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Sample records for ferroelectric materials

  1. Losses in Ferroelectric Materials.

    PubMed

    Liu, Gang; Zhang, Shujun; Jiang, Wenhua; Cao, Wenwu

    2015-03-01

    Ferroelectric materials are the best dielectric and piezoelectric materials known today. Since the discovery of barium titanate in the 1940s, lead zirconate titanate ceramics in the 1950s and relaxor-PT single crystals (such as lead magnesium niobate-lead titanate and lead zinc niobate-lead titanate) in the 1980s and 1990s, perovskite ferroelectric materials have been the dominating piezoelectric materials for electromechanical devices, and are widely used in sensors, actuators and ultrasonic transducers. Energy losses (or energy dissipation) in ferroelectrics are one of the most critical issues for high power devices, such as therapeutic ultrasonic transducers, large displacement actuators, SONAR projectors, and high frequency medical imaging transducers. The losses of ferroelectric materials have three distinct types, i.e., elastic, piezoelectric and dielectric losses. People have been investigating the mechanisms of these losses and are trying hard to control and minimize them so as to reduce performance degradation in electromechanical devices. There are impressive progresses made in the past several decades on this topic, but some confusions still exist. Therefore, a systematic review to define related concepts and clear up confusions is urgently in need. With this objective in mind, we provide here a comprehensive review on the energy losses in ferroelectrics, including related mechanisms, characterization techniques and collections of published data on many ferroelectric materials to provide a useful resource for interested scientists and engineers to design electromechanical devices and to gain a global perspective on the complex physical phenomena involved. More importantly, based on the analysis of available information, we proposed a general theoretical model to describe the inherent relationships among elastic, dielectric, piezoelectric and mechanical losses. For multi-domain ferroelectric single crystals and ceramics, intrinsic and extrinsic energy

  2. Losses in Ferroelectric Materials

    PubMed Central

    Liu, Gang; Zhang, Shujun; Jiang, Wenhua; Cao, Wenwu

    2015-01-01

    Ferroelectric materials are the best dielectric and piezoelectric materials known today. Since the discovery of barium titanate in the 1940s, lead zirconate titanate ceramics in the 1950s and relaxor-PT single crystals (such as lead magnesium niobate-lead titanate and lead zinc niobate-lead titanate) in the 1980s and 1990s, perovskite ferroelectric materials have been the dominating piezoelectric materials for electromechanical devices, and are widely used in sensors, actuators and ultrasonic transducers. Energy losses (or energy dissipation) in ferroelectrics are one of the most critical issues for high power devices, such as therapeutic ultrasonic transducers, large displacement actuators, SONAR projectors, and high frequency medical imaging transducers. The losses of ferroelectric materials have three distinct types, i.e., elastic, piezoelectric and dielectric losses. People have been investigating the mechanisms of these losses and are trying hard to control and minimize them so as to reduce performance degradation in electromechanical devices. There are impressive progresses made in the past several decades on this topic, but some confusions still exist. Therefore, a systematic review to define related concepts and clear up confusions is urgently in need. With this objective in mind, we provide here a comprehensive review on the energy losses in ferroelectrics, including related mechanisms, characterization techniques and collections of published data on many ferroelectric materials to provide a useful resource for interested scientists and engineers to design electromechanical devices and to gain a global perspective on the complex physical phenomena involved. More importantly, based on the analysis of available information, we proposed a general theoretical model to describe the inherent relationships among elastic, dielectric, piezoelectric and mechanical losses. For multi-domain ferroelectric single crystals and ceramics, intrinsic and extrinsic energy

  3. Photovoltaic effect in Ferroelectric Materials

    NASA Astrophysics Data System (ADS)

    Katiyar, Rajesh K.; Panwar, Neeraj; Morell, G.; Katiyar, Ram S.

    2010-03-01

    Photovoltaic effect in ferroelectric materials is of much interest due to the anomalously large open circuit photovoltages when illuminated. It is concluded that this unprecedented high value of photovoltaic effect is due to the presence of non-centrosymmetry in the ferroelectric materials which gives rise to electron excitation, relaxation, and scattering processes. The photovoltaic efficiencies are, however, limited due to small current densities and the large band gap values of the ferroelectric materials. We have synthesized thin films of BiFeO3 (a low band gap material ˜2.67eV) and ferroelectric material SrBi2Ta2O9(SBT) on silicon substrates with ITO as the bottom electrode. The band gap of the SBT has been decreased by incorporating metallic particles Ag, Pt. in the ferroelectric matrix. The results will be presented.

  4. Calligraphic Poling of Ferroelectric Material

    NASA Technical Reports Server (NTRS)

    Mohageg, Makan; Strekalov, Dmitry; Savchenkov, Anatoliy; Matsko, Adrey; Maleki, Lute; Iltchenko, Vladimir

    2007-01-01

    Calligraphic poling is a technique for generating an arbitrary, possibly complex pattern of localized reversal in the direction of permanent polarization in a wafer of LiNbO3 or other ferroelectric material. The technique is so named because it involves a writing process in which a sharp electrode tip is moved across a surface of the wafer to expose the wafer to a polarizing electric field in the desired pattern. The technique is implemented by use of an apparatus, denoted a calligraphic poling machine (CPM), that includes the electrode and other components as described in more detail below.

  5. Fatigue and hysteresis modeling of ferroelectric materials

    NASA Astrophysics Data System (ADS)

    Yoo, In. K.; Desu, Seshu B.

    1993-10-01

    Due to their nonlinear properties, ferroelectric materials are ideal candidates for smart materials. Degradation properties such as low voltage breakdown, fatigue, and aging have been major problems in commercial applications of these materials. Such degradations affect the lifetime of ferroelectric materials. Therefore, it is important to understand degradation for reliability improvement. In this article, recent studies on fatigue and hysteresis of ferroelectric ceramics such as Lead Zirconate Titanate (PZT) thin films is reviewed. A new fatigue model is discussed in detail which is based on effective one-directional movement of defects by internal field difference, defect entrapment at the ferroelectrics-electrode interface, and resultant polarization loss at the interface. A fatigue equation derived from this model is presented. Fatigue parameters such as initial polarization, piling constant, and decay constant are defined from the fatigue equation and voltage and temperature dependence of fatigue parameters are discussed. The jump distance of defect calculated from voltage dependence of the decay constant is close to the lattice constant of ferroelectric materials, which implies that oxygen or lead vacancies migrate either parallel or antiparallel to the polarization direction. From the temperature dependence of the decay constant, it is shown that the activation energy for domain wall movement plays an important role in fatigue. The hysteresis model of ferroelectrics is shown using polarization reversal. The hysteresis loop is made by four polarization stages: nucleation, growth, merging, and shrinkage of domains. The hysteresis equation confirms that dielectric viscosity controls hysteresis properties, and temperature dependence of the coefficient of dielectric viscosity is also discussed in conjunction with fatigue mechanism.

  6. Ferroelectric HfO2-based materials for next-generation ferroelectric memories

    NASA Astrophysics Data System (ADS)

    Fan, Zhen; Chen, Jingsheng; Wang, John

    2016-05-01

    Ferroelectric random access memory (FeRAM) based on conventional ferroelectric perovskites, such as Pb(Zr,Ti)O3 and SrBi2Ta2O9, has encountered bottlenecks on memory density and cost, because those conventional perovskites suffer from various issues mainly including poor complementary metal-oxide-semiconductor (CMOS)-compatibility and limited scalability. Next-generation cost-efficient, high-density FeRAM shall therefore rely on a material revolution. Since the discovery of ferroelectricity in Si:HfO2 thin films in 2011, HfO2-based materials have aroused widespread interest in the field of FeRAM, because they are CMOS-compatible and can exhibit robust ferroelectricity even when the film thickness is scaled down to below 10 nm. A review on this new class of ferroelectric materials is therefore of great interest. In this paper, the most appealing topics about ferroelectric HfO2-based materials including origins of ferroelectricity, advantageous material properties, and current and potential applications in FeRAM, are briefly reviewed.

  7. EFFECTS OF RADIATION ON FERROELECTRIC AND FERRIMAGNETIC MATERIALS. PART II. FERRIMAGNETIC MATERIALS

    DTIC Science & Technology

    FERRITES , *FERROELECTRIC MATERIALS, *FERROMAGNETIC MATERIALS, *FERROMAGNETISM, *GARNET, *HYSTERESIS, *MAGNETIC MATERIALS, DIELECTRICS, FAST NEUTRONS... SAMARIUM , ARTIFICIAL SATELLITES, SHIELDING, SIMULATION, SPACE ENVIRONMENTS, SPACECRAFT, YTTRIUM COMPOUNDS.

  8. The interface between ferroelectric and 2D material for a Ferroelectric Field-Effect Transistor

    NASA Astrophysics Data System (ADS)

    Park, Nahee; Kang, Haeyong; Lee, Sang-Goo; Lee, Young Hee; Suh, Dongseok

    We have studied electrical property of ferroelectric field-effect transistor which consists of graphene on hexagonal Boron-Nitride (h-BN) gated by a ferroelectric, PMN-PT (i.e. (1-x)Pb(Mg1/3Nb2/3) O3-xPbTiO3) single-crystal substrate. The PMN-PT was expected to have an effect on polarization field into the graphene channel and to induce a giant amount of surface charge. The hexagonal Boron-Nitride (h-BN) flake was directly exfoliated on the PMN-PT substrate for preventing graphene from directly contacting on the PMN-PT substrate. It can make us to observe the effect of the interface between ferroelectric and 2D material on the device operation. Monolayer graphene as 2D channel material, which was confirmed by Raman spectroscopy, was transferred on top of the hexagonal Boron-Nitride (h-BN) by using the conventional dry-transfer method. Here, we can demonstrate that the structure of graphene/hexagonal-BN/ferroelectric field-effect transistor makes us to clearly understand the device operation as well as the interface between ferroelectric and 2D materials by inserting h-BN between them. The phenomena such as anti-hysteresis, current saturation behavior, and hump-like increase of channel current, will be discussed by in terms of ferroelectric switching, polarization-assisted charge trapping.

  9. Experimental investigation of the electrocaloric response in ferroelectric materials

    NASA Astrophysics Data System (ADS)

    Es'kov, A. V.; Belyavskii, P. Yu.; Anokhin, A. S.; Pakhomov, O. V.; Semenov, A. A.; Myl'nikov, I. L.; Nikitin, A. A.; Bui, M. T.; Cherkasskii, M. A.; Plotnikov, V. V.

    2016-07-01

    We have analyzed the electrocaloric response in ferroelectric materials in nonequilibrium thermal conditions. The temperature dependences of the electrocaloric response during polarization and depolarization of ferroelectric samples based on solid solutions of barium-strontium titanate and lead magnoniobate-titanate are considered. The difference in the electrocaloric responses for polarization and depolarization, which can be as large as 5 mK, has been demonstrated experimentally.

  10. Thin-film ferroelectric materials and their applications

    NASA Astrophysics Data System (ADS)

    Martin, Lane W.; Rappe, Andrew M.

    2016-11-01

    Ferroelectric materials, because of their robust spontaneous electrical polarization, are widely used in various applications. Recent advances in modelling, synthesis and characterization techniques are spurring unprecedented advances in the study of these materials. In this Review, we focus on thin-film ferroelectric materials and, in particular, on the possibility of controlling their properties through the application of strain engineering in conventional and unconventional ways. We explore how the study of ferroelectric materials has expanded our understanding of fundamental effects, enabled the discovery of novel phases and physics, and allowed unprecedented control of materials properties. We discuss several exciting possibilities for the development of new devices, including those in electronic, thermal and photovoltaic applications, and transduction sensors and actuators. We conclude with a brief survey of the different directions that the field may expand to over the coming years.

  11. Ferroelectric polymer-based nanocomposites: Towards multiferroic materials

    NASA Astrophysics Data System (ADS)

    Andrew, Jennifer S.

    This dissertation describes new routes towards magnetic-ferroelectric materials, leading to new materials for multiferroic applications. Multiferroic materials exhibit both ferromagnetic and ferroelectric properties, which tend to be mutually exclusive in single-phase materials. Therefore, composite materials are the obvious approach to realizing a material with both a high electric permittivity and high magnetic permeability. In composite systems the magnetoelectric effect arises from a mechanical coupling between a magnetostrictive and a piezoelectric phase. In order to enhance this coupling the interfacial area between the two phases should be maximized. This can be accomplished with nanoparticles, which have a large surface to volume ratio. This work begins with the synthesis of ferrimagnetic (MFe2O 4, M=Ni, Ni0.5Zn0.5, Co) and ferroelectric (BaTiO 3) nanoparticles. Aqueous coprecipitation routes produced superparamagnetic ferrite nanoparticles with an average diameter of 8-10 nanometers. Nanometer sized particles of barium titanate were also produced, but they were cubic and therefore do not exhibit ferroelectric behavior. We then developed routes to form nanoparticle-nanoparticle composites by controlling their stability in solution and therefore their final assembly into magnetic-dielectric nanocomposites. We also developed novel magnetic-ferroelectric composites by filling a ferroelectric polymer with magnetic and dielectric nanoparticles. Polyvinylidene difluoride (PVDF) fibers as well as fibers with continuously dispersed ferrite (Ni0.5Zn0.5Fe2O4) nanoparticles were prepared by electrospinning from dimethyl formamide (DMF) solutions. The effects of the electrospinning processing conditions and nanoparticle loading on the fiber morphology, crystallinity, and the crystalline structure of PVDF were examined. Magnetic and dielectric measurements were also performed. Electrospinning provides a simple technique to form PVDF in the ferroelectric beta

  12. Voltage tunability of thermal conductivity in ferroelectric materials

    DOEpatents

    Ihlefeld, Jon; Hopkins, Patrick Edward

    2016-02-09

    A method to control thermal energy transport uses mobile coherent interfaces in nanoscale ferroelectric films to scatter phonons. The thermal conductivity can be actively tuned, simply by applying an electrical potential across the ferroelectric material and thereby altering the density of these coherent boundaries to directly impact thermal transport at room temperature and above. The invention eliminates the necessity of using moving components or poor efficiency methods to control heat transfer, enabling a means of thermal energy control at the micro- and nano-scales.

  13. Molecular Designs for Enhancement of Polarity in Ferroelectric Soft Materials

    NASA Astrophysics Data System (ADS)

    Ohtani, Ryo; Nakaya, Manabu; Ohmagari, Hitomi; Nakamura, Masaaki; Ohta, Kazuchika; Lindoy, Leonard F.; Hayami, Shinya

    2015-11-01

    The racemic oxovanadium(IV) salmmen complexes, [VO((rac)-(4-X-salmmen))] (X = C12C10C5 (1), C16 (2), and C18 (3); salmmen = N,N‧-monomethylenebis-salicylideneimine) with “banana shaped” molecular structures were synthesized, and their ferroelectric properties were investigated. These complexes exhibit well-defined hysteresis loops in their viscous phases, moreover, 1 also displays liquid crystal behaviour. We observed a synergetic effect influenced by three structural aspects; the methyl substituents on the ethylene backbone, the banana shaped structure and the square pyramidal metal cores all play an important role in generating the observed ferroelectricity, pointing the way to a useful strategy for the creation of advanced ferroelectric soft materials.

  14. Molecular Designs for Enhancement of Polarity in Ferroelectric Soft Materials

    PubMed Central

    Ohtani, Ryo; Nakaya, Manabu; Ohmagari, Hitomi; Nakamura, Masaaki; Ohta, Kazuchika; Lindoy, Leonard F.; Hayami, Shinya

    2015-01-01

    The racemic oxovanadium(IV) salmmen complexes, [VO((rac)-(4-X-salmmen))] (X = C12C10C5 (1), C16 (2), and C18 (3); salmmen = N,N′-monomethylenebis-salicylideneimine) with “banana shaped” molecular structures were synthesized, and their ferroelectric properties were investigated. These complexes exhibit well-defined hysteresis loops in their viscous phases, moreover, 1 also displays liquid crystal behaviour. We observed a synergetic effect influenced by three structural aspects; the methyl substituents on the ethylene backbone, the banana shaped structure and the square pyramidal metal cores all play an important role in generating the observed ferroelectricity, pointing the way to a useful strategy for the creation of advanced ferroelectric soft materials. PMID:26568045

  15. Piezoelectric properties of rhombohedral ferroelectric materials with phase transition

    NASA Astrophysics Data System (ADS)

    Zhao, Xiaofang; Soh, A. K.

    2015-12-01

    The temporal evolution of domain structure and its piezoelectric behavior of ferroelectric material BaTiO3 during the transition process from rhombohedral to tetragonal phase under an applied electric field have been studied by employing Landau-Ginzburg theory and the phase-field method. The results obtained show that, during the transformation process, the intermediate phase was monoclinic MA phase, and several peak values of piezoelectric coefficient appeared at the stage where obvious change of domain pattern occurred. In addition, by comparing the cases of applied electric field with different frequencies, it was found that the maximum piezoelectric coefficient obtained decreased with increasing frequency value. These results are of great significance in tuning the properties of engineering domains in ferroelectrics, and could provide more fundamentals to the design of ferroelectric devices.

  16. Frequency-agile microwave components using ferroelectric materials

    NASA Astrophysics Data System (ADS)

    Colom-Ustariz, Jose G.; Rodriguez-Solis, Rafael; Velez, Salmir; Rodriguez-Acosta, Snaider

    2003-04-01

    The non-linear electric field dependence of ferroelectric thin films can be used to design frequency and phase agile components. Tunable components have traditionally been developed using mechanically tuned resonant structures, ferrite components, or semiconductor-based voltage controlled electronics, but they are limited by their frequency performance, high cost, hgih losses, and integration into larger systems. In contrast, the ferroelectric-based tunable microwave component can easily be integrated into conventional microstrip circuits and attributes such as small size, light weight, and low-loss make these components attractive for broadband and multi-frequency applications. Components that are essential elements in the design of a microwave sensor can be fabricated with ferroelectric materials to achieve tunability over a broad frequency range. It has been reported that with a thin ferroelectric film placed between the top conductor layer and the dielectric material of a microstrip structure, and the proper DC bias scheme, tunable components above the Ku band can be fabricated. Components such as phase shifters, coupled line filters, and Lange couplers have been reported in the literature using this technique. In this wokr, simulated results from a full wave electromagnetic simulator are obtained to show the tunability of a matching netowrk typically used in the design of microwave amplifiers and antennas. In addition, simulated results of a multilayer Lange coupler, and a patch antenna are also presented. The results show that typical microstrip structures can be easily modified to provide frequency agile capabilities.

  17. Rational Design of Molecular Ferroelectric Materials and Nanostructures

    SciTech Connect

    Ducharme, Stephen

    2012-09-25

    The purpose of this project was to gain insight into the properties of molecular ferroelectrics through the detailed study of oligomer analogs of polyvinylidene fluoride (PVDF). By focusing on interactions at both the molecular level and the nanoscale level, we expect to gain improved understanding about the fundamental mechanism of ferroelectricity and its key properties. The research consisted of three complementary components: 1) Rational synthesis of VDF oligomers by Prof. Takacs' group; 2) Detailed structural and electrical studies of thin by Prof. Ducharme's Group; and 3) First-principles computational studies by DOE Lab Partner Dr. Serge Nakhman-son at Argonne National Laboratory. The main results of the work was a detailed understanding of the relationships between the molecular interactions and macroscopic phenomenology of fer-roelectricity VDF oligomers. This is valuable information supporting the development of im-proved electromechanical materials for, e.g., sonar, ultrasonic imaging, artificial muscles, and compliant actuators. Other potential applications include nonvolatile ferroelectric memories, heat-sensing imaging arrays, photovoltaic devices, and functional biomimetic materials. The pro-ject contributed to the training and professional development of undergraduate students and graduate students, post-doctoral assistants, and a high-school teacher. Project personnel took part in several outreach and education activities each year.

  18. Nanocharacterization of the negative stiffness of ferroelectric materials

    NASA Astrophysics Data System (ADS)

    Alipour Skandani, A.; Ctvrtlik, R.; Al-Haik, M.

    2014-08-01

    Phase changing materials such as ferroelectric materials could exhibit negative stiffness under certain thermomechanical environments. This negative stiffness is embodied by a deflection along the opposite direction of the applied load. So far negative stiffness materials were investigated with the specific morphology of embedded inclusions in stiff matrices then the resulting composite is studied to measure the behavior of each constituent indirectly. In this study, a modified nonisothermal nanoindentation method is developed to measure the negative stiffness of triglycine sulfate single crystal directly. This in-situ method is intended to first demonstrate the feasibility of detecting the negative stiffness via nanoindentation and nanocreep of a ferroelectric material at its Curie point and then to quantify the negative stiffness without the need for embedding the crystal within a stiffer matrix.

  19. New Techniques in Characterization of Ferroelectric Materials

    NASA Technical Reports Server (NTRS)

    Sehirlioglu, Alp

    2008-01-01

    Two new techniques have been developed to characterize Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) based ferroelectric single crystals: (i) electro-thermal imaging, and (ii) single crystal x-ray diffraction in the transmission mode. (i) Electro-thermal imaging is a remote sensing technique that can detect the polarization direction and poling state of a whole crystal slice. This imaging technique utilizes an IR camera to determine the field induced temperature change and does not require any special or destructive sample preparation. In the resulting images it is possible to distinguish regions of 180 deg domains. This powerful technique can be used remotely during poling to determine the poling state of the crystal to avoid over-poling that can result in inferior properties and/or cracking of the crystals. Electro-thermal imaging produced the first direct observations of polarization rotation. Under bipolar field, the domains near the corners were the first to switch direction. As the field increased above the coercive field, domains at the center part of the crystals switched direction. (ii) X-ray diffraction in the transmission mode has long been used in structure determination of organic crystals and proteins; however, it is not used much to characterize inorganic systems. 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 single crystals were examined by this XRD technique for the first time, and a never-before-seen super-lattice was revealed with a doubling of the unit cell in all three directions, giving a cell volume eight times that of a traditional perovskite unit cell. The significance of the super-lattice peaks increased with poling, indicating a structural contribution to ordering. Lack of such observations by electron diffraction in the transmission electron microscope examinations suggests the presence of a bulk effect.

  20. Structural Prediction and Experimental Verification of Three New Ferroelectric Materials

    NASA Astrophysics Data System (ADS)

    Arbogast, D. J.; Foster, M. C.; Nielson, R. M.; Photinos, P. J.; Abrahams, S. C.

    1999-05-01

    Aminoguanidinium hexafluorozirconate, potassium niobyl silicate and fresnoite are typical members of a growing group of materials predicted to be new ferroelectrics by the application of structural criteria. Following prediction, undergraduate chemistry majors prepare and physics majors measure the dielectric properties of each. Experimental results will be presented for the three title materials in verification of their predicted property. In addition to the structural criteria on which the predictions depend, the circuits built locally and other instrumentation used for measuring ac and dc hysteresis, the thermal and frequency dependence of the dielectric permittivity, the thermal dependence of the spontaneous polarization and also the pyroelectric coefficient will be presented.

  1. Three theoretical studies of ferroelectric materials in different geometries

    NASA Astrophysics Data System (ADS)

    Palova, Lucia

    Using a combination of numerical and analytical techniques, I present characterizations of ferroelectric materials in bulk, thin-film and nanostructure geometries. My results have impact on ongoing research and on design for nanodevices. Size-dependent effects in ferroelectrics are important due to their long-range electrostatic interactions; thus their dielectric properties depend on electromechanical boundary conditions. In my first study, I address the effects of strain on the measured properties of thin-film (TF) ferroelectrics. It has been suggested that the observed suppression of many TF dielectric characteristics implies underlying strain gradients in the film. I show that the same effects can be explained by a simpler model with homogeneous strain, and I suggest a "smoking gun" benchtop probe. The quantum paraelectric-ferroelectric transition (QPFT) is the topic of my second study. Using methods including finite-size scaling and self-consistent Gaussian theory, I calculate the classical-quantum crossover in the dielectric susceptbility and the resulting temperature-pressure phase diagram; comparison with current experiment is excellent and predictions are made for future measurements. Here, temperature can be considered a "finite-size effet" in time, and previous results on the QPFT using diagrammatic techniques are recovered and extended using this approach. Recent synthesis of artificially structured oxides with "checkerboard" patterning at the nanoscale has been reported, and this serves as motivation for my third study. Here, I use first-principles methods to characterize an atomic-scale BiFeO3-BiMnO3 nanocheckerboard, and find that it has properties that are distinctive from those of either parent compound. More specifically, it has both a spontaneous polarization and magnetization, and also displays a magnetostructural effect. My work on this prototypical multiferroic nanocheckerboard motivates further theoretical and experimental studies of new

  2. Ferroelectric Material Application: Modeling Ferroelectric Field Effect Transistor Characteristics from Micro to Nano

    NASA Technical Reports Server (NTRS)

    MacLeod, Todd, C.; Ho, Fat Duen

    2006-01-01

    All present ferroelectric transistors have been made on the micrometer scale. Existing models of these devices do not take into account effects of nanoscale ferroelectric transistors. Understanding the characteristics of these nanoscale devices is important in developing a strategy for building and using future devices. This paper takes an existing microscale ferroelectric field effect transistor (FFET) model and adds effects that become important at a nanoscale level, including electron velocity saturation and direct tunneling. The new model analyzed FFETs ranging in length from 40,000 nanometers to 4 nanometers and ferroelectric thickness form 200 nanometers to 1 nanometer. The results show that FFETs can operate on the nanoscale but have some undesirable characteristics at very small dimensions.

  3. Preparation of transparent conductors ferroelectric memory materials and ferrites

    DOEpatents

    Bhattacharya, Raghu Nath; Ginley, David S.

    1998-01-01

    A process for the preparation by electrodeposition of metal oxide film and powder compounds for ferroelectric memory materials and ferrites wherein the metal oxide includes a plurality of metals. The process comprises providing an electrodeposition bath, providing soluble salts of the metals to this bath, electrically energizing the bath to thereby cause formation of a recoverable film of metal on the electrode, recovering the resultant film as a film or a powder, and recovering powder formed on the floor of the bath. The films and powders so produced are subsequently annealed to thereby produce metal oxide for use in electronic applications. The process can be employed to produce metal-doped metal oxide film and powder compounds for transparent conductors. The process for preparation of these metal-doped metal oxides follows that described above.

  4. Preparation of transparent conductors ferroelectric memory materials and ferrites

    DOEpatents

    Bhattacharya, R.N.; Ginley, D.S.

    1998-07-28

    A process is described for the preparation by electrodeposition of metal oxide film and powder compounds for ferroelectric memory materials and ferrites wherein the metal oxide includes a plurality of metals. The process comprises providing an electrodeposition bath, providing soluble salts of the metals to this bath, electrically energizing the bath to thereby cause formation of a recoverable film of metal on the electrode, recovering the resultant film as a film or a powder, and recovering powder formed on the floor of the bath. The films and powders so produced are subsequently annealed to thereby produce metal oxide for use in electronic applications. The process can be employed to produce metal-doped metal oxide film and powder compounds for transparent conductors. The process for preparation of these metal-doped metal oxides follows that described above.

  5. An extended molecular statics algorithm simulating the electromechanical continuum response of ferroelectric materials

    NASA Astrophysics Data System (ADS)

    Endres, F.; Steinmann, P.

    2014-12-01

    Molecular dynamics (MD) simulations of ferroelectric materials have improved tremendously over the last few decades. Specifically, the core-shell model has been commonly used for the simulation of ferroelectric materials such as barium titanate. However, due to the computational costs of MD, the calculation of ferroelectric hysteresis behaviour, and especially the stress-strain relation, has been a computationally intense task. In this work a molecular statics algorithm, similar to a finite element method for nonlinear trusses, has been implemented. From this, an algorithm to calculate the stress dependent continuum deformation of a discrete particle system, such as a ferroelectric crystal, has been devised. Molecular statics algorithms for the atomistic simulation of ferroelectric materials have been previously described. However, in contrast to the prior literature the algorithm proposed in this work is also capable of effectively computing the macroscopic ferroelectric butterfly hysteresis behaviour. Therefore the advocated algorithm is able to calculate the piezoelectric effect as well as the converse piezoelectric effect simultaneously on atomistic and continuum length scales. Barium titanate has been simulated using the core-shell model to validate the developed algorithm.

  6. FeTRAM. An organic ferroelectric material based novel random access memory cell.

    PubMed

    Das, Saptarshi; Appenzeller, Joerg

    2011-09-14

    Science and technology in the electronics area have always been driven by the development of materials with unique properties and their integration into novel device concepts with the ultimate goal to enable new functionalities in innovative circuit architectures. In particular, a shift in paradigm requires a synergistic approach that combines materials, devices and circuit aspects simultaneously. Here we report the experimental implementation of a novel nonvolatile memory cell that combines silicon nanowires with an organic ferroelectric polymer-PVDF-TrFE-into a new ferroelectric transistor architecture. Our new cell, the ferroelectric transistor random access memory (FeTRAM) exhibits similarities with state-of-the-art ferroelectric random access memories (FeRAMs) in that it utilizes a ferroelectric material to store information in a nonvolatile (NV) fashion but with the added advantage of allowing for nondestructive readout. This nondestructive readout is a result of information being stored in our cell using a ferroelectric transistor instead of a capacitor-the scheme commonly employed in conventional FeRAMs.

  7. Supramolecular ferroelectrics

    NASA Astrophysics Data System (ADS)

    Tayi, Alok S.; Kaeser, Adrien; Matsumoto, Michio; Aida, Takuzo; Stupp, Samuel I.

    2015-04-01

    Supramolecular chemistry uses non-covalent interactions to coax molecules into forming ordered assemblies. The construction of ordered materials with these reversible bonds has led to dramatic innovations in organic electronics, polymer science and biomaterials. Here, we review how supramolecular strategies can advance the burgeoning field of organic ferroelectricity. Ferroelectrics -- materials with a spontaneous and electrically reversible polarization -- are touted for use in non-volatile computer memories, sensors and optics. Historically, this physical phenomenon has been studied in inorganic materials, although some organic examples are known and strong interest exists to extend the search for ferroelectric molecular systems. Other undiscovered applications outside this regime could also emerge. We describe the key features necessary for molecular and supramolecular dipoles in organic ferroelectrics and their incorporation into ordered systems, such as porous frameworks and liquid crystals. The goal of this Review is to motivate the development of innovative supramolecular ferroelectrics that exceed the performance and usefulness of known systems.

  8. Non-traditional solution routes to ferroelectric materials

    SciTech Connect

    Boyle, T.J.; Buchheit, C.D.; Al-Shareef, H.N.

    1997-04-01

    Non-traditional precursor solutions for production of ferroelectric thin films have been developed for PXZT (X = L, N, S), SBT, and PMN systems. For PXZT and SBT, pyridine is a key solvent, wherein, it both solubilizes and reduces the reactivity of the individual components of the solution. Further control of the final films has been obtained using novel tailor-made precursors to dictate their properties.

  9. Electrically tunable near-field radiative heat transfer via ferroelectric materials

    SciTech Connect

    Huang, Yi; Boriskina, Svetlana V.; Chen, Gang

    2014-12-15

    We explore ways to actively control near-field radiative heat transfer between two surfaces that relies on electrical tuning of phonon modes of ferroelectric materials. Ferroelectrics are widely used for tunable electrical devices, such as capacitors and memory devices; however, their tunable properties have not yet been examined for heat transfer applications. We show via simulations that radiative heat transfer between two ferroelectric materials can be enhanced by over two orders of magnitude over the blackbody limit in the near field, and can be tuned as much as 16.5% by modulating the coupling between surface phonon polariton modes at the two surfaces via varying external electric fields. We then discuss how to maximize the modulation contrast for tunable thermal devices using the studied mechanism.

  10. Ferroelectricity in Covalently functionalized Two-dimensional Materials: Integration of High-mobility Semiconductors and Nonvolatile Memory.

    PubMed

    Wu, Menghao; Dong, Shuai; Yao, Kailun; Liu, Junming; Zeng, Xiao Cheng

    2016-11-09

    Realization of ferroelectric semiconductors by conjoining ferroelectricity with semiconductors remains a challenging task because most present-day ferroelectric materials are unsuitable for such a combination due to their wide bandgaps. Herein, we show first-principles evidence toward the realization of a new class of two-dimensional (2D) ferroelectric semiconductors through covalent functionalization of many prevailing 2D materials. Members in this new class of 2D ferroelectric semiconductors include covalently functionalized germanene, and stanene (Nat. Commun. 2014, 5, 3389), as well as MoS2 monolayer (Nat. Chem. 2015, 7, 45), covalent functionalization of the surface of bulk semiconductors such as silicon (111) (J. Phys. Chem. B 2006, 110 , 23898), and the substrates of oxides such as silica with self-assembly monolayers (Nano Lett. 2014, 14, 1354). The newly predicted 2D ferroelectric semiconductors possess high mobility, modest bandgaps, and distinct ferroelectricity that can be exploited for developing various heterostructural devices with desired functionalities. For example, we propose applications of the 2D materials as 2D ferroelectric field-effect transistors with ultrahigh on/off ratio, topological transistors with Dirac Fermions switchable between holes and electrons, ferroelectric junctions with ultrahigh electro-resistance, and multiferroic junctions for controlling spin by electric fields. All these heterostructural devices take advantage of the combination of high-mobility semiconductors with fast writing and nondestructive reading capability of nonvolatile memory, thereby holding great potential for the development of future multifunctional devices.

  11. Emerging ferroelectric transistors with nanoscale channel materials: the possibilities, the limitations

    NASA Astrophysics Data System (ADS)

    Hong, Xia

    2016-03-01

    Combining the nonvolatile, locally switchable polarization field of a ferroelectric thin film with a nanoscale electronic material in a field effect transistor structure offers the opportunity to examine and control a rich variety of mesoscopic phenomena and interface coupling. It is also possible to introduce new phases and functionalities into these hybrid systems through rational design. This paper reviews two rapidly progressing branches in the field of ferroelectric transistors, which employ two distinct classes of nanoscale electronic materials as the conducting channel, the two-dimensional (2D) electron gas graphene and the strongly correlated transition metal oxide thin films. The topics covered include the basic device physics, novel phenomena emerging in the hybrid systems, critical mechanisms that control the magnitude and stability of the field effect modulation and the mobility of the channel material, potential device applications, and the performance limitations of these devices due to the complex interface interactions and challenges in achieving controlled materials properties. Possible future directions for this field are also outlined, including local ferroelectric gate control via nanoscale domain patterning and incorporating other emergent materials in this device concept, such as the simple binary ferroelectrics, layered 2D transition metal dichalcogenides, and the 4d and 5d heavy metal compounds with strong spin-orbit coupling.

  12. A Bayesian approach to modeling diffraction profiles and application to ferroelectric materials

    DOE PAGES

    Iamsasri, Thanakorn; Guerrier, Jonathon; Esteves, Giovanni; ...

    2017-02-01

    A new statistical approach for modeling diffraction profiles is introduced, using Bayesian inference and a Markov chain Monte Carlo (MCMC) algorithm. This method is demonstrated by modeling the degenerate reflections during application of an electric field to two different ferroelectric materials: thin-film lead zirconate titanate (PZT) of composition PbZr0.3Ti0.7O3and a bulk commercial PZT polycrystalline ferroelectric. Here, the new method offers a unique uncertainty quantification of the model parameters that can be readily propagated into new calculated parameters.

  13. Research in High Dielectric Properties of Ferroelectric Materials

    DTIC Science & Technology

    1992-01-01

    22 5.0 GROWTH OF PEROVSKITE PZT AND PLZT THIN FILMS.............. 36 6.0 FERROELECTRIC PROPERTIES OF LANTHANUM -MODIFIED Sro...properties. 23 C 1151ODM/bje o Rockwell International Science Center SC5345.FR INTRODUCTION A lanthanum -modified lead-zirconate-titanate solid solution...BISMUTH FERRITE SC44827 HIGH TC CUBIC ,,7000 MORPHOTROPIC T BOUNDARY Wi C HOW WIDE? TETRAGONAL RH PbTiOl BiFeO 3 VERY LARGE STRAIN Pb0 7 Bi *3T 10.7 Fe

  14. Graphene-based hybrid structures combined with functional materials of ferroelectrics and semiconductors

    NASA Astrophysics Data System (ADS)

    Jie, Wenjing; Hao, Jianhua

    2014-05-01

    Fundamental studies and applications of 2-dimensional (2D) graphene may be deepened and broadened via combining graphene sheets with various functional materials, which have been extended from the traditional insulator of SiO2 to a versatile range of dielectrics, semiconductors and metals, as well as organic compounds. Among them, ferroelectric materials have received much attention due to their unique ferroelectric polarization. As a result, many attractive characteristics can be shown in graphene/ferroelectric hybrid systems. On the other hand, graphene can be integrated with conventional semiconductors and some newly-discovered 2D layered materials to form distinct Schottky junctions, yielding fascinating behaviours and exhibiting the potential for various applications in future functional devices. This review article is an attempt to illustrate the most recent progress in the fabrication, operation principle, characterization, and promising applications of graphene-based hybrid structures combined with various functional materials, ranging from ferroelectrics to semiconductors. We focus on mechanically exfoliated and chemical-vapor-deposited graphene sheets integrated in numerous advanced devices. Some typical hybrid structures have been highlighted, aiming at potential applications in non-volatile memories, transparent flexible electrodes, solar cells, photodetectors, and so on.

  15. Tunable ferroelectric meta-material phase shifter embedded inside low temperature co-fired ceramics (LTCC)

    NASA Astrophysics Data System (ADS)

    Tork, Hossam S.

    This dissertation describes electrically tunable microwave devices utilizing low temperature co-fired ceramics (LTCC) and thick film via filled with the ferroelectric materials barium strontium titanate (BST) and barium zirconate titanate (BZT). Tunable ferroelectric capacitors, zero meta-material phase shifters, and tunable meta-material phase shifters are presented. Microwave phase shifters have many applications in microwave devices. They are essential components for active and passive phased array antennas and their most common use is in scanning phased array antennas. They are used in synthetic aperture radars (SAR), low earth orbit (LEO) communication satellites, collision warning radars, and intelligent vehicle highway systems (IVHS), in addition to various other applications. Tunable ferroelectric materials have been investigated, since they offer the possibility of lowering the total cost of phased arrays. Two of the most promising ferroelectric materials in microwave applications are BST and BZT. The proposed design and implementation in this research introduce new types of tunable meta-material phase shifters embedded inside LTCC, which use BST and BZT as capacitive tunable dielectric material controlled by changing the applied voltage. This phase shifter has the advantages of meta-material structures, which produce little phase error and compensation while having the simultaneous advantage of using LTCC technology for embedding passive components that improve signal integrity (several signal lines, power planes, and ground planes) by using different processes like via filling, screen printing, laminating and firing that can be produced in compact sizes at a low cost. The via filling technique was used to build tunable BST, BZT ferroelectric material capacitors to control phase shift. Finally, The use of the proposed ferroelectric meta-material phase shifter improves phase shifter performance by reducing insertion loss in both transmitting and receiving

  16. High Resolution Electromechanical Imaging of Ferroelectric Materials in a Liquid Environment by Piezoresponse Force Microscopy

    SciTech Connect

    Rodriguez, Brian J; Jesse, Stephen; Baddorf, Arthur P; Kalinin, Sergei V

    2006-01-01

    High-resolution imaging of ferroelectric materials using piezoresponse force microscopy (PFM) is demonstrated in an aqueous environment. The elimination of both long-range electrostatic forces and capillary interactions results in a localization of the ac field to the tip-surface junction and allows the tip-surface contact area to be controlled. This approach results in spatial resolutions approaching the limit of the intrinsic domain-wall width. Imaging at frequencies corresponding to high-order cantilever resonances minimizes the viscous damping and added mass effects on cantilever dynamics and allows sensitivities comparable to ambient conditions. PFM in liquids will provide novel opportunities for high-resolution studies of ferroelectric materials, imaging of soft polymer materials, and imaging of biological systems in physiological environments on, ultimately, the molecular level.

  17. Ferroelectric ultrathin perovskite films

    DOEpatents

    Rappe, Andrew M; Kolpak, Alexie Michelle

    2013-12-10

    Disclosed herein are perovskite ferroelectric thin-film. Also disclosed are methods of controlling the properties of ferroelectric thin films. These films can be used in a variety materials and devices, such as catalysts and storage media, respectively.

  18. III-nitride integration on ferroelectric materials of lithium niobate by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Namkoong, Gon; Lee, Kyoung-Keun; Madison, Shannon M.; Henderson, Walter; Ralph, Stephen E.; Doolittle, W. Alan

    2005-10-01

    Integration of III-nitride electrical devices on the ferroelectric material lithium niobate (LiNbO3) has been demonstrated. As a ferroelectric material, lithium niobate has a polarization which may provide excellent control of the polarity of III-nitrides. However, while high temperature, 1000°C, thermal treatments produce atomically smooth surfaces, improving adhesion of GaN epitaxial layers on lithium niobate, repolarization of the substrate in local domains occurs. These effects result in multi domains of mixed polarization in LiNbO3, producing inversion domains in subsequent GaN epilayers. However, it is found that AlN buffer layers suppress inversion domains of III-nitrides. Therefore, two-dimensional electron gases in AlGaN /GaN heterojunction structures are obtained. Herein, the demonstration of the monolithic integration of high power devices with ferroelectric materials presents possibilities to control LiNbO3 modulators on compact optoelectronic/electronic chips.

  19. Targeted basic studies of ferroelectric and ferroelastic materials for piezoelectric transducer applications

    NASA Astrophysics Data System (ADS)

    Cross, L. E.; Newnham, R. E.; Barsch, G. R.; Biggers, J. V.

    1983-03-01

    The work reported covers the fifth and final year of the program of targeted basic studies of ferroelectric and ferroelastic materials for piezoelectric transducer applications. Major achievements include: the development of a physical approach to understanding active composites, leading to the development of several new families of PZT, polymer piezoelectric composites for hydrophone application. These are new advances in the phenomenology and microscopic theory of electrostriction, and the evolution of a new family of high strain ferroelectric relaxor materials for practical application. New basic understanding of the polarization mechanisms in ferroelectric relaxors has been aided by the study of order disorder of the cation arrangement in lead scandium tantalate, and the results correlate well with studies of relaxor behavior, and of shape memory effects in PLZT ceramics. Low temperature studies on pure and doped PZTs have given the first clear indication of the intrinsic (averaged) single domain in response and correlate exceedingly well with earlier phenomenological theory. Crystal growth and ceramic processing studies have developed hand in hand with program needs providing new forms of conventional materials, new grain oriented structures and single crystals.

  20. Direct Imaging of the Spatial and Energy Distribution of Nucleation Centers in Ferroelectric Materials

    SciTech Connect

    Jesse, Stephen; Rodriguez, Brian J; Choudhury, S; Baddorf, Arthur P; Vrejoiu, I.; Hesse, D.; Alexe, M.; Eliseev, E. A.; Morozovska, A. N.; Zhang, J; Chen, L. Q.; Kalinin, Sergei V

    2008-01-01

    Macroscopic ferroelectric polarization switching, similar to other first order phase transitions, is controlled by nucleation centers. Despite 50 years of extensive theoretical and experimental effort, the microstructural origins of the Landauer paradox, i.e. the experimentally observed low values of coercive fields in ferroelectrics corresponding to implausibly large nucleation activation energies, are still a mystery. In this letter, we develop an approach to visualize the nucleation centers controlling polarization switching processes with nanometer resolution, determine their spatial and energy distribution, and correlate them to local microstructure. The random bond and random field components of the disorder potential are extracted from positive and negative nucleation biases. Observation of enhanced nucleation activity at the 90 domain wall boundaries and intersections combined with phase-field modeling identifies them as a class of nucleation centers that control switching in structural-defect free materials.

  1. Correlation Between Material Properties of Ferroelectric Thin Films and Design Parameters for Microwave Device Applications: Modeling Examples and Experimental Verification

    NASA Technical Reports Server (NTRS)

    Miranda, Felix A.; VanKeuls, Fred W.; Subramanyam, Guru; Mueller, Carl H.; Romanofsky, Robert R.; Rosado, Gerardo

    2000-01-01

    The application of thin ferroelectric films for frequency and phase agile components is the topic of interest of many research groups worldwide. Consequently, proof-of-concepts (POC) of different tunable microwave components using either (HTS, metal)/ferroelectric thin film/dielectric heterostructures or (thick, thin) film "flip-chip" technology have been reported. Either as ferroelectric thin film characterization tools or from the point of view of circuit implementation approach, both configurations have their respective advantages and limitations. However, we believe that because of the progress made so far using the heterostructure (i.e., multilayer) approach, and due to its intrinsic features such as planar configuration and monolithic integration, a study on the correlation of circuit geometry aspects and ferroelectric material properties could accelerate the insertion of this technology into working systems. In this paper, we will discuss our study performed on circuits based on microstrip lines at frequencies above 10 GHz, where the multilayer configuration offers greater ease of insertion due to circuit's size reduction. Modeled results of relevant circuit parameters such as the characteristic impedance, effective dielectric constant, and attenuation as a function of ferroelectric film's dielectric constant, tans, and thickness, will be presented for SrTiO3 and Ba(x)Sr(1-x)TiO3 ferroelectric films. A comparison between the modeled and experimental data for some of these parameters will be presented.

  2. Continuum damage model for ferroelectric materials and its application to multilayer actuators

    NASA Astrophysics Data System (ADS)

    Gellmann, Roman; Ricoeur, Andreas

    2016-05-01

    In this paper a micromechanical continuum damage model for ferroelectric materials is presented. As a constitutive law it is implemented into a finite element (FE) code. The model is based on micromechanical considerations of domain switching and its interaction with microcrack growth and coalescence. A FE analysis of a multilayer actuator is performed, showing the initiation of damage zones at the electrode tips during the poling process. Further, the influence of mechanical pre-stressing on damage evolution and actuating properties is investigated. The results provided in this work give useful information on the damage of advanced piezoelectric devices and their optimization.

  3. Examination of the possibility of negative capacitance using ferroelectric materials in solid state electronic devices.

    PubMed

    Krowne, C M; Kirchoefer, S W; Chang, W; Pond, J M; Alldredge, L M B

    2011-03-09

    We show here, using fundamental energy storage relationships for capacitors, that there are severe constraints upon what can be realized utilizing ferroelectric materials as FET dielectrics. A basic equation governing all small signal behavior is derived, a negative capacitance quality factor is defined based upon it, and thousands of carefully measured devices are evaluated. We show that no instance of negative capacitance occurs within our huge database. Furthermore, we demonstrate that highly nonlinear biasing behavior in a series stack could be misinterpreted as giving a negative capacitance.

  4. Targeted basic studies of ferroelectric and ferroelastic materials for piezoelectric transducer applications

    NASA Astrophysics Data System (ADS)

    Cross, L. E.; Newnham, R. E.; Barsch, G. R.; Biggers, J. V.

    1983-03-01

    The report delineates the new progress made in the fifth and final year and discusses the major accomplishments of the full five year program both in the basic science and in the spin off to practical transducer applications. Possible new areas of study which are suggested by the present studies are briefly reported. Major achievements include the development of a physical approach to understanding active composites, leading to the development of several new families of PZT:polymer piezoelectric composites for hydrophone application. New advances in the phenomenology and microscopic theory of electrostriction, and the evolution of a new family of high strain ferroelectric relaxor materials for practical application. New basic understanding of the polarization mechanisms in ferroelectric relaxors has been aided by the study of order-disorder of the cation arrangement in lead scandium tantalate, and the results correlate well with studies of relaxor behavior, and of shape memory effects in PLZT ceramics. Low temperature studies on pure and doped PZTs have given the first clear indication of the intrinsic (averaged) single domain response and correlate exceedingly well with earlier phenomenological theory. Crystal growth and ceramic processing studies have developed hand-in-hand with program needs providing new forms of conventional materials, new grain oriented structures and single crystals.

  5. Millimeter-Wave Dielectric Properties of Single Crystal Ferroelectric and Dielectric Materials

    SciTech Connect

    McCloy, John S.; Korolev, Konstantin A.; Li, Zijing; Afsar, Mohammed N.; Sundaram, S. K.

    2011-01-03

    Transmittance measurements on various single crystal ferroelectric materials over a broad millimeter-wave frequency range have been performed. Frequency dependence of the complex dielectric permittivity has been determined in the millimeter wave region for the first time. The measurements have been employed using a free-space quasi-optical millimeter-wave spectrometer equipped with a set of high power backward wave oscillators (BWOs) as sources of coherent radiation, tunable in the range from 30 - 120 GHz. The uncertainties and possible sources of instrumentation and measurement errors related to the free-space millimeter-wave technique are discussed. This work has demonstrated that precise MMW permittivities can be obtained even on small thin crystals using the BWO quasi-optical approach.

  6. Millimeter-wave dielectric properties of single-crystal ferroelectric and dielectric materials.

    PubMed

    McCloy, John S; Korolev, Konstantin A; Li, Zijing; Afsar, Mohammed N; Sundaram, Shanmugavelayutham K

    2011-01-01

    Transmittance measurements on various single crystal ferroelectric and dielectric materials, BaTiO(3), SrTiO(3), LiNbO(3), LiTaO(3), (PbMg(1/3)Nb(2/3)O(3))0.73-(PbTiO(3))0.27, LaAlO(3), and Bi(4)Ge(3)O(12), over a broad millimeter-wave (MMW) frequency range have been performed. Frequency dependence of the complex dielectric permittivity has been measured in the MMW region using high-power sources for the first time, using a free-space, quasi-optical MMW spectrometer equipped with high-power backward wave oscillators (BWOs) as sources of coherent radiation, tunable in the range from 30 to 120 and 180 to 260 GHz. These results are compared with MMW permittivity of these materials obtained by other methods as well as to RF, microwave, and optical frequency permittivities for all the materials tested. The effects of both crystallographic orientation and quality of the surface polishing of the crystals have been examined. Uncertainties and possible sources of instrumentation and measurement errors related to the freespace MMW technique are discussed. This work demonstrates that precise MMW permittivity data can be obtained even on relatively small and thin crystals of different surface conditions and orientations using the high-power BWO-based quasioptical approach.

  7. Flexible ferroelectric organic crystals

    PubMed Central

    Owczarek, Magdalena; Hujsak, Karl A.; Ferris, Daniel P.; Prokofjevs, Aleksandrs; Majerz, Irena; Szklarz, Przemysław; Zhang, Huacheng; Sarjeant, Amy A.; Stern, Charlotte L.; Jakubas, Ryszard; Hong, Seungbum; Dravid, Vinayak P.; Stoddart, J. Fraser

    2016-01-01

    Flexible organic materials possessing useful electrical properties, such as ferroelectricity, are of crucial importance in the engineering of electronic devices. Up until now, however, only ferroelectric polymers have intrinsically met this flexibility requirement, leaving small-molecule organic ferroelectrics with room for improvement. Since both flexibility and ferroelectricity are rare properties on their own, combining them in one crystalline organic material is challenging. Herein, we report that trisubstituted haloimidazoles not only display ferroelectricity and piezoelectricity—the properties that originate from their non-centrosymmetric crystal lattice—but also lend their crystalline mechanical properties to fine-tuning in a controllable manner by disrupting the weak halogen bonds between the molecules. This element of control makes it possible to deliver another unique and highly desirable property, namely crystal flexibility. Moreover, the electrical properties are maintained in the flexible crystals. PMID:27734829

  8. Flexible ferroelectric organic crystals

    NASA Astrophysics Data System (ADS)

    Owczarek, Magdalena; Hujsak, Karl A.; Ferris, Daniel P.; Prokofjevs, Aleksandrs; Majerz, Irena; Szklarz, Przemysław; Zhang, Huacheng; Sarjeant, Amy A.; Stern, Charlotte L.; Jakubas, Ryszard; Hong, Seungbum; Dravid, Vinayak P.; Stoddart, J. Fraser

    2016-10-01

    Flexible organic materials possessing useful electrical properties, such as ferroelectricity, are of crucial importance in the engineering of electronic devices. Up until now, however, only ferroelectric polymers have intrinsically met this flexibility requirement, leaving small-molecule organic ferroelectrics with room for improvement. Since both flexibility and ferroelectricity are rare properties on their own, combining them in one crystalline organic material is challenging. Herein, we report that trisubstituted haloimidazoles not only display ferroelectricity and piezoelectricity--the properties that originate from their non-centrosymmetric crystal lattice--but also lend their crystalline mechanical properties to fine-tuning in a controllable manner by disrupting the weak halogen bonds between the molecules. This element of control makes it possible to deliver another unique and highly desirable property, namely crystal flexibility. Moreover, the electrical properties are maintained in the flexible crystals.

  9. Synthesis and Characterization of Novel Ferromagnetic, Ferroelectric, Single Phase and Composite Multiferroic Mesoporous Materials

    NASA Astrophysics Data System (ADS)

    Quickel, Thomas Eugene

    Mesoporous nanostructures offer facile routes to novel materials with interesting and often unparalleled properties. Ferrimagnetic, ferroelectric and multiferroic phases, the latter comprising materials that simultaneously possess multiple order parameters, are of great technological importance. Developments in our knowledge of and ability to produce new materials exploiting their properties could have fundamental impacts. Employing versatile solution phase chemistry techniques utilizing co-assembly between organic block co-polymers and inorganic metal precursors, we are able to produce 3-dimensional porous nano-structures in thin film format. Mesoporous frameworks comprising various magnetic ferrites are explored in chapters 2, 3 & 4. The crystal structure and nanoscale architecture for each material is thoroughly examined, and the effects of mesoporosity on the magnetic characteristics of the individual ferrites are determined. The ferrites investigated (MFe2O4,M=Co, Zn, Ni, Mg) are magnetostrictive as their magnet moments are subject to change upon straining of the crystal lattice. It was observed that the nano-scale architecture imparts novel strain states on to the polycrystalline phases and spin re-orientation of their magnetic moment results, emulating results that, previous to the finding in this study, were exclusive to epitaxial growth techniques. Furthermore, the presence of high surface area, resulting from mesoporosity, increases surface spin states drastically altering the magnetic functionality of porous ferrites versus their bulk counterparts. The effects of mesoporosity on piezoelectric materials was also investigated. Piezoelectrics comprise a fascinating class of materials that exhibit internal creation of charge upon the action of mechanical strain, the reverse of which is also true. Mesoporous piezoelectric phases were successfully prepared, and the effects of porosity on the ferroelectric order paramter were established. The presence of pores

  10. Doubling the electrocaloric cooling of poled ferroelectric materials by bipolar cycling

    NASA Astrophysics Data System (ADS)

    Basso, Vittorio; Gerard, Jean-François; Pruvost, Sébastien

    2014-08-01

    We have investigated the entropy change in the ferroelectric phase of poly(vinylidene fluoride-trifluoroethylene) 70/30 films by direct heat flux calorimetry using Peltier cell heat flux sensors. We find that by applying a negative electric field to a positively poled state, the entropy can be further increased without any significantly change of the remanent polarization or the domain structure. By cycling between positive and negative values of the electric field, the electrocaloric effect (ECE) can be then improved by a factor of 2. As an example, we measured, around the positive remanence Pr = 60 × 10-3 C m-2, a fully reversible entropy change |Δs| = 1 J kg-1K-1 for a field change from 40 × 106 to -40 × 106 V m-1 and a maximum of |Δs| = 3.2 J kg-1K-1 for an asymmetric field change from 200 × 106 to -40 × 106 V m-1. This effect can be exploited to significantly increase the range of operating temperature for ECE materials below their Curie temperature.

  11. Ferroelectric Light Control Device

    NASA Technical Reports Server (NTRS)

    Park, Yeonjoon (Inventor); Choi, Sang H. (Inventor); King, Glen C. (Inventor); Kim, Jae-Woo (Inventor); Elliott, Jr., James R. (Inventor)

    2008-01-01

    A light control device is formed by ferroelectric material and N electrodes positioned adjacent thereto to define an N-sided regular polygonal region or circular region there between where N is a multiple of four.

  12. Nanomechanics of Ferroelectric Thin Films and Heterostructures

    SciTech Connect

    Li, Yulan; Hu, Shenyang Y.; Chen , L.Q.

    2016-08-31

    The focus of this chapter is to provide basic concepts of how external strains/stresses altering ferroelectric property of a material and how to evaluate quantitatively the effect of strains/stresses on phase stability, domain structure, and material ferroelectric properties using the phase-field method. The chapter starts from a brief introduction of ferroelectrics and the Landau-Devinshire description of ferroelectric transitions and ferroelectric phases in a homogeneous ferroelectric single crystal. Due to the fact that ferroelectric transitions involve crystal structure change and domain formation, strains and stresses can be produced inside of the material if a ferroelectric transition occurs and it is confined. These strains and stresses affect in turn the domain structure and material ferroelectric properties. Therefore, ferroelectrics and strains/stresses are coupled to each other. The ferroelectric-mechanical coupling can be used to engineer the material ferroelectric properties by designing the phase and structure. The followed section elucidates calculations of the strains/stresses and elastic energy in a thin film containing a single domain, twinned domains to complicated multidomains constrained by its underlying substrate. Furthermore, a phase field model for predicting ferroelectric stable phases and domain structure in a thin film is presented. Examples of using substrate constraint and temperature to obtain interested ferroelectric domain structures in BaTiO3 films are demonstrated b phase field simulations.

  13. Atomic layer deposition of environmentally benign SnTiO{sub x} as a potential ferroelectric material

    SciTech Connect

    Chang, Siliang; Selvaraj, Sathees Kannan; Choi, Yoon-Young; Hong, Seungbum; Nakhmanson, Serge M.; Takoudis, Christos G.

    2016-01-15

    Inspired by the need to discover environmentally friendly, lead-free ferroelectric materials, here the authors report the atomic layer deposition of tin titanate (SnTiO{sub x}) aiming to obtain the theoretically predicted perovskite structure that possesses ferroelectricity. In order to establish the growth conditions and probe the film structure and ferroelectric behavior, the authors grew SnTiO{sub x} films on the commonly used Si(100) substrate. Thin films of SnTiO{sub x} have been successfully grown at a deposition temperature of 200 °C, with a Sn/Ti atomic layer deposition (ALD) cycle ratio of 2:3 and postdeposition heat treatments under different conditions. X-ray photoelectron spectroscopy revealed excellent composition tunability of ALD. X-ray diffraction spectra suggested anatase phase for all films annealed at 650 and 350 °C, with peak positions shifted toward lower 2-theta angles indicating enlarged unit cell volume. The film annealed in O{sub 2} at 350 °C exhibited piezoresponse amplitude and phase hysteresis loops, indicative of the existence of switchable polarization.

  14. Application of the Wang-Landau Monte-Carlo Formalism applied to Ferroelectrics materials

    NASA Astrophysics Data System (ADS)

    Bin Omran, Saad; Kornev, Igor; Bellaiche, Laurent

    The conventional description of phase transitions in ferroelectrics is based on canonical thermodynamic functions and always assumes the thermodynamic limit of an infinite system. However, ferroelectrics at nanoscale recently became of high interest due to their potential applications in minuaturized devices. It is this timely and more appropriate to use the microcanonical ensemble when mimicking ferroelectric systems. Interestingly, a Monte Carlo method based on the density of states (or microcanonical ensemble partition function) proposed by Wang and Landau has the potential to over-come these difficulties. Here, the Wang-Landau Monte Carlo algorithm is implemented within an effective Hamiltonian approach and used to conduct a detailed study of physical properties of BaTiO3 bulk. In this presentation, we will show how this approach allows a highly-accurate and straightforward calculation of various thermodynamic properties, including phase transition temperatures, as well as polarization, dielectric susceptibility, specific heat and electrocaloric coefficient at any temperature.

  15. Ferroelectric Pump

    NASA Technical Reports Server (NTRS)

    Jalink, Antony, Jr. (Inventor); Hellbaum, Richard F. (Inventor); Rohrbach, Wayne W. (Inventor)

    2000-01-01

    A ferroelectric pump has one or more variable volume pumping chambers internal to a housing. Each chamber has at least one wall comprising a dome shaped internally prestressed ferroelectric actuator having a curvature and a dome height that varies with an electric voltage applied between an inside and outside surface of the actuator. A pumped medium flows into and out of each pumping chamber in response to displacement of the ferroelectric actuator. The ferroelectric actuator is mounted within each wall and isolates each ferroelectric actuator from the pumped medium, supplies a path for voltage to be applied to each ferroelectric actuator, and provides for positive containment of each ferroelectric actuator while allowing displacement of the entirety of each ferroelectric actuator in response to the applied voltage.

  16. Origin of Room Temperature Ferromagnetism in Cr-Doped Lead-Free Ferroelectric Bi0.5Na0.5TiO3 Materials

    NASA Astrophysics Data System (ADS)

    Thanh, L. T. H.; Doan, N. B.; Dung, N. Q.; Cuong, L. V.; Bac, L. H.; Duc, N. A.; Bao, P. Q.; Dung, D. D.

    2017-01-01

    The development of multiferroic materials based on lead-free ferroelectric material provides an opportunity to fabricate next-generation electronic devices. In this work, Cr-doped lead-free ferroelectric Bi0.5Na0.5TiO3 materials were synthesized by using the sol-gel method. The optical band gap was reduced from 3.12 eV to 2.12 eV for undoped and 9 mol.% Cr-doped Bi0.5Na0.5TiO3 with the substitution of Cr at the Ti-site. Cr-doped Bi0.5Na0.5TiO3 materials exhibited weak ferromagnetism at room temperature. Saturation magnetization was approximately 0.08 μ B/Cr at 5 K. Our work will facilitate the further understanding of the role of transition metal ferromagnetism in lead-free ferroelectric materials at room temperature.

  17. Heterostructure of ferromagnetic and ferroelectric materials with magneto-optic and electro-optic effects

    NASA Technical Reports Server (NTRS)

    Zou, Yingyin Kevin (Inventor); Jiang, Hua (Inventor); Li, Kewen Kevin (Inventor); Guo, Xiaomei (Inventor)

    2012-01-01

    A heterostructure of multiferroics or magnetoelectrics (ME) was disclosed. The film has both ferromagnetic and ferroelectric properties, as well as magneto-optic (MO) and electro-optic (EO) properties. Oxide buffer layers were employed to allow grown a cracking-free heterostructure a solution coating method.

  18. Introduction to the IEEE International Symposium on Applications of Ferroelectrics and International Symposium on Piezoresponse Force Microscopy and Nanoscale Phenomena in Polar Materials.

    PubMed

    Ye, Zuo-Guang; Tan, Xiaoli; Bokov, Alexei A

    2012-09-01

    The 20th IEEE International Symposium on Applications of Ferroelectrics (ISAF) was held on July 24-27, 2011, in Vancouver, British Columbia, Canada, jointly with the International Symposium on Piezoresponse Force Microscopy and Nanoscale Phenomena in Polar Materials (PFM). Over a period of four days, approximately 400 scientists, engineers, and students from around the world presented their work and discussed the latest developments in the field of ferroelectrics, related materials, and their applications. It is particularly encouraging to see that a large number of students (115) were attracted to the joint conference and presented high-quality research works. This trend is not only important to this conference series, but more importantly, it is vital to the future of the ferroelectrics field.

  19. Dielectric and Elastic Properties of Mixed Ferroelectric Material Potassium TANTALUM(1-X) Niobium(x) Oxide

    NASA Astrophysics Data System (ADS)

    Wang, Xiaomei

    Ferroelectricity is one of the important fields in solid state physics because of its scientific and technological significance. This dissertation describes dielectric and elastic properties of the ferroelectric system KTa_{1-x}Nb_{x}O _3 (KTN) with niobium in the concentration range 1.2% ~ 16%. The occurrence and the nature of the phase transition in mixed ferroelectric systems is an intriguing topic due to the introduction of configurational disorder. Experimental results have shown that the critical temperature T _{c} in the KTN system strongly depends on the concentration of Nb and that the transverse optic soft mode frequency decreases as the concentration of Nb increases. However, the origin of the phase transition in this system is not clearly known. In particular, it is not yet clear whether or not the transition is driven by a soft mode and how the nature of the transition evolves as the Nb concentration is changed. This dissertation describes experimental work on the dielectric and elastic behaviors of the KTN system. The results on the linear and the nonlinear dielectric constants and on the electric polarization of KTN reveal (a) the occurrence of a structural transition with the appearance of ferroelectric macroregions at T_{c }, even for relatively low impurity concentrations (b) the presence of polar microregions significantly above T_{c}. The phase transition in KTN is driven by the interaction between effective dipolar moments d* rather than a soft mode. Our experimental results also reveal the coexistence of both dipolar glass like and ferroelectric behaviors in KTN with low Nb concentrations. Elastic results obtained on KTN provide direct evidence of the two distinct stages which the transition go through when approaching the critical temperature T _{c}. The ultrasonic measurements of the longitudinal elastic constant C_ {11} shows the softening of C _{11} with a (T-T_ {c})^{-mu} dependence at intermediate temperature in the first stage. In the

  20. Extension of thickness-dependent dielectric breakdown law on adiabatically compressed ferroelectric materials

    NASA Astrophysics Data System (ADS)

    Shkuratov, Sergey I.; Baird, Jason; Talantsev, Evgueni F.

    2013-02-01

    It is experimentally found that the Eb(d) = γ . d-ξ law describing the thickness-dependent breakdown electric field for solid dielectrics at ambient conditions can be extended for dielectrics in other thermodynamic states. It follows from the experimental results reported herein that the breakdown field, Eb(d), of Pb(Zr0.95Ti0.05)O3 (PZT 95/5) and Pb(Zr0.52Ti0.48)O3 (PZT 52/48) ferroelectrics subjected to explosive adiabatic compression obeys the above-mentioned law in a wide range of voltages, up to 150 kV.

  1. Toluene decomposition by DBD-type plasma combined with metal oxide catalysts supported on ferroelectric materials.

    PubMed

    Jeong, Jin Guk; Lee, Hyeong Seok; Kang, Youngjin; Lee, Ki Bong; Yoo, Jung Whan

    2013-06-01

    We investigated toluene decomposition with a single-stage plasma catalytic system operated at atmospheric pressure and working at reduced temperature (T < 75 degrees C), where a synergistic catalyst was integrated on ferroelectric BaTiO3 beads with a high dielectric constant. The catalyst species were characterized by FE-SEM and XPS before and after the experiment. The MnO2/BaTiO3 catalyst showed high stability in igniting plasma during destruction of toluene for 230 hours in a lifetime test.

  2. Effective nanometer airgap of NEMS devices using negative capacitance of ferroelectric materials.

    PubMed

    Masuduzzaman, Muhammad; Alam, Muhammad Ashraful

    2014-06-11

    Nanoelectromechnical system (NEMS) is seen as one of the most promising candidates for next generation extreme low power electronics that can operate as a versatile switch/memory/sensor/display element. One of the main challenges toward this goal lies in the fabrication difficulties of ultrascaled NEMS required for high density integrated circuits. It is generally understood that fabricating and operating a NEMS with an airgap below a few nanometer will be extremely challenging due to surface roughness, nonideal forces, tunneling, etc. Here, we show that by cascading a NEMS with a ferroelectric capacitor, operating in the negative capacitance regime, the effective airgap can be reduced by almost an order of magnitude, without the need to reduce the airgap physically. This would not only reduce the pull-in voltage to sub-1 V regime, but also would offer a set of characteristics which are difficult/impossible to achieve otherwise. For example, one can reduce/increase the classical travel range, flip the traditional stable-unstable regime of the electrode, get a negative pull-out voltage, and thus, center the hysteresis around zero volt. Moreover, one can also operate the combination as an effective ferroelectric memory with much reduced switching voltages. These characteristics promise dramatic saving in power for NEMS-based switching, memory, and other related applications.

  3. Extension of thickness-dependent dielectric breakdown law on adiabatically compressed ferroelectric materials

    SciTech Connect

    Shkuratov, Sergey I.; Baird, Jason; Talantsev, Evgueni F.

    2013-02-04

    It is experimentally found that the E{sub b}(d) = {gamma} {center_dot} d{sup -{xi}} law describing the thickness-dependent breakdown electric field for solid dielectrics at ambient conditions can be extended for dielectrics in other thermodynamic states. It follows from the experimental results reported herein that the breakdown field, E{sub b}(d), of Pb(Zr{sub 0.95}Ti{sub 0.05})O{sub 3} (PZT 95/5) and Pb(Zr{sub 0.52}Ti{sub 0.48})O{sub 3} (PZT 52/48) ferroelectrics subjected to explosive adiabatic compression obeys the above-mentioned law in a wide range of voltages, up to 150 kV.

  4. Thin layer composite unimorph ferroelectric driver and sensor

    NASA Technical Reports Server (NTRS)

    Hellbaum, Richard F. (Inventor); Bryant, Robert G. (Inventor); Fox, Robert L. (Inventor); Jalink, Jr., Antony (Inventor); Rohrbach, Wayne W. (Inventor); Simpson, Joycelyn O. (Inventor)

    2004-01-01

    A method for forming ferroelectric wafers is provided. A prestress layer is placed on the desired mold. A ferroelectric wafer is placed on top of the prestress layer. The layers are heated and then cooled, causing the ferroelectric wafer to become prestressed. The prestress layer may include reinforcing material and the ferroelectric wafer may include electrodes or electrode layers may be placed on either side of the ferroelectric layer. Wafers produced using this method have greatly improved output motion.

  5. Ferroelectric Based Technologies for Accelerators

    SciTech Connect

    Kanareykin, A.; Jing, C.; Nenasheva, E.; Kazakov, S.; Tagantsev, A.; Yakovlev, V.

    2009-01-22

    Ferroelectrics have unique intrinsic properties that make them extremely attractive for high-energy accelerator applications. Low loss ferroelectric materials can be used as key elements in RF tuning and phase shifting components to provide fast, electronic control. These devices are under development for different accelerator applications for the X, Ka and L-frequency bands. The exact design of these devices depends on the electrical parameters of the particular ferroelectric material to be used--its dielectric constant, loss tangent and tunability. BST based ferroelectric-oxide compounds have been found to be suitable materials for a fast electrically-controlled tuners. We present recent results on the development of BST based ferroelectric compositions synthesized for use in high power technology components. The BST(M) ferroelectrics have been tested using both transverse and parallel dc bias fields to control the permittivity. Fast switching of a newly developed material has been shown and the feasibility of using of ferroelectric-based accelerator components in vacuum and in air has been demonstrated.

  6. Pathways towards ferroelectricity in hafnia

    NASA Astrophysics Data System (ADS)

    Huan, Tran Doan; Sharma, Vinit; Rossetti, George A.; Ramprasad, Rampi

    2014-08-01

    The question of whether one can systematically identify (previously unknown) ferroelectric phases of a given material is addressed, taking hafnia (HfO2) as an example. Low free energy phases at various pressures and temperatures are identified using a first-principles based structure search algorithm. Ferroelectric phases are then recognized by exploiting group theoretical principles for the symmetry-allowed displacive transitions between nonpolar and polar phases. Two orthorhombic polar phases occurring in space groups Pca21 and Pmn21 are singled out as the most viable ferroelectric phases of hafnia, as they display low free energies (relative to known nonpolar phases), and substantial switchable spontaneous electric polarization. These results provide an explanation for the recently observed surprising ferroelectric behavior of hafnia, and reveal pathways for stabilizing ferroelectric phases of hafnia as well as other compounds.

  7. Anomalously rotary polarization discovered in homochiral organic ferroelectrics

    NASA Astrophysics Data System (ADS)

    Li, Peng-Fei; Tang, Yuan-Yuan; Wang, Zhong-Xia; Ye, Heng-Yun; You, Yu-Meng; Xiong, Ren-Gen

    2016-11-01

    Molecular ferroelectrics are currently an active research topic in the field of ferroelectric materials. As complements or alternatives of conventional inorganic ferroelectrics, they have been designed to realize various novel properties, ranging from multiferroicity and semiconductive ferroelectricity to ferroelectric photovoltaics and ferroelectric luminescence. The stabilizing of ferroelectricity in various systems is owing to the flexible tailorability of the organic components. Here we describe the construction of optically active molecular ferroelectrics by introducing homochiral molecules as polar groups. We find that the ferroelectricity in (R)-(-)-3-hydroxlyquinuclidinium halides is due to the alignment of the homochiral molecules. We observe that both the specific optical rotation and rotatory direction change upon paraelectric-ferroelectric phase transitions, due to the existence of two origins from the molecular chirality and spatial arrangement, whose contributions vary upon the transitions. The optical rotation switching effect may find applications in electro-optical elements.

  8. Ferroelectric infrared detector and method

    DOEpatents

    Lashley, Jason Charles; Opeil, Cyril P.; Smith, James Lawrence

    2010-03-30

    An apparatus and method are provided for sensing infrared radiation. The apparatus includes a sensor element that is positioned in a magnetic field during operation to ensure a .lamda. shaped relationship between specific heat and temperature adjacent the Curie temperature of the ferroelectric material comprising the sensor element. The apparatus is operated by inducing a magnetic field on the ferroelectric material to reduce surface charge on the element during its operation.

  9. PREFACE: 12th Russia/CIS/Baltic/Japan Symposium on Ferroelectricity and 9th International Conference on Functional Materials and Nanotechnologies (RCBJSF-2014-FM&NT)

    NASA Astrophysics Data System (ADS)

    Sternberg, Andris; Grinberga, Liga; Sarakovskis, Anatolijs; Rutkis, Martins

    2015-03-01

    The joint International Symposium RCBJSF-2014-FM&NT successfully has united two international events - 12th Russia/CIS/Baltic/Japan Symposium on Ferroelectricity (RCBJSF-12) and 9th International Conference Functional Materials and Nanotechnologies (FM&NT-2014). The RCBJSF symposium is a continuation of series of meetings on ferroelectricity, the first of which took place in Novosibirsk (USSR) in 1976. FM&NT conferences started in 2006 and have been organized by Institute of Solid State Physics, University of Latvia in Riga. In 2012 the International program committee decided to transform this conference into a traveling Baltic State conference and the FM&NT-2013 was organized by the Institute of Physics, University of Tartu, Estonia. In 2014 the joint international symposium RCBJSF-2014-FM&NT was organized by the Institute of Solid State Physics, University of Latvia and was part of Riga - 2014, the European Capital of Culture event. The purpose of the joint Symposium was to bring together scientists, students and high-level experts in solid state physics, materials science, engineering and related disciplines. The number of the registered participants from 26 countries was over 350. During the Symposium 128 high quality scientific talks (5 plenary, 42 invited, 81 oral) and over 215 posters were presented. All presentations were divided into 4 parallel sessions according to 4 main topics of the Symposium: Ferroelectricity, including ferroelectrics and multiferroics, pyroelectrics, piezoelectrics and actuators, integrated ferroelectrics, relaxors, phase transitions and critical phenomena. Multifunctional Materials, including theory, multiscale and multiphenomenal material modeling and simulation, advanced inorganic, organic and hybrid materials. Nanotechnologies, including progressive methods, technologies and design for production, investigation of nano- particles, composites, structures, thin films and coatings. Energy, including perspective materials and

  10. THE FERROELECTRIC AND STRUCTURAL PROPERTIES OF HAFNIUM OXIDE COMPOUNDS,

    DTIC Science & Technology

    HAFNIUM COMPOUNDS, OXIDES), (* FERROELECTRICITY , HAFNIUM COMPOUNDS), (*CRYSTAL STRUCTURE, HAFNIUM COMPOUNDS), DIELECTRIC PROPERTIES, HYSTERESIS... FERROELECTRIC MATERIALS, SOLID SOLUTIONS, X RAY DIFFRACTION, CRYSTAL LATTICES, LOW TEMPERATURE, CALCIUM COMPOUNDS, STRONTIUM COMPOUNDS, LEAD COMPOUNDS, BARIUM COMPOUNDS

  11. Ferroelectric HfO2 for Emerging Ferroelectric Semiconductor Devices

    NASA Astrophysics Data System (ADS)

    Florent, Karine

    The spontaneous polarization in ferroelectrics (FE) makes them particularly attractive for non-volatile memory and logic applications. Non-volatile FRAM memories using perovskite structure materials, such as Lead Zirconate Titanate (PZT) and Strontium Bismuth Tantalate (SBT) have been studied for many years. However, because of their scaling limit and incompatibility with CMOS beyond 130 nm node, floating gate Flash memory technology has been preferred for manufacturing. The recent discovery of ferroelectricity in doped HfO2 in 2011 has opened the door for new ferroelectric based devices compatible with CMOS technology, such as Ferroelectric Field Effect Transistor (FeFET) and Ferroelectric Tunnel Junctions (FTJ). This work began with developing ferroelectric hysteresis characterization capabilities at RIT. Initially reactively sputtered aluminum doped HfO 2 films were investigated. It was observed that the composition control using co-sputtering was not achievable within the existing capabilities. During the course of this study, collaboration was established with the NaMLab group in Germany to investigate Si doped HfO2 deposited by Atomic Layer Deposition (ALD). Metal Ferroelectric Metal (MFM) devices were fabricated using TiN as the top and bottom electrode with Si:HfO2 thickness ranging from 6.4 nm to 22.9 nm. The devices were electrically tested for P-E, C-V and I-V characteristics. Structural characterizations included TEM, EELS, XRR, XRD and XPS/Auger spectroscopy. Higher remanant polarization (Pr) was observed for films of 9.3 nm and 13.1 nm thickness. Thicker film (22.9 nm) showed smaller Pr. Devices with 6.4 nm thick films exhibit tunneling behavior showing a memristor like I-V characteristics. The tunnel current and ferroelectricity showed decrease with cycling indicating a possible change in either the structure or the domain configurations. Theoretical simulations using the improved FE model were carried out to model the ferroelectric behavior of

  12. Domains in Ferroelectric Nanostructures

    NASA Astrophysics Data System (ADS)

    Gregg, Marty

    2010-03-01

    Ferroelectric materials have great potential in influencing the future of small scale electronics. At a basic level, this is because ferroelectric surfaces are charged, and so interact strongly with charge-carrying metals and semiconductors - the building blocks for all electronic systems. Since the electrical polarity of the ferroelectric can be reversed, surfaces can both attract and repel charges in nearby materials, and can thereby exert complete control over both charge distribution and movement. It should be no surprise, therefore, that microelectronics industries have already looked very seriously at harnessing ferroelectric materials in a variety of applications, from solid state memory chips (FeRAMs) to field effect transistors (FeFETs). In all such applications, switching the direction of the polarity of the ferroelectric is a key aspect of functional behavior. The mechanism for switching involves the field-induced nucleation and growth of domains. Domain coarsening, through domain wall propagation, eventually causes the entire ferroelectric to switch its polar direction. It is thus the existence and behavior of domains that determine the switching response, and ultimately the performance of the ferroelectric device. A major issue, associated with the integration of ferroelectrics into microelectronic devices, has been that the fundamental properties associated with ferroelectrics, when in bulk form, appear to change quite dramatically and unpredictably when at the nanoscale: new modes of behaviour, and different functional characteristics from those seen in bulk appear. For domains, in particular, the proximity of surfaces and boundaries have a dramatic effect: surface tension and depolarizing fields both serve to increase the equilibrium density of domains, such that minor changes in scale or morphology can have major ramifications for domain redistribution. Given the importance of domains in dictating the overall switching characteristics of a device

  13. Elastocaloric effect in ferroelectric ceramics

    NASA Astrophysics Data System (ADS)

    Chauhan, Aditya; Patel, Satyanarayan; Vaish, Rahul

    2015-04-01

    Elastocaloric effect has been experimentally demonstrated in bulk (Ba0.85Ca0.15)(Zr0.1Ti0.9)O3 polycrystalline ferroelectric material. Predictions were made using Maxwell's relationship for elastocaloric effect. A maximum elastocaloric effect of 1.55 K was observed for an initial material temperature of 340 K and applied compressive stress of 0-250 MPa (under a constant electric field of 2 MV m-1). The reported value is several times larger than the peak electrocaloric effect for the same material. The results indicate that ferroelectric materials possess a huge potential for elastocaloric refrigeration.

  14. Effects of oxygen ion irradiation on PMN-PT ferroelectric materials for space applications

    NASA Astrophysics Data System (ADS)

    Guggilla, Padmaja; Batra, A. K.; Powell, Rachel

    2016-09-01

    Lead magnesium niobate-lead titanate (PMN-PT) is an important and high performance piezoelectric and pyroelectric relaxor material having wide range of applications in infrared sensor devices. Present work studies the fabrication and dielectric characteristics of PMN-PT in the bulk form. The PMN-PT bulk material was prepared in sol-gel method and subsequently irradiated with heavy ion oxygen. The materials were analyzed and determined that the relaxorferroelectric material indicated changes in its dielectric constant and pyroelectric coefficient after irradiation. Due to the radiation fluent of 1×1016 ions/cm2, the dielectric constant of the material increased uniformly, while its pyroelectric coefficient showed a sharp increased to the value of 5×10-9 μC/cm2 °C with increase in temperature. Its dielectric constants showed increase in values of 527 μC/cm2 °C at 50°C, 635 μC/cm2 °C at 60°C and 748 μC/cm2 °C at 70°C. Properties such as the material impedance, admittance and modulus were investigated for changes in properties which became evident after irradiation.

  15. Materials Research of Novel Organic Piezoelectric/Ferroelectric Compounds at a H.S.I

    DTIC Science & Technology

    2015-07-06

    compounds such as chlorine gas and ammonia gas. These considerations seriously restrict when this material can be prepared (limited to summer months only...are duplicating the procedures of Serratosa3 for this synthesis. This synthesis requires the use of compounds such as chlorine gas and ammonia gas

  16. Differentiating Ferroelectric and Nonferroelectric Electromechanical Effects with Scanning Probe Microscopy

    DOE PAGES

    Balke, Nina; Maksymovych, Petro; Jesse, Stephen; ...

    2015-06-02

    Ferroelectricity in functional materials remains one of the most fascinating areas of modern science in the past several decades. In the last several years, the rapid development of piezoresponse force microscopy (PFM) and spectroscopy revealed the presence of electromechanical hysteresis loops and bias-induced remnant polar states in a broad variety of materials including many inorganic oxides, polymers, and biosystems. In many cases, this behavior was interpreted as the ample evidence for ferroelectric nature of the system. Here, we systematically analyze PFM responses on ferroelectric and nonferroelectric materials and demonstrate that mechanisms unrelated to ferroelectricity can induce ferroelectric-like characteristics through chargemore » injection and electrostatic forces on the tip. In this paper, we will focus on similarities and differences in various PFM measurement characteristics to provide an experimental guideline to differentiate between ferroelectric material properties and charge injection. In conclusion, we apply the developed measurement protocols to an unknown ferroelectric material.« less

  17. Differentiating Ferroelectric and Nonferroelectric Electromechanical Effects with Scanning Probe Microscopy

    SciTech Connect

    Balke, Nina; Maksymovych, Petro; Jesse, Stephen; Herklotz, Andreas; Tselev, Alexander; Eom, Chang-Beom; Kravchenko, Ivan I.; Yu, Pu; Kalinin, Sergei V.

    2015-06-02

    Ferroelectricity in functional materials remains one of the most fascinating areas of modern science in the past several decades. In the last several years, the rapid development of piezoresponse force microscopy (PFM) and spectroscopy revealed the presence of electromechanical hysteresis loops and bias-induced remnant polar states in a broad variety of materials including many inorganic oxides, polymers, and biosystems. In many cases, this behavior was interpreted as the ample evidence for ferroelectric nature of the system. Here, we systematically analyze PFM responses on ferroelectric and nonferroelectric materials and demonstrate that mechanisms unrelated to ferroelectricity can induce ferroelectric-like characteristics through charge injection and electrostatic forces on the tip. In this paper, we will focus on similarities and differences in various PFM measurement characteristics to provide an experimental guideline to differentiate between ferroelectric material properties and charge injection. In conclusion, we apply the developed measurement protocols to an unknown ferroelectric material.

  18. Combinatorial approach for ferroelectric material libraries prepared by liquid source misted chemical deposition method

    PubMed Central

    Kim, Ki Woong; Jeon, Min Ku; Oh, Kwang Seok; Kim, Tai Suk; Kim, Yun Seok; Woo, Seong Ihl

    2007-01-01

    Combinatorial approach for discovering novel functional materials in the huge diversity of chemical composition and processing conditions has become more important for breakthrough in thin film electronic and energy-conversion devices. The efficiency of combinatorial method depends on the preparation of a reliable high-density composition thin-film library. The physico-chemical properties of each sample on the library should be similar to those of the corresponding samples prepared by one-by-one conventional methods. We successfully developed the combinatorial liquid source misted chemical deposition (LSMCD) method and demonstrated its validity in screening the chemical composition of Bi3.75LaxCe0.25-xTi3O12 (BLCT) for high remanent polarization (Pr). LSMCD is a cheap promising combinatorial screening tool. It can control the composition up to ppm level and produce homogeneous multicomponent library. LSMCD method allows us to prepare BLCT thin-film library at the variation of 0.4 mol% of La. Maximum 2Pr is 35 μC/cm−2 at x = 0.21. The intensity of (117) XRD peak is quantitatively related to 2Pr. Newly developed scanning piezoelectric deformation measurement for nano-sized samples using scanning probe microscope (SPM) is also found out to be reliable for determining the relative ranking of Pr value rapidly. PMID:17218453

  19. Strong anisotropy of ferroelectricity in lead-free bismuth silicate

    NASA Astrophysics Data System (ADS)

    Seol, Daehee; Taniguchi, Hiroki; Hwang, Jae-Yeol; Itoh, Mitsuru; Shin, Hyunjung; Kim, Sung Wng; Kim, Yunseok

    2015-07-01

    Bismuth silicate (Bi2SiO5) was recently suggested as a potential silicate based lead-free ferroelectric material. Here, we show the existence of ferroelectricity and explore the strong anisotropy of local ferroelectricity using piezoresponse force microscopy (PFM). Domain structures are reconstructed using angle-resolved PFM. Furthermore, piezoresponse hysteresis loops and piezoelectric coefficients are spatially investigated at the nanoscale. The obtained results confirm the existence of ferroelectricity with strong c-axis polarization. These results could provide basic information on the anisotropic ferroelectricity in Bi2SiO5 and furthermore suggest its considerable potential for lead-free ferroelectric applications with silicon technologies.Bismuth silicate (Bi2SiO5) was recently suggested as a potential silicate based lead-free ferroelectric material. Here, we show the existence of ferroelectricity and explore the strong anisotropy of local ferroelectricity using piezoresponse force microscopy (PFM). Domain structures are reconstructed using angle-resolved PFM. Furthermore, piezoresponse hysteresis loops and piezoelectric coefficients are spatially investigated at the nanoscale. The obtained results confirm the existence of ferroelectricity with strong c-axis polarization. These results could provide basic information on the anisotropic ferroelectricity in Bi2SiO5 and furthermore suggest its considerable potential for lead-free ferroelectric applications with silicon technologies. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr03161c

  20. Photorefractive effect in ferroelectric liquid crystals

    NASA Astrophysics Data System (ADS)

    Sasaki, Takeo; Naka, Yumiko

    2014-03-01

    In this paper, we review recent progress of research on the photorefractive effect of ferroelectric liquid crystals. The photorefractive effect is a phenomenon that forms a dynamic hologram in a material. The interference of two laser beams in a photorefractive material establishes a refractive index grating. This phenomenon is applicable to a wide range of devices related to diffraction optics including 3D displays, optical amplification, optical tomography, novelty filters, and phase conjugate wave generators. Ferroelectric liquid crystals are considered as a candidate for practical photorefractive materials. A refractive index grating formation time of 8-10 ms and a large gain coefficient are easily obtained in photorefractive ferroelectric liquid crystals.

  1. Multiscale modeling for ferroelectric materials: identification of the phase-field model’s free energy for PZT from atomistic simulations

    NASA Astrophysics Data System (ADS)

    Völker, Benjamin; Landis, Chad M.; Kamlah, Marc

    2012-03-01

    Within a knowledge-based multiscale simulation approach for ferroelectric materials, the atomic level can be linked to the mesoscale by transferring results from first-principles calculations into a phase-field model. A recently presented routine (Völker et al 2011 Contin. Mech. Thermodyn. 23 435-51) for adjusting the Helmholtz free energy coefficients to intrinsic and extrinsic ferroelectric material properties obtained by DFT calculations and atomistic simulations was subject to certain limitations: caused by too small available degrees of freedom, an independent adjustment of the spontaneous strains and piezoelectric coefficients was not possible, and the elastic properties could only be considered in cubic instead of tetragonal symmetry. In this work we overcome such restrictions by expanding the formulation of the free energy function, i.e. by motivating and introducing new higher-order terms that have not appeared in the literature before. Subsequently we present an improved version of the adjustment procedure for the free energy coefficients that is solely based on input parameters from first-principles calculations performed by Marton and Elsässer, as documented in Völker et al (2011 Contin. Mech. Thermodyn. 23 435-51). Full sets of adjusted free energy coefficients for PbTiO3 and tetragonal Pb(Zr,Ti)O3 are presented, and the benefits of the newly introduced higher-order free energy terms are discussed.

  2. The Homogenized Energy Model (HEM) for Characterizing Polarization and Strains in Hysteretic Ferroelectric Materials: Material Properties and Uniaxial Model Development

    DTIC Science & Technology

    2012-01-01

    density of α-variant (CV/m 3) P Polarization (C/m2) P Polarization kernel (C/m2) Pα Polarization of α-variant (C/m2) PαR Remanent polarization of α...Permittivity (F/m = C/Vm) ε Strain (Unitless) ε Strain kernel εα Strain of α-variant εαR Remanence strain of α-variant εαm Minimum strain of α-variant γ γ...designates the dipole variant — e.g., ±180, 90 for tetragonal materials — and PαR , εαR are remanent values of the polarization and strain. At larger

  3. Ferroelectric memory based on nanostructures

    PubMed Central

    2012-01-01

    In the past decades, ferroelectric materials have attracted wide attention due to their applications in nonvolatile memory devices (NVMDs) rendered by the electrically switchable spontaneous polarizations. Furthermore, the combination of ferroelectric and nanomaterials opens a new route to fabricating a nanoscale memory device with ultrahigh memory integration, which greatly eases the ever increasing scaling and economic challenges encountered in the traditional semiconductor industry. In this review, we summarize the recent development of the nonvolatile ferroelectric field effect transistor (FeFET) memory devices based on nanostructures. The operating principles of FeFET are introduced first, followed by the discussion of the real FeFET memory nanodevices based on oxide nanowires, nanoparticles, semiconductor nanotetrapods, carbon nanotubes, and graphene. Finally, we present the opportunities and challenges in nanomemory devices and our views on the future prospects of NVMDs. PMID:22655750

  4. 1. Innovative Relaxor-Based PiezoCrystals: Phase Diagrams, Crystal Growth, Domain Structures and Electric Properties. 2. Piezo- and Ferroelectric Materials Based on Morphotropic Phase Boundary Synthesis, Characterization and Structure - Property Relations

    DTIC Science & Technology

    2006-03-31

    Aug. 2-8, 2003. [48] Z.-G. Ye, A. Bokov and M . Maglione , "Dielectric and Structural Properties of Relaxor Ferroelectrics", 55 Years of Ferroelectrics...Pacific Center for Advanced Materials and Microstructure (PCAMM), NRC / UBC, Dec. 4, 2004. [64] A. A. Bokov, M . Maglione and Z.-G. Ye, "Low-Frequency...Argentina, Sept. 5 - 9, 2005. [78] A. A. Bokov, M . Maglione and Z.-G. Ye, "Critical Dielectric Behaviour in Ba(Til-,Zr,)0 3 Solid Solution" (0), 1 1 1h

  5. Ferroelectric Field Effect Transistor Model Using Partitioned Ferroelectric Layer and Partial Polarization

    NASA Technical Reports Server (NTRS)

    MacLeod, Todd C.; Ho, Fat D.

    2004-01-01

    A model of an n-channel ferroelectric field effect transistor has been developed based on both theoretical and empirical data. The model is based on an existing model that incorporates partitioning of the ferroelectric layer to calculate the polarization within the ferroelectric material. The model incorporates several new aspects that are useful to the user. It takes into account the effect of a non-saturating gate voltage only partially polarizing the ferroelectric material based on the existing remnant polarization. The model also incorporates the decay of the remnant polarization based on the time history of the FFET. A gate pulse of a specific voltage; will not put the ferroelectric material into a single amount of polarization for that voltage, but instead vary with previous state of the material and the time since the last change to the gate voltage. The model also utilizes data from FFETs made from different types of ferroelectric materials to allow the user just to input the material being used and not recreate the entire model. The model also allows the user to input the quality of the ferroelectric material being used. The ferroelectric material quality can go from a theoretical perfect material with little loss and no decay to a less than perfect material with remnant losses and decay. This model is designed to be used by people who need to predict the external characteristics of a FFET before the time and expense of design and fabrication. It also allows the parametric evaluation of quality of the ferroelectric film on the overall performance of the transistor.

  6. Multigap Semiconducting ferroelectric perovskites

    NASA Astrophysics Data System (ADS)

    Jiang, Lai; Grinberg, Ilya; Wang, Fenggong; Davies, Peter; Rappe, Andrew

    2013-03-01

    The energy conversion efficiency of a solar cell is directly related to the band gap of the material. By doping ferroelectric perovskites with Bi5+ on the B-site, we propose low band-gap materials suitable for bulk photovoltaic effect and related solar applications.Our DFT calculations indicate that the low-lying 6 s empty states of the electronegative Bi atom produce empty isolated bands in the gap of the parent materials, effectively lowering the band gap by 1 ~2eV in various perovskites. Ferroelectricity (and therefore inversion symmetry breaking) weakens but survives upon doping, which enables the ``shift current'' mechanism for photocurrent generation, while the decreased band gap helps absorb low energy photons in the visible range. Furthermore, the existence of multiple band gaps allows for solar conversion devices with efficiency beyond the traditional Shockly-Queisser limit, in which successive photon excitations result in carriers with higher energy than a single-step excitation would achieve.

  7. Flexoelectric Induced Caloric Effect in Truncated Pyramid Shaped Ba0.67Sr0.33TiO3 Ferroelectric Material

    NASA Astrophysics Data System (ADS)

    Patel, Satyanarayan; Chauhan, Aditya; Madhar, Niyaz Ahamad; Ilahi, Bouraoui; Vaish, Rahul

    2017-02-01

    Solid state refrigeration based on ferroelectric materials can potentially be competing in not-in-kind refrigeration technology. However, their functionality is currently limited to Curie temperatures. Through this article, authors have attempted to describe an unexplored component of the stress-driven caloric effect, obtainable beyond the Curie point. The phenomenon, termed as the flexocaloric effect (FCE), relies on inhomogeneous straining of the crystal lattice to induce polarization in centrosymmetric crystals (flexoelectricity). For this study, a truncated pyramid geometry was selected, and the dependence of sample height on caloric capacity was studied. A peak temperature change of 1.75 K (313 K) was estimated for Ba0.67Sr0.33TiO3 (BST) ceramics employing a truncated pyramid configuration.

  8. SISGR -- Domain Microstructures and Mechanisms for Large, Reversible and Anhysteretic Strain Behaviors in Phase Transforming Ferroelectric Materials

    SciTech Connect

    Wang, Yu U.

    2013-12-06

    This four-year project (including one-year no-cost extension) aimed to advance fundamental understanding of field-induced strain behaviors of phase transforming ferroelectrics. We performed meso-scale phase field modeling and computer simulation to study domain evolutions, mechanisms and engineering techniques, and developed computational techniques for nanodomain diffraction analysis; to further support above originally planned tasks, we also carried out preliminary first-principles density functional theory calculations of point defects and domain walls to complement meso-scale computations as well as performed in-situ high-energy synchrotron X-ray single crystal diffraction experiments to guide theoretical development (both without extra cost to the project thanks to XSEDE supercomputers and DOE user facility Advanced Photon Source).

  9. Negative capacitance in a ferroelectric capacitor.

    PubMed

    Khan, Asif Islam; Chatterjee, Korok; Wang, Brian; Drapcho, Steven; You, Long; Serrao, Claudy; Bakaul, Saidur Rahman; Ramesh, Ramamoorthy; Salahuddin, Sayeef

    2015-02-01

    The Boltzmann distribution of electrons poses a fundamental barrier to lowering energy dissipation in conventional electronics, often termed as Boltzmann Tyranny. Negative capacitance in ferroelectric materials, which stems from the stored energy of a phase transition, could provide a solution, but a direct measurement of negative capacitance has so far been elusive. Here, we report the observation of negative capacitance in a thin, epitaxial ferroelectric film. When a voltage pulse is applied, the voltage across the ferroelectric capacitor is found to be decreasing with time--in exactly the opposite direction to which voltage for a regular capacitor should change. Analysis of this 'inductance'-like behaviour from a capacitor presents an unprecedented insight into the intrinsic energy profile of the ferroelectric material and could pave the way for completely new applications.

  10. A-SITE-AND/OR B-SITE-MODIFIED PBZRTIO3 MATERIALS AND (PB, SR, CA, BA, MG) (ZR, TI,NB, TA)O3 FILMS HAVING UTILITY IN FERROELECTRIC RANDOM ACCESS MEMORIES AND HIGH PERFORMANCE THIN FILM MICROACTUATORS

    NASA Technical Reports Server (NTRS)

    Roeder, Jeffrey F. (Inventor); Chen, Ing-Shin (Inventor); Bilodeau, Steven (Inventor); Baum, Thomas H. (Inventor)

    2004-01-01

    A modified PbZrTiO.sub.3 perovskite crystal material thin film, wherein the PbZrTiO.sub.3 perovskite crystal material includes crystal lattice A-sites and B-sites at least one of which is modified by the presence of a substituent selected from the group consisting of (i) A-site substituents consisting of Sr, Ca, Ba and Mg, and (ii) B-site substituents selected from the group consisting of Nb and Ta. The perovskite crystal thin film material may be formed by liquid delivery MOCVD from metalorganic precursors of the metal components of the thin film, to form PZT and PSZT, and other piezoelectric and ferroelectric thin film materials. The thin films of the invention have utility in non-volatile ferroelectric memory devices (NV-FeRAMs), and in microelectromechanical systems (MEMS) as sensor and/or actuator elements, e.g., high speed digital system actuators requiring low input power levels.

  11. Electrocaloric cooling based on relaxor ferroelectrics

    NASA Astrophysics Data System (ADS)

    Suchaneck, Gunnar; Gerlach, Gerald

    2015-03-01

    In this work, we consider the electrocaloric effect in relaxor ferroelectrics above the temperature of the dielectric constant maximum. For the purpose of modelling, a modified Curie--Weiss law was adapted to approximate the complex physics of relaxors. The requirements to electrocaloric materials derived on this basis are fulfilled by relaxor single crystals, ceramics and high-quality thin films. Relaxor ferroelectrics exhibit a suitable electrocaloric performance starting at applied electric fields of about 25 V/μm.

  12. Patterned piezo-, pyro-, and ferroelectricity of poled polymer electrets

    NASA Astrophysics Data System (ADS)

    Qiu, Xunlin

    2010-07-01

    Polymers with strong piezo-, pyro-, and ferroelectricity are attractive for a wide range of applications. In particular, semicrystalline ferroelectric polymers are suitable for a large variety of piezo- and pyroelectric transducers or sensors, while amorphous polymers containing chromophore molecules are particularly interesting for photonic devices. Recently, a new class of polymer materials has been added to this family: internally charged cellular space-charge polymer electrets (so-called "ferroelectrets"), whose piezoelectricity can be orders of magnitude higher than that of conventional ferroelectric polymers. Suitable patterning of these materials leads to improved or unusual macroscopic piezo-, pyro-, and ferroelectric or nonlinear optical properties that may be particularly useful for advanced transducer or waveguide applications. In the present paper, the piezo-, pyro-, and ferroelectricity of poled polymers is briefly introduced, an overview on the preparation of polymer electrets with patterned piezo-, pyro-, and ferroelectricity is provided and a survey of selected applications is presented.

  13. Lead-free epitaxial ferroelectric material integration on semiconducting (100) Nb-doped SrTiO3 for low-power non-volatile memory and efficient ultraviolet ray detection.

    PubMed

    Kundu, Souvik; Clavel, Michael; Biswas, Pranab; Chen, Bo; Song, Hyun-Cheol; Kumar, Prashant; Halder, Nripendra N; Hudait, Mantu K; Banerji, Pallab; Sanghadasa, Mohan; Priya, Shashank

    2015-07-23

    We report lead-free ferroelectric based resistive switching non-volatile memory (NVM) devices with epitaxial (1-x)BaTiO3-xBiFeO3 (x = 0.725) (BT-BFO) film integrated on semiconducting (100) Nb (0.7%) doped SrTiO3 (Nb:STO) substrates. The piezoelectric force microscopy (PFM) measurement at room temperature demonstrated ferroelectricity in the BT-BFO thin film. PFM results also reveal the repeatable polarization inversion by poling, manifesting its potential for read-write operation in NVM devices. The electroforming-free and ferroelectric polarization coupled electrical behaviour demonstrated excellent resistive switching with high retention time, cyclic endurance, and low set/reset voltages. X-ray photoelectron spectroscopy was utilized to determine the band alignment at the BT-BFO and Nb:STO heterojunction, and it exhibited staggered band alignment. This heterojunction is found to behave as an efficient ultraviolet photo-detector with low rise and fall time. The architecture also demonstrates half-wave rectification under low and high input signal frequencies, where the output distortion is minimal. The results provide avenue for an electrical switch that can regulate the pixels in low or high frequency images. Combined this work paves the pathway towards designing future generation low-power ferroelectric based microelectronic devices by merging both electrical and photovoltaic properties of BT-BFO materials.

  14. Lead-free epitaxial ferroelectric material integration on semiconducting (100) Nb-doped SrTiO3 for low-power non-volatile memory and efficient ultraviolet ray detection

    NASA Astrophysics Data System (ADS)

    Kundu, Souvik; Clavel, Michael; Biswas, Pranab; Chen, Bo; Song, Hyun-Cheol; Kumar, Prashant; Halder, Nripendra N.; Hudait, Mantu K.; Banerji, Pallab; Sanghadasa, Mohan; Priya, Shashank

    2015-07-01

    We report lead-free ferroelectric based resistive switching non-volatile memory (NVM) devices with epitaxial (1-x)BaTiO3-xBiFeO3 (x = 0.725) (BT-BFO) film integrated on semiconducting (100) Nb (0.7%) doped SrTiO3 (Nb:STO) substrates. The piezoelectric force microscopy (PFM) measurement at room temperature demonstrated ferroelectricity in the BT-BFO thin film. PFM results also reveal the repeatable polarization inversion by poling, manifesting its potential for read-write operation in NVM devices. The electroforming-free and ferroelectric polarization coupled electrical behaviour demonstrated excellent resistive switching with high retention time, cyclic endurance, and low set/reset voltages. X-ray photoelectron spectroscopy was utilized to determine the band alignment at the BT-BFO and Nb:STO heterojunction, and it exhibited staggered band alignment. This heterojunction is found to behave as an efficient ultraviolet photo-detector with low rise and fall time. The architecture also demonstrates half-wave rectification under low and high input signal frequencies, where the output distortion is minimal. The results provide avenue for an electrical switch that can regulate the pixels in low or high frequency images. Combined this work paves the pathway towards designing future generation low-power ferroelectric based microelectronic devices by merging both electrical and photovoltaic properties of BT-BFO materials.

  15. Ferroelectric symmetry-protected multibit memory cell

    PubMed Central

    Baudry, Laurent; Lukyanchuk, Igor; Vinokur, Valerii M.

    2017-01-01

    The tunability of electrical polarization in ferroelectrics is instrumental to their applications in information-storage devices. The existing ferroelectric memory cells are based on the two-level storage capacity with the standard binary logics. However, the latter have reached its fundamental limitations. Here we propose ferroelectric multibit cells (FMBC) utilizing the ability of multiaxial ferroelectric materials to pin the polarization at a sequence of the multistable states. Employing the catastrophe theory principles we show that these states are symmetry-protected against the information loss and thus realize novel topologically-controlled access memory (TAM). Our findings enable developing a platform for the emergent many-valued non-Boolean information technology and target challenges posed by needs of quantum and neuromorphic computing. PMID:28176866

  16. Ferroelectric symmetry-protected multibit memory cell

    NASA Astrophysics Data System (ADS)

    Baudry, Laurent; Lukyanchuk, Igor; Vinokur, Valerii M.

    2017-02-01

    The tunability of electrical polarization in ferroelectrics is instrumental to their applications in information-storage devices. The existing ferroelectric memory cells are based on the two-level storage capacity with the standard binary logics. However, the latter have reached its fundamental limitations. Here we propose ferroelectric multibit cells (FMBC) utilizing the ability of multiaxial ferroelectric materials to pin the polarization at a sequence of the multistable states. Employing the catastrophe theory principles we show that these states are symmetry-protected against the information loss and thus realize novel topologically-controlled access memory (TAM). Our findings enable developing a platform for the emergent many-valued non-Boolean information technology and target challenges posed by needs of quantum and neuromorphic computing.

  17. Fracture behavior of ferroelectric ceramics

    NASA Astrophysics Data System (ADS)

    Chen, Wei; Lupascu, Doru C.; Lynch, Christopher S.

    1999-06-01

    Piezoelectric actuators are key components in many smart structures applications. Long term reliability of these actuators becomes increasingly important as research makes the transition to commercial applications. Fracture toughness is a material parameter that measures a material's resistance to crack propagation. This is perhaps, one of the most important parameters for reliable device design. This paper reviews recent work by the authors on fracture behavior of ferroelectric ceramics. Vickers indentation data were used to determine the fracture toughness of a coarse and a fine grained PZT and two compositions of PLZT. R-curve data were obtained for two compositions of PLZT. The R-curve data presented here were generated using four point bend specimens with controlled surface flaws. The R-curve results compare favorably with the Vickers indentation data. A comparison of the R-curves for a ferroelectric composition of PLZT and a quadratic electrostrictive composition of PLZT demonstrate the contribution of domain reorientation to the toughening process.

  18. Ferroelectric domain wall motion induced by polarized light

    PubMed Central

    Rubio-Marcos, Fernando; Del Campo, Adolfo; Marchet, Pascal; Fernández, Jose F.

    2015-01-01

    Ferroelectric materials exhibit spontaneous and stable polarization, which can usually be reoriented by an applied external electric field. The electrically switchable nature of this polarization is at the core of various ferroelectric devices. The motion of the associated domain walls provides the basis for ferroelectric memory, in which the storage of data bits is achieved by driving domain walls that separate regions with different polarization directions. Here we show the surprising ability to move ferroelectric domain walls of a BaTiO3 single crystal by varying the polarization angle of a coherent light source. This unexpected coupling between polarized light and ferroelectric polarization modifies the stress induced in the BaTiO3 at the domain wall, which is observed using in situ confocal Raman spectroscopy. This effect potentially leads to the non-contact remote control of ferroelectric domain walls by light. PMID:25779918

  19. Phonon localization drives polar nanoregions in a relaxor ferroelectric.

    PubMed

    Manley, M E; Lynn, J W; Abernathy, D L; Specht, E D; Delaire, O; Bishop, A R; Sahul, R; Budai, J D

    2014-04-10

    Relaxor ferroelectrics exemplify a class of functional materials where interplay between disorder and phase instability results in inhomogeneous nanoregions. Although known for about 30 years, there is no definitive explanation for polar nanoregions (PNRs). Here we show that ferroelectric phonon localization drives PNRs in relaxor ferroelectric PMN-30%PT using neutron scattering. At the frequency of a preexisting resonance mode, nanoregions of standing ferroelectric phonons develop with a coherence length equal to one wavelength and the PNR size. Anderson localization of ferroelectric phonons by resonance modes explains our observations and, with nonlinear slowing, the PNRs and relaxor properties. Phonon localization at additional resonances near the zone edges explains competing antiferroelectric distortions known to occur at the zone edges. Our results indicate the size and shape of PNRs that are not dictated by complex structural details, as commonly assumed, but by phonon resonance wave vectors. This discovery could guide the design of next generation relaxor ferroelectrics.

  20. Ferroelectric domain engineering and micro-structuring of lithium niobate

    NASA Astrophysics Data System (ADS)

    Mailis, Sakellaris

    2010-11-01

    This paper discusses a number of recently developed all optical and optically assisted methods for ferroelectric domain engineering in lithium niobate and their impact on the micro-structuring of this optical ferroelectric crystal. Optical radiation is used to change the response of lithium niobate crystals to externally applied electric field encouraging or inhibiting ferroelectric domain inversion in a simultaneous or latent manner. Optically assisted poling processes have the advantage of producing ferroelectric domains with arbitrary shapes free from crystal symmetry restrictions which is very important for fabricating surface micro/nano-structures in this material.

  1. Ferroelectric nanostructure having switchable multi-stable vortex states

    DOEpatents

    Naumov, Ivan I.; Bellaiche, Laurent M.; Prosandeev, Sergey A.; Ponomareva, Inna V.; Kornev, Igor A.

    2009-09-22

    A ferroelectric nanostructure formed as a low dimensional nano-scale ferroelectric material having at least one vortex ring of polarization generating an ordered toroid moment switchable between multi-stable states. A stress-free ferroelectric nanodot under open-circuit-like electrical boundary conditions maintains such a vortex structure for their local dipoles when subject to a transverse inhomogeneous static electric field controlling the direction of the macroscopic toroidal moment. Stress is also capable of controlling the vortex's chirality, because of the electromechanical coupling that exists in ferroelectric nanodots.

  2. Organic ferroelectric/semiconducting nanowire hybrid layer for memory storage

    NASA Astrophysics Data System (ADS)

    Cai, Ronggang; Kassa, Hailu G.; Haouari, Rachid; Marrani, Alessio; Geerts, Yves H.; Ruzié, Christian; van Breemen, Albert J. J. M.; Gelinck, Gerwin H.; Nysten, Bernard; Hu, Zhijun; Jonas, Alain M.

    2016-03-01

    Ferroelectric materials are important components of sensors, actuators and non-volatile memories. However, possible device configurations are limited due to the need to provide screening charges to ferroelectric interfaces to avoid depolarization. Here we show that, by alternating ferroelectric and semiconducting nanowires over an insulating substrate, the ferroelectric dipole moment can be stabilized by injected free charge carriers accumulating laterally in the neighboring semiconducting nanowires. This lateral electrostatic coupling between ferroelectric and semiconducting nanowires offers new opportunities to design new device architectures. As an example, we demonstrate the fabrication of an elementary non-volatile memory device in a transistor-like configuration, of which the source-drain current exhibits a typical hysteretic behavior with respect to the poling voltage. The potential for size reduction intrinsic to the nanostructured hybrid layer offers opportunities for the development of strongly miniaturized ferroelectric and piezoelectric devices.Ferroelectric materials are important components of sensors, actuators and non-volatile memories. However, possible device configurations are limited due to the need to provide screening charges to ferroelectric interfaces to avoid depolarization. Here we show that, by alternating ferroelectric and semiconducting nanowires over an insulating substrate, the ferroelectric dipole moment can be stabilized by injected free charge carriers accumulating laterally in the neighboring semiconducting nanowires. This lateral electrostatic coupling between ferroelectric and semiconducting nanowires offers new opportunities to design new device architectures. As an example, we demonstrate the fabrication of an elementary non-volatile memory device in a transistor-like configuration, of which the source-drain current exhibits a typical hysteretic behavior with respect to the poling voltage. The potential for size reduction

  3. Novel Low Cost High Efficiency Tunable RF Devices and Antenna Arrays Design based on the Ferroelectric Materials and the CTS Technologies

    DTIC Science & Technology

    2011-02-14

    Microwave Theory and Techniques,”vol. 55, pp. 402-409, 2007 W. Kim and M. Iskander, "Integrated Phased Array Antenna Design Using Ferroelectric...on Microwaves , Communications, Antennas and Electronic Systems (IEEE COMCAS’09), Tel Aviv, Israel, Nov. 9-11, 2009. W. C. Kim, and m. F. Iskander, “A...Transactions on Microwave Theory and Techniques,”vol. 55, pp. 402-409, (2007) B. "Integrated Phased Array Antenna Design Using Ferroelectric

  4. Elastic Domain Wall Waves in Ferroelectric Ceramics and Single Crystals

    DTIC Science & Technology

    1988-07-01

    and identify by block number) " This report reviews research on acoustic guided waves along poling transitions in counter- poled ferroelectric ceramics...INTRODUCTION........................................ 1 II. GENERAL REVIEW . .. .......... ........... ... 2 (a) COUNTERPOLED CERAMICS...and better understanding of new ferroelectric materials. II. GENERAL REVIEW The initial phase of this project was an in-depth study of elastic wave

  5. Ferroelectric liquid crystal display

    NASA Technical Reports Server (NTRS)

    York, Paul K. (Inventor)

    1977-01-01

    A ferroelectric liquid crystal display device employs capacitance spoiling layers to minimize unneeded capacitances created by crossovers of X and Y address lines and to accurately define desired capacitances. The spoiler layers comprise low dielectric constant layers which space electrodes from the ferroelectric at crossover points where capacitance is not needed for device operation.

  6. Wireless ferroelectric resonating sensor.

    PubMed

    Viikari, Ville; Seppa, Heikki; Mattila, Tomi; Alastalo, Ari

    2010-04-01

    This paper presents a passive wireless resonating sensor that is based on a ferroelectric varactor. The sensor replies with its data at an intermodulation frequency when a reader device illuminates it at 2 closely located frequencies. The paper derives a theoretical equation for the response of such a sensor, verifies the theory by simulations, and demonstrates a temperature sensor based on a ferroelectric varactor.

  7. Super Stable Ferroelectrics with High Curie Point.

    PubMed

    Gao, Zhipeng; Lu, Chengjia; Wang, Yuhang; Yang, Sinuo; Yu, Yuying; He, Hongliang

    2016-04-07

    Ferroelectric materials are of great importance in the sensing technology due to the piezoelectric properties. Thermal depoling behavior of ferroelectrics determines the upper temperature limit of their application. So far, there is no piezoelectric material working above 800 °C available. Here, we show Nd2Ti2O7 with a perovskite-like layered structure has good resistance to thermal depoling up to 1400 °C. Its stable behavior is because the material has only 180° ferroelectric domains, complex structure change at Curie point (Tc) and their sintering temperature is below their Tc, which avoided the internal stresses produced by the unit cell volume change at Tc. The phase transition at Tc shows a first order behavior which involving the tilting and rotation of the octahedron. The Curie - Weiss temperature is calculated, which might explain why the thermal depoling starts at about 1400 °C.

  8. Super Stable Ferroelectrics with High Curie Point

    PubMed Central

    Gao, Zhipeng; Lu, Chengjia; Wang, Yuhang; Yang, Sinuo; Yu, Yuying; He, Hongliang

    2016-01-01

    Ferroelectric materials are of great importance in the sensing technology due to the piezoelectric properties. Thermal depoling behavior of ferroelectrics determines the upper temperature limit of their application. So far, there is no piezoelectric material working above 800 °C available. Here, we show Nd2Ti2O7 with a perovskite-like layered structure has good resistance to thermal depoling up to 1400 °C. Its stable behavior is because the material has only 180° ferroelectric domains, complex structure change at Curie point (Tc) and their sintering temperature is below their Tc, which avoided the internal stresses produced by the unit cell volume change at Tc. The phase transition at Tc shows a first order behavior which involving the tilting and rotation of the octahedron. The Curie – Weiss temperature is calculated, which might explain why the thermal depoling starts at about 1400 °C. PMID:27053338

  9. Ferroelectrics: A pathway to switchable surface chemistry and catalysis

    NASA Astrophysics Data System (ADS)

    Kakekhani, Arvin; Ismail-Beigi, Sohrab; Altman, Eric I.

    2016-08-01

    It has been known for more than six decades that ferroelectricity can affect a material's surface physics and chemistry thereby potentially enhancing its catalytic properties. Ferroelectrics are a class of materials with a switchable electrical polarization that can affect surface stoichiometry and electronic structure and thus adsorption energies and modes; e.g., molecular versus dissociative. Therefore, ferroelectrics may be utilized to achieve switchable surface chemistry whereby surface properties are not fixed but can be dynamically controlled by, for example, applying an external electric field or modulating the temperature. Several important examples of applications of ferroelectric and polar materials in photocatalysis and heterogeneous catalysis are discussed. In photocatalysis, the polarization direction can control band bending at water/ferroelectric and ferroelectric/semiconductor interfaces, thereby facilitating charge separation and transfer to the electrolyte and enhancing photocatalytic activity. For gas-surface interactions, available results suggest that using ferroelectrics to support catalytically active transition metals and oxides is another way to enhance catalytic activity. Finally, the possibility of incorporating ferroelectric switching into the catalytic cycle itself is described. In this scenario, a dynamic collaboration of two polarization states can be used to drive reactions that have been historically challenging to achieve on surfaces with fixed chemical properties (e.g., direct NOx decomposition and the selective partial oxidation of methane). These predictions show that dynamic modulation of the polarization can help overcome some of the fundamental limitations on catalytic activity imposed by the Sabatier principle.

  10. Ferroelectric Graphene-Perovskite Interfaces.

    PubMed

    Volonakis, George; Giustino, Feliciano

    2015-07-02

    Owing to their record-breaking energy conversion efficiencies, hybrid organometallic perovskites have emerged as the most promising light absorbers and ambipolar carrier transporters for solution-processable solar cells. Simultaneously, due to its exceptional electron mobility, graphene represents a prominent candidate for replacing transparent conducting oxides. Thus, it is possible that combining these wonder materials may propel the efficiency toward the Schokley-Queisser limit. Here, using first-principles calculations on graphene-CH3NH3PbI3 interfaces, we find that graphene suppresses the octahedral tilt in the very first perovskite monolayer, leading to a nanoscale ferroelectric distortion with a permanent polarization of 3 mC/m(2). This interfacial ferroelectricity drives electron extraction from the perovskite and hinders electron-hole recombination by keeping the electrons and holes separated. The interfacial ferroelectricity identified here simply results from the interplay between graphene's planar structure and CH3NH3PbI3's octahedral connectivity; therefore, this mechanism may be effective in a much broader class of perovskites, with potential applications in photovoltaics and photocatalysis.

  11. Ferroelectric Single-Crystal Gated Graphene/Hexagonal-BN/Ferroelectric Field-Effect Transistor.

    PubMed

    Park, Nahee; Kang, Haeyong; Park, Jeongmin; Lee, Yourack; Yun, Yoojoo; Lee, Jeong-Ho; Lee, Sang-Goo; Lee, Young Hee; Suh, Dongseok

    2015-11-24

    The effect of a ferroelectric polarization field on the charge transport in a two-dimensional (2D) material was examined using a graphene monolayer on a hexagonal boron nitride (hBN) field-effect transistor (FET) fabricated using a ferroelectric single-crystal substrate, (1-x)[Pb(Mg1/3Nb2/3)O3]-x[PbTiO3] (PMN-PT). In this configuration, the intrinsic properties of graphene were preserved with the use of an hBN flake, and the influence of the polarization field from PMN-PT could be distinguished. During a wide-range gate-voltage (VG) sweep, a sharp inversion of the spontaneous polarization affected the graphene channel conductance asymmetrically as well as an antihysteretic behavior. Additionally, a transition from antihysteresis to normal ferroelectric hysteresis occurred, depending on the V(G) sweep range relative to the ferroelectric coercive field. We developed a model to interpret the complex coupling among antihysteresis, current saturation, and sudden conductance variation in relation with the ferroelectric switching and the polarization-assisted charge trapping, which can be generalized to explain the combination of 2D structured materials with ferroelectrics.

  12. Ferroelectric switching of elastin

    PubMed Central

    Liu, Yuanming; Cai, Hong-Ling; Zelisko, Matthew; Wang, Yunjie; Sun, Jinglan; Yan, Fei; Ma, Feiyue; Wang, Peiqi; Chen, Qian Nataly; Zheng, Hairong; Meng, Xiangjian; Sharma, Pradeep; Zhang, Yanhang; Li, Jiangyu

    2014-01-01

    Ferroelectricity has long been speculated to have important biological functions, although its very existence in biology has never been firmly established. Here, we present compelling evidence that elastin, the key ECM protein found in connective tissues, is ferroelectric, and we elucidate the molecular mechanism of its switching. Nanoscale piezoresponse force microscopy and macroscopic pyroelectric measurements both show that elastin retains ferroelectricity at 473 K, with polarization on the order of 1 μC/cm2, whereas coarse-grained molecular dynamics simulations predict similar polarization with a Curie temperature of 580 K, which is higher than most synthetic molecular ferroelectrics. The polarization of elastin is found to be intrinsic in tropoelastin at the monomer level, analogous to the unit cell level polarization in classical perovskite ferroelectrics, and it switches via thermally activated cooperative rotation of dipoles. Our study sheds light onto a long-standing question on ferroelectric switching in biology and establishes ferroelectricity as an important biophysical property of proteins. This is a critical first step toward resolving its physiological significance and pathological implications. PMID:24958890

  13. Geometric shape control of thin film ferroelectrics and resulting structures

    DOEpatents

    McKee, Rodney A.; Walker, Frederick J.

    2000-01-01

    A monolithic crystalline structure and a method of making involves a semiconductor substrate, such as silicon, and a ferroelectric film, such as BaTiO.sub.3, overlying the surface of the substrate wherein the atomic layers of the ferroelectric film directly overlie the surface of the substrate. By controlling the geometry of the ferroelectric thin film, either during build-up of the thin film or through appropriate treatment of the thin film adjacent the boundary thereof, the in-plane tensile strain within the ferroelectric film is relieved to the extent necessary to permit the ferroelectric film to be poled out-of-plane, thereby effecting in-plane switching of the polarization of the underlying substrate material. The method of the invention includes the steps involved in effecting a discontinuity of the mechanical restraint at the boundary of the ferroelectric film atop the semiconductor substrate by, for example, either removing material from a ferroelectric film which has already been built upon the substrate, building up a ferroelectric film upon the substrate in a mesa-shaped geometry or inducing the discontinuity at the boundary by ion beam deposition techniques.

  14. Controlling Magnetic and Ferroelectric Order Through Geometry: Synthesis, Ab Initio Theory, Characterization of New Multi-Ferric Fluoride Materials

    SciTech Connect

    Halasyamani, Shiv; Fennie, Craig

    2016-11-03

    We have focused on the synthesis, characterization, and ab initio theory on multi-functional mixed-metal fluorides. With funding from the DOE, we have successfully synthesized and characterized a variety of mixed metal fluoride materials.

  15. Giant electrocaloric effect in ferroelectric nanotubes near room temperature.

    PubMed

    Liu, Man; Wang, Jie

    2015-01-12

    Ferroelectric perovskite oxides possess large electrocaloric effect, but only at high temperature, which limits their potential as next generation solid state cooling devices. Here, we demonstrate from phase field simulations that a giant adiabatic temperature change exhibits near room temperature in the strained ferroelectric PbTiO₃ nanotubes, which is several times in magnitude larger than that of PbTiO₃ thin films. Such giant adiabatic temperature change is attributed to the extrinsic contribution of unusual domain transition, which involves a dedicated interplay among the electric field, strain, temperature and polarization. Careful selection of external strain allows one to harness the extrinsic contribution to obtain large adiabatic temperature change in ferroelectric nanotubes near room temperature. Our finding provides a novel insight into the electrocaloric response of ferroelectric nanostructures and leads to a new strategy to tailor and improve the electrocaloric properties of ferroelectric materials through domain engineering.

  16. Giant electrocaloric effect in ferroelectric nanotubes near room temperature

    PubMed Central

    Liu, Man; Wang, Jie

    2015-01-01

    Ferroelectric perovskite oxides possess large electrocaloric effect, but only at high temperature, which limits their potential as next generation solid state cooling devices. Here, we demonstrate from phase field simulations that a giant adiabatic temperature change exhibits near room temperature in the strained ferroelectric PbTiO3 nanotubes, which is several times in magnitude larger than that of PbTiO3 thin films. Such giant adiabatic temperature change is attributed to the extrinsic contribution of unusual domain transition, which involves a dedicated interplay among the electric field, strain, temperature and polarization. Careful selection of external strain allows one to harness the extrinsic contribution to obtain large adiabatic temperature change in ferroelectric nanotubes near room temperature. Our finding provides a novel insight into the electrocaloric response of ferroelectric nanostructures and leads to a new strategy to tailor and improve the electrocaloric properties of ferroelectric materials through domain engineering. PMID:25578434

  17. Strain-Induced Ferroelectric Topological Insulator.

    PubMed

    Liu, Shi; Kim, Youngkuk; Tan, Liang Z; Rappe, Andrew M

    2016-03-09

    Ferroelectricity and band topology are two extensively studied yet distinct properties of insulators. Nonetheless, their coexistence has never been observed in a single material. Using first-principles calculations, we demonstrate that a noncentrosymmetric perovskite structure of CsPbI3 allows for the simultaneous presence of ferroelectric and topological orders with appropriate strain engineering. Metallic topological surface states create an intrinsic short-circuit condition, helping stabilize bulk polarization. Exploring diverse structural phases of CsPbI3 under pressure, we identify that the key structural feature for achieving a ferroelectric topological insulator is to suppress PbI6 cage rotation in the perovskite structure, which could be obtained via strain engineering. Ferroelectric control over the density of topological surface states provides a new paradigm for device engineering, such as perfect-focusing Veselago lens and spin-selective electron collimator. Our results suggest that CsPbI3 is a simple model system for ferroelectric topological insulators, enabling future studies exploring the interplay between conventional symmetry-breaking and topological orders and their novel applications in electronics and spintronics.

  18. Flexible graphene-PZT ferroelectric nonvolatile memory

    NASA Astrophysics Data System (ADS)

    Lee, Wonho; Kahya, Orhan; Tat Toh, Chee; Özyilmaz, Barbaros; Ahn, Jong-Hyun

    2013-11-01

    We report the fabrication of a flexible graphene-based nonvolatile memory device using Pb(Zr0.35,Ti0.65)O3 (PZT) as the ferroelectric material. The graphene and PZT ferroelectric layers were deposited using chemical vapor deposition and sol-gel methods, respectively. Such PZT films show a high remnant polarization (Pr) of 30 μC cm-2 and a coercive voltage (Vc) of 3.5 V under a voltage loop over ±11 V. The graphene-PZT ferroelectric nonvolatile memory on a plastic substrate displayed an on/off current ratio of 6.7, a memory window of 6 V and reliable operation. In addition, the device showed one order of magnitude lower operation voltage range than organic-based ferroelectric nonvolatile memory after removing the anti-ferroelectric behavior incorporating an electrolyte solution. The devices showed robust operation in bent states of bending radii up to 9 mm and in cycling tests of 200 times. The devices exhibited remarkable mechanical properties and were readily integrated with plastic substrates for the production of flexible circuits.

  19. Linear scanning array with bulk ferroelectric-integrated feed network.

    PubMed

    Teo, Peng-Thian; Jose, Kollakompil A; Wang, Ya-Jun; Lee, Ching-Kwang; Varadan, Vijay K

    2002-05-01

    Variable ferroelectric delay line technology has been utilized to implement a proof-of-concept, continuous scanning, ferroelectric integrated phased array antenna system. S21 phase shifts of up to 157 degrees have been achieved from the phase shifter itself via analogous variation of a DC bias. When integrated into a phased array, beam scanning of at least +/-12 degrees is achieved prior to any optimization. Some of the key material requirements, fabrication procedures, characterization, and assembly of the ferroelectric material will be revealed. The design, integration, and performance of the array system using such phased shifters will be presented.

  20. Biotechnology Opens New Routes to High-Performance Materials for Improved Photovoltaics, Batteries, Uncooled IR Detectors, Ferroelectrics and Optical Applications

    DTIC Science & Technology

    2006-11-01

    by Army Laboratories at ARL and CERDEC for lightweight, flexible, soldier-carried solar energy cells . Because the synthesis method is solution...which are advantageous for more efficient solar energy and lightweight, high power-density 3-d batteries. Because no organics or biochemicals are... interdigitated electrode array) confirm that material exhibits excellent ohmic conductance (with very low dark sheet dark sheet resistance = 5.9 x

  1. Polarization states and dielectric responses of elastically clamped ferroelectric nanocrystals

    NASA Astrophysics Data System (ADS)

    Azovtsev, A. V.; Pertsev, N. A.

    2016-12-01

    Polarization states and physical properties of ferroelectrics depend on the mechanical boundary conditions due to electrostrictive coupling between electric polarization and lattice strains. Here, we describe theoretically both equilibrium thermodynamic states and electric permittivities of ferroelectric nanocrystals subjected to the elastic three-dimensional (3D) clamping by a surrounding dielectric material. The problem is solved by the minimization of a special thermodynamic potential that describes the case of an ellipsoidal ferroelectric inclusion embedded into a linear elastic matrix. Numerical calculations are performed for BaTiO3, PbTiO3, and Pb(Zr0.5Ti0.5)O3 nanoparticles surrounded by silica glass. It is shown that, in the case of BaTiO3 and PbTiO3, elastic 3D clamping may change the order of a ferroelectric phase transition from first to second. Furthermore, the mechanical inclusion-matrix interaction shifts the temperatures of structural transitions between different ferroelectric states and even eliminates some ferroelectric phases existing in stress-free BaTiO3 and Pb(Zr0.5Ti0.5)O3 crystals. Another important effect of elastic clamping is the lowering of the symmetry of ferroelectric states in ellipsoidal inclusions, where orthorhombic and monoclinic phases may form instead of the tetragonal and rhombohedral bulk counterparts. Finally, our thermodynamic calculations show that the dielectric responses of studied perovskite ferroelectrics are sensitive to matrix-induced clamping as well. For instance, dielectric peaks occurring at structural transitions between different ferroelectric phases in BaTiO3 appear to be much higher in spherical inclusions than in the freestanding crystal. Predicted clamping-induced enhancement of certain dielectric responses at room temperature indicates that composite materials comprising nanocrystals of perovskite ferroelectrics are promising for device applications requiring the use of high-permittivity dielectrics.

  2. Short range magnetic exchange interaction favors ferroelectricity

    PubMed Central

    Wan, Xiangang; Ding, Hang-Chen; Savrasov, Sergey Y.; Duan, Chun-Gang

    2016-01-01

    Multiferroics, where two or more ferroic order parameters coexist, is one of the hottest fields in condensed matter physics and materials science. To search multiferroics, currently most researches are focused on frustrated magnets, which usually have complicated magnetic structure and low magnetic ordering temperature. Here, we argue that actually simple interatomic magnetic exchange interaction already contains a driving force for ferroelectricity, thus providing a new microscopic mechanism for the coexistence and strong coupling between ferroelectricity and magnetism. We demonstrate this mechanism by showing that even the simplest antiferromagnetic insulator like MnO, could display a magnetically induced ferroelectricity under a biaxial strain. In addition, we show that such mechanism also exists in the most important single phase multiferroics, i.e. BiFeO3, suggesting that this mechanism is ubiquitous in systems with superexchange interaction. PMID:26956480

  3. Draft 16 of a working document for a proposed standard to be entitled: IEEE standard definitions of terms associated with ferroelectric and related materials.

    PubMed

    2003-12-01

    Prior to acceptance of a standard by IEEE, it is important that the document be widely reviewed by experts in the field. This draft version of the standard is being published here to solicit that input. Readers are encouraged to submit any suggestions or corrections to the IEEE ferroelectrics standards committee for inclusion in the final version.

  4. Intrinsic space charge layers and field enhancement in ferroelectric nanojunctions

    DOE PAGES

    Cao, Ye; Ievlev, Anton V.; Morozovska, Anna N.; ...

    2015-07-13

    The conducting characteristics of topological defects in the ferroelectric materials, such as charged domain walls in ferroelectric materials, engendered broad interest and extensive study on their scientific merit and the possibility of novel applications utilizing domain engineering. At the same time, the problem of electron transport in ferroelectrics themselves still remains full of unanswered questions, and becomes still more relevant over the impending revival of interest in ferroelectric semiconductors and new improper ferroelectric materials. We have employed self-consistent phase-field modeling to investigate the physical properties of a local metal-ferroelectric (Pb(Zr0.2Ti0.8)O3) junction in applied electric field. We revealed an up tomore » 10-fold local field enhancement realized by large polarization gradient and over-polarization effects once the inherent non-linear dielectric properties of PZT are considered. The effect is independent of bias polarity and maintains its strength prior, during and after ferroelectric switching. The local field enhancement can be considered equivalent to increase of doping level, which will give rise to reduction of the switching bias and significantly smaller voltages to charge injection and electronic injection, electrochemical and photoelectrochemical processes.« less

  5. Intrinsic space charge layers and field enhancement in ferroelectric nanojunctions

    SciTech Connect

    Cao, Ye; Ievlev, Anton V.; Morozovska, Anna N.; Chen, Long-Qing; Kalinin, Sergei V.; Maksymovych, Petro

    2015-07-13

    The conducting characteristics of topological defects in the ferroelectric materials, such as charged domain walls in ferroelectric materials, engendered broad interest and extensive study on their scientific merit and the possibility of novel applications utilizing domain engineering. At the same time, the problem of electron transport in ferroelectrics themselves still remains full of unanswered questions, and becomes still more relevant over the impending revival of interest in ferroelectric semiconductors and new improper ferroelectric materials. We have employed self-consistent phase-field modeling to investigate the physical properties of a local metal-ferroelectric (Pb(Zr0.2Ti0.8)O3) junction in applied electric field. We revealed an up to 10-fold local field enhancement realized by large polarization gradient and over-polarization effects once the inherent non-linear dielectric properties of PZT are considered. The effect is independent of bias polarity and maintains its strength prior, during and after ferroelectric switching. The local field enhancement can be considered equivalent to increase of doping level, which will give rise to reduction of the switching bias and significantly smaller voltages to charge injection and electronic injection, electrochemical and photoelectrochemical processes.

  6. Intrinsic ferroelectric switching from first principles

    NASA Astrophysics Data System (ADS)

    Liu, Shi; Grinberg, Ilya; Rappe, Andrew M.

    2016-06-01

    The existence of domain walls, which separate regions of different polarization, can influence the dielectric, piezoelectric, pyroelectric and electronic properties of ferroelectric materials. In particular, domain-wall motion is crucial for polarization switching, which is characterized by the hysteresis loop that is a signature feature of ferroelectric materials. Experimentally, the observed dynamics of polarization switching and domain-wall motion are usually explained as the behaviour of an elastic interface pinned by a random potential that is generated by defects, which appear to be strongly sample-dependent and affected by various elastic, microstructural and other extrinsic effects. Theoretically, connecting the zero-kelvin, first-principles-based, microscopic quantities of a sample with finite-temperature, macroscopic properties such as the coercive field is critical for material design and device performance; and the lack of such a connection has prevented the use of techniques based on ab initio calculations for high-throughput computational materials discovery. Here we use molecular dynamics simulations of 90° domain walls (separating domains with orthogonal polarization directions) in the ferroelectric material PbTiO3 to provide microscopic insights that enable the construction of a simple, universal, nucleation-and-growth-based analytical model that quantifies the dynamics of many types of domain walls in various ferroelectrics. We then predict the temperature and frequency dependence of hysteresis loops and coercive fields at finite temperatures from first principles. We find that, even in the absence of defects, the intrinsic temperature and field dependence of the domain-wall velocity can be described with a nonlinear creep-like region and a depinning-like region. Our model enables quantitative estimation of coercive fields, which agree well with experimental results for ceramics and thin films. This agreement between model and experiment suggests

  7. Intrinsic ferroelectric switching from first principles.

    PubMed

    Liu, Shi; Grinberg, Ilya; Rappe, Andrew M

    2016-06-16

    The existence of domain walls, which separate regions of different polarization, can influence the dielectric, piezoelectric, pyroelectric and electronic properties of ferroelectric materials. In particular, domain-wall motion is crucial for polarization switching, which is characterized by the hysteresis loop that is a signature feature of ferroelectric materials. Experimentally, the observed dynamics of polarization switching and domain-wall motion are usually explained as the behaviour of an elastic interface pinned by a random potential that is generated by defects, which appear to be strongly sample-dependent and affected by various elastic, microstructural and other extrinsic effects. Theoretically, connecting the zero-kelvin, first-principles-based, microscopic quantities of a sample with finite-temperature, macroscopic properties such as the coercive field is critical for material design and device performance; and the lack of such a connection has prevented the use of techniques based on ab initio calculations for high-throughput computational materials discovery. Here we use molecular dynamics simulations of 90° domain walls (separating domains with orthogonal polarization directions) in the ferroelectric material PbTiO3 to provide microscopic insights that enable the construction of a simple, universal, nucleation-and-growth-based analytical model that quantifies the dynamics of many types of domain walls in various ferroelectrics. We then predict the temperature and frequency dependence of hysteresis loops and coercive fields at finite temperatures from first principles. We find that, even in the absence of defects, the intrinsic temperature and field dependence of the domain-wall velocity can be described with a nonlinear creep-like region and a depinning-like region. Our model enables quantitative estimation of coercive fields, which agree well with experimental results for ceramics and thin films. This agreement between model and experiment suggests

  8. Towards multicaloric effect with ferroelectrics

    NASA Astrophysics Data System (ADS)

    Liu, Yang; Zhang, Guangzu; Li, Qi; Bellaiche, Laurent; Scott, James F.; Dkhil, Brahim; Wang, Qing

    2016-12-01

    Utilizing thermal changes in solid-state materials strategically offers caloric-based alternatives to replace current vapor-compression technology. To make full use of multiple forms of the entropy and achieve higher efficiency for designs of cooling devices, the multicaloric effect appears as a cutting-edge concept encouraging researchers to search for multicaloric materials with outstanding caloric properties. Here we report the multicaloric effect in BaTi O3 single crystals driven simultaneously by mechanical and electric fields and described via a thermodynamic phenomenological model. It is found that the multicaloric behavior is mainly dominated by the mechanical field rather than the electric field, since the paraelectric-to-ferroelectric transition is more sensitive to mechanical field than to electric field. The use of uniaxial stress competes favorably with pressure due to its much higher caloric strength and negligible elastic thermal change. It is revealed that multicaloric response can be significantly larger than just the sum of mechanocaloric and electrocaloric effects in temperature regions far above the Curie temperature but cannot exceed this limit near the Curie temperature. Our results also show the advantage of the multicaloric effect over the mechanically mediated electrocaloric effect or electrically mediated mechanocaloric effect. Our findings therefore highlight the importance of ferroelectric materials to develop multicaloric cooling.

  9. Manganese incorporation into ferroelectric lead titanate

    NASA Astrophysics Data System (ADS)

    Stoupin, Stanislav

    Substitution with 3d magnetic transition elements in ABO 3 ferroelectric perovskite host media is widely utilized to produce relaxor ferroelectrics. Many resulting solid solutions exhibit magnetoelectric properties affected by concentration levels of the introduced magnetic ions. For conventional material preparation techniques such as firing of mechanically mixed oxides, incorporation is often limited by 5 mol% concentration level. Doping at higher concentrations requires introduction of other substituents to compensate charge within the unit cell to promote formation of the perovskite phase. In contrast, molecular mixing of precursor materials at the initial phase of preparation procedure offers an advantage of achieving higher incorporation levels of the 3d elements without additional charge-compensating ions. Presented in this thesis is a new sol-gel procedure utilized for high level incorporation of 3d magnetic ions into ferroelectric lead titanate. The technique was applied to produce PbTi1-xMnxO 3 solid solution, a perovskite system promising for high degree of magnetoelectric coupling. Concentration dependent studies were performed to characterize structural, thermal, ferroelectric and magnetic properties of the material. The solubility limit of Mn has been found to be 20 mol% and the material remains tetragonally distorted. X-ray Absorption Spectroscopy confirms that local structural environment of Mn, Ti, and Pb is consistent with tetragonal symmetry of the unit cell. Increase in Mn concentration leads to reduction in melting point, broadening of the ferroelectric transition, reduction of the transition temperature and increase in dielectric constant of the material. At the solubility limit the system was found to be ferromagnetic below 50 K.

  10. Ferroelectric control of metal-insulator transition

    NASA Astrophysics Data System (ADS)

    He, Xu; Jin, Kui-juan; Ge, Chen; Ma, Zhong-shui; Yang, Guo-zhen

    2016-03-01

    We propose a method of controlling the metal-insulator transition of one perovskite material at its interface with another ferroelectric material based on first principle calculations. The operating principle is that the rotation of oxygen octahedra tuned by the ferroelectric polarization can modulate the superexchange interaction in this perovskite. We designed a tri-color superlattice of (BiFeO3)N/LaNiO3/LaTiO3, in which the BiFeO3 layers are ferroelectric, the LaNiO3 layer is the layer of which the electronic structure is to be tuned, and LaTiO3 layer is inserted to enhance the inversion asymmetry. By reversing the ferroelectric polarization in this structure, there is a metal-insulator transition of the LaNiO3 layer because of the changes of crystal field splitting of the Ni eg orbitals and the bandwidth of the Ni in-plane eg orbital. It is highly expected that a metal-transition can be realized by designing the structures at the interfaces for more materials.

  11. Analyzing piezoresponse force microscopy for reconstruction of probed ferroelectric structures

    NASA Astrophysics Data System (ADS)

    Pan, K.; Liu, Y. Y.; Liu, Y. M.; Li, J. Y.

    2012-09-01

    Piezoresponse force microscopy (PFM) has emerged as the tool of choice for characterizing piezoelectric and ferroelectric materials at nanoscale, yet the interpretation of PFM remains to be difficult and sometimes ambiguous. Built on earlier works, we developed a numerical integration scheme to analyze the expected PFM response in ferroelectrics with arbitrary domain configurations, with the ultimate goal to accurately reconstruct the underlying ferroelectric structure from PFM measurements. Using such technique, we demonstrated that the relationship between the effective and intrinsic piezoelectric coefficients is sensitive to a variety of factors that are intrinsic to the probed materials, and showed that the PFM mapping is not only influenced by polarization distribution on the sample surface but also three-dimensional polarization distribution inside the material. While relatively simple domain structures were used for demonstration, the approach is general, and can be applied to ferroelectrics with arbitrary polarization distributions.

  12. Photovoltaics with Ferroelectrics: Current Status and Beyond.

    PubMed

    Paillard, Charles; Bai, Xiaofei; Infante, Ingrid C; Guennou, Maël; Geneste, Grégory; Alexe, Marin; Kreisel, Jens; Dkhil, Brahim

    2016-07-01

    Ferroelectrics carry a switchable spontaneous electric polarization. This polarization is usually coupled to strain, making ferroelectrics good piezoelectrics. When coupled to magnetism, they become so-called multiferroic systems, a field that has been widely investigated since 2003. While ferroelectrics are birefringent and non-linear optically transparent materials, the coupling of polarization with optical properties has received, since 2009, renewed attention, triggered notably by low-bandgap ferroelectrics suitable for sunlight spectrum absorption and original photovoltaic effects. Consequently, power conversion efficiencies up to 8.1% were recently achieved and values of 19.5% were predicted, making photoferroelectrics promising photovoltaic alternatives. This article aims at providing an up-to-date review on this emerging and rapidly progressing field by highlighting several important issues and parameters, such as the role of domain walls, ways to tune the bandgap, consequences arising from the polarization switchability, and the role of defects and contact electrodes, as well as the downscaling effects. Beyond photovoltaicity, other polarization-related processes are also described, like light-induced deformation (photostriction) or light-assisted chemical reaction (photostriction). It is hoped that this overview will encourage further avenues to be explored and challenged and, as a byproduct, will inspire other research communities in material science, e.g., so-called hybrid halide perovskites.

  13. Ferroelectric Devices Emit Charged Particles and Radiation

    NASA Technical Reports Server (NTRS)

    Bar-Cohen, Yoseph; Sherrit, Stewart; Bao, Xiaoqi; Felsteiner, Joshua; Karsik, Yakov

    2005-01-01

    Devices called solid-state ferroelectric- based sources (SSFBSs) are under development as sources of electrons, ions, ultraviolet light, and x-rays for diverse applications in characterization and processing of materials. Whereas heretofore it has been necessary to use a different device to generate each of the aforementioned species of charged particles or radiation, a single SSFBS can be configured and operated to selectively generate any of the species as needed using a single source. Relative to comparable prior sources based, variously, on field emission, thermionic emission, and gaseous discharge plasmas, SSFBSs demand less power, and are compact and lightweight. An SSFBS exploits the unique physical characteristics of a ferroelectric material in the presence of a high-frequency pulsed electric field. The basic building block of an SSFBS is a ferroelectric cathode -- a ferroelectric wafer with a solid electrode covering its rear face and a grid electrode on its front face (see figure). The application of a voltage pulse -- typically having amplitude of several kilovolts and duration of several nanoseconds -- causes dense surface plasma to form near the grid wires on the front surface.

  14. Ferroelectrics based absorbing layers

    NASA Astrophysics Data System (ADS)

    Hao, Jianping; Sadaune, Véronique; Burgnies, Ludovic; Lippens, Didier

    2014-07-01

    We show that ferroelectrics-based periodic structure made of BaSrTiO3 (BST) cubes, arrayed onto a metal plate with a thin dielectric spacer film exhibit a dramatic enhancement of absorbance with value close to unity. The enhancement is found around the Mie magnetic resonance of the Ferroelectrics cubes with the backside metal layer stopping any transmitted waves. It also involves quasi-perfect impedance matching resulting in reflection suppression via simultaneous magnetic and electrical activities. In addition, it was shown numerically the existence of a periodicity optimum, which is explained from surface waves analysis along with trade-off between the resonance damping and the intrinsic loss of ferroelectrics cubes. An experimental verification in a hollow waveguide configuration with a good comparison with full-wave numerical modelling is at last reported by measuring the scattering parameters of single and dual BST cubes schemes pointing out coupling effects for densely packed structures.

  15. Applications of modern ferroelectrics.

    PubMed

    Scott, J F

    2007-02-16

    Long viewed as a topic in classical physics, ferroelectricity can be described by a quantum mechanical ab initio theory. Thin-film nanoscale device structures integrated onto Si chips have made inroads into the semiconductor industry. Recent prototype applications include ultrafast switching, cheap room-temperature magnetic-field detectors, piezoelectric nanotubes for microfluidic systems, electrocaloric coolers for computers, phased-array radar, and three-dimensional trenched capacitors for dynamic random access memories. Terabit-per-square-inch ferroelectric arrays of lead zirconate titanate have been reported on Pt nanowire interconnects and nanorings with 5-nanometer diameters. Finally, electron emission from ferroelectrics yields cheap, high-power microwave devices and miniature x-ray and neutron sources.

  16. Ferroelectric switching of poly(vinylidene difluoride-trifluoroethylene) in metal-ferroelectric-semiconductor non-volatile memories with an amorphous oxide semiconductor

    NASA Astrophysics Data System (ADS)

    Gelinck, G. H.; van Breemen, A. J. J. M.; Cobb, B.

    2015-03-01

    Ferroelectric polarization switching of poly(vinylidene difluoride-trifluoroethylene) is investigated in different thin-film device structures, ranging from simple capacitors to dual-gate thin-film transistors (TFT). Indium gallium zinc oxide, a high mobility amorphous oxide material, is used as semiconductor. We find that the ferroelectric can be polarized in both directions in the metal-ferroelectric-semiconductor (MFS) structure and in the dual-gate TFT under certain biasing conditions, but not in the single-gate thin-film transistors. These results disprove the common belief that MFS structures serve as a good model system for ferroelectric polarization switching in thin-film transistors.

  17. Ferroelectric switching of poly(vinylidene difluoride-trifluoroethylene) in metal-ferroelectric-semiconductor non-volatile memories with an amorphous oxide semiconductor

    SciTech Connect

    Gelinck, G. H.; Breemen, A. J. J. M. van; Cobb, B.

    2015-03-02

    Ferroelectric polarization switching of poly(vinylidene difluoride-trifluoroethylene) is investigated in different thin-film device structures, ranging from simple capacitors to dual-gate thin-film transistors (TFT). Indium gallium zinc oxide, a high mobility amorphous oxide material, is used as semiconductor. We find that the ferroelectric can be polarized in both directions in the metal-ferroelectric-semiconductor (MFS) structure and in the dual-gate TFT under certain biasing conditions, but not in the single-gate thin-film transistors. These results disprove the common belief that MFS structures serve as a good model system for ferroelectric polarization switching in thin-film transistors.

  18. Unravelling and controlling hidden imprint fields in ferroelectric capacitors

    NASA Astrophysics Data System (ADS)

    Liu, Fanmao; Fina, Ignasi; Bertacco, Riccardo; Fontcuberta, Josep

    2016-04-01

    Ferroelectric materials have a spontaneous polarization that can point along energetically equivalent, opposite directions. However, when ferroelectric layers are sandwiched between different metallic electrodes, asymmetric electrostatic boundary conditions may induce the appearance of an electric field (imprint field, Eimp) that breaks the degeneracy of the polarization directions, favouring one of them. This has dramatic consequences on functionality of ferroelectric-based devices such as ferroelectric memories or photodetectors. Therefore, to cancel out the Eimp, ferroelectric components are commonly built using symmetric contact configuration. Indeed, in this symmetric contact configuration, when measurements are done under time-varying electric fields of relatively low frequency, an archetypical symmetric single-step switching process is observed, indicating Eimp ≈ 0. However, we report here on the discovery that when measurements are performed at high frequency, a well-defined double-step switching is observed, indicating the presence of Eimp. We argue that this frequency dependence originates from short-living head-to-head or tail-to-tail ferroelectric capacitors in the device. We demonstrate that we can modulate Eimp and the life-time of head-to-head or tail-to-tail polarization configurations by adjusting the polarization screening charges by suitable illumination. These findings are of relevance to understand the effects of internal electric fields on pivotal ferroelectric properties, such as memory retention and photoresponse.

  19. Unravelling and controlling hidden imprint fields in ferroelectric capacitors

    PubMed Central

    Liu, Fanmao; Fina, Ignasi; Bertacco, Riccardo; Fontcuberta, Josep

    2016-01-01

    Ferroelectric materials have a spontaneous polarization that can point along energetically equivalent, opposite directions. However, when ferroelectric layers are sandwiched between different metallic electrodes, asymmetric electrostatic boundary conditions may induce the appearance of an electric field (imprint field, Eimp) that breaks the degeneracy of the polarization directions, favouring one of them. This has dramatic consequences on functionality of ferroelectric-based devices such as ferroelectric memories or photodetectors. Therefore, to cancel out the Eimp, ferroelectric components are commonly built using symmetric contact configuration. Indeed, in this symmetric contact configuration, when measurements are done under time-varying electric fields of relatively low frequency, an archetypical symmetric single-step switching process is observed, indicating Eimp ≈ 0. However, we report here on the discovery that when measurements are performed at high frequency, a well-defined double-step switching is observed, indicating the presence of Eimp. We argue that this frequency dependence originates from short-living head-to-head or tail-to-tail ferroelectric capacitors in the device. We demonstrate that we can modulate Eimp and the life-time of head-to-head or tail-to-tail polarization configurations by adjusting the polarization screening charges by suitable illumination. These findings are of relevance to understand the effects of internal electric fields on pivotal ferroelectric properties, such as memory retention and photoresponse. PMID:27122309

  20. Nanoscale probing and photonic applications of ferroelectric domain walls

    NASA Astrophysics Data System (ADS)

    Tian, Lili

    Ferroelectrics are a versatile solid-state platform for a new generation of micro- and nanophotonic applications. Conventional integrated optics has often treated the phenomenon of ferroelectric domains and domain walls more as a nuisance rather than an asset. Ironically, domain walls can be immensely valuable in realizing a wide variety of new functionalities such as laser scanning, dynamic focusing, frequency conversion, beam shaping, waveguiding, high-speed modulation, and photonic crystal structures. All of these functions can be realized by shaping ferroelectric domain walls into arbitrary shapes on micro to nanoscale dimensions. Domain walls, however, have a mind of their own when it comes to shaping them. This thesis will focus on the fundamental domain switching characteristics under the uniform electrical fields, and local electromechanical response across the single ferroelectric domain wall in ferroelectric crystals lithium niobate, lithium tantalate and strontium barium niobate. The local electromechanical response across the single was modeled using finite element method to better understand the fundamentals of piezoelectric force microscopy in order to quantitatively interpret the measured material properties. The influence of stoichiometry on domain dynamics on macroscale and on local electromechanical properties on nanoscale was studied. The challenges in shaping ferroelectric domain are discussed and the examples of optical devices such as optical switch and optical beam deflector based on ferroelectric domain walls are presented.

  1. Unravelling and controlling hidden imprint fields in ferroelectric capacitors.

    PubMed

    Liu, Fanmao; Fina, Ignasi; Bertacco, Riccardo; Fontcuberta, Josep

    2016-04-28

    Ferroelectric materials have a spontaneous polarization that can point along energetically equivalent, opposite directions. However, when ferroelectric layers are sandwiched between different metallic electrodes, asymmetric electrostatic boundary conditions may induce the appearance of an electric field (imprint field, Eimp) that breaks the degeneracy of the polarization directions, favouring one of them. This has dramatic consequences on functionality of ferroelectric-based devices such as ferroelectric memories or photodetectors. Therefore, to cancel out the Eimp, ferroelectric components are commonly built using symmetric contact configuration. Indeed, in this symmetric contact configuration, when measurements are done under time-varying electric fields of relatively low frequency, an archetypical symmetric single-step switching process is observed, indicating Eimp ≈ 0. However, we report here on the discovery that when measurements are performed at high frequency, a well-defined double-step switching is observed, indicating the presence of Eimp. We argue that this frequency dependence originates from short-living head-to-head or tail-to-tail ferroelectric capacitors in the device. We demonstrate that we can modulate Eimp and the life-time of head-to-head or tail-to-tail polarization configurations by adjusting the polarization screening charges by suitable illumination. These findings are of relevance to understand the effects of internal electric fields on pivotal ferroelectric properties, such as memory retention and photoresponse.

  2. Ferroelectric tunneling element and memory applications which utilize the tunneling element

    DOEpatents

    Kalinin, Sergei V [Knoxville, TN; Christen, Hans M [Knoxville, TN; Baddorf, Arthur P [Knoxville, TN; Meunier, Vincent [Knoxville, TN; Lee, Ho Nyung [Oak Ridge, TN

    2010-07-20

    A tunneling element includes a thin film layer of ferroelectric material and a pair of dissimilar electrically-conductive layers disposed on opposite sides of the ferroelectric layer. Because of the dissimilarity in composition or construction between the electrically-conductive layers, the electron transport behavior of the electrically-conductive layers is polarization dependent when the tunneling element is below the Curie temperature of the layer of ferroelectric material. The element can be used as a basis of compact 1R type non-volatile random access memory (RAM). The advantages include extremely simple architecture, ultimate scalability and fast access times generic for all ferroelectric memories.

  3. Room-temperature ferroelectricity in CuInP2S6 ultrathin flakes

    DOE PAGES

    Liu, Fucai; You, Lu; Seyler, Kyle L.; ...

    2016-08-11

    In this study, two-dimensional (2D) materials have emerged as promising candidates for various optoelectronic applications based on their diverse electronic properties, ranging from insulating to superconducting. However, cooperative phenomena such as ferroelectricity in the 2D limit have not been well explored. Here, we report room-temperature ferroelectricity in 2D CuInP2S6 (CIPS) with a transition temperature of ~320 K. Switchable polarization is observed in thin CIPS of ~4 nm. To demonstrate the potential of this 2D ferroelectric material, we prepare a van der Waals (vdW) ferroelectric diode formed by CIPS/Si heterostructure, which shows good memory behaviour with on/off ratio of ~100. Themore » addition of ferroelectricity to the 2D family opens up possibilities for numerous novel applications, including sensors, actuators, non-volatile memory devices, and various vdW heterostructures based on 2D ferroelectricity.« less

  4. Room-temperature ferroelectricity in CuInP2S6 ultrathin flakes

    NASA Astrophysics Data System (ADS)

    Liu, Fucai; You, Lu; Seyler, Kyle L.; Li, Xiaobao; Yu, Peng; Lin, Junhao; Wang, Xuewen; Zhou, Jiadong; Wang, Hong; He, Haiyong; Pantelides, Sokrates T.; Zhou, Wu; Sharma, Pradeep; Xu, Xiaodong; Ajayan, Pulickel M.; Wang, Junling; Liu, Zheng

    2016-08-01

    Two-dimensional (2D) materials have emerged as promising candidates for various optoelectronic applications based on their diverse electronic properties, ranging from insulating to superconducting. However, cooperative phenomena such as ferroelectricity in the 2D limit have not been well explored. Here, we report room-temperature ferroelectricity in 2D CuInP2S6 (CIPS) with a transition temperature of ~320 K. Switchable polarization is observed in thin CIPS of ~4 nm. To demonstrate the potential of this 2D ferroelectric material, we prepare a van der Waals (vdW) ferroelectric diode formed by CIPS/Si heterostructure, which shows good memory behaviour with on/off ratio of ~100. The addition of ferroelectricity to the 2D family opens up possibilities for numerous novel applications, including sensors, actuators, non-volatile memory devices, and various vdW heterostructures based on 2D ferroelectricity.

  5. Room-temperature ferroelectricity in CuInP2S6 ultrathin flakes

    PubMed Central

    Liu, Fucai; You, Lu; Seyler, Kyle L.; Li, Xiaobao; Yu, Peng; Lin, Junhao; Wang, Xuewen; Zhou, Jiadong; Wang, Hong; He, Haiyong; Pantelides, Sokrates T.; Zhou, Wu; Sharma, Pradeep; Xu, Xiaodong; Ajayan, Pulickel M.; Wang, Junling; Liu, Zheng

    2016-01-01

    Two-dimensional (2D) materials have emerged as promising candidates for various optoelectronic applications based on their diverse electronic properties, ranging from insulating to superconducting. However, cooperative phenomena such as ferroelectricity in the 2D limit have not been well explored. Here, we report room-temperature ferroelectricity in 2D CuInP2S6 (CIPS) with a transition temperature of ∼320 K. Switchable polarization is observed in thin CIPS of ∼4 nm. To demonstrate the potential of this 2D ferroelectric material, we prepare a van der Waals (vdW) ferroelectric diode formed by CIPS/Si heterostructure, which shows good memory behaviour with on/off ratio of ∼100. The addition of ferroelectricity to the 2D family opens up possibilities for numerous novel applications, including sensors, actuators, non-volatile memory devices, and various vdW heterostructures based on 2D ferroelectricity. PMID:27510418

  6. Design of a Multi-Level/Analog Ferroelectric Memory Device

    NASA Technical Reports Server (NTRS)

    MacLeod, Todd C.; Phillips, Thomas A.; Ho, Fat D.

    2006-01-01

    Increasing the memory density and utilizing the dove1 characteristics of ferroelectric devices is important in making ferroelectric memory devices more desirable to the consumer. This paper describes a design that allows multiple levels to be stored in a ferroelectric based memory cell. It can be used to store multiple bits or analog values in a high speed nonvolatile memory. The design utilizes the hysteresis characteristic of ferroelectric transistors to store an analog value in the memory cell. The design also compensates for the decay of the polarization of the ferroelectric material over time. This is done by utilizing a pair of ferroelectric transistors to store the data. One transistor is used as a reference to determine the amount of decay that has occurred since the pair was programmed. The second transistor stores the analog value as a polarization value between zero and saturated. The design allows digital data to be stored as multiple bits in each memory cell. The number of bits per cell that can be stored will vary with the decay rate of the ferroelectric transistors and the repeatability of polarization between transistors. It is predicted that each memory cell may be able to store 8 bits or more. The design is based on data taken from actual ferroelectric transistors. Although the circuit has not been fabricated, a prototype circuit is now under construction. The design of this circuit is different than multi-level FLASH or silicon transistor circuits. The differences between these types of circuits are described in this paper. This memory design will be useful because it allows higher memory density, compensates for the environmental and ferroelectric aging processes, allows analog values to be directly stored in memory, compensates for the thermal and radiation environments associated with space operations, and relies only on existing technologies.

  7. A hybrid ferroelectric-flash memory cells

    NASA Astrophysics Data System (ADS)

    Park, Jae Hyo; Byun, Chang Woo; Seok, Ki Hwan; Kim, Hyung Yoon; Chae, Hee Jae; Lee, Sol Kyu; Son, Se Wan; Ahn, Donghwan; Joo, Seung Ki

    2014-09-01

    A ferroelectric-flash (F-flash) memory cells having a metal-ferroelectric-nitride-oxynitride-silicon structure are demonstrated, and the ferroelectric materials were perovskite-dominated Pb(Zr,Ti)O3 (PZT) crystallized by Pt gate electrode. The PZT thin-film as a blocking layer improves electrical and memorial performance where programming and erasing mechanism are different from the metal-ferroelectric-insulator-semiconductor device or the conventional silicon-oxide-nitride-oxide-silicon device. F-flash cells exhibit not only the excellent electrical transistor performance, having 442.7 cm2 V-1 s-1 of field-effect mobility, 190 mV dec-1 of substhreshold slope, and 8 × 105 on/off drain current ratio, but also a high reliable memory characteristics, having a large memory window (6.5 V), low-operating voltage (0 to -5 V), faster P/E switching speed (50/500 μs), long retention time (>10 years), and excellent fatigue P/E cycle (>105) due to the boosting effect, amplification effect, and energy band distortion of nitride from the large polarization. All these characteristics correspond to the best performances among conventional flash cells reported so far.

  8. Proceedings of the International Symposium on Integrated Ferroelectrics (ISIF) (3rd)

    DTIC Science & Technology

    1991-04-05

    used non-ferroelectric materials such as aluminum nitride (AIN) and zinc oxide (ZnO). The pyroelectric properties in these ferroelectric thin films are...followed by sputtering aluminum (2% Si) to form interconnects and bonding pads. Ferroelectric thin film properties are summarized in Table I. MICROSENSOR...10 S.B. Krupanidhi Advances in Processing and Properties of Pwanisdt Thit-Fi~ms for FRAMs, DRAMs. and Deoooupirg Ce p aca

  9. Fast Ferroelectric L-Band Tuner for ILC Cavities

    SciTech Connect

    Hirshfield, Jay L

    2010-03-15

    Design, analysis, and low-power tests are described on a 1.3 GHz ferroelectric tuner that could find application in the International Linear Collider or in Project X at Fermi National Accelerator Laboratory. The tuner configuration utilizes a three-deck sandwich imbedded in a WR-650 waveguide, in which ferroelectric bars are clamped between conducting plates that allow the tuning bias voltage to be applied. Use of a reduced one-third structure allowed tests of critical parameters of the configuration, including phase shift, loss, and switching speed. Issues that were revealed that require improvement include reducing loss tangent in the ferroelectric material, development of a reliable means of brazing ferroelectric elements to copper parts of the tuner, and simplification of the mechanical design of the configuration.

  10. Intrinsic space charge layers and field enhancement in ferroelectric nanojunctions

    NASA Astrophysics Data System (ADS)

    Cao, Ye; Ievlev, Anton V.; Morozovska, Anna N.; Chen, Long-Qing; Kalinin, Sergei V.; Maksymovych, Petro

    2015-07-01

    Conducting characteristics of topological defects in ferroelectric materials, such as charged domain walls, engendered a broad interest on their scientific merit and the possibility of novel applications utilizing domain engineering. At the same time, the problem of electron transport in ferroelectrics still remains full of unanswered questions and becomes yet more relevant over the growing interest in ferroelectric semiconductors and new improper ferroelectric materials. We have employed self-consistent phase-field modeling to investigate the physical properties of a local metal-ferroelectric (Pb(Zr0.2Ti0.8)O3) junction in applied electric field. We revealed an up to 10-fold local enhancement of electric field realized by large polarization gradient and over-polarization effects due to inherent non-linear dielectric properties of Pb(Zr0.2Ti0.8)O3. The effect is independent of bias polarity and maintains its strength prior, during and after ferroelectric switching. The observed field enhancement can be considered on similar grounds as increased doping level, giving rise to reduced switching bias and threshold voltages for charge injection, electrochemical and photoelectrochemical processes.

  11. Intrinsic space charge layers and field enhancement in ferroelectric nanojunctions

    SciTech Connect

    Cao, Ye; Ievlev, Anton V.; Kalinin, Sergei V.; Maksymovych, Petro; Morozovska, Anna N.; Chen, Long-Qing

    2015-07-13

    Conducting characteristics of topological defects in ferroelectric materials, such as charged domain walls, engendered a broad interest on their scientific merit and the possibility of novel applications utilizing domain engineering. At the same time, the problem of electron transport in ferroelectrics still remains full of unanswered questions and becomes yet more relevant over the growing interest in ferroelectric semiconductors and new improper ferroelectric materials. We have employed self-consistent phase-field modeling to investigate the physical properties of a local metal-ferroelectric (Pb(Zr{sub 0.2}Ti{sub 0.8})O{sub 3}) junction in applied electric field. We revealed an up to 10-fold local enhancement of electric field realized by large polarization gradient and over-polarization effects due to inherent non-linear dielectric properties of Pb(Zr{sub 0.2}Ti{sub 0.8})O{sub 3}. The effect is independent of bias polarity and maintains its strength prior, during and after ferroelectric switching. The observed field enhancement can be considered on similar grounds as increased doping level, giving rise to reduced switching bias and threshold voltages for charge injection, electrochemical and photoelectrochemical processes.

  12. Upper bounds for flexoelectric coefficients in ferroelectrics

    NASA Astrophysics Data System (ADS)

    Yudin, P. V.; Ahluwalia, R.; Tagantsev, A. K.

    2014-02-01

    Flexoelectric effect is the response of electric polarization to the mechanical strain gradient. At the nano-scale, where large strain gradients are expected, the flexoelectric effect becomes appreciable and may substitute piezoelectric effect in centrosymmetric materials. These features make flexoelectricity of growing interest during the last decade. At the same time, the available theoretical and experimental results are rather contradictory. In particular, experimentally measured flexoelectric coefficients in some ferroelectric materials largely exceed theoretically predicted values. Here, we determine the upper limits for the magnitude of the static bulk contribution to the flexoelectric effect in ferroelectrics, the contribution which was customarily considered as the dominating one. The magnitude of the upper bounds obtained suggests that the anomalously high flexoelectric coupling documented for perovskite ceramics can hardly be attributed to a manifestation of the static bulk effect.

  13. Molecular ferroelectrics: where electronics meet biology

    PubMed Central

    Li, Jiangyu; Liu, Yuanming; Zhang, Yanhang; Cai, Hong-Ling; Xiong, Ren-Gen

    2013-01-01

    In the last several years, we have witnessed significant advances in molecular ferroelectrics, with ferroelectric properties of molecular crystals approaching those of barium titanate. In addition, ferroelectricity has been observed in biological systems, filling an important missing link in bioelectric phenomena. In this perspective, we will present short historical notes on ferroelectrics, followed by overview on the fundamentals of ferroelectricity. Latest development in molecular ferroelectrics and biological ferroelectricity will then be highlighted, and their implications and potential applications will be discussed. We close by noting molecular ferroelectric as an exciting frontier between electronics and biology, and a number of challenges ahead are also noted. PMID:24018952

  14. Molecular ferroelectrics: where electronics meet biology.

    PubMed

    Li, Jiangyu; Liu, Yuanming; Zhang, Yanhang; Cai, Hong-Ling; Xiong, Ren-Gen

    2013-12-28

    In the last several years, we have witnessed significant advances in molecular ferroelectrics, with the ferroelectric properties of molecular crystals approaching those of barium titanate. In addition, ferroelectricity has been observed in biological systems, filling an important missing link in bioelectric phenomena. In this perspective, we will present short historical notes on ferroelectrics, followed by an overview of the fundamentals of ferroelectricity. The latest developments in molecular ferroelectrics and biological ferroelectricity will then be highlighted, and their implications and potential applications will be discussed. We close by noting molecular ferroelectric as an exciting frontier between electronics and biology, and a number of challenges ahead are also described.

  15. Depolarization field effect on dielectric and piezoelectric properties of particulate ferroelectric ceramic-polymer composites

    NASA Astrophysics Data System (ADS)

    Ma, Fengde D.; Wang, Yu U.

    2015-03-01

    The effects of depolarization field on the dielectric and piezoelectric properties of ferroelectric ceramic particle-filled polymer-matrix composites are investigated at the underlying domain level. Phase field modeling and simulation reveals that the macroscopic properties of the composites are dominated by depolarization field effect, which depends on the arrangement and alignment rather than the size or internal grain structure of the ferroelectric particulates. It is found that 0-3 particulate composites with random dispersion of ferroelectric particles behave essentially like linear dielectric rather than ferroelectric materials, and domain-level analysis reveals the physical mechanism for lack of domain switching or hysteresis as attributed to strong depolarization effect. Thus, without effective reduction or elimination of the depolarization field, the composites cannot benefit from the functional fillers regardless of their superior properties. In order to exhibit the desired ferroelectric behaviors, it necessitates continuous ferroelectric phase connectivity in the composites.

  16. Imaging and control of domain structures in ferroelectric thin films via scanning force microscopy.

    SciTech Connect

    Gruverman, A.; Auciello, O.; Tokumoto, H.; Materials Science Division; Joint Research Center for Atom Tech.; National Inst. for Advanced Interdisciplinary Research

    1998-01-01

    Scanning force microscopy (SFM) is becoming a powerful technique with great potential both for imaging and for control of domain structures in ferroelectric materials at the nanometer scale. Application of SFM to visualization of domain structures in ferroelectric thin films is described. Imaging methods of ferroelectric domains are based on the detection of surface charges in the noncontact mode of SFM and on the measurement of the piezoelectric response of a ferroelectric film to an external field applied by the tip in the SFM contact mode. This latter mode can be used for nondestructive evaluation of local ferroelectric and piezoelectric properties and for manipulation of domains of less than 50 nm in diameter. The effect of the film thickness and crystallinity on the imaging resolution is discussed. Scanning force microscopy is shown to be a technique well suited for nanoscale investigation of switching processes and electrical degradation effects in ferroelectric thin films.

  17. Insights into electrical characteristics of silicon doped hafnium oxide ferroelectric thin films

    NASA Astrophysics Data System (ADS)

    Zhou, Dayu; Müller, J.; Xu, Jin; Knebel, S.; Bräuhaus, D.; Schröder, U.

    2012-02-01

    Silicon doped hafnium oxide thin films were recently discovered to exhibit ferroelectricity. In the present study, metal-ferroelectric-metal capacitors with Si:HfO2 thin films as ferroelectric material and TiN as electrodes have been characterized with respect to capacitance and current density as functions of temperature and applied voltage. Polarity asymmetry of the frequency dependent coercive field was explained by interfacial effects. No ferroelectric-paraelectric phase transition was observed at temperatures up to 478 K. Clear distinctions between current evolutions with or without polarization switching were correlated to the time competition between the measurement and the response of relaxation mechanisms.

  18. Probing Nanoscale Ferroelectricity by Ultraviolet Raman Spectroscopy

    DTIC Science & Technology

    2006-09-15

    gap materials because the visible photon energy is much smaller than the band gap (10). Consequently, the absorption is extremely weak and the...UV ex- citation, the photon energy is above the band gaps of ferroelectrics, leading to a much stronger absorption and a shorter penetration depth...preventing light from entering the substrate. UV excitation near the band gap also leads to strong resonance enhancement of Raman sig- nals. This is

  19. The origin of ultrahigh piezoelectricity in relaxor-ferroelectric solid solution crystals

    PubMed Central

    Li, Fei; Zhang, Shujun; Yang, Tiannan; Xu, Zhuo; Zhang, Nan; Liu, Gang; Wang, Jianjun; Wang, Jianli; Cheng, Zhenxiang; Ye, Zuo-Guang; Luo, Jun; Shrout, Thomas R.; Chen, Long-Qing

    2016-01-01

    The discovery of ultrahigh piezoelectricity in relaxor-ferroelectric solid solution single crystals is a breakthrough in ferroelectric materials. A key signature of relaxor-ferroelectric solid solutions is the existence of polar nanoregions, a nanoscale inhomogeneity, that coexist with normal ferroelectric domains. Despite two decades of extensive studies, the contribution of polar nanoregions to the underlying piezoelectric properties of relaxor ferroelectrics has yet to be established. Here we quantitatively characterize the contribution of polar nanoregions to the dielectric/piezoelectric responses of relaxor-ferroelectric crystals using a combination of cryogenic experiments and phase-field simulations. The contribution of polar nanoregions to the room-temperature dielectric and piezoelectric properties is in the range of 50–80%. A mesoscale mechanism is proposed to reveal the origin of the high piezoelectricity in relaxor ferroelectrics, where the polar nanoregions aligned in a ferroelectric matrix can facilitate polarization rotation. This mechanism emphasizes the critical role of local structure on the macroscopic properties of ferroelectric materials. PMID:27991504

  20. The origin of ultrahigh piezoelectricity in relaxor-ferroelectric solid solution crystals

    NASA Astrophysics Data System (ADS)

    Li, Fei; Zhang, Shujun; Yang, Tiannan; Xu, Zhuo; Zhang, Nan; Liu, Gang; Wang, Jianjun; Wang, Jianli; Cheng, Zhenxiang; Ye, Zuo-Guang; Luo, Jun; Shrout, Thomas R.; Chen, Long-Qing

    2016-12-01

    The discovery of ultrahigh piezoelectricity in relaxor-ferroelectric solid solution single crystals is a breakthrough in ferroelectric materials. A key signature of relaxor-ferroelectric solid solutions is the existence of polar nanoregions, a nanoscale inhomogeneity, that coexist with normal ferroelectric domains. Despite two decades of extensive studies, the contribution of polar nanoregions to the underlying piezoelectric properties of relaxor ferroelectrics has yet to be established. Here we quantitatively characterize the contribution of polar nanoregions to the dielectric/piezoelectric responses of relaxor-ferroelectric crystals using a combination of cryogenic experiments and phase-field simulations. The contribution of polar nanoregions to the room-temperature dielectric and piezoelectric properties is in the range of 50-80%. A mesoscale mechanism is proposed to reveal the origin of the high piezoelectricity in relaxor ferroelectrics, where the polar nanoregions aligned in a ferroelectric matrix can facilitate polarization rotation. This mechanism emphasizes the critical role of local structure on the macroscopic properties of ferroelectric materials.

  1. Direct evidence of strong local ferroelectric ordering in a thermoelectric semiconductor

    SciTech Connect

    Aggarwal, Leena; Sekhon, Jagmeet S.; Arora, Ashima; Sheet, Goutam; Guin, Satya N.; Negi, Devendra S.; Datta, Ranjan; Biswas, Kanishka

    2014-09-15

    It is thought that the proposed new family of multi-functional materials, namely, the ferroelectric thermoelectrics may exhibit enhanced functionalities due to the coupling of the thermoelectric parameters with ferroelectric polarization in solids. Therefore, the ferroelectric thermoelectrics are expected to be of immense technological and fundamental significance. As a first step towards this direction, it is most important to identify the existing high performance thermoelectric materials exhibiting ferroelectricity. Herein, through the direct measurement of local polarization switching, we show that the recently discovered thermoelectric semiconductor AgSbSe{sub 2} has local ferroelectric ordering. Using piezo-response force microscopy, we demonstrate the existence of nanometer scale ferroelectric domains that can be switched by external electric field. These observations are intriguing as AgSbSe{sub 2} crystalizes in cubic rock-salt structure with centro-symmetric space group (Fm–3m), and therefore, no ferroelectricity is expected. However, from high resolution transmission electron microscopy measurement, we found the evidence of local superstructure formation which, we believe, leads to local distortion of the centro-symmetric arrangement in AgSbSe{sub 2} and gives rise to the observed ferroelectricity. Stereochemically active 5S{sup 2} lone-pair of Sb may also give rise to local structural distortion thereby creating ferroelectricity in AgSbSe{sub 2}.

  2. The origin of ultrahigh piezoelectricity in relaxor-ferroelectric solid solution crystals

    SciTech Connect

    Li, Fei; Zhang, Shujun; Yang, Tiannan; Xu, Zhuo; Zhang, Nan; Liu, Gang; Wang, Jianjun; Wang, Jianli; Cheng, Zhenxiang; Ye, Zuo-Guang; Luo, Jun; Shrout, Thomas R.; Chen, Long-Qing

    2016-12-19

    The discovery of ultrahigh piezoelectricity in relaxor-ferroelectric solid solution single crystals is a breakthrough in ferroelectric materials. A key signature of relaxor-ferroelectric solid solutions is the existence of polar nanoregions, a nanoscale inhomogeneity, that coexist with normal ferroelectric domains. Despite two decades of extensive studies, the contribution of polar nanoregions to the underlying piezoelectric properties of relaxor ferroelectrics has yet to be established. Here we quantitatively characterize the contribution of polar nanoregions to the dielectric/piezoelectric responses of relaxor-ferroelectric crystals using a combination of cryogenic experiments and phase-field simulations. The contribution of polar nanoregions to the room-temperature dielectric and piezoelectric properties is in the range of 50–80%. A mesoscale mechanism is proposed to reveal the origin of the high piezoelectricity in relaxor ferroelectrics, where the polar nanoregions aligned in a ferroelectric matrix can facilitate polarization rotation. This mechanism emphasizes the critical role of local structure on the macroscopic properties of ferroelectric materials.

  3. Physical aspects of ferroelectric semiconductors for photovoltaic solar energy conversion

    NASA Astrophysics Data System (ADS)

    Lopez-Varo, Pilar; Bertoluzzi, Luca; Bisquert, Juan; Alexe, Marin; Coll, Mariona; Huang, Jinsong; Jimenez-Tejada, Juan Antonio; Kirchartz, Thomas; Nechache, Riad; Rosei, Federico; Yuan, Yongbo

    2016-10-01

    Solar energy conversion using semiconductors to fabricate photovoltaic devices relies on efficient light absorption, charge separation of electron-hole pair carriers or excitons, and fast transport and charge extraction to counter recombination processes. Ferroelectric materials are able to host a permanent electrical polarization which provides control over electrical field distribution in bulk and interfacial regions. In this review, we provide a critical overview of the physical principles and mechanisms of solar energy conversion using ferroelectric semiconductors and contact layers, as well as the main achievements reported so far. In a ferroelectric semiconductor film with ideal contacts, the polarization charge would be totally screened by the metal layers and no charge collection field would exist. However, real materials show a depolarization field, smooth termination of polarization, and interfacial energy barriers that do provide the control of interface and bulk electric field by switchable spontaneous polarization. We explore different phenomena as the polarization-modulated Schottky-like barriers at metal/ferroelectric interfaces, depolarization fields, vacancy migration, and the switchable rectifying behavior of ferroelectric thin films. Using a basic physical model of a solar cell, our analysis provides a general picture of the influence of ferroelectric effects on the actual power conversion efficiency of the solar cell device, and we are able to assess whether these effects or their combinations are beneficial or counterproductive. We describe in detail the bulk photovoltaic effect and the contact layers that modify the built-in field and the charge injection and separation in bulk heterojunction organic cells as well as in photocatalytic and water splitting devices. We also review the dominant families of ferroelectric materials that have been most extensively investigated and have provided the best photovoltaic performance.

  4. The ferroelectric analysis of LCoS

    NASA Astrophysics Data System (ADS)

    Hao, Lifang; Lin, Bin

    2010-11-01

    In order to utilize the LCoS, this paper advances a new patten liquid material which is ferroelectric liquid crystal. It has the characteristics, such as time division-style full-color display, high resolution, low voltage and high speed response. If it is used in the microdisplay, we can attain large area visual display, high open rate and high responding time. The alignment of ferroelectric liquid crystal is very complicated, so we use photo-alignment, rubbing or hybrid-alignment to determine the direction of liquid. Once the liquid layer has been fabricated, we use space parameter method to analyse the liquid layer, and we make sure the detailed optical thickness and pretilted angle.

  5. A-site- and/or B-site-modified PbZrTiO3 materials and (Pb, Sr, Ca, Ba, Mg) (Zr, Ti, Nb, Ta)O3 films having utility in ferroelectric random access memories and high performance thin film microactuators

    NASA Technical Reports Server (NTRS)

    Roeder, Jeffrey F. (Inventor); Chen, Ing-Shin (Inventor); Bilodeau, Steven (Inventor); Baum, Thomas H. (Inventor)

    2001-01-01

    A modified PbZrTiO.sub.3 perovskite crystal material thin film, wherein the PbZrTiO.sub.3 perovskite crystal material includes crystal lattice A-sites and B-sites at least one of which is modified by the presence of a substituent selected from the group consisting of (i) A-site substituents consisting of Sr, Ca, Ba and Mg, and (ii) B-site substituents selected from the group consisting of Nb and Ta. The perovskite crystal thin film material may be formed by liquid delivery MOCVD from metalorganic precursors of the metal components of the thin film, to form PZT and PSZT, and other piezoelectric and ferroelectric thin film materials. The thin films of the invention have utility in non-volatile ferroelectric memory devices (NV-FeRAMs), and in microelectromechanical systems (MEMS) as sensor and/or actuator elements, e.g., high speed digital system actuators requiring low input power levels.

  6. Conduction at a ferroelectric interface

    SciTech Connect

    Marshall, Matthew S. J.; Malashevich, Andrei; Disa, Ankit S.; Han, Myung -Geun; Chen, Hanghui; Zhu, Yimei; Ismail-Beigi, Sohrab; Walker, Frederick J.; Ahn, Charles H.

    2014-11-05

    Typical logic elements utilizing the field effect rely on the change in carrier concentration due to the field in the channel region of the device. Ferroelectric-field-effect devices provide a nonvolatile version of this effect due to the stable polarization order parameter in the ferroelectric. In this study, we describe an oxide/oxide ferroelectric heterostructure device based on (001)-oriented PbZr₀̣.₂Ti₀.₈O₃-LaNiO₃ where the dominant change in conductivity is a result of a significant mobility change in the interfacial channel region. The effect is confined to a few atomic layers at the interface and is reversible by switching the ferroelectric polarization. More interestingly, in one polarization state, the field effect induces a 1.7 eV shift of the interfacial bands to create a new conducting channel in the interfacial PbO layer of the ferroelectric.

  7. Conduction at a ferroelectric interface

    DOE PAGES

    Marshall, Matthew S. J.; Malashevich, Andrei; Disa, Ankit S.; ...

    2014-11-05

    Typical logic elements utilizing the field effect rely on the change in carrier concentration due to the field in the channel region of the device. Ferroelectric-field-effect devices provide a nonvolatile version of this effect due to the stable polarization order parameter in the ferroelectric. In this study, we describe an oxide/oxide ferroelectric heterostructure device based on (001)-oriented PbZr₀̣.₂Ti₀.₈O₃-LaNiO₃ where the dominant change in conductivity is a result of a significant mobility change in the interfacial channel region. The effect is confined to a few atomic layers at the interface and is reversible by switching the ferroelectric polarization. More interestingly, inmore » one polarization state, the field effect induces a 1.7 eV shift of the interfacial bands to create a new conducting channel in the interfacial PbO layer of the ferroelectric.« less

  8. Why is the electrocaloric effect so small in ferroelectrics?

    NASA Astrophysics Data System (ADS)

    Guzmán-Verri, G. G.; Littlewood, P. B.

    2016-06-01

    Ferroelectrics are attractive candidate materials for environmentally friendly solid state refrigeration free of greenhouse gases. Their thermal response upon variations of external electric fields is largest in the vicinity of their phase transitions, which may occur near room temperature. The magnitude of the effect, however, is too small for useful cooling applications even when they are driven close to dielectric breakdown. Insight from microscopic theory is therefore needed to characterize materials and provide guiding principles to search for new ones with enhanced electrocaloric performance. Here, we derive from well-known microscopic models of ferroelectricity meaningful figures of merit for a wide class of ferroelectric materials. Such figures of merit provide insight into the relation between the strength of the effect and the characteristic interactions of ferroelectrics such as dipolar forces. We find that the long range nature of these interactions results in a small effect. A strategy is proposed to make it larger by shortening the correlation lengths of fluctuations of polarization. In addition, we bring into question other widely used but empirical figures of merit and facilitate understanding of the recently observed secondary broad peak in the electrocalorics of relaxor ferroelectrics.

  9. Some strategies for improving caloric responses with ferroelectrics

    NASA Astrophysics Data System (ADS)

    Liu, Yang; Scott, James F.; Dkhil, Brahim

    2016-06-01

    Many important breakthroughs and significant engineering developments have been achieved during the past two decades in the field of caloric materials. In this review, we address ferroelectrics emerging as ideal materials which permit both giant elastocaloric and/or electrocaloric responses near room temperature. We summarize recent strategies for improving caloric responses using geometrical optimization, maximizing the number of coexisting phases, combining positive and negative caloric responses, introducing extra degree of freedom like mechanical stress/pressure, and multicaloric effect driven by either single stimulus or multiple stimuli. This review highlights the promising perspective of ferroelectrics for developing next-generation solid-state refrigeration.

  10. Ferroelectric optical image comparator

    DOEpatents

    Butler, M.A.; Land, C.E.; Martin, S.J.; Pfeifer, K.B.

    1993-11-30

    A ferroelectric optical image comparator has a lead lanthanum zirconate titanate thin-film device which is constructed with a semi-transparent or transparent conductive first electrode on one side of the thin film, a conductive metal second electrode on the other side of the thin film, and the second electrode is in contact with a nonconducting substrate. A photoinduced current in the device represents the dot product between a stored image and an image projected onto the first electrode. One-dimensional autocorrelations are performed by measuring this current while displacing the projected image. 7 figures.

  11. Ferroelectric optical image comparator

    DOEpatents

    Butler, Michael A.; Land, Cecil E.; Martin, Stephen J.; Pfeifer, Kent B.

    1993-01-01

    A ferroelectric optical image comparator has a lead lanthanum zirconate titanate thin-film device which is constructed with a semi-transparent or transparent conductive first electrode on one side of the thin film, a conductive metal second electrode on the other side of the thin film, and the second electrode is in contact with a nonconducting substrate. A photoinduced current in the device represents the dot product between a stored image and an image projected onto the first electrode. One-dimensional autocorrelations are performed by measuring this current while displacing the projected image.

  12. Prediction of a native ferroelectric metal

    NASA Astrophysics Data System (ADS)

    Filippetti, Alessio; Fiorentini, Vincenzo; Ricci, Francesco; Delugas, Pietro; Íñiguez, Jorge

    2016-04-01

    Over 50 years ago, Anderson and Blount discussed symmetry-allowed polar distortions in metals, spawning the idea that a material might be simultaneously metallic and ferroelectric. While many studies have ever since considered such or similar situations, actual ferroelectricity--that is, the existence of a switchable intrinsic electric polarization--has not yet been attained in a metal, and is in fact generally deemed incompatible with the screening by mobile conduction charges. Here we refute this common wisdom and show, by means of first-principles simulations, that native metallicity and ferroelectricity coexist in the layered perovskite Bi5Ti5O17. We show that, despite being a metal, Bi5Ti5O17 can sustain a sizable potential drop along the polar direction, as needed to reverse its polarization by an external bias. We also reveal striking behaviours, as the self-screening mechanism at work in thin Bi5Ti5O17 layers, emerging from the interplay between polar distortions and carriers in this compound.

  13. Tunable Microwave Filter Design Using Thin-Film Ferroelectric Varactors

    NASA Astrophysics Data System (ADS)

    Haridasan, Vrinda

    Military, space, and consumer-based communication markets alike are moving towards multi-functional, multi-mode, and portable transceiver units. Ferroelectric-based tunable filter designs in RF front-ends are a relatively new area of research that provides a potential solution to support wideband and compact transceiver units. This work presents design methodologies developed to optimize a tunable filter design for system-level integration, and to improve the performance of a ferroelectric-based tunable bandpass filter. An investigative approach to find the origins of high insertion loss exhibited by these filters is also undertaken. A system-aware design guideline and figure of merit for ferroelectric-based tunable band- pass filters is developed. The guideline does not constrain the filter bandwidth as long as it falls within the range of the analog bandwidth of a system's analog to digital converter. A figure of merit (FOM) that optimizes filter design for a specific application is presented. It considers the worst-case filter performance parameters and a tuning sensitivity term that captures the relation between frequency tunability and the underlying material tunability. A non-tunable parasitic fringe capacitance associated with ferroelectric-based planar capacitors is confirmed by simulated and measured results. The fringe capacitance is an appreciable proportion of the tunable capacitance at frequencies of X-band and higher. As ferroelectric-based tunable capac- itors form tunable resonators in the filter design, a proportionally higher fringe capacitance reduces the capacitance tunability which in turn reduces the frequency tunability of the filter. Methods to reduce the fringe capacitance can thus increase frequency tunability or indirectly reduce the filter insertion-loss by trading off the increased tunability achieved to lower loss. A new two-pole tunable filter topology with high frequency tunability (> 30%), steep filter skirts, wide stopband

  14. Room-temperature ferroelectricity in CuInP2S6 ultrathin flakes

    SciTech Connect

    Liu, Fucai; You, Lu; Seyler, Kyle L.; Li, Xiaobao; Yu, Peng; Lin, Junhao; Wang, Xuewen; Zhou, Jiadong; Wang, Hong; He, Haiyong; Pantelides, Sokrates T.; Zhou, Wu; Sharma, Pradeep; Xu, Xiaodong; Ajayan, Pulickel M.; Wang, Junling; Liu, Zheng

    2016-08-11

    In this study, two-dimensional (2D) materials have emerged as promising candidates for various optoelectronic applications based on their diverse electronic properties, ranging from insulating to superconducting. However, cooperative phenomena such as ferroelectricity in the 2D limit have not been well explored. Here, we report room-temperature ferroelectricity in 2D CuInP2S6 (CIPS) with a transition temperature of ~320 K. Switchable polarization is observed in thin CIPS of ~4 nm. To demonstrate the potential of this 2D ferroelectric material, we prepare a van der Waals (vdW) ferroelectric diode formed by CIPS/Si heterostructure, which shows good memory behaviour with on/off ratio of ~100. The addition of ferroelectricity to the 2D family opens up possibilities for numerous novel applications, including sensors, actuators, non-volatile memory devices, and various vdW heterostructures based on 2D ferroelectricity.

  15. Ferroelectric Polarization in Nanocrystalline Hydroxyapatite Thin Films on Silicon

    NASA Astrophysics Data System (ADS)

    Lang, S. B.; Tofail, S. A. M.; Kholkin, A. L.; Wojtaś, M.; Gregor, M.; Gandhi, A. A.; Wang, Y.; Bauer, S.; Krause, M.; Plecenik, A.

    2013-07-01

    Hydroxyapatite nanocrystals in natural form are a major component of bone- a known piezoelectric material. Synthetic hydroxyapatite is widely used in bone grafts and prosthetic pyroelectric coatings as it binds strongly with natural bone. Nanocrystalline synthetic hydroxyapatite films have recently been found to exhibit strong piezoelectricity and pyroelectricity. While a spontaneous polarization in hydroxyapatite has been predicted since 2005, the reversibility of this polarization (i.e. ferroelectricity) requires experimental evidence. Here we use piezoresponse force microscopy to demonstrate that nanocrystalline hydroxyapatite indeed exhibits ferroelectricity: a reversal of polarization under an electrical field. This finding will strengthen investigations on the role of electrical polarization in biomineralization and bone-density related diseases. As hydroxyapatite is one of the most common biocompatible materials, our findings will also stimulate systematic exploration of lead and rare-metal free ferroelectric devices for potential applications in areas as diverse as in vivo and ex vivo energy harvesting, biosensing and electronics.

  16. I-V Characteristics of a Ferroelectric Field Effect Transistor

    NASA Technical Reports Server (NTRS)

    MacLeod, Todd C.; Ho, Fat Duen

    1999-01-01

    There are many possible uses for ferroelectric field effect transistors.To understand their application, a fundamental knowledge of their basic characteristics must first be found. In this research, the current and voltage characteristics of a field effect transistor are described. The effective gate capacitance and charge are derived from experimental data on an actual FFET. The general equation for a MOSFET is used to derive the internal characteristics of the transistor: This equation is modified slightly to describe the FFET characteristics. Experimental data derived from a Radiant Technologies FFET is used to calculate the internal transistor characteristics using fundamental MOSFET equations. The drain current was measured under several different gate and drain voltages and with different initial polarizations on the ferroelectric material in the transistor. Two different polarization conditions were used. One with the gate ferroelectric material polarized with a +9.0 volt write pulse and one with a -9.0 volt pulse.

  17. Ferroelectric Polarization in Nanocrystalline Hydroxyapatite Thin Films on Silicon

    PubMed Central

    Lang, S. B.; Tofail, S. A. M.; Kholkin, A. L.; Wojtaś, M.; Gregor, M.; Gandhi, A. A.; Wang, Y.; Bauer, S.; Krause, M.; Plecenik, A.

    2013-01-01

    Hydroxyapatite nanocrystals in natural form are a major component of bone- a known piezoelectric material. Synthetic hydroxyapatite is widely used in bone grafts and prosthetic pyroelectric coatings as it binds strongly with natural bone. Nanocrystalline synthetic hydroxyapatite films have recently been found to exhibit strong piezoelectricity and pyroelectricity. While a spontaneous polarization in hydroxyapatite has been predicted since 2005, the reversibility of this polarization (i.e. ferroelectricity) requires experimental evidence. Here we use piezoresponse force microscopy to demonstrate that nanocrystalline hydroxyapatite indeed exhibits ferroelectricity: a reversal of polarization under an electrical field. This finding will strengthen investigations on the role of electrical polarization in biomineralization and bone-density related diseases. As hydroxyapatite is one of the most common biocompatible materials, our findings will also stimulate systematic exploration of lead and rare-metal free ferroelectric devices for potential applications in areas as diverse as in vivo and ex vivo energy harvesting, biosensing and electronics. PMID:23884324

  18. Hierarchical ferroelectric and ferrotoroidic polarizations coexistent in nano-metamaterials

    NASA Astrophysics Data System (ADS)

    Shimada, Takahiro; Lich, Le Van; Nagano, Koyo; Wang, Jie; Kitamura, Takayuki

    2015-10-01

    Tailoring materials to obtain unique, or significantly enhanced material properties through rationally designed structures rather than chemical constituents is principle of metamaterial concept, which leads to the realization of remarkable optical and mechanical properties. Inspired by the recent progress in electromagnetic and mechanical metamaterials, here we introduce the concept of ferroelectric nano-metamaterials, and demonstrate through an experiment in silico with hierarchical nanostructures of ferroelectrics using sophisticated real-space phase-field techniques. This new concept enables variety of unusual and complex yet controllable domain patterns to be achieved, where the coexistence between hierarchical ferroelectric and ferrotoroidic polarizations establishes a new benchmark for exploration of complexity in spontaneous polarization ordering. The concept opens a novel route to effectively tailor domain configurations through the control of internal structure, facilitating access to stabilization and control of complex domain patterns that provide high potential for novel functionalities. A key design parameter to achieve such complex patterns is explored based on the parity of junctions that connect constituent nanostructures. We further highlight the variety of additional functionalities that are potentially obtained from ferroelectric nano-metamaterials, and provide promising perspectives for novel multifunctional devices. This study proposes an entirely new discipline of ferroelectric nano-metamaterials, further driving advances in metamaterials research.

  19. Hierarchical ferroelectric and ferrotoroidic polarizations coexistent in nano-metamaterials

    PubMed Central

    Shimada, Takahiro; Lich, Le Van; Nagano, Koyo; Wang, Jie; Kitamura, Takayuki

    2015-01-01

    Tailoring materials to obtain unique, or significantly enhanced material properties through rationally designed structures rather than chemical constituents is principle of metamaterial concept, which leads to the realization of remarkable optical and mechanical properties. Inspired by the recent progress in electromagnetic and mechanical metamaterials, here we introduce the concept of ferroelectric nano-metamaterials, and demonstrate through an experiment in silico with hierarchical nanostructures of ferroelectrics using sophisticated real-space phase-field techniques. This new concept enables variety of unusual and complex yet controllable domain patterns to be achieved, where the coexistence between hierarchical ferroelectric and ferrotoroidic polarizations establishes a new benchmark for exploration of complexity in spontaneous polarization ordering. The concept opens a novel route to effectively tailor domain configurations through the control of internal structure, facilitating access to stabilization and control of complex domain patterns that provide high potential for novel functionalities. A key design parameter to achieve such complex patterns is explored based on the parity of junctions that connect constituent nanostructures. We further highlight the variety of additional functionalities that are potentially obtained from ferroelectric nano-metamaterials, and provide promising perspectives for novel multifunctional devices. This study proposes an entirely new discipline of ferroelectric nano-metamaterials, further driving advances in metamaterials research. PMID:26424484

  20. Performing spectroscopic and specific heat studies of improper ferroelectrics

    NASA Technical Reports Server (NTRS)

    Coleman, L. B.

    1982-01-01

    The results of infrared measurements on Ni-Br, Cu-Cl, and Fe-I boracite improper ferroelectrics and far infrared measurements of Ni-Br boracite are presented. The boracites have the general formula X3B7O3Y, where X = divalent metal and Y = halogen. They undergo a first order phase transition from a high temperature paraelectric phase with cubic symmetry to a ferroelectric phase with orthorhombic symmetry. The boracites are "improper ferroelectrics" since the spontaneous polarization is not the primary order parameter in the cubic-orthorhombic phase transition. Current understanding of these materials is that the primary order parameter is associated with a doubly degenerate zone-boundary phonon in the cubic phase. The degenerate critical modes become homogeneous and split into the A sub 1 and A sub 2 modes in the orthorhombic phase, doubling the volume of the primitive cell. An harmonic coupling between the softing A sub 1 and a low frequency A sub 1 optic mode induces a spontaneous polarization as a secondary effect in the ferroelectric phase. This secondary non-critical nature of the ferroelectric mode earns these materials the "improper" title and is responsible for their unique properties and high figure of merit in detector use.

  1. Ferroelectricity and antiferroelectricity of doped thin HfO2-based films.

    PubMed

    Park, Min Hyuk; Lee, Young Hwan; Kim, Han Joon; Kim, Yu Jin; Moon, Taehwan; Kim, Keum Do; Müller, Johannes; Kersch, Alfred; Schroeder, Uwe; Mikolajick, Thomas; Hwang, Cheol Seong

    2015-03-18

    The recent progress in ferroelectricity and antiferroelectricity in HfO2-based thin films is reported. Most ferroelectric thin film research focuses on perovskite structure materials, such as Pb(Zr,Ti)O3, BaTiO3, and SrBi2Ta2O9, which are considered to be feasible candidate materials for non-volatile semiconductor memory devices. However, these conventional ferroelectrics suffer from various problems including poor Si-compatibility, environmental issues related to Pb, large physical thickness, low resistance to hydrogen, and small bandgap. In 2011, ferroelectricity in Si-doped HfO2 thin films was first reported. Various dopants, such as Si, Zr, Al, Y, Gd, Sr, and La can induce ferro-electricity or antiferroelectricity in thin HfO2 films. They have large remanent polarization of up to 45 μC cm(-2), and their coercive field (≈1-2 MV cm(-1)) is larger than conventional ferroelectric films by approximately one order of magnitude. Furthermore, they can be extremely thin (<10 nm) and have a large bandgap (>5 eV). These differences are believed to overcome the barriers of conventional ferroelectrics in memory applications, including ferroelectric field-effect-transistors and three-dimensional capacitors. Moreover, the coupling of electric and thermal properties of the antiferroelectric thin films is expected to be useful for various applications, including energy harvesting/storage, solid-state-cooling, and infrared sensors.

  2. Ferroelectric tunneling under bias voltages

    NASA Astrophysics Data System (ADS)

    Ma, Z. J.; Chen, G.; Zhou, P.; Mei, Z. H.; Zhang, T. J.

    2017-01-01

    Theoretical investigations of ferroelectric tunneling in a SrRuO3/BaTiO3/Pt junction were conducted, and critical expressions for the surface charge density in the electrodes and the potential distribution across the tunnel junction were derived. It was found that the screening charges associated with the ferroelectric polarization and the charging effect of the capacitor jointly contribute to the charges in the electrodes. A current-voltage study simulating the ‘read’ operation indicated that the tunneling electroresistance effect increases with the ferroelectric thickness, and the tunneling electroresistance values agree well with experimental results.

  3. Spectroscopic signature for ferroelectric ice

    NASA Astrophysics Data System (ADS)

    Wójcik, Marek J.; Gług, Maciej; Boczar, Marek; Boda, Łukasz

    2014-09-01

    Various forms of ice exist within our galaxy. Particularly intriguing type of ice - ‘ferroelectric ice' was discovered experimentally and is stable in temperatures below 72 K. This form of ice can generate enormous electric fields and can play an important role in planetary formation. In this letter we present Car-Parrinello simulation of infrared spectra of ferroelectric ice and compare them with spectra of hexagonal ice. Librational region of the spectra can be treated as spectroscopic signature of ice XI and can be of help to identify ferroelectric ice in the Universe.

  4. Stress effects in ferroelectric perovskite thin-films

    NASA Astrophysics Data System (ADS)

    Zednik, Ricardo Johann

    The exciting class of ferroelectric materials presents the engineer with an array of unique properties that offer promise in a variety of applications; these applications include infra-red detectors ("night-vision imaging", pyroelectricity), micro-electro-mechanical-systems (MEMS, piezoelectricity), and non-volatile memory (NVM, ferroelectricity). Realizing these modern devices often requires perovskite-based ferroelectric films thinner than 100 nm. Two such technologically important material systems are (Ba,Sr)TiO3 (BST), for tunable dielectric devices employed in wireless communications, and Pb(Zr,Ti)O3 (PZT), for ferroelectric non-volatile memory (FeRAM). In general, the material behavior is strongly influenced by the mechanical boundary conditions imposed by the substrate and surrounding layers and may vary considerably from the known bulk behavior. A better mechanistic understanding of these effects is essential for harnessing the full potential of ferroelectric thin-films and further optimizing existing devices. Both materials share a common crystal structure and similar properties, but face unique challenges due to the design parameters of these different applications. Tunable devices often require very low dielectric loss as well as large dielectric tunability. Present results show that the dielectric response of BST thin-films can either resemble a dipole-relaxor or follow the accepted empirical Universal Relaxation Law (Curie-von Schweidler), depending on temperature. These behaviors in a single ferroelectric thin-film system are often thought to be mutually exclusive. In state-of-the-art high density FeRAM, the ferroelectric polarization is at least as important as the dielectric response. It was found that these properties are significantly affected by moderate biaxial tensile and compressive stresses which reversibly alter the ferroelastic domain populations of PZT at room temperature. The 90-degree domain wall motion observed by high resolution

  5. Athermal domain-wall creep near a ferroelectric quantum critical point

    NASA Astrophysics Data System (ADS)

    Kagawa, Fumitaka; Minami, Nao; Horiuchi, Sachio; Tokura, Yoshinori

    2016-02-01

    Ferroelectric domain walls are typically stationary because of the presence of a pinning potential. Nevertheless, thermally activated, irreversible creep motion can occur under a moderate electric field, thereby underlying rewritable and non-volatile memory applications. Conversely, as the temperature decreases, the occurrence of creep motion becomes less likely and eventually impossible under realistic electric-field magnitudes. Here we show that such frozen ferroelectric domain walls recover their mobility under the influence of quantum fluctuations. Nonlinear permittivity and polarization-retention measurements of an organic charge-transfer complex reveal that ferroelectric domain-wall creep occurs via an athermal process when the system is tuned close to a pressure-driven ferroelectric quantum critical point. Despite the heavy masses of material building blocks such as molecules, the estimated effective mass of the domain wall is comparable to the proton mass, indicating the realization of a ferroelectric domain wall with a quantum-particle nature near the quantum critical point.

  6. Directionally tunable and mechanically deformable ferroelectric crystals from rotating polar globular ionic molecules

    NASA Astrophysics Data System (ADS)

    Harada, Jun; Shimojo, Takafumi; Oyamaguchi, Hideaki; Hasegawa, Hiroyuki; Takahashi, Yukihiro; Satomi, Koichiro; Suzuki, Yasutaka; Kawamata, Jun; Inabe, Tamotsu

    2016-10-01

    Ferroelectrics are used in a wide range of applications, including memory elements, capacitors and sensors. Recently, molecular ferroelectric crystals have attracted interest as viable alternatives to conventional ceramic ferroelectrics because of their solution processability and lack of toxicity. Here we show that a class of molecular compounds—known as plastic crystals—can exhibit ferroelectricity if the constituents are judiciously chosen from polar ionic molecules. The intrinsic features of plastic crystals, for example, the rotational motion of molecules and phase transitions with lattice-symmetry changes, provide the crystals with unique ferroelectric properties relative to those of conventional molecular crystals. This allows a flexible alteration of the polarization axis direction in a grown crystal by applying an electric field. Owing to the tunable nature of the crystal orientation, together with mechanical deformability, this type of molecular crystal represents an attractive functional material that could find use in a diverse range of applications.

  7. Athermal domain-wall creep near a ferroelectric quantum critical point

    PubMed Central

    Kagawa, Fumitaka; Minami, Nao; Horiuchi, Sachio; Tokura, Yoshinori

    2016-01-01

    Ferroelectric domain walls are typically stationary because of the presence of a pinning potential. Nevertheless, thermally activated, irreversible creep motion can occur under a moderate electric field, thereby underlying rewritable and non-volatile memory applications. Conversely, as the temperature decreases, the occurrence of creep motion becomes less likely and eventually impossible under realistic electric-field magnitudes. Here we show that such frozen ferroelectric domain walls recover their mobility under the influence of quantum fluctuations. Nonlinear permittivity and polarization-retention measurements of an organic charge-transfer complex reveal that ferroelectric domain-wall creep occurs via an athermal process when the system is tuned close to a pressure-driven ferroelectric quantum critical point. Despite the heavy masses of material building blocks such as molecules, the estimated effective mass of the domain wall is comparable to the proton mass, indicating the realization of a ferroelectric domain wall with a quantum-particle nature near the quantum critical point. PMID:26880041

  8. Ferroelectric polymer networks with high energy density and improved discharged efficiency for dielectric energy storage.

    PubMed

    Khanchaitit, Paisan; Han, Kuo; Gadinski, Matthew R; Li, Qi; Wang, Qing

    2013-01-01

    Ferroelectric polymers are being actively explored as dielectric materials for electrical energy storage applications. However, their high dielectric constants and outstanding energy densities are accompanied by large dielectric loss due to ferroelectric hysteresis and electrical conduction, resulting in poor charge-discharge efficiencies under high electric fields. To address this long-standing problem, here we report the ferroelectric polymer networks exhibiting significantly reduced dielectric loss, superior polarization and greatly improved breakdown strength and reliability, while maintaining their fast discharge capability at a rate of microseconds. These concurrent improvements lead to unprecedented charge-discharge efficiencies and large values of the discharged energy density and also enable the operation of the ferroelectric polymers at elevated temperatures, which clearly outperforms the melt-extruded ferroelectric polymer films that represents the state of the art in dielectric polymers. The simplicity and scalability of the described method further suggest their potential for high energy density capacitors.

  9. Athermal domain-wall creep near a ferroelectric quantum critical point.

    PubMed

    Kagawa, Fumitaka; Minami, Nao; Horiuchi, Sachio; Tokura, Yoshinori

    2016-02-16

    Ferroelectric domain walls are typically stationary because of the presence of a pinning potential. Nevertheless, thermally activated, irreversible creep motion can occur under a moderate electric field, thereby underlying rewritable and non-volatile memory applications. Conversely, as the temperature decreases, the occurrence of creep motion becomes less likely and eventually impossible under realistic electric-field magnitudes. Here we show that such frozen ferroelectric domain walls recover their mobility under the influence of quantum fluctuations. Nonlinear permittivity and polarization-retention measurements of an organic charge-transfer complex reveal that ferroelectric domain-wall creep occurs via an athermal process when the system is tuned close to a pressure-driven ferroelectric quantum critical point. Despite the heavy masses of material building blocks such as molecules, the estimated effective mass of the domain wall is comparable to the proton mass, indicating the realization of a ferroelectric domain wall with a quantum-particle nature near the quantum critical point.

  10. Ferroelectric capacitor with reduced imprint

    DOEpatents

    Evans, Jr., Joseph T.; Warren, William L.; Tuttle, Bruce A.; Dimos, Duane B.; Pike, Gordon E.

    1997-01-01

    An improved ferroelectric capacitor exhibiting reduced imprint effects in comparison to prior art capacitors. A capacitor according to the present invention includes top and bottom electrodes and a ferroelectric layer sandwiched between the top and bottom electrodes, the ferroelectric layer comprising a perovskite structure of the chemical composition ABO.sub.3 wherein the B-site comprises first and second elements and a dopant element that has an oxidation state greater than +4. The concentration of the dopant is sufficient to reduce shifts in the coercive voltage of the capacitor with time. In the preferred embodiment of the present invention, the ferroelectric element comprises Pb in the A-site, and the first and second elements are Zr and Ti, respectively. The preferred dopant is chosen from the group consisting of Niobium, Tantalum, and Tungsten. In the preferred embodiment of the present invention, the dopant occupies between 1 and 8% of the B-sites.

  11. Ferroelectricity in one unit-cell period oxide superlattices

    NASA Astrophysics Data System (ADS)

    Noh, T. W.; Lee, J. H.; Lee, H. N.

    2005-03-01

    We present electric properties of one unit-cell period superlattices composed of CaTiO3 (CTO), SrTiO3 (STO), and BaTiO3 (BTO) perovskites, in which the structural symmetry and lattice misfit strain can be systematically varied without changing the chemical valence states. The one unit-cell period CTO/BTO, BTO/STO, and CTO/STO superlattices were grown by high oxygen pressure pulsed laser deposition on atomically flat SrRuO3 conducting oxide grown on STO (001) substrates. CTO/BTO and BTO/STO showed ferroelectricity in room temperature, while CTO/STO showed paraelectric behavior. Such spontaneous electric polarization was an unexpected result, because all TiO6 octahedron was not in the same structural condition with ferroelectric BTO, but was sandwiched by CaO (SrO) and BaO layers in these superlattices. By performing first principle calculations, ferroelectric ground states can be found in the distorted TiO6. Moreover, the ferroelectricity was described as the collective displacement of the titanium-oxygen-titanium ions, which is different from that of bulk ferroelectric material.

  12. Complex oxide ferroelectrics: Electrostatic doping by domain walls

    DOE PAGES

    Maksymovych, Petro

    2015-06-19

    Electrically conducting interfaces can form, rather unexpectedly, by breaking the translational symmetry of electrically insulating complex oxides. For example, a nanometre-thick heteroepitaxial interface between electronically insulating LaAlO3 and SrTiO3 supports a 2D electron gas1 with high mobility of >1,000 cm2 V-1 s-1 (ref. 2). Such interfaces can exhibit magnetism, superconductivity and phase transitions that may form the functional basis of future electronic devices2. A peculiar conducting interface can be created within a polar ferroelectric oxide by breaking the translational symmetry of the ferroelectric order parameter and creating a so-called ferroelectric domain wall (Fig. 1a,b). If the direction of atomic displacementsmore » changes at the wall in such a way as to create a discontinuity in the polarization component normal to the wall (Fig. 1a), the domain wall becomes electrostatically charged. It may then attract compensating mobile charges of opposite sign produced by dopant ionization, photoexcitation or other effects, thereby locally, electrostatically doping the host ferroelectric film. In contrast to conductive interfaces between epitaxially grown oxides, domain walls can be reversibly created, positioned and shaped by electric fields, enabling reconfigurable circuitry within the same volume of the material. Now, writing in Nature Nanotechnology, Arnaud Crassous and colleagues at EPFL and University of Geneva demonstrate control and stability of charged conducting domain walls in ferroelectric thin films of BiFeO3 down to the nanoscale.« less

  13. Graphene-ferroelectric hybrid structure for flexible transparent electrodes.

    PubMed

    Ni, Guang-Xin; Zheng, Yi; Bae, Sukang; Tan, Chin Yaw; Kahya, Orhan; Wu, Jing; Hong, Byung Hee; Yao, Kui; Özyilmaz, Barbaros

    2012-05-22

    Graphene has exceptional optical, mechanical, and electrical properties, making it an emerging material for novel optoelectronics, photonics, and flexible transparent electrode applications. However, the relatively high sheet resistance of graphene is a major constraint for many of these applications. Here we propose a new approach to achieve low sheet resistance in large-scale CVD monolayer graphene using nonvolatile ferroelectric polymer gating. In this hybrid structure, large-scale graphene is heavily doped up to 3 × 10(13) cm(-2) by nonvolatile ferroelectric dipoles, yielding a low sheet resistance of 120 Ω/□ at ambient conditions. The graphene-ferroelectric transparent conductors (GFeTCs) exhibit more than 95% transmittance from the visible to the near-infrared range owing to the highly transparent nature of the ferroelectric polymer. Together with its excellent mechanical flexibility, chemical inertness, and the simple fabrication process of ferroelectric polymers, the proposed GFeTCs represent a new route toward large-scale graphene-based transparent electrodes and optoelectronics.

  14. Ferroelectric Fluoride Memory FET Development

    DTIC Science & Technology

    1993-10-01

    After’ First Metal Definition ..................... 53 Figure 3-30: Initial BMF FEMFETs Demonstrated Ferroelectric Behavior ................ 57 I Figure...as bismuth titanate. 2.0 INTRODUCTION The concept of a thin film ferroelectric memory field-effect transistor (FEMFET) is not new. The first FEMFET...candidate for these studies. BaF2, and MgF 2 have similar melting and evaporation temperatures, and their vapor pressures were also found to be comparable

  15. Dielectric relaxation and charged domain walls in (K,Na)NbO3-based ferroelectric ceramics

    NASA Astrophysics Data System (ADS)

    Esin, A. A.; Alikin, D. O.; Turygin, A. P.; Abramov, A. S.; Hreščak, J.; Walker, J.; Rojac, T.; Bencan, A.; Malic, B.; Kholkin, A. L.; Shur, V. Ya.

    2017-02-01

    The influence of domain walls on the macroscopic properties of ferroelectric materials is a well known phenomenon. Commonly, such "extrinsic" contributions to dielectric permittivity are discussed in terms of domain wall displacements under external electric field. In this work, we report on a possible contribution of charged domain walls to low frequency (10-106 Hz) dielectric permittivity in K1-xNaxNbO3 ferroelectric ceramics. It is shown that the effective dielectric response increases with increasing domain wall density. The effect has been attributed to the Maxwell-Wagner-Sillars relaxation. The obtained results may open up possibilities for domain wall engineering in various ferroelectric materials.

  16. Clamping effect on the microwave properties of ferroelectric thin films

    NASA Astrophysics Data System (ADS)

    Poplavko, Y.; Cho, N.-I.

    1999-11-01

    Ferroelectric and paraelectric films deposited on dielectric and semiconductor substrates were studied at the frequency range 0.3-100 GHz and temperature interval 300-700 K in comparison with chemically equivalent bulk materials. A dielectric spectroscopy method helps to trace the change of dielectric polarization and dielectric loss mechanisms when the free-stress volume (bulk) ferroelectric is transformed into a thin planar layer (film) that is stressed by its forced accommodation to a rigid substrate. The change in bulk-film properties could be either favourable or an adverse factor for electronic devices.

  17. Engineering ferroelectric tunnel junctions through potential profile shaping

    SciTech Connect

    Boyn, S.; Garcia, V. Fusil, S.; Carrétéro, C.; Garcia, K.; Collin, S.; Deranlot, C.; Bibes, M.; Barthélémy, A.

    2015-06-01

    We explore the influence of the top electrode materials (W, Co, Ni, Ir) on the electronic band profile in ferroelectric tunnel junctions based on super-tetragonal BiFeO{sub 3}. Large variations of the transport properties are observed at room temperature. In particular, the analysis of current vs. voltage curves by a direct tunneling model indicates that the metal/ferroelectric interfacial barrier height increases with the top-electrode work function. While larger metal work functions result in larger OFF/ON ratios, they also produce a large internal electric field which results in large and potentially destructive switching voltages.

  18. Ferroelectric Smectic Phase Formed by Achiral Straight Core Mesogens

    NASA Astrophysics Data System (ADS)

    Stannarius, Ralf; Li, Jianjun; Weissflog, Wolfgang

    2003-01-01

    We report electro-optic experiments in liquid crystalline freestanding films of achiral hockey stick shaped mesogens with a straight aromatic core. The material forms two smectic mesophases. In the higher temperature phase, a spontaneous polarization exists in the smectic layer plane and the films show polar switching in electric fields. It is the first example of a ferroelectric phase formed by nearly rodlike achiral mesogens. Mirror symmetry of the phase is spontaneously broken. We propose a molecular configuration similar to a synclinic ferroelectric (CSPF) high temperature phase and an anticlinic, probably antiferroelectric (CAPA) low temperature phase.

  19. First-principles theory, coarse-grained models, and simulations of ferroelectrics.

    PubMed

    Waghmare, Umesh V

    2014-11-18

    CONSPECTUS: A ferroelectric crystal exhibits macroscopic electric dipole or polarization arising from spontaneous ordering of its atomic-scale dipoles that breaks inversion symmetry. Changes in applied pressure or electric field generate changes in electric polarization in a ferroelectric, defining its piezoelectric and dielectric properties, respectively, which make it useful as an electromechanical sensor and actuator in a number of applications. In addition, a characteristic of a ferroelectric is the presence of domains or states with different symmetry equivalent orientations of spontaneous polarization that are switchable with large enough applied electric field, a nonlinear property that makes it useful for applications in nonvolatile memory devices. Central to these properties of a ferroelectric are the phase transitions it undergoes as a function of temperature that involve lowering of the symmetry of its high temperature centrosymmetric paraelectric phase. Ferroelectricity arises from a delicate balance between short and long-range interatomic interactions, and hence the resulting properties are quite sensitive to chemistry, strains, and electric charges associated with its interface with substrate and electrodes. First-principles density functional theoretical (DFT) calculations have been very effective in capturing this and predicting material and environment specific properties of ferroelectrics, leading to fundamental insights into origins of ferroelectricity in oxides and chalcogenides uncovering a precise picture of electronic hybridization, topology, and mechanisms. However, use of DFT in molecular dynamics for detailed prediction of ferroelectric phase transitions and associated temperature dependent properties has been limited due to large length and time scales of the processes involved. To this end, it is quite appealing to start with input from DFT calculations and construct material-specific models that are realistic yet simple for use in

  20. The Modification of Ferroelectric Surfaces for Catalysis

    NASA Astrophysics Data System (ADS)

    Herdiech, Matthew William

    Ferroelectrics are a class of materials in which a net dipole can be associated with each repeat unit, resulting in a potentially large electric field through the material. The ability to reversibly switch the polarization direction by applying an external electric field distinguishes ferroelectrics from polar orientations of ordinary materials. Recent studies exploring the reactivity of ferroelectric surfaces toward polar molecules have shown that the heats of adsorption for these molecules are polarization dependent, but the surfaces tend to be unreactive. Despite the inertness of ferroelectric surfaces, their use as supports for catalytically active materials could yield novel reactivity. As even metal oxides that are generally considered inert can influence the catalytic properties of supported layers, a ferroelectric support may offer the opportunity to modulate catalytic activity since charge compensation of the polar surfaces might include chemical and electronic reconstructions of the active layer. In this thesis, the fabrication of active layers with polarization dependent properties was investigated by coating ferroelectric substrates with catalytically active oxides that are likely to grow in a layer-by-layer manner. Two systems in particular were explored: chromium oxide on ferroelectric lithium niobate (Cr2O3/LiNbO3), and ruthenium oxide on ferroelectric lead zirconate titanate (RuO2/Pb(Zr0.2Ti0.8)O 3). The chromium oxide and ruthenium oxide films were characterized with X-ray photoelectron spectroscopy (XPS), low energy electron diffraction (LEED), and reflection high energy electron diffraction (RHEED). Additionally, the chromium oxide films were characterized with X-ray diffraction (XRD) and X-ray reflectivity (XRR) measurements, and the ruthenium oxide films were characterized with ion scattering spectroscopy (ISS) measurements. The reactivity of the films was investigated using temperature programmed desorption (TPD) measurements. In particular

  1. Ferroelectric polymer nanocomposites for room-temperature electrocaloric refrigeration.

    PubMed

    Zhang, Guangzu; Li, Qi; Gu, Haiming; Jiang, Shenglin; Han, Kuo; Gadinski, Matthew R; Haque, Md Amanul; Zhang, Qiming; Wang, Qing

    2015-02-25

    Solution-processable ferroelectric polymer nanocomposites are developed as a new form of electrocaloric materials that can be effectively operated under both modest and high electric fields at ambient temperature. By integrating the complementary properties of the constituents, the nanocomposites exhibit state-of-the-art cooling energy densities. Greatly improved thermal conductivity also yields superior cooling power densities validated by finite volume simulations.

  2. Uncooled monolithic ferroelectric IRFPA technology

    NASA Astrophysics Data System (ADS)

    Belcher, James F.; Hanson, Charles M.; Beratan, Howard R.; Udayakumar, K. R.; Soch, Kevin L.

    1998-10-01

    Once relegated to expensive military platforms, occasionally to civilian platforms, and envisioned for individual soldiers, uncooled thermal imaging affords cost-effective solutions for police cars, commercial surveillance, driving aids, and a variety of other industrial and consumer applications. System prices are continuing to drop, and swelling production volume will soon drive prices substantially lower. The impetus for further development is to improve performance. Hybrid barium strontium titanate (BST) detectors currently in production are relatively inexpensive, but have limited potential for improved performance. The MTF at high frequencies is limited by thermal conduction through the optical coating. Microbolometer arrays in development at Raytheon have recently demonstrated performance superior to hybrid detectors. However, microbolometer technology lacks a mature, low-cost system technology and an abundance of upgradable, deployable system implementations. Thin-film ferroelectric (TFFE) detectors have all the performance potential of microbolometers. They are also compatible with numerous fielded and planned system implementations. Like the resistive microbolometer, the TFFE detector is monolithic; i.e., the detector material is deposited directly on the readout IC rather than being bump bonded to it. Imaging arrays of 240 X 320 pixels have been produced, demonstrating the feasibility of the technology.

  3. Structural, Optical, and Magnetic Properties of Lead-Free Ferroelectric Bi0.5K0.5TiO3 Solid Solution with BiFeO3 Materials

    NASA Astrophysics Data System (ADS)

    Tuan, Nguyen Hoang; Bac, Luong Huu; Cuong, Le Viet; Van Thiet, Duong; Van Tam, Tran; Dung, Dang Duc

    2017-02-01

    A solid solution of Bi0.5K0.5TiO3-BiFeO3 was fabricated by a sol-gel technique. The pure Bi0.5K0.5TO3 samples exhibited weak room-temperature ferromagnetism. The room-temperature ferromagnetism was observed in BiFeO3 solid solution in Bi0.5K0.5TiO3. The optical band gap of Bi0.5K0.5TiO3 was reduced from 3.22 eV to 1.39 eV with the increase in the amount of BiFeO3 solid solution. The room-temperature ferromagnetism and band gap reduction were attributed to the diffusion of BiFeO3 into Bi0.5K0.5TiO3 to form a solid solution. Our work provided a simple method of realizing room-temperature ferromagnetism in lead-free ferroelectric materials.

  4. Conductivity and interfacial charge induced phenomena in ferroelectric films and composites

    NASA Astrophysics Data System (ADS)

    Wong, Chung Kwan

    2005-11-01

    Ferroelectric materials are polar dielectrics which normally possess small but finite electrical conductivity. We believe that conductivity in ferroelectrics can induce new phenomena or modify known physical phenomena, which may be difficult to understand if the materials are regarded as perfectly insulating. In this thesis, some "anomalous" phenomena are investigated for which the origins are still under debate in literature, and we suggest that these may very well be manifestations of electrical conduction and electric charges. Ferroelectric systems of interest to this investigation include composites and films. Electrical conductivity in ferroelectric composites allows free charge to accumulate at the matrix-inclusion interfaces. We focus on the role of interfacial charge at such interfaces in ferroelectric 0--3 composites (normally, ferroelectric ceramic inclusions dispersed in polymer matrices) in the interpretation of their peculiar experimental results. The effect of interfacial charge on the piezoelectric properties of ferroelectric 0--3 composites and the effect of electrical conductivity on their dielectric and piezoelectric properties are also investigated. Our previously developed model has been extended to include the additional contribution from the deformation of the inclusion particles (for discussing the effect of interfacial charge) due to the applied stresses in piezoelectric measurements, and for discussing the effect of conductivity to include its contribution as well as the frequency of measurement. Phenomena induced by electrical conductivity in other ferroelectric systems have also been studied. We consider the effects of electrical conductivity on the dynamic polarization behavior of ferroelectric films. Using a parallelogram-like P-E hysteresis model for the film material, explicit expressions are obtained for describing the D-E loops of ferroelectric films as would be measured from a Sawyer-Tower circuit which originally assumes the

  5. The Soft Mode Driven Dynamics in Ferroelectric Perovskites at the Nanoscale: An Atomistic Study

    NASA Astrophysics Data System (ADS)

    McCash, Kevin

    The discovery of ferroelectricity at the nanoscale has incited a lot of interest in perovskite ferroelectrics not only for their potential in device application but also for their potential to expand fundamental understanding of complex phenomena at very small size scales. Unfortunately, not much is known about the dynamics of ferroelectrics at this scale. Many of the widely held theories for ferroelectric materials are based on bulk dynamics which break down when applied to smaller scales. In an effort to increase understanding of nanoscale ferroelectric materials we use atomistic resolution computational simulations to investigate the dynamics of polar perovskites. Within the framework of a well validated effective Hamiltonian model we are able to accurately predict many of the properties of ferroelectric materials at the nanoscale including the response of the soft mode to mechanical boundary conditions and the polarization reversal dynamics of ferroelectric nanowires. Given that the focus of our study is the dynamics of ferroelectric perovskites we begin by developing an effective Hamiltonian based model that could simultaneously describe both static and dynamic properties of such materials. Our study reveals that for ferroelectric perovskites that undergo a sequence of phase transitions, such as BaTiO3. for example, the minimal parameter effective Hamiltonian model is unable to reproduce both static and dynamical properties simultaneously. Nevertheless we developed two sets of parameters that accurately describes the static properties and dynamic properties of BaTiO3 independently. By creating a tool that accurately models the dynamical properties of perovskite ferroelectrics we are able to investigate the frequencies of the soft modes in the perovskite crystal. The lowest energy transverse optical soft modes in perovskite ferroelectrics are known to be cause of the ferroelectric phase transition in these materials and affect a number of electrical properties

  6. Digital holographic tomography method for 3D observation of domain patterns in ferroelectric single crystals

    NASA Astrophysics Data System (ADS)

    Mokrý, Pavel; Psota, Pavel; Steiger, Kateřina; Václavík, Jan; Vápenka, David; Doleček, Roman; Vojtíšek, Petr; Sládek, Juraj; Lédl, Vít.

    2016-11-01

    We report on the development and implementation of the digital holographic tomography for the three-dimensio- nal (3D) observations of the domain patterns in the ferroelectric single crystals. Ferroelectric materials represent a group of materials, whose macroscopic dielectric, electromechanical, and elastic properties are greatly in uenced by the presence of domain patterns. Understanding the role of domain patterns on the aforementioned properties require the experimental techniques, which allow the precise 3D measurements of the spatial distribution of ferroelectric domains in the single crystal. Unfortunately, such techniques are rather limited at this time. The most frequently used piezoelectric atomic force microscopy allows 2D observations on the ferroelectric sample surface. Optical methods based on the birefringence measurements provide parameters of the domain patterns averaged over the sample volume. In this paper, we analyze the possibility that the spatial distribution of the ferroelectric domains can be obtained by means of the measurement of the wavefront deformation of the transmitted optical wave. We demonstrate that the spatial distribution of the ferroelectric domains can be determined by means of the measurement of the spatial distribution of the refractive index. Finally, it is demonstrated that the measurements of wavefront deformations generated in ferroelectric polydomain systems with small variations of the refractive index provide data, which can be further processed by means of the conventional tomographic methods.

  7. Conducting Ferroelectric Walls, Domain Topology, and Domain Switching Kinetics in a Hybrid Improper Ferroelectric

    NASA Astrophysics Data System (ADS)

    Cheong, Sang-Wook; Rutgers CenterEmergent Materials Team

    Charged polar interfaces such as charged ferroelectric domain walls or heterostructured interfaces of ZnO/(Zn,Mg)O and LaAlO 3 /SrTiO 3 , across which the normal component of electric polarization changes suddenly, can host large two-dimensional conduction. Charged ferroelectric domain walls can be highly conducting but energetically unfavored; however, they were found to be mysteriously abundant in hybrid improper ferroelectric (Ca,Sr) 3 Ti 2 O 7 single crystals. From the exploration of antiphase domain boundaries, which are hidden in piezoresponse force microscopy, using dark-field electron microscopy, we have explored the macroscopic topology of polarization domains and antiphase domains. We found that the macroscopic domain topology is directly responsible for the presence of charged domain walls, and is closely related with the polarization domain switching mechanism in (Ca,Sr) 3 Ti 2 O 7 . Rutgers Center for Emergent Materials and Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey 08854, USA.

  8. Downscaling ferroelectric field effect transistors by using ferroelectric Si-doped HfO2

    NASA Astrophysics Data System (ADS)

    Martin, Dominik; Yurchuk, Ekaterina; Müller, Stefan; Müller, Johannes; Paul, Jan; Sundquist, Jonas; Slesazeck, Stefan; Schlösser, Till; van Bentum, Ralf; Trentzsch, Martin; Schröder, Uwe; Mikolajick, Thomas

    2013-10-01

    Throughout the 22 nm technology node HfO2 is established as a reliable gate dielectric in contemporary complementary metal oxide semiconductor (CMOS) technology. The working principle of ferroelectric field effect transistors FeFET has also been demonstrated for some time for dielectric materials like Pb[ZrxTi1-x]O3 and SrBi2Ta2O9. However, integrating these into contemporary downscaled CMOS technology nodes is not trivial due to the necessity of an extremely thick gate stack. Recent developments have shown HfO2 to have ferroelectric properties, given the proper doping. Moreover, these doped HfO2 thin films only require layer thicknesses similar to the ones already in use in CMOS technology. This work will show how the incorporation of Si induces ferroelectricity in HfO2 based capacitor structures and finally demonstrate non-volatile storage in nFeFETs down to a gate length of 100 nm. A memory window of 0.41 V can be retained after 20,000 switching cycles. Retention can be extrapolated to 10 years.

  9. Ferroelectricity and Self-Polarization in Ultrathin Relaxor Ferroelectric Films.

    PubMed

    Miao, Peixian; Zhao, Yonggang; Luo, Nengneng; Zhao, Diyang; Chen, Aitian; Sun, Zhong; Guo, Meiqi; Zhu, Meihong; Zhang, Huiyun; Li, Qiang

    2016-01-28

    We report ferroelectricity and self-polarization in the (001) oriented ultrathin relaxor ferroelectric PMN-PT films grown on Nb-SrTiO3, SrRuO3 and La0.7Sr0.3MnO3, respectively. Resistance-voltage measurements and AC impedance analysis suggest that at high temperatures Schottky depletion width in a 4 nm thick PMN-PT film deposited on Nb-SrTiO3 is smaller than the film thickness. We propose that Schottky interfacial dipoles make the dipoles of the nanometer-sized polar nanoregions (PNRs) in PMN-PT films grown on Nb-SrTiO3 point downward at high temperatures and lead to the self-polarization at room temperature with the assistance of in-plane compressive strain. This work sheds light on the understanding of epitaxial strain effects on relaxor ferroelectric films and self-polarization mechanism.

  10. Ferroelectricity and Self-Polarization in Ultrathin Relaxor Ferroelectric Films

    NASA Astrophysics Data System (ADS)

    Miao, Peixian; Zhao, Yonggang; Luo, Nengneng; Zhao, Diyang; Chen, Aitian; Sun, Zhong; Guo, Meiqi; Zhu, Meihong; Zhang, Huiyun; Li, Qiang

    2016-01-01

    We report ferroelectricity and self-polarization in the (001) oriented ultrathin relaxor ferroelectric PMN-PT films grown on Nb-SrTiO3, SrRuO3 and La0.7Sr0.3MnO3, respectively. Resistance-voltage measurements and AC impedance analysis suggest that at high temperatures Schottky depletion width in a 4 nm thick PMN-PT film deposited on Nb-SrTiO3 is smaller than the film thickness. We propose that Schottky interfacial dipoles make the dipoles of the nanometer-sized polar nanoregions (PNRs) in PMN-PT films grown on Nb-SrTiO3 point downward at high temperatures and lead to the self-polarization at room temperature with the assistance of in-plane compressive strain. This work sheds light on the understanding of epitaxial strain effects on relaxor ferroelectric films and self-polarization mechanism.

  11. Ferroelectricity and Self-Polarization in Ultrathin Relaxor Ferroelectric Films

    PubMed Central

    Miao, Peixian; Zhao, Yonggang; Luo, Nengneng; Zhao, Diyang; Chen, Aitian; Sun, Zhong; Guo, Meiqi; Zhu, Meihong; Zhang, Huiyun; Li, Qiang

    2016-01-01

    We report ferroelectricity and self-polarization in the (001) oriented ultrathin relaxor ferroelectric PMN-PT films grown on Nb-SrTiO3, SrRuO3 and La0.7Sr0.3MnO3, respectively. Resistance-voltage measurements and AC impedance analysis suggest that at high temperatures Schottky depletion width in a 4 nm thick PMN-PT film deposited on Nb-SrTiO3 is smaller than the film thickness. We propose that Schottky interfacial dipoles make the dipoles of the nanometer-sized polar nanoregions (PNRs) in PMN-PT films grown on Nb-SrTiO3 point downward at high temperatures and lead to the self-polarization at room temperature with the assistance of in-plane compressive strain. This work sheds light on the understanding of epitaxial strain effects on relaxor ferroelectric films and self-polarization mechanism. PMID:26817516

  12. Thin-Film Ferroelectric Tunable Microwave Devices Being Developed

    NASA Technical Reports Server (NTRS)

    VanKeuls, Frederick W.

    1999-01-01

    Electronically tunable microwave components have become the subject of intense research efforts in recent years. Many new communications systems would greatly benefit from these components. For example, planned low Earth orbiting satellite networks have a need for electronically scanned antennas. Thin ferroelectric films are one of the major technologies competing to fill these applications. When a direct-current (dc) voltage is applied to ferroelectric film, the dielectric constant of the film can be decreased by nearly an order of magnitude, changing the high-frequency wavelength in the microwave device. Recent advances in film growth have demonstrated high-quality ferroelectric thin films. This technology may allow microwave devices that have very low power and are compact, lightweight, simple, robust, planar, voltage tunable, and affordable. The NASA Lewis Research Center has been designing, fabricating, and testing proof-of-concept tunable microwave devices. This work, which is being done in-house with funding from the Lewis Director's Discretionary Fund, is focusing on introducing better microwave designs to utilize these materials. We have demonstrated Ku- and K-band phase shifters, tunable local oscillators, tunable filters, and tunable diplexers. Many of our devices employ SrTiO3 as the ferroelectric. Although it is one of the more tunable and easily grown ferroelectrics, SrTiO3 must be used at cryogenic temperatures, usually below 100 K. At these temperatures, we frequently use high-temperature superconducting thin films of YBa2Cu3O7-8 to carry the microwave signals. However, much of our recent work has concentrated on inserting room-temperature ferroelectric thin films, such as BaxSr1- xTiO3 into these devices. The BaxSr1-xTiO3 films are used in conjuction with normal metal conductors, such as gold.

  13. Ferroelectricity in undoped hafnium oxide

    SciTech Connect

    Polakowski, Patrick; Müller, Johannes

    2015-06-08

    We report the observation of ferroelectric characteristics in undoped hafnium oxide thin films in a thickness range of 4–20 nm. The undoped films were fabricated using atomic layer deposition (ALD) and embedded into titanium nitride based metal-insulator-metal (MIM) capacitors for electrical evaluation. Structural as well as electrical evidence for the appearance of a ferroelectric phase in pure hafnium oxide was collected with respect to film thickness and thermal budget applied during titanium nitride electrode formation. Using grazing incidence X-Ray diffraction (GIXRD) analysis, we observed an enhanced suppression of the monoclinic phase fraction in favor of an orthorhombic, potentially, ferroelectric phase with decreasing thickness/grain size and for a titanium nitride electrode formation below crystallization temperature. The electrical presence of ferroelectricity was confirmed using polarization measurements. A remanent polarization P{sub r} of up to 10 μC cm{sup −2} as well as a read/write endurance of 1.6 × 10{sup 5} cycles was measured for the pure oxide. The experimental results reported here strongly support the intrinsic nature of the ferroelectric phase in hafnium oxide and expand its applicability beyond the doped systems.

  14. Phonon anomalies and the ferroelectric phase transition in multiferroic BiFeO3

    NASA Astrophysics Data System (ADS)

    Haumont, R.; Kreisel, J.; Bouvier, P.; Hippert, F.

    2006-04-01

    We report a temperature-dependent Raman scattering investigation of the multiferroic material bismuth ferrite BiFeO3 (BFO). The observed loss of the Raman spectrum at the ferroelectric Curie temperature TC should be in agreement with a cubic Pm3¯m structure of the high-temperature paraelectric phase. Surprisingly, the ferroelectric-to-paraelectric phase transition is not soft-mode driven, indicating a nonconventional ferroelectric. Furthermore, our results reveal pronounced phonon anomalies around the magnetic Néel temperature TN . We tentatively attribute these anomalies to the multiferroic character of BFO.

  15. Photo-induced currents in the sandwich metal-ferroelectric-metal structure

    NASA Astrophysics Data System (ADS)

    Ivanov, V.; Karpets, Yu; Perkov, Yu

    2017-01-01

    It was described the photoelectric effect in thin sandwich metal-ferroelectric-metal system. The effect was observed in doped lithium niobate crystals with two electrodes of different metals. The effect is observed only in doped lithium niobate crystals and has a maximum for concentrations of impurities of iron around 0.3 % weight. This paper proposed thermal model of the investigated phenomena resulting from field contact potential difference on the borders of section of metal-ferroelectric material. The results obtained can be used to develop radiation receivers, as well as in the interpretation of experimental results on studying the properties of sandwiched metal-ferroelectric-metal structure.

  16. Relaxor ferroelectric behavior of poly(vinylidene fluoride-trifluorethylene) copolymer modified by low energy irradiation

    SciTech Connect

    Faria, Luiz O.; Welter, Cezar; Moreira, Roberto L.

    2006-05-08

    We report a relaxorlike modification in the ferroelectric poly(vinylidene fluoride-trifluorethylene) copolymer using ultraviolet (UV) irradiation. This behavior is clearly demonstrated by dielectric measurements. Besides the relaxor feature, the ferroelectric character of the material is retained, also exhibiting Curie transition at barely diminished temperatures. UV-Vis absorption measurements suggests that the UV radiation induces conjugated C=C bonds in the copolymer chains. The coexistence of both relaxor and ferroelectric behavior, the lack of chain cross-linking, and a weak reducing in the crystallinity suggest that the UV-induced defects are not sufficient to completely break up the polarization domains.

  17. New Ferroelectric Aminoguanidinium Hexafluorozirconate

    NASA Astrophysics Data System (ADS)

    Bauer, Matt; Arbogast, Darin; Gallagher, Craig; Christie, Jim; Pugmire, David; Paulsen, Brian; Ross, Charles; Photinos, Panos; Nielson, Roger; Abrahams, Sidney C.

    2000-03-01

    Satisfaction of structural criteria led to the prediction that anhydrous aminoguanidinium hexafluorozirconate CN_4H_8ZrF6 is a new ferroelectric. Calorimetric and dielectric permittivity measurements reveal a highly-reproducible anomaly at the Curie temperature Tc = 383(1) K. The heat capacity undergoes an entropy change of 0.7(1) J mol-1 K-1 at Tc as the relative permittivity increases sharply by nearly an order of magnitude. Dielectric hysteresis at 295 K under the application of 1 MV m-1 ac is also observed at all T < Tc but not at T > T_c, confirming the prediction. Saturation is not reached before electric breakdown above 1 MV m-1 ac. The piezoelectric coefficient d_33 = 1.9 pC N-1 at 298 K. Polarisation reversal requires each symmetry-independent CN_4H_8^+2 ion to tilt and both N NH3 and C (NH_2)2 groups to rotate about the C N bond. Small atomic displacements within the ZrF_6-2 anion lead to mirror symmetry in course of the phase transition.

  18. Improper Ferroelectricity in Stuffed Aluminate Sodalites for Pyroelectric Energy Harvesting

    NASA Astrophysics Data System (ADS)

    Maeda, Yusaku; Wakamatsu, Toru; Konishi, Ayako; Moriwake, Hiroki; Moriyoshi, Chikako; Kuroiwa, Yoshihiro; Tanabe, Kenji; Terasaki, Ichiro; Taniguchi, Hiroki

    2017-03-01

    In the present study, we demonstrate ferroelectricity in stuffed aluminate sodalites (Ca1 -xSrx)8[AlO2]12(WO4)2 (x ≤0.2 ) (C1 -xSxAW ). Pyroelectric measurements clarify switchable spontaneous polarization in polycrystalline C1 -xSxAW , whose polarization values are on the order of 10-2 μ C /cm2 at room temperature. A weak anomaly in the dielectric permittivity at temperatures near the ferroelectric transition temperature suggests improper ferroelectricity of C1 -xSxAW for all investigated values of x . A comprehensive study involving synchrotron x-ray powder diffraction measurements, molecular dynamics simulations, and first-principles calculations clarifies that the ferroelectric phase transition of C1 -xSxAW is driven by the freezing of the fluctuations of WO4 tetrahedra in the voids of an [AlO2]12 12 - framework. The voltage response and electromechanical coupling factor of C1 -xSxAW estimated from the present results indicate that this material exhibits excellent performance as a pyroelectric energy harvester, suggesting that aluminate sodalites exhibit great promise as a class of materials for highly efficient energy-harvesting devices.

  19. Polarization switching in ferroelectric cathodes

    SciTech Connect

    Rosenman, G.; Shur, D.; Garb, K.; Cohen, R.; Krasik, Y.E.

    1997-07-01

    A new mechanism of polarization switching and electron emission in ferroelectric cathodes is proposed. Surface flashover plasma of a ferroelectric origin was observed on a polar ferroelectric surface [D. Shur, G. Rosenman, and Ya. E. Krasik, Appl. Phys. Lett. {bold 70}, 574 (1997)]. Simultaneous measurements of switched charge and plasma density show that expanding surface plasma represents a dynamic switching electrode. Direct measurements of ion/electron emission currents and surface analysis implemented by different analytic tools indicate that electrons and ions from the surface plasma contribute to spontaneous polarization screening. The high energy of charged particles emitted from the surface plasma is ascribed to a high surface potential during polarization switching. {copyright} {ital 1997 American Institute of Physics.}

  20. A strong ferroelectric ferromagnet created by means of spin-lattice coupling.

    PubMed

    Lee, June Hyuk; Fang, Lei; Vlahos, Eftihia; Ke, Xianglin; Jung, Young Woo; Kourkoutis, Lena Fitting; Kim, Jong-Woo; Ryan, Philip J; Heeg, Tassilo; Roeckerath, Martin; Goian, Veronica; Bernhagen, Margitta; Uecker, Reinhard; Hammel, P Chris; Rabe, Karin M; Kamba, Stanislav; Schubert, Jürgen; Freeland, John W; Muller, David A; Fennie, Craig J; Schiffer, Peter; Gopalan, Venkatraman; Johnston-Halperin, Ezekiel; Schlom, Darrell G

    2010-08-19

    Ferroelectric ferromagnets are exceedingly rare, fundamentally interesting multiferroic materials that could give rise to new technologies in which the low power and high speed of field-effect electronics are combined with the permanence and routability of voltage-controlled ferromagnetism. Furthermore, the properties of the few compounds that simultaneously exhibit these phenomena are insignificant in comparison with those of useful ferroelectrics or ferromagnets: their spontaneous polarizations or magnetizations are smaller by a factor of 1,000 or more. The same holds for magnetic- or electric-field-induced multiferroics. Owing to the weak properties of single-phase multiferroics, composite and multilayer approaches involving strain-coupled piezoelectric and magnetostrictive components are the closest to application today. Recently, however, a new route to ferroelectric ferromagnets was proposed by which magnetically ordered insulators that are neither ferroelectric nor ferromagnetic are transformed into ferroelectric ferromagnets using a single control parameter, strain. The system targeted, EuTiO(3), was predicted to exhibit strong ferromagnetism (spontaneous magnetization, approximately 7 Bohr magnetons per Eu) and strong ferroelectricity (spontaneous polarization, approximately 10 microC cm(-2)) simultaneously under large biaxial compressive strain. These values are orders of magnitude higher than those of any known ferroelectric ferromagnet and rival the best materials that are solely ferroelectric or ferromagnetic. Hindered by the absence of an appropriate substrate to provide the desired compression we turned to tensile strain. Here we show both experimentally and theoretically the emergence of a multiferroic state under biaxial tension with the unexpected benefit that even lower strains are required, thereby allowing thicker high-quality crystalline films. This realization of a strong ferromagnetic ferroelectric points the way to high

  1. A strong ferroelectric ferromagnet created by means of spin-lattice coupling.

    SciTech Connect

    Lee, J. H.; Fang, L.; Vlahos, E.; Ke, X.; Jung, Y.W.; Fitting Kourkaoutis, L.; Kim, J. W.; Ryan, P.; Heeg, T.; Roeckerath, M.; Goian, V.; Bernhagen, M.; Uecker, R.; Hammel, P.C.; Rabe, K. M.; Kamba, S.; Schubert, J.; Freeland, J.W.; Muller, D.A.; Fennie, C.J.; Schiffer, P.; Gopalan, V.; Johnston-Halperin, E.; Schlom, D. G.

    2010-08-19

    Ferroelectric ferromagnets are exceedingly rare, fundamentally interesting multiferroic materials that could give rise to new technologies in which the low power and high speed of field-effect electronics are combined with the permanence and routability of voltage-controlled ferromagnetism. Furthermore, the properties of the few compounds that simultaneously exhibit these phenomena are insignificant in comparison with those of useful ferroelectrics or ferromagnets: their spontaneous polarizations or magnetizations are smaller by a factor of 1,000 or more. The same holds for magnetic- or electric-field-induced multiferroics. Owing to the weak properties of single-phase multiferroics, composite and multilayer approaches involving strain-coupled piezoelectric and magnetostrictive components are the closest to application today. Recently, however, a new route to ferroelectric ferromagnets was proposed by which magnetically ordered insulators that are neither ferroelectric nor ferromagnetic are transformed into ferroelectric ferromagnets using a single control parameter, strain. The system targeted, EuTiO{sub 3}, was predicted to exhibit strong ferromagnetism (spontaneous magnetization, {approx}7 Bohr magnetons per Eu) and strong ferroelectricity (spontaneous polarization, {approx}10 {micro}C cm{sup -2}) simultaneously under large biaxial compressive strain. These values are orders of magnitude higher than those of any known ferroelectric ferromagnet and rival the best materials that are solely ferroelectric or ferromagnetic. Hindered by the absence of an appropriate substrate to provide the desired compression we turned to tensile strain. Here we show both experimentally and theoretically the emergence of a multiferroic state under biaxial tension with the unexpected benefit that even lower strains are required, thereby allowing thicker high-quality crystalline films. This realization of a strong ferromagnetic ferroelectric points the way to high

  2. The origin of incipient ferroelectricity in lead telluride.

    PubMed

    Jiang, M P; Trigo, M; Savić, I; Fahy, S; Murray, É D; Bray, C; Clark, J; Henighan, T; Kozina, M; Chollet, M; Glownia, J M; Hoffmann, M C; Zhu, D; Delaire, O; May, A F; Sales, B C; Lindenberg, A M; Zalden, P; Sato, T; Merlin, R; Reis, D A

    2016-07-22

    The interactions between electrons and lattice vibrations are fundamental to materials behaviour. In the case of group IV-VI, V and related materials, these interactions are strong, and the materials exist near electronic and structural phase transitions. The prototypical example is PbTe whose incipient ferroelectric behaviour has been recently associated with large phonon anharmonicity and thermoelectricity. Here we show that it is primarily electron-phonon coupling involving electron states near the band edges that leads to the ferroelectric instability in PbTe. Using a combination of nonequilibrium lattice dynamics measurements and first principles calculations, we find that photoexcitation reduces the Peierls-like electronic instability and reinforces the paraelectric state. This weakens the long-range forces along the cubic direction tied to resonant bonding and low lattice thermal conductivity. Our results demonstrate how free-electron-laser-based ultrafast X-ray scattering can be utilized to shed light on the microscopic mechanisms that determine materials properties.

  3. Multiferroic BaCoF4 in Thin Film Form: Ferroelectricity, Magnetic Ordering, and Strain.

    PubMed

    Borisov, Pavel; Johnson, Trent A; García-Castro, Andrés Camilo; KC, Amit; Schrecongost, Dustin; Cen, Cheng; Romero, Aldo H; Lederman, David

    2016-02-03

    Multiferroic materials have simultaneous magnetic and ferroelectric long-range orders and can be potentially useful for a wide range of applications. Conventional ferroelectricity in oxide perovskites favors nonmagnetic electronic configurations of transition metal ions, thus limiting the number of intrinsic multiferroic materials. On the other hand, this is not necessarily true for multiferroic fluorides. Using molecular beam epitaxy, we demonstrate for the first time that the multiferroic orthorhombic fluoride BaCoF4 can be synthesized in thin film form. Ferroelectric hysteresis measurements and piezoresponse force microscopy show that the films are indeed ferroelectric. From structural information, magnetic measurements, and first-principles calculations, a modified magnetic ground state is identified which can be represented as a combination of bulk collinear antiferromagnetism with two additional canted spin orders oriented along orthogonal axes of the BaCoF4 unit cell. The calculations indicate that an anisotropic epitaxial strain is responsible for this unusual magnetic ground state.

  4. Ferroelectric control of spin polarization.

    PubMed

    Garcia, V; Bibes, M; Bocher, L; Valencia, S; Kronast, F; Crassous, A; Moya, X; Enouz-Vedrenne, S; Gloter, A; Imhoff, D; Deranlot, C; Mathur, N D; Fusil, S; Bouzehouane, K; Barthélémy, A

    2010-02-26

    A current drawback of spintronics is the large power that is usually required for magnetic writing, in contrast with nanoelectronics, which relies on "zero-current," gate-controlled operations. Efforts have been made to control the spin-relaxation rate, the Curie temperature, or the magnetic anisotropy with a gate voltage, but these effects are usually small and volatile. We used ferroelectric tunnel junctions with ferromagnetic electrodes to demonstrate local, large, and nonvolatile control of carrier spin polarization by electrically switching ferroelectric polarization. Our results represent a giant type of interfacial magnetoelectric coupling and suggest a low-power approach for spin-based information control.

  5. Ferroelectric Fluid Flow Control Valve

    NASA Technical Reports Server (NTRS)

    Jalink, Antony, Jr. (Inventor); Hellbaum, Richard F. (Inventor); Rohrbach, Wayne W. (Inventor)

    1999-01-01

    An active valve is controlled and driven by external electrical actuation of a ferroelectric actuator to provide for improved passage of the fluid during certain time periods and to provide positive closure of the valve during other time periods. The valve provides improved passage in the direction of flow and positive closure in the direction against the flow. The actuator is a dome shaped internally prestressed ferroelectric actuator having a curvature, said dome shaped actuator having a rim and an apex. and a dome height measured from a plane through said rim said apex that varies with an electric voltage applied between an inside and an outside surface of said dome shaped actuator.

  6. Doped liquid nitrobenzene is ferroelectric.

    PubMed

    Shelton, David P; Quine, Zachary

    2007-11-28

    The high resolution hyper-Rayleigh light scattering spectrum for liquid nitrobenzene doped with triflic acid (CF(3)SO(3)H) shows a narrow spike at zero frequency shift which has the polarization signature of a polar longitudinal collective mode. This spectral spike disappears for pure nitrobenzene. The spectral spike is interpreted as due to ferroelectric domains in the liquid. The dopant molecules appear to induce ferroelectric organization of the nitrobenzene molecules which is otherwise absent in the pure liquid. Estimated domain size is 34 nm and relaxation time is 50 ns.

  7. Image plane digital holographic microscope for the inspection of ferroelectric single crystals

    NASA Astrophysics Data System (ADS)

    Psota, Pavel; Mokrý, Pavel; Lédl, Vít; Vojtíšek, Petr

    2016-12-01

    One of the most important characteristics in the research and application of ferroelectric materials is the appearance of the domain patterns, which take place in phenomena such as ferroelectric phase transitions or ferroelectric switching. The ability to visualize domains is the key factor that enables the progress in the research of these extremely interesting phenomena. However, the three-dimensional visualization of the ferroelectric domain patterns in the whole volume of the ferroelectric single crystal is not a straightforward task. We present the optical method, which allows the acquisition of quantitative and qualitative data substantial for the ferroelectric domain research. The principle of the method is based on image plane digital holographic microscopy (DHM). We used DHM setup outcomes from a Mach-Zehnder type of interferometer and phase-shifting digital holography. The studied specimen is a single crystal of barium titanate. It is demonstrated that the use of solid-state thin-film transparent electrodes of indium tin oxide greatly reduces the unwanted wavefront distortions, which are frequently produced in liquid electrodes. Using this approach, it is possible to greatly improve the DHM measurements in low applied electric fields. Thanks to the properties of the setup, real-time observation of domain walls growth or existing patterns of the ferroelectric crystal is possible.

  8. Metallic-like to nonmetallic transitions in a variety of heavily oxygen deficient ferroelectrics

    SciTech Connect

    Bock, Jonathan A.; Trolier-McKinstry, Susan; Randall, Clive A.; Lee, Soonil

    2015-08-31

    The coupling between ferroelectric distortions and electron transport is an important factor in understanding ferroelectric/noncentrosymmetric materials with metallic conductivities and ferroelectric-based thermoelectrics. Here, multiple d{sup 0} ferroelectrics with a variety of crystal structures are doped via oxygen deficiency, resulting in metallic-like conduction in the paraelectric state. It is found that most of the studied systems show a metallic-like to nonmetallic transition near the paraelectric-ferroelectric transition. The metallic-like to nonmetallic transition temperature can be shifted using mechanisms that shift the paraelectric-ferroelectric transition temperature. It was found that the metallic-like to nonmetallic transition temperature could be shifted from 373 K to 273 K by varying (Ba{sub 1−x}Sr{sub x})TiO{sub 3−δ} from x = 0 to x = 0.3 and x = 1. The most probable mechanism for ferroelectric-electron transport coupling was determined to be Anderson localization associated with polarization with short-range order.

  9. The direct magnetoelectric effect in ferroelectric-ferromagnetic epitaxial heterostructures

    NASA Astrophysics Data System (ADS)

    Fina, I.; Dix, N.; Rebled, J. M.; Gemeiner, P.; Martí, X.; Peiró, F.; Dkhil, B.; Sánchez, F.; Fàbrega, L.; Fontcuberta, J.

    2013-08-01

    Ferroelectric (FE) and ferromagnetic (FM) materials engineered in horizontal heterostructures allow interface-mediated magnetoelectric coupling. The so-called converse magnetoelectric effect (CME) has been already demonstrated by electric-field poling of the ferroelectric layers and subsequent modification of the magnetic state of adjacent ferromagnetic layers by strain effects and/or free-carrier density tuning. Here we focus on the direct magnetoelectric effect (DME) where the dielectric state of a ferroelectric thin film is modified by a magnetic field. Ferroelectric BaTiO3 (BTO) and ferromagnetic CoFe2O4 (CFO) oxide thin films have been used to create epitaxial FE/FM and FM/FE heterostructures on SrTiO3(001) substrates buffered with metallic SrRuO3. It will be shown that large ferroelectric polarization and DME can be obtained by appropriate selection of the stacking order of the FE and FM films and their relative thicknesses. The dielectric permittivity, at the structural transitions of BTO, is strongly modified (up to 36%) when measurements are performed under a magnetic field. Due to the insulating nature of the ferromagnetic layer and the concomitant absence of the electric-field effect, the observed DME effect solely results from the magnetostrictive response of CFO elastically coupled to the BTO layer. These findings show that appropriate architecture and materials selection allow overcoming substrate-induced clamping in multiferroic multi-layered films.Ferroelectric (FE) and ferromagnetic (FM) materials engineered in horizontal heterostructures allow interface-mediated magnetoelectric coupling. The so-called converse magnetoelectric effect (CME) has been already demonstrated by electric-field poling of the ferroelectric layers and subsequent modification of the magnetic state of adjacent ferromagnetic layers by strain effects and/or free-carrier density tuning. Here we focus on the direct magnetoelectric effect (DME) where the dielectric state of a

  10. Polar Superhelices in Ferroelectric Chiral Nanosprings

    PubMed Central

    Shimada, Takahiro; Lich, Le Van; Nagano, Koyo; Wang, Jian-Shan; Wang, Jie; Kitamura, Takayuki

    2016-01-01

    Topological objects of nontrivial spin or dipolar field textures, such as skyrmions, merons, and vortices, interacting with applied external fields in ferroic materials are of great scientific interest as an intriguing playground of unique physical phenomena and novel technological paradigms. The quest for new topological configurations of such swirling field textures has primarily been done for magnets with Dzyaloshinskii-Moriya interactions, while the absence of such intrinsic chiral interactions among electric dipoles left ferroelectrics aside in this quest. Here, we demonstrate that a helical polarization coiled into another helix, namely a polar superhelix, can be extrinsically stabilized in ferroelectric nanosprings. The interplay between dipolar interactions confined in the chiral geometry and the complex strain field of mixed bending and twisting induces the superhelical configuration of electric polarization. The geometrical structure of the polar superhelix gives rise to electric chiralities at two different length scales and the coexistence of three order parameters, i.e., polarization, toroidization, and hypertoroidization, both of which can be manipulated by homogeneous electric and/or mechanical fields. Our work therefore provides a new geometrical configuration of swirling dipolar fields, which offers the possibility of multiple order-parameters, and electromechanically controllable dipolar chiralities and associated electro-optical responses. PMID:27713540

  11. Functional ferroelectric tunnel junctions on silicon

    NASA Astrophysics Data System (ADS)

    Guo, Rui; Wang, Zhe; Zeng, Shengwei; Han, Kun; Huang, Lisen; Schlom, Darrell G.; Venkatesan, T.; Ariando; Chen, Jingsheng

    2015-07-01

    The quest for solid state non-volatility memory devices on silicon with high storage density, high speed, low power consumption has attracted intense research on new materials and novel device architectures. Although flash memory dominates in the non-volatile memory market currently, it has drawbacks, such as low operation speed, and limited cycle endurance, which prevents it from becoming the “universal memory”. In this report, we demonstrate ferroelectric tunnel junctions (Pt/BaTiO3/La0.67Sr0.33MnO3) epitaxially grown on silicon substrates. X-ray diffraction spectra and high resolution transmission electron microscope images prove the high epitaxial quality of the single crystal perovskite films grown on silicon. Furthermore, the write speed, data retention and fatigue properties of the device compare favorably with flash memories. The results prove that the silicon-based ferroelectric tunnel junction is a very promising candidate for application in future non-volatile memories.

  12. Ferroelectric Liquid Crystals In Aerodynamic Testing

    NASA Technical Reports Server (NTRS)

    Parmar, Devendra S.; Holmes, Harlan K.

    1994-01-01

    The process of simultaneous optical visualization and quantitative measurement of aerodynamic boundary layer parameters requires new concepts, materials and utilization methods. Measurement of shear stress in terms of the transmitted or the reflected light intensity from an aligned ferroelectric liquid crystal (FLC) thin (approx. 1 micron) film deposited on a glass substrate has been the first step in this direction. In this paper, recent progress in utilization of FLC thin films for skin friction measurement and for studying the state of the boundary layer in a wind tunnel environment is reviewed. The switching characteristics of FLCs have been used to measure pressure from the newly devised system of partially exposed polymer dispersed ferroelectric liquid crystals (PEPDFLCs). In this configuration, a PEPDFLC thin film (approx. 10-25 microns) is sandwiched between two transparent conducting electrodes, one a rigid surface and the other a flexible sheet such as polyvinylidene fluoride or mylar. The switching characteristics of the film are a function of the pressure applied to the flexible transparent electrode and a predetermined bias voltage across the two electrodes. The results, considering the dielectrics of composite media, are discussed.

  13. Improper ferroelectricity: A theoretical and experimental investigation

    NASA Astrophysics Data System (ADS)

    Hardy, J. R.; Ullman, F. G.

    1984-02-01

    A combined theoretical and experimental study has been made of the origins and properties of the improper ferroelectricity associated with structural modulations of non-zero wavelengths. Two classes of materials have been studied: rare earth molybdates (specifically, gadolinium molybdate: GMO), and potassium selenate and its isomorphs. In the former, the modulation is produced by a zone boundary phonon instability, and in the latter by the instability of a phonon of wave vector approximately two-thirds of the way to the zone-boundary. In the second case the initial result is a modulated structure whose repeat distance is not a rational multiple of the basic lattice repeat distance. This result is a modulated polarization which, when the basic modulation locks in to a rational multiple of the lattice spacing, becomes uniform, and improper ferroelectricity results. The origins of these effects have been elucidated by theoretical studies, initially semi-empirical, but subsequently from first-principles. These complemented the experimental work, which primarily used inelastic light scattering, uniaxial stress, and hydrostatic pressure, to probe the balance between the interionic forces through the effects on the phonons and dielectric properties.

  14. Prediction of a native ferroelectric metal

    PubMed Central

    Filippetti, Alessio; Fiorentini, Vincenzo; Ricci, Francesco; Delugas, Pietro; Íñiguez, Jorge

    2016-01-01

    Over 50 years ago, Anderson and Blount discussed symmetry-allowed polar distortions in metals, spawning the idea that a material might be simultaneously metallic and ferroelectric. While many studies have ever since considered such or similar situations, actual ferroelectricity—that is, the existence of a switchable intrinsic electric polarization—has not yet been attained in a metal, and is in fact generally deemed incompatible with the screening by mobile conduction charges. Here we refute this common wisdom and show, by means of first-principles simulations, that native metallicity and ferroelectricity coexist in the layered perovskite Bi5Ti5O17. We show that, despite being a metal, Bi5Ti5O17 can sustain a sizable potential drop along the polar direction, as needed to reverse its polarization by an external bias. We also reveal striking behaviours, as the self-screening mechanism at work in thin Bi5Ti5O17 layers, emerging from the interplay between polar distortions and carriers in this compound. PMID:27040076

  15. A CMOS compatible, ferroelectric tunnel junction.

    PubMed

    Ambriz Vargas, Fabian; Kolhatkar, Gitanjali; Broyer, Maxime; Hadj Youssef, Azza; Nouar, Rafik; Sarkissian, Andranik; Thomas, Reji; Gomez-Yanez, Carlos; Gauthier, Marc A; Ruediger, Andreas

    2017-04-03

    In recent years, the experimental demonstration of Ferroelectric Tunnel Junctions (FTJ) based on perovskite tunnel barriers has been reported. However, integrating these perovskite materials into conventional silicon memory technology remains challenging due to their lack of compatibility with the complementary metal oxide semiconductor process (CMOS). The present communication reports the fabrication of an FTJ based on a CMOS compatible tunnel barrier Hf0.5Zr0.5O2 (6 unit cells thick) on an equally CMOS compatible TiN electrode. Analysis of the FTJ by grazing angle incidence X-ray diffraction confirmed the formation of the non-centrosymmetric orthorhombic phase (Pbc2_1, ferroelectric phase). The FTJ characterization is followed by the reconstruction of the electrostatic potential profile in the as-grown TiN/Hf0.5Zr0.5O2/Pt heterostructure. A direct tunneling current model across a trapezoidal barrier was used to correlate the electronic and electrical properties of our FTJ devices. The good agreement between the experimental and the theoretical model attests to the tunneling electroresistance effect (TER) in our FTJ device. A TER ratio of ~15 was calculated for the present FTJ device at low read voltage (+0.2 V). This study makes Hf0.5Zr0.5O2 a promising candidate for integration into conventional Si memory technology.

  16. Mechanisms for the operation of thin film transistors on ferroelectrics

    SciTech Connect

    Seager, C.H.; McIntyre, D.; Tuttle, B.A.; Evans, J.

    1993-12-31

    The electric field emanating from the surface of a poled ferroelectric can control the conduction properties of an overlaying semiconducting film, this combination of materials can thus serve as a non-destructive readout, non-volatile memory device. Here the authors will describe a variety of experimental studies of these devices designed to probe the physics of their operation. The experimental systems included sputtered, n-type semiconductor (SC) films of In{sub 2}O{sub 3} and ZnO deposited on bulk PLZT ferroelectrics (FE) and thin PZT FE films. Two distinctly different types of device response were measured in this study; in the first, the change in SC film conductance observed in the remanent FE state is in the direction expected from the remanent polarization vector in the ferroelectric. In the second, typically seen in the thin film FE devices, the opposite behavior is observed. They find that these two general cases of behavior, including the observed variations of the SC film conductances and carrier mobilities, can be described by a general model which takes into account not only the FE displacement vector, but also charge injected from the semiconductor into the ferroelectric during biasing of the gate.

  17. Stabilizing the ferroelectric phase in doped hafnium oxide

    NASA Astrophysics Data System (ADS)

    Hoffmann, M.; Schroeder, U.; Schenk, T.; Shimizu, T.; Funakubo, H.; Sakata, O.; Pohl, D.; Drescher, M.; Adelmann, C.; Materlik, R.; Kersch, A.; Mikolajick, T.

    2015-08-01

    The ferroelectric properties and crystal structure of doped HfO2 thin films were investigated for different thicknesses, electrode materials, and annealing conditions. Metal-ferroelectric-metal capacitors containing Gd:HfO2 showed no reduction of the polarization within the studied thickness range, in contrast to hafnia films with other dopants. A qualitative model describing the influence of basic process parameters on the crystal structure of HfO2 was proposed. The influence of different structural parameters on the field cycling behavior was examined. This revealed the wake-up effect in doped HfO2 to be dominated by interface induced effects, rather than a field induced phase transition. TaN electrodes were shown to considerably enhance the stabilization of the ferroelectric phase in HfO2 compared to TiN electrodes, yielding a Pr of up to 35 μC/cm2. This effect was attributed to the interface oxidation of the electrodes during annealing, resulting in a different density of oxygen vacancies in the Gd:HfO2 films. Ab initio simulations confirmed the influence of oxygen vacancies on the phase stability of ferroelectric HfO2.

  18. Collective dynamics underpins Rayleigh behavior in disordered polycrystalline ferroelectrics

    PubMed Central

    Bintachitt, P.; Jesse, S.; Damjanovic, D.; Han, Y.; Reaney, I. M.; Trolier-McKinstry, S.; Kalinin, S. V.

    2010-01-01

    Nanoscale and mesoscopic disorder and associated local hysteretic responses underpin the unique properties of spin and cluster glasses, phase-separated oxides, polycrystalline ferroelectrics, and ferromagnets alike. Despite the rich history of the field, the relationship between the statistical descriptors of hysteresis behavior such as Preisach density, and micro and nanostructure has remained elusive. By using polycrystalline ferroelectric capacitors as a model system, we now report quantitative nonlinearity measurements in 0.025–1 μm3 volumes, approximately 106 times smaller than previously possible. We discover that the onset of nonlinear behavior with thickness proceeds through formation and increase of areal density of micron-scale regions with large nonlinear response embedded in a more weakly nonlinear matrix. This observation indicates that large-scale collective domain wall dynamics, as opposed to motion of noninteracting walls, underpins Rayleigh behavior in disordered ferroelectrics. The measurements provide evidence for the existence and extent of the domain avalanches in ferroelectric materials, forcing us to rethink 100-year old paradigms. PMID:20368462

  19. Thermal-to-electric energy conversion using ferroelectric film capacitors

    SciTech Connect

    Kozyrev, A. B.; Platonov, R. A.; Soldatenkov, O. I.

    2014-10-28

    The capacitive ferroelectric thermoelectric converter harvesting electrical energy through non-linear capacitance variation caused by changes in temperature is analyzed. The ferroelectric material used was the thin (0.5 μm) Ba{sub 0.3}Sr{sub 0.7}TiO{sub 3} film. On the basis of experimental dependencies of the ferroelectric film permittivity on temperature ranging from 100 K to 350 K under different electric fields up to 80 V/μm, the optimum values of operating temperatures and electric field for the energy harvesting optimization were determined. For the temperature oscillations of ±15 K around room temperature and electric field about 40 V/μm, the harvested energy was estimated as 30 mJ/cm{sup 3}. It is shown that the use of thin ferroelectric films for rapid capacitance variation versus temperature and microelectromechanical systems for fast temperature modulations may be a relevant solution for creation of small power scale generators for portable electronics.

  20. Quantum ferroelectricity in charge-transfer complex crystals

    PubMed Central

    Horiuchi, Sachio; Kobayashi, Kensuke; Kumai, Reiji; Minami, Nao; Kagawa, Fumitaka; Tokura, Yoshinori

    2015-01-01

    Quantum phase transition achieved by fine tuning the continuous phase transition down to zero kelvin is a challenge for solid state science. Critical phenomena distinct from the effects of thermal fluctuations can materialize when the electronic, structural or magnetic long-range order is perturbed by quantum fluctuations between degenerate ground states. Here we have developed chemically pure tetrahalo-p-benzoquinones of n iodine and 4–n bromine substituents (QBr4–nIn, n=0–4) to search for ferroelectric charge-transfer complexes with tetrathiafulvalene (TTF). Among them, TTF–QBr2I2 exhibits a ferroelectric neutral–ionic phase transition, which is continuously controlled over a wide temperature range from near-zero kelvin to room temperature under hydrostatic pressure. Quantum critical behaviour is accompanied by a much larger permittivity than those of other neutral–ionic transition compounds, such as well-known ferroelectric complex of TTF–QCl4 and quantum antiferroelectric of dimethyl–TTF–QBr4. By contrast, TTF–QBr3I complex, another member of this compound family, shows complete suppression of the ferroelectric spin-Peierls-type phase transition. PMID:26076656

  1. Domain walls and ferroelectric reversal in corundum derivatives

    NASA Astrophysics Data System (ADS)

    Ye, Meng; Vanderbilt, David

    2017-01-01

    Domain walls are the topological defects that mediate polarization reversal in ferroelectrics, and they may exhibit quite different geometric and electronic structures compared to the bulk. Therefore, a detailed atomic-scale understanding of the static and dynamic properties of domain walls is of pressing interest. In this work, we use first-principles methods to study the structures of 180∘ domain walls, both in their relaxed state and along the ferroelectric reversal pathway, in ferroelectrics belonging to the family of corundum derivatives. Our calculations predict their orientation, formation energy, and migration energy and also identify important couplings between polarization, magnetization, and chirality at the domain walls. Finally, we point out a strong empirical correlation between the height of the domain-wall-mediated polarization reversal barrier and the local bonding environment of the mobile A cations as measured by bond-valence sums. Our results thus provide both theoretical and empirical guidance for future searches for ferroelectric candidates in materials of the corundum derivative family.

  2. Mechanism for strong magnetoelectric coupling in dilute magnetic ferroelectrics

    NASA Astrophysics Data System (ADS)

    Weston, L.; Cui, X. Y.; Ringer, S. P.; Stampfl, C.

    2016-11-01

    The manipulation of atomic-scale magnetization is important from both a fundamental and a practical perspective. Using first-principles density-functional-theory calculations within the hybrid functional approach, we systematically study spin-lattice coupling effects for isolated 3 d4-3 d7 transition-metal dopants in a nonmagnetic, ferroelectric PbTiO3 host material. When present at the B-site, a low-spin (or intermediate-spin) to high-spin crossover induces marked ferroelectric-like distortions in the local geometry, characterized by a shift of the dopant ion with respect to the surrounding O6 octahedral cage. The origins of this microscopic multiferroic effect are discussed in terms of the pseudo-Jahn-Teller theory for ferroelectricity. The possibility to exploit this phenomenon to achieve strong magnetoelectric coupling, including controlled spin switching, is also investigated. These results provide a further understanding of ferroelectricity and multiferroicity in perovskite oxides, and they suggest a possible pathway to manipulate single atomic spins in semiconductor solid solutions.

  3. Stabilizing the ferroelectric phase in doped hafnium oxide

    SciTech Connect

    Hoffmann, M.; Schroeder, U.; Schenk, T.; Shimizu, T.; Funakubo, H.; Sakata, O.; Pohl, D.; Drescher, M.; Adelmann, C.; Materlik, R.; Kersch, A.; Mikolajick, T.

    2015-08-21

    The ferroelectric properties and crystal structure of doped HfO{sub 2} thin films were investigated for different thicknesses, electrode materials, and annealing conditions. Metal-ferroelectric-metal capacitors containing Gd:HfO{sub 2} showed no reduction of the polarization within the studied thickness range, in contrast to hafnia films with other dopants. A qualitative model describing the influence of basic process parameters on the crystal structure of HfO{sub 2} was proposed. The influence of different structural parameters on the field cycling behavior was examined. This revealed the wake-up effect in doped HfO{sub 2} to be dominated by interface induced effects, rather than a field induced phase transition. TaN electrodes were shown to considerably enhance the stabilization of the ferroelectric phase in HfO{sub 2} compared to TiN electrodes, yielding a P{sub r} of up to 35 μC/cm{sup 2}. This effect was attributed to the interface oxidation of the electrodes during annealing, resulting in a different density of oxygen vacancies in the Gd:HfO{sub 2} films. Ab initio simulations confirmed the influence of oxygen vacancies on the phase stability of ferroelectric HfO{sub 2}.

  4. Collective dynamics underpins Rayleigh behavior in disordered polycrystalline ferroelectrics.

    PubMed

    Bintachitt, P; Jesse, S; Damjanovic, D; Han, Y; Reaney, I M; Trolier-McKinstry, S; Kalinin, S V

    2010-04-20

    Nanoscale and mesoscopic disorder and associated local hysteretic responses underpin the unique properties of spin and cluster glasses, phase-separated oxides, polycrystalline ferroelectrics, and ferromagnets alike. Despite the rich history of the field, the relationship between the statistical descriptors of hysteresis behavior such as Preisach density, and micro and nanostructure has remained elusive. By using polycrystalline ferroelectric capacitors as a model system, we now report quantitative nonlinearity measurements in 0.025-1 microm(3) volumes, approximately 10(6) times smaller than previously possible. We discover that the onset of nonlinear behavior with thickness proceeds through formation and increase of areal density of micron-scale regions with large nonlinear response embedded in a more weakly nonlinear matrix. This observation indicates that large-scale collective domain wall dynamics, as opposed to motion of noninteracting walls, underpins Rayleigh behavior in disordered ferroelectrics. The measurements provide evidence for the existence and extent of the domain avalanches in ferroelectric materials, forcing us to rethink 100-year old paradigms.

  5. Single crystal ternary oxide ferroelectric integration with Silicon

    NASA Astrophysics Data System (ADS)

    Bakaul, Saidur; Serrao, Claudy; Youun, Long; Khan, Asif; Salahuddin, Sayeef

    2015-03-01

    Integrating single crystal, ternary oxide ferroelectric thin film with Silicon or other arbitrary substrates has been a holy grail for the researchers since the inception of microelectronics industry. The key motivation is that adding ferroelectric materials to existing electronic devices could bring into new functionality, physics and performance improvement such as non-volatility of information, negative capacitance effect and lowering sub-threshold swing of field effect transistor (FET) below 60 mV/decade in FET [Salahuddin, S, Datta, S. Nano Lett. 8, 405(2008)]. However, fabrication of single crystal ferroelectric thin film demands stringent conditions such as lattice matched single crystal substrate and high processing temperature which are incompatible with Silicon. Here we report on successful integration of PbZr0.2Ti0.8O3 in single crystal form with by using a layer transfer method. The lattice structure, surface morphology, piezoelectric coefficient d33, dielectric constant, ferroelectric domain switching and spontaneous and remnant polarization of the transferred PZT are as good as these characteristics of the best PZT films grown by pulsed laser deposition on lattice matched oxide substrates. We also demonstrate Si based, FE gate controlled FET devices.

  6. Ferroelectric Thin Films III, Symposium Held in San Francisco, California on April 13 - 16, 1993. Materials Research Society Symposium Proceedings, Volume 310

    DTIC Science & Technology

    1993-04-16

    prepare other materials such as LiTaO 3 was also examined. EXPERIMENTAL Likewise the previous process [9, 101, 0.5 M ethanol based precursor solutions for...to examine electrical properties of polycrystalline thin films prepared by the present process . The cleaned substrates were ethanol spin-dried...the ethanol based precursor showed lower refractive indices than LiNbO3 prepared from the methoxyethanol based 296 precursor. RTA processed LiNbO 3

  7. Integration of first-principles methods and crystallographic database searches for new ferroelectrics: Strategies and explorations

    NASA Astrophysics Data System (ADS)

    Bennett, Joseph W.; Rabe, Karin M.

    2012-11-01

    In this concept paper, the development of strategies for the integration of first-principles methods with crystallographic database mining for the discovery and design of novel ferroelectric materials is discussed, drawing on the results and experience derived from exploratory investigations on three different systems: (1) the double perovskite Sr(Sb1/2Mn1/2)O3 as a candidate semiconducting ferroelectric; (2) polar derivatives of schafarzikite MSb2O4; and (3) ferroelectric semiconductors with formula M2P2(S,Se)6. A variety of avenues for further research and investigation are suggested, including automated structure type classification, low-symmetry improper ferroelectrics, and high-throughput first-principles searches for additional representatives of structural families with desirable functional properties.

  8. Three-dimensional Phase-field Simulation of Domain Structures in Ferroelectric Islands

    SciTech Connect

    Zhang , J.X.; Wu, R.; Choudhury, S.; Li, Yulan; Hu, Shenyang Y.; Chen , L.Q.

    2008-03-24

    A three-dimensional phase-field model was developed for studying the domain structures and their evolution in ferroelectric islands attached onto a substrate. It simultaneously takes into account the long-range interactions such as electric and elastic interactions, substrate constraint, as well as the stress relaxation caused by the surfaces of an island. As an example, we studied the domain structures of PbZr0.2Ti0.8O3 islands. It was demonstrated that the domain structures of ferroelectric islands could be dramatically different from those of continuous thin films due to the relief of substrate constraint. The stress distribution inside islands is highly dependent on the aspect ratio, i.e., lateral dimension over island thickness, which provides us a new way for engineering the domain structures of ferroelectric materials. The effect of electrostatic energy on the domain structures of ferroelectric islands was also discussed.

  9. CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES: Study of Phase Transition Properties in Epitaxial Ferroelectric Film

    NASA Astrophysics Data System (ADS)

    Wang, Chun-Dong; Teng, Bao-Hua; Ju, Yong-Feng; Cheng, Deng-Mu; Zhang, Chun-Lai

    2010-10-01

    Based on the transverse Ising model and using decoupling approximation to the Fermi-type Green's function, we study the phase transition properties of the epitaxial ferroelectric film with one substrate. A general recursive equation of the ferroelectric thin film with two n-layer materials is obtained, which enables us to study the phase transition properties for any number layers for epitaxial ferroelectric thin film. With the help of this equation, we analyze the effect of the exchange interaction and the transverse field in the phase diagram, the influence to the polarizations and Curie temperature numerically. The results show that epitaxial ferroelectric film are able to induce a strong increase or decrease of Curie temperature to different exchange interactions and transverse fields within the epitaxial film layers. The theoretical results are in reasonable accordance with experimental data of different ferroelectric thin film.

  10. Pulse sharpening effects of thin film ferroelectric transmission lines

    NASA Astrophysics Data System (ADS)

    Sleezer, Robert J.

    Advances in material science have resulted in the development of electrically nonlinear high dielectric thin film ferroelectrics, which have led to new opportunities for the creation of novel devices. This dissertation investigated one such device: a low voltage nonlinear transmission line (NLTL). A finite element simulation of ferroelectric transmission lines showed that NLTLs are capable of creating shockwaves. Additionally, if the losses are kept sufficiently low, it was shown that voltage gain should be possible. Furthermore, a method of accounting for material dispersion was developed. Results from simulations including material dispersion showed that temporal solitons might be possible from a continuous ferroelectric based nonlinear transmission line. Fabrication of a thin film ferroelectric NLTL required the growth of a ferroelectric material on a conductive substrate. Barium titanate (BTO), which has been gaining popularity due to its high dielectric constant, strong nonlinearity, and lack of lead, was grown. Molecular beam epitaxy and sol-gel growth were both explored and sol-gel was chosen as the growth method for the final device, in part due to its ability to grow BTO thin films on highly conductive nickel substrates. Samples approximately 330 nm thick were grown by this method. Oxygen vacancies in the as grown BTO films were filled by annealing in low pressure oxygen environments. X-ray diffraction measurements were used to determine an O2 pressure for oxidation that was slightly less than the pressure at which NiO forms to ensure maximum filling of the vacancies in the BTO. Grown samples were successfully shown to have ferroelectric properties. A lumped element transmission line was fabricated using discrete capacitors and inductors with a sample as described above. Test capacitors were fabricated and used to determine the dielectric constant of the BTO thin film. This was used to select capacitor pad sizes and inductor values to create a 50 Ohm line

  11. Complex oxide ferroelectrics: Electrostatic doping by domain walls

    SciTech Connect

    Maksymovych, Petro

    2015-06-19

    Electrically conducting interfaces can form, rather unexpectedly, by breaking the translational symmetry of electrically insulating complex oxides. For example, a nanometre-thick heteroepitaxial interface between electronically insulating LaAlO3 and SrTiO3 supports a 2D electron gas1 with high mobility of >1,000 cm2 V-1 s-1 (ref. 2). Such interfaces can exhibit magnetism, superconductivity and phase transitions that may form the functional basis of future electronic devices2. A peculiar conducting interface can be created within a polar ferroelectric oxide by breaking the translational symmetry of the ferroelectric order parameter and creating a so-called ferroelectric domain wall (Fig. 1a,b). If the direction of atomic displacements changes at the wall in such a way as to create a discontinuity in the polarization component normal to the wall (Fig. 1a), the domain wall becomes electrostatically charged. It may then attract compensating mobile charges of opposite sign produced by dopant ionization, photoexcitation or other effects, thereby locally, electrostatically doping the host ferroelectric film. In contrast to conductive interfaces between epitaxially grown oxides, domain walls can be reversibly created, positioned and shaped by electric fields, enabling reconfigurable circuitry within the same volume of the material. Now, writing in Nature Nanotechnology, Arnaud Crassous and colleagues at EPFL and University of Geneva demonstrate control and stability of charged conducting domain walls in ferroelectric thin films of BiFeO3 down to the nanoscale.

  12. Ferroelectricity in Si-doped HfO2 revealed: a binary lead-free ferroelectric.

    PubMed

    Martin, Dominik; Müller, Johannes; Schenk, Tony; Arruda, Thomas M; Kumar, Amit; Strelcov, Evgheni; Yurchuk, Ekaterina; Müller, Stefan; Pohl, Darius; Schröder, Uwe; Kalinin, Sergei V; Mikolajick, Thomas

    2014-12-23

    Static domain structures and polarization dynamics of silicon doped HfO2 are explored. The evolution of ferroelectricity as a function of Si-doping level driving the transition from paraelectricity via ferroelectricity to antiferroelectricity is investigated. Ferroelectric and antiferroelectric properties can be observed locally on the pristine, poled and electroded surfaces, providing conclusive evidence to intrinsic ferroic behavior.

  13. Experimental observation of negative capacitance in ferroelectrics at room temperature.

    PubMed

    Appleby, Daniel J R; Ponon, Nikhil K; Kwa, Kelvin S K; Zou, Bin; Petrov, Peter K; Wang, Tianle; Alford, Neil M; O'Neill, Anthony

    2014-07-09

    Effective negative capacitance has been postulated in ferroelectrics because there is a hysteresis in plots of polarization-electric field. Compelling experimental evidence of effective negative capacitance is presented here at room temperature in engineered devices, where it is stabilized by the presence of a paraelectric material. In future integrated circuits, the incorporation of such negative capacitance into MOSFET gate stacks would reduce the subthreshold slope, enabling low power operation and reduced self-heating.

  14. Crack instability of ferroelectric solids under alternative electric loading

    NASA Astrophysics Data System (ADS)

    Chen, Hao-Sen; Wang, He-Ling; Pei, Yong-Mao; Wei, Yu-Jie; Liu, Bin; Fang, Dai-Ning

    2015-08-01

    The low fracture toughness of the widely used piezoelectric and ferroelectric materials in technological applications raises a big concern about their durability and safety. Up to now, the mechanisms of electric-field induced fatigue crack growth in those materials are not fully understood. Here we report experimental observations that alternative electric loading at high frequency or large amplitude gives rise to dramatic temperature rise at the crack tip of a ferroelectric solid. The temperature rise subsequently lowers the energy barrier of materials for domain switch in the vicinity of the crack tip, increases the stress intensity factor and leads to unstable crack propagation finally. In contrast, at low frequency or small amplitude, crack tip temperature increases mildly and saturates quickly, no crack growth is observed. Together with our theoretical analysis on the non-linear heat transfer at the crack tip, we constructed a safe operating area curve with respect to the frequency and amplitude of the electric field, and validated the safety map by experiments. The revealed mechanisms about how electro-thermal-mechanical coupling influences fracture can be directly used to guide the design and safety assessment of piezoelectric and ferroelectric devices.

  15. Ferroelectric, Thermal, and Magnetic Characteristics of Praseodymium Malonate Hexahydrate Crystals

    NASA Astrophysics Data System (ADS)

    Ahmad, Nazir; Ahmad, M. M.; Kotru, P. N.

    2016-04-01

    Gel-grown single crystals of [Pr2(C3H2O4)3(H2O)6] exhibit remarkably flat habit faces, the most predominant being {110}. High-resolution x-ray diffraction analysis showed that the crystals are free from structural grain boundaries, which is the key requirement for single crystals for use in the microelectronics industry to serve as low-dielectric-constant ferroelectric material. The dielectric behavior recorded on {110} planes of single crystals shows that the crystal is ferroelectric with transition temperature T c = 135°C, which differs from the Curie-Weiss temperature T 0 by 2°C (T 0 < T c). Material in pellet form is shown to exhibit slightly different dielectric behavior. Polarization versus electric field confirms the ferroelectric behavior of the material. The dielectric behavior is also supported by the results of thermal studies, viz. thermogravimetric analysis (TGA), differential thermal analysis (DTA), and differential scanning calorimetry (DSC). The magnetic susceptibility and magnetic moment are calculated to be 30.045 × 10-6 emu and 3.092 BM, respectively.

  16. Topological phase transformations and intrinsic size effects in ferroelectric nanoparticles.

    PubMed

    Mangeri, John; Espinal, Yomery; Jokisaari, Andrea; Pamir Alpay, S; Nakhmanson, Serge; Heinonen, Olle

    2017-01-26

    Composite materials comprised of ferroelectric nanoparticles in a dielectric matrix are being actively investigated for a variety of functional properties attractive for a wide range of novel electronic and energy harvesting devices. However, the dependence of these functionalities on shapes, sizes, orientation and mutual arrangement of ferroelectric particles is currently not fully understood. In this study, we utilize a time-dependent Ginzburg-Landau approach combined with coupled-physics finite-element-method based simulations to elucidate the behavior of polarization in isolated spherical PbTiO3 or BaTiO3 nanoparticles embedded in a dielectric medium, including air. The equilibrium polarization topology is strongly affected by particle diameter, as well as the choice of inclusion and matrix materials, with monodomain, vortex-like and multidomain patterns emerging for various combinations of size and materials parameters. This leads to radically different polarization vs. electric field responses, resulting in highly tunable size-dependent dielectric properties that should be possible to observe experimentally. Our calculations show that there is a critical particle size below which ferroelectricity vanishes. For the PbTiO3 particle, this size is 2 and 3.4 nm, respectively, for high- and low-permittivity media. For the BaTiO3 particle, it is ∼3.6 nm regardless of the medium dielectric strength.

  17. Nanodynamics of ferroelectric ultrathin films.

    PubMed

    Zhang, Qingteng; Herchig, R; Ponomareva, I

    2011-10-21

    The nanodynamics of ferroelectric ultrathin films made of PbTi(0.6)Zr(0.4)TiO(3) alloy is explored via the use of a first-principles-based technique. Our atomistic simulations predict that the nanostripe domains which constitute the ground state of ferroelectric ultrathin films under most electric boundary conditions oscillate under a driving ac field. Furthermore, we find that the atomically thin wall, or nanowall, that separates the nanodomains with different polarization directions behaves as an elastic object and has a mass associated with it. The nanowall mass is size-dependent and gives rise to a unique size-driven transition from resonance to relaxational dynamics in ultrathin films. A general theory of nanodynamics in such films is developed and used to explain all computational findings. In addition, we find an unusual dynamical coupling between nanodomains and mechanical deformations that could potentially be used in ultrasensitive electromechanical nanosensors.

  18. Ferroelectric Stirling-Cycle Refrigerator

    NASA Technical Reports Server (NTRS)

    Jalink, Antony, Jr. (Inventor); Hellbaum, Richard F. (Inventor); Rohrbach, Wayne W. (Inventor)

    1999-01-01

    A Stirling-cycle refrigerator has a three-pump configuration and pumping sequence, in which one pump serves as a compressor. one pump serves as an expander, and one pump serves as a displacer. The pumps are ferroelectrically actuated diaphragm pumps which are coordinated by synchronizing the ferroelectric-actuator voltages in such a way that the net effect of the displacer is to reduce the deleterious effect of dead space; that is, to circulate a greater fraction of the working fluid through the heat exchangers than would be possible by use of the compressor and expander alone. In addition. the displacer can be controlled separately to make the flow of working fluid in the heat exchangers turbulent (to increase the rate of transfer of heat at the cost of greater resistance to flow) or laminar (to decrease the resistance to flow at the cost of a lower heat-transfer rate).

  19. Domain Processes in Ferroelectric Ceramics

    DTIC Science & Technology

    1994-04-14

    WALLS Electron holography utilizing the wave characteristics of electrons. Through a sharp emission tip, the emitted electron beam is largely coherent, or...mirostructural modulation at 25% doping. The strongly first order ferroelectric phase transition in PbTiO3 is also gradually changed to a nearly second...a new domain configuraton. 13 The end-member of the PZT solid solution, PbTiO3 , has the highest transition temperature (Tc = 490 °C) and the largest

  20. Relationship between ferroelectric properties and local structure of Pb1-xBaxZr0.40Ti0.60O3 ceramic materials studied by X-ray absorption and Raman spectroscopies

    NASA Astrophysics Data System (ADS)

    Mesquita, Alexandre; Michalowicz, Alain; Moscovici, Jacques; Pizani, Paulo Sergio; Mastelaro, Valmor Roberto

    2016-08-01

    This paper reports on the structural characterization of Pb1-xBaxZr0.40Ti0.60O3 (PBZT) ferroelectric ceramic compositions prepared by the conventional solid state reaction method. X-ray absorption spectroscopy (XAS) and Raman spectroscopy were used in the probing of the local structure of PBZT samples that exhibit a normal or relaxor ferroelectric behavior. They showed a considerable local disorder around Zr and Pb atoms in the samples of tetragonal or cubic long-range order symmetry. The intensity of the E(TO3) mode in the Raman spectra of PBZT relaxor samples remains constant at temperatures lower than Tm, which has proven the stabilization of the correlation process between nanodomains.

  1. Performance Measurement of a Multi-Level/Analog Ferroelectric Memory Device Design

    NASA Technical Reports Server (NTRS)

    MacLeod, Todd C.; Phillips, Thomas A.; Ho, Fat D.

    2007-01-01

    Increasing the memory density and utilizing the unique characteristics of ferroelectric devices is important in making ferroelectric memory devices more desirable to the consumer. This paper describes the characterization of a design that allows multiple levels to be stored in a ferroelectric based memory cell. It can be used to store multiple bits or analog values in a high speed nonvolatile memory. The design utilizes the hysteresis characteristic of ferroelectric transistors to store an analog value in the memory cell. The design also compensates for the decay of the polarization of the ferroelectric material over time. This is done by utilizing a pair of ferroelectric transistors to store the data. One transistor is used a reference to determinethe amount of decay that has occurred since the pair was programmed. The second transistor stores the analog value as a polarization value between zero and saturated. The design allows digital data to be stored as multiple bits in each memory cell. The number of bits per cell that can be stored will vary with the decay rate of the ferroelectric transistors and the repeatability of polarization between transistors. This paper presents measurements of an actual prototype memory cell. This prototype is not a complete implementation of a device, but instead, a prototype of the storage and retrieval portion of an actual device. The performance of this prototype is presented with the projected performance of the overall device. This memory design will be useful because it allows higher memory density, compensates for the environmental and ferroelectric aging processes, allows analog values to be directly stored in memory, compensates for the thermal and radiation environments associated with space operations, and relies only on existing technologies.

  2. Impact of symmetry on the ferroelectric properties of CaTiO3 thin films

    NASA Astrophysics Data System (ADS)

    Biegalski, Michael D.; Qiao, Liang; Gu, Yijia; Mehta, Apurva; He, Qian; Takamura, Yayoi; Borisevich, Albina; Chen, Long-Qing

    2015-04-01

    Epitaxial strain is a powerful tool to induce functional properties such as ferroelectricity in thin films of materials that do not possess ferroelectricity in bulk form. In this work, a ferroelectric state was stabilized in thin films of the incipient ferroelectric, CaTiO3, through the careful control of the biaxial strain state and TiO6 octahedral rotations. Detailed structural characterization was carried out by synchrotron x-ray diffraction and scanning transmission electron microscopy. CaTiO3 films grown on La0.18Sr0.82Al0.59Ta0.41O3 (LSAT) and NdGaO3 (NGO) substrates experienced a 1.1% biaxial strain state but differed in their octahedral tilt structures. A suppression of the out-of-plane rotations of the TiO6 octahedral in films grown on LSAT substrates resulted in a robust ferroelectric I4 mm phase with remnant polarization ˜5 μC/cm2 at 10 K and Tc near 140 K. In contrast, films grown on NGO substrates with significant octahedral tilting showed reduced polarization and Tc. These results highlight the key role played by symmetry in controlling the ferroelectric properties of perovskite oxide thin films.

  3. Self-consistent theory of nanodomain formation on non-polar surfaces of ferroelectrics

    DOE PAGES

    Morozovska, Anna N.; Obukhovskii, Vyacheslav; Fomichov, Evhen; ...

    2016-04-28

    We propose a self-consistent theoretical approach capable of describing the features of the anisotropic nanodomain formation induced by a strongly inhomogeneous electric field of a charged scanning probe microscopy tip on nonpolar cuts of ferroelectrics. We obtained that a threshold field, previously regarded as an isotropic parameter, is an anisotropic function that is specified from the polar properties and lattice pinning anisotropy of a given ferroelectric in a self-consistent way. The proposed method for the calculation of the anisotropic threshold field is not material specific, thus the field should be anisotropic in all ferroelectrics with the spontaneous polarization anisotropy alongmore » the main crystallographic directions. The most evident examples are uniaxial ferroelectrics, layered ferroelectric perovskites, and low-symmetry incommensurate ferroelectrics. Obtained results quantitatively describe the differences at several times in the nanodomain length experimentally observed on X and Y cuts of LiNbO3 and can give insight into the anisotropic dynamics of nanoscale polarization reversal in strongly inhomogeneous electric fields.« less

  4. Self-consistent theory of nanodomain formation on non-polar surfaces of ferroelectrics

    SciTech Connect

    Morozovska, Anna N.; Obukhovskii, Vyacheslav; Fomichov, Evhen; Varenyk, O. V.; Shur, Vladimir Ya.; Kalinin, Sergei V.; Eliseev, E. A.

    2016-04-28

    We propose a self-consistent theoretical approach capable of describing the features of the anisotropic nanodomain formation induced by a strongly inhomogeneous electric field of a charged scanning probe microscopy tip on nonpolar cuts of ferroelectrics. We obtained that a threshold field, previously regarded as an isotropic parameter, is an anisotropic function that is specified from the polar properties and lattice pinning anisotropy of a given ferroelectric in a self-consistent way. The proposed method for the calculation of the anisotropic threshold field is not material specific, thus the field should be anisotropic in all ferroelectrics with the spontaneous polarization anisotropy along the main crystallographic directions. The most evident examples are uniaxial ferroelectrics, layered ferroelectric perovskites, and low-symmetry incommensurate ferroelectrics. Obtained results quantitatively describe the differences at several times in the nanodomain length experimentally observed on X and Y cuts of LiNbO3 and can give insight into the anisotropic dynamics of nanoscale polarization reversal in strongly inhomogeneous electric fields.

  5. Study of the microscopic ferroelectric properties of copolymer P(VDF-TrFe) films

    NASA Astrophysics Data System (ADS)

    Baur, Li-Jie C.; Koslowski, B.; Dransfeld, K.

    1995-02-01

    By using a scanning tunneling microscope (STM) we investigated the local ferroelectric behaviour of copolymer P(VDF-TrFE) films of various compositions and crystallinity. By means of the STM we examined locally the variation of the film thickness as a function of the poling voltage (a newly developed microscopic adaptation of the so-called “butterfly” technique), achieving an accuracy of better than 1 Å in height and a lateral resolution in the nanometer range. We could clearly distinguish the different ferroelectric switching behaviour of the amorphous and crystalline domains. In addition, we were able to detect the switching of individual crystallites, the analogue to the Barkhausen-effect in ferromagnetic materials, which has not been seen so far in ferroelectric systems. Finally, our observation of a spread-out but strong ferroelectric switching also in the amorphous regions of sample is not compatible with the current theoretical structural model of a strictly non-ferroelectric amorphous phase enclosing the ferroelectric crystallites.

  6. Kinetics of Ferroelectric Phase Transition: Nonlinear Pyroelectric Effect and Ferroelectric Solar Cell

    NASA Astrophysics Data System (ADS)

    Itskovsky, M.

    1999-08-01

    Kinetics of a ferroelectric phase transition in thin ferroelectric layer (film), coated with metallic films [metal-ferroelectric-metal (MFM) system] and overheated with various heating rates through phase transition temperature by solar or laser irradiation impulse, is investigated. Dynamical nonlinear pyroelectric effect (pyroelectric current and polarization) as well as anomalies of dielectric permittivity and specific heat are calculated as functions of changing in time temperature for various heating rates. Conversion efficiency during heating of the MFM system (served as ferroelectric solar cell), operating due to the nonlinear pyroelectric effect in the ferroelectric phase transition region, ranges from a few percent for ferroelectrics of the triglycine sulphate (TGS) type to above 10% for the NaNO2 type ferroelectrics, reaching the order of efficiency of photovoltaic solar cell.

  7. Room temperature ferroelectricity in one-dimensional single chain molecular magnets [{M(Δ)M(Λ)}(ox)2(phen)2]n (M = Fe and Mn)

    NASA Astrophysics Data System (ADS)

    Bhatt, Pramod; Mukadam, M. D.; Meena, S. S.; Mishra, S. K.; Mittal, R.; Sastry, P. U.; Mandal, B. P.; Yusuf, S. M.

    2017-03-01

    The ferroelectric materials are mainly focused on pure inorganic oxides; however, the organic molecule based materials have recently attracted great attention because of their multifunctional properties. The mixing of oxalate and phenanthroline ligands with metal ions (Fe or Mn) at room temperature followed by hydrothermal treatment results in the formation of one-dimensional single chain molecular magnets which exhibit room temperature dielectric and ferroelectric behavior. The compounds are chiral in nature, and exhibit a ferroelectric behavior, attributed to the polar point group C2, in which they crystallized. The compounds are also associated with a dielectric loss and thus a relaxation process. The observed electric dipole moment, essential for a ferroelectricity, has been understood quantitatively in terms of lattice distortions at two different lattice sites within the crystal structure. The studied single chain molecular magnetic materials with room temperature ferroelectric and dielectric properties could be of great technological importance in non-volatile memory elements, and high-performance insulators.

  8. Characterization of an Autonomous Non-Volatile Ferroelectric Memory Latch

    NASA Technical Reports Server (NTRS)

    John, Caroline S.; MacLeod, Todd C.; Evans, Joe; Ho, Fat D.

    2011-01-01

    We present the electrical characterization of an autonomous non-volatile ferroelectric memory latch using the principle that when an electric field is applied to a ferroelectriccapacitor,the positive and negative remnant polarization charge states of the capacitor are denoted as either data 0 or data 1. The properties of the ferroelectric material to store an electric polarization in the absence of an electric field make the device non-volatile. Further the memory latch is autonomous as it operates with the ground, power and output node connections, without any externally clocked control line. The unique quality of this latch circuit is that it can be written when powered off. The advantages of this latch over flash memories are: a) It offers unlimited reads/writes b) works on symmetrical read/write cycles. c) The latch is asynchronous. The circuit was initially developed by Radiant Technologies Inc., Albuquerque, New Mexico.

  9. Modeling of Metal-Ferroelectric-Semiconductor Field Effect Transistors

    NASA Technical Reports Server (NTRS)

    Duen Ho, Fat; Macleod, Todd C.

    1998-01-01

    The characteristics for a MFSFET (metal-ferroelectric-semiconductor field effect transistor) is very different than a conventional MOSFET and must be modeled differently. The drain current has a hysteresis shape with respect to the gate voltage. The position along the hysteresis curve is dependent on the last positive or negative polling of the ferroelectric material. The drain current also has a logarithmic decay after the last polling. A model has been developed to describe the MFSFET drain current for both gate voltage on and gate voltage off conditions. This model takes into account the hysteresis nature of the MFSFET and the time dependent decay. The model is based on the shape of the Fermi-Dirac function which has been modified to describe the MFSFET's drain current. This is different from the model proposed by Chen et. al. and that by Wu.

  10. A finite element model of ferroelectric/ferroelastic polycrystals

    SciTech Connect

    HWANG,STEPHEN C.; MCMEEKING,ROBERT M.

    2000-02-17

    A finite element model of polarization switching in a polycrystalline ferroelectric/ferroelastic ceramic is developed. It is assumed that a crystallite switches if the reduction in potential energy of the polycrystal exceeds a critical energy barrier per unit volume of switching material. Each crystallite is represented by a finite element with the possible dipole directions assigned randomly subject to crystallographic constraints. The model accounts for both electric field induced (i.e. ferroelectric) switching and stress induced (i.e. ferroelastic) switching with piezoelectric interactions. Experimentally measured elastic, dielectric, and piezoelectric constants are used consistently, but different effective critical energy barriers are selected phenomenologically. Electric displacement versus electric field, strain versus electric field, stress versus strain, and stress versus electric displacement loops of a ceramic lead lanthanum zirconate titanate (PLZT) are modeled well below the Curie temperature.

  11. Polarization-driven catalysis via ferroelectric oxide surfaces.

    PubMed

    Kakekhani, Arvin; Ismail-Beigi, Sohrab

    2016-07-20

    The surface chemistry and physics of oxide ferroelectric surfaces with a fixed polarization state have been studied experimentally for some time. Here, we discuss the possibility of using these materials in a different mode, namely under cyclically changing polarization conditions achievable via periodic perturbations by external fields (e.g., temperature, strain or electric field). We use Density Functional Theory (DFT) and electronic structure analysis to understand the polarization-dependent surface physics and chemistry of ferroelectric oxide PbTiO3 as an example of this class of materials. This knowledge is then applied to design catalytic cycles for industrially important reactions including NOx direct decomposition and SO2 oxidation into SO3. The possibility of catalyzing direct partial oxidation of methane to methanol is also investigated. More generally, we discuss how using ferroelectrics under cyclically changing polarization conditions can help overcome some of the fundamental challenges facing the catalysis community such as the limitations imposed by the Sabatier principle and scaling relations.

  12. Quantum breathers in lithium tantalate ferroelectrics

    NASA Astrophysics Data System (ADS)

    Biswas, Arindam; Adhikar, Sutapa; Choudhary, Kamal; Basu, Reshmi; Bandyopadhyay, A. K.; Bhattacharjee, A. K.; Mandal, D.

    2013-08-01

    Lithium tantalate is technologically one of the most important ferroelectric materials with a low poling field that has several applications in the field of photonics and memory switching devices. In a Hamiltonian system, such as dipolar system, the polarization behavior of such ferroelectrics can be well-modeled by Klein-Gordon (K-G) equation. Due to strong localization coupled with discreteness in a nonlinear K-G lattice, there is a formation of breathers and multi-breathers that manifest in the localization peaks across the domains in polarization-space-time plot. Due to the presence of nonlinearity and also impurities (as antisite tantalum defects) in the structure, dissipative effects are observed and hence dissipative breathers are studied here. To probe the quantum states related to discrete breathers, the same K-G lattice is quantized to give rise to quantum breathers (QBs) that are explained by a periodic boundary condition. The gap between the localized and delocalized phonon-band is a function of impurity content that is again related to the effect of pinning of domains due to antisite tantalum defects in the system, i.e., a point of easier switching within the limited amount of data on poling field, which is related to Landau coefficient (read, nonlinearity). Secondly, in a non-periodic boundary condition, the temporal evolution of quanta shows interesting behavior in terms of `critical' time of redistribution of quanta that is proportional to QB's lifetime in femtosecond having a possibility for THz applications. Hence, the importance of both the methods for characterizing quantum breathers is shown in these perspectives.

  13. Predictive modelling of ferroelectric tunnel junctions

    NASA Astrophysics Data System (ADS)

    Velev, Julian P.; Burton, John D.; Zhuravlev, Mikhail Ye; Tsymbal, Evgeny Y.

    2016-05-01

    Ferroelectric tunnel junctions combine the phenomena of quantum-mechanical tunnelling and switchable spontaneous polarisation of a nanometre-thick ferroelectric film into novel device functionality. Switching the ferroelectric barrier polarisation direction produces a sizable change in resistance of the junction—a phenomenon known as the tunnelling electroresistance effect. From a fundamental perspective, ferroelectric tunnel junctions and their version with ferromagnetic electrodes, i.e., multiferroic tunnel junctions, are testbeds for studying the underlying mechanisms of tunnelling electroresistance as well as the interplay between electric and magnetic degrees of freedom and their effect on transport. From a practical perspective, ferroelectric tunnel junctions hold promise for disruptive device applications. In a very short time, they have traversed the path from basic model predictions to prototypes for novel non-volatile ferroelectric random access memories with non-destructive readout. This remarkable progress is to a large extent driven by a productive cycle of predictive modelling and innovative experimental effort. In this review article, we outline the development of the ferroelectric tunnel junction concept and the role of theoretical modelling in guiding experimental work. We discuss a wide range of physical phenomena that control the functional properties of ferroelectric tunnel junctions and summarise the state-of-the-art achievements in the field.

  14. Evaluation of Ferroelectric Materials for Memory Applications

    DTIC Science & Technology

    1990-06-01

    for EPROMs and EEPROMs, and further development could bring their cost -per-bit down and performance up until they are direct competition for DRAMs [Ref...total dose of 5x10 6 rad(Si), and 6xl0 6/cm 2 heavy ion fission fragments from a californium -252 fission process with approximately 200 MeV of energy...compatible with the existing semiconductor processes and provide reliability, reproducibility, and low cost if it is to be effective in manufacturing

  15. Flexoelectric piezoelectric metamaterials based on the bending of ferroelectric ceramic wafers

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaotong; Liu, Jiliang; Chu, Mingjin; Chu, Baojin

    2016-08-01

    Conventional piezoelectric ceramics lose their piezoelectric properties near the Curie temperature (Tc), which limits their application at high temperatures. One approach to resolving this issue is to design flexoelectric piezoelectric composites or piezoelectric metamaterials by exploiting the flexoelectric effect of the ferroelectric materials. In this work, an experimental study on two designs of flexoelectric metamaterials is demonstrated. When a ferroelectric ceramic wafer is placed on a metal ring or has a domed shape, which is produced through the diffusion between two pieces of ferroelectric ceramic of different compositions at high temperatures, an apparent piezoelectric response originating from the flexoelectric effect can be measured under a stress. The apparent piezoelectric response of the materials based on the designs can be sustained well above Tc. This study provides an approach to designing materials for high-temperature electromechanical applications.

  16. Charge ordering and ferroelectricity in magnetite

    NASA Astrophysics Data System (ADS)

    Khomskii, Daniel

    2007-03-01

    Magnetite Fe3O4 is one of the most fascinating material in solid state physics. Besides being the first magnetic material known to the mankind, it is also the first example of an insulator-metal transition in transition metal oxides -- the famous Verwey transition [1]. One usually connects this transition with the charge ordering of Fe^2+ and Fe^3+. However the detailed pattern of CO in Fe3O4 is still a matter of debate. Another aspect, which is not so widely known and which did not yet receive sufficient attention, is that below TV, besides being completely spin polarised, magnetite apparently is also ferroelectric (FE) [2]. Thus it seems that magnetite, besides being the first magnetic material and the first transition metal oxide with an insulator-metal transition, is also the first multiferroic material. Using the idea of a coexistence of site-centred and bond-centred charge ordering [3], I suggest a novel type of ordering in magnetite which explains the observed FE in Fe3O4 and which agrees with the structural data. [1] Verwey E.J.W., Nature 144, 327 (1939) [2] Rado G.T. and Ferrari J.M., Phys.Rev.B 12, 5166 (1975); Kato K. and Iida S., J.Phys.Soc.Japan 50, 2844 (1981) [3] Efremov D.V., van den Brink J. and Khomskii D.I., Nature Mater. 3, 853 (2004)

  17. Systematic prediction of new ferroelectrics in space group P3.

    PubMed

    Abrahams, S C

    2000-10-01

    The current release of the Inorganic Crystal Structure Database contains a total of 57 entries under space group P3 that correspond to 50 different materials. There are 21 structures reported with this space group that satisfy the criteria for ferroelectricity, at a confidence level that depends on the reliability of the underlying structural determination. One ferroelectric discovered earlier is also listed. In addition, the database contains 19 entries that probably should be assigned to a centrosymmetric space group, seven that are polar but probably not ferroelectric and two that are without atomic coordinates. Seven entries are either duplicates or present additional structural studies of the same material. Structures in space group P3 identified as potentially new ferroelectrics include LiAsCu(0.93), Na(2)UF(6), BiTeI, BaGe(4)O(9), alpha-UMo(2)O(8), Cu(2)SiS(3), Co(IO(3))(2), Sr(7)Al(12)O(25), KSn(2)F(5), YbIn(2)S(4), Na(5)CrF(2)(PO(4))(2), Sn(ClO(2))(2)(ClO(4))(6), Eu(3)BWO(9), Li(H(2)O)(4)B(OH)(4).2H(2)O, Mn(3)V(1/2)(SiO(4))O(OH)(2), Ca(6)(Si(2)O(7))(OH)(6), Na(6. 9(2))[Al(5.6(1))Si(6.4(1))O(24)](S(2)O(3))(1.0(1)).2H(2)O, BaCa(2)In(6)O(12), Ni(H(2)O)(6)[Sb(OH)(6)](2), Sr(4)Cr(3)O(9) and Cu(5)O(2)(VO(4))(2).CuCl(2).

  18. Stress and orientation effects in ferroelectric thin films

    NASA Astrophysics Data System (ADS)

    Lian, Lei

    ferroelectrics under a general state of stress and electric field. Material parameters obtained by fitting simulation results with available experimental data are used to predict effects of the preferred crystallographic orientation and biaxial tensile stress applied transverse to the poling direction. The simulation results are consistent with experimental observations of the preferred orientation and stress effects in PZT (52/48) thin films.

  19. Colossal Room-Temperature Electrocaloric Effect in Ferroelectric Polymer Nanocomposites Using Nanostructured Barium Strontium Titanates.

    PubMed

    Zhang, Guangzu; Zhang, Xiaoshan; Yang, Tiannan; Li, Qi; Chen, Long-Qing; Jiang, Shenglin; Wang, Qing

    2015-07-28

    The electrocaloric effect (ECE) refers to conversion of thermal to electrical energy of polarizable materials and could form the basis for the next-generation refrigeration and power technologies that are highly efficient and environmentally friendly. Ferroelectric materials such as ceramic and polymer films exhibit large ECEs, but each of these monolithic materials has its own limitations for practical cooling applications. In this work, nanosized barium strontium titanates with systematically varied morphologies have been prepared to form polymer nanocomposites with the ferroelectric polymer matrix. The solution-processed polymer nanocomposites exhibit an extraordinary room-temperature ECE via the synergistic combination of the high breakdown strength of a ferroelectric polymer matrix and the large change of polarization with temperature of ceramic nanofillers. It is found that a sizable ECE can be generated under both modest and high electric fields, and further enhanced greatly by tailoring the morphology of the ferroelectric nanofillers such as increasing the aspect ratio of the nanoinclusions. The effect of the geometry of the nanofillers on the dielectric permittivity, polarization, breakdown strength, ECE and crystallinity of the ferroelectric polymer has been systematically investigated. Simulations based on the phase-field model have been carried out to substantiate the experimental results. With the remarkable cooling energy density and refrigerant capacity, the polymer nanocomposites are promising for solid-state cooling applications.

  20. Switchable S = 1/2 and J = 1/2 Rashba bands in ferroelectric halide perovskites

    PubMed Central

    Kim, Minsung; Im, Jino; Freeman, Arthur J.; Ihm, Jisoon; Jin, Hosub

    2014-01-01

    The Rashba effect is spin degeneracy lift originated from spin–orbit coupling under inversion symmetry breaking and has been intensively studied for spintronics applications. However, easily implementable methods and corresponding materials for directional controls of Rashba splitting are still lacking. Here, we propose organic–inorganic hybrid metal halide perovskites as 3D Rashba systems driven by bulk ferroelectricity. In these materials, it is shown that the helical direction of the angular momentum texture in the Rashba band can be controlled by external electric fields via ferroelectric switching. Our tight-binding analysis and first-principles calculations indicate that and Rashba bands directly coupled to ferroelectric polarization emerge at the valence and conduction band edges, respectively. The coexistence of two contrasting Rashba bands having different compositions of the spin and orbital angular momentum is a distinctive feature of these materials. With recent experimental evidence for the ferroelectric response, the halide perovskites will be, to our knowledge, the first practical realization of the ferroelectric-coupled Rashba effect, suggesting novel applications to spintronic devices. PMID:24785294

  1. First-principles effective Hamiltonian simulation of ABO3-type perovskite ferroelectrics for energy storage application

    NASA Astrophysics Data System (ADS)

    Luo, Bingcheng; Wang, Xiaohui; Tian, Enke; Wu, Longwen; Li, Longtu

    2016-08-01

    Dielectric materials with high power density and energy density are eagerly desired for the potential application in advanced pulsed capacitors. Here, we present the first-principles effective Hamiltonian simulation of perovskite ferroelectrics BaTiO3, PbTiO3, and KNbO3 in order to better predict and design materials for energy storage application. The lattice constant, dielectric constant and ferroelectric hysteresis, and energy-storage density of BaTiO3, PbTiO3, and KNbO3 were calculated with the consideration of the effects of temperature and external electric field.

  2. High photovoltages in ferroelectric ceramics

    NASA Technical Reports Server (NTRS)

    Brody, P. S.

    1976-01-01

    The short-circuit currents and photo-emfs were measured for various ceramics including barium titanate, lead metaniobate, and lead titanate. It is suggested that the emfs and currents arise from the presence of photoconductor-insulator sandwiches in the presence of space-charge-produced internal fields. Results are in agreement with the proposed theory and indicate that the ferroelectric ceramics are not only producers of high-voltage photoelectricity but a photo-battery, the polarity and magnitude of which can be switched by application of an electrical signal.

  3. Structural and electronic properties of Diisopropylammonium bromide molecular ferroelectric crystal

    NASA Astrophysics Data System (ADS)

    Alsaad, A.; Qattan, I. A.; Ahmad, A. A.; Al-Aqtash, N.; Sabirianov, R. F.

    2015-10-01

    We report the results of ab-initio calculations based on Generalized Gradient Approximation (GGA) and hybrid functional (HSE06) of electronic band structure, density of states and partial density of states to get a deep insight into structural and electronic properties of P21 ferroelectric phase of Diisopropylammonium Bromide molecular crystal (DIPAB). We found that the optical band gap of the polar phase of DIPAB is ∼ 5 eV confirming it as a good dielectric. Examination of the density of states and partial density of states reveal that the valence band maximum is mainly composed of bromine 4p orbitals and the conduction band minimum is dominated by carbon 2p, carbon 2s, and nitrogen 2s orbitals. A unique aspect of P21 ferroelectric phase is the permanent dipole within the material. We found that P21 DIPAB has a spontaneous polarization of 22.64 consistent with recent findings which make it good candidate for the creation of ferroelectric tunneling junctions (FTJs) which have the potential to be used as memory devices.

  4. Photovoltaic properties of low band gap ferroelectric perovskite oxides

    NASA Astrophysics Data System (ADS)

    Huang, Xin; Paudel, Tula; Dong, Shuai; Tsymbal, Evgeny

    2015-03-01

    Low band gap ferroelectric perovskite oxides are promising for photovoltaic applications due to their high absorption in the visible optical spectrum and a possibility of having large open circuit voltage. Additionally, an intrinsic electric field present in these materials provides a bias for electron-hole separation without requiring p-n junctions as in conventional solar cells. High quality thin films of these compounds can be grown with atomic layer precision allowing control over surface and defect properties. Initial screening based on the electronic band gap and the energy dependent absorption coefficient calculated within density functional theory shows that hexagonal rare-earth manganites and ferrites are promising as photovoltaic absorbers. As a model, we consider hexagonal TbMnO3. This compound has almost ideal band gap of about 1.4 eV, very high ferroelectric Curie temperature, and can be grown epitaxially. Additionally hexagonal TbMnO3 offers possibility of coherent structure with transparent conductor ZnO. We find that the absorption is sufficiently high and dominated by interband transitions between the Mn d-bands. We will present the theoretically calculated photovoltaic efficiency of hexagonal TbMnO3 and explore other ferroelectric perovskite oxides.

  5. Microstructure tuning and magnetism switching of ferroelectric barium titanate

    SciTech Connect

    Zhou, Wenliang; Deng, Hongmei; Ding, Nuofan; Yu, Lu; Yue, Fangyu; Yang, Pingxiong; Chu, Junhao

    2015-09-15

    Single-crystal and polycrystal BaTiO{sub 3} (BTO) materials synthesized by the physical and chemical methods, respectively, have been studied based on microstructural characterizations and magnetic measurements. The results of X-ray diffraction and Raman scatting spectra show that a single crystal tetragonal to polycrystalline pseudo-cubic structure transformation occurs in BTO ferroelectrics, dependent of growth conditions and interface effects. High-resolution transmission electron microscope data indicate that the as-prepared BTO/SrTiO{sub 3} (001) and BTO/SrRuO{sub 3}/SrTiO{sub 3} (001) heterostructures are highly c-axis oriented with atomic sharp interfaces. Lattice defects (i.e., edge-type misfit dislocations and stacking faults) in the heterostructures could be identified clearly and showed tunable with the variations of interface strain. Furthermore, the effects of vacancy defects on magnetic properties of BTO are discussed, which shows a diamagnetism–ferromagnetism switching as intrinsic vacancies increase. This work opens up a possible avenue to prepare magnetic BTO ferroelectrics. - Highlights: • Structure of BTO is tunable, depending on growth conditions and interface strain. • STEM–EDX data indicate the presence of lattice defects in BTO ferroelectrics. • BTO magnetism could be controlled by defects showing dia-ferromagnetism switching. • BTO with more vacancies shows RTFM, as evidence of vacancy magnetism effects.

  6. Magnetic switching of ferroelectric domains at room temperature in multiferroic PZTFT

    PubMed Central

    Evans, D.M.; Schilling, A.; Kumar, Ashok; Sanchez, D.; Ortega, N.; Arredondo, M.; Katiyar, R.S.; Gregg, J.M.; Scott, J.F.

    2013-01-01

    Single-phase magnetoelectric multiferroics are ferroelectric materials that display some form of magnetism. In addition, magnetic and ferroelectric order parameters are not independent of one another. Thus, the application of either an electric or magnetic field simultaneously alters both the electrical dipole configuration and the magnetic state of the material. The technological possibilities that could arise from magnetoelectric multiferroics are considerable and a range of functional devices has already been envisioned. Realising these devices, however, requires coupling effects to be significant and to occur at room temperature. Although such characteristics can be created in piezoelectric-magnetostrictive composites, to date they have only been weakly evident in single-phase multiferroics. Here in a newly discovered room temperature multiferroic, we demonstrate significant room temperature coupling by monitoring changes in ferroelectric domain patterns induced by magnetic fields. An order of magnitude estimate of the effective coupling coefficient suggests a value of ~1 × 10−7 sm−1. PMID:23443562

  7. Nanoscale Electromechanics of Ferroelectric and Biological Systems: A New Dimension in Scanning Probe Microscopy

    NASA Astrophysics Data System (ADS)

    Kalinin, Sergei V.; Rodriguez, Brian J.; Jesse, Stephen; Karapetian, Edgar; Mirman, Boris; Eliseev, Eugene A.; Morozovska, Anna N.

    2007-08-01

    Functionality of biological and inorganic systems ranging from nonvolatile computer memories and microelectromechanical systems to electromotor proteins and cellular membranes is ultimately based on the intricate coupling between electrical and mechanical phenomena. In the past decade, piezoresponse force microscopy (PFM) has been established as a powerful tool for nanoscale imaging, spectroscopy, and manipulation of ferroelectric and piezoelectric materials. Here, we give an overview of the fundamental image formation mechanism in PFM and summarize recent theoretical and technological advances. In particular, we show that the signal formation in PFM is complementary to that in the scanning tunneling microscopy (STM) and atomic force microscopy (AFM) techniques, and we discuss the implications. We also consider the prospect of extending PFM beyond ferroelectric characterization for quantitative probing of electromechanical behavior in molecular and biological systems and high-resolution probing of static and dynamic polarization switching processes in low-dimensional ferroelectric materials and heterostructures.

  8. Nanoscale Electromechanics of Ferroelectric and Biological Systems: A New Dimension in Scanning Probe Microscopy

    SciTech Connect

    Kalinin, Sergei V; Rodriguez, Brian J; Jesse, Stephen; Karapetian, Edgar; Mirman, B; Eliseev, E. A.; Morozovska, A. N.

    2007-01-01

    Functionality of biological and inorganic systems ranging from nonvolatile computer memories and microelectromechanical systems to electromotor proteins and cellular membranes is ultimately based on the intricate coupling between electrical and mechanical phenomena. In the past decade, piezoresponse force microscopy (PFM) has been established as a powerful tool for nanoscale imaging, spectroscopy, and manipulation of ferroelectric and piezoelectric materials. Here, we give an overview of the fundamental image formation mechanism in PFM and summarize recent theoretical and technological advances. In particular, we show that the signal formation in PFM is complementary to that in the scanning tunneling microscopy (STM) and atomic force microscopy (AFM) techniques, and we discuss the implications. We also consider the prospect of extending PFM beyond ferroelectric characterization for quantitative probing of electromechanical behavior in molecular and biological systems and high-resolution probing of static and dynamic polarization switching processes in low-dimensional ferroelectric materials and heterostructures.

  9. Large Electrocaloric Effect in Relaxor Ferroelectric and Antiferroelectric Lanthanum Doped Lead Zirconate Titanate Ceramics.

    PubMed

    Lu, Biao; Li, Peilian; Tang, Zhenhua; Yao, Yingbang; Gao, Xingsen; Kleemann, Wolfgang; Lu, Sheng-Guo

    2017-03-27

    Both relaxor ferroelectric and antiferroelectric materials can individually demonstrate large electrocaloric effects (ECE). However, in order to further enhance the ECE it is crucial to find a material system, which can exhibit simultaneously both relaxor ferroelectric and antiferroelectric properties, or easily convert from one into another in terms of the compositional tailoring. Here we report on a system, in which the structure can readily change from antiferroelectric into relaxor ferroelectric and vice versa. To this end relaxor ferroelectric Pb0.89La0.11(Zr0.7Ti0.3)0.9725O3 and antiferroelectric Pb0.93La0.07(Zr0.82Ti0.18)0.9825O3 ceramics were designed near the antiferroelectric-ferroelectric phase boundary line in the La2O3-PbZrO3-PbTiO3 phase diagram. Conventional solid state reaction processing was used to prepare the two compositions. The ECE properties were deduced from Maxwell relations and Landau-Ginzburg-Devonshire (LGD) phenomenological theory, respectively, and also directly controlled by a computer and measured by thermometry. Large electrocaloric efficiencies were obtained and comparable with the results calculated via the phenomenological theory. Results show great potential in achieving large cooling power as refrigerants.

  10. Graphene Based Surface Plasmon Polariton Modulator Controlled by Ferroelectric Domains in Lithium Niobate

    PubMed Central

    Wang, Hao; Zhao, Hua; Hu, Guangwei; Li, Siren; Su, Hang; Zhang, Jingwen

    2015-01-01

    We proposed a ferroelectric domain controlled graphene based surface plasmon polariton modulator. Ferroelectricity-induced electronic and optical property tuning of graphene by domain in lithium niobate was theoretically investigated considering both interband and intraband contributions of surface conductivity. With the corrected Sellmeier equation of lithium niobate, the propagation of transverse magnetic mode surface plasmon polaritons in an air/graphene/lithium niobate structure was studied when monolayer graphene was tuned by down polarization direction ferroelectric domain with different polarization levels. The length of the ferroelectric domain was optimized to be 90 nm for a wavelength of 5.0 μm with signal extinction per unit 14.7 dB/μm, modulation depth 474.1 dB/μm and figure of merit 32.5. This work may promote the study of highly efficient modulators and other ultra-compact nonvolatile electronic and photonic devices in which two-dimensional materials and ferroelectric materials are combined. PMID:26657622

  11. Mechanical confinement for tuning ferroelectric response in PMN-PT single crystal

    NASA Astrophysics Data System (ADS)

    Patel, Satyanarayan; Chauhan, Aditya; Vaish, Rahul

    2015-02-01

    Ferroelectrics form an important class of materials and are employed for a variety of applications. However, specific applications dictate the need of tailored ferroelectric response. This creates a requirement to obtain ferroelectric materials with tunable properties. Generally, chemical modifications or domain engineering are employed to this effect. This study attempts to shed light on the use of compressive pre-stresses for tuning and enhancing the ferroelectric properties. For the purpose, polarization versus electric field hysteresis data for 68Pb(Mn1/3Nb2/3)O3-32PbTiO3 (PMN-PT) single crystals were obtained as a function of uniaxial compressive stresses and operating temperatures. These data were utilized to investigate the effects of mechanical confinement for four individual case studies of electrocaloric effect, electrical energy storage, pyroelectric, and piezoelectric effect. A significant improvement was obtained for all case studies. The adiabatic temperature change was improved by ≈80% (28 MPa, 353 K); energy storage density increased by a factor of five (28 MPa, 353 K); pyroelectric figure of merits improved by an order of magnitude (21 MPa) and the piezoelectric coefficient was tailored (variable stress). The results offer promising insight into the use of directional confinement for improving application specific ferroelectric properties in PMN-PT single crystal.

  12. The demonstration of significant ferroelectricity in epitaxial Y-doped HfO2 film.

    PubMed

    Shimizu, Takao; Katayama, Kiliha; Kiguchi, Takanori; Akama, Akihiro; Konno, Toyohiko J; Sakata, Osami; Funakubo, Hiroshi

    2016-09-09

    Ferroelectricity and Curie temperature are demonstrated for epitaxial Y-doped HfO2 film grown on (110) yttrium oxide-stabilized zirconium oxide (YSZ) single crystal using Sn-doped In2O3 (ITO) as bottom electrodes. The XRD measurements for epitaxial film enabled us to investigate its detailed crystal structure including orientations of the film. The ferroelectricity was confirmed by electric displacement filed - electric filed hysteresis measurement, which revealed saturated polarization of 16 μC/cm(2). Estimated spontaneous polarization based on the obtained saturation polarization and the crystal structure analysis was 45 μC/cm(2). This value is the first experimental estimations of the spontaneous polarization and is in good agreement with the theoretical value from first principle calculation. Curie temperature was also estimated to be about 450 °C. This study strongly suggests that the HfO2-based materials are promising for various ferroelectric applications because of their comparable ferroelectric properties including polarization and Curie temperature to conventional ferroelectric materials together with the reported excellent scalability in thickness and compatibility with practical manufacturing processes.

  13. The demonstration of significant ferroelectricity in epitaxial Y-doped HfO2 film

    NASA Astrophysics Data System (ADS)

    Shimizu, Takao; Katayama, Kiliha; Kiguchi, Takanori; Akama, Akihiro; Konno, Toyohiko J.; Sakata, Osami; Funakubo, Hiroshi

    2016-09-01

    Ferroelectricity and Curie temperature are demonstrated for epitaxial Y-doped HfO2 film grown on (110) yttrium oxide-stabilized zirconium oxide (YSZ) single crystal using Sn-doped In2O3 (ITO) as bottom electrodes. The XRD measurements for epitaxial film enabled us to investigate its detailed crystal structure including orientations of the film. The ferroelectricity was confirmed by electric displacement filed – electric filed hysteresis measurement, which revealed saturated polarization of 16 μC/cm2. Estimated spontaneous polarization based on the obtained saturation polarization and the crystal structure analysis was 45 μC/cm2. This value is the first experimental estimations of the spontaneous polarization and is in good agreement with the theoretical value from first principle calculation. Curie temperature was also estimated to be about 450 °C. This study strongly suggests that the HfO2-based materials are promising for various ferroelectric applications because of their comparable ferroelectric properties including polarization and Curie temperature to conventional ferroelectric materials together with the reported excellent scalability in thickness and compatibility with practical manufacturing processes.

  14. The demonstration of significant ferroelectricity in epitaxial Y-doped HfO2 film

    PubMed Central

    Shimizu, Takao; Katayama, Kiliha; Kiguchi, Takanori; Akama, Akihiro; Konno, Toyohiko J.; Sakata, Osami; Funakubo, Hiroshi

    2016-01-01

    Ferroelectricity and Curie temperature are demonstrated for epitaxial Y-doped HfO2 film grown on (110) yttrium oxide-stabilized zirconium oxide (YSZ) single crystal using Sn-doped In2O3 (ITO) as bottom electrodes. The XRD measurements for epitaxial film enabled us to investigate its detailed crystal structure including orientations of the film. The ferroelectricity was confirmed by electric displacement filed – electric filed hysteresis measurement, which revealed saturated polarization of 16 μC/cm2. Estimated spontaneous polarization based on the obtained saturation polarization and the crystal structure analysis was 45 μC/cm2. This value is the first experimental estimations of the spontaneous polarization and is in good agreement with the theoretical value from first principle calculation. Curie temperature was also estimated to be about 450 °C. This study strongly suggests that the HfO2-based materials are promising for various ferroelectric applications because of their comparable ferroelectric properties including polarization and Curie temperature to conventional ferroelectric materials together with the reported excellent scalability in thickness and compatibility with practical manufacturing processes. PMID:27608815

  15. Large Electrocaloric Effect in Relaxor Ferroelectric and Antiferroelectric Lanthanum Doped Lead Zirconate Titanate Ceramics

    PubMed Central

    Lu, Biao; Li, Peilian; Tang, Zhenhua; Yao, Yingbang; Gao, Xingsen; Kleemann, Wolfgang; Lu, Sheng-Guo

    2017-01-01

    Both relaxor ferroelectric and antiferroelectric materials can individually demonstrate large electrocaloric effects (ECE). However, in order to further enhance the ECE it is crucial to find a material system, which can exhibit simultaneously both relaxor ferroelectric and antiferroelectric properties, or easily convert from one into another in terms of the compositional tailoring. Here we report on a system, in which the structure can readily change from antiferroelectric into relaxor ferroelectric and vice versa. To this end relaxor ferroelectric Pb0.89La0.11(Zr0.7Ti0.3)0.9725O3 and antiferroelectric Pb0.93La0.07(Zr0.82Ti0.18)0.9825O3 ceramics were designed near the antiferroelectric-ferroelectric phase boundary line in the La2O3-PbZrO3-PbTiO3 phase diagram. Conventional solid state reaction processing was used to prepare the two compositions. The ECE properties were deduced from Maxwell relations and Landau-Ginzburg-Devonshire (LGD) phenomenological theory, respectively, and also directly controlled by a computer and measured by thermometry. Large electrocaloric efficiencies were obtained and comparable with the results calculated via the phenomenological theory. Results show great potential in achieving large cooling power as refrigerants. PMID:28345655

  16. Negative capacitance in multidomain ferroelectric superlattices

    NASA Astrophysics Data System (ADS)

    Zubko, Pavlo; Wojdeł, Jacek C.; Hadjimichael, Marios; Fernandez-Pena, Stéphanie; Sené, Anaïs; Luk'Yanchuk, Igor; Triscone, Jean-Marc; Íñiguez, Jorge

    2016-06-01

    The stability of spontaneous electrical polarization in ferroelectrics is fundamental to many of their current applications, which range from the simple electric cigarette lighter to non-volatile random access memories. Research on nanoscale ferroelectrics reveals that their behaviour is profoundly different from that in bulk ferroelectrics, which could lead to new phenomena with potential for future devices. As ferroelectrics become thinner, maintaining a stable polarization becomes increasingly challenging. On the other hand, intentionally destabilizing this polarization can cause the effective electric permittivity of a ferroelectric to become negative, enabling it to behave as a negative capacitance when integrated in a heterostructure. Negative capacitance has been proposed as a way of overcoming fundamental limitations on the power consumption of field-effect transistors. However, experimental demonstrations of this phenomenon remain contentious. The prevalent interpretations based on homogeneous polarization models are difficult to reconcile with the expected strong tendency for domain formation, but the effect of domains on negative capacitance has received little attention. Here we report negative capacitance in a model system of multidomain ferroelectric-dielectric superlattices across a wide range of temperatures, in both the ferroelectric and paraelectric phases. Using a phenomenological model, we show that domain-wall motion not only gives rise to negative permittivity, but can also enhance, rather than limit, its temperature range. Our first-principles-based atomistic simulations provide detailed microscopic insight into the origin of this phenomenon, identifying the dominant contribution of near-interface layers and paving the way for its future exploitation.

  17. Negative capacitance in multidomain ferroelectric superlattices.

    PubMed

    Zubko, Pavlo; Wojdeł, Jacek C; Hadjimichael, Marios; Fernandez-Pena, Stéphanie; Sené, Anaïs; Luk'yanchuk, Igor; Triscone, Jean-Marc; Íñiguez, Jorge

    2016-06-23

    The stability of spontaneous electrical polarization in ferroelectrics is fundamental to many of their current applications, which range from the simple electric cigarette lighter to non-volatile random access memories. Research on nanoscale ferroelectrics reveals that their behaviour is profoundly different from that in bulk ferroelectrics, which could lead to new phenomena with potential for future devices. As ferroelectrics become thinner, maintaining a stable polarization becomes increasingly challenging. On the other hand, intentionally destabilizing this polarization can cause the effective electric permittivity of a ferroelectric to become negative, enabling it to behave as a negative capacitance when integrated in a heterostructure. Negative capacitance has been proposed as a way of overcoming fundamental limitations on the power consumption of field-effect transistors. However, experimental demonstrations of this phenomenon remain contentious. The prevalent interpretations based on homogeneous polarization models are difficult to reconcile with the expected strong tendency for domain formation, but the effect of domains on negative capacitance has received little attention. Here we report negative capacitance in a model system of multidomain ferroelectric-dielectric superlattices across a wide range of temperatures, in both the ferroelectric and paraelectric phases. Using a phenomenological model, we show that domain-wall motion not only gives rise to negative permittivity, but can also enhance, rather than limit, its temperature range. Our first-principles-based atomistic simulations provide detailed microscopic insight into the origin of this phenomenon, identifying the dominant contribution of near-interface layers and paving the way for its future exploitation.

  18. Antiferroelectric-to-Ferroelectric Switching in CH3NH3PbI3 Perovskite and Its Potential Role in Effective Charge Separation in Perovskite Solar Cells

    NASA Astrophysics Data System (ADS)

    Sewvandi, Galhenage A.; Hu, Dengwei; Chen, Changdong; Ma, Hao; Kusunose, Takafumi; Tanaka, Yasuhiro; Nakanishi, Shunsuke; Feng, Qi

    2016-08-01

    Perovskite solar cells (PSCs) often suffer from large performance variations which impede to define a clear charge-transfer mechanism. Ferroelectric polarization is measured numerically using CH3NH3PbI3 (M A PbI3 ) pellets to overcome the measurement issues such as pinholes and low uniformity of thickness, etc., with M A PbI3 thin films. M A PbI3 perovskite is an antiferroelectric semiconductor which is different from typical semiconducting materials and ferroelectric materials. The effect of polarization carrier separation on the charge-transfer mechanism in the PSCs is elucidated by using the results of ferroelectric and structural studies on the perovskite. The ferroelectric polarization contributes to an inherent carrier-separation effect and the I - V hysteresis. The ferroelectric and semiconducting synergistic charge-separation effect gives an alternative category of solar cells, ferroelectric semiconductor solar cells. Our findings identify the ferroelectric semiconducting behavior of the perovskite absorber as being significant to the improvement of the ferroelectric PSCs performances in future developments.

  19. Structural Consequences of Ferroelectric Nanolithography

    SciTech Connect

    J Young Jo; P Chen; R Sichel; S Bake; R Smith; N Balke; S Kalinin; M Holt; J Maser; et al.

    2011-12-31

    Domains of remnant polarization can be written into ferroelectrics with nanoscale precision using scanning probe nanolithography techniques such as piezoresponse force microscopy (PFM). Understanding the structural effects accompanying this process has been challenging due to the lack of appropriate structural characterization tools. Synchrotron X-ray nanodiffraction provides images of the domain structure written by PFM into an epitaxial Pb(Zr,Ti)O{sub 3} thin film and simultaneously reveals structural effects arising from the writing process. A coherent scattering simulation including the superposition of the beams simultaneously diffracted by multiple mosaic blocks provides an excellent fit to the observed diffraction patterns. Domains in which the polarization is reversed from the as-grown state have a strain of up to 0.1% representing the piezoelectric response to unscreened surface charges. An additional X-ray microdiffraction study of the photon-energy dependence of the difference in diffracted intensity between opposite polarization states shows that this contrast has a crystallographic origin. The sign and magnitude of the intensity contrast between domains of opposite polarization are consistent with the polarization expected from PFM images and with the writing of domains through the entire thickness of the ferroelectric layer. The strain induced by writing provides a significant additional contribution to the increased free energy of the written domain state with respect to a uniformly polarized state.

  20. Switching dynamics of thin film ferroelectric devices - a massively parallel phase field study

    NASA Astrophysics Data System (ADS)

    Ashraf, Md. Khalid

    In this thesis, we investigate the switching dynamics in thin film ferroelectrics. Ferroelectric materials are of inherent interest for low power and multi-functional devices. However, possible device applications of these materials have been limited due to the poorly understood electromagnetic and mechanical response at the nanoscale in arbitrary device structures. The difficulty in understanding switching dynamics mainly arises from the presence of features at multiple length scales and the nonlinearity associated with the strongly coupled states. For example, in a ferroelectric material, the domain walls are of nm size whereas the domain pattern forms at micron scale. The switching is determined by coupled chemical, electrostatic, mechanical and thermal interactions. Thus computational understanding of switching dynamics in thin film ferroelectrics and a direct comparison with experiment poses a significant numerical challenge. We have developed a phase field model that describes the physics of polarization dynamics at the microscopic scale. A number of efficient numerical methods have been applied for achieving massive parallelization of all the calculation steps. Conformally mapped elements, node wise assembly and prevention of dynamic loading minimized the communication between processors and increased the parallelization efficiency. With these improvements, we have reached the experimental scale - a significant step forward compared to the state of the art thin film ferroelectric switching dynamics models. Using this model, we elucidated the switching dynamics on multiple surfaces of the multiferroic material BFO. We also calculated the switching energy of scaled BFO islands. Finally, we studied the interaction of domain wall propagation with misfit dislocations in the thin film. We believe that the model will be useful in understanding the switching dynamics in many different experimental setups incorporating thin film ferroelectrics.

  1. Theoretical analysis of shock induced depolarization and current generation in ferroelectrics

    NASA Astrophysics Data System (ADS)

    Agrawal, Vinamra; Bhattacharya, Kaushik

    Ferroelectric generators are used to generate large magnitude current pulse by impacting a polarized ferroelectric material. The impact causes depolarization of the material and at high impact speeds, dielectric breakdown. Depending on the loading conditions and the electromechanical boundary conditions, the current or voltage profiles obtained vary. In this study, we explore the large deformation dynamic response of a ferroelectric material. Using the Maxwell's equations, conservation laws and the second law of thermodynamics, we derive the governing equations for the phase boundary propagation as well as the driving force acting on it. We allow for the phase boundary to contain surface charges which introduces the contribution of curvature of phase boundary in the governing equations and the driving force. This type of analysis accounts for the dielectric breakdown and resulting conduction in the material. Next, we implement the equations derived to solve a one dimensional impact problem on a ferroelectric material under different electrical boundary conditions. The constitutive law is chosen to be piecewise quadratic in polarization and quadratic in the strain. We solve for the current profile generated in short circuit case and for voltage profile in open circuited case. This work was made possible by the financial support of the US Air Force Office of Scientific Research through the Center of Excellence in High Rate Deformation Physics of Heterogeneous Materials (Grant: FA 9550-12-1-0091).

  2. Analysis of shock induced depolarization and current generation in ferroelectric ceramics

    NASA Astrophysics Data System (ADS)

    Agrawal, Vinamra; Bhattacharya, Kaushik

    2015-06-01

    Ferroelectric generators are used to generate large magnitude current pulse by impacting a polarized ferroelectric material. The impact causes depolarization of the material and at high impact speeds, dielectric breakdown. The current or voltage profiles obtained vary depending on the loading conditions. In this study, we explore the large deformation dynamic response of a ferroelectric material. Using the Maxwell's equations, conservation laws and the second law of thermodynamics, we derive the governing equations for the phase boundary propagation as well as the driving force acting on it. We allow for the phase boundary to contain surface charges which introduces the contribution of curvature of phase boundary in the governing equations and the driving force. This type of analysis accounts for the dielectric breakdown and resulting conduction in the material. Next, we implement the equations derived to solve a one dimensional impact problem on a ferroelectric material under different electrical boundary conditions. The constitutive law is chosen to be piecewise quadratic in polarization and quadratic in the strain. We solve for the current profile generated in short circuit case and for voltage profile in open circuited case. This work was made possible by the financial support of the US Air Force Office of Scientific Research through the Center of Excellence in High Rate Deformation Physics of Heterogeneous Materials (Grant: FA 9550-12-1-0091).

  3. Ultrafast Photovoltaic Response in Ferroelectric Nanolayers

    SciTech Connect

    Daranciang, Dan

    2012-02-15

    We show that light drives large-amplitude structural changes in thin films of the prototypical ferroelectric PbTiO3 via direct coupling to its intrinsic photovoltaic response. Using time-resolved x-ray scattering to visualize atomic displacements on femtosecond timescales, photoinduced changes in the unit-cell tetragonality are observed. These are driven by the motion of photogenerated free charges within the ferroelectric and can be simply explained by a model including both shift and screening currents, associated with the displacement of electrons first antiparallel to and then parallel to the ferroelectric polarization direction.

  4. Static Characteristics of the Ferroelectric Transistor Inverter

    NASA Technical Reports Server (NTRS)

    Mitchell, Cody; Laws, crystal; MacLeond, Todd C.; Ho, Fat D.

    2010-01-01

    The inverter is one of the most fundamental building blocks of digital logic, and it can be used as the foundation for understanding more complex logic gates and circuits. This paper presents the characteristics of an inverter circuit using a ferroelectric field-effect transistor. The voltage transfer characteristics are analyzed with respect to varying parameters such as supply voltage, input voltage, and load resistance. The effects of the ferroelectric layer between the gate and semiconductor are examined, and comparisons are made between the inverters using ferroelectric transistors and those using traditional MOSFETs.

  5. Curie transitions for attograms of ferroelectric polymers.

    PubMed

    Serghei, A; Zhao, W; Miranda, D; Russell, T P

    2013-02-13

    Polymer systems having one, two, or three dimensions on the nanometer length scale can exhibit physical properties different from the bulk. The degree of disorder characteristic for large amounts of matter is strongly reduced and changes in symmetry are imposed by means of geometrical confinement. This could be used to induce-through orientation and order-enhancement in the material properties. Experiments on extremely small amounts of matter, however, are naturally characterized by large fluctuations in the measured signals, especially in the case of polymer objects having three dimensions on the nanometer length scale. This imposes the necessity of repeating the measurements until a statistical distribution is obtained. Here we show that investigations on statistical ensembles of attograms of material (1 ag = 10(-18) g) are possible in a single experiment by employing highly ordered arrays of identical, independent, additive nanocontainers. Phase transitions corresponding to attograms of a ferroelectric polymer are measured by this approach. As compared to one- or two-dimensional confinement, significant changes in the Curie transitions are found.

  6. Thermally tunable ferroelectric thin film photonic crystals.

    SciTech Connect

    Lin, P. T.; Wessels, B. W.; Imre, A.; Ocola, L. E.; Northwestern Univ.

    2008-01-01

    Thermally tunable PhCs are fabricated from ferroelectric thin films. Photonic band structure and temperature dependent diffraction are calculated by FDTD. 50% intensity modulation is demonstrated experimentally. This device has potential in active ultra-compact optical circuits.

  7. Ferroelectricity in yttrium-doped hafnium oxide

    NASA Astrophysics Data System (ADS)

    Müller, J.; Schröder, U.; Böscke, T. S.; Müller, I.; Böttger, U.; Wilde, L.; Sundqvist, J.; Lemberger, M.; Kücher, P.; Mikolajick, T.; Frey, L.

    2011-12-01

    Structural and electrical evidence for a ferroelectric phase in yttrium doped hafnium oxide thin films is presented. A doping series ranging from 2.3 to 12.3 mol% YO1.5 in HfO2 was deposited by a thermal atomic layer deposition process. Grazing incidence X-ray diffraction of the 10 nm thick films revealed an orthorhombic phase close to the stability region of the cubic phase. The potential ferroelectricity of this orthorhombic phase was confirmed by polarization hysteresis measurements on titanium nitride based metal-insulator-metal capacitors. For 5.2 mol% YO1.5 admixture the remanent polarization peaked at 24 μC/cm2 with a coercive field of about 1.2 MV/cm. Considering the availability of conformal deposition processes and CMOS-compatibility, ferroelectric Y:HfO2 implies high scaling potential for future, ferroelectric memories.

  8. Strain tunable ferroelectric and dielectric properties of BaZrO{sub 3}

    SciTech Connect

    Zhang, Yajun; Liu, Man; Shimada, Takahiro; Kitamura, Takayuki; Wang, Jie

    2014-06-14

    The crucial role of epitaxial (in-plane) strain on the structural, electronic, energetic, ferroelectric, and dielectric properties of BaZrO{sub 3} (BZO) is investigated using density-functional theory calculations. We demonstrate that the BZO crystal subjected to a critical compressive (or tensile) strain exhibits non-trivial spontaneous polarization that is higher than that of well-known ferroelectrics BaTiO{sub 3}, while the BZO crystal is essentially paraelectric in the absence of strain. The electronic structure and Born-effective-charge analyses elucidate that the strain-induced paraelectric-to-ferroelectric transition is driven by the orbital hybridization of d-p electrons between zirconium and oxygen. Through the strain-induced paraelectric-to-ferroelectric phase transition, the dielectric response of BZO is significantly enhanced by the in-plane strain. The tensile strain increases the in-plane dielectric constant by a factor of seven with respect to that without the strain, while the compression tends to enhance the out-of-plane dielectric response. Therefore, strain engineering makes BZO an important electromechanical material due to the diversity in ferroelectric and dielectric properties.

  9. Emergent ferroelectricity in disordered tri-color multilayer structure comprised of ferromagnetic manganites

    NASA Astrophysics Data System (ADS)

    Niu, Li-Wei; Chen, Chang-Le; Dong, Xiang-Lei; Xing, Hui; Luo, Bing-Cheng; Jin, Ke-Xin

    2016-10-01

    Multiferroic materials, showing the coexistence and coupling of ferroelectric and magnetic orders, are of great technological and fundamental importance. However, the limitation of single phase multiferroics with robust magnetization and polarization hinders the magnetoelectric effect from being applied practically. Magnetic frustration, which can induce ferroelectricity, gives rise to multiferroic behavior. In this paper, we attempt to construct an artificial magnetically frustrated structure comprised of manganites to induce ferroelectricity. A disordered stacking of manganites is expected to result in frustration at interfaces. We report here that a tri-color multilayer structure comprised of non-ferroelectric La0.9Ca0.1MnO3(A)/Pr0.85Ca0.15MnO3(B)/Pr0.85Sr0.15MnO3(C) layers with the disordered arrangement of ABC-ACB-CAB-CBA-BAC-BCA is prepared to form magnetoelectric multiferroics. The multilayer film exhibits evidence of ferroelectricity at room temperature, thus presenting a candidate for multiferroics. Project supported by the National Natural Science Foundation of China (Grant Nos. 61471301, 61078057, 51172183, 51402240, and 51471134), the Specialized Research Fund for the Doctoral Program of Higher Education, China (Grant No. 20126102110045), the Natural Science Foundation of Shaanxi Province, China (Grant No. 2015JQ5125), and the Fundamental Research Funds for the Central Universities, China (Grant No. 3102015ZY078).

  10. Effect of antisite-like defect in ferroelectricity of SrTiO3 films

    NASA Astrophysics Data System (ADS)

    Yang, Fang; Yang, Zhenzhong; Gu, Lin; Guo, Jiandong; Institute of Physics, Chinese Academy of Sciences Team

    2014-03-01

    Ferroelectricity in thin films of nominally nonferroelectric materials such as SrTiO3 has been widely studied. It is known that some extrinsic factors such as strain [M. P. Warusawithana et al. Science 324, 367 (2009)] and defect [H. W. Jang et al., Phys. Rev. Lett. 104, 197601 (2010), M. Choi et al., Phys. Rev. Lett. 103, 185502 (2009)] can result in the ferroelectricity of SrTiO3 thin films. The SrTiO3 thin films with ferroelectricity were prepared on Si (001) substrates by oxide molecular beam epitaxy. The energy dispersive x-ray spectroscopy (EDX) mapping measurement results demonstrate Sr diffuses to the interface of SrTiO3 and Si. The cross sectional high-resolution transmission electron microscopy (HRTEM) results show that there are interstitial Ti atoms in the unit cells. The off-centered Ti from the Sr site along [100] or [110] direction can be regarded as a polar defect pair composed of a Sr vacancy and an interstitial Ti. It is predicted that Ti antisitelike defects in SrTiO3 are responsible for the ferroelectricity . Such antisitelike defects observed in SrTiO3 films are considered as the origin of the ferroelectricity. This work is supported by ``973'' Program of China (2012CB921700) and NSFC Project 11225422.

  11. Néel-like domain walls in ferroelectric Pb(Zr,Ti)O3 single crystals

    PubMed Central

    Wei, Xian-Kui; Jia, Chun-Lin; Sluka, Tomas; Wang, Bi-Xia; Ye, Zuo-Guang; Setter, Nava

    2016-01-01

    In contrast to the flexible rotation of magnetization direction in ferromagnets, the spontaneous polarization in ferroelectric materials is highly confined along the symmetry-allowed directions. Accordingly, chirality at ferroelectric domain walls was treated only at the theoretical level and its real appearance is still a mystery. Here we report a Néel-like domain wall imaged by atom-resolved transmission electron microscopy in Ti-rich ferroelectric Pb(Zr1−xTix)O3 crystals, where nanometre-scale monoclinic order coexists with the tetragonal order. The formation of such domain walls is interpreted in the light of polarization discontinuity and clamping effects at phase boundaries between the nesting domains. Phase-field simulation confirms that the coexistence of both phases as encountered near the morphotropic phase boundary promotes the polarization to rotate in a continuous manner. Our results provide a further insight into the complex domain configuration in ferroelectrics, and establish a foundation towards exploring chiral domain walls in ferroelectrics. PMID:27539075

  12. Controlled creation and displacement of charged domain walls in ferroelectric thin films

    PubMed Central

    Feigl, L.; Sluka, T.; McGilly, L. J.; Crassous, A.; Sandu, C. S.; Setter, N.

    2016-01-01

    Charged domain walls in ferroelectric materials are of high interest due to their potential use in nanoelectronic devices. While previous approaches have utilized complex scanning probe techniques or frustrative poling here we show the creation of charged domain walls in ferroelectric thin films during simple polarization switching using either a conductive probe tip or patterned top electrodes. We demonstrate that ferroelectric switching is accompanied - without exception - by the appearance of charged domain walls and that these walls can be displaced and erased reliably. We ascertain from a combination of scanning probe microscopy, transmission electron microscopy and phase field simulations that creation of charged domain walls is a by-product of, and as such is always coupled to, ferroelectric switching. This is due to the (110) orientation of the tetragonal (Pb,Sr)TiO3 thin films and the crucial role played by the limited conduction of the LSMO bottom electrode layer used in this study. This work highlights that charged domain walls, far from being exotic, unstable structures, as might have been assumed previously, can be robust, stable easily-controlled features in ferroelectric thin films. PMID:27507433

  13. INSTRUMENTS AND METHODS OF INVESTIGATION: Electron emission from ferroelectric plasma cathodes

    NASA Astrophysics Data System (ADS)

    Mesyats, G. A.

    2008-01-01

    Recent and not so recent experimental data are analyzed to show that the reason for strong electron emission from dielectric cathodes is the incomplete discharge occurring on the dielectric surface due to the electric field there being tangentially nonzero. The places of origin of such discharges are the metal-dielectric-vacuum triple junctions (TJs). As the discharge plasma moves over the surface of the dielectric electrode, the bias current arises, and an electric microexplosion occurs at a TJ. If the number of TJs is large, as it is for a metal grid held tightly to a ferroelectric, electron currents of up to 104 A with densities of more than 102 A cm-2 can be achieved. A surface discharge is initiated by applying a triggering pulse to the metal substrate deposited beforehand onto the opposite side of the ferroelectric. If this pulse leads the accelerating voltage pulse, the electron current is many times the Child-Langmuir current. The reason for the ferroelectric effect is the large permittivity (ɛ > 103) of the materials used (BaTiO3, PLZT, PZT). Although these devices have come to be known as ferroelectric cathodes, we believe ferroelectric plasma cathodes would be a better term to use to emphasize the key role of plasma effects.

  14. Suppression of creep-regime dynamics in epitaxial ferroelectric BiFeO3 films

    PubMed Central

    Shin, Y. J.; Jeon, B. C.; Yang, S. M.; Hwang, I.; Cho, M. R.; Sando, D.; Lee, S. R.; Yoon, J.-G.; Noh, T. W.

    2015-01-01

    Switching dynamics of ferroelectric materials are governed by the response of domain walls to applied electric field. In epitaxial ferroelectric films, thermally-activated ‘creep’ motion plays a significant role in domain wall dynamics, and accordingly, detailed understanding of the system’s switching properties requires that this creep motion be taken into account. Despite this importance, few studies have investigated creep motion in ferroelectric films under ac-driven force. Here, we explore ac hysteretic dynamics in epitaxial BiFeO3 thin films, through ferroelectric hysteresis measurements, and stroboscopic piezoresponse force microscopy. We reveal that identically-fabricated BiFeO3 films on SrRuO3 or La0.67Sr0.33MnO3 bottom electrodes exhibit markedly different switching behaviour, with BiFeO3/SrRuO3 presenting essentially creep-free dynamics. This unprecedented result arises from the distinctive spatial inhomogeneities of the internal fields, these being influenced by the bottom electrode’s surface morphology. Our findings further highlight the importance of controlling interface and defect characteristics, to engineer ferroelectric devices with optimised performance. PMID:26014521

  15. A new class of in-plane Ferroelectric Mott insulators via oxide hetorostructuring

    NASA Astrophysics Data System (ADS)

    Kim, Chanul; Park, Hyowon; Marianetti, Chris

    2015-03-01

    We propose simple design rules based on charge transfer, cation ordering, and size mismatch to design a new class of in-plane ferroelectric Mott insulators in perovskite-based transition metal oxides. Ab Initio DFT+U calculations are then used to selectively scan phase space based on these rules. We begin by exploring pairs of A-type ions (A, A') and pairs of B-type ions (B, B') in AA' BB'O6 which will have nominal charge transfer consistent with valencies that are conducive to a low Mott gap insulator. Additionally, the A-type ions are chosen to have a large size mismatch and stereochemical effect. The ordering of A/A' and B/B' still retains C4v symmetry which may be spontaneously broken to yield an in-plane ferroelectric. We uncover a number of materials which are strong candidates to be in-plane ferroelectric Mott insulators in experiment, including BaBiVCuO6, BaBiVNiO6, PbLaVCuO6. Finally, we will discuss potential applications of in-plane ferroelectric Mott insulators such as ferroelectric photovoltaics, Mott FET, and optoelectronic devices. Semiconductor Research Corporation (FAME).

  16. A second ferroelectric transition induced by pressure in multiferroic GdMn2O5

    NASA Astrophysics Data System (ADS)

    Lorenz, Bernd; Poudel, Narayan; Gooch, Melissa; Chu, Ching-Wu; Cheong, Sang-Wook

    2015-03-01

    In multiferroic materials different magnetic and ferroelectric states compete for the ground state and are usually close in energy. This results in a high sensitivity of the multiferroic state to external perturbations, such as magnetic fields or pressure, which has been demonstrated, e.g. in Ni3V2O8,MnWO4,andRMn2O5 (R = Tb, Ho, Dy, Y). Here we report the results of a high-pressure study of the multiferroic and ferroelectric properties of GdMn2O5,theRMn2O5 compound with the highest value of the polarization. The ferroelectric polarization below 29 K is enhanced upon application of pressure. Above a critical pressure, a second ferroelectric transition at even higher temperature is detected through a sizable increase of the polarization and a second peak of the dielectric constant. The ferroelectric polarization at high pressures exhibits two step-like increases upon decreasing temperature. This work was supported by the US AFOSR, the T.L.L. Temple Foundation, the John J. and Rebecca Moores Endowment, and the State of Texas through TCSUH.

  17. Design of ferroelectric organic molecular crystals with ultrahigh polarization.

    PubMed

    Chen, Shuang; Zeng, Xiao Cheng

    2014-04-30

    confirmed by experiments, the computer-aided ferroelectric material design on the basis of hydrogen-bonded charge-transfer complexes with flexible electron-donor and acceptor molecules would be proven valuable for expediting the search of room-temperature "displasive-type" ferroelectric organic crystals.

  18. Energy band alignment at ferroelectric/electrode interface determined by photoelectron spectroscopy

    NASA Astrophysics Data System (ADS)

    Chen, Feng; Wu, Wen-Bin; Li, Shun-Yi; Andreas, Klein

    2014-01-01

    The most important interface-related quantities determined by band alignment are the barrier heights for charge transport, given by the Fermi level position at the interface. Taking Pb(Zr,Ti)O3 (PZT) as a typical ferroelectric material and applying X-ray photoelectron spectroscopy (XPS), we briefly review the interface formation and barrier heights at the interfaces between PZT and electrodes made of various metals or conductive oxides. Polarization dependence of the Schottky barrier height at a ferroelectric/electrode interface is also directly observed using XPS.

  19. Single-step colloidal processing of stable aqueous dispersions of ferroelectric nanoparticles for biomedical imaging

    NASA Astrophysics Data System (ADS)

    Zribi, Olena; Garbovskiy, Yuriy; Glushchenko, Anatoliy

    2014-12-01

    The biomedical applications of ferroelectric nanoparticles rely on the production of stable aqueous colloids. We report an implementation of the high energy ball milling method to produce and disperse ultrafine BaTiO3 nanoparticles in an aqueous media in a single step. This technique is low-cost, environmentally friendly and has the capability to control nanoparticle size and functionality with milling parameters. As a result, ultrafine nanoparticles with sizes as small as 6 nm can be produced. These nanoparticles maintain ferroelectricity and can be used as second harmonic generating nanoprobes for biomedical imaging. This technique can be generalized to produce aqueous nanoparticle colloids of other imaging materials.

  20. Ferroelectricity Driven by Dzyaloshinskii-Moriya Interaction in an Anisotropic Heisenberg Antiferromagnetic Chain

    NASA Astrophysics Data System (ADS)

    Qi, Yan; Du, An

    2012-06-01

    We have made a theoretical study on the ferroelectricity and ferromagnetism in an antiferromagnetic Heisenberg chain with a Dzyaloshinskii-Moriya interaction which may induce ferroelectricity in some low-dimensional magnetic materials. Based on the transfer-matrix method, we obtain the analytical results of the average magnetization, polarization and magnetic susceptibility. And these physical quantities as functions of temperature and applied field are discussed respectively under various conditions. We find that the temperature dependence of the magnetic susceptibility exhibits different responses for the external field applied along the chain and perpendicular to the chain, demonstrating the important role of anisotropy.

  1. Enhancing interfacial magnetization with a ferroelectric

    DOE PAGES

    Meyer, Tricia L.; Herklotz, Andreas; Lauter, Valeria; ...

    2016-11-21

    Ferroelectric control of interfacial magnetism has attracted much attention. However, the coupling of these two functionalities has not been understood well at the atomic scale. The lack of scientific progress is mainly due to the limited characterization methods by which the interface’s magnetic properties can be probed at an atomic level. In this paper, we use polarized neutron reflectometry to probe the evolution of the magnetic moment at interfaces in ferroelectric/strongly correlated oxide [PbZr0.2Ti0.8O3/La0.8Sr0.2MnO3(PZT/LSMO)] heterostructures. We find that the magnetization at the surfaces and interfaces of our LSMO films without PZT are always deteriorated and such magnetic deterioration can bemore » greatly improved by interfacing with a strongly polar PZT film. Magnetoelectric coupling of magnetism and ferroelectric polarization was observed within a couple of nanometers of the interface via an increase in the LSMO surface magnetization to 4.0μB/f.u., a value nearly 70% higher than the surface magnetization of our LSMO film without interfacing with a ferroelectric layer. We attribute this behavior to hole depletion driven by the ferroelectric polarization. Finally, these compelling results not only probe the presence of nanoscale magnetic suppression and its control by ferroelectrics, but also emphasize the importance of utilizing probing techniques that can distinguish between bulk and interfacial phenomena.« less

  2. Three perimeter effects in ferroelectric nanostructures

    NASA Astrophysics Data System (ADS)

    Ruediger, Andreas; Peter, Frank; Waser, Rainer

    2006-03-01

    As the lateral size of ferroelectric nanoislands is now well below 50 nm, the question of size effects becomes increasingly relevant. Three independent techniques provided data of pronounced ferroelectric features along the perimeter: impedance spectroscopy [1], piezoelectric force microscopy [2] and pyroelectric current sensing [3]. However, as we can show, all three observations are related to the measurement technique that interferes with the lateral confinement and still there is no direct evidence of a lateral size effect in ferroelectric nanostructures. We discuss some scenarios of further downscaling and possible consequences. [1]M.Dawber, D.J. Jung, J.F. Scott, “Perimeter effect in very small ferroelectrics“,Appl. Phys. Lett. 82, 436 (2003) [2 ]F. Peter, A. Ruediger, R. Dittmann, R. Waser, K. Szot, B. Reichenberg, K. Prume, “Analysis of shape effects on the piezoresponse in ferroelectric nanograins with and without adsorbates”, Applied Physics Letters, 87, 082901 (2005) [3] B.W. Peterson, S. Ducharme, V.M. Fridkin, “Mapping surface Polarization in thin films of the ferroelectric polymer P(VDF-TrFE)”,Ferroelectrics, 304, 51 (2004)

  3. Enhancing interfacial magnetization with a ferroelectric

    NASA Astrophysics Data System (ADS)

    Meyer, Tricia L.; Herklotz, Andreas; Lauter, Valeria; Freeland, John W.; Nichols, John; Guo, Er-Jia; Lee, Shinbuhm; Ward, T. Zac; Balke, Nina; Kalinin, Sergei V.; Fitzsimmons, Michael R.; Lee, Ho Nyung

    2016-11-01

    Ferroelectric control of interfacial magnetism has attracted much attention. However, the coupling of these two functionalities has not been understood well at the atomic scale. The lack of scientific progress is mainly due to the limited characterization methods by which the interface's magnetic properties can be probed at an atomic level. Here, we use polarized neutron reflectometry to probe the evolution of the magnetic moment at interfaces in ferroelectric/strongly correlated oxide [PbZ r0.2T i0.8O3/L a0.8S r0.2Mn O3(PZT /LSMO ) ] heterostructures. We find that the magnetization at the surfaces and interfaces of our LSMO films without PZT are always deteriorated and such magnetic deterioration can be greatly improved by interfacing with a strongly polar PZT film. Magnetoelectric coupling of magnetism and ferroelectric polarization was observed within a couple of nanometers of the interface via an increase in the LSMO surface magnetization to 4.0 μB/f .u . , a value nearly 70% higher than the surface magnetization of our LSMO film without interfacing with a ferroelectric layer. We attribute this behavior to hole depletion driven by the ferroelectric polarization. These compelling results not only probe the presence of nanoscale magnetic suppression and its control by ferroelectrics, but also emphasize the importance of utilizing probing techniques that can distinguish between bulk and interfacial phenomena.

  4. Nanopatterned ferroelectrics for ultrahigh density rad-hard nonvolatile memories.

    SciTech Connect

    Brennecka, Geoffrey L.; Stevens, Jeffrey; Scrymgeour, David; Gin, Aaron V.; Tuttle, Bruce Andrew

    2010-09-01

    Radiation hard nonvolatile random access memory (NVRAM) is a crucial component for DOE and DOD surveillance and defense applications. NVRAMs based upon ferroelectric materials (also known as FERAMs) are proven to work in radiation-rich environments and inherently require less power than many other NVRAM technologies. However, fabrication and integration challenges have led to state-of-the-art FERAMs still being fabricated using a 130nm process while competing phase-change memory (PRAM) has been demonstrated with a 20nm process. Use of block copolymer lithography is a promising approach to patterning at the sub-32nm scale, but is currently limited to self-assembly directly on Si or SiO{sub 2} layers. Successful integration of ferroelectrics with discrete and addressable features of {approx}15-20nm would represent a 100-fold improvement in areal memory density and would enable more highly integrated electronic devices required for systems advances. Towards this end, we have developed a technique that allows us to carry out block copolymer self-assembly directly on a huge variety of different materials and have investigated the fabrication, integration, and characterization of electroceramic materials - primarily focused on solution-derived ferroelectrics - with discrete features of {approx}20nm and below. Significant challenges remain before such techniques will be capable of fabricating fully integrated NVRAM devices, but the tools developed for this effort are already finding broader use. This report introduces the nanopatterned NVRAM device concept as a mechanism for motivating the subsequent studies, but the bulk of the document will focus on the platform and technology development.

  5. Multiscale dynamics in relaxor ferroelectrics

    SciTech Connect

    Toulouse, J.; Cai, L; Pattnaik, R. K.; Boatner, Lynn A

    2014-01-01

    The multiscale dynamics of complex oxides is illustrated by pairs of mechanical resonances that are excited in the relaxor ferroelectric K1 xLixTaO3 (KLT). These macroscopic resonances are shown to originate in the collective dynamics of piezoelectric polar nanodomains (PND) interacting with the surrounding lattice. Their characteristic Fano lineshapes and rapid evolution with temperature reveal the coherent interplay between the piezoelectric oscillations and orientational relaxations of the PNDs at higher temperature and the contribution of heterophase oscillations near the phase transition. A theoretical model is presented, that describes the evolution of the resonances over the entire temperature range. Similar resonances are observed in other relaxors and must therefore be a common characteristics of these systems.

  6. Magnetic control of ferroelectric interfaces

    NASA Astrophysics Data System (ADS)

    Dussan, S.; Kumar, A.; Katiyar, R. S.; Priya, S.; Scott, J. F.

    2011-05-01

    We report the strong magnetic field dependence of ferroelectric PbZr0.52Ti0.48O3 (PZT) films on half-metallic oxide La0.67Sr0.33MnO3 (LSMO) electrodes. As the field H is increased, the hysteresis loop first broadens (becomes lossy) and then disappears at approximately H = 0.34 T and ambient temperatures. The data are compared with the theories of Pirč et al (2009 Phys. Rev. B 79 214114), Parish and Littlewood (2008 Phys. Rev. Lett. 101 166602) and Catalan (2006 Appl. Phys. Lett. 88 102902). The results are interpreted as due not to magnetocapacitance but to the sharp negative magnetoresistance in LSMO at low magnetic fields (Hwang et al 1996 Phys. Rev. Lett. 77 2041), which causes a dramatic increase in leakage current through the PZT.

  7. Lattice dynamics and ferroelectric properties of the nitride perovskite LaWN3

    NASA Astrophysics Data System (ADS)

    Fang, Yue-Wen; Fisher, Craig A. J.; Kuwabara, Akihide; Shen, Xin-Wei; Ogawa, Takafumi; Moriwake, Hiroki; Huang, Rong; Duan, Chun-Gang

    2017-01-01

    Using first-principles calculations we examine the crystal structures and phase transitions of nitride perovskite LaWN3. Lattice dynamics calculations indicate that the ground-state structure belongs to space group R 3 c . Two competitive phase transition pathways are identified which are characterized by symmetry-adapted distortion modes. The results suggest that R 3 c LaWN3 should be an excellent ferroelectric semiconductor, as its large spontaneous polarization of around 61 μ C /cm2 is comparable to that of PbTiO3, and its band gap is about 1.72 eV. Ferroelectricity is found to result from the B -site instability driven by hybridization between W -5 d and N -2 p orbitals. These properties make LaWN3 an attractive candidate material for use in ferroelectric memory devices and photovoltaic cells.

  8. Polarization-electric field hysteresis of ferroelectric PVDF films: comparison of different measurement regimes.

    PubMed

    Wegener, Michael

    2008-10-01

    Polarization-electric field hysteresis is an important property of ferroelectric materials. Different experimental procedures and measurement regimes are demonstrated and frequently used in order to determine this hysteresis behavior. For the characterization of the poling behavior of ferroelectric polymers it is common to analyze the poling current and separate current contributions, which are based on charging the sample capacitance as well as on conductivity. Experimentally this can be realized with two different measurement regimes, either poling of the sample with bipolar cycles or with a sequence of bipolar and unipolar cycles of the applied electric field. Here, we demonstrate the comparison of both measurement routines by performing poling experiments on the same ferroelectric PVDF sample.

  9. A phase-field study of the scaling law in free-standing ferroelectric thin films.

    PubMed

    Yin, Binglun; Mao, Huina; Qu, Shaoxing

    2015-12-18

    The scaling law for ferroelectric stripe domains is investigated in free-standing BaTiO3 and PbTiO3 thin films via phase-field simulations. The results agree with the Kittel law, where the square of the domain width is found to be proportional to the thin film thickness. After being rescaled by the corresponding domain wall thickness, the generalized scaling law is also demonstrated, with the dimensionless scaling constant M estimated to be ∼3.3 in two ferroelectric materials. Moreover, we predict the effect of the exchange constant which is incorporated in Ginzburg-Landau theory on the equilibrium domain width and the critical thickness of the ferroelectric thin films.

  10. High-density ferroelectric recording using a hard disk drive-type data storage system

    NASA Astrophysics Data System (ADS)

    Aoki, Tomonori; Hiranaga, Yoshiomi; Cho, Yasuo

    2016-05-01

    Ferroelectric probe data storage has been proposed as a novel data storage method in which bits are recorded based on the polarization directions of individual domains. These bits are subsequently read by scanning nonlinear dielectric microscopy. The domain walls of typical ferroelectric materials are quite thin: often only several times the lattice constant, which is advantageous for high-density data storage. In this work, high-density read/write (R/W) demonstrations were conducted using a hard disk drive-type test system, and the writing of bit arrays with a recording density of 3.4 Tbit/in.2 was achieved. Additionally, a series of writing and reading operations was successfully demonstrated at a density of 1 Tbit/in.2. Favorable characteristics of ferroelectric recording media for use with the proposed method are discussed in the latter part of this paper.

  11. Domains and ferroelectric switching pathways in Ca3Ti2O7 from first principles

    NASA Astrophysics Data System (ADS)

    Nowadnick, Elizabeth A.; Fennie, Craig J.

    2016-09-01

    Hybrid improper ferroelectricity, where an electrical polarization can be induced via a trilinear coupling to two nonpolar structural distortions of different symmetries, recently was demonstrated experimentally in the n =2 Ruddlesden-Popper compound Ca3Ti2O7 . In this paper we use group theoretic methods and first-principles calculations to identify possible ferroelectric switching pathways in Ca3Ti2O7 . We identify low-energy paths that reverse the polarization direction by switching via an orthorhombic twin domain or via an antipolar structure. We also introduce a chemically intuitive set of local order parameters to give insight into how these paths are relevant to ferroelectric switching nucleated at domain walls. Our findings suggest that switching may proceed via more than one mechanism in this material.

  12. The origin of incipient ferroelectricity in lead telluride

    PubMed Central

    Jiang, M. P.; Trigo, M.; Savić, I.; Fahy, S.; Murray, É. D.; Bray, C.; Clark, J.; Henighan, T.; Kozina, M.; Chollet, M.; Glownia, J. M.; Hoffmann, M. C.; Zhu, D.; Delaire, O.; May, A. F.; Sales, B. C.; Lindenberg, A. M.; Zalden, P.; Sato, T.; Merlin, R.; Reis, D. A.

    2016-01-01

    The interactions between electrons and lattice vibrations are fundamental to materials behaviour. In the case of group IV–VI, V and related materials, these interactions are strong, and the materials exist near electronic and structural phase transitions. The prototypical example is PbTe whose incipient ferroelectric behaviour has been recently associated with large phonon anharmonicity and thermoelectricity. Here we show that it is primarily electron-phonon coupling involving electron states near the band edges that leads to the ferroelectric instability in PbTe. Using a combination of nonequilibrium lattice dynamics measurements and first principles calculations, we find that photoexcitation reduces the Peierls-like electronic instability and reinforces the paraelectric state. This weakens the long-range forces along the cubic direction tied to resonant bonding and low lattice thermal conductivity. Our results demonstrate how free-electron-laser-based ultrafast X-ray scattering can be utilized to shed light on the microscopic mechanisms that determine materials properties. PMID:27447688

  13. The origin of incipient ferroelectricity in lead telluride

    SciTech Connect

    Jiang, M. P.; Trigo, M.; Savić, I.; Fahy, S.; Murray, É. D.; Bray, C.; Clark, J.; Henighan, T.; Kozina, M.; Chollet, M.; Glownia, J. M.; Hoffmann, M. C.; Zhu, D.; Delaire, O.; May, A. F.; Sales, B. C.; Lindenberg, A. M.; Zalden, P.; Sato, T.; Merlin, R.; Reis, D. A.

    2016-07-22

    The interactions between electrons and lattice vibrations are fundamental to materials behaviour. In the case of group IV–VI, V and related materials, these interactions are strong, and the materials exist near electronic and structural phase transitions. The prototypical example is PbTe whose incipient ferroelectric behaviour has been recently associated with large phonon anharmonicity and thermoelectricity. Here we show that it is primarily electron-phonon coupling involving electron states near the band edges that leads to the ferroelectric instability in PbTe. Using a combination of nonequilibrium lattice dynamics measurements and first principles calculations, we find that photoexcitation reduces the Peierls-like electronic instability and reinforces the paraelectric state. This weakens the long-range forces along the cubic direction tied to resonant bonding and low lattice thermal conductivity. Lastly, our results demonstrate how free-electron-laser-based ultrafast X-ray scattering can be utilized to shed light on the microscopic mechanisms that determine materials properties.

  14. The origin of incipient ferroelectricity in lead telluride

    DOE PAGES

    Jiang, M. P.; Trigo, M.; Savić, I.; ...

    2016-07-22

    The interactions between electrons and lattice vibrations are fundamental to materials behaviour. In the case of group IV–VI, V and related materials, these interactions are strong, and the materials exist near electronic and structural phase transitions. The prototypical example is PbTe whose incipient ferroelectric behaviour has been recently associated with large phonon anharmonicity and thermoelectricity. Here we show that it is primarily electron-phonon coupling involving electron states near the band edges that leads to the ferroelectric instability in PbTe. Using a combination of nonequilibrium lattice dynamics measurements and first principles calculations, we find that photoexcitation reduces the Peierls-like electronic instabilitymore » and reinforces the paraelectric state. This weakens the long-range forces along the cubic direction tied to resonant bonding and low lattice thermal conductivity. Lastly, our results demonstrate how free-electron-laser-based ultrafast X-ray scattering can be utilized to shed light on the microscopic mechanisms that determine materials properties.« less

  15. Effectively control negative thermal expansion of single-phase ferroelectrics of PbTiO3-(Bi,La)FeO3 over a giant range.

    PubMed

    Chen, Jun; Wang, Fangfang; Huang, Qingzhen; Hu, Lei; Song, Xiping; Deng, Jinxia; Yu, Ranbo; Xing, Xianran

    2013-01-01

    Control of negative thermal expansion is a fundamentally interesting topic in the negative thermal expansion materials in order for the future applications. However, it is a challenge to control the negative thermal expansion in individual pure materials over a large scale. Here, we report an effective way to control the coefficient of thermal expansion from a giant negative to a near zero thermal expansion by means of adjusting the spontaneous volume ferroelectrostriction (SVFS) in the system of PbTiO3-(Bi,La)FeO3 ferroelectrics. The adjustable range of thermal expansion contains most negative thermal expansion materials. The abnormal property of negative or zero thermal expansion previously observed in ferroelectrics is well understood according to the present new concept of spontaneous volume ferroelectrostriction. The present studies could be useful to control of thermal expansion of ferroelectrics, and could be extended to multiferroic materials whose properties of both ferroelectricity and magnetism are coupled with thermal expansion.

  16. Effectively control negative thermal expansion of single-phase ferroelectrics of PbTiO3-(Bi,La)FeO3 over a giant range

    PubMed Central

    Chen, Jun; Wang, Fangfang; Huang, Qingzhen; Hu, Lei; Song, Xiping; Deng, Jinxia; Yu, Ranbo; Xing, Xianran

    2013-01-01

    Control of negative thermal expansion is a fundamentally interesting topic in the negative thermal expansion materials in order for the future applications. However, it is a challenge to control the negative thermal expansion in individual pure materials over a large scale. Here, we report an effective way to control the coefficient of thermal expansion from a giant negative to a near zero thermal expansion by means of adjusting the spontaneous volume ferroelectrostriction (SVFS) in the system of PbTiO3-(Bi,La)FeO3 ferroelectrics. The adjustable range of thermal expansion contains most negative thermal expansion materials. The abnormal property of negative or zero thermal expansion previously observed in ferroelectrics is well understood according to the present new concept of spontaneous volume ferroelectrostriction. The present studies could be useful to control of thermal expansion of ferroelectrics, and could be extended to multiferroic materials whose properties of both ferroelectricity and magnetism are coupled with thermal expansion. PMID:23949238

  17. The Inorganie Fluoride and Oxyfluoride Ferroelectrics

    NASA Astrophysics Data System (ADS)

    Ravez, J.

    1997-06-01

    The ferroelectric fluorides belong to six families of type (NH4)2BeF4, BaMnF4, SrAlF5, Na2MgAlF7, K3Fe5F{15} or Pb5Cr3F{19}. The oxyfluorides can be separated in two groups: i) the true oxyfluorides with a relatively high F/O value (K3MoO3F3, Na5W3O9F5, Pb5W3O9F{10}, Bi2TiO4F2, ...); ii) the compositions derived from ferroelectric oxides (perovskite, tetragonal tungsten bronze, pyrochlore, LiTaO3, ...) characterized by a continuous F-O substitution. The phase transitions and the physical properties are discussed. The origin of the spontaneous polarization is described structurally. The variations of the Curie temperature with the type of substitution are related to chemical bonding. The potential interest of these materials for applications is briefly given. Les ferroélectriques fluorés appartiennent à six familles de type (NH4)_2BeF4, BaMnF4, SrAlF5, Na2MgAlF7, K3Fe5F{15} ou Pb5Cr3F{19}. Les oxyfluorures peuvent être séparés en deux groupes : i) les oxyfluorures “vrais” comportant un rapport F/O relativement élevé (K3MoO3F3, Na5W3O9F5, Pb5W3O9F{10}, Bi2TiO4F2, ...), ii) les compositions dérivées des oxydes ferroélectriques (perovskite, bronze quadratique de tungstène, pyrochlore, LiTaO3, ...) et caractérisées par une substitution F-O continue. Les transitions de phases et les propriétés physiques sont analysées. L'origine de la polarisation est précisée sur le plan structural. Les variations de la température de Curie avec le type de substitution sont reliées à des considérations de liaison chimique. L'intérêt potentiel de ces matériaux pour les applications est brièvement abordé.

  18. Ferroelectric fluoride compositions and methods of making and using same

    DOEpatents

    Halasyamani, P Shiv; Chang, Hong-Young

    2015-04-07

    A method for synthesis of a ferroelectric material characterized by the general formula A.sub.xB.sub.yF.sub.z where A is an alkaline earth metal, B is transition metal or a main group metal, x and y each range from about 1 to about 5, and z ranges from about 1 to about 20 comprising contacting an alkaline earth metal fluoride, a difluorometal compound and a fluoroorganic acid in a medium to form a reaction mixture; and subjecting the reaction mixture to conditions suitable for hydrothermal crystal growth.

  19. Ferroelectric all-polymer hollow Bragg fibers for terahertz guidance

    NASA Astrophysics Data System (ADS)

    Skorobogatiy, Maksim; Dupuis, Alexandre

    2007-03-01

    Design of hollow all-polymer Bragg fibers using periodic multilayers of ferroelectric polyvinylidene fluoride (PVDF) polymer and a low loss polycarbonate (PC) polymer is demonstrated. Efficient band gap guiding is predicted near the transverse optical frequency of a PVDF material in the terahertz regime. Optimal reflector designs are investigated in the whole terahertz region. Depending on frequency, the lowest loss hollow Bragg fiber can be one of the following: a photonic crystal fiber guiding in the band gap regime, a metamaterial fiber with a subwavelength reflector period, a single PC, or a PVDF tube.

  20. Multifunctional ferrimagnetic-ferroelectric thin films for microwave applications

    NASA Astrophysics Data System (ADS)

    Heindl, R.; Srikanth, H.; Witanachchi, S.; Mukherjee, P.; Heim, A.; Matthews, G.; Balachandran, S.; Natarajan, S.; Weller, T.

    2007-06-01

    Ferrimagnetic and ferroelectric structures based on barium strontium titanate and barium hexaferrite are investigated for potential applications in tunable microwave devices. Thin film bilayers were grown on MgO and sapphire, and their underlying crystallographic, microstructural, and magnetic properties were analyzed and compared. Microcircuits were fabricated using optical lithography, and microwave properties and electrical tunability were measured in the range of 1-50GHz. Overall, the studies demonstrate the possibility of realizing high quality multifunctional microwave materials that combine tunable magnetic and dielectric properties.

  1. Phononic Crystal Tunable via Ferroelectric Phase Transition

    NASA Astrophysics Data System (ADS)

    Xu, Chaowei; Cai, Feiyan; Xie, Shuhong; Li, Fei; Sun, Rong; Fu, Xianzhu; Xiong, Rengen; Zhang, Yi; Zheng, Hairong; Li, Jiangyu

    2015-09-01

    Phononic crystals (PCs) consisting of periodic materials with different acoustic properties have potential applications in functional devices. To realize more smart functions, it is desirable to actively control the properties of PCs on demand, ideally within the same fabricated system. Here, we report a tunable PC made of Ba0.7Sr0.3Ti O3 (BST) ceramics, wherein a 20-K temperature change near room temperature results in a 20% frequency shift in the transmission spectra induced by a ferroelectric phase transition. The tunability phenomenon is attributed to the structure-induced resonant excitation of A0 and A1 Lamb modes that exist intrinsically in the uniform BST plate, while these Lamb modes are sensitive to the elastic properties of the plate and can be modulated by temperature in a BST plate around the Curie temperature. The study finds opportunities for creating tunable PCs and enables smart temperature-tuned devices such as the Lamb wave filter or sensor.

  2. Advances in monolithic ferroelectric uncooled IRFPA technology

    NASA Astrophysics Data System (ADS)

    Hanson, Charles M.; Beratan, Howard R.; Belcher, James F.; Udayakumar, K. R.; Soch, Kevin L.

    1998-07-01

    The success of uncooled IR imaging at Raytheon has awakened a new view of the potential of thermal imaging. Once relegated to only expensive military platforms, occasionally to civilian platforms, and envisioned for individual soldiers, thermal imaging is now affordable for police cars, commercial surveillance, driving aids, and a variety of other industrial and consumer applications. System prices are as low as $8000, and swelling production volume will soon drive prices substantially lower. The impetus for further development is performance. The hybrid barium strontium titanate (BST) detectors currently in production have limited potential for improved sensitivity, and their MTF is suppressed at high frequencies. Microbolometer arrays in development at Raytheon have demonstrated performance superior to hybrid detectors. However, microbolometer technology lacks a mature, low-cost system technology and an abundance of deployable system implementations. Thin-film ferroelectric (TFFE) detectors have all the performance potential of microbolometers, and arguably more. They are also compatible with numerous fielded and planned system implementations. Like a microbolometer, the TFFE detector is monolithic; i.e., the detector material is deposited directly on the readout IC rather than being bump bonded to it. Initial imaging arrays of 240 X 320 pixels have been produced, demonstrating the feasibility of the technology.

  3. Ferroelectric-ferromagnetic multilayers: A magnetoelectric heterostructure with high output charge signal

    SciTech Connect

    Prokhorenko, S.; Kohlstedt, H.; Pertsev, N. A.

    2014-09-21

    Multiferroic composites and heterostructures comprising ferroelectric and ferromagnetic materials exhibit room-temperature magnetoelectric (ME) effects greatly exceeding those of single-phase magnetoelectrics known to date. Since these effects are mediated by the interfacial coupling between ferroic constituents, the ME responses may be enhanced by increasing the density of interfaces and improving their quality. A promising material system providing these features is a ferroelectric-ferromagnetic multilayer with epitaxial interfaces. In this paper, we describe theoretically the strain-mediated direct ME effect exhibited by free-standing multilayers composed of single-crystalline ferroelectric nanolayers interleaved by conducting ferromagnetic slabs. Using a nonlinear thermodynamic approach allowing for specific mechanical boundary conditions of the problem, we first calculate the polarization states and dielectric properties of ferroelectric nanolayers in dependence on the lattice mismatch between ferroic constituents and their volume fractions. In these calculations, the ferromagnetic component is described by a model which combines linear elastic behavior with magnetic-field-dependent lattice parameters. Then the quasistatic ME polarization and voltage coefficients are evaluated using the theoretical strain sensitivity of ferroelectric polarization and measured effective piezomagnetic coefficients of ferromagnets. For Pb(Zr₀.₅Ti₀.₅)O₃-FeGaB and BaTiO₃-FeGaB multilayers, the ME coefficients are calculated numerically as a function of the FeGaB volume fraction and used to evaluate the output charge and voltage signals. It is shown that the multilayer geometry of a ferroelectric-ferromagnetic nanocomposite opens the way for a drastic enhancement of the output charge signal. This feature makes biferroic multilayers advantageous for the development of ultrasensitive magnetic-field sensors for technical and biomedical applications.

  4. Fully printed and flexible ferroelectric capacitors based on a ferroelectric polymer for pressure detection

    NASA Astrophysics Data System (ADS)

    Sekine, Tomohito; Sugano, Ryo; Tashiro, Tomoya; Fukuda, Kenjiro; Kumaki, Daisuke; Domingues Dos Santos, Fabrice; Miyabo, Atsushi; Tokito, Shizuo

    2016-10-01

    We report on the fabrication and demonstration of fully printed ferroelectric capacitors using poly(vinylidene fluoridetrifluoroethylene) [P(VDF-TrFE)]. The printed ferroelectric capacitors were primarily fabricated by ink-jet printing on a thin plastic film substrate. The annealing process for the P(VDF-TrFE) layer was optimized from the viewpoints of surface morphology and crystallinity. A good ferroelectric polarization-electric field loop and piezoelectricity in the P(VDF-TrFE) were achieved for the printed ferroelectric capacitors. We have succeeded in the detection of a weak pressure of 150 mbar using the printed ferroelectric capacitor, which is an indication of a potential application to health-care biosensors. These results were realized by the optimization of the annealing temperature for the P(VDF-TrFE) layer.

  5. Development and characterization of a ferroelectric non-volatile memory for flexible electronics

    NASA Astrophysics Data System (ADS)

    Mao, Duo

    Flexible electronics have received significant attention recently because of the potential applications in displays, sensors, radio frequency identification (RFID) tags and other integrated circuits. Electrically addressable non-volatile memory is a key component for these applications. The major challenges are to fabricate the memory at a low temperature compatible with plastic substrates while maintaining good device reliability, by being compatible with process as needed to integrate with other electronic components for system-on-chip applications. In this work, ferroelectric capacitors fabricated at low temperature were developed. Based on that, a ferroelectric random access memory (FRAM) for flexible electronics was developed and characterized. Poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] copolymer was used as a ferroelectric material and a photolithographic process was developed to fabricate ferroelectric capacitors. Different characterization methods including atomic force microscopy, x-ray diffraction and Fourier-transform infrared reflection-absorption spectroscopy were used to study the material properties of the P(VDF-TrFE) film. The material properties were correlated with the electrical characteristics of the ferroelectric capacitors. To understand the polarization switching behavior of the P(VDF-TrFE) ferroelectric capacitors, a Nucleation-Limited-Switching (NLS) model was used to study the switching kinetics. The switching kinetics were characterized over the temperature range from -60 °C to 100 °C. Fatigue characteristics were studied at different electrical stress voltages and frequencies to evaluate the reliability of the ferroelectric capacitor. The degradation mechanism is attributed to the increase of the activation field and the suppression of the switchable polarization. To develop a FRAM circuit for flexible electronics, an n-channel thin film transistor (TFT) based on CdS as the semiconductor was integrated with a P

  6. Giant Electrocaloric Effect in Ferroelectrics with Tailored Polaw-Nanostructures

    SciTech Connect

    Zhang, Qiming

    2015-06-24

    Electrocaloric effect (ECE) is the temperature and/or entropy change in a dielectric material caused by an electric field induced polarization change. Although ECE has been studied since 1930s, the very small ECE observed in earlier studies in bulk materials before 2007 makes it not attractive for practical cooling applications. The objectives of this DOE program are to carry out a systematical scientific research on the entropy change and ECE in polar-dielectrics, especially ferroelectrics based on several fundamental hypotheses and to search for answers on a few scientific questions. Especially, this research program developed a series of polar-dielectric materials with controlled nano- and meso-structures and carried out studies on how these structures affect the polar-ordering, correlations, energy landscapes, and consequently the entropy states at different phases and ECE. The key hypotheses of the program include: (i) Whether a large ECE can be obtained near the ferroelectric-paraelectric (FE-PE) transition in properly designed ferroelectrics which possess large polarization P and large ß (the coefficient in the thermodynamic Landau theory where the Gibbs free energy G = G = G0+ ½ a P2 +1/4 b P4 + 1/6 c P6 – EP, and a = ß (T-Tc), where b,c,ß and Tc are constants)? (ii) What determines/determine ß? Whether a ferroelectric material with built-in disorders, which disrupt the polar-correlations and enabling a large number of local polar-states, such as a properly designed ferroelectric relaxor, can achieve a large ECE? (iii) How to design a ferroelectric material which has flat energy landscape so that the energy barriers for switching among different phases are vanishingly small? What are the necessary conditions to maximize the number of coexisting phases? (iv) How to design ferroelectric materials with a large tunable dielectric response? That is, at zero electric field, the material possesses very

  7. INVESTIGATION OF A COMPOUND REPORTED AS BOTH FERRIMAGNETIC AND FERROELECTRIC,

    DTIC Science & Technology

    FERRITES , *FERROELECTRIC CRYSTALS, MAGNETIC PROPERTIES, X RAY DIFFRACTION, IMPURITIES, FERROELECTRICITY, FERROMAGNETISM, CRYSTAL STRUCTURE...DIELECTRIC PROPERTIES, MICROSCOPY, BARIUM COMPOUNDS, SAMARIUM COMPOUNDS, NIOBIUM COMPOUNDS, TITANIUM COMPOUNDS, TITANATES, PHOTOMICROGRAPHY, CRYSTAL LATTICES, OXIDES.

  8. In situ X-ray diffraction and the evolution of polarization during the growth of ferroelectric superlattices

    PubMed Central

    Bein, Benjamin; Hsing, Hsiang-Chun; Callori, Sara J.; Sinsheimer, John; Chinta, Priya V.; Headrick, Randall L.; Dawber, Matthew

    2015-01-01

    In epitaxially strained ferroelectric thin films and superlattices, the ferroelectric transition temperature can lie above the growth temperature. Ferroelectric polarization and domains should then evolve during the growth of a sample, and electrostatic boundary conditions may play an important role. In this work, ferroelectric domains, surface termination, average lattice parameter and bilayer thickness are simultaneously monitored using in situ synchrotron X-ray diffraction during the growth of BaTiO3/SrTiO3 superlattices on SrTiO3 substrates by off-axis radio frequency magnetron sputtering. The technique used allows for scan times substantially faster than the growth of a single layer of material. Effects of electric boundary conditions are investigated by growing the same superlattice alternatively on SrTiO3 substrates and 20 nm SrRuO3 thin films on SrTiO3 substrates. These experiments provide important insights into the formation and evolution of ferroelectric domains when the sample is ferroelectric during the growth process. PMID:26634894

  9. In situ X-ray diffraction and the evolution of polarization during the growth of ferroelectric superlattices

    DOE PAGES

    Bein, Benjamin; Hsing, Hsiang-Chun; Callori, Sara J.; ...

    2015-12-04

    In the epitaxially strained ferroelectric thin films and superlattices, the ferroelectric transition temperature can lie above the growth temperature. Ferroelectric polarization and domains should then evolve during the growth of a sample, and electrostatic boundary conditions may play an important role. In this work, ferroelectric domains, surface termination, average lattice parameter and bilayer thickness are simultaneously monitored using in situ synchrotron X-ray diffraction during the growth of BaTiO3/SrTiO3 superlattices on SrTiO3 substrates by off-axis radio frequency magnetron sputtering. The technique used allows for scan times substantially faster than the growth of a single layer of material. Effects of electric boundarymore » conditions are investigated by growing the same superlattice alternatively on SrTiO3 substrates and 20 nm SrRuO3 thin films on SrTiO3 substrates. Our experiments provide important insights into the formation and evolution of ferroelectric domains when the sample is ferroelectric during the growth process.« less

  10. In situ X-ray diffraction and the evolution of polarization during the growth of ferroelectric superlattices

    SciTech Connect

    Bein, Benjamin; Hsing, Hsiang-Chun; Callori, Sara J.; Sinsheimer, John; Chinta, Priya V.; Headrick, Randall L.; Dawber, Matthew

    2015-12-04

    In the epitaxially strained ferroelectric thin films and superlattices, the ferroelectric transition temperature can lie above the growth temperature. Ferroelectric polarization and domains should then evolve during the growth of a sample, and electrostatic boundary conditions may play an important role. In this work, ferroelectric domains, surface termination, average lattice parameter and bilayer thickness are simultaneously monitored using in situ synchrotron X-ray diffraction during the growth of BaTiO3/SrTiO3 superlattices on SrTiO3 substrates by off-axis radio frequency magnetron sputtering. The technique used allows for scan times substantially faster than the growth of a single layer of material. Effects of electric boundary conditions are investigated by growing the same superlattice alternatively on SrTiO3 substrates and 20 nm SrRuO3 thin films on SrTiO3 substrates. Our experiments provide important insights into the formation and evolution of ferroelectric domains when the sample is ferroelectric during the growth process.

  11. Phase-field modeling of ferroelectric to paraelectric phase boundary structures in single-crystal barium titanate

    NASA Astrophysics Data System (ADS)

    Woldman, Alexandra Y.; Landis, Chad M.

    2016-03-01

    Ferroelectric perovskite materials have been shown to exhibit a large electrocaloric effect near phase transitions. We develop a computational model based on a phase-field approach to characterize the structure of ferroelectric to paraelectric phase boundaries for planar configurations under generalized plane strain with temperatures near the Curie temperature. A nonlinear finite element method is used to solve for the phase boundary structure of a representative unit cell with a 180° ferroelectric laminate for a range of domain widths. The temperature at which the phase boundary can be found increases with domain width, approaching the Curie temperature asymptotically. The excess free energy density per unit area of the boundary increases with domain width. As expected, closure domains form between the ferroelectric and paraelectric phase, and the shape of the closure domains evolves from triangular to needle-shaped as the domain width increases. The entropy jump across the phase boundary is quantified and is shown to increase with domain width as well. A planar configuration with a 90° ferroelectric laminate is investigated, but shown to be physically unlikely due to the high stress levels required to achieve strain compatibility between the phases. Possible three-dimensional structures of the ferroelectric-paraelectric phase boundary are also discussed.

  12. Uniaxial ferroelectric quantum criticality in multiferroic hexaferrites BaFe12O19 and SrFe12O19

    PubMed Central

    Rowley, S. E.; Chai, Yi-Sheng; Shen, Shi-Peng; Sun, Young; Jones, A. T.; Watts, B. E.; Scott, J. F.

    2016-01-01

    BaFe12O19 is a popular M-type hexaferrite with a Néel temperature of 720 K and is of enormous commercial value ($3 billion/year). It is an incipient ferroelectric with an expected ferroelectric phase transition extrapolated to lie at 6 K but suppressed due to quantum fluctuations. The theory of quantum criticality for such uniaxial ferroelectrics predicts that the temperature dependence of the electric susceptibility χ diverges as 1/T3, in contrast to the 1/T2 dependence found in pseudo-cubic materials such as SrTiO3 or KTaO3. In this paper we present evidence of the susceptibility varying as 1/T3, i.e. with a critical exponent γ = 3. In general γ = (d + z – 2)/z, where the dynamical exponent for a ferroelectric z = 1 and the dimension is increased by 1 from deff = 3 + z to deff = 4 + z due to the effect of long-range dipole interactions in uniaxial as opposed to multiaxial ferroelectrics. The electric susceptibility of the incipient ferroelectric SrFe12O19, which is slightly further from the quantum phase transition is also found to vary as 1/T3. PMID:27185343

  13. Uniaxial ferroelectric quantum criticality in multiferroic hexaferrites BaFe12O19 and SrFe12O19

    NASA Astrophysics Data System (ADS)

    Rowley, S. E.; Chai, Yi-Sheng; Shen, Shi-Peng; Sun, Young; Jones, A. T.; Watts, B. E.; Scott, J. F.

    2016-05-01

    BaFe12O19 is a popular M-type hexaferrite with a Néel temperature of 720 K and is of enormous commercial value ($3 billion/year). It is an incipient ferroelectric with an expected ferroelectric phase transition extrapolated to lie at 6 K but suppressed due to quantum fluctuations. The theory of quantum criticality for such uniaxial ferroelectrics predicts that the temperature dependence of the electric susceptibility χ diverges as 1/T3, in contrast to the 1/T2 dependence found in pseudo-cubic materials such as SrTiO3 or KTaO3. In this paper we present evidence of the susceptibility varying as 1/T3, i.e. with a critical exponent γ = 3. In general γ = (d + z – 2)/z, where the dynamical exponent for a ferroelectric z = 1 and the dimension is increased by 1 from deff = 3 + z to deff = 4 + z due to the effect of long-range dipole interactions in uniaxial as opposed to multiaxial ferroelectrics. The electric susceptibility of the incipient ferroelectric SrFe12O19, which is slightly further from the quantum phase transition is also found to vary as 1/T3.

  14. Uniaxial ferroelectric quantum criticality in multiferroic hexaferrites BaFe12O19 and SrFe12O19.

    PubMed

    Rowley, S E; Chai, Yi-Sheng; Shen, Shi-Peng; Sun, Young; Jones, A T; Watts, B E; Scott, J F

    2016-05-17

    BaFe12O19 is a popular M-type hexaferrite with a Néel temperature of 720 K and is of enormous commercial value ($3 billion/year). It is an incipient ferroelectric with an expected ferroelectric phase transition extrapolated to lie at 6 K but suppressed due to quantum fluctuations. The theory of quantum criticality for such uniaxial ferroelectrics predicts that the temperature dependence of the electric susceptibility χ diverges as 1/T(3), in contrast to the 1/T(2) dependence found in pseudo-cubic materials such as SrTiO3 or KTaO3. In this paper we present evidence of the susceptibility varying as 1/T(3), i.e. with a critical exponent γ = 3. In general γ = (d + z - 2)/z, where the dynamical exponent for a ferroelectric z = 1 and the dimension is increased by 1 from deff = 3 + z to deff = 4 + z due to the effect of long-range dipole interactions in uniaxial as opposed to multiaxial ferroelectrics. The electric susceptibility of the incipient ferroelectric SrFe12O19, which is slightly further from the quantum phase transition is also found to vary as 1/T(3).

  15. CuInP2S6 Room Temperature Layered Ferroelectric

    DOE PAGES

    Belianinov, Alex; He, Qian; Dziaugys, Andrius; ...

    2015-05-01

    In this paper, we explore ferroelectric properties of cleaved 2-D flakes of copper indium thiophosphate, CuInP2S6 (CITP), and probe size effects along with limits of ferroelectric phase stability, by ambient and ultra high vacuum scanning probe microscopy. CITP belongs to the only material family known to display ferroelectric polarization in a van der Waals, layered crystal at room temperature and above. Our measurements directly reveal stable, ferroelectric polarization as evidenced by domain structures, switchable polarization, and hysteresis loops. We found that at room temperature the domain structure of flakes thicker than 100 nm is similar to the cleaved bulk surfaces,more » whereas below 50 nm polarization disappears. We ascribe this behavior to a well-known instability of polarization due to depolarization field. Furthermore, polarization switching at high bias is also associated with ionic mobility, as evidenced both by macroscopic measurements and by formation of surface damage under the tip at a bias of 4 V—likely due to copper reduction. Mobile Cu ions may therefore also contribute to internal screening mechanisms. Finally, the existence of stable polarization in a van-der-Waals crystal naturally points toward new strategies for ultimate scaling of polar materials, quasi-2D, and single-layer materials with advanced and nonlinear dielectric properties that are presently not found in any members of the growing “graphene family”.« less

  16. Effect of charge on the ferroelectric field effect in strongly correlated oxides

    NASA Astrophysics Data System (ADS)

    Chen, Xuegang; Xiao, Zhiyong; Zhang, Xiaozhe; Zhang, Le; Zhao, Weiwei; Xu, Xiaoshan; Hong, Xia

    We present a systematic study of the effect of charge on the ferroelectric field effect modulation of various strongly correlated oxide materials. We have fabricated high quality epitaxial heterostructures composed of a ferroelectric Pb(Zr,Ti)O3 (PZT) gate and a correlated oxide channel, including Sm0.5Nd0.5NiO3 (SNNO), La0.7Sr0.3MnO3 (LSMO), SNNO/LSMO bilayers, and NiCo2O4 (NCO). The Hall effect measurements reveal a carrier density of ~4 holes/u.c. (0.4 cm2V-1s-1) for SNNO to ~2 holes/u.c. (27 cm2V-1s-1) for NCO. We find the magnitude of the field effect is closely related to both the intrinsic carrier density and carrier mobility of the channel material. For devices employing the SNNO/LSMO bilayer channel, we believe the charge transfer between the two correlated oxides play an important role in the observed resistance modulation. The screening capacitor of the channel materials and the interfacial defect states also have significant impact on the retention characteristics of the field effect. Our study reveals the critical role of charge in determining the interfacial coupling between ferroelectric and magnetic oxides, and has important implications in developing ferroelectric-controlled Mott memory devices.

  17. CuInP2S6 Room Temperature Layered Ferroelectric

    SciTech Connect

    Belianinov, Alex; He, Qian; Dziaugys, Andrius; Maksymovych, Petro; Eliseev, Eugene; Borisevich, Albina Y.; Morozovska, Anna N.; Banys, Juras; Vysochanskii, Yulian; Kalinin, Sergei V.

    2015-05-01

    In this paper, we explore ferroelectric properties of cleaved 2-D flakes of copper indium thiophosphate, CuInP2S6 (CITP), and probe size effects along with limits of ferroelectric phase stability, by ambient and ultra high vacuum scanning probe microscopy. CITP belongs to the only material family known to display ferroelectric polarization in a van der Waals, layered crystal at room temperature and above. Our measurements directly reveal stable, ferroelectric polarization as evidenced by domain structures, switchable polarization, and hysteresis loops. We found that at room temperature the domain structure of flakes thicker than 100 nm is similar to the cleaved bulk surfaces, whereas below 50 nm polarization disappears. We ascribe this behavior to a well-known instability of polarization due to depolarization field. Furthermore, polarization switching at high bias is also associated with ionic mobility, as evidenced both by macroscopic measurements and by formation of surface damage under the tip at a bias of 4 V—likely due to copper reduction. Mobile Cu ions may therefore also contribute to internal screening mechanisms. Finally, the existence of stable polarization in a van-der-Waals crystal naturally points toward new strategies for ultimate scaling of polar materials, quasi-2D, and single-layer materials with advanced and nonlinear dielectric properties that are presently not found in any members of the growing “graphene family”.

  18. Ferroelectric polarization effect on surface chemistry and photo-catalytic activity: A review

    NASA Astrophysics Data System (ADS)

    Khan, M. A.; Nadeem, M. A.; Idriss, H.

    2016-03-01

    The current efficiency of various photocatalytic processes is limited by the recombination of photogenerated electron-hole pairs in the photocatalyst as well as the back-reaction of intermediate species. This review concentrates on the use of ferroelectric polarization to mitigate electron-hole recombination and back-reactions and therefore improve photochemical reactivity. Ferroelectric materials are considered as wide band gap polarizable semiconductors. Depending on the surface polarization, different regions of the surface experience different extents of band bending and promote different carriers to move to spatially different locations. This can lead to some interesting interactions at the surface such as spatially selective adsorption and surface redox reactions. This introductory review covers the fundamental properties of ferroelectric materials, effect of an internal electric field/polarization on charge carrier separation, effect of the polarization on the surface photochemistry and reviews the work done on the use of these ferroelectric materials for photocatalytic applications such as dye degradation and water splitting. The manipulation of photogenerated charge carriers through an internal electric field/surface polarization is a promising strategy for the design of improved photocatalysts.

  19. Experimental and analytical modeling of resonant permittivity and permeability in ferroelectric-ferrite composites in microwave range

    NASA Astrophysics Data System (ADS)

    Ciomaga, Cristina E.; Balmus, Sorin B.; Dumitru, Ioan; Mitoseriu, Liliana

    2012-06-01

    The ferroelectric-magnetic composite materials are very suitable for designing and producing microwave devices and components, due to their dielectric and magnetic properties. For microwave antennas, sensors, resonators, oscillators, filters, phase shifters, attenuators, and amplifiers, the output and input impedances, the resonance frequencies, the quality factor (the losses), and the attenuation or the amplification can be very easily adjusted by modifying the dielectric permittivity or/and the magnetic permeability. This is possible by a right choice of the ratio between the ferroelectric and magnetic phases in the composite material. Therefore, it is highly important to accurately determine these characteristics of the composite material in microwave range.

  20. A high performance triboelectric nanogenerator for self-powered non-volatile ferroelectric transistor memory

    NASA Astrophysics Data System (ADS)

    Fang, Huajing; Li, Qiang; He, Wenhui; Li, Jing; Xue, Qingtang; Xu, Chao; Zhang, Lijing; Ren, Tianling; Dong, Guifang; Chan, H. L. W.; Dai, Jiyan; Yan, Qingfeng

    2015-10-01

    We demonstrate an integrated module of self-powered ferroelectric transistor memory based on the combination of a ferroelectric FET and a triboelectric nanogenerator (TENG). The novel TENG was made of a self-assembled polystyrene nanosphere array and a poly(vinylidene fluoride) porous film. Owing to this unique structure, it exhibits an outstanding performance with an output voltage as high as 220 V per cycle. Meanwhile, the arch-shaped TENG is shown to be able to pole a bulk ferroelectric 0.65Pb(Mg1/3Nb2/3)O3-0.35PbTiO3 (PMN-PT) single crystal directly. Based on this effect, a bottom gate ferroelectric FET was fabricated using pentacene as the channel material and a PMN-PT single crystal as the gate insulator. Systematic tests illustrate that the ON/OFF current ratio of this transistor memory element is approximately 103. More importantly, we demonstrate the feasibility to switch the polarization state of this FET gate insulator, namely the stored information, by finger tapping the TENG with a designed circuit. These results may open up a novel application of TENGs in the field of self-powered memory systems.We demonstrate an integrated module of self-powered ferroelectric transistor memory based on the combination of a ferroelectric FET and a triboelectric nanogenerator (TENG). The novel TENG was made of a self-assembled polystyrene nanosphere array and a poly(vinylidene fluoride) porous film. Owing to this unique structure, it exhibits an outstanding performance with an output voltage as high as 220 V per cycle. Meanwhile, the arch-shaped TENG is shown to be able to pole a bulk ferroelectric 0.65Pb(Mg1/3Nb2/3)O3-0.35PbTiO3 (PMN-PT) single crystal directly. Based on this effect, a bottom gate ferroelectric FET was fabricated using pentacene as the channel material and a PMN-PT single crystal as the gate insulator. Systematic tests illustrate that the ON/OFF current ratio of this transistor memory element is approximately 103. More importantly, we demonstrate the

  1. Ferroelectric and dielectric properties of ferrite-ferroelectric ceramic composites

    SciTech Connect

    Elena Ciomaga, Cristina; Maria Neagu, Alexandra; Valentin Pop, Mihai; Mitoseriu, Liliana; Airimioaei, Mirela; Tascu, Sorin; Schileo, Giorgio; Galassi, Carmen

    2013-02-21

    Particulate composites of ferrite and ferroelectric phases with xNiFe{sub 2}O{sub 4} (NF) and (1 - x)Pb{sub 0.988}(Zr{sub 0.52}Ti{sub 0.48}){sub 0.976}Nb{sub 0.024}O{sub 3} (where x = 2, 10, 20, 30, 50, 70, and 100 wt. %) were prepared in situ by sol-gel method. The presence of a diphase composition was confirmed by X-ray diffraction while the microstructure of the composites was studied by scanning electron microscopy revealing a good mixing of the two phases and a good densification of the bulk ceramics. The dielectric permittivity shows usual dielectric dispersion behavior with increasing frequency due to Maxwell-Wagner interfacial polarization. AC conductivity measurements made in frequency range 1 Hz-1 MHz suggest that the conduction process is due to mixed polaron hopping. The effect of NF phase concentration on the P-E and M-H hysteresis behavior and dielectric properties of the composites was investigated. At low NF concentration a sharp ferro-paraelectric transition peak can be observed at around 360 Degree-Sign C while for higher NF concentrations a trend to a diffuse phase transition occurs. All the composite samples exhibit typical ferromagnetic hysteresis loops, indicating the presence of ordered magnetic structure.

  2. Ferroelectric Thin-Film Capacitors As Ultraviolet Detectors

    NASA Technical Reports Server (NTRS)

    Thakoor, Sarita

    1995-01-01

    Advantages include rapid response, solar blindness, and relative invulnerability to ionizing radiation. Ferroelectric capacitor made to function as photovoltaic detector of ultraviolet photons by making one of its electrodes semitransparent. Photovoltaic effect exploited more fully by making Schottky barrier at illuminated semitransparent-electrode/ferroelectric interface taller than Schottky barrier at other electrode/ferroelectric interface.

  3. Tensile strain effect in ferroelectric perovskite oxide thin films on spinel magnesium aluminum oxide substrate

    NASA Astrophysics Data System (ADS)

    Zhou, Xiaolan

    Ferroelectrics are used in FeRAM (Ferroelectric random-access memory). Currently (Pb,Zr)TiO3 is the most common ferroelectric material. To get lead-free and high performance ferroelectric material, we investigated perovskite ferroelectric oxides (Ba,Sr)TiO3 and BiFeO3 films with strain. Compressive strain has been investigated intensively, but the effects of tensile strain on the perovskite films have yet to be explored. We have deposited (Ba,Sr)TiO3, BiFeO3 and related films by pulsed laser deposition (PLD) and analyzed the films by X-ray diffractometry (XRD), atomic force microscopy (AFM), etc. To obtain inherently fully strained films, the selection of the appropriate substrates is crucial. MgAl2O4 matches best with good quality and size, yet the spinel structure has an intrinsic incompatibility to that of perovskite. We introduced a rock-salt structure material (Ni 1-xAlxO1+delta) as a buffer layer to mediate the structural mismatch for (Ba,Sr)TiO3 films. With buffer layer Ni1-xAlxO1+delta, we show that the BST films have high quality crystallization and are coherently epitaxial. AFM images show that the films have smoother surfaces when including the buffer layer, indicating an inherent compatibility between BST-NAO and NAO-MAO. In-plane Ferroelectricity measurement shows double hysteresis loops, indicating an antiferroelectric-like behavior: pinned ferroelectric domains with antiparallel alignments of polarization. The Curie temperatures of the coherent fully strained BST films are also measured. It is higher than 900°C, at least 800°C higher than that of bulk. The improved Curie temperature makes the use of BST as FeRAM feasible. We found that the special behaviors of ferroelectricity including hysteresis loop and Curie temperature are due to inherent fully tensile strain. This might be a clue of physics inside ferroelectric stain engineering. An out-of-plane ferroelectricity measurement would provide a full whole story of the tensile strain. However, a

  4. Scaling Effects in Perovskite Ferroelectrics: Fundamental Limits and Process-Structure-Property Relations

    DOE PAGES

    Ihlefeld, Jon F.; Harris, David T.; Keech, Ryan; ...

    2016-07-05

    Ferroelectric materials are well-suited for a variety of applications because they can offer a combination of high performance and scaled integration. Examples of note include piezoelectrics to transform between electrical and mechanical energies, capacitors used to store charge, electro-optic devices, and non-volatile memory storage. Accordingly, they are widely used as sensors, actuators, energy storage, and memory components, ultrasonic devices, and in consumer electronics products. Because these functional properties arise from a non-centrosymmetric crystal structure with spontaneous strain and a permanent electric dipole, the properties depend upon physical and electrical boundary conditions, and consequently, physical dimension. The change of properties withmore » decreasing physical dimension is commonly referred to as a size effect. In thin films, size effects are widely observed, while in bulk ceramics, changes in properties from the values of large-grained specimens is most notable in samples with grain sizes below several microns. It is important to note that ferroelectricity typically persists to length scales of about 10 nm, but below this point is often absent. Despite the stability of ferroelectricity for dimensions greater than ~10 nm, the dielectric and piezoelectric coefficients of scaled ferroelectrics are suppressed relative to their bulk counterparts, in some cases by changes up to 80%. The loss of extrinsic contributions (domain and phase boundary motion) to the electromechanical response accounts for much of this suppression. In this article the current understanding of the underlying mechanisms for this behavior in perovskite ferroelectrics are reviewed. We focus on the intrinsic limits of ferroelectric response, the roles of electrical and mechanical boundary conditions, grain size and thickness effects, and extraneous effects related to processing. Ultimately, in many cases, multiple mechanisms combine to produce the observed scaling

  5. Scaling Effects in Perovskite Ferroelectrics: Fundamental Limits and Process-Structure-Property Relations

    SciTech Connect

    Ihlefeld, Jon F.; Harris, David T.; Keech, Ryan; Jones, Jacob L.; Maria, Jon-Paul; Trolier-McKinstry, Susan

    2016-07-05

    Ferroelectric materials are well-suited for a variety of applications because they can offer a combination of high performance and scaled integration. Examples of note include piezoelectrics to transform between electrical and mechanical energies, capacitors used to store charge, electro-optic devices, and non-volatile memory storage. Accordingly, they are widely used as sensors, actuators, energy storage, and memory components, ultrasonic devices, and in consumer electronics products. Because these functional properties arise from a non-centrosymmetric crystal structure with spontaneous strain and a permanent electric dipole, the properties depend upon physical and electrical boundary conditions, and consequently, physical dimension. The change of properties with decreasing physical dimension is commonly referred to as a size effect. In thin films, size effects are widely observed, while in bulk ceramics, changes in properties from the values of large-grained specimens is most notable in samples with grain sizes below several microns. It is important to note that ferroelectricity typically persists to length scales of about 10 nm, but below this point is often absent. Despite the stability of ferroelectricity for dimensions greater than ~10 nm, the dielectric and piezoelectric coefficients of scaled ferroelectrics are suppressed relative to their bulk counterparts, in some cases by changes up to 80%. The loss of extrinsic contributions (domain and phase boundary motion) to the electromechanical response accounts for much of this suppression. In this article the current understanding of the underlying mechanisms for this behavior in perovskite ferroelectrics are reviewed. We focus on the intrinsic limits of ferroelectric response, the roles of electrical and mechanical boundary conditions, grain size and thickness effects, and extraneous effects related to processing. Ultimately, in many cases, multiple mechanisms combine to produce the observed scaling effects.

  6. Contribution of oxygen vacancies to the ferroelectric behavior of Hf0.5Zr0.5O2 thin films

    NASA Astrophysics Data System (ADS)

    Shimizu, Takao; Yokouchi, Tatsuhiko; Oikawa, Takahiro; Shiraishi, Takahisa; Kiguchi, Takanori; Akama, Akihiro; Konno, Toyohiko J.; Gruverman, Alexei; Funakubo, Hiroshi

    2015-03-01

    The ferroelectric properties of the (Hf0.5Zr0.5)O2 films on Pt/Ti/SiO2/Si substrate are investigated. It is found that the films crystallized by annealing in O2 and N2 atmospheres have similar crystal structures as well as remanent polarization and coercive fields. Weak temperature and frequency dependences of the ferroelectric properties indicate that the hysteretic behavior in HfO2-based films originates not from the mobile defects but rather from the lattice ionic displacement, as is the case of the typical ferroelectric materials.

  7. Simulation studies of nucleation of ferroelectric polarization reversal.

    SciTech Connect

    Brennecka, Geoffrey L.; Winchester, Benjamin Michael

    2014-08-01

    Electric field-induced reversal of spontaneous polarization is the defining characteristic of a ferroelectric material, but the process(es) and mechanism(s) associated with the initial nucleation of reverse-polarity domains are poorly understood. This report describes studies carried out using phase field modeling of LiTaO3, a relatively simple prototype ferroelectric material, in order to explore the effects of either mechanical deformation or optically-induced free charges on nucleation and resulting domain configuration during field-induced polarization reversal. Conditions were selected to approximate as closely as feasible those of accompanying experimental work in order to provide not only support for the experimental work but also ensure that additional experimental validation of the simulations could be carried out in the future. Phase field simulations strongly support surface mechanical damage/deformation as effective for dramatically reducing the overall coercive field (Ec) via local field enhancements. Further, optically-nucleated polarization reversal appears to occur via stabilization of latent nuclei via the charge screening effects of free charges.

  8. Ferroelectric properties of niobium-doped strontium bismuth tantalate films

    NASA Astrophysics Data System (ADS)

    Golosov, D. A.; Zavadski, S. M.; Kolos, V. V.; Turtsevich, A. S.

    2016-01-01

    The characteristics of ferroelectric thin films of strontium bismuth tantalate (SBT) and niobium-doped strontium bismuth tantalate (SBTN) deposited by radio-frequency (RF) magnetron sputtering on Pt/TiO2/SiO2/Si substrates were investigated. For the formation of the structure of the ferroelectric material, the deposited films were subjected to a subsequent annealing at temperatures of 970-1070 K in an O2 atmosphere. The results of the X-ray diffraction analysis demonstrated that, in contrast to SBT films, in which the Aurivillius phase is formed only at annealing temperatures of 1050-1070 K, the formation of this phase in SBTN films is observed already at a temperature of 970 K. The dependences of the dielectric permittivity, remanent polarization, and coercive force of the SBT and SBTN films on the subsequent annealing conditions were determined. It was found that, upon doping of the SBT films with niobium, the remanent polarization increases by a factor of approximately three, the Curie temperature increases by 50 K, and the dielectric permittivity also increases. It was revealed that, in contrast to the SBT films, the polarization of the SBTN films is observed already at an annealing temperature of approximately 970 K. It was shown that the replacement of SBT films by SBTN films in the manufacture of high-density nonvolatile ferroelectric randomaccess memory (FeRAM) capacitor modules makes it possible to decrease the synthesis temperature from 1070 to 990-1000 K, which improves the compatibility with the planar technology of semiconductor devices. However, it turned out that an increase in the coercive field makes niobium-doped SBT films less attractive for the use in FeRAM.

  9. Molecular dynamics study of ferroelectric domain nucleation and domain switching dynamics.

    PubMed

    Boddu, Vishal; Endres, Florian; Steinmann, Paul

    2017-04-11

    Ferroelectric materials contain domains of ordered electric dipoles, separated by domain walls, that can undergo polarisation switching under externally applied electric fields. The domain switching dynamics in ferroelectric materials plays an essential role in their application to electronic and electro-optic de- vices. Previous studies suggest that the switching occurs largely through domain wall motion which is explained from the viewpoint of statistical physics on surface growth as the behaviour of a pinned elas- tic interface. We perform molecular dynamics simulations to investigate the domain switching process and quantitatively estimate the switching speed of anti-parallel 180° domains in ferroelectric, tetragonal BaTiO3 perfect single crystals at room temperature using the core-shell model. We observe an unprece- dented, non-linear increase in the domain switching speed caused by the nucleation of new domains within the switching domain. We determine the strength of the electric field to evoke nucleation of new domains and show that the nucleated domains diffuse into nearby favourable domains when the electric field is removed. Furthermore, we discuss the prominence of domain nucleations during ferroelectric switching.

  10. Fatigue mechanism of yttrium-doped hafnium oxide ferroelectric thin films fabricated by pulsed laser deposition.

    PubMed

    Huang, Fei; Chen, Xing; Liang, Xiao; Qin, Jun; Zhang, Yan; Huang, Taixing; Wang, Zhuo; Peng, Bo; Zhou, Peiheng; Lu, Haipeng; Zhang, Li; Deng, Longjiang; Liu, Ming; Liu, Qi; Tian, He; Bi, Lei

    2017-02-01

    Owing to their prominent stability and CMOS compatibility, HfO2-based ferroelectric films have attracted great attention as promising candidates for ferroelectric random-access memory applications. A major reliability issue for HfO2 based ferroelectric devices is fatigue. So far, there have been a few studies on the fatigue mechanism of this material. Here, we report a systematic study of the fatigue mechanism of yttrium-doped hafnium oxide (HYO) ferroelectric thin films deposited by pulsed laser deposition. The influence of pulse width, pulse amplitude and temperature on the fatigue behavior of HYO during field cycling is studied. The temperature dependent conduction mechanism is characterized after different fatigue cycles. Domain wall pinning caused by carrier injection at shallow defect centers is found to be the major fatigue mechanism of this material. The fatigued device can fully recover to the fatigue-free state after being heated at 90 °C for 30 min, confirming the shallow trap characteristic of the domain wall pinning defects.

  11. Pulsed laser ablation of ferroelectric composites for phased array antenna applications

    NASA Astrophysics Data System (ADS)

    Sengupta, S.; Green, S. M.

    1998-05-01

    Low loss composites have been fabricated in thick and thin film forms for a broad range of frequency applications. The thin film composites of barium strontium titanium oxide (BSTO) have been primarily developed by the pulsed laser ablation (PLA) method. This deposition technique has produced high quality thin films of BSTO composites on various substrates [S. Sengupta, L.C. Sengupta, W.E. Kosik, Pulsed laser deposition of ferroelectric thin films in conjunction with superconducting oxides, IEEE Cat# 94CH3416-5, 431][Analysis of ferroelectric thin films deposited by the pulsed laser deposition method on oxide and fluoride substrates, IEEE Cat# 94CH3416-5, 70][S. Sengupta, D.P. Vijay, S.B. Desu, Thin films of novel ferroelectric composites, Proceedings of MRS, 361, 1995, 545][S. Sengupta, L.C. Sengupta, Novel pyroelectric sensor materials, submitted to the Special Issue on Sensors and Actuators of the IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control]. The objective of this work is to elucidate the PLA deposition parameters of the BSTO composite thin films. The material characterization and the electronic parameters of the thin films will also be presented. Finally, the patterning techniques required to fabricate the BSTO composite thin film phase shifters will be discussed. Some preliminary results of the phase shifter characterization will also be presented.

  12. Permanent ferroelectric retention of BiFeO3 mesocrystal

    PubMed Central

    Hsieh, Ying-Hui; Xue, Fei; Yang, Tiannan; Liu, Heng-Jui; Zhu, Yuanmin; Chen, Yi-Chun; Zhan, Qian; Duan, Chun-Gang; Chen, Long-Qing; He, Qing; Chu, Ying-Hao

    2016-01-01

    Non-volatile electronic devices based on magnetoelectric multiferroics have triggered new possibilities of outperforming conventional devices for applications. However, ferroelectric reliability issues, such as imprint, retention and fatigue, must be solved before the realization of practical devices. In this study, everlasting ferroelectric retention in the heteroepitaxially constrained multiferroic mesocrystal is reported, suggesting a new approach to overcome the failure of ferroelectric retention. Studied by scanning probe microscopy and transmission electron microscopy, and supported via the phase-field simulations, the key to the success of ferroelectric retention is to prevent the crystal from ferroelastic deformation during the relaxation of the spontaneous polarization in a ferroelectric nanocrystal. PMID:27782123

  13. Ferroelectric Properties of Ultrathin Perovskite Heterostructures.

    NASA Astrophysics Data System (ADS)

    Junquera, Javier

    2004-03-01

    Due to their switchable spontaneous polarization, ferroelectric thin films can be used in non-volatile ferroelectric random access memories (FeRAMs). Recently, 30 Gbit/cm^2 data storage densities have been demonstrated for Pb(Zr_0.2Ti_0.8)O3 films on a metallic oxide electrode (T. Tybell et al.), Phys. Rev. Lett. 89, 097601 (2002). While industry's demands for ultrahigh density information storage imposes a reduction of the cell-sizes and thicknesses of the ferroelectric thin films, fundamental questions concerning thickness dependence of ferroelectricity and related properties becomes crucial. Using a first-principles density-functional-theory approach (J. M. Soler et al.), J. Phys.: Condens. Matter 14, 2745 (2002) we have simulated the behaviour at 0 K of a typical ferroelectric capacitor epitaxially grown on a SrTiO3 substrate and made of an ultrathin film of BaTiO3 in between two SrRuO3 electrodes in short circuit (J. Junquera and Ph. Ghosez, Nature 422), 506 (2003). Both the electrical and the mechanical boundary conditions were properly considered in the calculations. We predict the existence of a critical thickness for ferroelectricity of about six unit cells (26 Ang), and relate it to an incomplete screening of the depolarizing field by real metallic electrodes. Transposing these ideas into a first-principles-based model Hamiltonian, (U. V. Waghmare and K. M. Rabe, Phys. Rev. B 55), 6161 (1997) and using Monte Carlo simulations, we have analyzed the temperature dependence of the thickness evolution of the polarization and tetragonality of the samples, as well as the piezoelectric and dielectric tensors. Our theoretical results show good agreement with very recent experimental measurements.

  14. Enhancing interfacial magnetization with a ferroelectric

    SciTech Connect

    Meyer, Tricia L.; Herklotz, Andreas; Lauter, Valeria; Freeland, John W.; Nichols, John; Guo, Er-Jia; Lee, Shinbuhm; Ward, T. Zac; Balke, Nina; Kalinin, Sergei V.; Fitzsimmons, Michael R.; Lee, Ho Nyung

    2016-11-21

    Ferroelectric control of interfacial magnetism has attracted much attention. However, the coupling of these two functionalities has not been understood well at the atomic scale. The lack of scientific progress is mainly due to the limited characterization methods by which the interface’s magnetic properties can be probed at an atomic level. In this paper, we use polarized neutron reflectometry to probe the evolution of the magnetic moment at interfaces in ferroelectric/strongly correlated oxide [PbZr0.2Ti0.8O3/La0.8Sr0.2MnO3(PZT/LSMO)] heterostructures. We find that the magnetization at the surfaces and interfaces of our LSMO films without PZT are always deteriorated and such magnetic deterioration can be greatly improved by interfacing with a strongly polar PZT film. Magnetoelectric coupling of magnetism and ferroelectric polarization was observed within a couple of nanometers of the interface via an increase in the LSMO surface magnetization to 4.0μB/f.u., a value nearly 70% higher than the surface magnetization of our LSMO film without interfacing with a ferroelectric layer. We attribute this behavior to hole depletion driven by the ferroelectric polarization. Finally, these compelling results not only probe the presence of nanoscale magnetic suppression and its control by ferroelectrics, but also emphasize the importance of utilizing probing techniques that can distinguish between bulk and interfacial phenomena.

  15. Investigation of reduced (Srx,Ba1-x)Nb 2O6 as a ferroelectric-based thermoelectric

    NASA Astrophysics Data System (ADS)

    Bock, Jonathan A.

    A comprehensive study of a novel type of thermoelectric - a heavily doped material from a ferroelectric base composition - is presented. Due to the low-lying optic modes and scattering of phonons at domain walls, ferroelectrics make interesting candidates for thermoelectrics. The example of (Srx,Ba1-x)Nb2O6-delta (SBN) is explored in detail due to a report of an impressive thermoelectric figure of merit in single crystals. The goal of this research is to understand the source of the large figure of merit in SBN. In attempts to do this, the electron transport mechanism, the coupling between electron transport and ferroelectricity, the phase equilibria, and the single crystalline thermoelectric properties were investigated under various reduction conditions. It was found that the electron transport properties of a normal ferroelectric SBN can be well explained by activation of electrons into the conduction band from a localized impurity band. SBN can be shifted between a normal and relaxor ferroelectric by changing the Sr:Ba ratio. This property of SBN was utilized to study the effect of relaxor ferroelectricity on electron transport. Within the relaxor ferroelectric regime, a change in the activation energy for electronic conduction and an abnormal temperature dependence of the Seebeck coefficient were found. These properties are attributed to Anderson localization caused by the relaxor ferroelectricity. This is not thought to be the cause of the large thermoelectric figure of merit. The electron transport-ferroelectric coupling was also studied in oxygen deficient (Bax,Sr1-x)TiO3-delta (BST). A metallic-like to nonmetallic transition occurs at the ferroelectric transition, and the temperature of the metallic-like to nonmetallic transition can be shifted via Sr doping. The temperature shift on Sr doping is equivalent to the shift in the paraelectric ferroelectric transition temperature in unreduced samples, showing that the ferroelectric transition is the cause of

  16. Density inhomogeneity in ferroelectric thin films

    NASA Astrophysics Data System (ADS)

    Cao, Jiang-Li; Solbach, Axel; Klemradt, Uwe; Weirich, Thomas; Mayer, Joachim; Böttger, Ulrich; Schorn, Peter J.; Waser, Rainer

    2006-07-01

    Structural investigations of Pb(Zr ,Ti)O3 (PZT) ferroelectric thin films derived by chemical solution deposition on Pt /TiOx electrode stacks were performed using grazing incidence x-ray specular reflectivity of synchrotron radiation and transmission electron microscopy. A density inhomogeneity, i.e., a sublayer structure, in the PZT thin films was observed; the upper PZT sublayer had a lower density and the lower sublayer had a higher density. The influence of the density inhomogeneity, as a possible extrinsic contribution to size effects in ferroelectric thin films, was discussed.

  17. Intelligent Processing of Ferroelectric Thin Films

    DTIC Science & Technology

    1994-05-31

    Review," Ferroelectrics, 75, 25(1987) be determined by the compensator. With the PLZT phase modulator, the above (3] H. Higashino , T. Kawaguchi, H...Phys. Lett. 42(1983)867 4. F. Wang and G. Haertling, Appl. Phys. Lett. 63(1993)1730 5. H. Higashino et al, Japan. J. Appi. Phys. Vol. 24(1985...Single Crystals," Phza.JRev. 97, 414(1991) 1585(1965) (2] D. Bonsurant and F. Gnadinger, "Ferroelectrics for [10] H. Higashino , T. Kawaguchi, H. Adachi, T

  18. Switching Characteristics of Ferroelectric Transistor Inverters

    NASA Technical Reports Server (NTRS)

    Laws, Crystal; Mitchell, Coey; MacLeod, Todd C.; Ho, Fat D.

    2010-01-01

    This paper presents the switching characteristics of an inverter circuit using a ferroelectric field effect transistor, FeFET. The propagation delay time characteristics, phl and plh are presented along with the output voltage rise and fall times, rise and fall. The propagation delay is the time-delay between the V50% transitions of the input and output voltages. The rise and fall times are the times required for the output voltages to transition between the voltage levels V10% and V90%. Comparisons are made between the MOSFET inverter and the ferroelectric transistor inverter.

  19. Ferroelectric Cathodes in Transverse Magnetic Fields

    SciTech Connect

    Alexander Dunaevsky; Yevgeny Raitses; Nathaniel J. Fisch

    2002-07-29

    Experimental investigations of a planar ferroelectric cathode in a transverse magnetic field up to 3 kGs are presented. It is shown that the transverse magnetic field affects differently the operation of ferroelectric plasma cathodes in ''bright'' and ''dark'' modes in vacuum. In the ''bright'' mode, when the surface plasma is formed, the application of the transverse magnetic field leads to an increase of the surface plasma density. In the ''dark'' mode, the magnetic field inhibits the development of electron avalanches along the surface, as it does similarly in other kinds of surface discharges in the pre-breakdown mode.

  20. 95 GHz gyrotron with ferroelectric cathode.

    PubMed

    Einat, M; Pilossof, M; Ben-Moshe, R; Hirshbein, H; Borodin, D

    2012-11-02

    Ferroelectric cathodes were reported as a feasible electron source for microwave tubes. However, due to the surface plasma emission characterizing this cathode, operation of millimeter wave tubes based on it remains questionable. Nevertheless, the interest in compact high power sources of millimeter waves and specifically 95 GHz is continually growing. In this experiment, a ferroelectric cathode is used as an electron source for a gyrotron with the output frequency extended up to 95 GHz. Power above a 5 kW peak and ~0.5 μs pulses are reported; a duty cycle of 10% is estimated to be achievable.

  1. Investigation of ferroelectric phase transitions of water in nanoporous silicates in simultaneous electrical noise and calorimetric measurements

    NASA Astrophysics Data System (ADS)

    Bordonskiy, G. S.; Orlov, A. O.

    2014-08-01

    The phase transitions of water in the nanoporous silicate materials SBA-15 and MCM-41 with an ordered system of cylindrical pores have been investigated. Measurements of low-frequency electrical noises (Barkhausen noises) in the frequency range of 1-100 Hz have been performed simultaneously with relative calorimetric measurements. It has been found that the voltage of electrical fluctuations increases approximately 100 times in the temperature range from -30 to -50°C, which is associated with the first-order and second-order ferroelectric phase transitions. It has been assumed that the ferroelectric ice XI can be formed in capillary pores of the materials under investigations.

  2. Static ferroelectric memory transistor having improved data retention

    DOEpatents

    Evans, Jr., Joseph T.; Warren, William L.; Tuttle, Bruce A.

    1996-01-01

    An improved ferroelectric FET structure in which the ferroelectric layer is doped to reduce retention loss. A ferroelectric FET according to the present invention includes a semiconductor layer having first and second contacts thereon, the first and second contacts being separated from one another. The ferroelectric FET also includes a bottom electrode and a ferroelectric layer which is sandwiched between the semiconductor layer and the bottom electrode. The ferroelectric layer is constructed from a perovskite structure of the chemical composition ABO.sub.3 wherein the B site comprises first and second elements and a dopant element that has an oxidation state greater than +4 in sufficient concentration to impede shifts in the resistance measured between the first and second contacts with time. The ferroelectric FET structure preferably comprises Pb in the A-site. The first and second elements are preferably Zr and Ti, respectively. The preferred B-site dopants are Niobium, Tantalum, and Tungsten at concentrations between 1% and 8%.

  3. Carrier Density Modulation in Ge Heterostructure by Ferroelectric Switching

    SciTech Connect

    Ponath, Patrick; Fredrickson, Kurt; Posadas, Agham B.; Ren, Yuan; Vasudevan, Rama K.; Okatan, Mahmut Baris; Jesse, Stephen; Aoki, Toshihiro; McCartney, Martha; Smith, David J.; Kalinin, Sergei V.; Lai, Keji; Demkov, Alexander A.

    2015-01-14

    The development of nonvolatile logic through direct coupling of spontaneous ferroelectric polarization with semiconductor charge carriers is nontrivial, with many issues, including epitaxial ferroelectric growth, demonstration of ferroelectric switching, and measurable semiconductor modulation. Here we report a true ferroelectric field effect carrier density modulation in an underlying Ge(001) substrate by switching of the ferroelectric polarization in the epitaxial c-axis-oriented BaTiO3 (BTO) grown by molecular beam epitaxy (MBE) on Ge. Using density functional theory, we demonstrate that switching of BTO polarization results in a large electric potential change in Ge. Aberration-corrected electron microscopy confirms the interface sharpness, and BTO tetragonality. Electron-energy-loss spectroscopy (EELS) indicates the absence of any low permittivity interlayer at the interface with Ge. Using piezoelectric force microscopy (PFM), we confirm the presence of fully switchable, stable ferroelectric polarization in BTO that appears to be single domain. Using microwave impedance microscopy (MIM), we clearly demonstrate a ferroelectric field effect.

  4. First-principles study of interface doping in ferroelectric junctions

    PubMed Central

    Wang, Pin-Zhi; Cai, Tian-Yi; Ju, Sheng; Wu, Yin-Zhong

    2016-01-01

    Effect of atomic monolayer insertion on the performance of ferroelectric tunneling junction is investigated in SrRuO3/BaTiO3/SrRuO3 heterostrucutures. Based on first-principles calculations, the atomic displacement, orbital occupancy, and ferroelectric polarization are studied. It is found that the ferroelectricity is enhanced when a (AlO2)− monolayer is inserted between the electrode SRO and the barrier BTO, where the relatively high mobility of doped holes effectively screen ferroelectric polarization. On the other hand, for the case of (LaO)+ inserted layer, the doped electrons resides at the both sides of middle ferroelectric barrier, making the ferroelectricity unfavorable. Our findings provide an alternative avenue to improve the performance of ferroelectric tunneling junctions. PMID:27063704

  5. Ultrafast terahertz-field-driven ionic response in ferroelectric BaTiO3

    SciTech Connect

    Chen, F.; Zhu, Y.; Liu, S.; Qi, Y.; Hwang, H. Y.; Brandt, N. C.; Lu, J.; Quirin, F.; Enquist, H.; Zalden, P.; Hu, T.; Goodfellow, J.; Sher, M. -J.; Hoffmann, M. C.; Zhu, D.; Lemke, H.; Glownia, J.; Chollet, M.; Damodaran, A. R.; Park, J.; Cai, Z.; Jung, I. W.; Highland, M. J.; Walko, D. A.; Freeland, J. W.; Evans, P. G.; Vailionis, A.; Larsson, J.; Nelson, K. A.; Rappe, A. M.; Sokolowski-Tinten, K.; Martin, L. W.; Wen, H.; Lindenberg, A. M.

    2016-11-22

    The dynamical processes associated with electric field manipulation of the polarization in a ferroelectric remain largely unknown but fundamentally determine the speed and functionality of ferroelectric materials and devices. Here we apply subpicosecond duration, single-cycle terahertz pulses as an ultrafast electric field bias to prototypical BaTiO3 ferroelectric thin films with the atomic-scale response probed by femtosecond x-ray-scattering techniques. We show that electric fields applied perpendicular to the ferroelectric polarization drive large-amplitude displacements of the titanium atoms along the ferroelectric polarization axis, comparable to that of the built-in displacements associated with the intrinsic polarization and incoherent across unit cells. This effect is associated with a dynamic rotation of the ferroelectric polarization switching on and then off on picosecond time scales. These transient polarization modulations are followed by long-lived vibrational heating effects driven by resonant excitation of the ferroelectric soft mode, as reflected in changes in the c-axis tetragonality. The ultrafast structural characterization described here enables a direct comparison with first-principles-based molecular-dynamics simulations, with good agreement obtained.

  6. Synthesis, deposition and characterization of ferroelectric films for electrooptic devices

    NASA Astrophysics Data System (ADS)

    Tunaboylu, Bahadir

    The use of integrable ferroelectric electro-optic thin films is a revolutionary approach in the development of high-speed, low-voltage and high-contrast ratio integrated electro-optic spatial light modulators (SLM) for free-space optoelectronic interconnects. Thin films offer improved performance over bulk ferroelectric (FE) materials because of their lower modulator capacitance and operation at high speeds with low switching energies. Integration of ferroelectric thin films with silicon technology will also impact both the uncooled infrared sensor and dynamic and nonvolatile memory technologies. Ferroelectrics such as lead lanthanum zirconate titanate (PLZT) and patassium tantalate niobate (KTN) present great potential for SLMs due to their large electro-optic (EO) effect in the bulk form. The development of thin-film SLMs require electro-optic films of high optical quality with good dielectric and EO properties. High quality thin films of PLZT and KTN were deposited using RF magnetron sputtering on r-plane sapphire substrates which offer integration capability with semiconductor devices. PLZT films with extremely large peak dielectric constant, 2800 at the Curie temperature of 180sp°C, were achieved with remarkably low dissipation loss factor <0.04. The dielectric frequency dispersion was determined to be very small up to 1 Mhz. Also, the absorption of the light in the films was very low. A giant effective quadratic electrooptic effect was demonstrated in PLZT films. These results represent a huge leap forward for the FE-SLM technology with respect to the goal of fully integrated thin film electrooptic light modulators. Microstructural development and phase transformation kinetics in PLZT films were also analyzed for the first time and are presented here. Energy required for the formation of desirable perovskite phase was determined to be 322 kJ/mol. Single-phase PLZT films with larger average grain size showed higher dielectric constants and better EO

  7. Silicon-Based Optical Modulator with Ferroelectric Layer

    NASA Technical Reports Server (NTRS)

    Sheldon, Douglas

    2006-01-01

    According to a proposal, a silicon dioxide layer in a high-speed, low-power, silicon- based electro-optical modulator would be replaced by a layer of lead zirconate titanate or other ferroelectric oxide material. The purpose of this modification is to enhance the power performance and functionality of the modulator. In its unmodified form, the particular silicon- based electro-optical modulator is of an advanced design that overcomes the speed limitation of prior silicon-based electro- optical modulators. Whereas modulation frequencies of such devices had been limited to about 20 MHz, this modulator can operate at modulation frequencies as high as 1 GHz. This modulator can be characterized as a silicon-waveguide-based metal oxide/semiconductor (MOS) capacitor phase shifter in which modulation of the index of refraction in silicon is obtained by exploiting the free-charge-carrier-plasma dispersion effect. As shown in the figure, the modulator includes an n-doped crystalline silicon slab (the silicon layer of a silicon- on-insulator wafer) and a p-doped polycrystalline silicon rib with a gate oxide layer (the aforementioned silicon dioxide layer) sandwiched between them. Under accumulation conditions, the majority charge carriers in the silicon waveguide modify the index of refraction so that a phase shift is induced in the optical mode propagating in the waveguide. The advantage of using an MOS capacitor phase shifter is that it is possible to achieve high modulation speed because there are no slow carrier-generation or -recombination processes involved in the accumulation operation. The main advantage of the proposed substitution of a ferroelectric oxide layer for the silicon dioxide layer would arise from the spontaneous polarization effect of the ferroelectric layer: This spontaneous polarization would maintain accumulation conditions in the absence of applied voltage. Consequently, once the device had been switched to a given optical state, it would remain in

  8. Giant lateral electrostriction in ferroelectric liquid-crystalline elastomers.

    PubMed

    Lehmann, W; Skupin, H; Tolksdorf, C; Gebhard, E; Zentel, R; Krüger, P; Lösche, M; Kremer, F

    2001-03-22

    Mechanisms for converting electrical energy into mechanical energy are essential for the design of nanoscale transducers, sensors, actuators, motors, pumps, artificial muscles, and medical microrobots. Nanometre-scale actuation has to date been mainly achieved by using the (linear) piezoelectric effect in certain classes of crystals (for example, quartz), and 'smart' ceramics such as lead zirconate titanate. But the strains achievable in these materials are small--less than 0.1 per cent--so several alternative materials and approaches have been considered. These include grafted polyglutamates (which have a performance comparable to quartz), silicone elastomers (passive material--the constriction results from the Coulomb attraction of the capacitor electrodes between which the material is sandwiched) and carbon nanotubes (which are slow). High and fast strains of up to 4 per cent within an electric field of 150 MV x m(-1) have been achieved by electrostriction (this means that the strain is proportional to the square of the applied electric field) in an electron-irradiated poly(vinylidene fluoride-trifluoroethylene) copolymer. Here we report a material that shows a further increase in electrostriction by two orders of magnitude: ultrathin (less than 100 nanometres) ferroelectric liquid-crystalline elastomer films that exhibit 4 per cent strain at only 1.5 MV x m(-1). This giant electrostriction was obtained by combining the properties of ferroelectric liquid crystals with those of a polymer network. We expect that these results, which can be completely understood on a molecular level, will open new perspectives for applications.

  9. Multidomain ferroelectricity as a limiting factor for voltage amplification in ferroelectric field-effect transistors

    NASA Astrophysics Data System (ADS)

    Cano, A.; Jiménez, D.

    2010-09-01

    We revise the possibility of having an amplified surface potential in ferroelectric field-effect transistors pointed out by [S. Salahuddin and S. Datta, Nano Lett. 8, 405 (2008)]. We show that the negative-capacitance regime that allows for such amplification is actually bounded by the appearance of multidomain ferroelectricity. This imposes a severe limit to the maximum step-up of the surface potential obtainable in the device. We indicate new device design rules taking into account this scenario.

  10. Are lithium niobate (LiNbO3) and lithium tantalate (LiTaO3) ferroelectrics bioactive?

    PubMed

    Vilarinho, Paula Maria; Barroca, Nathalie; Zlotnik, Sebastian; Félix, Pedro; Fernandes, Maria Helena

    2014-06-01

    The use of functional materials, such as ferroelectrics, as platforms for tissue growth in situ or ex situ, is new and holds great promise. But the usage of materials in any bioapplication requires information on biocompatibility and desirably on bioactive behavior when bone tissue engineering is envisaged. Both requirements are currently unknown for many ferroelectrics. Herein the bioactivity of LiNbO3 and LiTaO3 is reported. The formation of apatite-like structures on the surface of LiNbO3 and LiTaO3 powders after immersion in simulated body fluid (SBF) for different soaking periods indicates their bioactive potential. The mechanism of apatite formation is suggested. In addition, the significant release of lithium ions from the ferroelectric powders in the very first minutes of soaking in SBF is examined and ways to overcome this likely hurdle addressed.

  11. A multi-surface model for ferroelectric ceramics - application to cyclic electric loading with changing maximum amplitude

    NASA Astrophysics Data System (ADS)

    Maniprakash, S.; Arockiarajan, A.; Menzel, A.

    2016-05-01

    Depending on the maximum amplitude of externally applied cyclic electric fields, ferroelectric ceramics show minor or major hysteresis. The materials also show asymmetric butterfly hysteresis in a prepoled material. Aiming at capturing these behaviour in a phenomenological constitutive model, a multi-surface modelling approach for ferroelectrics is introduced. In this paper, with the note on the motivation for a multi-surface model related to the results of new experimental investigations and also to experimental data reported in the literature, the constitutive relation for a rate dependent multi-surface ferroelectric model is developed. Following this, a brief graphical illustration shows how this model captures the objective phenomena. Consequently, the numerical implementation of the model to capture experimental results is demonstrated. Finally, the performance of this model to represent behaviour of decaying polarisation offset of electrically fatigued specimen is shown.

  12. Ferroelectric-field-effect-enhanced electroresistance in metal/ferroelectric/semiconductor tunnel junctions.

    PubMed

    Wen, Zheng; Li, Chen; Wu, Di; Li, Aidong; Ming, Naiben

    2013-07-01

    Ferroelectric tunnel junctions (FTJs), composed of two metal electrodes separated by an ultrathin ferroelectric barrier, have attracted much attention as promising candidates for non-volatile resistive memories. Theoretical and experimental works have revealed that the tunnelling resistance switching in FTJs originates mainly from a ferroelectric modulation on the barrier height. However, in these devices, modulation on the barrier width is very limited, although the tunnelling transmittance depends on it exponentially as well. Here we propose a novel tunnelling heterostructure by replacing one of the metal electrodes in a normal FTJ with a heavily doped semiconductor. In these metal/ferroelectric/semiconductor FTJs, not only the height but also the width of the barrier can be electrically modulated as a result of a ferroelectric field effect, leading to a greatly enhanced tunnelling electroresistance. This idea is implemented in Pt/BaTiO3/Nb:SrTiO3 heterostructures, in which an ON/OFF conductance ratio above 10(4), about one to two orders greater than those reported in normal FTJs, can be achieved at room temperature. The giant tunnelling electroresistance, reliable switching reproducibility and long data retention observed in these metal/ferroelectric/semiconductor FTJs suggest their great potential in non-destructive readout non-volatile memories.

  13. Ultrafast acousto-optic mode conversion in optically birefringent ferroelectrics

    PubMed Central

    Lejman, Mariusz; Vaudel, Gwenaelle; Infante, Ingrid C.; Chaban, Ievgeniia; Pezeril, Thomas; Edely, Mathieu; Nataf, Guillaume F.; Guennou, Mael; Kreisel, Jens; Gusev, Vitalyi E.; Dkhil, Brahim; Ruello, Pascal

    2016-01-01

    The ability to generate efficient giga–terahertz coherent acoustic phonons with femtosecond laser makes acousto-optics a promising candidate for ultrafast light processing, which faces electronic device limits intrinsic to complementary metal oxide semiconductor technology. Modern acousto-optic devices, including optical mode conversion process between ordinary and extraordinary light waves (and vice versa), remain limited to the megahertz range. Here, using coherent acoustic waves generated at tens of gigahertz frequency by a femtosecond laser pulse, we reveal the mode conversion process and show its efficiency in ferroelectric materials such as BiFeO3 and LiNbO3. Further to the experimental evidence, we provide a complete theoretical support to this all-optical ultrafast mechanism mediated by acousto-optic interaction. By allowing the manipulation of light polarization with gigahertz coherent acoustic phonons, our results provide a novel route for the development of next-generation photonic-based devices and highlight new capabilities in using ferroelectrics in modern photonics. PMID:27492493

  14. Studies on grain-boundary effects of ferroelectric polycrystals

    NASA Astrophysics Data System (ADS)

    Jayabal, K.; Arockiarajan, A.; Sivakumar, S. M.; Sansour, C.

    2008-07-01

    The aim of this paper is to study the nonlinear dissipative effects of ferroelectric polycrystals based on firm thermodynamics principles. The developed micro-mechanically motivated model is embedded into an electromechanically coupled finite element formulation. In this framework, each domain is represented by a single finite element, and initial dipole directions are randomly oriented so that the virgin state of the particular bulk ceramics of interest reflects an un-poled material. Thermodynamically consistent energy criterion based on Gibbs free energy is adopted for the initiation of domain switching processes. The so-called grain-boundary effects, that is the constraint imposed by the surrounding grains on a grain at its boundary is incorporated in this model by means of micro-macromechanically motivated concept. In the expression for the driving force, an additional term is incorporated based on the change in Gibbs free energy of the neighboring grains for the particular switching domain/grain of interest. To study the overall bulk ceramics behavior, straightforward volume averaging techniques are applied. The simulated numerical results show appreciable improvement in modeling the nonlinear response for ferroelectrics subjected to various loading aspects compared with the experimental data from the literature.

  15. Discriminator Stabilized Superconductor/Ferroelectric Thin Film Local Oscillator

    NASA Technical Reports Server (NTRS)

    Romanofsky, Robert R. (Inventor); Miranda, Felix A. (Inventor)

    2000-01-01

    A tunable local oscillator with a tunable circuit that includes a resonator and a transistor as an active element for oscillation. Tuning of the circuit is achieved with an externally applied dc bias across coupled lines on the resonator. Preferably the resonator is a high temperature superconductor microstrip ring resonator with integral coupled lines formed over a thin film ferroelectric material. A directional coupler samples the output of the oscillator which is fed into a diplexer for determining whether the oscillator is performing at a desired frequency. The high-pass and lowpass outputs of the diplexer are connected to diodes respectively for inputting the sampled signals into a differential operational amplifier. The amplifier compares the sampled signals and emits an output signal if there is a difference between the resonant and crossover frequencies. Based on the sampled signal, a bias supplied to the ring resonator is either increased or decreased for raising or lowering the resonant frequency by decreasing or increasing, respectively, the dielectric constant of the ferroelectric.

  16. Microwave conductance of ferroelectric domain walls in lead titanate

    NASA Astrophysics Data System (ADS)

    Tselev, Alexander; Cao, Ye; Yu, Pu; Kalinin, Sergei V.; Maksymovych, Petro

    Numerous theoretical works predicted electronically conducting domain walls in otherwise insulating ferroelectric crystals. A number of recent experiments reported conducting walls, although conductivity itself and a conclusive proof of conductance mechanism remain elusive, largely due to the electrical contact problem. The latter can be overcome using high-frequency AC voltage. Here we will present our successful measurements of microwave conductance at 180o domain walls in lead titanate using microwave microscopy. AC conducting domain walls can be repeatably reconfigured and have extraordinary stability in time and temperature. AC conductivity is detected even when DC is not. Quantitative modeling reveals that the conductance of domain walls is comparable to doped silicon. We will also present a new and robust mechanism to create charged domain walls in any ferroelectric lattice. Overall, this sets the stage for a new generation of local experiments on conducting domain walls, and furthers the prospects of their application in fast electronic devices. AT, YC, SVK, PM supported by Division of Materials Sciences and Engineering, Office of Science, Basic Energy Sciences, U. S. DOE. PY supported by the National Basic Research Program of China (2015CB921700).

  17. Origin of stationary domain wall enhanced ferroelectric susceptibility

    NASA Astrophysics Data System (ADS)

    Liu, Shi; Cohen, R. E.

    2017-03-01

    Ferroelectrics usually adopt a multidomain state with domain walls separating domains with polarization axes oriented differently. It has long been recognized that domain walls can dramatically impact the properties of ferroelectric materials. The enhancement of low-field susceptibility/permittivity under subswitching conditions is usually attributed to reversible domain wall vibration. Recent experiments highlight the stationary domain wall contribution to the dielectric susceptibility irrespective of any lateral displacements or deformations of the wall. We study the effects of domain walls on the low-field permittivity of PbTiO3 with density functional theory and molecular dynamics simulations. The static dielectric constant is calculated as a function of increasing domain wall density and temperature. We find an increase of dielectric permittivity with increasing domain wall density, which is expected to occur at a low driving field where the lateral motion of domain walls is forbidden. Real-space decomposition of the dielectric response reveals that frustrated dipoles within the finite width of the domain walls are responsible for the enhanced low-field permittivity. We explain the 100 % enhancement of the dielectric susceptibility form domain walls, which arises from the softer potential wells within them.

  18. Simulation Model of A Ferroelectric Field Effect Transistor

    NASA Technical Reports Server (NTRS)

    MacLeod, Todd C.; Ho, Fat Duen; Russell, Larry W. (Technical Monitor)

    2002-01-01

    An electronic simulation model has been developed of a ferroelectric field effect transistor (FFET). This model can be used in standard electrical circuit simulation programs to simulate the main characteristics of the FFET. The model uses a previously developed algorithm that incorporates partial polarization as a basis for the design. The model has the main characteristics of the FFET, which are the current hysterisis with different gate voltages and decay of the drain current when the gate voltage is off. The drain current has values matching actual FFET's, which were measured experimentally. The input and output resistance in the model is similar to that of the FFET. The model is valid for all frequencies below RF levels. A variety of different ferroelectric material characteristics can be modeled. The model can be used to design circuits using FFET'S with standard electrical simulation packages. The circuit can be used in designing non-volatile memory circuits and logic circuits and is compatible with all SPICE based circuit analysis programs. The model is a drop in library that integrates seamlessly into a SPICE simulation. A comparison is made between the model and experimental data measured from an actual FFET.

  19. Dielectric Property Change of Ferroelectrics and Electronic Structures

    NASA Astrophysics Data System (ADS)

    Fujita, Masaki; Sekine, Rika; Sugihara, Sunao

    1999-09-01

    Electronic structures were investigated in relation to the relative permittivity of ferroelectrics such as the ABO3-type and A- and/or B-substituted materials, using amolecular orbital method. The A-site ions were Ba, Pb, Sr and Ca, andthe B-site ion was Zr. Calculation was performed using theDV-Xα (discrete variational Xα) method and the overlappopulation, which is related to the covalent bonding nature, was discussed together with the effective charge. As a result, the change from ferroelectric to paraelectric was found to be associated with the covalency between the A-site ion and Ti or Zr. Furthermore, the energy for π-bonding between O2p and Ti3d (or Zr4d in AZrO3) shifted toward the lower energy level by substitution of the A site with Ca to give a lower relative permittivity. Then, we studied the effect of quantitative changes of the amount (x = 0.25, 0.5, 0.75) of A-site ions in the (Ba1-x, Srx)TiO3 system on the electronic structures, and suggested that the bonding nature between O and Ti is related to the relative permittivity of the system.

  20. Ferroelectric polymers for electrical energy storage

    NASA Astrophysics Data System (ADS)

    Claude, Jason W.

    The energy storage properties of vinylidene fluoride based fluoropolymers were explored. Energy density is a function of a materials permittivity and electrical breakdown strength. High values of each of these parameters are desirable for a high energy density and were explored in various fluoropolymer systems. Copolymers containing vinylidene fluoride (VDF), chlorofluoroethylene (CTFE), and trifluoroethylene (TrFE) were synthesized by a two-step approach beginning with the copolymerization of VDF and CTFE and the subsequent hydrogenation of the CTFE units to TrFE to create the terpolymer P(VDF-CTFE-TrFE). By changing the chemical composition of the fluoropolymers, the permittivity was varied from 12 to 50 due to changes in the crystal phase that converted the polymers from paraelectric to ferroelectric materials. The electrical breakdown mechanisms of a single copolymer composition of P(VDF-CTFE) was studied as a function of molecular weight and temperature. Energy density and breakdown strength increased as molecular weight increased and temperature decreased. An electromechanical breakdown mechanism was responsible for failure at 25°C while a thermal breakdown mechanism operated at -35°C which was below the glass transition of the material. In between at -15°C, a combination of the two mechanisms was found to operate. Electromechanical breakdown was also found to operate in a copolymer system with a fixed amount of VDF and varying amounts of TrFE and CTFE. The molecular weights were identical for all the polymers. Maxwell stress is the primary contributor to the electromechanical stress in polymers with a high amount the CTFE. Electrostrictive stress due to a crystal phase change at high electric fields is a major contributor to the electromechanical stress in polymers containing a high amount of TrFE. Energy density and electrical breakdown strength increased with increasing amounts of TrFE. Nanometer sized silica particles were incorporated into a P

  1. Piezoelectricity and ferroelectricity of cellular polypropylene electrets films characterized by piezoresponse force microscopy

    SciTech Connect

    Miao, Hongchen; Sun, Yao; Zhou, Xilong; Li, Yingwei; Li, Faxin

    2014-08-14

    Cellular electrets polymer is a new ferroelectret material exhibiting large piezoelectricity and has attracted considerable attentions in researches and industries. Property characterization is very important for this material and current investigations are mostly on macroscopic properties. In this work, we conduct nanoscale piezoelectric and ferroelectric characterizations of cellular polypropylene (PP) films using piezoresponse force microscopy (PFM). First, both the single-frequency PFM and dual-frequency resonance-tracking PFM testings were conducted on the cellular PP film. The localized piezoelectric constant d{sub 33} is estimated to be 7–11pC/N by correcting the resonance magnification with quality factor and it is about one order lower than the macroscopic value. Next, using the switching spectroscopy PFM (SS-PFM), we studied polarization switching behavior of the cellular PP films. Results show that it exhibits the typical ferroelectric-like phase hysteresis loops and butterfly-shaped amplitude loops, which is similar to that of a poly(vinylidene fluoride) (PVDF) ferroelectric polymer film. However, both the phase and amplitude loops of the PP film are intensively asymmetric, which is thought to be caused by the nonzero remnant polarization after poling. Then, the D-E hysteresis loops of both the cellular PP film and PVDF film were measured by using the same wave form as that used in the SS-PFM, and the results show significant differences. Finally, we suggest that the ferroelectric-like behavior of cellular electrets films should be distinguished from that of typical ferroelectrics, both macroscopically and microscopically.

  2. Piezoelectricity and ferroelectricity of cellular polypropylene electrets films characterized by piezoresponse force microscopy

    NASA Astrophysics Data System (ADS)

    Miao, Hongchen; Sun, Yao; Zhou, Xilong; Li, Yingwei; Li, Faxin

    2014-08-01

    Cellular electrets polymer is a new ferroelectret material exhibiting large piezoelectricity and has attracted considerable attentions in researches and industries. Property characterization is very important for this material and current investigations are mostly on macroscopic properties. In this work, we conduct nanoscale piezoelectric and ferroelectric characterizations of cellular polypropylene (PP) films using piezoresponse force microscopy (PFM). First, both the single-frequency PFM and dual-frequency resonance-tracking PFM testings were conducted on the cellular PP film. The localized piezoelectric constant d33 is estimated to be 7-11pC/N by correcting the resonance magnification with quality factor and it is about one order lower than the macroscopic value. Next, using the switching spectroscopy PFM (SS-PFM), we studied polarization switching behavior of the cellular PP films. Results show that it exhibits the typical ferroelectric-like phase hysteresis loops and butterfly-shaped amplitude loops, which is similar to that of a poly(vinylidene fluoride) (PVDF) ferroelectric polymer film. However, both the phase and amplitude loops of the PP film are intensively asymmetric, which is thought to be caused by the nonzero remnant polarization after poling. Then, the D-E hysteresis loops of both the cellular PP film and PVDF film were measured by using the same wave form as that used in the SS-PFM, and the results show significant differences. Finally, we suggest that the ferroelectric-like behavior of cellular electrets films should be distinguished from that of typical ferroelectrics, both macroscopically and microscopically.

  3. Three-dimensional H-bonding and ferroelectric transition in KDP. Quantum-chemical study

    NASA Astrophysics Data System (ADS)

    Dolin, S. P.; Mikhailova, T. Yu; Solin, M. V.; Breslavskaya, N. N.; Levin, A. A.

    On basis of the nonempirical methods (SCF, B3LYP, MP2-MP4) and several cluster models, the ferroelectric KH2PO4 (KDP) and its deuteroanalogue are studied. The tunneling integralsΩ and the parameters of the effective coupling of protons/deuterons U,V (the Ising parameters) are calculated for these materials with the 3d network of H/D-bonds. Using the obtained U,V andΩ values in the frames of molecular field approximation, it is found that the structural phase (ferroelectric) transition occurs for both crystals within the lowering of temperature. Such low-temperature behavior differs the 3d KDP-family materials from 0d systems, where the low-temperature phase transition takes place only upon deuteration. It is demonstrated that this difference is associated with an abrupt Ising parameters growth for KDP if compared with the nondeuterated 0d materials.

  4. Crystallographic, Ferroelectric and Electronic Properties of the Sr2ZrTiO6 Double Perovskite

    NASA Astrophysics Data System (ADS)

    Landínez Téllez, D. A.; Carrero Bermúdez, L. A.; Deluque Toro, C. E.; Cardona, R.; Roa-Rojas, J.

    2013-08-01

    In this paper, we report structural analysis, ferroelectric behavior and electronic structure of Sr2ZrTiO6 double perovskite. Samples were produced by the solid state reaction recipe. Crystallographic analysis was performed by Rietveld refinement of experimental X-ray diffraction patterns. Results show that this material crystallizes in a tetragonal perovskite structure which corresponds to the space group I4/m. The curve of polarization as a function of applied voltage evidences a ferroelectric character with saturation polarization on the application of voltages up to 1800 V. Calculations of density of states and band structure for this manganite-like material were carried out by means of the density functional theory implemented into the Wien2k code. Results of total and partial density of states reveal the insulator character of this material with an energy gap of 2.66 eV.

  5. Thermal Expansion Anomaly in TTB Ferroelectrics: The Interplay between Framework Structure and Electric Polarization.

    PubMed

    Lin, Kun; You, Li; Li, Qiang; Chen, Jun; Deng, Jinxia; Xing, Xianran

    2016-08-15

    Tetragonal tungsten bronze (TTB) makes up a large family of functional materials with fascinating dielectric, piezoelectric, or ferroelectric properties. Understanding the thermal expansion mechanisms associated with their physical properties is important for their practical applications as well as theoretical investigations. Fortunately, the appearance of anomalous thermal expansion in functional materials offers a chance to capture the physics behind them. Herein, we report an investigation of the thermal expansion anomalies in TTBs that are related to ferroelectric transitions and summarize recent progress in this field. The special role of Pb(2+) cation is elucidated. The interplay between the thermal expansion anomaly, electric polarization, and framework structure provides new insight into the structure-property relationships in functional materials.

  6. Deaging and Asymmetric Energy Landscapes in Electrically Biased Ferroelectrics

    SciTech Connect

    Tutuncu, Goknur; Damjanovic, Dragan; Chen, Jun; Jones, Jacob L.

    2015-09-01

    In ferroic materials, the dielectric, piezoelectric, magnetic, and elastic coefficients are significantly affected by the motion of domain walls. This motion can be described as the propagation of a wall across various types and strengths of pinning centers that collectively constitute a force profile or energetic landscape. Biased domain structures and asymmetric energy landscapes can be created through application of high fields (such as during electrical poling), and the material behavior in such states is often highly asymmetric. In some cases, this behavior can be considered as the electric analogue to the Bauschinger effect. The present Letter uses time-resolved, high-energy x-ray Bragg scattering to probe this asymmetry and the associated deaging effect in the ferroelectric morphotropic phase boundary composition 0.36BiScO{sub 3}-0.64PbTiO{sub 3}.

  7. Deaging and asymmetric energy landscapes in electrically biased ferroelectrics.

    PubMed

    Tutuncu, Goknur; Damjanovic, Dragan; Chen, Jun; Jones, Jacob L

    2012-04-27

    In ferroic materials, the dielectric, piezoelectric, magnetic, and elastic coefficients are significantly affected by the motion of domain walls. This motion can be described as the propagation of a wall across various types and strengths of pinning centers that collectively constitute a force profile or energetic landscape. Biased domain structures and asymmetric energy landscapes can be created through application of high fields (such as during electrical poling), and the material behavior in such states is often highly asymmetric. In some cases, this behavior can be considered as the electric analogue to the Bauschinger effect. The present Letter uses time-resolved, high-energy x-ray Bragg scattering to probe this asymmetry and the associated deaging effect in the ferroelectric morphotropic phase boundary composition 0.36BiScO3 - 0.64PbTiO3.

  8. A high performance triboelectric nanogenerator for self-powered non-volatile ferroelectric transistor memory.

    PubMed

    Fang, Huajing; Li, Qiang; He, Wenhui; Li, Jing; Xue, Qingtang; Xu, Chao; Zhang, Lijing; Ren, Tianling; Dong, Guifang; Chan, H L W; Dai, Jiyan; Yan, Qingfeng

    2015-11-07

    We demonstrate an integrated module of self-powered ferroelectric transistor memory based on the combination of a ferroelectric FET and a triboelectric nanogenerator (TENG). The novel TENG was made of a self-assembled polystyrene nanosphere array and a poly(vinylidene fluoride) porous film. Owing to this unique structure, it exhibits an outstanding performance with an output voltage as high as 220 V per cycle. Meanwhile, the arch-shaped TENG is shown to be able to pole a bulk ferroelectric 0.65Pb(Mg1/3Nb2/3)O3-0.35PbTiO3 (PMN-PT) single crystal directly. Based on this effect, a bottom gate ferroelectric FET was fabricated using pentacene as the channel material and a PMN-PT single crystal as the gate insulator. Systematic tests illustrate that the ON/OFF current ratio of this transistor memory element is approximately 10(3). More importantly, we demonstrate the feasibility to switch the polarization state of this FET gate insulator, namely the stored information, by finger tapping the TENG with a designed circuit. These results may open up a novel application of TENGs in the field of self-powered memory systems.

  9. Displacive-type ferroelectricity from magnetic correlations within spin-chain

    PubMed Central

    Basu, Tathamay; Kishore, V. V. Ravi; Gohil, Smita; Singh, Kiran; Mohapatra, N.; Bhattacharjee, S.; Gonde, Babu; Lalla, N. P.; Mahadevan, Priya; Ghosh, Shankar; Sampathkumaran, E. V.

    2014-01-01

    Observation of ferroelectricity among non-d0 systems, which was believed for a long time an unrealistic concept, led to various proposals for the mechanisms to explain the same (i.e. magnetically induced ferroelectricity) during last decade. Here, we provide support for ferroelectricity of a displacive-type possibly involving magnetic ions due to short-range magnetic correlations within a spin-chain, through the demonstration of magnetoelectric coupling in a Haldane spin-chain compound Er2BaNiO5 well above its Néel temperature of (TN = ) 32 K. There is a distinct evidence for electric polarization setting in near 60 K around which there is an evidence for short-range magnetic correlations from other experimental methods. Raman studies also establish a softening of phonon modes in the same temperature (T) range and T-dependent x-ray diffraction (XRD) patterns also reveal lattice parameters anomalies. Density-functional theory based calculations establish a displacive component (similar to d0-ness) as the root-cause of ferroelectricity from (magnetic) NiO6 chain, thereby offering a new route to search for similar materials near room temperature to enable applications. PMID:25005869

  10. Analysis of the Measurement and Modeling of a Digital Inverter Based on a Ferroelectric Transistor

    NASA Technical Reports Server (NTRS)

    MacLeod, Todd C.; Phillips, Thomas A.; Sayyah, Rana; Ho, Fat D.

    2009-01-01

    The use of ferroelectric materials for digital memory devices is widely researched and implemented, but ferroelectric devices also possess unique characteristics that make them have interesting and useful properties in digital circuits. Because ferroelectric transistors possess the properties of hysteresis and nonlinearity, a digital inverter containing a FeFET has very different characteristics than one with a traditional FET. This paper characterizes the properties of the measurement and modeling of a FeFET based digital inverter. The circuit was set up using discrete FeFETs. The purpose of this circuit was not to produce a practical integrated circuit that could be inserted directly into existing digital circuits, but to explore the properties and characteristics of such a device and to look at possible future uses. Input and output characteristics are presented, as well as timing measurements. Comparisons are made between the ferroelectric device and the properties of a standard digital inverter. Potential benefits and possible uses of such a device are presented.

  11. Characterizing new compositions of [001]C relaxor ferroelectric single crystals using a work-energy model

    NASA Astrophysics Data System (ADS)

    Gallagher, John A.

    2016-04-01

    The desired operating range of ferroelectric materials with compositions near the morphotropic phase boundary is limited by field induced phase transformations. In [001]C cut and poled relaxor ferroelectric single crystals the mechanically driven ferroelectric rhombohedral to ferroelectric orthorhombic phase transformation is hindered by antagonistic electrical loading. Instability around the phase transformation makes the current experimental technique for characterization of the large field behavior very time consuming. Characterization requires specialized equipment and involves an extensive set of measurements under combined electrical, mechanical, and thermal loads. In this work a mechanism-based model is combined with a more limited set of experiments to obtain the same results. The model utilizes a work-energy criterion that calculates the mechanical work required to induce the transformation and the required electrical work that is removed to reverse the transformation. This is done by defining energy barriers to the transformation. The results of the combined experiment and modeling approach are compared to the fully experimental approach and error is discussed. The model shows excellent predictive capability and is used to substantially reduce the total number of experiments required for characterization. This decreases the time and resources required for characterization of new compositions.

  12. Size Effect in Ferroelectric Long Cylinders

    NASA Astrophysics Data System (ADS)

    Wang, Yuguo; Zhang, Peilin; Wang, Chunlei; Zhong, Weilie; N, Napp; D, R. Tilly

    1995-02-01

    The Curie temperature and polarization in a ferroelectric cylinder with infinite length have been examined using Landau free energy expansion. The Curie temperature and polarization decrease with decreasing cylinder diameter for the positive extrapolation length, and reach zero at the critical size. For negative extrapolation length, both Curie temperature and polarization increase with decreasing cylinder diameter.

  13. Ferroelectric control of a Mott insulator

    PubMed Central

    Yamada, Hiroyuki; Marinova, Maya; Altuntas, Philippe; Crassous, Arnaud; Bégon-Lours, Laura; Fusil, Stéphane; Jacquet, Eric; Garcia, Vincent; Bouzehouane, Karim; Gloter, Alexandre; Villegas, Javier E.; Barthélémy, Agnès; Bibes, Manuel

    2013-01-01

    The electric field control of functional properties is an important goal in oxide-based electronics. To endow devices with memory, ferroelectric gating is interesting, but usually weak compared to volatile electrolyte gating. Here, we report a very large ferroelectric field-effect in perovskite heterostructures combining the Mott insulator CaMnO3 and the ferroelectric BiFeO3 in its “supertetragonal” phase. Upon polarization reversal of the BiFeO3 gate, the CaMnO3 channel resistance shows a fourfold variation around room temperature, and a tenfold change at ~200 K. This is accompanied by a carrier density modulation exceeding one order of magnitude. We have analyzed the results for various CaMnO3 thicknesses and explain them by the electrostatic doping of the CaMnO3 layer and the presence of a fixed dipole at the CaMnO3/BiFeO3 interface. Our results suggest the relevance of ferroelectric gates to control orbital- or spin-ordered phases, ubiquitous in Mott systems, and pave the way toward efficient Mott-tronics devices. PMID:24089020

  14. Ferroelectric Diodes with Charge Injection and Trapping

    NASA Astrophysics Data System (ADS)

    Fan, Zhen; Fan, Hua; Lu, Zengxing; Li, Peilian; Huang, Zhifeng; Tian, Guo; Yang, Lin; Yao, Junxiang; Chen, Chao; Chen, Deyang; Yan, Zhibo; Lu, Xubing; Gao, Xingsen; Liu, Jun-Ming

    2017-01-01

    Ferroelectric diodes with polarization-modulated Schottky barriers are promising for applications in resistive switching (RS) memories. However, they have not achieved satisfactory performance reliability as originally hoped. The physical origins underlying this issue have not been well studied, although they deserve much attention. Here, by means of scanning Kelvin probe microscopy we show that the electrical poling of ferroelectric diodes can cause significant charge injection and trapping besides polarization switching. We further show that the reproducibility and stability of switchable diode-type RS behavior are significantly affected by the interfacial traps. A theoretical model is then proposed to quantitatively describe the modifications of Schottky barriers by charge injection and trapping. This model is able to reproduce various types of hysteretic current-voltage characteristics as experimentally observed. It is further revealed that the charge injection and trapping can significantly modify the electroresistance ratio, RS polarity, and high- or low-resistance states initially defined by the polarization direction. Several approaches are suggested to suppress the effect of charge injection and trapping so as to realize high-performance polarization-reversal-induced RS. This study, therefore, reveals the microscopic mechanisms for the RS behavior comodulated by polarization reversal and charge trapping in ferroelectric diodes, and also provides useful suggestions for developing reliable ferroelectric RS memories.

  15. A Model for Ferroelectric Phase Shifters

    NASA Technical Reports Server (NTRS)

    Romanofsky, Robert R.; Qureshi, A. Haq

    2000-01-01

    Novel microwave phase shifters consisting of coupled microstrip lines on thin ferroelectric films have been demonstrated recently. A theoretical model useful for predicting the propagation characteristics (insertion phase shift, dielectric loss, impedance, and bandwidth) is presented here. The model is based on a variational solution for line capacitance and coupled strip transmission line theory.

  16. Room temperature p-type conductivity and coexistence of ferroelectric order in ferromagnetic Li doped ZnO nanoparticles

    SciTech Connect

    Awan, Saif Ullah E-mail: ullahphy@gmail.com; Hasanain, S. K.; Anjum, D. H.; Awan, M. S.; Shah, Saqlain A.

    2014-10-28

    Memory and switching devices acquired new materials which exhibit ferroelectric and ferromagnetic order simultaneously. We reported multiferroic behavior in Zn{sub 1−y}Li{sub y}O(0.00≤y≤0.10) nanoparticles. The analysis of transmission electron micrographs confirmed the hexagonal morphology and wurtzite crystalline structure. We investigated p-type conductivity in doped samples and measured hole carriers in range 2.4 × 10{sup 17}/cc to 7.3 × 10{sup 17}/cc for different Li contents. We found that hole carriers are responsible for long range order ferromagnetic coupling in Li doped samples. Room temperature ferroelectric hysteresis loops were observed in 8% and 10% Li doped samples. We demonstrated ferroelectric coercivity (remnant polarization) 2.5 kV/cm (0.11 μC/cm{sup 2}) and 2.8 kV/cm (0.15 μC/cm{sup 2}) for y = 0.08 and y = 0.10 samples. We propose that the mechanism of Li induced ferroelectricity in ZnO is due to indirect dipole interaction via hole carriers. We investigated that if the sample has hole carriers ≥5.3 × 10{sup 17}/cc, they can mediate the ferroelectricity. Ferroelectric and ferromagnetic measurements showed that higher electric polarization and larger magnetic moment is attained when the hole concentration is larger and vice versa. Our results confirmed the hole dependent coexistence of ferromagnetic and ferroelectric behavior at room temperature, which provide potential applications for switchable and memory devices.

  17. Interaction of Terahertz Radiation with Ferroelectrics

    NASA Astrophysics Data System (ADS)

    Nelson, Keith

    2007-03-01

    Ferroelectric crystals have long been used as acoustic transducers and receivers. An extensive toolset has been developed for MHz-frequency acoustic wave generation, control, guidance, and readout. In recent years, an analogous toolset has been developed for terahertz wave transduction and detection. Femtosecond optical pulses irradiate ferroelectric crystals to generate responses in the 0.1-5 THz frequency range that are admixtures of electromagnetic and polar lattice vibrational excitations called phonon-polaritons. Spatiotemporal femtosecond pulse shaping may be used to generate additional optical pulses that arrive at specified times and sample locations for control and manipulation of the THz waves. Femtosecond laser machining may be used for fabrication of waveguides, resonators, and other structures that are integrated into the ferroelectric host crystal. Finally, real-space imaging of the THz fields can be executed with variably delayed femtosecond probe pulses, permitting direct visualization of THz wave spatial and temporal evolution. This ``polaritonics'' toolset enables multiplexed generation of arbitrary THz waveforms and use of the waveforms within the ferroelectric host crystal or after projection into free space or an adjacent medium. The polaritonics platform will be reviewed and several new developments and applications will be presented. These include spectroscopy of relaxor ferroelectrics, whose temperature-dependent dielectric responses in the GHz-THz regime reveal complex polarization dynamics on well separated fast and slow time scales; direct measurement of phonon-polariton lattice vibrational displacements through femtosecond time-resolved x-ray diffraction; generation of high polariton field amplitudes and pulse energies; use of large-amplitude polariton waves to drive nonlinear lattice vibrational responses; and enhancement of optical-to-THz conversion efficiency through a pseudo-phase-matching approach that circumvents the very large

  18. Effects of the poling process on dielectric, piezoelectric, and ferroelectric properties of lead zirconate titanate

    NASA Astrophysics Data System (ADS)

    Prewitt, Anderson D.

    Smart materials are widely used in many of today's relevant technologies such as nano and micro electromechanical systems (NEMS and MEMS), sensors, actuators, nonvolatile memory, and solid state devices. Many of these systems rely heavily on the electromechanical properties of certain smart materials, such as piezoelectricity and ferroelectricity. By definition, piezoelectricity is a mechanical stress in a material that produces an electric displacement (known as the direct piezoelectric effect) or electrical charge in a material which produces a mechanical strain (known as the converse piezoelectric effect). Ferroelectricity is a sub-class of piezoelectricity in which the polarization occurs spontaneously and the dipoles can be reoriented. Domain walls are the nanoscale regions separating two finite distinctively polarized areas in a ferroelectric. The reorientation of polarization in a material is called the poling process and many factors can influence the effectiveness of this process. A more fundamental understanding of how electrical and mechanical loading changes the domain structure of these materials could lead to enhanced properties such as increased energy transduction and decreased nonlinear behavior. This research demonstrates the influence of mechanical pressure and electrical field during and after the poling process on domain walls. The effects of strong mechanical forces on large-scale domain switching and weak cyclic forces on small-scale domain wall motion are investigated to show how they affect the macroscopic behavior of these materials. Commercial lead zirconate titanate ceramics were studied under various poling conditions and the effect of domain wall motion on the piezoelectric, dielectric, and ferroelectric properties was investigated. Polarization and strain measurements from samples poled at specific conditions and converse piezoelectric coefficient and dielectric permittivity data was extracted and interpreted in the context of

  19. Ferroelectric BaTiO3 thin films on Ti substrate fabricated using pulsed-laser deposition.

    PubMed

    He, J; Jiang, J C; Liu, J; Collins, G; Chen, C L; Lin, B; Giurgiutiu, V; Guo, R Y; Bhalla, A; Meletis, E I

    2010-09-01

    We report on the fabrication of ferroelectric BaTiO3 thin films on titanium substrates using pulsed laser deposition and their microstructures and properties. Electron microscopy studies reveal that BaTiO3 films are composed of crystalline assemblage of nanopillars with average cross sections from 100 nm to 200 nm. The BaTiO3 films have good interface structures and strong adhesion with respect to Ti substrates by forming a rutile TiO2 intermediate layer with a gradient microstructure. The room temperature ferroelectric polarization measurements show that the as-deposited BTO films possess nearly the same spontaneous polarization as the bulk BTO ceramics indicating formation of ferroelectric domains in the films. Successful fabrication of such ferroelectric films on Ti has significant importance for the development of new applications such as structural health monitoring spanning from aerospace to civil infrastructure. The work can be extended to integrate other ferroelectric oxide films with various promising properties to monitor the structural health of materials.

  20. Switchable and Tunable Ferroelectric Bulk Acoustic Wave Resonators and Filters

    NASA Astrophysics Data System (ADS)

    Saddik, George Nabih

    Ferroelectric materials such as barium titanate (BaTiO 3 or BTO), strontium titanate (SrTiO3 or STO), and their solid solution barium strontium titanate (BaxSr1-xTiO 3 or BST) have been under investigation for over 50 years. BTO, STO, and BST are high-k dielectric materials, with a field dependent permittivity and a perovskite crystal structure. At room temperature BTO is a ferroelectric with a ferroelectric to paraelectric transition temperature of about 116°C (Curie temperature), while STO has no ferroelectric phase. The formation of a solid solution between BTO and STO allows for the engineering of the Curie temperature; the Curie temperature decreses as the mole ratio of barium decreases. Extensive research went into understanding the properties of BST and developing RF circuits such as tunable capacitors, tunable matching networks, tunable filters, phase shifters and harmonic generators. BST tunable capacitors have always had anomalous resonances in the one port scattering parameter measurements, although they are very small they degrade the quality factor of the device, and research went into reducing these resonances as much as possible. The goal of this thesis is to investigate these anomalous resonances and exploit them into RF devices and circuits. Careful investigation showed that these resonances were field induced piezoelectric resonance. Piezoelectric materials such as AlN, ZnO, and PZT are used in many applications, such as resonators, and filters. Thin film bulk acoustic wave resonators (FBAR) have been in use by research and industry since the early 1980s, and in high volume production for cell phone duplexers since early 2000s. FBAR filters and duplexers have several advantages over surface acoustic wave (SAW) and ceramic devices such as high quality factors necessary for sharp filter skirts, small size, high performance, and ease of integration. There are two approaches to designing bulk acoustic wave resonators. The first is an FBAR where a

  1. Study of ferroelectric characteristics of diisopropylammonium bromide films

    NASA Astrophysics Data System (ADS)

    Thirmal, C.; Biswas, P. P.; Shin, Y. J.; Noh, T. W.; Giridharan, N. V.; Venimadhav, A.; Murugavel, P.

    2016-09-01

    Organic molecular ferroelectrics are highly desirable due to their numerous advantages. In the present work, a thick film of diisopropylammonium bromide organic molecular ferroelectric is fabricated on the ITO/glass substrate. The grown film shows preferential orientation along the c-axis with a ferroelectric transition at 419 K. The piezoresponse force microscopic measurements are done in a dual ac resonance tracking mode for its switching characteristics. The amplitude and phase images of the oppositely written domain patterns exhibit a clear contrast with 180° phase difference. The dynamical spectroscopic studies reveal a butterfly loop in amplitude and hysteretic character of the phase which are the expected characteristics features of ferroelectrics. In addition, the macroscopic polarization versus electric field hysteresis gives an additional proof for ferroelectric character of the film with the maximum polarization of 3.5 μC/cm2. Overall, we have successfully fabricated diisopropylammonium bromide organic films and demonstrated its room temperature ferroelectric characteristics.

  2. Ferroelectric domain engineering by focused infrared femtosecond pulses

    SciTech Connect

    Chen, Xin; Shvedov, Vladlen; Sheng, Yan; Karpinski, Pawel; Koynov, Kaloian; Wang, Bingxia; Trull, Jose; Cojocaru, Crina; Krolikowski, Wieslaw

    2015-10-05

    We demonstrate infrared femtosecond laser-induced inversion of ferroelectric domains. This process can be realised solely by using tightly focused laser pulses without application of any electric field prior to, in conjunction with, or subsequent to the laser irradiation. As most ferroelectric crystals like LiNbO{sub 3}, LiTaO{sub 3}, and KTiOPO{sub 4} are transparent in the infrared, this optical poling method allows one to form ferroelectric domain patterns much deeper inside a ferroelectric crystal than by using ultraviolet light and hence can be used to fabricate practical devices. We also propose in situ diagnostics of the ferroelectric domain inversion process by monitoring the Čerenkov second harmonic signal, which is sensitive to the appearance of ferroelectric domain walls.

  3. Optical Temperature Sensor Through Upconversion Emission from the Er3+ Doped SrBi8Ti7O27 Ferroelectrics

    NASA Astrophysics Data System (ADS)

    Zou, Hua; Wang, Xusheng; Hu, Yifeng; Zhu, Xiaoqing; Sui, Yongxing; Song, Zhitang

    2016-06-01

    Er doped SrBi8Ti7O27 (SBT) ferroelectric ceramics were prepared by a solid-state reaction technique. By Er doping, the intensive green upconversion emissions were recorded under 980 nm diode laser excitation with 20 mW. The fluorescence spectrum was investigated in the temperature range of 150-580 K. By the fluorescence intensity ratio technique, the green emission band was studied as a function of temperature with a maximum sensing sensitivity of 0.0028 at 510 K. These results indicate that the Er doped SBT ferroelectric ceramics are promising multifunctional sensing materials.

  4. Integrated ferroelectric stacked MIM capacitors with 100 nF/mm(2) and 90 V breakdown as replacement for discretes.

    PubMed

    Roest, Aarnoud; Mauczok, Rüdiger; Reimann, Klaus; van Leuken-Peters, Linda; Klee, Mareike

    2009-03-01

    This paper shows for the first time integrated thin film ferroelectric metal-insulator-metal capacitors on silicon with a record high capacitance density above 100 nF/mm(2) combined with a breakdown voltage of 90 V and a lifetime exceeding 10 years at 85 degrees C and 5 V. The high capacitance density was obtained by a combination of material optimizations resulting in a dielectric constant of 1600, and stacking of capacitors. The reliability of these ferroelectric capacitors was studied in detail with accelerated lifetime testing. The high performance of the integrated capacitors in this paper shows great potential for applications demanding high capacitance densities combined with electrostatic discharge protection.

  5. Ferromagnetism induced by entangled charge and orbital orderings in ferroelectric titanate perovskites

    PubMed Central

    Bristowe, N. C.; Varignon, J.; Fontaine, D.; Bousquet, E.; Ghosez, Ph.

    2015-01-01

    In magnetic materials, the Pauli exclusion principle typically drives anti-alignment between electron spins on neighbouring species resulting in antiferromagnetic behaviour. Ferromagnetism exhibiting spontaneous spin alignment is a fairly rare behaviour, but once materialized is often associated with itinerant electrons in metals. Here we predict and rationalize robust ferromagnetism in an insulating oxide perovskite structure based on the popular titanate series. In half-doped layered titanates, the combination of Jahn–Teller and oxygen breathing motions opens a band gap and creates an unusual charge and orbital ordering of the Ti d electrons. It is argued that this intriguingly intricate electronic network favours the elusive inter-site ferromagnetic (FM) ordering, on the basis of intra-site Hund's rules. Finally, we find that the layered oxides are also ferroelectric with a spontaneous polarization approaching that of BaTiO3. The concepts are general and design principles of the technologically desirable FM ferroelectric multiferroics are presented. PMID:25807180

  6. High-performance black phosphorus top-gate ferroelectric transistor for nonvolatile memory applications

    NASA Astrophysics Data System (ADS)

    Lee, Young Tack; Hwang, Do Kyung; Choi, Won Kook

    2016-10-01

    Two-dimensional (2D) van der Waals (vdW) atomic crystals have been extensively studied and significant progress has been made. The newest 2D vdW material, called black phosphorus (BP), has attracted considerable attention due to its unique physical properties, such as its being a singlecomponent material like graphene, and its having a high mobility and direct band gap. Here, we report on a high-performance BP nanosheet based ferroelectric field effect transistor (FeFET) with a poly(vinylidenefluoride-trifluoroethylene) top-gate insulator for a nonvolatile memory application. The BP FeFETs show the highest linear hole mobility of 563 cm2/Vs and a clear memory window of more than 15 V. For more advanced nonvolatile memory circuit applications, two different types of resistive-load and complementary ferroelectric memory inverters were implemented, which showed distinct memory on/off switching characteristics.

  7. Fast 704 MHz Ferroelectric Tuner for Superconducting Cavities

    SciTech Connect

    Jay L. Hirshfield

    2012-04-12

    with narrower bandwidth. It is planned to build a 704 MHz version of the tuner, to check its underlying principles, and to make high-power tests at power densities aimed towards controlling 50 kW of average power. Steps towards this goal will be limited by, among other factors, losses in the actual ferroelectric elements in the ferroelectric assemblies. As the ferroelectric material loss tangent is reduced through efforts by the supplier Euclid TechLabs LLC, the concomitant power loss in its ferroelectric assemblies will drop, and the average power-handling capability of the Omega-P tuner will rise. It can thus be anticipated that the Phase II development project of the 704 MHz tuner will be iterative, but the pace and ultimate power-handling level of the tuner is difficult to predict at this early stage in Euclid's development program. Fortunately, since Omega-P's conceptual tuner is a simple module (nominally rated for 5 kW), so that the number of modules required in each tuner can be chosen, depending upon the cavity power level needed, plus the power for tuner losses.

  8. Observation of a periodic array of flux-closure quadrants in strained ferroelectric PbTiO3 films

    DOE PAGES

    Tang, Y. L.; Zhu, Y. L; Ma, Xiuliang; ...

    2015-05-01

    Nanoscale ferroelectrics are expected to exhibit various exotic domain configurations, such as the full flux-closure pattern that is well known in ferromagnetic materials. Here we observe not only the atomic morphology of the flux-closure quadrant but also a periodic array of flux closures in ferroelectric PbTiO3 films, mediated by tensile strain on a GdScO3 substrate. Using aberration-corrected scanning transmission electron microscopy, we directly visualize an alternating array of clockwise and counterclockwise flux closures, whose periodicity depends on the PbTiO3 film thickness. In the vicinity of the core, the strain is sufficient to rupture the lattice, with strain gradients up tomore » 109 per meter. We found engineering strain at the nanoscale may facilitate the development of nanoscale ferroelectric devices.« less

  9. Modified Johnson model for ferroelectric lead lanthanum zirconate titanate at very high fields and below Curie temperature.

    SciTech Connect

    Narayanan, M.; Tong, S.; Ma, B.; Liu, S.; Balachandran, U.

    2012-01-01

    A modified Johnson model is proposed to describe the nonlinear field dependence of the dielectric constant ({var_epsilon}-E loop) in ferroelectric materials below the Curie temperature. This model describes the characteristic ferroelectric 'butterfly' shape observed in typical {var_epsilon}-E loops. The predicted nonlinear behavior agreed well with the measured values in both the low- and high-field regions for lead lanthanum zirconate titanate films. The proposed model was also validated at different temperatures below the ferroelectric-to-paraelectric Curie point. The anharmonic coefficient in the model decreased from 6.142 x 10{sup -19} cm{sup 2}/V{sup 2} to 2.039 x 10{sup -19} cm{sup 2}/V{sup 2} when the temperature increased from 25 C to 250 C.

  10. Recent Advances in Electromechanical Imaging on the Nanometer Scale: Polarization Dynamics in Ferroelectrics, Biopolymers, and Liquid Imaging

    NASA Astrophysics Data System (ADS)

    Kalinin, Sergei V.; Jesse, Stephen; Rodriguez, Brian J.; Seal, Katyayani; Baddorf, Arthur P.; Zhao, Tong; Chu, Y. H.; Ramesh, Ramamoorthy; Eliseev, Eugene A.; Morozovska, Anna N.; Mirman, B.; Karapetian, Edgar

    2007-09-01

    Coupling between electrical and mechanical phenomena is ubiquitous in nature, with examples ranging from piezoelectricity in polar perovskites and chemical bonds to complex pathways of electromechanical transformations underpinning the functionality of electromotor proteins, cells, and tissues. Piezoresponse force microscopy (PFM) had originally emerged as a technique to study electromechanical phenomena in ferroelectric perovskites on the nanoscale. In recent years, the applicability of PFM for studying a broad range of non-ferroelectric polar materials has been demonstrated, necessitating further development of the technique, including theory of the image formation mechanism as well as probe and controller development. Here, we review the basic principles of PFM and summarize some of the recent advances, including switching spectroscopy, mapping of polarization dynamics in ferroelectric and multiferroic nanostructures, imaging of biopolymers in calcified and connective tissues and PFM in liquid environments.

  11. Fabrication of Glassy and Crystalline Ferroelectric Oxide by Containerless Processing

    NASA Astrophysics Data System (ADS)

    Yoda, Shinichi

    1. Instruction Much effort has been devoted to forming bulk glass from the melt of ferroelectric crystalline materials without adding any network-forming oxides such as SiO2 due to the potential for producing transparent glass ceramics with high dielectric constant and enhanced piezoelectric, pyroelectric and electro-optic effects. However, they require a higher cooling rate than glass formed by conventional techniques. Therefore, only amorphous thin-films have been formed, using rapid quenching with a cooling rate >105 K/s. The containerless processing is an attractive synthesis technique as it can prevent melt contamination, minimize heterogeneous nucleation, and allow melt to achieve deep undercooling for forming metastable phase and glassy material. Recently a new ferroelectric materiel, monoclinic BaTi2 O5 , with Currie temperature as 747 K was reported. In this study, we fabricated a bulk BaTi2 O5 glass from melt using containerless processing to study the phase relations and ferroelectric properties of BaTi2 O5 . To our knowledge, this was the first time that a bulk glass of ferroelectric material was fabricated from melt without adding any network-forming oxide. 2. Experiments BaTi2 O5 sphere glass with 2mm diameter was fabricated using containerless processing in an Aerodynamic Levitation Furnace (ALF). The containerless processing allowed the melt to achieve deep undercooling for glass forming. High purity commercial BaTiO3 and TiO2 powders were mixed with a mole ratio of 1:1 and compressed into rods and then sintered at 1427 K for 10 h. Bulk samples with a mass of about 20 mg were cut from the rod, levitated with the ALF, and then melted by a CO2 laser beam. After quenching with a cooling rate of about 1000 K/s, 2 mm diameter sphere glass could be obtained. To analyze the glass structure, a high-energy x-ray diffraction experiment was performed using an incident photon energy of 113.5 keV at the high-energy x-ray diffraction beamline BL04B2 of SPring-8

  12. Improved Properties of Pb Based BLZT Ferroelectric Ceramics

    SciTech Connect

    Kumar, Parveen; Singh, Sangeeta; Juneja, J. K.; Raina, K. K.; Prakash, Chandra

    2011-11-22

    Present report is concerning with investigation of effect of different sintering profiles on Pb based BLZT ceramics. The material powder of selected composition (Ba{sub 0.795}La{sub 0.005}Pb{sub 0.20}Ti{sub 0.90}Zr{sub 0.10}O{sub 3}) was prepared by solid state reaction route and then powder was compacted in the form of circular discs. The discs were then sintered at different temperatures (1325 deg. C for 4h, 1325 deg. C for 15min+1200 deg. C for 4h). Improved dielectric and ferroelectric properties were observed for samples sintered at 1200 deg. C. Shifting in T{sub c} to higher temperature could be related to enhanced tetragonality, which was further confirmed by X-ray diffraction analysis. All these improvements evidences that there is less Pb loss in case of modified sintering profile.

  13. High resolution field effect sensing of ferroelectric charges.

    SciTech Connect

    Ko, H.; Ryu, K.; Park, H.; Park, C.; Jeon, D.; Kim, Y. K.; Jung, J.; Min, D.-K.; Kim, Y.; Lee, H. N.; Park, Y.; Shin, H.; Hong, S.

    2011-03-04

    Nanoscale manipulation of surface charges and their imaging are essential for understanding local electronic behaviors of polar materials and advanced electronic devices. Electrostatic force microscopy and Kelvin probe force microscopy have been extensively used to probe and image local surface charges responsible for electrodynamics and transport phenomena. However, they rely on the weak electric force modulation of cantilever that limits both spatial and temporal resolutions. Here we present a field effect transistor embedded probe that can directly image surface charges on a length scale of 25 nm and a time scale of less than 125 {micro}s. On the basis of the calculation of net surface charges in a 25 nm diameter ferroelectric domain, we could estimate the charge density resolution to be as low as 0.08 {micro}C/cm{sup 2}, which is equivalent to 1/20 electron per nanometer square at room temperature.

  14. High-Resolution Field Effect Sensing of Ferroelectric Charges

    SciTech Connect

    Ko, Hyoungsoo; Ryu, Kyunghee; Park, Hongsik; Park, Chulmin; Jeon, Daeyoung; Kim, Yong Kwan; Jung, Juhwan; Min, Dong-Ki; Kim, Yunseok; Lee, Ho Nyung; Park, Yoondong; Shin, Hyunjung; Hong, Seungbum

    2011-01-01

    Nanoscale manipulation of surface charges and their imaging are essential for understanding local electronic behaviors of polar materials and advanced electronic devices. Electrostatic force microscopy and Kelvin probe force microscopy have been extensively used to probe and image local surface charges responsible for electrodynamics and transport phenomena. However, they rely on the weak electric force modulation of cantilever that limits both spatial and temporal resolutions. Here we present a field effect transistor embedded probe that can directly image surface charges on a length scale of 25 nm and a time scale of less than 125 {micro}s. On the basis of the calculation of net surface charges in a 25 nm diameter ferroelectric domain, we could estimate the charge density resolution to be as low as 0.08 {micro}C/cm{sup 2}, which is equivalent to 1/20 electron per nanometer square at room temperature.

  15. A ferroelectric model for the low emissivity highlands on Venus

    NASA Astrophysics Data System (ADS)

    Shepard, M. K.; Arvidson, R. E.; Brackett, R. A.; Fegley, B.

    1994-03-01

    A model to explain the low emissivity venusian highlands is proposed utilizing the temperature-dependent dielectric constant of ferroelectric minerals. Ferroelectric minerals are known to occur in alkaline and carbonite rocks, both of which are plausible for Venus. Ferroelectric minerals possess extremely high dielectric constants (105) over small temperature intervals and are only required in minor (much less than 1%) abundances to explain the observed emissivities. The ferroelectric model can account for: (1) the observed reduction in emissivity with increased altitude, (2) the abrupt return to normal emissivities at highest elevations, and (3) the variations in the critical elevation observed from region to region.

  16. One‐Dimensional Ferroelectric Nanostructures: Synthesis, Properties, and Applications

    PubMed Central

    Liang, Longyue; Kang, Xueliang

    2016-01-01

    One‐dimensional (1D) ferroelectric nanostructures, such as nanowires, nanorods, nanotubes, nanobelts, and nanofibers, have been studied with increasing intensity in recent years. Because of their excellent ferroelectric, ferroelastic, pyroelectric, piezoelectric, inverse piezoelectric, ferroelectric‐photovoltaic (FE‐PV), and other unique physical properties, 1D ferroelectric nanostructures have been widely used in energy‐harvesting devices, nonvolatile random access memory applications, nanoelectromechanical systems, advanced sensors, FE‐PV devices, and photocatalysis mechanisms. This review summarizes the current state of 1D ferroelectric nanostructures and provides an overview of the synthesis methods, properties, and practical applications of 1D nanostructures. Finally, the prospects for future investigations are outlined. PMID:27812477

  17. Piezoelectric and electrostrictive materials for transducers applications, volume 4

    NASA Astrophysics Data System (ADS)

    Cross, L. E.; Newnham, R. E.; Bhalla, A. S.; Dougherty, J. P.; Adair, J. H.; Varadan, V. K.; Varadan, V. V.

    1992-01-01

    The topics discussed are as follows: A Study of Y1Ba2Cu3O(7-x) Thick Films on Ferroelectric Substrates; Y1Ba2Cu30(7-x) as an Electrode Material for Ferroelectric Devices; Polarization Reversal and High Dielectric Permittivity in Lead Magnesium Niobate Titanate Thin Films; Ferroelectric Switching in Lead Zirconate-Lead Zinc Niobate Thin Films; Lead Zirconate Titanate Stannate Thin Films for Large Strian Microactuator Applications; Ferroelectric Thin Film Ultrasonic Micromotors; and Piezoelectric Micromotors for Microrobots.

  18. Ferroelectric, pyroelectric, and piezoelectric properties of a photovoltaic perovskite oxide

    NASA Astrophysics Data System (ADS)

    Bai, Yang; Siponkoski, Tuomo; Peräntie, Jani; Jantunen, Heli; Juuti, Jari

    2017-02-01

    A perovskite solid-solution, (1-x)KNbO3-xBaNi1/2Nb1/2O3-δ (KBNNO), has been found to exhibit tunable bandgaps in the visible light energy range, making it suitable for light absorption and conversion applications, e.g., solar energy harvesting and light sensing. Such a common ABO3-type perovskite structure, most widely used for ferroelectrics and piezoelectrics, enables the same solid-solution material to be used for the simultaneous harvesting or sensing of solar, kinetic, and thermal energies. In this letter, the ferroelectric, pyroelectric, and piezoelectric properties of KBNNO with x = 0.1 have been reported above room temperature. The investigation has also identified the optimal bandgap for visible light absorption. The stoichiometric composition and also a composition with potassium deficiency have been investigated, where the latter has shown more balanced properties. As a result, a remanent polarization of 3.4 μC/cm2, a pyroelectric coefficient of 26 μC/m2 K, piezoelectric coefficients d33 ≈ 23 pC/N and g33 ≈ 4.1 × 10-3 Vm/N, and a direct bandgap of 1.48 eV have been measured for the KBNNO ceramics. These results are considered to be a significant improvement compared to those of other compositions (e.g., ZnO and AlN), which could be used for the same applications. The results pave the way for the development of hybrid energy harvesters/sensors, which can convert multiple energy sources into electrical energy simultaneously in the same material.

  19. Ferroelectricity, Antiferroelectricity and Ultrathin 2D Electron/Hole Gas in Multifunctional Monolayer MXene.

    PubMed

    Chandrasekaran, Anand; Mishra, Avanish; Singh, Abhishek Kumar

    2017-04-04

    Presence of ferroelectric polarization in 2D materials is extremely rare due to the effect of the surface depolarizing field. Here, we use first-principles calculations to show the largest out-of-plane polarization observed in a monolayer in functionalized MXenes (Sc2CO2). The switching of polarization in this new class of ferroelectric materials occurs through an previously unknown intermediate antiferroelectric structure thus establishing three states for applications in low-dimensional non-volatile memory. We show that the armchair domain-interface acts as an 1D metallic nanowire separating two insulating domains. In the case of the van-der-Waals bilayer we observe, interestingly, the presence of an ultrathin 2D electron/hole gas (2DEG) on the top/bottom layers, respectively, due to the redistrubution of charge carriers. The 2DEG is non-degenerate due to spin-orbit-coupling, thus paving the way for spin-orbitronic devices. The coexistence of ferroelectricity, antiferroelectricity, 2DEG and spin-orbit splitting in this system suggests that such 2D polar materials possess high potential for device application in a multitude of fields ranging from nanoelectronics to photovoltaics.

  20. Removing pinhole shorts during large scale ferroelectric switching through ionic liquid interfaces

    NASA Astrophysics Data System (ADS)

    Wong, Anthony; Herklotz, Andreas; Wisinger, Nina; Rack, Philip; Ward, Thomas

    Ferroelectrics are a classification of materials that spontaneously polarize, accumulating charge at interfaces, and have non-linear hysteretic polarization curves. Switching fields required for ferroelectric materials are often very high, requiring thin insulating layers and high applied voltages. This commonly leads to electric pinholes and limits the areal sizes that can be polarized at a time. Ionic liquids have recently received heavy interest for the formation of electronic double layers which lead to huge electric fields at interfacial regions with low applied biases, and without the thickness constraint associated with conventional capacitors. We will show recent results which demonstrate that ionic liquid gating may offer the ideal solution to switch large regions of a ferroelectric film without limitations associated with pinhole defects. This has great importance to practical applications and fundamental interface studies that require large sample regions to be uniformly polarized. Supported by the US DOE Office of Basic Energy Sciences, Materials Sciences and Engineering Division and under US DOE Grant DE-SC0002136.

  1. Glucose Suppresses Biological Ferroelectricity in Aortic Elastin

    NASA Astrophysics Data System (ADS)

    Liu, Yuanming; Wang, Yunjie; Chow, Ming-Jay; Chen, Nataly Q.; Ma, Feiyue; Zhang, Yanhang; Li, Jiangyu

    2013-04-01

    Elastin is an intriguing extracellular matrix protein present in all connective tissues of vertebrates, rendering essential elasticity to connective tissues subjected to repeated physiological stresses. Using piezoresponse force microscopy, we show that the polarity of aortic elastin is switchable by an electrical field, which may be associated with the recently discovered biological ferroelectricity in the aorta. More interestingly, it is discovered that the switching in aortic elastin is largely suppressed by glucose treatment, which appears to freeze the internal asymmetric polar structures of elastin, making it much harder to switch, or suppressing the switching completely. Such loss of ferroelectricity could have important physiological and pathological implications from aging to arteriosclerosis that are closely related to glycation of elastin.

  2. Block copolymer/ferroelectric nanoparticle nanocomposites

    NASA Astrophysics Data System (ADS)

    Pang, Xinchang; He, Yanjie; Jiang, Beibei; Iocozzia, James; Zhao, Lei; Guo, Hanzheng; Liu, Jin; Akinc, Mufit; Bowler, Nicola; Tan, Xiaoli; Lin, Zhiqun

    2013-08-01

    Nanocomposites composed of diblock copolymer/ferroelectric nanoparticles were formed by selectively constraining ferroelectric nanoparticles (NPs) within diblock copolymer nanodomains via judicious surface modification of ferroelectric NPs. Ferroelectric barium titanate (BaTiO3) NPs with different sizes that are permanently capped with polystyrene chains (i.e., PS-functionalized BaTiO3NPs) were first synthesized by exploiting amphiphilic unimolecular star-like poly(acrylic acid)-block-polystyrene (PAA-b-PS) diblock copolymers as nanoreactors. Subsequently, PS-functionalized BaTiO3 NPs were preferentially sequestered within PS nanocylinders in the linear cylinder-forming polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) diblock copolymer upon mixing the BaTiO3 NPs with PS-b-PMMA. The use of PS-b-PMMA diblock copolymers, rather than traditional homopolymers, offers the opportunity for controlling the spatial organization of PS-functionalized BaTiO3 NPs in the PS-b-PMMA/BaTiO3 NP nanocomposites. Selective solvent vapor annealing was utilized to control the nanodomain orientation in the nanocomposites. Vertically oriented PS nanocylinders containing PS-functionalized BaTiO3 NPs were yielded after exposing the PS-b-PMMA/BaTiO3 NP nanocomposite thin film to acetone vapor, which is a selective solvent for PMMA block. The dielectric properties of nanocomposites in the microwave frequency range were investigated. The molecular weight of PS-b-PMMA and the size of BaTiO3 NPs were found to exert an apparent influence on the dielectric properties of the resulting nanocomposites.Nanocomposites composed of diblock copolymer/ferroelectric nanoparticles were formed by selectively constraining ferroelectric nanoparticles (NPs) within diblock copolymer nanodomains via judicious surface modification of ferroelectric NPs. Ferroelectric barium titanate (BaTiO3) NPs with different sizes that are permanently capped with polystyrene chains (i.e., PS-functionalized BaTiO3NPs) were

  3. Super-crystals in composite ferroelectrics

    PubMed Central

    Pierangeli, D.; Ferraro, M.; Di Mei, F.; Di Domenico, G.; de Oliveira, C. E. M.; Agranat, A. J.; DelRe, E.

    2016-01-01

    As atoms and molecules condense to form solids, a crystalline state can emerge with its highly ordered geometry and subnanometric lattice constant. In some physical systems, such as ferroelectric perovskites, a perfect crystalline structure forms even when the condensing substances are non-stoichiometric. The resulting solids have compositional disorder and complex macroscopic properties, such as giant susceptibilities and non-ergodicity. Here, we observe the spontaneous formation of a cubic structure in composite ferroelectric potassium–lithium–tantalate–niobate with micrometric lattice constant, 104 times larger than that of the underlying perovskite lattice. The 3D effect is observed in specifically designed samples in which the substitutional mixture varies periodically along one specific crystal axis. Laser propagation indicates a coherent polarization super-crystal that produces an optical X-ray diffractometry, an ordered mesoscopic state of matter with important implications for critical phenomena and applications in miniaturized 3D optical technologies. PMID:26907725

  4. Domain switching of fatigued ferroelectric thin films

    SciTech Connect

    Tak Lim, Yun; Yeog Son, Jong E-mail: hoponpop@ulsan.ac.kr; Shin, Young-Han E-mail: hoponpop@ulsan.ac.kr

    2014-05-12

    We investigate the domain wall speed of a ferroelectric PbZr{sub 0.48}Ti{sub 0.52}O{sub 3} (PZT) thin film using an atomic force microscope incorporated with a mercury-probe system to control the degree of electrical fatigue. The depolarization field in the PZT thin film decreases with increasing the degree of electrical fatigue. We find that the wide-range activation field previously reported in ferroelectric domains result from the change of the depolarization field caused by the electrical fatigue. Domain wall speed exhibits universal behavior to the effective electric field (defined by an applied electric field minus the depolarization field), regardless of the degree of the electrical fatigue.

  5. A Ferroelectric Oxide Made Directly on Silicon

    DTIC Science & Technology

    2009-04-17

    Issues of Complex, Epitaxial Oxide Growth and Integration with Silicon by Molecular Beam Epitaxy (Pennsylvania State University, University Park, 2002...Ferroelectric Oxide Made Directly on Silicon Maitri P. Warusawithana,1 Cheng Cen,2 Charles R. Sleasman,2 Joseph C. Woicik,3 Yulan Li,4 Lena Fitting...Schlom1* Metal oxide semiconductor field-effect transistors, formed using silicon dioxide and silicon, have undergone four decades of staggering

  6. Barkhausen noise in a relaxor ferroelectric.

    PubMed

    Colla, Eugene V; Chao, Lambert K; Weissman, M B

    2002-01-07

    Barkhausen noise, including both periodic and aperiodic components, is found in and near the relaxor regime of a familiar relaxor ferroelectric, PbMg(1/3)Nb(2/3)O3, driven by a periodic electric field. The temperature dependences of both the amplitude and spectral form show that the size of the coherent changes in the dipole moment shrink as the relaxor regime is entered, contrary to expectations based on some simple models.

  7. Block copolymer/ferroelectric nanoparticle nanocomposites.

    PubMed

    Pang, Xinchang; He, Yanjie; Jiang, Beibei; Iocozzia, James; Zhao, Lei; Guo, Hanzheng; Liu, Jin; Akinc, Mufit; Bowler, Nicola; Tan, Xiaoli; Lin, Zhiqun

    2013-09-21

    Nanocomposites composed of diblock copolymer/ferroelectric nanoparticles were formed by selectively constraining ferroelectric nanoparticles (NPs) within diblock copolymer nanodomains via judicious surface modification of ferroelectric NPs. Ferroelectric barium titanate (BaTiO3) NPs with different sizes that are permanently capped with polystyrene chains (i.e., PS-functionalized BaTiO3NPs) were first synthesized by exploiting amphiphilic unimolecular star-like poly(acrylic acid)-block-polystyrene (PAA-b-PS) diblock copolymers as nanoreactors. Subsequently, PS-functionalized BaTiO3 NPs were preferentially sequestered within PS nanocylinders in the linear cylinder-forming polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) diblock copolymer upon mixing the BaTiO3 NPs with PS-b-PMMA. The use of PS-b-PMMA diblock copolymers, rather than traditional homopolymers, offers the opportunity for controlling the spatial organization of PS-functionalized BaTiO3 NPs in the PS-b-PMMA/BaTiO3 NP nanocomposites. Selective solvent vapor annealing was utilized to control the nanodomain orientation in the nanocomposites. Vertically oriented PS nanocylinders containing PS-functionalized BaTiO3 NPs were yielded after exposing the PS-b-PMMA/BaTiO3 NP nanocomposite thin film to acetone vapor, which is a selective solvent for PMMA block. The dielectric properties of nanocomposites in the microwave frequency range were investigated. The molecular weight of PS-b-PMMA and the size of BaTiO3 NPs were found to exert an apparent influence on the dielectric properties of the resulting nanocomposites.

  8. Flat panel ferroelectric electron emission display system

    DOEpatents

    Sampayan, Stephen E.; Orvis, William J.; Caporaso, George J.; Wieskamp, Ted F.

    1996-01-01

    A device which can produce a bright, raster scanned or non-raster scanned image from a flat panel. Unlike many flat panel technologies, this device does not require ambient light or auxiliary illumination for viewing the image. Rather, this device relies on electrons emitted from a ferroelectric emitter impinging on a phosphor. This device takes advantage of a new electron emitter technology which emits electrons with significant kinetic energy and beam current density.

  9. Electrically induced mechanical precompression of ferroelectric plates

    DOEpatents

    Chen, P.J.

    1987-03-02

    A method of electrically inducing mechanical precompression of ferroelectric plate covered with electrodes utilizes the change in strains of the plate as functions of applied electric field. A first field polarizes and laterally shrinks the entire plate. An outer portion of the electrodes are removed, and an opposite field partially depolarizes and expands the central portion of the plate against the shrunk outer portion. 2 figs.

  10. Flat panel ferroelectric electron emission display system

    DOEpatents

    Sampayan, S.E.; Orvis, W.J.; Caporaso, G.J.; Wieskamp, T.F.

    1996-04-16

    A device is disclosed which can produce a bright, raster scanned or non-raster scanned image from a flat panel. Unlike many flat panel technologies, this device does not require ambient light or auxiliary illumination for viewing the image. Rather, this device relies on electrons emitted from a ferroelectric emitter impinging on a phosphor. This device takes advantage of a new electron emitter technology which emits electrons with significant kinetic energy and beam current density. 6 figs.

  11. Electrically induced mechanical precompression of ferroelectric plates

    DOEpatents

    Chen, Peter J.

    1987-01-01

    A method of electrically inducing mechanical precompression of a ferroelectric plate covered with electrodes utilizes the change in strains of the plate as functions of applied electric field. A first field polarizes and laterally shrinks the entire plate. An outer portion of the electrodes are removed, and an opposite field partially depolarizes and expands the central portion of the plate against the shrunk outer portion.

  12. Development of "fragility" in relaxor ferroelectrics

    NASA Astrophysics Data System (ADS)

    Wang, Yi-zhen; Chen, Lan; Wang, Hai-yan; Frank Zhang, X.; Fu, Jun; Xiong, Xiao-min; Zhang, Jin-xiu

    2014-02-01

    Relaxor ferroelectrics (RFs), a special class of the disordered crystals or ceramics, exhibit a pronounced slowdown of their dynamics upon cooling as glass-forming liquids, called the "Super-Arrhenius (SA)" relaxation. Despite great progress in glass-forming liquids, the "fragility" property of the SA relaxation in RFs remains unclear so far. By measuring the temperature-dependent dielectric relaxation in the typical relaxor Pb(Mg1/3Nb2/3)O3-x%PbTiO3 (PMN - x%PT) with 0 ≤ x ≤ 20.0, we in-depth study the "fragility" properties of the SA relaxation in PMN - x%PT. Such fascinating issues as the mechanism of the "fragility" at an atomic scale, the roles of the systematic configurational entropy change and interaction among relaxing units (RUs, including polar nanoregions and free dipoles) and the relation between "fragility" and ferroelectric order are investigated. Our results show that both the "fragility" of the temperature-dependent SA relaxation and ferroelectric order in the PMN - x%PT systems investigated arise thermodynamically from the configurational-entropy loss due to the attractive interaction among RUs, and develops as a power law, possibly diverging at the finite critical temperature Tc. A reasonable physical scenario, based on our "configurational-entropy-loss" theory and Nowick's "stress-induced-ordering" theory, was proposed.

  13. WFL: Microwave Applications of Thin Ferroelectric Films

    NASA Technical Reports Server (NTRS)

    Romanofsky, Robert

    2013-01-01

    We have developed a family of tunable microwave circuits, operating from X- through Ka-band, based on laser ablated BaxSr1-xTiO films on lanthanum aluminate and magnesium oxide substrates. Circuits include voltage controlled oscillators, filters, phase shifters and antennas. A review of the basic theory of operation of these devices will be presented along with measured performance. Emphasis has been on low-loss phase shifters to enable a new phased array architecture. The critical role of phase shifter loss and transient response in reflectarray antennas will be discussed. The Ferroelectric Reflectarray Critical Components Space Experiment was launched on the penultimate Space Shuttle, STS-134, in May of 2011. It included a bank of ferroelectric phase shifters with two different stoichiometries as well as ancillary electronics. The experiment package and status will be reported. In addition, unusual results of a Van der Pauw measurement involving a ferroelectric film grown on buffered high resisitivity silicon will be discussed.

  14. Ferromagnetic and ferroelectric nanoparticles in liquid crystals

    NASA Astrophysics Data System (ADS)

    Reznikov, Yuriy; Glushchenko, Anatoliy; Garbovskiy, Yuriy

    This chapter introduces the basic principles of physics of magnetic and ferroelectric nanoparticles suspensions in thermotropic liquid crystals (LCs). It also covers the main features of such suspensions along with the look at the challenges that researchers in the field are facing today. Special attention is paid to understanding of major physical mechanisms responsible for the inuence of nanoparticles on the properties of LCs. In the case of magnetic nanoparticles, their dipole moments are aligned by an external magnetic field that, in turn, results in a reorientation of the LC due to the surface anchoring between the nanoparticles and the LC. This mechanical coupling between the LC and the magnetic particles determines the unique sensitivity of the suspension to magnetic fields. In regard to the ferroelectric particles, their effect on LCs is due to a strong electric field by the permanent electric dipoles of the particles. This field is strong enough to change the orientational ordering of the LC surrounding the particle. In addition, the above-mentioned mechanism of the surface anchoring may also take place. The ongoing scientific and technological problems related to the suspensions are discussed. Among such problems are the stability of the suspensions, selection of the proper surfactants, formation of the particle chains, and the effect of the electric charges on the properties of the ferroelectric liquid crystal suspensions.

  15. Ferroelectricity in underdoped La-based cuprates

    PubMed Central

    Viskadourakis, Z.; Sunku, S. S.; Mukherjee, S.; Andersen, B. M.; Ito, T.; Sasagawa, T.; Panagopoulos, C.

    2015-01-01

    Doping a “parent” antiferromagnetic Mott insulator in cuprates leads to short-range electronic correlations and eventually to high-Tc superconductivity. However, the nature of charge correlations in the lightly doped cuprates remains unclear. Understanding the intermediate electronic phase in the phase diagram (between the parent insulator and the high-Tc superconductor) is expected to elucidate the complexity both inside and outside the superconducting dome, and in particular in the underdoped region. One such phase is ferroelectricity whose origin and relation to the properties of high-Tc superconductors is subject of current research. Here we demonstrate that ferroelectricity and the associated magnetoelectric coupling are in fact common in La-214 cuprates namely, La2-xSrxCuO4, La2LixCu1-xO4 and La2CuO4+x. It is proposed that ferroelectricity may result from local CuO6 octahedral distortions, associated with the dopant atoms and clustering of the doped charge carriers, which break spatial inversion symmetry at the local scale whereas magnetoelectric coupling can be tuned through Dzyaloshinskii-Moriya interaction. PMID:26486276

  16. Quantum properties of charged ferroelectric domain walls

    NASA Astrophysics Data System (ADS)

    Sturman, B.; Podivilov, E.; Stepanov, M.; Tagantsev, A.; Setter, N.

    2015-12-01

    We consider the properties of charged domain walls in ferroelectrics as a quantum problem. This includes determination of self-consistent attracting 1D potential for compensating charge carriers, the number and positions of discrete energy levels in this potential, dependencies on the ferroelectric characteristics, as well as the spatial structure and formation energy of the wall. Our description is based on the Hartree and Thomas-Fermi methods and Landau theory for the ferroelectric transitions. Changeover from a few to many quantum levels (with the electron binding energies ˜1 eV) is controlled by a single characteristic parameter. The quantum models well describe the core of the wall, whose width is typically ˜10 nm. Additionally, the walls possess pronounced long-range tails which are due to trap recharging. For the trap concentration Nt=(1017-1018) cm-3 , the tail length ℓ is of the μ m scale. On the distances much larger than ℓ the walls are electrically uncoupled from each other and the crystal faces.

  17. Influence of ferroelectric polarization on magnetic anisotropy

    NASA Astrophysics Data System (ADS)

    Mardana, A.; Ducharme, S.; Adenwalla, S.

    2010-03-01

    Thin film heterostructures of transition metal ferromagnets (FM) and polymer ferroelectrics (FE) are investigated to look for changes in the magnetic anisotropy of the FM layer that occur on switching the FE polarization (with an ensuing change in the electric field direction).[1] Samples of [Glass/ Pd (50 nm)/Co wedge (0.9-2.6nm)/ferroelectric P(VDF-TrFE) (53 nm)/Al (30nm)] are deposited via sputtering or evaporation for the metallic layers and via Langmuir-Schaefer deposition for the polymer ferroelectric. [2] Magnetic and FE properties have been characterized using the Magneto-Optical Kerr Effect (MOKE) and the pyroelectric effect. Polar and longitudinal MOKE loops are measured across the Co wedge for both positive and negative FE polarization and the difference in the two MOKE loops is ascribed to the changes in the magnetic anisotropy of the FM layer. [3] These changes are most apparent in the region where the Co undergoes a transition from in-plane to out-of-plane anisotropy. This research is supported by the NSF MRSEC through Grant No. DMR- 0820521 1. Chun-Gang Duan et al, Appl. Phys. Lett. 92, 122905 (2008) 2. A. V. Bune, et al, Nature (London) 391, 874 (1998) 3. P. F. Carcia, J.Appl. Phys. 63, 5066 (1988)

  18. Electrical activity of ferroelectric biomaterials and its effects on the adhesion, growth and enzymatic activity of human osteoblast-like cells

    NASA Astrophysics Data System (ADS)

    Vaněk, P.; Kolská, Z.; Luxbacher, T.; García, J. A. L.; Lehocký, M.; Vandrovcová, M.; Bačáková, L.; Petzelt, J.

    2016-05-01

    Ferroelectrics have been, among others, studied as electroactive implant materials. Previous investigations have indicated that such implants induce improved bone formation. If a ferroelectric is immersed in a liquid, an electric double layer and a diffusion layer are formed at the interface. This is decisive for protein adsorption and bioactive behaviour, particularly for the adhesion and growth of cells. The charge distribution can be characterized, in a simplified way, by the zeta potential. We measured the zeta potential in dependence on the surface polarity on poled ferroelectric single crystalline LiNbO3 plates. Both our results and recent results of colloidal probe microscopy indicate that the charge distribution at the surface can be influenced by the surface polarity of ferroelectrics under certain ‘ideal’ conditions (low ionic strength, non-contaminated surface, very low roughness). However, suggested ferroelectric coatings on the surface of implants are far from ideal: they are rough, polycrystalline, and the body fluid is complex and has high ionic strength. In real cases, it can therefore be expected that there is rather low influence of the sign of the surface polarity on the electric diffusion layer and thus on the specific adsorption of proteins. This is supported by our results from studies of the adhesion, growth and the activity of alkaline phosphatase of human osteoblast-like Saos-2 cells on ferroelectric LiNbO3 plates in vitro.

  19. Ferroelectric Thin Films for Electronic Applications

    NASA Astrophysics Data System (ADS)

    Udayakumar, K. R.

    This study yokes together the feasibility of a family of PbO-based perovskite-structured ferroelectric thin films as functional elements in nonvolatile random access memories (NVRAMs), in high capacity dynamic RAMs, and in a new class of flexure wave piezoelectric ultrasonic micromotors. The dielectric and ferroelectric properties of lead zirconate titanate (PZT) thin films were dependent on thickness; at saturation, the films were characterized by a relative permittivity of 1300, remanent polarization of 36 muC/cm^2 and breakdown strength of over 1 MV/cm. The temperature dependence of permittivity revealed an anomalous behavior with the film annealing temperature. Based on the ferroelectric properties in the bulk, thin films in the lead zirconate -lead zinc niobate (PZ-PZN) solid solution system at 8-12% PZN, examined as alternate compositions for ferroelectric memories, feature switched charges of 4-14 mu C/cm^2, with coercive and saturation voltages less than the semiconductor operating voltage of 5 V. Rapid thermally annealed lead magnesium niobate titanate films were privy to weak signal dielectric permittivity of 2900, remanent polarization of 11 muC/cm^2, and a storage density of 210 fC/mum^2 at 5 V; the films merit consideration for potential applications in ultra large scale integrated circuits as also ferroelectric nonvolatile RAMs. The high breakdown strength and relative permittivity of the PZT films entail maximum stored energy density 10^3 times larger than a silicon electrostatic motor. The longitudinal piezoelectric strain coefficient d_{33 } was measured to be 220 pC/N at a dc bias of 75 kV/cm. The transverse piezoelectric strain coefficient d_{31} bore a nonlinear relationship with the electric field; at 200 kV/cm, d _{31} was -88 pC/N. The development of the piezoelectric ultrasonic micromotors from the PZT thin films, and the architecture of the stator structures are described. Nonoptimized prototype micromotors show rotational velocities of 100

  20. Studies of ferroelectric heterostructure thin films, interfaces, and device-related processes via in situ analytical techniques.

    SciTech Connect

    Aggarwal, S.; Auciello, O.; Dhote, A. M.; Gao, Y.; Gruen, D. M.; Im, J.; Irene, E. A.; Krauss, A. R.; Muller, A. H.; Ramesh, R.

    1999-06-29

    The science and technology of ferroelectric thin films has experienced an explosive development during the last ten years. Low-density non-volatile ferroelectric random access memories (NVFRAMS) are now incorporated in commercial products such as ''smart cards'', while high permittivity capacitors are incorporated in cellular phones. However, substantial work is still needed to develop materials integration strategies for high-density memories. We have demonstrated that the implementation of complementary in situ characterization techniques is critical to understand film growth and device processes relevant to device development. We are using uniquely integrated time of flight ion scattering and recoil spectroscopy (TOF-ISARS) and spectroscopic ellipsometry (SE) techniques to perform in situ, real-time studies of film growth processes in the high background gas pressure required to growth ferroelectric thin films. TOF-ISARS provides information on surface processes, while SE permits the investigation of buried interfaces as they are being formed. Recent studies on SrBi{sub 2}Ta{sub 2}O{sub 9} (SBT) and Ba{sub x}Sr{sub 1{minus}x}TiO{sub 3} (BST) film growth and interface processes are discussed. Direct imaging of ferroelectric domains under applied electric fields can provide valuable information to understand domain dynamics in ferroelectric films. We discuss results of piezoresponse scanning force microscopy (SFM) imaging for nanoscale studies of polarization reversal and retention loss in Pb(Zr{sub x}Ti{sub 1{minus}x})O{sub 3} (PZT)-based capacitors. Another powerful technique suitable for in situ, real-time characterization of film growth processes and ferroelectric film-based device operation is based on synchrotrons X-ray scattering, which is currently being implemented at Argonne National Laboratory.

  1. Manipulation of charge transfer and transport in plasmonic-ferroelectric hybrids for photoelectrochemical applications

    PubMed Central

    Wang, Zhijie; Cao, Dawei; Wen, Liaoyong; Xu, Rui; Obergfell, Manuel; Mi, Yan; Zhan, Zhibing; Nasori, Nasori; Demsar, Jure; Lei, Yong

    2016-01-01

    Utilizing plasmonic nanostructures for efficient and flexible conversion of solar energy into electricity or fuel presents a new paradigm in photovoltaics and photoelectrochemistry research. In a conventional photoelectrochemical cell, consisting of a plasmonic structure in contact with a semiconductor, the type of photoelectrochemical reaction is determined by the band bending at the semiconductor/electrolyte interface. The nature of the reaction is thus hard to tune. Here instead of using a semiconductor, we employed a ferroelectric material, Pb(Zr,Ti)O3 (PZT). By depositing gold nanoparticle arrays and PZT films on ITO substrates, and studying the photocurrent as well as the femtosecond transient absorbance in different configurations, we demonstrate an effective charge transfer between the nanoparticle array and PZT. Most importantly, we show that the photocurrent can be tuned by nearly an order of magnitude when changing the ferroelectric polarization in PZT, demonstrating a versatile and tunable system for energy harvesting. PMID:26753764

  2. Magnetic-field-induced ferroelectric polarization reversal in magnetoelectric composites revealed by piezoresponse force microscopy.

    PubMed

    Miao, Hongchen; Zhou, Xilong; Dong, Shuxiang; Luo, Haosu; Li, Faxin

    2014-08-07

    Controlling electric polarization (or magnetization) in multiferroic materials with external magnetic fields (or electric fields) is very important for fundamental physics and spintronic devices. Although there has been some progress on magnetic-field-induced polarization reversal in single-phase multiferroics, such behavior has so far never been realized in composites. Here we show that it is possible to reverse ferroelectric polarization using magnetic fields in a bilayer Terfenol-D/PMN-33%PT composite. We realized this by ferroelectric domain imaging using piezoresponse force microscopy (PFM) under applied magnetic field loading. The internal electric field caused by the magnetoelectric (ME) effect in the PMN-PT crystal is considered as the driving force for the 180° polarization switching, and its existence is verified by switching spectroscopy PFM testing under a series of external magnetic fields. A quantitative method is further suggested to estimate the local ME coefficient based on the switching spectroscopy PFM testing results.

  3. Manipulation of charge transfer and transport in plasmonic-ferroelectric hybrids for photoelectrochemical applications

    NASA Astrophysics Data System (ADS)

    Wang, Zhijie; Cao, Dawei; Wen, Liaoyong; Xu, Rui; Obergfell, Manuel; Mi, Yan; Zhan, Zhibing; Nasori, Nasori; Demsar, Jure; Lei, Yong

    2016-01-01

    Utilizing plasmonic nanostructures for efficient and flexible conversion of solar energy into electricity or fuel presents a new paradigm in photovoltaics and photoelectrochemistry research. In a conventional photoelectrochemical cell, consisting of a plasmonic structure in contact with a semiconductor, the type of photoelectrochemical reaction is determined by the band bending at the semiconductor/electrolyte interface. The nature of the reaction is thus hard to tune. Here instead of using a semiconductor, we employed a ferroelectric material, Pb(Zr,Ti)O3 (PZT). By depositing gold nanoparticle arrays and PZT films on ITO substrates, and studying the photocurrent as well as the femtosecond transient absorbance in different configurations, we demonstrate an effective charge transfer between the nanoparticle array and PZT. Most importantly, we show that the photocurrent can be tuned by nearly an order of magnitude when changing the ferroelectric polarization in PZT, demonstrating a versatile and tunable system for energy harvesting.

  4. Buffer layer investigations on MFIS capacitors consisting of ferroelectric poly[vinylidene fluoride trifluoroethylene

    NASA Astrophysics Data System (ADS)

    Henkel, K.; Seime, B.; Paloumpa, I.; Müller, K.; Schmeißer, D.

    2010-02-01

    In this paper we present capacitance-voltage (CV) measurements on metal-ferroelectric-insulator-semiconductor (MFIS) capacitors with poly[vinylidene fluoride trifluoroethylene] (P[VDF/TrFE] as ferroelectric layer and SiO2, Al2O3 and HfO2 as buffering insulator layer. In order to discuss our data in a quantitative manner we perform fits to the data based on a model proposed by Miller and McWorther. The improvement of the polarization values and subsequently its effect on the hysteresis of the CV curve by the successive shrinking of the buffer layer thickness and the following choice of a high-k buffer material is demonstrated. Our data underline that a saturated polarization of P[VDF/TrFE] cannot be controlled with a SiO2 buffer layer and the insertion of a high-k buffer layer is essential for further improvements of the characteristics of MFIS stacks.

  5. Effect of Dipolar Orientational Polarization on Electronic Conductivity in Ferroelectric Polymer Electrets

    NASA Astrophysics Data System (ADS)

    Yang, Lianyun; Zhu, Lei

    2014-03-01

    The leakage current, ion migration, and dipolar orientational polarization are major losses in ferroelectric polymers. The loss from the leakage current originates from electronic conduction and its behavior could be significantly affected by the internal electric field, which is induced by the dipolar orientational polarization. In this work, the leakage current in the corona charged PVDF electrets is studied under different external electric fields. Under low applied electric field, when no or very few dipoles could flip, the conductivity from the leakage direct current increases upon increasing the electric field. Under higher electric field, the aligned dipole-induced internal field would prevent the electrons from going through so that the conductivity decreases. After all the dipoles are aligned with the external electric field, the conductivity can increase again. This study will help us better understand the interplay between electronic conduction and dipolar orientation in ferroelectric materials.

  6. Photovoltaic properties of ferroelectric BaTiO3 thin films RF sputter deposited on silicon

    NASA Technical Reports Server (NTRS)

    Dharmadhikari, V. S.; Grannemann, W. W.

    1982-01-01

    Ferroelectric thin films of BaTiO3 have been successfully deposited on n-type silicon substrates at temperatures above 500 C by RF sputtering in an O2/Ar atmosphere. Analysis by X-ray diffraction patterns show that films deposited at room temperature are amorphous. At temperatures above 500 C, crystalline BaTiO3 films with a tetragonal structure are obtained. The polarization-electric field (P-E) hysteresis loops and a broad peak in the dielectric constant versus temperature curve at Curie point indicate that the RF sputtered BaTiO3 films are ferroelectric. An anomalous photovoltaic effect is observed in these thin films which is related to the remanent polarization of the material. The results on open-circuit and short-circuit measurements provide an important basis for a better understanding of the role of photovoltaic field, photovoltaic current, and the pyroelectric properties in photoferroelectric domain switching.

  7. Dielectric, ferroelectric and mechanical Properties of Microwave Sintered Bi based High temperature Piezoelectric Ceramics

    NASA Astrophysics Data System (ADS)

    Angalakurthi, Rambabu; Raju, K. C. James

    2011-10-01

    The sintering of advanced ceramics requires fast heating in order to avoid both grain growth and inter diffusion. In this context, the microwave sintering is a powerful method since it enables sintering in a short time. This paper reports the synthesis and characterization of Strontium Bismuth Titanate (SBTi) system. The material powder was prepared by solid state route and sintering was carried out by both conventional and microwave furnaces. Morphological, dielectric, ferroelectric and mechanical properties were studied for both samples. The dielectric constant and loss tangent of the conventional and microwave sintered samples have ranged between (185-195) & (0.005-0.007) and (195-220) & (0.004-0.006) respectively when measured at 1MHz frequency. The microwave sintering of the SBTi ceramics leads to higher densification (97% of the theoretical density), fine microstructure, and good mechanical and ferroelectric properties in much shorter duration of time compared to that of the conventional sintering process.

  8. Direct measurement of oxygen octahedral rotations in improper ferroelectric superlattices by STEM

    NASA Astrophysics Data System (ADS)

    Lapano, Jason; Haislmaier, Ryan; Stone, Gregory; Gopalan, Venkat; Engel-Herbert, Roman

    Complex ABO3 perovskites are an intensely studied class of materials due to their numerous magnetic and electronic functionalities. Using strain and A-site cation, can induce new high temperature functionality known as improper ferroelectricity1. Visualizing the interplay between strain, cation ordering and octahedral rotations in improper ferroelectics is crucial to understand how this property manifests itself in thin films2. A series of CaTiO3n/SrTiO3n with periodicities n =2-10 were grown on (La,Sr)(Al,Ta)O3 by hybrid molecular beam epitaxy. I will discuss how strain and layering affects the cation and oxygen sublattices, and how these distortions propagate through the layers, with direct imaging of the oxygen cations by annular bright field (ABF) STEM. I will then relate these back to understanding how improper ferroelectricity evolves in these films. National Science Foundation MRSEC.

  9. Plasma reforming of methane in a tunable ferroelectric packed-bed dielectric barrier discharge reactor

    NASA Astrophysics Data System (ADS)

    Montoro-Damas, A. M.; Brey, J. Javier; Rodríguez, Miguel A.; González-Elipe, Agustín R.; Cotrino, José

    2015-11-01

    In a tunable circular parallel plate dielectric barrier discharge reactor with pellets of a ferroelectric material separating the electrodes we investigate the plasma reforming of methane trying to maximize both the reaction yield and the energetic efficiency of the process. The geometrical configuration of the reactor (gap between electrodes, active electrode area) and the ferroelectric pellet size have been systematically varied to determine their influence on the process efficiency. The comparison between wet (with H2O as reactant), oxidative (with O2), and dry (with CO2) reforming reactions reveals a higher efficiency for the former with CO + H2 as main reaction products. The maximum energetic efficiency EE, defined as the produced number of litres of H2 per kWh, found for optimized working conditions at low-level applied power is higher than the up to date best-known results. A comprehensive discussion of the influence of the different parameters affecting the reaction yield is carried out.

  10. Electrocaloric effect in core-shell ferroelectric ceramics: Theoretical approach and practical conclusions

    NASA Astrophysics Data System (ADS)

    Anoufa, M.; Kiat, J. M.; Bogicevic, C.

    2015-10-01

    Most of the theoretical and experimental studies on the electrocaloric effect (ECE) are devoted to thin films, but they can be hardly envisaged for cooling macroscopic systems; moreover, the results obtained cannot be easily transposed for larger systems like multilayered ceramics. Therefore, efforts should also be focused on predicting, synthesizing, and characterizing interesting bulk single crystal or ceramics. In ferroelectric nanoparticles and ceramics, the core-shell structure of grains is of uttermost importance to explain the experimental results at small sizes. Moreover, it can be used to tailor physical properties, such as energy storage, by experimenting with the composition, thickness, and permittivity of the shell. Here, we report the effect of such structures on the electrocaloric effects in a variety of ferroelectric materials. The magnitude of ECE as well as its field and temperature-dependence are obtained for different types of core-shells. The optimal configuration for a maximal ECE is deduced.

  11. A Novel Metal-Ferroelectric-Semiconductor Field-Effect Transistor Memory Cell Design

    NASA Technical Reports Server (NTRS)

    Phillips, Thomas A.; Bailey, Mark; Ho, Fat Duen

    2004-01-01

    The use of a Metal-Ferroelectric-Semiconductor Field-Effect Transistor (MFSFET) in a resistive-load SRAM memory cell has been investigated A typical two-transistor resistive-load SRAM memory cell architecture is modified by replacing one of the NMOS transistors with an n-channel MFSFET. The gate of the MFSFET is connected to a polling voltage pulse instead of the other NMOS transistor drain. The polling voltage pulses are of sufficient magnitude to saturate the ferroelectric gate material and force the MFSFET into a particular logic state. The memory cell circuit is further modified by the addition of a PMOS transistor and a load resistor in order to improve the retention characteristics of the memory cell. The retention characteristics of both the "1" and "0" logic states are simulated. The simulations show that the MFSFET memory cell design can maintain both the "1" and "0" logic states for a long period of time.

  12. Surface potential at a ferroelectric grain due to asymmetric screening of depolarization fields

    SciTech Connect

    Genenko, Yuri A. Hirsch, Ofer; Erhart, Paul

    2014-03-14

    Nonlinear screening of electric depolarization fields, generated by a stripe domain structure in a ferroelectric grain of a polycrystalline material, is studied within a semiconductor model of ferroelectrics. It is shown that the maximum strength of local depolarization fields is rather determined by the electronic band gap than by the spontaneous polarization magnitude. Furthermore, field screening due to electronic band bending and due to presence of intrinsic defects leads to asymmetric space charge regions near the grain boundary, which produce an effective dipole layer at the surface of the grain. This results in the formation of a potential difference between the grain surface and its interior of the order of 1 V, which can be of either sign depending on defect transition levels and concentrations. Exemplary acceptor doping of BaTiO{sub 3} is shown to allow tuning of the said surface potential in the region between 0.1 and 1.3 V.

  13. Electrostrain enhancement at an invisible boundary in a single ferroelectric phase

    NASA Astrophysics Data System (ADS)

    Zhao, Luo; Ke, Xiaoqin; Wang, Weichen; Zhang, Le; Zhou, Chao; Zhou, Zhijian; Zhang, Lixue; Ren, Xiaobing

    2017-01-01

    In ferroelectric materials the maximum electrostrain effect usually occurs at a phase boundary (often referred to as a "morphotropic phase boundary") between two or more different phases due to lattice instability at such compositions. As a result it is not expected that the electrostrain maximum can appear in a single ferroelectric phase regime which is away from lattice instability. In this Rapid Communication we report an unexpected finding that the electrostrain maximum occurs in a single rhombohedral phase region of the (1 -x %) Ba (T i0.8H f0.2 ) O3-x %(B a0.7C a0.3 ) Ti O3 system. The composition showing the maximum electrostrain corresponds to an "invisible boundary" within the single ferroelectric phase, which is a vertical line starting from the quadruple point of the system. At the invisible boundary other anomalies, such as maximum spontaneous polarization also appear. The origin of electrostrain enhancement at the invisible boundary is considered to correlate with an easy polarization extension inherited from the quadruple point. The electrostrain enhancement effect at the invisible boundary has the advantage of having better temperature stability as compared with that at a phase boundary and thus may provide a way for designing high-electrostrain materials with improved temperature stability.

  14. Local switching of two-dimensional superconductivity using the ferroelectric field effect

    NASA Astrophysics Data System (ADS)

    Takahashi, K. S.; Gabay, M.; Jaccard, D.; Shibuya, K.; Ohnishi, T.; Lippmaa, M.; Triscone, J.-M.

    2006-05-01

    Correlated oxides display a variety of extraordinary physical properties including high-temperature superconductivity and colossal magnetoresistance. In these materials, strong electronic correlations often lead to competing ground states that are sensitive to many parameters-in particular the doping level-so that complex phase diagrams are observed. A flexible way to explore the role of doping is to tune the electron or hole concentration with electric fields, as is done in standard semiconductor field effect transistors. Here we demonstrate a model oxide system based on high-quality heterostructures in which the ferroelectric field effect approach can be studied. We use a single-crystal film of the perovskite superconductor Nb-doped SrTiO3 as the superconducting channel and ferroelectric Pb(Zr,Ti)O3 as the gate oxide. Atomic force microscopy is used to locally reverse the ferroelectric polarization, thus inducing large resistivity and carrier modulations, resulting in a clear shift in the superconducting critical temperature. Field-induced switching from the normal state to the (zero resistance) superconducting state was achieved at a well-defined temperature. This unique system could lead to a field of research in which devices are realized by locally defining in the same material superconducting and normal regions with `perfect' interfaces, the interface being purely electronic. Using this approach, one could potentially design one-dimensional superconducting wires, superconducting rings and junctions, superconducting quantum interference devices (SQUIDs) or arrays of pinning centres.

  15. Thick lead-free ferroelectric films with high Curie temperatures through nanocomposite-induced strain.

    PubMed

    Harrington, Sophie A; Zhai, Junyi; Denev, Sava; Gopalan, Venkatraman; Wang, Haiyan; Bi, Zhenxing; Redfern, Simon A T; Baek, Seung-Hyub; Bark, Chung W; Eom, Chang-Beom; Jia, Quanxi; Vickers, Mary E; Macmanus-Driscoll, Judith L

    2011-07-03

    Ferroelectric materials are used in applications ranging from energy harvesting to high-power electronic transducers. However, industry-standard ferroelectric materials contain lead, which is toxic and environmentally unfriendly. The preferred alternative, BaTiO(3), is non-toxic and has excellent ferroelectric properties, but its Curie temperature of ∼130 °C is too low to be practical. Strain has been used to enhance the Curie temperature of BaTiO(3) (ref. 4) and SrTiO(3) (ref. 5) films, but only for thicknesses of tens of nanometres, which is not thick enough for many device applications. Here, we increase the Curie temperature of micrometre-thick films of BaTiO(3) to at least 330 °C, and the tetragonal-to-cubic structural transition temperature to beyond 800 °C, by interspersing stiff, self-assembled vertical columns of Sm(2)O(3) throughout the film thickness. The columns, which are 10 nm in diameter, strain the BaTiO(3) matrix by 2.35%, forcing it to maintain its tetragonal structure and resulting in the highest BaTiO(3) transition temperatures so far.

  16. Local switching of two-dimensional superconductivity using the ferroelectric field effect.

    PubMed

    Takahashi, K S; Gabay, M; Jaccard, D; Shibuya, K; Ohnishi, T; Lippmaa, M; Triscone, J-M

    2006-05-11

    Correlated oxides display a variety of extraordinary physical properties including high-temperature superconductivity and colossal magnetoresistance. In these materials, strong electronic correlations often lead to competing ground states that are sensitive to many parameters--in particular the doping level--so that complex phase diagrams are observed. A flexible way to explore the role of doping is to tune the electron or hole concentration with electric fields, as is done in standard semiconductor field effect transistors. Here we demonstrate a model oxide system based on high-quality heterostructures in which the ferroelectric field effect approach can be studied. We use a single-crystal film of the perovskite superconductor Nb-doped SrTiO3 as the superconducting channel and ferroelectric Pb(Zr,Ti)O3 as the gate oxide. Atomic force microscopy is used to locally reverse the ferroelectric polarization, thus inducing large resistivity and carrier modulations, resulting in a clear shift in the superconducting critical temperature. Field-induced switching from the normal state to the (zero resistance) superconducting state was achieved at a well-defined temperature. This unique system could lead to a field of research in which devices are realized by locally defining in the same material superconducting and normal regions with 'perfect' interfaces, the interface being purely electronic. Using this approach, one could potentially design one-dimensional superconducting wires, superconducting rings and junctions, superconducting quantum interference devices (SQUIDs) or arrays of pinning centres.

  17. Ferroelectric-like response from the surface of SrTiO₃ crystals at high temperatures

    SciTech Connect

    Jyotsna, Shubhra; Arora, Ashima; Sekhon, Jagmeet S.; Sheet, Goutam

    2014-09-14

    Since SrTiO₃ has a high dielectric constant, it is used as a substrate for a large number of complex physical systems for electrical characterization. Since SrTiO₃ crystals are known to be non-ferroelectric/non-piezoelectric at room temperature and above, SrTiO₃ has been believed to be a good choice as a substrate/base material for PFM (Piezoresponse Force Microscopy) on novel systems at room temperature. In this paper, from PFM-like measurement using an atomic force microscope on bare crystals of (110) SrTiO₃ we show that ferroelectric and piezoelectric-like response may originate from bare SrTiO₃ at remarkably high temperatures up to 420 K. Electrical domain writing and erasing are also possible using a scanning probe tip on the surface of SrTiO₃ crystals. This observation indicates that the role of the electrical response of SrTiO₃ needs to be revisited in the systems where signature of ferroelectricity/piezoelectricity has been previously observed with SrTiO₃ as a substrate/base material.

  18. Thick lead-free ferroelectric films with high Curie temperatures through nanocomposite-induced strain

    NASA Astrophysics Data System (ADS)

    Harrington, Sophie A.; Zhai, Junyi; Denev, Sava; Gopalan, Venkatraman; Wang, Haiyan; Bi, Zhenxing; Redfern, Simon A. T.; Baek, Seung-Hyub; Bark, Chung W.; Eom, Chang-Beom; Jia, Quanxi; Vickers, Mary E.; MacManus-Driscoll, Judith L.

    2011-08-01

    Ferroelectric materials are used in applications ranging from energy harvesting to high-power electronic transducers. However, industry-standard ferroelectric materials contain lead, which is toxic and environmentally unfriendly. The preferred alternative, BaTiO3, is non-toxic and has excellent ferroelectric properties, but its Curie temperature of ~130 °C is too low to be practical. Strain has been used to enhance the Curie temperature of BaTiO3 (ref. 4) and SrTiO3 (ref. 5) films, but only for thicknesses of tens of nanometres, which is not thick enough for many device applications. Here, we increase the Curie temperature of micrometre-thick films of BaTiO3 to at least 330 °C, and the tetragonal-to-cubic structural transition temperature to beyond 800 °C, by interspersing stiff, self-assembled vertical columns of Sm2O3 throughout the film thickness. The columns, which are 10 nm in diameter, strain the BaTiO3 matrix by 2.35%, forcing it to maintain its tetragonal structure and resulting in the highest BaTiO3 transition temperatures so far.

  19. Giant electromechanical coupling of relaxor ferroelectrics controlled by polar nanoregion vibrations

    PubMed Central

    Manley, Michael E.; Abernathy, Douglas L.; Sahul, Raffi; Parshall, Daniel E.; Lynn, Jeffrey W.; Christianson, Andrew D.; Stonaha, Paul J.; Specht, Eliot D.; Budai, John D.

    2016-01-01

    Relaxor-based ferroelectrics are prized for their giant electromechanical coupling and have revolutionized sensor and ultrasound applications. A long-standing challenge for piezoelectric materials has been to understand how these ultrahigh electromechanical responses occur when the polar atomic displacements underlying the response are partially broken into polar nanoregions (PNRs) in relaxor-based ferroelectrics. Given the complex inhomogeneous nanostructure of these materials, it has generally been assumed that this enhanced response must involve complicated interactions. By using neutron scattering measurements of lattice dynamics and local structure, we show that the vibrational modes of the PNRs enable giant coupling by softening the underlying macrodomain polarization rotations in relaxor-based ferroelectric PMN-xPT {(1 − x)[Pb(Mg1/3Nb2/3)O3] – xPbTiO3} (x = 30%). The mechanism involves the collective motion of the PNRs with transverse acoustic phonons and results in two hybrid modes, one softer and one stiffer than the bare acoustic phonon. The softer mode is the origin of macroscopic shear softening. Furthermore, a PNR mode and a component of the local structure align in an electric field; this further enhances shear softening, revealing a way to tune the ultrahigh piezoelectric response by engineering elastic shear softening. PMID:27652338

  20. Giant electromechanical coupling of relaxor ferroelectrics controlled by polar nanoregion vibrations

    DOE PAGES

    Manley, Michael E.; Abernathy, Douglas L.; Sahul, Raffi; ...

    2016-09-01

    Relaxor-based ferroelectrics are prized for their giant electromechanical coupling and have revolutionized sensor and ultrasound applications. A long-standing challenge for piezoelectric materials has been to understand how these ultrahigh electromechanical responses occur when the polar atomic displacements underlying the response are partially broken into polar nanoregions (PNRs) in relaxor-based ferroelectrics. Given the complex inhomogeneous nanostructure of these materials, it has generally been assumed that this enhanced response must involve complicated interactions. By using neutron scattering measurements of lattice dynamics and local structure, we show that the vibrational modes of the PNRs enable giant coupling by softening the underlying macrodomain polarizationmore » rotations in relaxor-based ferroelectric PMN-xPT {(1 x)[Pb(Mg1/3Nb2/3)O3] xPbTiO3} (x = 30%). The mechanism involves the collective motion of the PNRs with transverse acoustic phonons and results in two hybrid modes, one softer and one stiffer than the bare acoustic phonon. The softer mode is the origin of macroscopic shear softening. Furthermore, a PNR mode and a component of the local structure align in an electric field; this further enhances shear softening, revealing a way to tune the ultrahigh piezoelectric response by engineering elastic shear softening.« less

  1. Giant electromechanical coupling of relaxor ferroelectrics controlled by polar nanoregion vibrations

    SciTech Connect

    Manley, Michael E.; Abernathy, Douglas L.; Sahul, Raffi; Parshall, Daniel E.; Lynn, Jeffrey W.; Christianson, Andrew D.; Stonaha, Paul J.; Specht, Eliot D.; Budai, John D.

    2016-09-01

    Relaxor-based ferroelectrics are prized for their giant electromechanical coupling and have revolutionized sensor and ultrasound applications. A long-standing challenge for piezoelectric materials has been to understand how these ultrahigh electromechanical responses occur when the polar atomic displacements underlying the response are partially broken into polar nanoregions (PNRs) in relaxor-based ferroelectrics. Given the complex inhomogeneous nanostructure of these materials, it has generally been assumed that this enhanced response must involve complicated interactions. By using neutron scattering measurements of lattice dynamics and local structure, we show that the vibrational modes of the PNRs enable giant coupling by softening the underlying macrodomain polarization rotations in relaxor-based ferroelectric PMN-xPT {(1 x)[Pb(Mg1/3Nb2/3)O3] xPbTiO3} (x = 30%). The mechanism involves the collective motion of the PNRs with transverse acoustic phonons and results in two hybrid modes, one softer and one stiffer than the bare acoustic phonon. The softer mode is the origin of macroscopic shear softening. Furthermore, a PNR mode and a component of the local structure align in an electric field; this further enhances shear softening, revealing a way to tune the ultrahigh piezoelectric response by engineering elastic shear softening.

  2. Electrospinning induced ferroelectricity in poly(vinylidene fluoride) fibers.

    PubMed

    Baji, Avinash; Mai, Yiu-Wing; Li, Qian; Liu, Yun

    2011-08-01

    Poly(vinylidene fluoride) (PVDF) fibers with diameters ranging from 70 to 400 nm are produced by electrospinning and the effect of fiber size on the ferroelectric β-crystalline phase is determined. Domain switching and associated ferro-/piezo-electric properties of the electrospun PVDF fibers were also determined. The fibers showed well-defined ferroelectric and piezoelectric properties.

  3. Electrospinning induced ferroelectricity in poly(vinylidene fluoride) fibers

    NASA Astrophysics Data System (ADS)

    Baji, Avinash; Mai, Yiu-Wing; Li, Qian; Liu, Yun

    2011-08-01

    Poly(vinylidene fluoride) (PVDF) fibers with diameters ranging from 70 to 400 nm are produced by electrospinning and the effect of fiber size on the ferroelectric β-crystalline phase is determined. Domain switching and associated ferro-/piezo-electric properties of the electrospun PVDF fibers were also determined. The fibers showed well-defined ferroelectric and piezoelectric properties.

  4. Ferroelectric functionality in SrTiO3/Si heterojunctions

    NASA Astrophysics Data System (ADS)

    Yu, H. L.; Wu, Y. Z.; Jiang, X. F.; Cai, M. Q.; Gu, L. P.; Yang, G. W.

    2013-11-01

    By the first-principles calculations, various SrTiO3/Si interface architectures have been studied in this work and the computed results showed that the stable ferroelectricity can be realized in the SrTiO3/Si system. The Si/SrO interface architecture with the Si-O configuration showed predominately the ferroelectric nature and the height of the potential barrier between the negative and positive poled states (0.77 eV per interfacial unit cell). The presence of the covalent bond between the substrate Si and O of SrO layer adjacent to the substrate Si leads to the disappearance of the electronic dipoles at the interface, and the reason is that the Si-O configuration of the Si/SrO interface architecture exhibits ferroelectric nature. In order to further understand the influence of the interfacial bonding nature on the ferroelectricity of the oxide layer, the BaTiO3/Si heterojunction with the same interface architectures also have been studied. Indeed, the Si/BaO interface architecture with the Si-O configuration showed predominately the ferroelectric nature too. Certainly, a full SrO (or BaO) layer directly grown on the substrate Si is benefit to the realization of the ferroelectric functionality in the ferroelectric-Si heterojunction. These findings are useful for the understanding of the basic physics of the ferroelectric-Si heterojunction and the silicon-based functional oxide device design.

  5. Future Development of Dense Ferroelectric Memories for Space Applications

    NASA Technical Reports Server (NTRS)

    Philpy, Stephen C.; Derbenwick, Gary F.

    2001-01-01

    The availability of high density, radiation tolerant, nonvolatile memories is critical for space applications. Ferroelectric memories, when fabricated with radiation hardened complementary metal oxide semiconductors (CMOS), can be manufactured and packaged to provide high density replacements for Flash memory, which is not radiation tolerant. Previous work showed ferroelectric memory cells to be resistant to single event upsets and proton irradiation, and ferroelectric storage capacitors to be resistant to neutron exposure. In addition to radiation hardness, the fast programming times, virtually unlimited endurance, and low voltage, low power operation make ferroelectric memories ideal for space missions. Previously, a commercial double level metal 64-kilobit ferroelectric memory was presented. Although the capabilities of radiation hardened wafer fabrication facilities lag behind those of the most modern commercial wafer fabrication facilities, several paths to achieving radiation tolerant, dense ferroelectric memories are emerging. Both short and long term solutions are presented in this paper. Although worldwide major semiconductor companies are introducing commercial ferroelectric memories, funding limitations must be overcome to proceed with the development of high density, radiation tolerant ferroelectric memories.

  6. Ferroelectric domain structure of Pb(Zr /sub 52/Ti /sub 48/)O/sub 3/

    SciTech Connect

    Goo, E.K.; Mishra, R.K.

    1980-08-01

    Ferroelectric domains are twins that are formed when PZT undergoes a phase transformation from a non-ferroelectric cubic phase to a ferroelectric tetragonal phase upon cooling below approx. 375/sup 0/C. The tetragonal phase is spontaneously polarized in the direction of c-axis, making each twin a ferroelectric domain.

  7. Characteristics of Radio-Frequency Circuits Utilizing Ferroelectric Capacitors

    NASA Technical Reports Server (NTRS)

    Eskridge, Michael; Gui, Xiao; MacLeod, Todd; Ho, Fat D.

    2011-01-01

    Ferroelectric capacitors, most commonly used in memory circuits and variable components, were studied in simple analog radio-frequency circuits such as the RLC resonator and Colpitts oscillator. The goal was to characterize the RF circuits in terms of frequency of oscillation, gain, etc, using ferroelectric capacitors. Frequencies of oscillation of both circuits were measured and studied a more accurate resonant frequency can be obtained using the ferroelectric capacitors. Many experiments were conducted and data collected. A model to simulate the experimental results will be developed. Discrepancies in gain and frequency in these RF circuits when conventional capacitors are replaced with ferroelectric ones were studied. These results will enable circuit designers to anticipate the effects of using ferroelectric components in their radio- frequency applications.

  8. Ferroelectric nanotubes fabricated using nanowires as positive templates

    SciTech Connect

    Alexe, M.; Hesse, D.; Schmidt, V.; Senz, S.; Fan, H. J.; Zacharias, M.; Goesele, U.

    2006-10-23

    The authors report on fabrication and electrical characterization of ferroelectric nanotubes and metal-ferroelectric-metal composite nanotubes using silicon and ZnO nanowires as positive templates. Nanotubes of high aspect ratio with a minimum inner diameter of about 100 nm and a length ranging from 0.5 {mu}m to a few microns have been obtained by magnetron sputtering and/or pulsed laser deposition. Metal-ferroelectric one-dimensional structures were characterized by piezoelectric scanning probe microscopy, showing piezoelectric hysteresis loops and ferroelectric switching. The presented fabrication approach can be used to fabricate three-dimensional capacitors for ferroelectric nonvolatile memories as well as nanosize piezoelectric scanners and actuators.

  9. Full first-principles simulations on 180^o ferroelectric stripe domains in realistic ferroelectric capacitors.

    NASA Astrophysics Data System (ADS)

    Junquera, Javier; Aguado-Puente, Pablo

    2007-03-01

    The field of ferroelectric thin films is at a momentous stage. Several experimental and theoretical works, both within a phenomenological approach or atomistic models, have been devoted to ascertain the ground state of ferroelectric thin-film capacitors. Using a full first-principles density-functional-theory approach, we have simulated 180^o ferroelectric stripe domains at 0 K in SrRuO3/BaTiO3/SrRuO3 and SrRuO3/PbTiO3/SrRuO3 realistic ferroelectric capacitors epitaxially grown on a SrTiO3 substrate. For a ferroelectic thin-film 2 unit cells thick, the lateral sizes of the domains ranged from 2 to 4 unit cells. The in-plane displacement of the atoms is essential to stabilize the domain structure. A exotic vortex structure, closed by the atoms of the first metallic layer, is found for the polarization. Ph. Ghosez and J. Junquera, http://xxx.lanl.gov/pdf/cond-mat/0605299, and references therein. J. M. Soler et al., J. Phys.: Condens. Matter 14 2745 (2002)

  10. Predicting a Ferrimagnetic-Ferroelectric Phase of Zn2FeOsO6 with Strong Magnetoelectric Coupling

    NASA Astrophysics Data System (ADS)

    Xiang, Hongjun; Wang, P. S.; Ren, Wei; Bellaiche, L.

    2015-03-01

    Multiferroic materials, in which ferroelectric and magnetic ordering coexist, are of fundamental interest for the development of novel memory devices that allow for electrical writing and non-destructive magnetic readout operation. The great challenge is to create room temperature multiferroic materials with strongly coupled ferroelectric and ferromagnetic (or ferrimagnetic) orderings. BiFeO3 has been the most heavily investigated single-phase multiferroic to date due to the coexistence of its magnetic order and ferroelectric order at room temperature. However, there is no net magnetic moment in the cycloidal (antiferromagnetic-like) magnetic state of bulk BiFeO3, which severely limits its realistic applications in electric field controlled spintronic devices. Here, we predict that double perovskite Zn2FeOsO6 is a new multiferroic with properties superior to BiFeO3. First, there are strong ferroelectricity and strong ferrimagnetism at room temperature in Zn2FeOsO6. Second, the easy-plane of the spontaneous magnetization can be switched by an external electric field, evidencing the strong magnetoelectric coupling existing in this system. Our results suggest that ferrimagnetic 3d-5d double perovskite may therefore be used to achieve voltage control of magnetism in future spintronic devices.

  11. Ferroelectricity and ferroelectric resistive switching in sputtered Hf0.5Zr0.5O2 thin films

    NASA Astrophysics Data System (ADS)

    Fan, Zhen; Xiao, Juanxiu; Wang, Jingxian; Zhang, Lei; Deng, Jinyu; Liu, Ziyan; Dong, Zhili; Wang, John; Chen, Jingsheng

    2016-06-01

    Ferroelectric properties and ferroelectric resistive switching (FE-RS) of sputtered Hf0.5Zr0.5O2 (HZO) thin films were investigated. The HZO films with the orthorhombic phase were obtained without capping or post-deposition annealing. Ferroelectricity was demonstrated by polarization-voltage (P-V) hysteresis loops measured in a positive-up negative-down manner and piezoresponse force microscopy. However, defects such as oxygen vacancies caused the films to become leaky. The observed ferroelectricity and semiconducting characteristics led to the FE-RS effect. The FE-RS effect may be explained by a polarization modulated trap-assisted tunneling model. Our study not only provides a facile route to develop ferroelectric HfO2-based thin films but also explores their potential applications in FE-RS memories.

  12. Nanomanufacturing and analysis of novel continuous ferroelectric PVDF and P(VDF-TrFE) nanofibers

    NASA Astrophysics Data System (ADS)

    Ren, Xi

    Poly(vinylidene fluoride) (PVDF) and PVDF copolymers are well known for their ferroelectric and piezoelectric properties. Currently, they are mainly used in applications in the form of films. Thin PVDF films have been shown to possess unique ferroelectric properties in the nanoscale range. However, their two-dimensional nature limits their applicability in active engineering materials and structures. One-dimensional PVDF nanofibers can be expected to combine ferroelectric behavior with enhanced mechanical properties and ultrahigh flexibility providing critical advantages for applications. In this work, novel continuous PVDF nanofibers were nanomanufactured and systematically studied for the first time. Nanofibers from PVDF and P(VDF-TrFE) copolymer with several molecular weights and co-polymer compositions were manufactured by electrospinning. The method consists of spinning polymer solutions in high electric fields. Effects of process parameters on nanofiber diameters and morphology were studied. Resulting nanofibers were characterized by FE-SEM, TEM, XRD, FTIR, DSC and TGA. Effects of annealing on copolymer nanofibers were analyzed. Nanofiber-reinforced composites were manufactured and their polarization behavior studied using a specially designed experimental device. A number of pioneering observations and discoveries were made as a result of this analysis. For example, analysis of crystalline structure of PVDF nanofibers showed that the initial a phase of the PVDF raw material was converted to beta phase during electrospinning. This result is very encouraging as the beta phase is primarily responsible for the piezo- and ferroelectric behavior of PVDF polymers. It was also shown for the first time that nanofabricated P(VDF-TrFE) nanofibers exhibited distinct Curie points and different structures than their raw materials. Annealing was shown to be an effective way to modify properties of P(VDF-TrFE) co-polymer nanofibers. Overall, the results demonstrated for the

  13. Electric-field-induced local and mesoscale structural changes in polycrystalline dielectrics and ferroelectrics

    PubMed Central

    Usher, Tedi-Marie; Levin, Igor; Daniels, John E.; Jones, Jacob L.

    2015-01-01

    The atomic-scale response of dielectrics/ferroelectrics to electric fields is central to their functionality. Here we introduce an in situ characterization method that reveals changes in the local atomic structure in polycrystalline materials under fields. The method employs atomic pair distribution functions (PDFs), determined from X-ray total scattering that depends on orientation relative to the applied field, to probe structural changes over length scales from sub-Ångstrom to several nanometres. The PDF is sensitive to local ionic displacements and their short-range order, a key uniqueness relative to other techniques. The method is applied to representative ferroelectrics, BaTiO3 and Na½Bi½TiO3, and dielectric SrTiO3. For Na½Bi½TiO3, the results reveal an abrupt field-induced monoclinic to rhombohedral phase transition, accompanied by ordering of the local Bi displacements and reorientation of the nanoscale ferroelectric domains. For BaTiO3 and SrTiO3, the local/nanoscale structural changes observed in the PDFs are dominated by piezoelectric lattice strain and ionic polarizability, respectively. PMID:26424360

  14. Temperature Dependence of Dielectric and Ferroelectric Properties of BiFeO3 Thin Films

    SciTech Connect

    Biegalski, Michael D; Jang, J H; Bark, C; Eom, Professor Chang-Beom

    2009-01-01

    Multiferroic materials, with their potential for novel devices and sensors, have spurred an immense amount of research. The most concentrated effort has been on BiFeO3 thin films due to their high N el temperature and high ferroelectric transition temperature. Most studies on BiFeO3 films suffer from electrical leakage, requiring the measurement of dielectric or ferroelectric properties to be conducted at low temperatures. In this work we show that room-temperature leakage is not intrinsic to BiFeO3. Results are shown for highly insulating films, including the temperature dependence (10K to 300K) of the dielectric properties, ferroelectric P-E loops, and leakage current. This data shows very little temperature change in the dielectric constant with a TCC of 0.38 K-1, and dielectric losses below 0.005. The remanent polarization similarly showed no temperature dependence within the error of the measurement with a Pr of 67 1 C/cm2. The leakage current remains below 3x10-4(A/cm2) at 100 kV/cm. This work proves that BiFeO3 does not intrinsically have high leakage, and validates the extrapolation of the properties of BiFeO3 films measured at low temperatures to room temperatures.

  15. Magnetism-Driven Ferroelectricity in Double Perovskite Y₂NiMnO₆.

    PubMed

    Su, J; Yang, Z Z; Lu, X M; Zhang, J T; Gu, L; Lu, C J; Li, Q C; Liu, J-M; Zhu, J S

    2015-06-24

    We report the discovery of multiferroic behavior in double perovskite Y2NiMnO6. X-ray diffraction shows that the material has a centrosymmetric crystal structure of space group P2(1)/n with Ni(2+)/Mn(4+) ordering. This result is further confirmed by aberration-corrected scanning transmission electron microscopy combined with atomic resolution electron energy loss spectroscopy. The appearance of ferroelectric polarization coincides with the magnetic phase transition (∼67 K), which indicates that the ferroelectricity is driven by magnetism, and this is further confirmed by its strong magnetoelectric (ME) effect. We proposed the origin of the ferroelectricity is associated with the combination of Ni(2+)/Mn(4+) charge ordering and the ↑↑↓↓ spin ordering. When compared with other known magnetic multiferroics, Y2NiMnO6 displays several attractive multiferroic properties, including high polarization (∼145 μC/m(2)), a high multiferroic transition temperature (∼67 K), and strong ME coupling (∼21%).

  16. Large enhancement of the photovoltaic effect in ferroelectric complex oxides through bandgap reduction

    PubMed Central

    An, Hyunji; Han, Jun Young; Kim, Bongjae; Song, Jaesun; Jeong, Sang Yun; Franchini, Cesare; Bark, Chung Wung; Lee, Sanghan

    2016-01-01

    Tuning the bandgap in ferroelectric complex oxides is a possible route for improving the photovoltaic activity of materials. Here, we report the realization of this effect in epitaxial thin films of the ferroelectric complex oxide Bi3.25La0.75Ti3O12 (BLT) suitably doped by Fe and Co. Our study shows that Co (BLCT) doping and combined Fe, Co (BLFCT) doping lead to a reduction of the bandgap by more than 1 eV compared to undoped BLT, accompanied by a surprisingly more efficient visible light absorption. Both BLCT and BLFCT films can absorb visible light with a wavelength of up to 500 nm while still exhibiting ferroelectricity, whereas undoped BLT only absorbs UV light with a wavelength of less than 350 nm. Correlated with its bandgap reduction, the BLFCT film shows a photocurrent density enhanced by 25 times compared to that of BLT films. Density functional theory calculations indicate that the bandgap contraction is caused by the formation of new energy states below the conduction bands due to intermixed transition metal dopants (Fe, Co) in BLT. This mechanism of tuning the bandgap by simple doping can be applied to other wide-bandgap complex oxides, thereby enabling their use in solar energy conversion or optoelectronic applications. PMID:27313099

  17. Converse magnetoelectric effect via strain-driven magnetization reorientations in ultrathin ferromagnetic films on ferroelectric substrates

    NASA Astrophysics Data System (ADS)

    Pertsev, N. A.

    2015-07-01

    A phenomenological theory is developed for the strain-driven magnetization reorientations occurring in ultrathin ferromagnetic films coupled to ferroelectric substrates experiencing electric-field-induced piezoelectric deformations. The theory takes into account the surface/interface magnetic anisotropy playing an important role in the energetics of such films and first describes the thickness-driven spin reorientation transitions emerging in the presence of substrate-induced lattice strains. Then the threshold and critical intensities of the electric field created in a ferroelectric substrate are calculated, at which different magnetic states acquire the same energy or become unstable in a strained ferromagnetic overlayer. To demonstrate stability ranges of various possible magnetization orientations, we introduce magnetoelectric orientational diagrams, where the electric-field intensity and film thickness are employed as two variables. Such diagrams are constructed for ultrathin Ni, Fe, and F e60C o40 films coupled to single crystals of classical and relaxor ferroelectrics. The inspection of these diagrams shows that the use of multiferroic hybrids comprising ultrathin ferromagnetic films significantly enlarges the range of ferroic materials suitable for experimental observations of the strain-mediated converse magnetoelectric effect.

  18. Electric-field-induced local and mesoscale structural changes in polycrystalline dielectrics and ferroelectrics

    SciTech Connect

    Usher, Tedi -Marie; Levin, Igor; Daniels, John E.; Jones, Jacob L.

    2015-10-01

    In this study, the atomic-scale response of dielectrics/ferroelectrics to electric fields is central to their functionality. Here we introduce an in situ characterization method that reveals changes in the local atomic structure in polycrystalline materials under fields. The method employs atomic pair distribution functions (PDFs), determined from X-ray total scattering that depends on orientation relative to the applied field, to probe structural changes over length scales from sub-Ångstrom to several nanometres. The PDF is sensitive to local ionic displacements and their short-range order, a key uniqueness relative to other techniques. The method is applied to representative ferroelectrics, BaTiO3 and Na½Bi½TiO3, and dielectric SrTiO3. For Na½Bi½TiO3, the results reveal an abrupt field-induced monoclinic to rhombohedral phase transition, accompanied by ordering of the local Bi displacements and reorientation of the nanoscale ferroelectric domains. For BaTiO3 and SrTiO3, the local/nanoscale structural changes observed in the PDFs are dominated by piezoelectric lattice strain and ionic polarizability, respectively.

  19. Upconversion luminescence, ferroelectrics and piezoelectrics of Er Doped SrBi4Ti4O15

    NASA Astrophysics Data System (ADS)

    Peng, Dengfeng; Zou, Hua; Xu, Chaonan; Wang, Xusheng; Yao, Xi; Lin, Jian; Sun, Tiantuo

    2012-12-01

    Er3+ doped SrBi4Ti4O15 (SBT) bismuth layered-structure ferroelectric ceramics were synthesized by the traditional solid-state method, and their upconversion photoluminescent (UC) properties were investigated as a function of Er3+ concentration and incident pump power. Green (555 nm) and red (670 nm) emission bands were obtained under 980 nm excitation at room temperature, which corresponded to the radiative transitions from 4S3/2, and 4F9/2 to 4I15/2, respectively. The emission color of the samples could be changed with moderating the doping concentrations. The dependence of UC intensity on pumping power indicated a two-photon emission process. Studies on dielectric properties indicated that the introduction of Er increased the ferroelectric-paraelectric phase transition temperature (Tc) of SBT, thus making this ceramic suitable for piezoelectric sensor applications at higher temperatures. Piezoelectric measurement showed that the doped SBT had a relative higher piezoelectric constant d33 compared with the non-doped ceramics. The thermal annealing behaviors of the doped sample revealed a stable piezoelectric property. The doped SBT showed bright UC emission while simultaneously having increased Tc and d33. As a multifunctional material, Er doped SBT ferroelectric oxide showed great potential in application of sensor, future optical-electro integration and coupling devices.

  20. Giant photovoltaic effect of ferroelectric domain walls in perovskite single crystals

    PubMed Central

    Inoue, Ryotaro; Ishikawa, Shotaro; Imura, Ryota; Kitanaka, Yuuki; Oguchi, Takeshi; Noguchi, Yuji; Miyayama, Masaru

    2015-01-01

    The photovoltaic (PV) effect in polar materials offers great potential for light-energy conversion that generates a voltage beyond the bandgap limit of present semiconductor-based solar cells. Ferroelectrics have received renewed attention because of the ability to deliver a high voltage in the presence of ferroelastic domain walls (DWs). In recent years, there has been considerable debate over the impact of the DWs on the PV effects, owing to lack of information on the bulk PV tensor of host ferroelectrics. In this article, we provide the first direct evidence of an unusually large PV response induced by ferroelastic DWs—termed ‘DW’-PV effect. The precise estimation of the bulk PV tensor in single crystals of barium titanate enables us to quantify the giant PV effect driven by 90° DWs. We show that the DW-PV effect arises from an effective electric field consisting of a potential step and a local PV component in the 90° DW region. This work offers a starting point for further investigation into the DW-PV effect of alternative systems and opens a reliable route for enhancing the PV properties in ferroelectrics based on the engineering of domain structures in either bulk or thin-film form. PMID:26443381