force Spectroscopy And Spectroscopic Imaging, Brian J. Rodriguez, Stephen Jesse, Jihee Kim, Stephen Ducharme, Sergei V. Kalinin
Stephen Ducharme Publications
Time-resolved piezoresponse force spectroscopy (TR-PFS) and spectroscopic imaging are developed to probe the spatial variability of relaxation behavior in nanoscale ferroelectric materials and structures. TR-PFS was applied to study polarization dynamics in polyvinylidine fluoride and trifluoroethylene nanomesas. We demonstrate that polarization relaxation in ferroelectric polymers is slow even on the ~10 nm length scale of piezoresponse force microscopy (PFM) signal generation. Furthermore, the relaxation times are found to be nonuniform within the nanomesa, indicative of a complex internal structure. The applicability of TR-PFM for studies of polarization dynamics in ferroelectric polymers and relaxors is discussed.
Polarization Switching Kinetics At The Nanoscale In Ferroelectric Copolymer Langmuir-Blodgett Films, R. V. Gaynutdinov, O. A. Lysova, A. L. Tolstikhina, S. G. Yudin, V. M. Fridkin, Stephen Ducharme
Polarization Switching Kinetics At The Nanoscale In Ferroelectric Copolymer Langmuir-Blodgett Films, R. V. Gaynutdinov, O. A. Lysova, A. L. Tolstikhina, S. G. Yudin, V. M. Fridkin, Stephen Ducharme
Stephen Ducharme Publications
The polarization switching kinetics of ferroelectric Langmuir–Blodgett films of vinylidene fluoride-trifluoroethylene copolymer were investigated by piezoresponse force microscopy with a resolution of 100 nm. The switching time in response to a localized voltage pulse exhibits an exponential dependence on reciprocal voltage, which is consistent with nucleation-limited switching dynamics.
Effects Of An External Electric Field On The Ferroelectric-Paraelectric Phase Transition In Polyvinylidene Fluoride-Trifluoroethylene Copolymer Langmuir-Blodgett Films, Matt Poulsen, A. V. Sorokin, Shireen Adenwalla, Stephen Ducharme, V. M. Fridkin
Effects Of An External Electric Field On The Ferroelectric-Paraelectric Phase Transition In Polyvinylidene Fluoride-Trifluoroethylene Copolymer Langmuir-Blodgett Films, Matt Poulsen, A. V. Sorokin, Shireen Adenwalla, Stephen Ducharme, V. M. Fridkin
Stephen Ducharme Publications
X-ray diffraction and capacitance measurements have been employed to study the structural and dielectric behavior of the ferroelectric-paraelectric phase transition under the influence of a large external electric field. The samples under study are ultrathin (15–100 nm) Langmuir–Blodgett films of a copolymer of vinylidene fluoride (70%) with trifluoroethylene (30%) deposited on aluminum-coated silicon. In situ θ-2θ x-ray diffraction was used to measure the change in interlayer spacing perpendicular to the film surface, corresponding to the (110) direction and indicating that the polymer chains along (001) lie predominantly in the plane, while capacitance measurements were used to monitor the …
Switching Kinetics Of Ferroelectric Polymer Nanomesas, Christina M. Othon, Jihee Kim, Stephen Ducharme, V. M. Fridkin
Switching Kinetics Of Ferroelectric Polymer Nanomesas, Christina M. Othon, Jihee Kim, Stephen Ducharme, V. M. Fridkin
Stephen Ducharme Publications
The switching dynamics and switching time of ferroelectric nanomesas grown from the paraelectric phase of ultrathin Langmuir–Blodgett vinylidene fluoride and trifluoroethylene copolymer films are investigated. Ferroelectric nanomesas are created through heat treatment and self-organization and have an average height of 10 nm and an average diameter of 100 nm. Ferroelectric nanomesas are highly crystalline and are in the ferroelectric phase and switch faster than 50 μs. The dependence of switching time on applied voltage implies an extrinsic switching nature.
Oligo(Vinylidene Fluoride) Langmuir-Blodgett Films Studied By Spectroscopic, Rafal Korlacki, J. Travis Johnston, Jihee Kim, Stephen Ducharme, Daniel W. Thompson, Vladimir M. Fridkin, Zhongxin Ge, James M. Takacs
Oligo(Vinylidene Fluoride) Langmuir-Blodgett Films Studied By Spectroscopic, Rafal Korlacki, J. Travis Johnston, Jihee Kim, Stephen Ducharme, Daniel W. Thompson, Vladimir M. Fridkin, Zhongxin Ge, James M. Takacs
Stephen Ducharme Publications
Thin films of amphiphilic vinylidene fluoride oligomers prepared by Langmuir–Blodgett deposition on silicone substrates were investigated by comparing experimental and theoretical mid-infrared (IR) spectra. The experimental spectra were obtained using infrared spectroscopic ellipsometry. Theoretical spectra were calculated using density functional theory. Excellent correspondence of major IR bands in both data sets shows that the molecular backbone is oriented with the long axis normal to the substrate plane. This is in contrast to poly vinylidene fluoride[1] LB films, in which the polymer chains are parallel to the substrate.
Microimprinting And Ferroelectric Properties Of Poly(Vinylidene Fluoride-Trifluoroethylene) Copolymer Films, Lei Zhang, Stephen Ducharme, Jiangyu Li
Microimprinting And Ferroelectric Properties Of Poly(Vinylidene Fluoride-Trifluoroethylene) Copolymer Films, Lei Zhang, Stephen Ducharme, Jiangyu Li
Stephen Ducharme Publications
Poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] copolymer films have been patterned by microimprinting with excellent quality of pattern transferring. Ferroelectricity of the imprinted films has been confirmed by ferroelectric hysteresis and surface potential measurement, and very good correlation is observed between remnant polarization and surface potential of the imprinted films. Imprinted P(VDF-TrFE) films show high remnant polarization and high poling-induced surface potential when the imprinting temperature is around 140 °C, suggesting that 140 °C is the optimal imprinting temperature for P(VDF-TrFE) films. The patterned ferroelectric P(VDF-TrFE) films can be used for a wide range of applications.
Vitaly Ginzburg: The Last Classical Physicist, Vladimir Fridkin, Stephen Ducharme, Wolfgang Kleemann, Yoshihiro Ishibashi
Vitaly Ginzburg: The Last Classical Physicist, Vladimir Fridkin, Stephen Ducharme, Wolfgang Kleemann, Yoshihiro Ishibashi
Stephen Ducharme Publications
It is a great honor and responsibility to be Guest Editors for the special issue of Ferroelectrics, dedicated to the 90th Birthday of Nobel Prize Winner Prof. Vitaly Ginzburg. We have entitled our Guest Editorial “The Last Classical Physicist” because his creative work practically covers all regions of the modern physics: astronomy, astrophysics, cosmic rays, high spin elementary particles, quantum electrodynamics, solid state physics, including superconductivity and superfluidity, superdiamagnetism and ferrotoroics, crystallooptics and last (but for this journal not least) the theory of ferroelectricity and soft mode conception.
Electron Diffraction Study Of The Structure Of Vinylidene Fluoride–Trifluoroethylene Copolymer Nanocrystals, Mengjun Bai, Xingzhong Li, Stephen Ducharme
Electron Diffraction Study Of The Structure Of Vinylidene Fluoride–Trifluoroethylene Copolymer Nanocrystals, Mengjun Bai, Xingzhong Li, Stephen Ducharme
Stephen Ducharme Publications
The structures of nanocrystals consisting of 70% vinylidene fluoride and 30% trifluoroethylene made by Langmuir–Blodgett deposition were studied using transmission electron microscopy and electron diffraction. Highly ordered nanocrystals with sizes ranging from 100 nm to 4 μm were grown on Langmuir– Blodgett films at a deposition surface pressure of 20 mN m-1. Electron diffraction patterns from individual crystals allowed us to determine the crystal symmetry and lattice parameters. A monoclinic phase had been found with the lattice parameters a = 9.06 ± 0.03 Å, b = 5.18 ± 0.02 Å, c = 20.40 ± 0.05 Å, α = …
Electric Energy Density Of Dielectric Nanocomposites, Jiangyu Li, L. Zhang, Stephen Ducharme
Electric Energy Density Of Dielectric Nanocomposites, Jiangyu Li, L. Zhang, Stephen Ducharme
Stephen Ducharme Publications
Dielectric materials with large electric energy density are actively pursued for many applications. The authors analyze the effective permittivity, breakdown strength, and electric energy density of dielectric nanocomposites using an effective medium approximation, modeling the nanocomposite as a three-phase material by the double-inclusion method. The addition of nanoparticles enhances the permittivity but reduces the breakdown strength, making the potential gain in electric energy density small. In addition, the interfacial interaction shifts the “percolation” threshold toward lower volume fraction of nanoparticles. The analysis suggests that the microstructure of nanocomposites must be carefully controlled to maintain high dielectric strength and therefore realize …
Nanoscale Polarization Manipulation And Imaging Of Ferroelectric Langmuir-Blodgett Polymer Films, Brian J. Rodriguez, Stephen Jesse, Sergei V. Kalinin, Jihee Kim, Stephen Ducharme, V.M. Fridkin
Nanoscale Polarization Manipulation And Imaging Of Ferroelectric Langmuir-Blodgett Polymer Films, Brian J. Rodriguez, Stephen Jesse, Sergei V. Kalinin, Jihee Kim, Stephen Ducharme, V.M. Fridkin
Stephen Ducharme Publications
Piezoresponse force microscopy has been used to manipulate and image polarization of ferroelectric polymer Langmuir-Blodgett films at the nanoscale, achieving polarization control with a resolution below 50 nm and imaging resolution below 5 nm. Individual regions showed square polarization-voltage hysteresis loops, demonstrating bistability of the polarization state. Arbitrary polarization patterns could be repeatedly written and erased with a resolution of 25 to 50 nm, limited by grain size, demonstrating the potential for high-density data storage and retrieval at densities exceeding 250 Gbits/ in2.
The Effect Of Interlayer Interactions On The Ferroelectric–Paraelectric Phase Transition In Multilayered Thin Films Of Vinylidene Fluoride–Trifluoroethylene Copolymers, Jihee Kim, Hoydoo You, Stephen Ducharme, Shireen Adenwalla
The Effect Of Interlayer Interactions On The Ferroelectric–Paraelectric Phase Transition In Multilayered Thin Films Of Vinylidene Fluoride–Trifluoroethylene Copolymers, Jihee Kim, Hoydoo You, Stephen Ducharme, Shireen Adenwalla
Stephen Ducharme Publications
The interaction between ferroelectric polymer films with different transition temperatures is evident in the effect of layer thickness on the ferroelectric– paraelectric phase transition in multilayer films, as revealed by x-ray diffraction and dielectric measurements. The multilayer samples consisted of alternating Langmuir–Blodgett (LB) films of two different copolymers of vinylidene fluoride with trifluoroethylene, one with 80% vinylidene fluoride and a ferroelectric–paraelectric transition temperature on heating of 133 ± 4 °C and the other with 50% vinylidene fluoride and a transition temperature of 70 ± 4 °C. Samples with a repeat period of 20 LB layers (10 contiguous layers of each …