Switchable and Tunable Bulk Acoustic Wave Devices Based on Ferroelectric Material

NASA Astrophysics Data System (ADS)

Mansour, Almonir

The explosive development of personal communications systems, navigation, satellite communications as well as personal computer and data processing systems together with the constant demand for higher speeds and larger bandwidths has driven fabrication technology to its limits. This, in turn, necessitates the development of novel functional materials for the fabrication of devices with superior performance and higher capacity at reduced manufacturing costs. Ferroelectric materials such as barium strontium titanate (BST) and strontium titanium oxide (STO) have received more attention by researchers and industry because of their field-induced piezoelectric property. This property gives these types of ferroelectric materials the ability to be switchable and tunable in the presence of an electric field. These features have allowed the ferroelectric materials to be used in many applications such as non-volatile memory and DRAMs, sensors, pyroelectric detectors, and tunable microwave devices. Therefore, with the ever increasing complexity in RF front-end receivers, and the demand for services (which in turn requires more functionalities), ferroelectric bulk acoustic wave (BAW) resonators and filters that are intrinsically switchable and tunable promise to reduce the size and complexity of component parts. In this work, we present the design, fabrication and experimental evaluation of switchable and tunable thin film bulk acoustic wave (BAW) resonators, filters and duplexers for radio frequency (RF) applications. The switchability and tunability of these devices come from utilizing the electrostrictive effect of ferroelectric materials such as barium strontium titanate (BST) with the application of an external DC-bias voltage. The BAW resonators, filters and duplexers in this work were fabricated on different substrates as solidly mounted resonator (SMR) structure with number of periodic layers of silicon dioxide and tantalum oxide as a Bragg reflector in order to

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 MoS 2 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.

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.

Supramolecular ferroelectrics.

PubMed

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.

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

Ferroelectric self-assembled molecular materials showing both rectifying and switchable conductivity

PubMed Central

Gorbunov, Andrey V.; Garcia Iglesias, Miguel; Guilleme, Julia; Cornelissen, Tim D.; Roelofs, W. S. Christian; Torres, Tomas; González-Rodríguez, David; Meijer, E. W.; Kemerink, Martijn

2017-01-01

Advanced molecular materials that combine two or more physical properties are typically constructed by combining different molecules, each being responsible for one of the properties required. Ideally, single molecules could take care of this combined functionality, provided they are self-assembled correctly and endowed with different functional subunits whose strong electronic coupling may lead to the emergence of unprecedented and exciting properties. We present a class of disc-like semiconducting organic molecules that are functionalized with strong dipolar side groups. Supramolecular organization of these materials provides long-range polar order that supports collective ferroelectric behavior of the side groups as well as charge transport through the stacked semiconducting cores. The ferroelectric polarization in these supramolecular polymers is found to couple to the charge transport and leads to a bulk conductivity that is both switchable and rectifying. An intuitive model is developed and found to quantitatively reproduce the experimental observations. In a larger perspective, these results highlight the possibility of modulating material properties using the large electric fields associated with ferroelectric polarization. PMID:28975150

Ferroelectric or non-ferroelectric: Why so many materials exhibit “ferroelectricity” on the nanoscale

DOE PAGES

Vasudevan, Rama K.; Balke, Nina; Maksymovych, Peter; ...

2017-05-01

Here, ferroelectric materials have remained one of the major focal points of condensed matter physics and materials science for over 50 years. In the last 20 years, the development of voltage-modulated scanning probe microscopy techniques, exemplified by Piezoresponse force microscopy (PFM) and associated time- and voltage spectroscopies, opened a pathway to explore these materials on a single-digit nanometer level. Consequently, domain structures and walls and polarization dynamics can now be imaged in real space. More generally, PFM has allowed studying electromechanical coupling in a broad variety of materials ranging from ionics to biological systems.

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.

Ferroelectric materials for applications in sensor protection

NASA Astrophysics Data System (ADS)

Bhalla, Amar S.; Cross, L. Eric

1995-07-01

The focus of this program has been upon producing and characterizing new functional materials whose properties can be fine tuned to provide eye sensor protection against laser threats and to suit a range of optoelectronic device applications. Material systems that maximize orientational anisotropy (for use in scattering mode systems) and systems that minimize orientational anisotropy (for use in high field modulators and field induced photorefractive applications) were both approached. Relaxor ferroelectric tungsten bronze single crystals (Sr,Ba)Nb2O6 and (Pb,Ba)Nb2O6 solid solution families and relaxor ferroelectric perovskite (1-x)Pb(Mg(1/3)Nb(2/3))O(3-x)PbTiO3 (PMN-PT) families, were studied extensively. The unique capabilities of a laser heated pedestal growth (LHPG) system were utilized for growth of new materials in single crystal fiber form that produces crystals of long interaction length for optical wave in the crystal and high crystal perfection with maximized properties along chosen directions. Hot uniaxial pressing, hot forging, or appropriate solid state reaction processing methods were used to produce transparent polycrystalline ceramics to provide low scattering, high anisotropy ceramics or high scattering, high anisotropy ceramics. This final report summarizes significant results produced from this program through combination of experimental and crystal chemistry approaches in this field, delineates conclusions drawn from the research, and provides recommendations for future research.

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.

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.

Nanomechanics of Ferroelectric Thin Films and Heterostructures

DOE Office of Scientific and Technical Information (OSTI.GOV)

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.more » 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.« less

Retention of intermediate polarization states in ferroelectric materials enabling memories for multi-bit data storage

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhao, Dong; Asadi, Kamal; Blom, Paul W. M.

A homogeneous ferroelectric single crystal exhibits only two remanent polarization states that are stable over time, whereas intermediate, or unsaturated, polarization states are thermodynamically instable. Commonly used ferroelectric materials however, are inhomogeneous polycrystalline thin films or ceramics. To investigate the stability of intermediate polarization states, formed upon incomplete, or partial, switching, we have systematically studied their retention in capacitors comprising two classic ferroelectric materials, viz. random copolymer of vinylidene fluoride with trifluoroethylene, P(VDF-TrFE), and Pb(Zr,Ti)O{sub 3}. Each experiment started from a discharged and electrically depolarized ferroelectric capacitor. Voltage pulses were applied to set the given polarization states. The retention wasmore » measured as a function of time at various temperatures. The intermediate polarization states are stable over time, up to the Curie temperature. We argue that the remarkable stability originates from the coexistence of effectively independent domains, with different values of polarization and coercive field. A domain growth model is derived quantitatively describing deterministic switching between the intermediate polarization states. We show that by using well-defined voltage pulses, the polarization can be set to any arbitrary value, allowing arithmetic programming. The feasibility of arithmetic programming along with the inherent stability of intermediate polarization states makes ferroelectric materials ideal candidates for multibit data storage.« less

Ferroelectrics for semiconductor devices

NASA Astrophysics Data System (ADS)

Sayer, M.; Wu, Z.; Vasant Kumar, C. V. R.; Amm, D. T.; Griswold, E. M.

1992-11-01

The technology for the implementation of the integration of thin film ferroelectrics with silicon processing for various devices is described, and factors affecting the integration of ferroelectric films with semiconductor processing are discussed. Consideration is also given to film properties, the properties of electrode materials and structures, and the phenomena of ferroelectric fatigue and aging. Particular attention is given to the nonmemory device application of ferroelectrics.

Photostriction in ferroelectric and multiferroic materials from first principles

NASA Astrophysics Data System (ADS)

Paillard, Charles

The so-called Bulk Photovoltaic Effect (BPVE), occurring in materialslacking inversion symmetry, has attracted interest for the design of new solar cells. Hence, non-centrosymmetry of ferroelectrics makes themnatural candidates to the design of suchsolar cells. Itis also fundamental to their piezoelectric properties, i . e . the coupling of their electric polarization to strain. Therefore, ferroelectrics offer a natural route towards the realization of light-induced actuators among the class of photostrictive materials. Experimental evidences towards this goal have appeared, with intense studies of the photostriction in bismuth ferrite, in which both thesteady state response andthe transientgiant shear strain induced by femtoseconds laser pulses wereattributed to the conjunction of the BPVE and the piezoelectric effect. However, theory has not investigated the coupling of light with electromechanical properties of ferroelectrics on a microscopic scale. To tackle this problem, we employ a Δ-SCF scheme in which the occupation numbers of the Kohn-Sham orbitals are constrained. We apply this method to various prototypical ferroelectric and multiferroic materials, such as bismuth ferrite. This scheme yields a photostrictioneffect of the same order of magnitude than the ones recently observed. It also predicts a strong dependence of photostrictive response on both the reached conduction state and the crystallographic direction (along which this effect is determined). In particular, according to our results, BFO should shrink along its pseudo-cubic and polarization axes, with the pseudo-cubic angle getting closer to 90°, while the directions perpendicular to the polarization, such as [110]pc, stretches under excitation of electrons in the conduction band. Another of our main results is that photostriction is found to originate from the combination of screening of the polarization at the unit cell scale by the photoexcited carriers, and converse piezoelectric effect. We

Flexible ferroelectric organic crystals

DOE PAGES

Owczarek, Magdalena; Hujsak, Karl A.; Ferris, Daniel P.; ...

2016-10-13

Flexible organic materials possessing useful electrical properties, such as ferroelectricity, are of crucial importance in the engineering of electronic devices. But, until now, 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. 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.more » 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.« less

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 PbZr 0.3Ti 0.7O 3and 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.

General Nonlinear Ferroelectric Model v. Beta

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dong, Wen; Robbins, Josh

2017-03-14

The purpose of this software is to function as a generalized ferroelectric material model. The material model is designed to work with existing finite element packages by providing updated information on material properties that are nonlinear and dependent on loading history. The two major nonlinear phenomena this model captures are domain-switching and phase transformation. The software itself does not contain potentially sensitive material information and instead provides a framework for different physical phenomena observed within ferroelectric materials. The model is calibrated to a specific ferroelectric material through input parameters provided by the user.

New iron-based multiferroics with improper ferroelectricity

NASA Astrophysics Data System (ADS)

Peng, Jin; Zhang, Yang; Lin, Ling-Fang; Lin, Lin; Liu, Meifeng; Liu, Jun-Ming; Dong, Shuai

2018-06-01

In this contribution to the special issue on magnetoelectrics and their applications, we focus on some single phase multiferroics, which have been theoretically predicted and/or experimentally discovered by the authors in recent years. In these materials, iron is the common core element. However, these materials are conceptually different from the mostly-studied BiFeO3, since their ferroelectricity is improper. Our reviewed materials are not simply repeating one magnetoelectric mechanism, but cover multiple branches of improper ferroelectricity, including the magnetism-driven ferroelectrics, geometric ferroelectric, as well as electronic ferroelectric driven by charge ordering. In this sense, these iron-based improper ferroelectrics can be an encyclopaedic playground to explore the comprehensive physics of multiferroics and magnetoelectricity. Furthermore, the unique characteristics of iron’s 3d orbitals make some of their magnetoelectric properties quite prominent, comparing with the extensively-studied Mn-based improper multiferroics. In addition, these materials establish the crossover between multiferroics and other fields of functional materials, which enlarges the application scope of multiferroics.

Recent patents on perovskite ferroelectric nanostructures.

PubMed

Zhu, Xinhua

2009-01-01

Ferroelectric oxide materials with a perovskite structure have promising applications in electronic devices such as random access memories, sensors, actuators, infrared detectors, and so on. Recent advances in science and technology of ferroelectrics have resulted in the feature sizes of ferroelectric-based electronic devices entering into nanoscale dimensions. At nanoscale perovskite ferroelectric materials exhibit a pronounced size effect manifesting itself in a significant deviation of the properties of low-dimensional structures from the bulk and film counterparts. One-dimensional perovskite ferroelectric nanotube/nanowire systems, offer fundamental scientific opportunities for investigating the intrinsic size effects in ferroelectrics. In the past several years, much progress has been made both in fabrication and physical property testing of perovskite ferroelectric nanostructures. In the first part of this paper, the recent patents and literatures for fabricating ferroelectric nanowires, nanorods, nanotubes, and nanorings with promising features, are reviewed. The second part deals with the recent advances on the physical property testing of perovskite ferroelectric nanostructures. The third part summarizes the recently patents and literatures about the microstructural characterizations of perovskite ferroelectric nanostructures, to improve their crystalline quality, morphology and uniformity. Finally, we conclude this review with personal perspectives towards the potential future developments of perovskite ferroelectric nanostructures.

New classes of piezoelectrics, ferroelectrics, and antiferroelectrics by first-principles high-throughput materials design

NASA Astrophysics Data System (ADS)

Bennett, Joseph

2013-03-01

Functional materials, such as piezoelectrics, ferroelectrics, and antiferroelectrics, exhibit large changes with applied fields and stresses. This behavior enables their incorporation into a wide variety of devices in technological fields such as energy conversion/storage and information processing/storage. Discovery of functional materials with improved performance or even new types of responses is thus not only a scientific challenge, but can have major impacts on society. In this talk I will review our efforts to uncover new families of functional materials using a combined crystallographic database/high-throughput first-principles approach. I will describe our work on the design and discovery of thousands of new functional materials, specifically the LiAlSi family as piezoelectrics, the LiGaGe family as ferroelectrics, and the MgSrSi family as antiferroelectrics.

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.

Materials being simultaneously ferroelectric, ferromagnetic, ferrotoroidic and ferroelastic

NASA Astrophysics Data System (ADS)

Schmid, Hans

2001-03-01

For the simultaneous occurrence of ferroelectric, ferromagnetic, ferrotoroidic and ferroelastic properties in the same phase, certain stringent symmetry and structural requirements have to be met. Among the 122 Shubnikov point groups 31 are allowing a spontaneous polarization, 31 a spontaneous magnetization and 31 a spontaneous toroidal moment, but only 9 groups allow all three types of vector property at the same time(H. Schmid, Ferroelectrics, in press). In practice this number is further reduced to 6 groups which are permitting "weak ferromagnetism", the most probable type of ferromagnetism found in ferroelectrics with magnetic superexchange interaction nets. The additional occurrence of ferroelasticity is possible for certain prototype phase/ferroic phase pairs of point group (= "Aizu species") only. In addition, one of the mentioned 9 point groups excludes ferroelasticity and allows a co-elastic phase transition only. - The presence or absence of full or partial coupling between the named primary ferroic spontaneous quantities and the resulting possibilities of coupled or non-coupled ferroic domain switching and reorientation are also ruled by the type of species(H. Schmid, Ferroelectrics, 221, 9-17 (1999)). - Apart from a few exceptions, multiferroic phases being simultaneously ferroelectric, ferromagnetic, ferrotoroidic and ferroelastic, are so far well established in the crystal family of boracites M_3B_7O_13X only, where M stands for a bivalent 3d-transition metal ion and X for an ion of the halogens Cl, Br or I(H. Schmid, Ferroelectrics, 162, 317-338 (1994)). - A toroidal moment changes sign both under time reversal and space inversion and has the same symmetry as current density, anapole moment, velocity, etc. First experimental evidence of the presence of a spontaneous toroidal moment in boracites is suggested by phenomenological theory on the basis of measured anomalies of the linear magnetoelectric effect(D.G. Sannikov, Ferroelectrics, 219, 177 (1998

Characterization Of Graphene-Ferroelectric Superlattice Hybrid Devices

NASA Astrophysics Data System (ADS)

Yusuf, Mohammed; Du, Xu; Dawber, Matthew

2013-03-01

Ferroelectric materials possess a spontaneous electrical polarization, which can be controlled by an electric field. A good interface between ferroelectric surface and graphene sheets can introduce a new generation of multifunctional devices, in which the ferroelectric material can be used to control the properties of graphene. In our approach, problems encountered in previous efforts to combine ferroelectric/carbon systems are overcome by the use of artificially layered superlattice materials grown in the form of epitaxial thin films. In these materials the phase transition temperature and dielectric response of the material can be tailored, allowing us to avoid polarization screening by surface absorbates, whilst maintaining an atomically smooth surface and optimal charge doping properties. Using ferroelectric PbTiO3/SrTiO3 superlattices, we have shown ultra-low-voltage operation of graphene field effect devices within +/- 1 V at room temperature. The switching of the graphene field effect transistors is characterized by pronounced resistance hysteresis, suitable for ultra-fast non-volatile electronics. Low temperature characterization confirmed that the coercive field required for the ferroelectric domain switching increases significantly with decreasing temperatures. National Science Foundation (NSF) (grant number 1105202)

Ferroelectric Phase Transformations for Energy Conversion and Storage Applications

NASA Astrophysics Data System (ADS)

Jo, Hwan Ryul

Ferroelectric materials possess a spontaneous polarization and actively respond to external mechanical, electrical, and thermal loads. Due to their coupled behavior, ferroelectric materials are used in products such as sensors, actuators, detectors, and transducers. However, most current applications rely on low-energy conversion that involves low magnitude fields. They utilize the low-field linear properties of ferroelectric materials (piezoelectric, pyroelectric) and do not take full advantage of the large-field nonlinear behavior (irreversible domain wall motion, phase transformations) that can occur in ferroelectric materials. When external fields exceed a certain critical level, a structural transformation of the crystal can occur. These phase transformations are accompanied by a much larger response than the linear piezoelectric and pyroelectric responses, by as much as a multiple of ten times in the magnitude. This makes the non-linear behavior in ferroelectric materials promising for energy harvesting and energy storage technologies which will benefit from large-energy conversion. Yet, the ferroelectric phase transformation behavior under large external fields have been less studied and only a few studies have been directed at utilizing this large material response in applications. This dissertation addresses the development ferroelectric phase transformation-based applications, with particular focus on the materials. Development of the ferroelectric phase transformation-based applications was approached in several steps. First, the phase transformation behavior was fully characterized and understood by measuring the phase transformation responses under mechanical, electrical, thermal, and combined loads. Once the behavior was well characterized, systems level applications were addressed. This required assessing the effect of the phase transformation behavior on system performance. The performance of ferroelectric devices is strongly dependent on material

Stress-induced reversible and irreversible ferroelectric domain switching

NASA Astrophysics Data System (ADS)

Chen, Zibin; Huang, Qianwei; Wang, Feifei; Ringer, Simon P.; Luo, Haosu; Liao, Xiaozhou

2018-04-01

Ferroelectric materials have been extensively explored for applications in electronic devices because of their ferroelectric/ferroelastic domain switching behaviour under electric bias or mechanical stress. Recent findings on applying mechanical loading to manipulate reversible logical signals in non-volatile ferroelectric memory devices make ferroelectric materials more attractive to scientists and engineers. However, the dynamical microscopic structural behaviour of ferroelectric domains under stress is not well understood, which limits the applications of ferroelectric/ferroelastic switching in memory devices. Here, the kinetics of reversible and irreversible ferroelectric domain switching induced by mechanical stress in relaxor-based ferroelectrics was explored. In-situ transmission electron microscopy investigation revealed that 90° ferroelastic and 180° ferroelectric domain switching can be induced by low and high mechanical stresses. The nucleation and growth of nanoscale domains overwhelm the defect-induced pinning effect on the stable micro-domain walls. This study provides deep insights for exploring the mechanical kinetics for ferroelectric/ferroelastic domains and a clear pathway to overcome the domain pinning effect of defects in ferroelectrics.

Ultrahigh density ferroelectric storage and lithography by high order ferroic switching

DOEpatents

Kalinin, Sergei V.; Baddorf, Arthur P.; Lee, Ho Nyung; Shin, Junsoo; Gruverman, Alexei L.; Karapetian, Edgar; Kachanov, Mark

2007-11-06

A method for switching the direction of polarization in a relatively small domain in a thin-film ferroelectric material whose direction of polarization is oriented normal to the surface of the material involves a step of moving an electrically-chargeable tip into contact with the surface of the ferroelectric material so that the direction of polarization in a region adjacent the tip becomes oriented in a preselected direction relative to the surface of the ferroelectric material. The tip is then pressed against the surface of the ferroelectric material so that the direction of polarization of the ferroelectric material within the area of the ferroelectric material in contact with the tip is reversed under the combined effect of the compressive influence of the tip and electric bias.

Differentiating Ferroelectric and Nonferroelectric Electromechanical Effects with Scanning Probe Microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Balke, Nina; Maksymovych, Petro; Jesse, Stephen

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

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

Quantum mechanical studies of complex ferroelectric perovskites

NASA Astrophysics Data System (ADS)

Ramer, Nicholas John

In many electronic device applications, there is a need to interconvert electrical energy and other types of energy. Ferroelectric materials, which possess a voltage-dependent polarization, can enable this energy conversion process. Because of the broad interest in ferroelectric materials for these devices, there is a critical research effort, both experimental and theoretical, to understand these materials and aid in the development of materials with improved properties. This thesis presents detailed quantum mechanical investigations of the behavior of a complex ferroelectric perovskite under applied stress. In particular, we have chosen to study the solid solution PbZr1-xTix O3 (PZT). Since the study of ferroelectricity involves understanding both its structural and electronic signatures in materials, it has necessitated the development of a novel theoretical technique which improves the accuracy of the pseudopotentials used in our density functional theory calculations as well as a new method for constructing three-dimensional atomistic responses to small amounts of external stress. To examine the material's behavior under larger amounts of stress, we have studied the behavior of a composition of PZT lying near a structural phase boundary. On either side of the phase boundary, the material is characterized by a different polarization direction and may easily be switched between phases by applying external stress. In addition to stress-induced phase transitions, most ferroelectric materials also have composition dependent phase boundaries. Since different compositions of PZT would require increased computational effort, we have formulated an improved virtual crystal approach that makes tractable the study of the entire composition range. Using this method, we have been able to show for the first time via first-principles calculations, a composition dependent phase transition in a ferroelectric material. This thesis has accomplished three important goals: new

Robust ferroelectricity in two-dimensional SbN and BiP.

PubMed

Liu, Chang; Wan, Wenhui; Ma, Jie; Guo, Wei; Yao, Yugui

2018-05-03

Based on first-principles calculations, we discover two new two-dimensional (2D) ferroelectric materials SbN and BiP. Both of them are stable in a phosphorene-like structure and maintain their ferroelectricity above room temperature. Till date, SbN has the largest in-plane spontaneous polarization of about 7.81 × 10-10 C m-1 ever found in 2D ferroelectric materials, and it can retain its ferroelectricity until melting at about 1700 K. The spontaneous polarizations and switching barriers can easily be tuned by strains. Additionally, the ferroelectricity can still be maintained in their multilayers. These advantages make SbN and BiP promising candidate materials for future integrated ferroelectric devices.

The anhysteretic polarisation of ferroelectrics

NASA Astrophysics Data System (ADS)

Kaeswurm, B.; Segouin, V.; Daniel, L.; Webber, K. G.

2018-02-01

Measurement and calculation of anhysteretic curves is a well-established method in the field of magnetic materials and is applied to ferroelectric materials here. The anhysteretic curve is linked to a stable equilibrium state in the domain structure, and ignores dissipative effects related to mechanisms such as domain wall pinning. In this study, an experimental method for characterising the anhysteretic behaviour of ferroelectrics is presented, which is subsequently used to determine the anhysteretic polarisation response of polycrystalline barium titanate and a doped lead zirconate titanate composition at room temperature. Various external parameters, such as electric field, stress, and temperature, can significantly affect ferroelectric behaviour. Ferroelectric hysteresis curves can assess the importance of such effects but cannot distinguish their contribution on the different intrinsic and extrinsic mechanisms involved in ferroelectric behaviour. In this work, the influence of compressive stress on the anhysteretic polarisation is measured and discussed. The comparison of the polarization loop to the anhysteretic curve under compressive stress elucidates the effects on the stable equilibrium domain configuration and dynamic effects associated to dissipation.

The origin of the residual conductivity of GaN films on ferroelectric materials

NASA Astrophysics Data System (ADS)

Lee, Kyoung-Keun; Cai, Zhuhua; Ziemer, Katherine; Doolittle, William Alan

2009-08-01

In this paper, the origin of the conductivity of GaN films grown on ferroelectric materials was investigated using XPS, AES, and XRD analysis tools. Depth profiles confirmed the existence of impurities in the GaN film originating from the substrates. Bonding energy analysis from XPS and AES verified that oxygen impurities from the substrates were the dominant origin of the conductivity of the GaN film. Furthermore, Ga-rich GaN films have a greater chance of enhancing diffusion of lithium oxide from the substrates, resulting in more substrate phase separation and a wider inter-mixed region confirmed by XRD. Therefore, the direct GaN film growth on ferroelectric materials causes impurity diffusion from the substrates, resulting in highly conductive GaN films. Future work needs to develop non-conductive buffer layers for impurity suppression in order to obtain highly resistive GaN films.

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.

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.

Ferroelectric negative capacitance domain dynamics

NASA Astrophysics Data System (ADS)

Hoffmann, Michael; Khan, Asif Islam; Serrao, Claudy; Lu, Zhongyuan; Salahuddin, Sayeef; Pešić, Milan; Slesazeck, Stefan; Schroeder, Uwe; Mikolajick, Thomas

2018-05-01

Transient negative capacitance effects in epitaxial ferroelectric Pb(Zr0.2Ti0.8)O3 capacitors are investigated with a focus on the dynamical switching behavior governed by domain nucleation and growth. Voltage pulses are applied to a series connection of the ferroelectric capacitor and a resistor to directly measure the ferroelectric negative capacitance during switching. A time-dependent Ginzburg-Landau approach is used to investigate the underlying domain dynamics. The transient negative capacitance is shown to originate from reverse domain nucleation and unrestricted domain growth. However, with the onset of domain coalescence, the capacitance becomes positive again. The persistence of the negative capacitance state is therefore limited by the speed of domain wall motion. By changing the applied electric field, capacitor area or external resistance, this domain wall velocity can be varied predictably over several orders of magnitude. Additionally, detailed insights into the intrinsic material properties of the ferroelectric are obtainable through these measurements. A new method for reliable extraction of the average negative capacitance of the ferroelectric is presented. Furthermore, a simple analytical model is developed, which accurately describes the negative capacitance transient time as a function of the material properties and the experimental boundary conditions.

Current and surface charge modified hysteresis loops in ferroelectric thin films

DOE PAGES

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

2015-08-19

Polarization domains in ferroelectric materials and the ability to orient them with an external electric field lead to the development of a variety of applications from information storage to actuation. The development of piezoresponse force microscopy (PFM) has enabled researchers to investigate ferroelectric domains and ferroelectric domain switching on the nanoscale, which offers a pathway to study structure-function relationships in this important material class. Due to its commercial availability and ease of use, PFM has become a widely used research tool. However, measurement artifacts, i.e., alternative signal origins besides the piezoelectric effect are barely discussed or considered. This becomes especiallymore » important for materials with a small piezoelectric coefficient or materials with unknown ferroelectric properties, including non-ferroelectric materials. Here, the role of surface charges and current flow during PFM measurements on classical ferroelectrics are discussed and it will be shown how they alter the PFM hysteresis loop shape. This will help to better address alternative signal origins in PFM-type experiments and offer a pathway to study additional phenomena besides ferroelectricity.« less

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

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.

Thin Layer Composite Unimorph Ferroelectric Driver and Sensor

NASA Technical Reports Server (NTRS)

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

1995-01-01

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.

Highly Effective Ferroelectric Materials and Technologies for Their Processing

NASA Astrophysics Data System (ADS)

Reznichenko, L. A.; Verbenko, I. A.; Andryushina, I. N.; Andryushin, K. P.; Pavelko, A. A.; Pavlenko, A. A.; Shilkina, L. A.; Dudkina, S. I.; Sudykov, H. A.; Abubakarov, A. G.; Talanov, M. V.; Gershenovich, V. V.; Miller, A. I.; Alyoshin, V. A.

The basis of most commonly ferroelectric ceramic materials (FECMs) used in the modern industry is solid solutions of complex lead oxides. It should be noted that due to significant toxicity of lead compounds there has been an intensive search for alternative materials in recent years. Such efforts resulted from the introduction of a new legislative base aiming at environmental protection [Directive 2002/95/EC of the European Parliament and Council by 27 January 2003 on the restriction of the use of certain hazardous substances in electronic equipment]. In the Research Institute of Physics of SFedU much work has been done for about 30 years to investigate and develop of the environmentally friendly FECMs on the basis of alkali niobate metals. Nowadays such materials are finding more applications in the defense industry rather than other industries. Therefore it is extremely important to promote the production of lead low-cost materials and develop new FECMs.

Prediction of intrinsic two-dimensional ferroelectrics in In2Se3 and other III2-VI3 van der Waals materials.

PubMed

Ding, Wenjun; Zhu, Jianbao; Wang, Zhe; Gao, Yanfei; Xiao, Di; Gu, Yi; Zhang, Zhenyu; Zhu, Wenguang

2017-04-07

Interest in two-dimensional (2D) van der Waals materials has grown rapidly across multiple scientific and engineering disciplines in recent years. However, ferroelectricity, the presence of a spontaneous electric polarization, which is important in many practical applications, has rarely been reported in such materials so far. Here we employ first-principles calculations to discover a branch of the 2D materials family, based on In 2 Se 3 and other III 2 -VI 3 van der Waals materials, that exhibits room-temperature ferroelectricity with reversible spontaneous electric polarization in both out-of-plane and in-plane orientations. The device potential of these 2D ferroelectric materials is further demonstrated using the examples of van der Waals heterostructures of In 2 Se 3 /graphene, exhibiting a tunable Schottky barrier, and In 2 Se 3 /WSe 2 , showing a significant band gap reduction in the combined system. These findings promise to substantially broaden the tunability of van der Waals heterostructures for a wide range of applications.

Prediction of intrinsic two-dimensional ferroelectrics in In2Se3 and other III2-VI3 van der Waals materials

PubMed Central

Ding, Wenjun; Zhu, Jianbao; Wang, Zhe; Gao, Yanfei; Xiao, Di; Gu, Yi; Zhang, Zhenyu; Zhu, Wenguang

2017-01-01

Interest in two-dimensional (2D) van der Waals materials has grown rapidly across multiple scientific and engineering disciplines in recent years. However, ferroelectricity, the presence of a spontaneous electric polarization, which is important in many practical applications, has rarely been reported in such materials so far. Here we employ first-principles calculations to discover a branch of the 2D materials family, based on In2Se3 and other III2-VI3 van der Waals materials, that exhibits room-temperature ferroelectricity with reversible spontaneous electric polarization in both out-of-plane and in-plane orientations. The device potential of these 2D ferroelectric materials is further demonstrated using the examples of van der Waals heterostructures of In2Se3/graphene, exhibiting a tunable Schottky barrier, and In2Se3/WSe2, showing a significant band gap reduction in the combined system. These findings promise to substantially broaden the tunability of van der Waals heterostructures for a wide range of applications. PMID:28387225

Prediction of intrinsic two-dimensional ferroelectrics in In2Se3 and other III2-VI3 van der Waals materials

NASA Astrophysics Data System (ADS)

Ding, Wenjun; Zhu, Jianbao; Wang, Zhe; Gao, Yanfei; Xiao, Di; Gu, Yi; Zhang, Zhenyu; Zhu, Wenguang

2017-04-01

Interest in two-dimensional (2D) van der Waals materials has grown rapidly across multiple scientific and engineering disciplines in recent years. However, ferroelectricity, the presence of a spontaneous electric polarization, which is important in many practical applications, has rarely been reported in such materials so far. Here we employ first-principles calculations to discover a branch of the 2D materials family, based on In2Se3 and other III2-VI3 van der Waals materials, that exhibits room-temperature ferroelectricity with reversible spontaneous electric polarization in both out-of-plane and in-plane orientations. The device potential of these 2D ferroelectric materials is further demonstrated using the examples of van der Waals heterostructures of In2Se3/graphene, exhibiting a tunable Schottky barrier, and In2Se3/WSe2, showing a significant band gap reduction in the combined system. These findings promise to substantially broaden the tunability of van der Waals heterostructures for a wide range of applications.

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.

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

Alloying n-Butylamine into CsPbBr3 to Give a Two-Dimensional Bilayered Perovskite Ferroelectric Material.

PubMed

Wu, Zhenyue; Ji, Chengmin; Li, Lina; Kong, Jintao; Sun, Zhihua; Zhao, Sangen; Wang, Sasa; Hong, Maochun; Luo, Junhua

2018-05-11

Cesium-lead halide perovskites (e.g. CsPbBr 3 ) have gained attention because of their rich physical properties, but their bulk ferroelectricity remains unexplored. Herein, by alloying flexible organic cations into the cubic CsPbBr 3 , we design the first cesium-based two-dimensional (2D) perovskite ferroelectric material with both inorganic alkali metal and organic cations, (C 4 H 9 NH 3 ) 2 CsPb 2 Br 7 (1). Strikingly, 1 shows a high Curie temperature (T c =412 K) above that of BaTiO 3 (ca. 393 K) and notable spontaneous polarization (ca. 4.2 μC cm -2 ), triggered by not only the ordering of organic cations but also atomic displacement of inorganic Cs + ions. To our knowledge, such a 2D bilayered Cs + -based metal-halide perovskite ferroelectric material with inorganic and organic cations is unprecedented. 1 also shows photoelectric semiconducting behavior with large "on/off" ratios of photoconductivity (>10 3 ). © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Fei; Zhang, Shujun; Yang, Tiannan

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 propertiesmore » 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.« less

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

DOE PAGES

Li, Fei; Zhang, Shujun; Yang, Tiannan; ...

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 propertiesmore » 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.« less

Manipulating Ferroelectrics through Changes in Surface and Interface Properties

DOE Office of Scientific and Technical Information (OSTI.GOV)

Balke, Nina; Ramesh, Ramamoorthy; Yu, Pu

Ferroelectric materials are used in many applications of modern technologies including information storage, transducers, sensors, tunable capacitors, and other novel device concepts. In many of these applications, the ferroelectric properties, such as switching voltages, piezoelectric constants, or stability of nanodomains, are crucial. For any application, even for material characterization, the material itself needs to be interfaced with electrodes. On the basis of the structural, chemical, and electronic properties of the interfaces, the measured material properties can be determined by the interface. This is also true for surfaces. However, the importance of interfaces and surfaces and their effect on experiments aremore » often neglected, which results in many dramatically different experimental results for nominally identical samples. Therefore, it is crucial to understand the role of the interface and surface properties on internal bias fields and the domain switching process. Here, the nanoscale ferroelectric switching process and the stability of nanodomains for Pb(Zr,Ti)O 3 thin films are investigated by using scanning probe microscopy. Interface and surface properties are modulated through the selection/redesign of electrode materials as well as tuning the surface-near oxygen vacancies, which both can result in changes of the electric fields acting across the sample, and consequently this controls the measured ferroelectric and domain retention properties. By understanding the role of surfaces and interfaces, ferroelectric properties can be tuned to eliminate the problem of asymmetric domain stability by combining the effects of different electrode materials. Lastly, this study forms an important step toward integrating ferroelectric materials in electronic devices.« less

Manipulating Ferroelectrics through Changes in Surface and Interface Properties

DOE PAGES

Balke, Nina; Ramesh, Ramamoorthy; Yu, Pu

2017-10-23

Ferroelectric materials are used in many applications of modern technologies including information storage, transducers, sensors, tunable capacitors, and other novel device concepts. In many of these applications, the ferroelectric properties, such as switching voltages, piezoelectric constants, or stability of nanodomains, are crucial. For any application, even for material characterization, the material itself needs to be interfaced with electrodes. On the basis of the structural, chemical, and electronic properties of the interfaces, the measured material properties can be determined by the interface. This is also true for surfaces. However, the importance of interfaces and surfaces and their effect on experiments aremore » often neglected, which results in many dramatically different experimental results for nominally identical samples. Therefore, it is crucial to understand the role of the interface and surface properties on internal bias fields and the domain switching process. Here, the nanoscale ferroelectric switching process and the stability of nanodomains for Pb(Zr,Ti)O 3 thin films are investigated by using scanning probe microscopy. Interface and surface properties are modulated through the selection/redesign of electrode materials as well as tuning the surface-near oxygen vacancies, which both can result in changes of the electric fields acting across the sample, and consequently this controls the measured ferroelectric and domain retention properties. By understanding the role of surfaces and interfaces, ferroelectric properties can be tuned to eliminate the problem of asymmetric domain stability by combining the effects of different electrode materials. Lastly, this study forms an important step toward integrating ferroelectric materials in electronic devices.« less

High-performance ferroelectric and magnetoresistive materials for next-generation thermal detector arrays

NASA Astrophysics Data System (ADS)

Todd, Michael A.; Donohue, Paul P.; Watton, Rex; Williams, Dennis J.; Anthony, Carl J.; Blamire, Mark G.

2002-12-01

This paper discusses the potential thermal imaging performance achievable from thermal detector arrays and concludes that the current generation of thin-film ferroelectric and resistance bolometer based detector arrays are limited by the detector materials used. It is proposed that the next generation of large uncooled focal plane arrays will need to look towards higher performance detector materials - particularly if they aim to approach the fundamental performance limits and compete with cooled photon detector arrays. Two examples of bolometer thin-film materials are described that achieve high performance from operating around phase transitions. The material Lead Scandium Tantalate (PST) has a paraelectric-to-ferroelectric phase transition around room temperature and is used with an applied field in the dielectric bolometer mode for thermal imaging. PST films grown by sputtering and liquid-source CVD have shown merit figures for thermal imaging a factor of 2 to 3 times higher than PZT-based pyroelectric thin films. The material Lanthanum Calcium Manganite (LCMO) has a paramagnetic to ferromagnetic phase transition around -20oC. This paper describes recent measurements of TCR and 1/f noise in pulsed laser-deposited LCMO films on Neodymium Gallate substrates. These results show that LCMO not only has high TCR's - up to 30%/K - but also low 1/f excess noise, with bolometer merit figures at least an order of magnitude higher than Vanadium Oxide, making it ideal for the next generation of microbolometer arrays. These high performance properties come at the expense of processing complexities and novel device designs will need to be introduced to realize the potential of these materials in the next generation of thermal detectors.

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(Zr 0.2Ti 0.8)O3) junction in applied electric field. We revealed anmore » 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.« less

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.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

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 thatmore » 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.« less

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.

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.

Ferroelectric nanostructure having switchable multi-stable vortex states

DOEpatents

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

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.

Targeted Basic Studies of Ferroelectric and Ferroelastic Materials for Piezoelectric Transducer Applications.

DTIC Science & Technology

1983-03-01

PLZT ceramics. Low temperature studies on pure and doped PZTs have given the first clear indi- cation of the intrinsic (averaged) single domain...8217 11 4.0 PYROELECTRIC MATERIALS 27 4.1 Micro Composites 27 4.2 ’ Doped ’ Tungsten Bronze and TGS Structure Single Crystals 28 5.0 FERROELECTRIC...differences in piezo- electric activity, coupling constant and permittivity between differently doped PZTs are extrinsic and freeze out at 4°K. Extending

Ferroelectric symmetry-protected multibit memory cell

DOE PAGES

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

2017-02-08

Here, 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-valuedmore » non-Boolean information technology and target challenges posed by needs of quantum and neuromorphic computing.« less

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.

Proceedings of the 8th International Symposium on Applications of Ferroelectrics

NASA Astrophysics Data System (ADS)

Liu, M.; Safari, A.; Kingon, A.; Haertling, G.

1993-02-01

The eighth International Symposium on the Applications of Ferroelectrics was held in Greenville, SC, on August 30 to Sept 2, 1992. It was attended by approximately 260 scientists and engineers who presented nearly 200 oral and poster papers. The three plenary presentations covered ferroelectric materials which are currently moving into commercial exploitation or have strong potential to do so. These were (1) pyroelectric imaging, (2) ferroelectric materials integrated with silicon for use as micromotors and microsensors and (3) research activity in Japan on high permittivity materials for DRAM's. Invited papers covered such subjects as pyroelectric and electrooptic properties of thin films, photorefractive effects, ferroelectric polymers, piezoelectric transducers, processing of ferroelectrics, domain switching in ferroelectrics, thin film memories, thin film vacuum deposition techniques and the fabrication of chemically prepared PZT and PLZT thin films. The papers continued to reflect the large interest in ferroelectric thin films. It was encouraging that there have been substantial strides made in both the processing and understanding of the films in the last two years. It was equally clear, however, that much still remains to be done before reliable thin film devices will be available in the marketplace.

Design of a terahertz photonic crystal transmission filter containing ferroelectric material.

PubMed

King, Tzu-Chyang; Chen, Jian-Jie; Chang, Kai-Chun; Wu, Chien-Jang

2016-10-10

The ferroelectric material KTaO₃ (KTO) has a very high refractive index, which is advantageous to the photonic crystal (PC) design. KTO polycrystalline crystal has a high extinction coefficient. In this work, we perform a theoretical study of the transmission properties of a PC bandpass filter made of polycrystalline KTO at terahertz (THz) frequencies. Our results show that the defect modes of usual PC narrowband filters no longer exist because of the existence of the high loss. We provide a new PC structure for the high-extinction materials and show that it has defect modes in its transmittance spectra, providing a possible bandpass filter design in the THz region.

Room temperature ferroelectricity in fluoroperovskite thin films.

PubMed

Yang, Ming; Kc, Amit; Garcia-Castro, A C; Borisov, Pavel; Bousquet, E; Lederman, David; Romero, Aldo H; Cen, Cheng

2017-08-03

The NaMnF 3 fluoride-perovskite has been found, theoretically, to be ferroelectric under epitaxial strain becoming a promising alternative to conventional oxides for multiferroic applications. Nevertheless, this fluoroperovskite has not been experimentally verified to be ferroelectric so far. Here we report signatures of room temperature ferroelectricity observed in perovskite NaMnF 3 thin films grown on SrTiO 3 . Using piezoresponse force microscopy, we studied the evolution of ferroelectric polarization in response to external and built-in electric fields. Density functional theory calculations were also performed to help understand the strong competition between ferroelectric and paraelectric phases as well as the profound influences of strain. These results, together with the magnetic order previously reported in the same material, pave the way to future multiferroic and magnetoelectric investigations in fluoroperovskites.

Photoelectron spectroscopic and microspectroscopic probes of ferroelectrics

NASA Astrophysics Data System (ADS)

Tǎnase, Liviu C.; Abramiuc, Laura E.; Teodorescu, Cristian M.

2017-12-01

This contribution is a review of recent aspects connected with photoelectron spectroscopy of free ferroelectric surfaces, metals interfaced with these surfaces, graphene-like layers together with some exemplifications concerning molecular adsorption, dissociations and desorptions occurring from ferroelectrics. Standard photoelectron spectroscopy is used nowadays in correlation with other characterization techniques, such as piezoresponse force microscopy, high resolution transmission electron spectroscopy, and ferroelectric hysteresis cycles. In this work we will concentrate mainly on photoelectron spectroscopy and spectro-microscopy characterization of ferroelectric thin films, starting from atomically clean ferroelectric surfaces of lead zirco-titanate, then going towards heterostructures using this material in combination with graphene-like carbon layers or with metals. Concepts involving charge accumulation and depolarization near surface will be revisited by taking into account the newest findings in this area.

An Automated Ab Initio Framework for Identifying New Ferroelectrics

NASA Astrophysics Data System (ADS)

Smidt, Tess; Reyes-Lillo, Sebastian E.; Jain, Anubhav; Neaton, Jeffrey B.

Ferroelectric materials have a wide-range of technological applications including non-volatile RAM and optoelectronics. In this work, we present an automated first-principles search for ferroelectrics. We integrate density functional theory, crystal structure databases, symmetry tools, workflow software, and a custom analysis toolkit to build a library of known and proposed ferroelectrics. We screen thousands of candidates using symmetry relations between nonpolar and polar structure pairs. We use two search strategies 1) polar-nonpolar pairs with the same composition and 2) polar-nonpolar structure type pairs. Results are automatically parsed, stored in a database, and accessible via a web interface showing distortion animations and plots of polarization and total energy as a function of distortion. We benchmark our results against experimental data, present new ferroelectric candidates found through our search, and discuss future work on expanding this search methodology to other material classes such as anti-ferroelectrics and multiferroics.

Anti-Ferroelectric Ceramics for High Energy Density Capacitors.

PubMed

Chauhan, Aditya; Patel, Satyanarayan; Vaish, Rahul; Bowen, Chris R

2015-11-25

With an ever increasing dependence on electrical energy for powering modern equipment and electronics, research is focused on the development of efficient methods for the generation, storage and distribution of electrical power. In this regard, the development of suitable dielectric based solid-state capacitors will play a key role in revolutionizing modern day electronic and electrical devices. Among the popular dielectric materials, anti-ferroelectrics (AFE) display evidence of being a strong contender for future ceramic capacitors. AFE materials possess low dielectric loss, low coercive field, low remnant polarization, high energy density, high material efficiency, and fast discharge rates; all of these characteristics makes AFE materials a lucrative research direction. However, despite the evident advantages, there have only been limited attempts to develop this area. This article attempts to provide a focus to this area by presenting a timely review on the topic, on the relevant scientific advancements that have been made with respect to utilization and development of anti-ferroelectric materials for electric energy storage applications. The article begins with a general introduction discussing the need for high energy density capacitors, the present solutions being used to address this problem, and a brief discussion of various advantages of anti-ferroelectric materials for high energy storage applications. This is followed by a general description of anti-ferroelectricity and important anti-ferroelectric materials. The remainder of the paper is divided into two subsections, the first of which presents various physical routes for enhancing the energy storage density while the latter section describes chemical routes for enhanced storage density. This is followed by conclusions and future prospects and challenges which need to be addressed in this particular field.

Anti-Ferroelectric Ceramics for High Energy Density Capacitors

PubMed Central

Chauhan, Aditya; Patel, Satyanarayan; Vaish, Rahul; Bowen, Chris R.

2015-01-01

With an ever increasing dependence on electrical energy for powering modern equipment and electronics, research is focused on the development of efficient methods for the generation, storage and distribution of electrical power. In this regard, the development of suitable dielectric based solid-state capacitors will play a key role in revolutionizing modern day electronic and electrical devices. Among the popular dielectric materials, anti-ferroelectrics (AFE) display evidence of being a strong contender for future ceramic capacitors. AFE materials possess low dielectric loss, low coercive field, low remnant polarization, high energy density, high material efficiency, and fast discharge rates; all of these characteristics makes AFE materials a lucrative research direction. However, despite the evident advantages, there have only been limited attempts to develop this area. This article attempts to provide a focus to this area by presenting a timely review on the topic, on the relevant scientific advancements that have been made with respect to utilization and development of anti-ferroelectric materials for electric energy storage applications. The article begins with a general introduction discussing the need for high energy density capacitors, the present solutions being used to address this problem, and a brief discussion of various advantages of anti-ferroelectric materials for high energy storage applications. This is followed by a general description of anti-ferroelectricity and important anti-ferroelectric materials. The remainder of the paper is divided into two subsections, the first of which presents various physical routes for enhancing the energy storage density while the latter section describes chemical routes for enhanced storage density. This is followed by conclusions and future prospects and challenges which need to be addressed in this particular field. PMID:28793694

Structure-Function Relationships of Ferroelectric Polymers.

NASA Astrophysics Data System (ADS)

Pavlopoulou, Eleni; Maiz, Jon; Spampinato, Nicoletta; Maglione, Mario; Hadziioannou, Georges

Poly(vinylidene fluoride), PVDF, and its copolymers with trifluoroethylene, P(VDF-co-TrFE) have been long appreciated for their excellent ferroelectric properties. Although they have been mainly studied in the 80s and 90s, understanding their performance is still lacking. Yet the increasing use of P(VDF-co-TrFE) thin films in organic electronic devices during the last ten years revives the need for apprehending the function of these materials. In this work we investigate the structure of P(VDF-co-TrFE) films and correlate it to their ferroelectric properties. Our results show that ferroelectric performance is solely driven by the fraction of polymer that has been crystallized in the ferroelectric phases of PVDF. The relations between remnant polarization, coercive field and dipole switching rate of P(VDF-co-TrFE) with the ferroelectric crystallinity are demonstrated. The French Research Agency (ANR), the Aquitaine Region, Arkema and STMicroelectronics are kindly acknowledged for financial support.

Ferroelectric polymer dielectrics: Emerging materials for future electrostatic energy storage applications

NASA Astrophysics Data System (ADS)

Panda, Maheswar

2018-05-01

In this manuscript, the dielectric behavior of a variety of ferroelectric polymer dielectrics (FPD), which may bethe materials for future electrostatic energy storage application shave been discussed. The variety of polymer dielectrics, comprising of ferroelectric polymer[polyvinylidene fluoride (PVDF)]/non-polarpolymer [low density polyethylene (LDPE)] and different sizes of metal particles (Ni, quasicrystal of Al-Cu-Fe) as filler, were prepared through different process conditions (cold press/hot press) and are investigated experimentally. Very high values of effective dielectric constants (ɛeff) with low loss tangent (Tan δ) were observed forall the prepared FPD at their respective percolation thresholds (fc). The enhancement of ɛeff and Tan δ at the insulator to metal transition (IMT) is explained through the boundary layer capacitor effect and the percolation theory respectively. The non-universal fc/critical exponents across the IMT have been explained through percolation theory andis attributed to the fillerparticle size& shape, interaction between the components, method of their preparation, adhesiveness, connectivity and homogeneity, etc. of the samples. Recent results on developed FPD with high ɛeff and low Tan δ prepared through cold press have proven themselves to be the better candidates for low frequency and static dielectric applications.

Why is the electrocaloric effect so small in ferroelectrics?

DOE PAGES

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

2016-05-19

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 widemore » 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.« less

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.

Ferroelectric large polarons

NASA Astrophysics Data System (ADS)

Miyata, Kiyoshi; Zhu, X.-Y.

2018-05-01

Kiyoshi Miyata and X.-Y. Zhu analyse the ferroelectric-like dielectric response of lead halide perovskites in the terahertz region and discuss the potential role of polar nanodomains in accounting for the defect tolerance and low recombination rates of these materials.

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.

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.

Multiscale Simulations of Dynamics of Ferroelectric Domains

NASA Astrophysics Data System (ADS)

Liu, Shi

Ferroelectrics with switchable polarization have many important technological applications, which heavily rely on the interactions between the polarization and external perturbations. Understanding the dynamical response of ferroelectric materials is crucial for the discovery and development of new design principles and engineering strategies for optimized and breakthrough applications of ferroelectrics. We developed a multiscale computational approach that combines methods at different length and time scales to elucidate the connection between local structures, domain dynamics, and macroscopic finite-temperature properties of ferroelectrics. We started from first-principles calculations of ferroelectrics to build a model interatomic potential, enabling large-scale molecular dynamics (MD) simulations. The atomistic insights of nucleation and growth at the domain wall obtained from MD were then incorporated into a continuum model within the framework of Landau-Ginzburg-Devonshire theory. This progressive theoretical framework allows for the first time an efficient and accurate estimation of macroscopic properties such as the coercive field for a broad range of ferroelectrics from first-principles. This multiscale approach has also been applied to explore the effect of dipolar defects on ferroelectric switching and to understand the origin of giant electro-strain coupling. ONR, NSF, Carnegie Institution for Science.

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

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.

Ferroelectrics under the Synchrotron Light: A Review.

PubMed

Fuentes-Cobas, Luis E; Montero-Cabrera, María E; Pardo, Lorena; Fuentes-Montero, Luis

2015-12-30

Currently, an intensive search for high-performance lead-free ferroelectric materials is taking place. ABO₃ perovskites (A = Ba, Bi, Ca, K and Na; B = Fe, Nb, Ti, and Zr) appear as promising candidates. Understanding the structure-function relationship is mandatory, and, in this field, the roles of long- and short-range crystal orders and interactions are decisive. In this review, recent advances in the global and local characterization of ferroelectric materials by synchrotron light diffraction, scattering and absorption are analyzed. Single- and poly-crystal synchrotron diffraction studies allow high-resolution investigations regarding the long-range average position of ions and subtle global symmetry break-downs. Ferroelectric materials, under the action of electric fields, undergo crystal symmetry, crystallite/domain orientation distribution and strain condition transformations. Methodological aspects of monitoring these processes are discussed. Two-dimensional diffraction clarify larger scale ordering: polycrystal texture is measured from the intensities distribution along the Debye rings. Local order is investigated by diffuse scattering (DS) and X-ray absorption fine structure (XAFS) experiments. DS provides information about thermal, chemical and displacive low-dimensional disorders. XAFS investigation of ferroelectrics reveals local B-cation off-centering and oxidation state. This technique has the advantage of being element-selective. Representative reports of the mentioned studies are described.

Ferroelectrics under the Synchrotron Light: A Review

PubMed Central

Fuentes-Cobas, Luis E.; Montero-Cabrera, María E.; Pardo, Lorena; Fuentes-Montero, Luis

2015-01-01

Currently, an intensive search for high-performance lead-free ferroelectric materials is taking place. ABO3 perovskites (A = Ba, Bi, Ca, K and Na; B = Fe, Nb, Ti, and Zr) appear as promising candidates. Understanding the structure–function relationship is mandatory, and, in this field, the roles of long- and short-range crystal orders and interactions are decisive. In this review, recent advances in the global and local characterization of ferroelectric materials by synchrotron light diffraction, scattering and absorption are analyzed. Single- and poly-crystal synchrotron diffraction studies allow high-resolution investigations regarding the long-range average position of ions and subtle global symmetry break-downs. Ferroelectric materials, under the action of electric fields, undergo crystal symmetry, crystallite/domain orientation distribution and strain condition transformations. Methodological aspects of monitoring these processes are discussed. Two-dimensional diffraction clarify larger scale ordering: polycrystal texture is measured from the intensities distribution along the Debye rings. Local order is investigated by diffuse scattering (DS) and X-ray absorption fine structure (XAFS) experiments. DS provides information about thermal, chemical and displacive low-dimensional disorders. XAFS investigation of ferroelectrics reveals local B-cation off-centering and oxidation state. This technique has the advantage of being element-selective. Representative reports of the mentioned studies are described. PMID:28787814

Flexible graphene-PZT ferroelectric nonvolatile memory.

PubMed

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

2013-11-29

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.

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

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.

Stabilization of Polar Nanoregions in Pb-free Ferroelectrics

NASA Astrophysics Data System (ADS)

Pramanick, A.; Dmowski, W.; Egami, T.; Budisuharto, A. Setiadi; Weyland, F.; Novak, N.; Christianson, A. D.; Borreguero, J. M.; Abernathy, D. L.; Jørgensen, M. R. V.

2018-05-01

The formation of polar nanoregions through solid-solution additions is known to enhance significantly the functional properties of ferroelectric materials. Despite considerable progress in characterizing the microscopic behavior of polar nanoregions (PNR), understanding their real-space atomic structure and dynamics of their formation remains a considerable challenge. Here, using the method of dynamic pair distribution function, we provide direct insights into the role of solid-solution additions towards the stabilization of polar nanoregions in the Pb-free ferroelectric of Ba (Zr ,Ti )O3 . It is shown that for an optimum level of substitution of Ti by larger Zr ions, the dynamics of atomic displacements for ferroelectric polarization are slowed sufficiently below THz frequencies, which leads to increased local correlation among dipoles within PNRs. The dynamic pair distribution function technique demonstrates a unique capability to obtain insights into locally correlated atomic dynamics in disordered materials, including new Pb-free ferroelectrics, which is necessary to understand and control their functional properties.

Scanning Probe Microscopy and Electrical Transport Studies of Ferroelectric Thin Films and 2D van der Waals Materials

NASA Astrophysics Data System (ADS)

Xiao, Zhiyong

In this dissertation, I present the scanning microscopy and electrical transport studies of ferroelectric thin films and ferroic/2D van der Waals heterostructures. Based on the conducting probe atomic force microscopy and piezo-response force microscopy (PFM) studies of the static and dynamic behavior of ferroelectric domain walls (DW), we found that the ferroelectric polymer poly(vinylidene-fluoride-trifluorethylene) P(VDF-TrFE) is composed of two-dimensional (2D) ferroelectric monolayers (MLs) that are weakly coupled to each other. We also observed polarization asymmetry in epitaxial thin films of ferroelectric Pb(Zr,Ti)O3, which is attributed to the screening properties of the underlying conducting oxide. PFM studies also reveal ferroelectric relaxor-type behavior in ultrathin Sr(Zr,Ti)O3 films epitaxially deposited on Ge. We exploited scanning-probe-controlled domain patterning in a P(VDF-TrFE) top layer to induce nonvolatile modulation of the conduction characteristic of ML molybdenum disulfide (MoS2) between a transistor and a junction state. In the presence of a DW, MoS2 exhibits rectified Ids-Vds (IV) characteristics that are well described by the thermionic emission model. This approach can be applied to a wide range of van der Waals materials to design various functional homojunctions and nanostructures. We also studied the interfacial charge transfer effect between graphene and magnetoelectric Cr2O3 via electrostatic force microscopy and Kelvin probe force microscopy, which reveal p-type doping with up to 150 meV shift of the Fermi level. The graphene/Cr2O3 heterostructure is promising for developing magnetoelectric graphene transistors for spintronic applications.

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.

Investigations on the effects of electrode materials on the device characteristics of ferroelectric memory thin film transistors fabricated on flexible substrates

NASA Astrophysics Data System (ADS)

Yang, Ji-Hee; Yun, Da-Jeong; Seo, Gi-Ho; Kim, Seong-Min; Yoon, Myung-Han; Yoon, Sung-Min

2018-03-01

For flexible memory device applications, we propose memory thin-film transistors using an organic ferroelectric poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] gate insulator and an amorphous In-Ga-Zn-O (a-IGZO) active channel. The effects of electrode materials and their deposition methods on the characteristics of memory devices exploiting the ferroelectric field effect were investigated for the proposed ferroelectric memory thin-film transistors (Fe-MTFTs) at flat and bending states. It was found that the plasma-induced sputtering deposition and mechanical brittleness of the indium-tin oxide (ITO) markedly degraded the ferroelectric-field-effect-driven memory window and bending characteristics of the Fe-MTFTs. The replacement of ITO electrodes with metal aluminum (Al) electrodes prepared by plasma-free thermal evaporation greatly enhanced the memory device characteristics even under bending conditions owing to their mechanical ductility. Furthermore, poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate) (PEDOT:PSS) was introduced to achieve robust bending performance under extreme mechanical stress. The Fe-MTFTs using PEDOT:PSS source/drain electrodes were successfully fabricated and showed the potential for use as flexible memory devices. The suitable choice of electrode materials employed for the Fe-MTFTs is concluded to be one of the most important control parameters for highly functional flexible Fe-MTFTs.

Ferroelectric transistors with monolayer molybdenum disulfide and ultra-thin aluminum-doped hafnium oxide

NASA Astrophysics Data System (ADS)

Yap, Wui Chung; Jiang, Hao; Liu, Jialun; Xia, Qiangfei; Zhu, Wenjuan

2017-07-01

In this letter, we demonstrate ferroelectric memory devices with monolayer molybdenum disulfide (MoS2) as the channel material and aluminum (Al)-doped hafnium oxide (HfO2) as the ferroelectric gate dielectric. Metal-ferroelectric-metal capacitors with 16 nm thick Al-doped HfO2 are fabricated, and a remnant polarization of 3 μC/cm2 under a program/erase voltage of 5 V is observed. The capability of potential 10 years data retention was estimated using extrapolation of the experimental data. Ferroelectric transistors based on embedded ferroelectric HfO2 and MoS2 grown by chemical vapor deposition are fabricated. Clockwise hysteresis is observed at low program/erase voltages due to slow bulk traps located near the 2D/dielectric interface, while counterclockwise hysteresis is observed at high program/erase voltages due to ferroelectric polarization. In addition, the endurances of the devices are tested, and the effects associated with ferroelectric materials, such as the wake-up effect and polarization fatigue, are observed. Reliable writing/reading in MoS2/Al-doped HfO2 ferroelectric transistors over 2 × 104 cycles is achieved. This research can potentially lead to advances of two-dimensional (2D) materials in low-power logic and memory applications.

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.

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.

Room-temperature ferroelectricity in CuInP 2S 6 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 CuInP 2S 6 (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 ofmore » ~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.« less

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

Room-temperature ferroelectricity in CuInP2S6 ultrathin flakes.

PubMed

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

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.

Electrostatic micromotor based on ferroelectric ceramics

NASA Astrophysics Data System (ADS)

Baginsky, I. L.; Kostsov, E. G.

2004-11-01

A new electrostatic micromotor is described that utilizes the electromechanical energy conversion principle earlier described by the authors. The electromechanical energy conversion is based on reversible electrostatic rolling of thin metallic films (petals) on a ferroelectric surface. The motor's active media are layers of ferroelectric ceramics (about 100 µm in thickness). The characteristics of the electrostatic rolling of the petals on different ceramic surfaces are studied, as well as the dynamic characteristics of the micromotors. It is shown that the use of antiferroelectric material allows one to reach a specific energy capacitance comparable to that of the micromotors based on ferroelectric films and to achieve a specific power of 30-300 µW mm-2.

Ferroelectric properties of YMnO3 epitaxial films for ferroelectric-gate field-effect transistors

NASA Astrophysics Data System (ADS)

Ito, Daisuke; Fujimura, Norifumi; Yoshimura, Takeshi; Ito, Taichiro

2003-05-01

Ferroelectric properties of YMnO3 epitaxial films were studied. The ferroelectric properties of epitaxially grown (0001) YMnO3 films on (111)Pt/(0001)sapphire (epi-YMO/Pt) with an excellent crystallinity were compared to (0001)-oriented poly crystalline films on (111)Pt/ZrO2/SiO2/Si. The epi-YMO/Pt had saturated polarization-electric-field (P-E) hysteresis loops, with a remanent polarization (Pr) of 1.7 μC/cm2 and a coercive field (Ec) of 80 kV/cm. The fatigue property showed no degradation up to 1010 measured cycles. These results suggested that the YMnO3 epitaxial films were suitable ferroelectric material for the ferroelectric-gate field-effect transistors. Consequently, epitaxially grown (0001)YMnO3 films on epitaxial Y2O3/Si (epi-YMO/Si) were fabricated. The epi-YMO/Si capacitor had almost equivalent crystallinity compared to epi-YMO/Pt. It was recognized that the epi-YMO/Si capacitor exhibited the ferroelectric type C-V hysteresis loop with the width of the memory window of 4.8 V, which was almost identical to the value of twice coercive voltage of the P-E hysteresis loops of the epi-YMO/Pt. A retention time exceeding 104 s was obtained in the epi-YMO/Si capacitor.

Polarization fatigue of organic ferroelectric capacitors

PubMed Central

Zhao, Dong; Katsouras, Ilias; Li, Mengyuan; Asadi, Kamal; Tsurumi, Junto; Glasser, Gunnar; Takeya, Jun; Blom, Paul W. M.; de Leeuw, Dago M.

2014-01-01

The polarization of the ferroelectric polymer P(VDF-TrFE) decreases upon prolonged cycling. Understanding of this fatigue behavior is of great technological importance for the implementation of P(VDF-TrFE) in random-access memories. However, the origin of fatigue is still ambiguous. Here we investigate fatigue in thin-film capacitors by systematically varying the frequency and amplitude of the driving waveform. We show that the fatigue is due to delamination of the top electrode. The origin is accumulation of gases, expelled from the capacitor, under the impermeable top electrode. The gases are formed by electron-induced phase decomposition of P(VDF-TrFE), similar as reported for inorganic ferroelectric materials. When the gas barrier is removed and the waveform is adapted, a fatigue-free ferroelectric capacitor based on P(VDF-TrFE) is realized. The capacitor can be cycled for more than 108 times, approaching the programming cycle endurance of its inorganic ferroelectric counterparts. PMID:24861542

Enhanced performance of ferroelectric materials under hydrostatic pressure

NASA Astrophysics Data System (ADS)

Chauhan, Aditya; Patel, Satyanarayan; Wang, Shuai; Novak, Nikola; Xu, Bai-Xiang; Lv, Peng; Vaish, Rahul; Lynch, Christopher S.

2017-12-01

Mechanical confinement or restricted degrees of freedom have been explored for its potential to enhance the performance of ferroelectric devices. It presents an easy and reversible method to tune the response for specific applications. However, such studies have been mainly limited to uni- or bi-axial stress. This study investigates the effect of hydrostatic pressure on the ferroelectric behavior of bulk polycrystalline Pb0.99Nb0.02(Zr0.95Ti0.05)0.98O3. Polarization versus electric field hysteresis plots were generated as a function of hydrostatic pressure for a range of operating temperatures (298-398 K). The application of hydrostatic pressure was observed to induce anti-ferroelectric like double hysteresis loops. This in turn enhances the piezoelectric, energy storage, energy harvesting, and electrocaloric effects. The hydrostatic piezoelectric coefficient (dh) was increased from 50 pCN-1 (0 MPa) to ˜900 pC N-1 (265 MPa) and ˜3200 pCN-1 (330 MPa) at 298 K. Energy storage density was observed to improve by more than 4 times under pressure, in the whole temperature range. The relative change in entropy was also observed to shift from ˜0 to 4.8 J kg-1 K-1 under an applied pressure of 325 MPa. This behavior can be attributed to the evolution of pinched hysteresis loops that have been explained using a phenomenological model. All values represent an improvement of several hundred percent compared to unbiased performance, indicating the potential benefits of the proposed methodology.

Stabilization of Polar Nanoregions in Pb-free Ferroelectrics

DOE PAGES

Pramanick, A.; Dmowski, Wojciech; Egami, Takeshi; ...

2018-05-18

In this study, the formation of polar nanoregions through solid-solution additions is known to enhance significantly the functional properties of ferroelectric materials. Despite considerable progress in characterizing the microscopic behavior of polar nanoregions (PNR), understanding their real-space atomic structure and dynamics of their formation remains a considerable challenge. Here, using the method of dynamic pair distribution function, we provide direct insights into the role of solid-solution additions towards the stabilization of polar nanoregions in the Pb-free ferroelectric of Ba(Zr,Ti)O 3. It is shown that for an optimum level of substitution of Ti by larger Zr ions, the dynamics of atomicmore » displacements for ferroelectric polarization are slowed sufficiently below THz frequencies, which leads to increased local correlation among dipoles within PNRs. The dynamic pair distribution function technique demonstrates a unique capability to obtain insights into locally correlated atomic dynamics in disordered materials, including new Pb-free ferroelectrics, which is necessary to understand and control their functional properties.« less

Stabilization of Polar Nanoregions in Pb-free Ferroelectrics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pramanick, A.; Dmowski, Wojciech; Egami, Takeshi

In this study, the formation of polar nanoregions through solid-solution additions is known to enhance significantly the functional properties of ferroelectric materials. Despite considerable progress in characterizing the microscopic behavior of polar nanoregions (PNR), understanding their real-space atomic structure and dynamics of their formation remains a considerable challenge. Here, using the method of dynamic pair distribution function, we provide direct insights into the role of solid-solution additions towards the stabilization of polar nanoregions in the Pb-free ferroelectric of Ba(Zr,Ti)O 3. It is shown that for an optimum level of substitution of Ti by larger Zr ions, the dynamics of atomicmore » displacements for ferroelectric polarization are slowed sufficiently below THz frequencies, which leads to increased local correlation among dipoles within PNRs. The dynamic pair distribution function technique demonstrates a unique capability to obtain insights into locally correlated atomic dynamics in disordered materials, including new Pb-free ferroelectrics, which is necessary to understand and control their functional properties.« less

Ferroionic states: coupling between surface electrochemical and bulk ferroelectric functionalities on the nanoscale.

NASA Astrophysics Data System (ADS)

Kalinin, Sergei

Ferroelectricity on the nanoscale has remained a subject of much fascination in condensed matter physics for the last several decades. It is well-recognized that stability of the ferroelectric state necessitates effective polarization screening, and hence screening mechanism and screening charge dynamics become strongly coupled to ferroelectric phase stability and domain behavior. Previously, the role of the screening charge in macroscopic ferroelectrics was observed in phenomena such as potential retention above Curie temperature, back switching of ferroelectric domains, and chaos and intermittency during domain switching. In the last several years, multiple reports claiming ferroelectricity in ultrathin ferroelectrics based on formation of remanent polarization states, local hysteresis loops, and pressure induced switching were made. However, similar phenomena were reported for traditionally non-ferroelectric materials, creating significant level of uncertainty in the field. We pose that in the nanoscale systems, the ferroelectric state is fundamentally inseparable from electrochemical state of the surface, leading to emergence of coupled electrochemical-ferroelectric states. I will present the results of experimental and theoretical work exploring the basic mechanisms of emergence of these coupled states including the basic theory and phase-field formulation for domain evolution. I further discuss the thermodynamics and thickness evolution of this state, and demonstrate the experimental pathway to establish its presence based on spectroscopic version of piezoresponse force microscopy. Finally, the role of chemical screening on domain dynamics is explored using phase-field modelling. This analysis reconciles multiple prior studies, and set forward the predictive pathways for new generations of ferroelectric devices and applications. This research was sponsored by the Division of Materials Sciences and Engineering, BES, DOE, and was conducted at the Center for

Ferroelectricity in corundum derivatives

NASA Astrophysics Data System (ADS)

Ye, Meng; Vanderbilt, David

2016-04-01

The search for new ferroelectric (FE) materials holds promise for broadening our understanding of FE mechanisms and extending the range of application of FE materials. Here we investigate a class of A B O3 and A2B B'O6 materials that can be derived from the X2O3 corundum structure by mixing two or three ordered cations on the X site. Most such corundum derivatives have a polar structure, but it is unclear whether the polarization is reversible, which is a requirement for a FE material. In this paper, we propose a method to study the FE reversal path of materials in the corundum derivative family. We first categorize the corundum derivatives into four classes and show that only two of these allow for the possibility of FE reversal. We then calculate the energy profile and energy barrier of the FE reversal path using first-principles density functional methods with a structural constraint. Furthermore, we identify several empirical measures that can provide a rule of thumb for estimating the energy barriers. Finally, the conditions under which the magnetic ordering is compatible with ferroelectricity are determined. These results lead us to predict several potentially new FE materials.

Surface-screening mechanisms in ferroelectric thin films and their effect on polarization dynamics and domain structures

NASA Astrophysics Data System (ADS)

Kalinin, Sergei V.; Kim, Yunseok; Fong, Dillon D.; Morozovska, Anna N.

2018-03-01

For over 70 years, ferroelectric materials have been one of the central research topics for condensed matter physics and material science, an interest driven both by fundamental science and applications. However, ferroelectric surfaces, the key component of ferroelectric films and nanostructures, still present a significant theoretical and even conceptual challenge. Indeed, stability of ferroelectric phase per se necessitates screening of polarization charge. At surfaces, this can lead to coupling between ferroelectric and semiconducting properties of material, or with surface (electro) chemistry, going well beyond classical models applicable for ferroelectric interfaces. In this review, we summarize recent studies of surface-screening phenomena in ferroelectrics. We provide a brief overview of the historical understanding of the physics of ferroelectric surfaces, and existing theoretical models that both introduce screening mechanisms and explore the relationship between screening and relevant aspects of ferroelectric functionalities starting from phase stability itself. Given that the majority of ferroelectrics exist in multiple-domain states, we focus on local studies of screening phenomena using scanning probe microscopy techniques. We discuss recent studies of static and dynamic phenomena on ferroelectric surfaces, as well as phenomena observed under lateral transport, light, chemical, and pressure stimuli. We also note that the need for ionic screening renders polarization switching a coupled physical–electrochemical process and discuss the non-trivial phenomena such as chaotic behavior during domain switching that stem from this. ).

Investigation of ferroelectric liquid crystal orientation in the silica microcapillaries

NASA Astrophysics Data System (ADS)

Budaszewski, D.; Domański, A. W.; Woliński, T. R.

2013-05-01

In the paper we present our recent results concerning the orientation of ferroelectric liquid crystal molecules inside silica micro capillaries. We have infiltrated the silica micro capillaries with experimental ferroelectric liquid crystal material W-260K synthesized in the Military University of Technology. The infiltrated micro capillaries were observed under the polarization microscope while both a polarizer and an analyzer were crossed. The studies on the orientation of ferroelectric liquid crystal molecules may contribute to further studies on behavior of this group of liquid crystal materials inside photonic crystal fiber. The obtained results may lead to design of a new type of fast optical fiber sensors.

Bismuth-, Tin-, and Lead-Containing Metal-Organic Materials: Synthesis, Structure, Photoluminescence, Second Harmonic Generation, and Ferroelectric Properties

NASA Astrophysics Data System (ADS)

Wibowo, Arief Cahyo

Metal-Organic Materials (MOMs) contain metal moieties and organic ligands that combine to form discrete (e.g. metal-organic polyhedra, spheres or nanoballs, metal-organic polygons) or polymeric structures with one-, two-, or three-dimensional periodicities that can exhibit a variety of properties resulting from the presence of the metal moieties and/or ligand connectors in the structure. To date, MOMs with a range of functional attributes have been prepared, including record-breaking porosity, catalytic properties, molecular magnetism, chemical separations and sensing ability, luminescence and NLO properties, multiferroic, ferroelectric, and switchable molecular dielectric properties. We are interested in synthesizing non-centrosymmetric MOM single crystals possessing one of the ten polar space groups required for non-linear optical properties (such as second harmonic generation) and ferroelectric applications. This thesis is divided into two main parts: materials with optical properties, such as photoluminescence and materials for targeted applications such as second harmonic generation and ferroelectric properties. This thesis starts with an introduction describing material having centrosymmetric, non-polar space groups, single crystals structures and their photoluminescence properties. These crystals exhibit very interesting and rare structures as well as interesting photoluminescence properties. Chapters 2-5 of this thesis focus on photoluminescent properties of new MOMs, and detail the exploratory research involving the comparatively rare bismuth, lead, and tin coordination polymers. Specifically, the formation of single white-light emitting phosphors based on the combination of bismuth or lead with pyridine-2,5-dicarboxylate is discussed (Chapter 2). The observation of a new Bi2O2 layer and a new Bi4O 3 chain in bismuth terephthalate-based coordination polymers is presented in Chapter 3, while the formation of diverse structures of tin-based coordination

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

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.

Nonvolatile gate effect in a ferroelectric-semiconductor quantum well.

PubMed

Stolichnov, Igor; Colla, Enrico; Setter, Nava; Wojciechowski, Tomasz; Janik, Elzbieta; Karczewski, Grzegorz

2006-12-15

Field effect transistors with ferroelectric gates would make ideal rewritable nonvolatile memories were it not for the severe problems in integrating the ferroelectric oxide directly on the semiconductor channel. We propose a powerful way to avoid these problems using a gate material that is ferroelectric and semiconducting simultaneously. First, ferroelectricity in semiconductor (Cd,Zn)Te films is proven and studied using modified piezoforce scanning probe microscopy. Then, a rewritable field effect device is demonstrated by local poling of the (Cd,Zn)Te layer of a (Cd,Zn)Te/CdTe quantum well, provoking a reversible, nonvolatile change in the resistance of the 2D electron gas. The results point to a potential new family of nanoscale one-transistor memories.

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. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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.

Interface control of bulk ferroelectric polarization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yu, P; Luo, Weidong; Yi, D.

2012-01-01

The control of material interfaces at the atomic level has led to no- vel interfacial properties and functionalities. In particular, the study of polar discontinuities at interfaces between complex oxides lies at the frontier of modern condensed matter research. Here we em- ploy a combination of experimental measurements and theoretical calculations to demonstrate the control of a bulk property, namely ferroelectric polarization, of a heteroepitaxial bilayer by precise atomic-scale interface engineering. More specifically, the control is achieved by exploiting the interfacial valence mismatch to influence the electrostatic potential step across the interface, which manifests itself as the biased-voltage in ferroelectricmore » hysteresis loops and determines the ferroelectric state. A broad study of diverse systems comprising different ferroelectrics and conducting perovskite un- derlayers extends the generality of this phenomenon.« less

Surface-screening mechanisms in ferroelectric thin films and their effect on polarization dynamics and domain structures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kalinin, Sergei V.; Kim, Yunseok; Fong, Dillon D.

For over 70 years, ferroelectric materials have been one of the central research topics for condensed matter physics and material science, an interest driven both by fundamental science and applications. However, ferroelectric surfaces, the key component of ferroelectric films and nanostructures, still present a significant theoretical and even conceptual challenge. Indeed, stability of ferroelectric phase per se necessitates screening of polarization charge. At surfaces, this can lead to coupling between ferroelectric and semiconducting properties of material, or with surface (electro) chemistry, going well beyond classical models applicable for ferroelectric interfaces. In this review, we summarize recent studies of surface-screening phenomenamore » in ferroelectrics. We provide a brief overview of the historical understanding of the physics of ferroelectric surfaces, and existing theoretical models that both introduce screening mechanisms and explore the relationship between screening and relevant aspects of ferroelectric functionalities starting from phase stability itself. Given that the majority of ferroelectrics exist in multiple-domain states, we focus on local studies of screening phenomena using scanning probe microscopy techniques. We discuss recent studies of static and dynamic phenomena on ferroelectric surfaces, as well as phenomena observed under lateral transport, light, chemical, and pressure stimuli. We also note that the need for ionic screening renders polarization switching a coupled physical-electrochemical process and discuss the non-trivial phenomena such as chaotic behavior during domain switching that stem from this.« less

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

CuInP₂S₆ Room Temperature Layered Ferroelectric.

PubMed

Belianinov, A; He, Q; Dziaugys, A; Maksymovych, P; Eliseev, E; Borisevich, A; Morozovska, A; Banys, J; Vysochanskii, Y; Kalinin, S V

2015-06-10

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. 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".

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.

Quinuclidinium salt ferroelectric thin-film with duodecuple-rotational polarization-directions

NASA Astrophysics Data System (ADS)

You, Yu-Meng; Tang, Yuan-Yuan; Li, Peng-Fei; Zhang, Han-Yue; Zhang, Wan-Ying; Zhang, Yi; Ye, Heng-Yun; Nakamura, Takayoshi; Xiong, Ren-Gen

2017-04-01

Ferroelectric thin-films are highly desirable for their applications on energy conversion, data storage and so on. Molecular ferroelectrics had been expected to be a better candidate compared to conventional ferroelectric ceramics, due to its simple and low-cost film-processability. However, most molecular ferroelectrics are mono-polar-axial, and the polar axes of the entire thin-film must be well oriented to a specific direction to realize the macroscopic ferroelectricity. To align the polar axes, an orientation-controlled single-crystalline thin-film growth method must be employed, which is complicated, high-cost and is extremely substrate-dependent. In this work, we discover a new molecular ferroelectric of quinuclidinium periodate, which possesses six-fold rotational polar axes. The multi-axes nature allows the thin-film of quinuclidinium periodate to be simply prepared on various substrates including flexible polymer, transparent glasses and amorphous metal plates, without considering the crystallinity and crystal orientation. With those benefits and excellent ferroelectric properties, quinuclidinium periodate shows great potential in applications like wearable devices, flexible materials, bio-machines and so on.

Electrical and structural investigations, and ferroelectric domains in nanoscale structures

NASA Astrophysics Data System (ADS)

Alexe, Marin

2005-03-01

Generally speaking material properties are expected to change as the characteristic dimension of a system approaches at the nanometer scale. In the case of ferroelectric materials fundamental problems such as the super-paraelectric limit, influence of the free surface and/or of the interface and bulk defects on ferroelectric switching, etc. arise when scaling the systems into the sub-100 nm range. In order to study these size effects, fabrication methods of high quality nanoscale ferroelectric crystals as well as AFM-based investigations methods have been developed in the last few years. The present talk will briefly review self-patterning and self- assembly fabrication methods, including chemical routes, morphological instability of ultrathin films, and self-assembly lift-off, employed up to the date to fabricate ferroelectric nanoscale structures with lateral size in the range of few tens of nanometers. Moreover, in depth structural and electrical investigations of interfaces performed to differentiate between intrinsic and extrinsic size effects will be also presented.

Negative-pressure-induced enhancement in a freestanding ferroelectric

NASA Astrophysics Data System (ADS)

Wang, Jin; Wylie-van Eerd, Ben; Sluka, Tomas; Sandu, Cosmin; Cantoni, Marco; Wei, Xian-Kui; Kvasov, Alexander; McGilly, Leo John; Gemeiner, Pascale; Dkhil, Brahim; Tagantsev, Alexander; Trodahl, Joe; Setter, Nava

2015-10-01

Ferroelectrics are widespread in technology, being used in electronics and communications, medical diagnostics and industrial automation. However, extension of their operational temperature range and useful properties is desired. Recent developments have exploited ultrathin epitaxial films on lattice-mismatched substrates, imposing tensile or compressive biaxial strain, to enhance ferroelectric properties. Much larger hydrostatic compression can be achieved by diamond anvil cells, but hydrostatic tensile stress is regarded as unachievable. Theory and ab initio treatments predict enhanced properties for perovskite ferroelectrics under hydrostatic tensile stress. Here we report negative-pressure-driven enhancement of the tetragonality, Curie temperature and spontaneous polarization in freestanding PbTiO3 nanowires, driven by stress that develops during transformation of the material from a lower-density crystal structure to the perovskite phase. This study suggests a simple route to obtain negative pressure in other materials, potentially extending their exploitable properties beyond their present levels.

Mesopores induced zero thermal expansion in single-crystal ferroelectrics.

PubMed

Ren, Zhaohui; Zhao, Ruoyu; Chen, Xing; Li, Ming; Li, Xiang; Tian, He; Zhang, Ze; Han, Gaorong

2018-04-24

For many decades, zero thermal expansion materials have been the focus of numerous investigations because of their intriguing physical properties and potential applications in high-precision instruments. Different strategies, such as composites, solid solution and doping, have been developed as promising approaches to obtain zero thermal expansion materials. However, microstructure controlled zero thermal expansion behavior via interface or surface has not been realized. Here we report the observation of an impressive zero thermal expansion (volumetric thermal expansion coefficient, -1.41 × 10 -6  K -1 , 293-623 K) in single-crystal ferroelectric PbTiO 3 fibers with large-scale faceted and enclosed mesopores. The zero thermal expansion behavior is attributed to a synergetic effect of positive thermal expansion near the mesopores due to the oxygen-based polarization screening and negative thermal expansion from an intrinsic ferroelectricity. Our results show that a fascinating surface construction in negative thermal expansion ferroelectric materials could be a promising strategy to realize zero thermal expansion.

Ferroelectricity in corundum derivatives

NASA Astrophysics Data System (ADS)

Ye, Meng; Vanderbilt, David

The search for new ferroelectric (FE) materials holds promise for broadening our understanding of FE mechanisms and extending the range of application of FE materials. The known FE materials LiNbO3 can be regarded as derived from the A2O3 corundum structure with cation ordering. Here we consider more general binary (AB O3) and ternary (A2 BB' O6) corundum derivatives as an extended class of potential FE materials, motivated by the fact that some members of this class have recently been synthesized. There are four structure types for these corundum derivatives, and the number of cation combinations is enormous, but in many cases the energy barriers for polarization reversal may be too large to allow FE behavior. Here we present a first-principles study of the polar structure, coherent FE barrier, and domain-wall switching barrier for a representative set of polar corundum derivatives, allowing us to identify several potentially new FE materials. We also discuss the conditions under which ferroelectricity is compatible with magnetic ordering. Finally, we identify several empirical measures that can provide a rule of thumb for estimating the barrier energies. Our results should assist in the experimental search for new FE materials in the corundum derivative family. This work is supported by ONR Grant No. N-00014-12-1-1035.

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).

Thin film ferroelectric electro-optic memory

NASA Technical Reports Server (NTRS)

Thakoor, Sarita (Inventor); Thakoor, Anilkumar P. (Inventor)

1993-01-01

An electrically programmable, optically readable data or memory cell is configured from a thin film of ferroelectric material, such as PZT, sandwiched between a transparent top electrode and a bottom electrode. The output photoresponse, which may be a photocurrent or photo-emf, is a function of the product of the remanent polarization from a previously applied polarization voltage and the incident light intensity. The cell is useful for analog and digital data storage as well as opto-electric computing. The optical read operation is non-destructive of the remanent polarization. The cell provides a method for computing the product of stored data and incident optical data by applying an electrical signal to store data by polarizing the thin film ferroelectric material, and then applying an intensity modulated optical signal incident onto the thin film material to generate a photoresponse therein related to the product of the electrical and optical signals.

Cooperative Couplings between Octahedral Rotations and Ferroelectricity in Perovskites and Related Materials

NASA Astrophysics Data System (ADS)

Gu, Teng; Scarbrough, Timothy; Yang, Yurong; Íñiguez, Jorge; Bellaiche, L.; Xiang, H. J.

2018-05-01

The structure of AB O 3 perovskites is dominated by two types of unstable modes, namely, the oxygen octahedral rotation (AFD) and ferroelectric (FE) mode. It is generally believed that such AFD and FE modes tend to compete and suppress each other. Here we use first-principles methods to show that a dual nature of the FE-AFD coupling, which turns from competitive to cooperative as the AFD mode strengthens, occurs in numerous perovskite oxides. We provide a unified model of such a dual interaction by introducing novel high-order coupling terms and explain the atomistic origin of the resulting new form of ferroelectricity in terms of universal steric mechanisms. We also predict that such a novel form of ferroelectricity leads to atypical behaviors, such as an enhancement of all the three Cartesian components of the electric polarization under hydrostatic pressure and compressive epitaxial strain.

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.

Electronic ferroelectricity in carbon-based systems: from reality of organic conductors to promises of polymers and graphene nano-ribbons

NASA Astrophysics Data System (ADS)

Kirova, Natasha; Brazovskii, Serguei

2014-03-01

Ferroelectricity is a rising demand in fundamental and applied solid state physics. Ferroelectrics are used in microelectronics as active gate materials, in capacitors, electro-optical-acoustic modulators, etc. There is a particular demand for plastic ferroelectrics, e.g. as a sensor for acoustic imaging in medicine and beyond, in shapeable capacitors, etc. Microscopic mechanisms of ferroelectric polarization in traditional materials are typically ionic. In this talk we discuss the electronic ferroelectrics - carbon-based materials: organic crystals, conducting polymers and graphene nano-ribbons. The motion of walls, separating domains with opposite electric polarisation, can be influenced and manipulated by terahertz and infra-red range optics.

Theory and computer simulation of relaxor ferroelectrics doped by off-center impurities

NASA Astrophysics Data System (ADS)

Su, Chin-Cheng

A family of ferroelectric materials have relaxation type dynamics. These materials, called relaxor ferroelectrics, show remarkable dielectric and electromechanical properties important for many practical applications that are different from those of normal ferroelectrics. Despite of the engineering importance of relaxor ferroelectrics, the physical origin of the relaxor behavior is not fully understood. A purpose of this thesis is to advance the theory of relaxor ferroelectrics and to develop the model, which could be used for a computer simulation of the static dielectric and dynamic properties and their relation to the concentration of dopant ions. In this thesis, a Ginzburg-Landau type theory of interaction of randomly distributed local dipoles immersed in a paraelectric crystal is developed. The interaction is caused by the polarization of the host lattice generated by these dipoles. It is long-ranged and decays proportionally to the inverse distance between the local dipoles. The obtained effective Hamiltonian of the dipole-dipole interaction is employed for both the Monte Carlo and the Master Equation simulations of the dielectric and ferroelectric properties of a system with off-center dopant ions producing local dipoles. The computer simulation shows that at low concentration of dopant ions the paraelectric state transforms into a macroscopically paraelectric state consisting of randomly oriented polar clusters. The behavior of the system is similar to that of a spin-glass system. The polar clusters amplify the effective dipole moment and significantly increase the dielectric constant. It is shown that the interaction between the clusters results in a spectrum of relaxation times and the transition to the relaxor state. The real and imaginary parts of the susceptibility of this state are calculated. The slim hysteresis loop in the polarization, which usually appears in the high temperature non-polarized relaxor ferroelectrics, is also obtained for our doped

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

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

Complex Electric-Field Induced Phenomena in Ferroelectric/Antiferroelectric Nanowires

NASA Astrophysics Data System (ADS)

Herchig, Ryan Christopher

Perovskite ferroelectrics and antiferroelectrics have attracted a lot of attention owing to their potential for device applications including THz sensors, solid state cooling, ultra high density computer memory, and electromechanical actuators to name a few. The discovery of ferroelectricity at the nanoscale provides not only new and exciting possibilities for device miniaturization, but also a way to study the fundamental physics of nanoscale phenomena in these materials. Ferroelectric nanowires show a rich variety of physical characteristics which are advantageous to the design of nanoscale ferroelectric devices such as exotic dipole patterns, a strong dependence of the polarization and phonon frequencies on the electrical and mechanical boundary conditions, as well as a dependence of the transition temperatures on the diameter of the nanowire. Antiferroelectricity also exists at the nanoscale and, due to the proximity in energy of the ferroelectric and antiferroelectric phases, a phase transition from the ferroelectric to the antiferroelectric phase can be facilitated through the application of the appropriate mechanical and electrical boundary conditions. While much progress has been made over the past several decades to understand the nature of ferroelectricity/antiferroelectricity in nanowires, many questions remain unanswered. In particular, little is known about how the truncated dimensions affect the soft mode frequency dynamics or how various electrical and mechanical boundary conditions might change the nature of the phase transitions in these ferroelectric nanowires. Could nanowires offer a distinct advantage for solid state cooling applications? Few studies have been done to elucidate the fundamental physics of antiferroelectric nanowires. How the polarization in ferroelectric nanowires responds to a THz electric field remains relatively underexplored as well. In this work, the aim is to to develop and use computational tools that allow first

Constitutive relations of ferroelectric ceramics

NASA Astrophysics Data System (ADS)

Su, Yu

The objective of this thesis is to obtain a better understanding on the fundamental constitutive behavior of ferroelectric ceramics based on the physics of phase transition, micromechanics of heterogeneous materials, and principles of irreversible thermodynamics. Within this framework, a self-consistent model is developed to investigate the electromechanical responses of ferroelectric polycrystals under temperature change and electromechanical loading. Cooling of a paraelectric crystal below its curie temperature Tc would result in spontaneous polarization, whereas electromechanical loading on a poled crystal could lead to domain switch. Domain growth and reorientation inside ferroelectric crystals are studied in light of these phase transition and domain switch. In this process, the change of the effective elastic, dielectric and piezoelectric constants during the evolution of microstructures are examined. In addition, hysteresis loops for the electric displacement and other related phenomena are computed under cyclic electric load. On top of all methods implemented in this work, the kinetic equation derived from the irreversible thermodynamics is the key to study the domain evolution in ferroelectric crystals. The kinetic relation not only governs the growth of new domain in a ferroelectric crystal, but it also determines the onset of phase transition. This characteristic is used to study the effect of hydrostatic pressure on the shift of Curie temperature of a ferroelectric crystal. Based on the derived expressions, it is observed that the deriving force can increase or decrease upon applied hydrostatic mechanical loading, depending on the change of electromechanical moduli, eigenstrain and electro-polarization. Several typical cases are computed and it is found that the change of the electromechanical moduli during phase transformation plays the key role in the shift of Curie temperature. Since ferroelectric ceramics are in a polycrystal form, a self

Reversible optical control of macroscopic polarization in ferroelectrics

NASA Astrophysics Data System (ADS)

Rubio-Marcos, Fernando; Ochoa, Diego A.; Del Campo, Adolfo; García, Miguel A.; Castro, Germán R.; Fernández, José F.; García, José E.

2018-01-01

The optical control of ferroic properties is a subject of fascination for the scientific community, because it involves the establishment of new paradigms for technology1-9. Domains and domain walls are known to have a great impact on the properties of ferroic materials1-24. Progress is currently being made in understanding the behaviour of the ferroelectric domain wall, especially regarding its dynamic control10-12,17,19. New research is being conducted to find effective methodologies capable of modulating ferroelectric domain motion for future electronics. However, the practical use of ferroelectric domain wall motion should be both stable and reversible (rewritable) and, in particular, be able to produce a macroscopic response that can be monitored easily12,17. Here, we show that it is possible to achieve a reversible optical change of ferroelectric domains configuration. This effect leads to the tuning of macroscopic polarization and its related properties by means of polarized light, a non-contact external control. Although this is only the first step, it nevertheless constitutes the most crucial one in the long and complex process of developing the next generation of photo-stimulated ferroelectric devices.

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

Heterogeneous Polarized States in Ferroelectric Inclusions in a Ferroelectric-Dielectric Nanocomposite

NASA Astrophysics Data System (ADS)

Nechaev, V. N.; Viskovatykh, A. V.

2018-06-01

The behavior of the previously observed inhomogeneous polarized states in ferroelectric inclusions of the nanocomposite is analyzed in detail. The domain structure of ferroelectric particles depends on the temperature and nature of interaction with the dielectric matrix. The possibility of controlling the domain structure in ferroelectric particles using an external electric field is shown.

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.

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.

Ferroelectric properties of substituted barium titanate ceramics

NASA Astrophysics Data System (ADS)

Kumar, Parveen; Singh, Sangeeta; Juneja, J. K.; Prakash, Chandra; Raina, K. K.

2009-06-01

Barium titanate (BT) is among the most studied ferroelectric material which has been used in various forms, e.g. bulk, thin and thick film, powder, in a number of applications. In order to achieve a material with desired properties, it is modified with a variety of substituents. Most common substituents have been strontium, calcium and zirconium. Here we report studies on lead and zirconium substituted BT. The material series with compositional formula Ba 0.80Pb 0.20Ti 1-xZr xO 3 with, 0< x<0.1 was chosen for investigations. The material was synthesized by solid state reaction method. Reacted powder compacted in form of circular discs were sintered in the range of 1300 °C. All the samples were subjected to X-ray analysis and found to be single phase. Ferroelectric properties were studied as a function of composition and temperature. Pr/ Ps ratio was determined. It was found to decrease with increase in x.

Ferroelectricity with Ferromagnetic Moment in Orthoferrites

NASA Astrophysics Data System (ADS)

Tokunaga, Yusuke

2010-03-01

Exotic multiferroics with gigantic magnetoelectric (ME) coupling have recently been attracting broad interests from the viewpoints of both fundamental physics and possible technological application to next-generation spintronic devices. To attain a strong ME coupling, it would be preferable that the ferroelectric order is induced by the magnetic order. Nevertheless, the magnetically induced ferroelectric state with the spontaneous ferromagnetic moment is still quite rare apart from a few conical-spin multiferroics. To further explore multiferroic materials with both the strong ME coupling and spontaneous magnetization, we focused on materials with magnetic structures other than conical structure. In this talk we present that the most orthodox perovskite ferrite systems DyFeO3 and GdFeO3 have ``ferromagnetic-ferroelectric,'' i.e., genuinely multiferroic states in which weak ferromagnetic moment is induced by Dzyaloshinskii-Moriya interaction working on Fe spins and electric polarization originates from the striction due to symmetric exchange interaction between Fe and Dy (Gd) spins [1] [2]. Both materials showed large electric polarization (>0.1 μC/cm^2) and strong ME coupling. In addition, we succeeded in mutual control of magnetization and polarization with electric- and magnetic-fields in GdFeO3, and attributed the controllability to novel, composite domain wall structure. [4pt] [1] Y. Tokunaga et al., Phys. Rev. Lett. 101, 097205 (2008). [0pt] [2] Y. Tokunaga et al., Nature Mater. 8, 558 (2009).

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

Optimization of Ferroelectric Ceramics by Design at the Microstructure Level

NASA Astrophysics Data System (ADS)

Jayachandran, K. P.; Guedes, J. M.; Rodrigues, H. C.

2010-05-01

Ferroelectric materials show remarkable physical behaviors that make them essential for many devices and have been extensively studied for their applications of nonvolatile random access memory (NvRAM) and high-speed random access memories. Although ferroelectric ceramics (polycrystals) present ease in manufacture and in compositional modifications and represent the widest application area of materials, computational and theoretical studies are sparse owing to many reasons including the large number of constituent atoms. Macroscopic properties of ferroelectric polycrystals are dominated by the inhomogeneities at the crystallographic domain/grain level. Orientation of grains/domains is critical to the electromechanical response of the single crystalline and polycrystalline materials. Polycrystalline materials have the potential of exhibiting better performance at a macroscopic scale by design of the domain/grain configuration at the domain-size scale. This suggests that piezoelectric properties can be optimized by a proper choice of the parameters which control the distribution of grain orientations. Nevertheless, this choice is complicated and it is impossible to analyze all possible combinations of the distribution parameters or the angles themselves. Hence we have implemented the stochastic optimization technique of simulated annealing combined with the homogenization for the optimization problem. The mathematical homogenization theory of a piezoelectric medium is implemented in the finite element method (FEM) by solving the coupled equilibrium electrical and mechanical fields. This implementation enables the study of the dependence of the macroscopic electromechanical properties of a typical crystalline and polycrystalline ferroelectric ceramic on the grain orientation.

Magnetic enhancement of ferroelectric polarization in a self-grown ferroelectric-ferromagnetic composite

NASA Astrophysics Data System (ADS)

Kumar, Amit; Narayan, Bastola; Pachat, Rohit; Ranjan, Rajeev

2018-02-01

Ferroelectric-ferromagnetic multiferroic composites are of great interest both from the scientific and technological standpoints. The extent of coupling between polarization and magnetization in such two-phase systems depends on how efficiently the magnetostrictive and electrostrictive/piezoelectric strain gets transferred from one phase to the other. This challenge is most profound in the easy to make 0-3 ferroelectric-ferromagnetic particulate composites. Here we report a self-grown ferroelectric-ferromagnetic 0-3 particulate composite through controlled spontaneous precipitation of ferrimagnetic barium hexaferrite phase (BaF e12O19 ) amid ferroelectric grains in the multiferroic alloy system BiFe O3-BaTi O3 . We demonstrate that a composite specimen exhibiting merely ˜1% hexaferrite phase exhibits ˜34% increase in saturation polarization in a dc magnetic field of ˜10 kOe. Using modified Rayleigh analysis of the polarization field loop in the subcoercive field region we argue that the substantial enhancement in the ferroelectric switching is associated with the reduction in the barrier heights of the pinning centers of the ferroelectric-ferroelastic domain walls in the stress field generated by magnetostriction in the hexaferrite grains when the magnetic field is turned on. Our study proves that controlled precipitation of the magnetic phase is a good strategy for synthesis of 0-3 ferroelectric-ferromagnetic particulate multiferroic composite as it not only helps in ensuring a good electrical insulating character of the composite, enabling it to sustain high enough electric field for ferroelectric switching, but also the factors associated with the spontaneity of the precipitation process ensure efficient transfer of the magnetostrictive strain/stress to the surrounding ferroelectric matrix making domain wall motion easy.

Ferroelectric Based High Power Components for L-Band Accelerator Applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kanareykin, Alex; Jing, Chunguang; Kostin, Roman

2018-01-16

We are developing a new electronic device to control the power in particle accelerators. The key technology is a new nanostructured material developed by Euclid that changes its properties with an applied electric field. Both superconducting and conventional accelerating structures require fast electronic control of the input rf power. A fast controllable phase shifter would allow for example the control of the rf power delivered to multiple accelerating cavities from a single power amplifier. Nonlinear ferroelectric microwave components can control the tuning or the input power coupling for rf cavities. Applying a bias voltage across a nonlinear ferroelectric changes itsmore » permittivity. This effect can be used to cause a phase change of a propagating rf signal or change the resonant frequency of a cavity. The key is the development of a low loss highly tunable ferroelectric material.« less

Shock induced phase transitions and current generation in ferroelectric ceramics

NASA Astrophysics Data System (ADS)

Agrawal, Vinamra; Bhattacharya, Kaushik

2017-06-01

Ferroelectric materials are used as ferroelectric generators to obtain pulsed power by subjecting them to a shock loading. The impact induces a phase transition and at high impact speeds, dielectric breakdown. Depending on the loading conditions and the electromechanical boundary conditions, the current or voltage profiles obtained vary. We explore the phenomenon of large deformation dynamic behavior and the associated electro-thermo-mechanical coupling of ferroelectric materials in adiabatic environments. Using conservation laws, Maxwell's equations and second law of thermodynamics, we obtain a set of governing equations for the material and the driving force acting on the propagating phase boundary. We also account for the possibility of surface charges on the phase boundary in case of dielectric breakdown which introduces contribution of curvature of the phase boundary in the equations. Next, the governing equations are used to solve a plate impact problem. The Helmholtz energy of the material is chosen be a combination of piecewise quadratic potential in polarization and thermo-elastic material capable of undergoing phase transformation. We obtain current profiles for short circuit boundary conditions along with strain, particle velocity and temperature maps. US AFOSR through Center of Excellence in High Rate Deformation of Heterogeneous Materials FA 9550-12-1-0091.

Room-temperature ferromagnetism in Fe-based perovskite solid solution in lead-free ferroelectric Bi0.5Na0.5TiO3 materials

NASA Astrophysics Data System (ADS)

Hung, Nguyen The; Bac, Luong Huu; Trung, Nguyen Ngoc; Hoang, Nguyen The; Van Vinh, Pham; Dung, Dang Duc

2018-04-01

The integration of ferromagnetism in lead-free ferroelectric materials is important to fabricate smart materials for electronic devices. In this work, (1 - x)Bi0.5Na0.5TiO3 + xMgFeO3-δ materials (x = 0-9 mol%) were prepared through sol-gel method. X-ray diffraction characterization indicated that MgFeO3-δ materials existed as a well solid solution in lead-free ferroelectric Bi0.5Na0.5TiO3 materials. The rhombohedral structure of Bi0.5Na0.5TiO3 materials was distorted due to the random distribution of Mg and Fe cations into the host lattice. The reduced optical band gap and the induced room-temperature ferromagnetism were due to the spin splitting of transition metal substitution at the B-site of perovskite Bi0.5Na0.5TiO3 and the modification by A-site co-substitution. This work elucidates the role of secondary phase as solid solution in Bi0.5Na0.5TiO3 material for development of lead-free multiferroelectric materials.

Correlation among oxygen vacancies in bismuth titanate ferroelectric ceramics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li Wei; Chen Kai; Yao Yangyang

2004-11-15

Pure Bi{sub 4}Ti{sub 3}O{sub 12} ceramics were prepared using the conventional solid-state reaction method and their dielectric properties were investigated. A dielectric loss peak with the relaxation-type characteristic was observed at about 370 K at 100 Hz frequency. This peak was confirmed to be associated with the migration of oxygen vacancies inside ceramics. The Cole-Cole fitting to this peak reveals a strong correlation among oxygen vacancies and this strong correlation is considered to commonly exist among oxygen vacancies in ferroelectrics. Therefore, the migration of oxygen vacancies in ferroelectric materials would demonstrate a collective behavior instead of an individual one duemore » to this strong correlation. Furthermore, this correlation is in proportion to the concentration and in inverse proportion to the activation energy of oxygen vacancies. These results could be helpful to the understanding of the fatigue mechanisms in ferroelectric materials.« less

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

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.

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.

Ferroelectric polarization in nanocrystalline hydroxyapatite thin films on silicon.

PubMed

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.

Ferroelectricity and piezoelectricity in soft biological tissue: Porcine aortic walls revisited

NASA Astrophysics Data System (ADS)

Lenz, Thomas; Hummel, Regina; Katsouras, Ilias; Groen, Wilhelm A.; Nijemeisland, Marlies; Ruemmler, Robert; Schäfer, Michael K. E.; de Leeuw, Dago M.

2017-09-01

Recently reported piezoresponse force microscopy (PFM) measurements have proposed that porcine aortic walls are ferroelectric. This finding may have great implications for understanding biophysical properties of cardiovascular diseases such as arteriosclerosis. However, the complex anatomical structure of the aortic wall with different extracellular matrices appears unlikely to be ferroelectric. The reason is that a prerequisite for ferroelectricity, which is the spontaneous switching of the polarization, is a polar crystal structure of the material. Although the PFM measurements were performed locally, the phase-voltage hysteresis loops could be reproduced at different positions on the tissue, suggesting that the whole aorta is ferroelectric. To corroborate this hypothesis, we analyzed entire pieces of porcine aorta globally, both with electrical and electromechanical measurements. We show that there is no hysteresis in the electric displacement as well as in the longitudinal strain as a function of applied electric field and that the strain depends on the electric field squared. By using the experimentally determined quasi-static permittivity and Young's modulus of the fixated aorta, we show that the strain can quantitatively be explained by Maxwell stress and electrostriction, meaning that the aortic wall is neither piezoelectric nor ferroelectric, but behaves as a regular dielectric material.

Improper ferroelectric polarization in a perovskite driven by intersite charge transfer and ordering

NASA Astrophysics Data System (ADS)

Chen, Wei-Tin; Wang, Chin-Wei; Wu, Hung-Cheng; Chou, Fang-Cheng; Yang, Hung-Duen; Simonov, Arkadiy; Senn, M. S.

2018-04-01

It is of great interest to design and make materials in which ferroelectric polarization is coupled to other order parameters such as lattice, magnetic, and electronic instabilities. Such materials will be invaluable in next-generation data storage devices. Recently, remarkable progress has been made in understanding improper ferroelectric coupling mechanisms that arise from lattice and magnetic instabilities. However, although theoretically predicted, a compact lattice coupling between electronic and ferroelectric (polar) instabilities has yet to be realized. Here we report detailed crystallographic studies of a perovskite HgAMn3A'Mn4BO12 that is found to exhibit a polar ground state on account of such couplings that arise from charge and orbital ordering on both the A'- and B-sites, which are themselves driven by a highly unusual MnA '-MnB intersite charge transfer. The inherent coupling of polar, charge, orbital, and hence magnetic degrees of freedom make this a system of great fundamental interest, and demonstrating ferroelectric switching in this and a host of recently reported hybrid improper ferroelectrics remains a substantial challenge.

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.

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.

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

Polar Vortices Observed in Ferroelectric | Berkeley Lab

Science.gov Websites

vortices" that appear to be the electrical cousins of magnetic skyrmions holds intriguing structures are confined to magnetic systems and aren't possible in ferroelectric materials, but through the . Ferroic materials display unique electrical or magnetic properties - or both in the case of multiferroics

CuInP 2S 6 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, CuInP 2S 6 (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 cleavedmore » 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”.« less

New Ferroelectric Phase in Atomic-Thick Phosphorene Nanoribbons: Existence of in-Plane Electric Polarization.

PubMed

Hu, Ting; Wu, Haiping; Zeng, Haibo; Deng, Kaiming; Kan, Erjun

2016-12-14

Ferroelectrics have many significant applications in electric devices, such as capacitor or random-access memory, tuning the efficiency of solar cell. Although atomic-thick ferroelectrics are the necessary components for high-density electric devices or nanoscale devices, the development of such materials still faces a big challenge because of the limitation of intrinsic mechanism. Here, we reported that in-plane atomic-thick ferroelectricity can be induced by vertical electric field in phosphorene nanoribbons (PNRs). Through symmetry arguments, we predicted that ferroelectric direction is perpendicular to the direction of external electric field and lies in the plane. Further confirmed by the comprehensive first-principles calculations, we showed that such ferroelectricity is induced by the electron-polarization, which is different from the structural distortion in traditional ferroelectrics and the recent experimental discovery of in-plane atomic-thick ferroelectrics (Science 2016, 353, 274). Moreover, we found that the value of electronic polarization in bilayer is much larger than that in monolayer. Our results show that electron-polarization ferroelectricity maybe the most promising candidate for atomic-thick ferroelectrics.

Kinetics of Domain Switching by Mechanical and Electrical Stimulation in Relaxor-Based Ferroelectrics

NASA Astrophysics Data System (ADS)

Chen, Zibin; Hong, Liang; Wang, Feifei; An, Xianghai; Wang, Xiaolin; Ringer, Simon; Chen, Long-Qing; Luo, Haosu; Liao, Xiaozhou

2017-12-01

Ferroelectric materials have been extensively explored for applications in high-density nonvolatile memory devices because of their ferroelectric-ferroelastic domain-switching behavior under electric loading or mechanical stress. However, the existence of ferroelectric and ferroelastic backswitching would cause significant data loss, which affects the reliability of data storage. Here, we apply in situ transmission electron microscopy and phase-field modeling to explore the unique ferroelastic domain-switching kinetics and the origin of this in relaxor-based Pb (Mg1 /3Nb2 /3)O3-33 % PbTiO3 single-crystal pillars under electrical and mechanical stimulations. Results showed that the electric-mechanical hysteresis loop shifted for relaxor-based single-crystal pillars because of the low energy levels of domains in the material and the constraint on the pillars, resulting in various mechanically reversible and irreversible domain-switching states. The phenomenon can potentially be used for advanced bit writing and reading in nonvolatile memories, which effectively overcomes the backswitching problem and broadens the types of ferroelectric materials for nonvolatile memory applications.

A new method to study ferroelectrics using the remanent Henkel plots

NASA Astrophysics Data System (ADS)

Vopson, Melvin M.

2018-05-01

Analysis of experimental curves constructed from dc demagnetization and isothermal remanent magnetization known as Henkel and delta M plots, have served for over 53 years as an important tool for characterization of interactions in ferromagnets. In this article we address the question whether the same experimental technique could be applied to the study of ferroelectric systems. The successful measurement of the equivalent dc depolarisation and isothermal remanent polarization curves and the construction of the Henkel and delta P plots for ferroelectrics is reported here. Full measurement protocol is provided together with experimental examples for two ferroelectric ceramic samples. This new measurement technique is an invaluable experimental tool that could be used to further advance our understanding of ferroelectric materials and their applications.

Comparative analysis of ferroelectric domain statistics via nonlinear diffraction in random nonlinear materials.

PubMed

Wang, B; Switowski, K; Cojocaru, C; Roppo, V; Sheng, Y; Scalora, M; Kisielewski, J; Pawlak, D; Vilaseca, R; Akhouayri, H; Krolikowski, W; Trull, J

2018-01-22

We present an indirect, non-destructive optical method for domain statistic characterization in disordered nonlinear crystals having homogeneous refractive index and spatially random distribution of ferroelectric domains. This method relies on the analysis of the wave-dependent spatial distribution of the second harmonic, in the plane perpendicular to the optical axis in combination with numerical simulations. We apply this technique to the characterization of two different media, Calcium Barium Niobate and Strontium Barium Niobate, with drastically different statistical distributions of ferroelectric domains.

Electrostatic engineering of strained ferroelectric perovskites from first principles

NASA Astrophysics Data System (ADS)

Cazorla, Claudio; Stengel, Massimiliano

2015-12-01

Design of novel artificial materials based on ferroelectric perovskites relies on the basic principles of electrostatic coupling and in-plane lattice matching. These rules state that the out-of-plane component of the electric displacement field and the in-plane components of the strain are preserved across a layered superlattice, provided that certain growth conditions are respected. Intense research is currently directed at optimizing materials functionalities based on these guidelines, often with remarkable success. Such principles, however, are of limited practical use unless one disposes of reliable data on how a given material behaves under arbitrary electrical and mechanical boundary conditions. Here we demonstrate, by focusing on the prototypical ferroelectrics PbTiO3 and BiFeO3 as test cases, how such information can be calculated from first principles in a systematic and efficient way. In particular, we construct a series of two-dimensional maps that describe the behavior of either compound (e.g., concerning the ferroelectric polarization and antiferrodistortive instabilities) at any conceivable choice of the in-plane lattice parameter, a , and out-of-plane electric displacement, D . In addition to being of immediate practical applicability to superlattice design, our results bring new insight into the complex interplay of competing degrees of freedom in perovskite materials and reveal some notable instances where the behavior of these materials depart from what naively is expected.

Ferroelectric-field-effect-enhanced electroresistance in metal/ferroelectric/semiconductor tunnel junctions

NASA Astrophysics Data System (ADS)

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 104, 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.

Domain walls and ferroelectric reversal in corundum derivatives

NASA Astrophysics Data System (ADS)

Ye, Meng; Vanderbilt, David

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 to further search for ferroelectric candidates in materials of the corundum derivative family. The work is supported by ONR Grant N00014-12-1-1035.

Local control of the resistivity of graphene through mechanically induced switching of a ferroelectric superlattice

NASA Astrophysics Data System (ADS)

Humed Yusuf, Mohammed; Gura, Anna; Du, Xu; Dawber, Matthew

2017-06-01

We exploit nanoscale mechanically induced switching of an artificially layered ferroelectric material, used as an active substrate, to achieve the local manipulation of the electrical transport properties of graphene. In Graphene Ferroelectric Field Effect Transistors (GFeFETs), the graphene channel’s charge state is controlled by an underlying ferroelectric layer. The tip of an atomic force microscope (AFM) can be used to mechanically ‘write’ nanoscale regions of the graphene channel and ‘read’ off the modulation in the transport behavior. The written features associated with the switching of ferroelectric domains remain polarized until an electrical reset operation is carried out. Our result provides a method for flexible and reversible nano-scale manipulation of the transport properties of a broad class of 2D materials.

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

Ultrafast terahertz-field-driven ionic response in ferroelectric BaTiO 3

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, F.; Zhu, Y.; Liu, S.

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 BaTiO 3 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. Thismore » 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.« less

Ultrafast terahertz-field-driven ionic response in ferroelectric BaTiO 3

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, F.; Zhu, Y.; Liu, S.

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 in this paper we apply subpicosecond duration, single-cycle terahertz pulses as an ultrafast electric field bias to prototypical BaTiO 3 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 acrossmore » 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.« less

Ultrafast terahertz-field-driven ionic response in ferroelectric BaTiO 3

DOE PAGES

Chen, F.; Zhu, Y.; Liu, S.; ...

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 in this paper we apply subpicosecond duration, single-cycle terahertz pulses as an ultrafast electric field bias to prototypical BaTiO 3 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 acrossmore » 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.« less

Spontaneous ferroelectricity in strained low-temperature monoclinic Fe3O4: A first-principles study

NASA Astrophysics Data System (ADS)

Liu, Xiang; Mi, Wen-Bo

2018-04-01

As a single-phase multiferroic material, Fe3O4 exhibits spontaneous ferroelectric polarization below 38 K. However, the nature of the ferroelectricity in Fe3O4 and effect of external disturbances such as strain on it remains ambiguous. Here, the spontaneous ferroelectric polarization of low-temperature monoclinic Fe3O4 was investigated by first-principles calculations. The pseudo-centrosymmetric Fe B42-Fe B43 pair has a different valence state. The noncentrosymmetric charge distribution results in ferroelectric polarization. The initial ferroelectric polarization direction is in the - x and - z directions. The ferroelectricity along the y axis is limited owing to the symmetry of the Cc space group. Both the ionic displacement and charge separation at the Fe B42-Fe B43 pair are affected by strain, which further influences the spontaneous ferroelectric polarization of monoclinic Fe3O4. The ferroelectric polarization along the z axis exhibits an increase of 45.3% as the strain changes from 6% to -6%.

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

Why is the electrocaloric effect so small in ferroelectrics?

NASA Astrophysics Data System (ADS)

Guzman-Verri, Gian G.; Littlewood, Peter B.

2015-03-01

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 present meaningful figures of merit derived from well-known microscopic models of ferroelectricity which provide insight into the relation between the strength of the effect and the characteristic interactions of ferroelectrics such as dipole 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. Work at Argonne is supported by the U.S. Department of Energy, Office of Basic Energy Sciences under Contract No. DE-AC02-06CH11357.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

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

Probing the effects of defects on ferroelectricity in ferroelectric thin films

NASA Astrophysics Data System (ADS)

Zhu, Lin

Ferroelectric materials have been intensively studied due to their interesting properties such as piezoelectricity, ferroelectricity including spontaneous polarization, remnant polarization, hysteresis loop, and etc. In this study, effects of defects, thickness, and temperature on ferroelectric stability, hysteresis loop, and phase transition in ferroelectric thin films have been investigated using molecular dynamics simulations with first-principles effective Hamiltonian. Various types of defects are considered including oxygen vacancy, hydrogen contamination, and dead layer. We first study the effects of oxygen vacancy on ferroelectricity in PbTiO3 (PTO) thin films. An oxygen vacancy has been modeled as a +2q charged point defect which generates local strain and electrostatic fields. Atomic displacements induced by an oxygen vacancy were obtained by first-principles calculations and the corresponding strain field was fitted with elastic continuum model of a point defect. The obtained local strain and electrostatic fields are the inputs to the molecular dynamics (MD) simulations. We limited the oxygen vacancies in the interfacial layers between the film and electrodes. Oxygen vacancies reduce the spontaneous polarization and significantly increase the critical thickness below which the spontaneous polarization disappears. With the presence of oxygen vacancy only at one interface layer, PTO film exhibits asymmetric hysteresis loop which is consistent with experimental observations about the imprint effect. In the heating-up and cooling-down processes, oxygen vacancies weaken the phase transitions, but contribute tension along the thickness direction at high temperature. First-principles calculations are performed to determine the possible position, formation energy, and mobility of the interstitial hydrogen atom, and the calculated results are used as inputs to MD simulations in a large system. The hydrogen atom is able to move within one unit cell with small

Two-dimensional ferroelectric topological insulators in functionalized atomically thin bismuth layers

NASA Astrophysics Data System (ADS)

Kou, Liangzhi; Fu, Huixia; Ma, Yandong; Yan, Binghai; Liao, Ting; Du, Aijun; Chen, Changfeng

2018-02-01

We introduce a class of two-dimensional (2D) materials that possess coexisting ferroelectric and topologically insulating orders. Such ferroelectric topological insulators (FETIs) occur in noncentrosymmetric atomic layer structures with strong spin-orbit coupling (SOC). We showcase a prototype 2D FETI in an atomically thin bismuth layer functionalized by C H2OH , which exhibits a large ferroelectric polarization that is switchable by a ligand molecule rotation mechanism and a strong SOC that drives a band inversion leading to the topologically insulating state. An external electric field that switches the ferroelectric polarization also tunes the spin texture in the underlying atomic lattice. Moreover, the functionalized bismuth layer exhibits an additional quantum order driven by the valley splitting at the K and K' points in the Brillouin zone stemming from the symmetry breaking and strong SOC in the system, resulting in a remarkable state of matter with the simultaneous presence of the quantum spin Hall and quantum valley Hall effect. These phenomena are predicted to exist in other similarly constructed 2D FETIs, thereby offering a unique quantum material platform for discovering novel physics and exploring innovative applications.

Electronic ferroelectricity induced by charge and orbital orderings.

PubMed

Yamauchi, Kunihiko; Barone, Paolo

2014-03-12

After the revival of the magnetoelectric effect which took place in the early 2000s, the interest in multiferroic materials displaying simultaneous presence of spontaneous long-range magnetic and dipolar order has motivated an exponential growth of research activity, from both the experimental and theoretical perspectives. Within this context, and relying also on the rigorous formulation of macroscopic polarization as provided by the Berry-phase approach, it has been possible to identify new microscopic mechanisms responsible for the appearance of ferroelectricity. In particular, it has been realized that electronic spin, charge and orbital degrees of freedom may be responsible for the breaking of the space-inversion symmetry, a necessary condition for the appearance of electric polarization, even in centrosymmetric crystal structures. In view of its immediate potential application in magnetoelectric-based devices, many efforts have been made to understand how magnetic orderings may lead to ferroelectric polarization, and to identify candidate materials. On the other hand, the role of charge and orbital degrees of freedom, which have received much less attention, has been predicted to be non-negligible in several cases. Here, we review recent theoretical advances in the field of so-called electronic ferroelectricity, focusing on the possible mechanisms by which charge- and/or orbital-ordering effects may cause the appearance of macroscopic polarization. Generally, a naive distinction can be drawn between materials displaying almost localized electrons and those characterized by a strong covalent character and delocalized electrons. As for the latter, an intuitive understanding of basic mechanisms is provided in the framework of tight-binding model Hamiltonians, which are used to shed light on unusual charge/orbital effects in half-doped manganites, whereas the case of magnetite will be thoroughly discussed in light of recent progress pointing to an electronic

Ferroelectricity and tunneling electroresistance effect in asymmetric ferroelectric tunnel junctions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tao, L. L.; Wang, J., E-mail: jianwang@hku.hk

2016-06-14

We report the investigation on the ferroelectricity and tunneling electroresistance (TER) effect in PbTiO{sub 3} (PTO)-based ferroelectric tunnel junctions (FTJs) using first-principles calculations. For symmetric FTJs, we have calculated the average polarizations of PTO film and effective screening lengths of different metal electrodes for a number of FTJs, which is useful for experimental research. For asymmetric FTJs, significant asymmetric ferroelectric displacements in PTO film are observed, which is attributed to the intrinsic field generated by the two dissimilar electrodes. Moreover, by performing quantum transport calculations on those asymmetric FTJs, a sizable TER effect is observed. It is found that themore » asymmetry of ferroelectric displacements in PTO barrier, which is determined by the difference of work functions of the electrodes, controls the observed TER effect. Our results will help unravel the TER mechanism of asymmetric FTJs in most experiments and will be useful for the designing of FTJ-based devices.« less

Salts of diisopropylammonium - A non-toxic alternate to perovskite ferroelectrics

NASA Astrophysics Data System (ADS)

Kabir, Ekramul; Khatun, M.; Ghosh, T.; Raihan, Mustafa J.; Rahman, M.

2018-04-01

Organic ferroelectric crystals - diisopropylammonium bromide (DIPAB) and diisopropylammonium iodide (DIPAI) have been synthesized using different chemical methods. However the polarization values of these crystals are found comparable to that of inorganic ferroelectric materials. Monoclinic polar structure have been found for the crystals but the polarization and other electrical properties of DIPAB are much stable than those of DIPAI crystals. Hydroscopic nature of DIPAI crystals seems to be responsible for unstable electrical properties.

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.

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.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Prokhorenko, S.; Kohlstedt, H.; Pertsev, N. A., E-mail: pertsev.domain@mail.ioffe.ru

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 boundarymore » 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.« less

FAST TRACK COMMUNICATION: Ferroelectricity in low-symmetry biaxial nematic liquid crystals

NASA Astrophysics Data System (ADS)

Osipov, Mikhail A.; Gorkunov, Maxim V.

2010-09-01

Order parameters and phenomenological theory for both high- and low-symmetry biaxial nematic phases are presented and it is predicted that the chiral low-symmetry biaxial phase must be ferroelectric. This conclusion is based on general symmetry arguments and on the results of the Landau-de Gennes theory. The microscopic mechanism of the ferroelectric ordering in this chiral biaxial phase is illustrated using a simple molecular model based on dispersion interactions between biaxial molecules of low symmetry. Similar to the chiral smectic C* phase, the ferroelectricity in the chiral biaxial nematic phase is improper, i.e., polarization is not a primary order parameter and is not determined by dipolar interactions. Ferroelectric ordering in biaxial nematics may be found, in principle, in materials composed of chiral analogues of the tetrapod molecules which are known to exhibit biaxial phases.

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.

Giant Electrocaloric Effect in Ferroelectrics with Tailored Polaw-Nanostructures

DOE Office of Scientific and Technical Information (OSTI.GOV)

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 controlledmore » 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 = G 0+ ½ a P 2 +1/4 b P 4 + 1/6 c P 6 – EP, and a = ß (T-T c), 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 low polar-correlation and hence a very

Laterally azo-bridged h-shaped ferroelectric dimesogens for second-order nonlinear optics: ferroelectricity and second harmonic generation.

PubMed

Zhang, Yongqiang; Martinez-Perdiguero, Josu; Baumeister, Ute; Walker, Christopher; Etxebarria, Jesus; Prehm, Marko; Ortega, Josu; Tschierske, Carsten; O'Callaghan, Michael J; Harant, Adam; Handschy, Mark

2009-12-30

Two classes of laterally azo-bridged H-shaped ferroelectric liquid crystals (FLCs), incorporating azobenzene and disperse red 1 (DR-1) chromophores along the FLC polar axes, were synthesized and characterized by polarized light microscopy, differential scanning calorimetry, 2D X-ray diffraction analysis, and electro-optical investigations. They represent the first H-shaped FLC materials exhibiting the ground-state, thermodynamically stable enantiotropic SmC* phase, i.e., ground-state ferroelectricity. Second harmonic generation measurements of one compound incorporating a DR-1 chromophore at the incident wavelength of 1064 nm give a nonlinear coefficient of d(22) = 17 pm/V, the largest nonlinear optics coefficient reported to date for calamitic FLCs. This value enables viable applications of FLCs in nonlinear optics.

Coexisting exchange bias effect and ferroelectricity in geometrically frustrated ZnCr2O4

NASA Astrophysics Data System (ADS)

Dey, J. K.; Majumdar, S.; Giri, S.

2018-06-01

Concomitant occurrence of exchange bias effect and ferroelectric order is revealed in antiferromagnetic spinel ZnCr2O4. The exchange bias effect is observed below antiferromagnetic Neél temperature (T N) with a reasonable value of exchange bias field ( Oe at 2 K). Intriguingly, the ratio is found unusually high as  ∼2.2, where H C is the coercivity. This indicates that large H C is not always primary for obtaining large exchange bias effect. Ferroelectric order is observed at T N, where non-centrosymmetric magnetic structure with space group associated with the magnetoelectric coupling correlates the ferroelectric order, proposing that, ZnCr2O4 is an improper multiferroic material. Rare occurrence of exchange bias effect and ferroelectric order in ZnCr2O4 attracts the community for fundamental interest and draws special attention in designing new materials for possible electric field control of exchange bias effect.

Recent Progress in Understanding the Shock Response of Ferroelectric Ceramics

NASA Astrophysics Data System (ADS)

Setchell, R. E.

2002-07-01

Ferroelectric ceramics exhibit a permanent remanent polarization, and shock depoling of these materials to achieve pulsed sources of electrical power was proposed in the late 1950s. During the following twenty years, extensive studies were conducted to examine the shock response of ferroelectric ceramics primarily based on lead zirconate titanate (PZT). Under limited conditions, relatively simple analytical models were found to adequately describe the observed electrical behavior. A more complex behavior was indicated over broader conditions, however, resulting in the incorporation of shock-induced conductivity and dielectric relaxation into analytical models. Unfortunately, few experimental studies were undertaken over the next twenty years, and the development of more comprehensive models was inhibited. In recent years, a strong interest in advancing numerical simulation capabilities has motivated new experimental studies and corresponding model development. More than seventy gas gun experiments have examined several ferroelectric ceramics, with most experiments on lead zirconate titanate having a Zr:Ti ratio of 95:5 and modified with 2% niobium (PZT 95/5). This material is nominally ferroelectric but is near an antiferroelectric phase boundary, and depoling results from a shock-driven phase transition. Experiments have examined unpoled, normally poled, and axially poled PZT 95/5 over broad ranges of shock pressure and peak electric field. The extensive base of new data provides quantitative insights into both the stress and field dependencies of depoling kinetics, and the significance of pore collapse at higher stresses. The results are being actively utilized to develop and refine material response models used in numerical simulations of pulsed power devices.

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 LaAlO 3 and SrTiO 3 supports a 2D electron gas1 with high mobility of >1,000 cm 2 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). Ifmore » 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 BiFeO 3 down to the nanoscale.« less

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

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

Functional electronic inversion layers at ferroelectric domain walls

NASA Astrophysics Data System (ADS)

Mundy, J. A.; Schaab, J.; Kumagai, Y.; Cano, A.; Stengel, M.; Krug, I. P.; Gottlob, D. M.; Doğanay, H.; Holtz, M. E.; Held, R.; Yan, Z.; Bourret, E.; Schneider, C. M.; Schlom, D. G.; Muller, D. A.; Ramesh, R.; Spaldin, N. A.; Meier, D.

2017-06-01

Ferroelectric domain walls hold great promise as functional two-dimensional materials because of their unusual electronic properties. Particularly intriguing are the so-called charged walls where a polarity mismatch causes local, diverging electrostatic potentials requiring charge compensation and hence a change in the electronic structure. These walls can exhibit significantly enhanced conductivity and serve as a circuit path. The development of all-domain-wall devices, however, also requires walls with controllable output to emulate electronic nano-components such as diodes and transistors. Here we demonstrate electric-field control of the electronic transport at ferroelectric domain walls. We reversibly switch from resistive to conductive behaviour at charged walls in semiconducting ErMnO3. We relate the transition to the formation--and eventual activation--of an inversion layer that acts as the channel for the charge transport. The findings provide new insight into the domain-wall physics in ferroelectrics and foreshadow the possibility to design elementary digital devices for all-domain-wall circuitry.

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

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.

Room-temperature ferroelectric resistive switching in ultrathin Pb(Zr 0.2 Ti 0.8)O3 films.

PubMed

Pantel, Daniel; Goetze, Silvana; Hesse, Dietrich; Alexe, Marin

2011-07-26

Spontaneous polarization of ferroelectric materials has been for a long time proposed as binary information support, but it suffers so far from destructive readout. A nondestructive resistive readout of the ferroelectric polarization state in a metal-ferroelectric-metal capacitor would thus be advantageous for data storage applications. Combing conducting force microscopy and piezoelectric force microscopy, we unambiguously show that ferroelectric polarization direction and resistance state are correlated for epitaxial ferroelectric Pb(Zr(0.2)Ti(0.8))O(3) nanoscale capacitors prepared by self-assembly methods. For intermediate ferroelectric layer thickness (∼9 nm) sandwiched between copper and La(0.7)Sr(0.3)MnO(3) electrodes we achieved giant electroresistance with a resistance ratio of >1500 and high switching current densities (>10 A/cm(2)) necessary for effective resistive readout. The present approach uses metal-ferroelectric-metal devices at room temperature and, therefore, significantly advances the use of ferroelectric-based resistive switching.

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

Chemical Synthesis of Porous Barium Titanate Thin Film and Thermal Stabilization of Ferroelectric Phase by Porosity-Induced Strain.

PubMed

Suzuki, Norihiro; Osada, Minoru; Billah, Motasim; Bando, Yoshio; Yamauchi, Yusuke; Hossain, Shahriar A

2018-03-27

Barium titanate (BaTiO3, hereafter BT) is an established ferroelectric material first discovered in the 1940s and still widely used because of its well-balanced ferroelectricity, piezoelectricity, and dielectric constant. In addition, BT does not contain any toxic elements. Therefore, it is considered to be an eco-friendly material, which has attracted considerable interest as a replacement for lead zirconate titanate (PZT). However, bulk BT loses its ferroelectricity at approximately 130 °C, thus, it cannot be used at high temperatures. Because of the growing demand for high-temperature ferroelectric materials, it is important to enhance the thermal stability of ferroelectricity in BT. In previous studies, strain originating from the lattice mismatch at hetero-interfaces has been used. However, the sample preparation in this approach requires complicated and expensive physical processes, which are undesirable for practical applications. In this study, we propose a chemical synthesis of a porous material as an alternative means of introducing strain. We synthesized a porous BT thin film using a surfactant-assisted sol-gel method, in which self-assembled amphipathic surfactant micelles were used as an organic template. Through a series of studies, we clarified that the introduction of pores had a similar effect on distorting the BT crystal lattice, to that of a hetero-interface, leading to the enhancement and stabilization of ferroelectricity. Owing to its simplicity and cost effectiveness, this fabrication process has considerable advantages over conventional methods.

Chemical Synthesis of Porous Barium Titanate Thin Film and Thermal Stabilization of Ferroelectric Phase by Porosity-Induced Strain

PubMed Central

Suzuki, Norihiro; Osada, Minoru; Billah, Motasim; Bando, Yoshio; Yamauchi, Yusuke; Hossain, Shahriar A.

2018-01-01

Barium titanate (BaTiO3, hereafter BT) is an established ferroelectric material first discovered in the 1940s and still widely used because of its well-balanced ferroelectricity, piezoelectricity, and dielectric constant. In addition, BT does not contain any toxic elements. Therefore, it is considered to be an eco-friendly material, which has attracted considerable interest as a replacement for lead zirconate titanate (PZT). However, bulk BT loses its ferroelectricity at approximately 130 °C, thus, it cannot be used at high temperatures. Because of the growing demand for high-temperature ferroelectric materials, it is important to enhance the thermal stability of ferroelectricity in BT. In previous studies, strain originating from the lattice mismatch at hetero-interfaces has been used. However, the sample preparation in this approach requires complicated and expensive physical processes, which are undesirable for practical applications. In this study, we propose a chemical synthesis of a porous material as an alternative means of introducing strain. We synthesized a porous BT thin film using a surfactant-assisted sol-gel method, in which self-assembled amphipathic surfactant micelles were used as an organic template. Through a series of studies, we clarified that the introduction of pores had a similar effect on distorting the BT crystal lattice, to that of a hetero-interface, leading to the enhancement and stabilization of ferroelectricity. Owing to its simplicity and cost effectiveness, this fabrication process has considerable advantages over conventional methods. PMID:29658917

Tetragonal CH3NH3PbI3 is ferroelectric

PubMed Central

Bar-Elli, Omri; Meirzadeh, Elena; Kaslasi, Hadar; Peleg, Yagel; Hodes, Gary; Lubomirsky, Igor; Oron, Dan; Ehre, David; Cahen, David

2017-01-01

Halide perovskite (HaP) semiconductors are revolutionizing photovoltaic (PV) solar energy conversion by showing remarkable performance of solar cells made with HaPs, especially tetragonal methylammonium lead triiodide (MAPbI3). In particular, the low voltage loss of these cells implies a remarkably low recombination rate of photogenerated carriers. It was suggested that low recombination can be due to the spatial separation of electrons and holes, a possibility if MAPbI3 is a semiconducting ferroelectric, which, however, requires clear experimental evidence. As a first step, we show that, in operando, MAPbI3 (unlike MAPbBr3) is pyroelectric, which implies it can be ferroelectric. The next step, proving it is (not) ferroelectric, is challenging, because of the material’s relatively high electrical conductance (a consequence of an optical band gap suitable for PV conversion) and low stability under high applied bias voltage. This excludes normal measurements of a ferroelectric hysteresis loop, to prove ferroelectricity’s hallmark switchable polarization. By adopting an approach suitable for electrically leaky materials as MAPbI3, we show here ferroelectric hysteresis from well-characterized single crystals at low temperature (still within the tetragonal phase, which is stable at room temperature). By chemical etching, we also can image the structural fingerprint for ferroelectricity, polar domains, periodically stacked along the polar axis of the crystal, which, as predicted by theory, scale with the overall crystal size. We also succeeded in detecting clear second harmonic generation, direct evidence for the material’s noncentrosymmetry. We note that the material’s ferroelectric nature, can, but need not be important in a PV cell at room temperature. PMID:28588141

Gap-state engineering of visible-light-active ferroelectrics for photovoltaic applications.

PubMed

Matsuo, Hiroki; Noguchi, Yuji; Miyayama, Masaru

2017-08-08

Photoferroelectrics offer unique opportunities to explore light energy conversion based on their polarization-driven carrier separation and above-bandgap voltages. The problem associated with the wide bandgap of ferroelectric oxides, i.e., the vanishingly small photoresponse under visible light, has been overcome partly by bandgap tuning, but the narrowing of the bandgap is, in principle, accompanied by a substantial loss of ferroelectric polarization. In this article, we report an approach, 'gap-state' engineering, to produce photoferroelectrics, in which defect states within the bandgap act as a scaffold for photogeneration. Our first-principles calculations and single-domain thin-film experiments of BiFeO 3 demonstrate that gap states half-filled with electrons can enhance not only photocurrents but also photovoltages over a broad photon-energy range that is different from intermediate bands in present semiconductor-based solar cells. Our approach opens a promising route to the material design of visible-light-active ferroelectrics without sacrificing spontaneous polarization.Overcoming the optical transparency of wide bandgap of ferroelectric oxides by narrowing its bandgap tends to result in a loss of polarization. By utilizing defect states within the bandgap, Matsuo et al. report visible-light-active ferroelectrics without sacrificing polarization.

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

Ferroelectric polarization-controlled two-dimensional electron gas in ferroelectric/AlGaN/GaN heterostructure

NASA Astrophysics Data System (ADS)

Kong, Y. C.; Xue, F. S.; Zhou, J. J.; Li, L.; Chen, C.; Li, Y. R.

2009-06-01

The control effect of the ferroelectric polarization on the two-dimensional electron gas (2DEG) in a ferroelectric/AlGaN/GaN metal-ferroelectric-semiconductor (MFS) structure is theoretically analyzed by a self-consistent approach. With incorporating the hysteresis nature of the ferroelectric into calculation, the nature of the control effect is disclosed, where the 2DEG density is depleted/restored after poling/depoling operation on the MFS structure. The orientation of the ferroelectric polarization is clarified to be parallel to that of the AlGaN barrier, which, based on an electrostatics analysis, is attributed to the pinning effect of the underlying polarization. Reducing the thickness of the AlGaN barrier from 25 nm to 20 nm leads to an improved control modulation of the 2DEG density from 36.7% to 54.1%.

Tunable ferroelectric polarization and its interplay with spin-orbit coupling in tin iodide perovskites

NASA Astrophysics Data System (ADS)

Stroppa, Alessandro; di Sante, Domenico; Barone, Paolo; Bokdam, Menno; Kresse, Georg; Franchini, Cesare; Whangbo, Myung-Hwan; Picozzi, Silvia

2014-12-01

Ferroelectricity is a potentially crucial issue in halide perovskites, breakthrough materials in photovoltaic research. Using density functional theory simulations and symmetry analysis, we show that the lead-free perovskite iodide (FA)SnI3, containing the planar formamidinium cation FA, (NH2CHNH2)+, is ferroelectric. In fact, the perpendicular arrangement of FA planes, leading to a ‘weak’ polarization, is energetically more stable than parallel arrangements of FA planes, being either antiferroelectric or ‘strong’ ferroelectric. Moreover, we show that the ‘weak’ and ‘strong’ ferroelectric states with the polar axis along different crystallographic directions are energetically competing. Therefore, at least at low temperatures, an electric field could stabilize different states with the polarization rotated by π/4, resulting in a highly tunable ferroelectricity appealing for multistate logic. Intriguingly, the relatively strong spin-orbit coupling in noncentrosymmetric (FA)SnI3 gives rise to a co-existence of Rashba and Dresselhaus effects and to a spin texture that can be induced, tuned and switched by an electric field controlling the ferroelectric state.

Random electric field instabilities of relaxor ferroelectrics

NASA Astrophysics Data System (ADS)

Arce-Gamboa, José R.; Guzmán-Verri, Gian G.

2017-06-01

Relaxor ferroelectrics are complex oxide materials which are rather unique to study the effects of compositional disorder on phase transitions. Here, we study the effects of quenched cubic random electric fields on the lattice instabilities that lead to a ferroelectric transition and show that, within a microscopic model and a statistical mechanical solution, even weak compositional disorder can prohibit the development of long-range order and that a random field state with anisotropic and power-law correlations of polarization emerges from the combined effect of their characteristic dipole forces and their inherent charge disorder. We compare and reproduce several key experimental observations in the well-studied relaxor PbMg1/3Nb2/3O3-PbTiO3.

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

Giant electrocaloric effect in a cracked ferroelectrics

NASA Astrophysics Data System (ADS)

Huang, Cheng; Yang, Hai-Bing; Gao, Cun-Fa

2018-04-01

The electrocaloric effect (ECE) is the temperature change in a material induced by electrical field variation under adiabatic condition. Considering an external electric load applied on a cracked ferroelectric solid, a non-uniform electric field would be induced at the crack tip, and thus, incompatible strain field and local stress concentration would be generated around it. Furthermore, the enormous strain energy and the electrostatic energy would affect the polarization switching of the ferroelectric solid, important for the electrocaloric response. In this paper, the large negative and positive ECEs in a ferroelectric sheet with a conducting crack are investigated by the phase field method with the consideration of time-dependent Ginzburg-Landau equation. The numerical calculations indicated that the polarization field generates a sharp rise during the domain transition from polydomain to monodomain under a certain electric load. Large negative ECEs, about -10.21 K and -7.55 K, are obtained at 135 °C and 85 °C, respectively. The domain transition temperature is much lower than the Curie temperature, which enlarges the existence scope of the large ECE in ferroelectrics. The results also imply that the domain transition from a multi-domain state to a single domain takes place with the minimization of total free energy, which involves the courses of the electric field, stress field, temperature, and polarization interaction. Therefore, the non-uniform distributions of the stress-electric fields induced by the crack play an important role in ECE.

Ultrahigh piezoelectricity in ferroelectric ceramics by design

NASA Astrophysics Data System (ADS)

Li, Fei; Lin, Dabin; Chen, Zibin; Cheng, Zhenxiang; Wang, Jianli; Li, ChunChun; Xu, Zhuo; Huang, Qianwei; Liao, Xiaozhou; Chen, Long-Qing; Shrout, Thomas R.; Zhang, Shujun

2018-03-01

Piezoelectric materials, which respond mechanically to applied electric field and vice versa, are essential for electromechanical transducers. Previous theoretical analyses have shown that high piezoelectricity in perovskite oxides is associated with a flat thermodynamic energy landscape connecting two or more ferroelectric phases. Here, guided by phenomenological theories and phase-field simulations, we propose an alternative design strategy to commonly used morphotropic phase boundaries to further flatten the energy landscape, by judiciously introducing local structural heterogeneity to manipulate interfacial energies (that is, extra interaction energies, such as electrostatic and elastic energies associated with the interfaces). To validate this, we synthesize rare-earth-doped Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT), as rare-earth dopants tend to change the local structure of Pb-based perovskite ferroelectrics. We achieve ultrahigh piezoelectric coefficients d33 of up to 1,500 pC N-1 and dielectric permittivity ɛ33/ɛ0 above 13,000 in a Sm-doped PMN-PT ceramic with a Curie temperature of 89 °C. Our research provides a new paradigm for designing material properties through engineering local structural heterogeneity, expected to benefit a wide range of functional materials.

Ultrahigh piezoelectricity in ferroelectric ceramics by design.

PubMed

Li, Fei; Lin, Dabin; Chen, Zibin; Cheng, Zhenxiang; Wang, Jianli; Li, ChunChun; Xu, Zhuo; Huang, Qianwei; Liao, Xiaozhou; Chen, Long-Qing; Shrout, Thomas R; Zhang, Shujun

2018-04-01

Piezoelectric materials, which respond mechanically to applied electric field and vice versa, are essential for electromechanical transducers. Previous theoretical analyses have shown that high piezoelectricity in perovskite oxides is associated with a flat thermodynamic energy landscape connecting two or more ferroelectric phases. Here, guided by phenomenological theories and phase-field simulations, we propose an alternative design strategy to commonly used morphotropic phase boundaries to further flatten the energy landscape, by judiciously introducing local structural heterogeneity to manipulate interfacial energies (that is, extra interaction energies, such as electrostatic and elastic energies associated with the interfaces). To validate this, we synthesize rare-earth-doped Pb(Mg 1/3 Nb 2/3 )O 3 -PbTiO 3 (PMN-PT), as rare-earth dopants tend to change the local structure of Pb-based perovskite ferroelectrics. We achieve ultrahigh piezoelectric coefficients d 33 of up to 1,500 pC N -1 and dielectric permittivity ε 33 /ε 0 above 13,000 in a Sm-doped PMN-PT ceramic with a Curie temperature of 89 °C. Our research provides a new paradigm for designing material properties through engineering local structural heterogeneity, expected to benefit a wide range of functional materials.

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.

Selective control of multiple ferroelectric switching pathways using a trailing flexoelectric field

NASA Astrophysics Data System (ADS)

Park, Sung Min; Wang, Bo; Das, Saikat; Chae, Seung Chul; Chung, Jin-Seok; Yoon, Jong-Gul; Chen, Long-Qing; Yang, Sang Mo; Noh, Tae Won

2018-05-01

Flexoelectricity is an electromechanical coupling between electrical polarization and a strain gradient1 that enables mechanical manipulation of polarization without applying an electrical bias2,3. Recently, flexoelectricity was directly demonstrated by mechanically switching the out-of-plane polarization of a uniaxial system with a scanning probe microscope tip3,4. However, the successful application of flexoelectricity in low-symmetry multiaxial ferroelectrics and therefore active manipulation of multiple domains via flexoelectricity have not yet been achieved. Here, we demonstrate that the symmetry-breaking flexoelectricity offers a powerful route for the selective control of multiple domain switching pathways in multiaxial ferroelectric materials. Specifically, we use a trailing flexoelectric field that is created by the motion of a mechanically loaded scanning probe microscope tip. By controlling the SPM scan direction, we can deterministically select either stable 71° ferroelastic switching or 180° ferroelectric switching in a multiferroic magnetoelectric BiFeO3 thin film. Phase-field simulations reveal that the amplified in-plane trailing flexoelectric field is essential for this domain engineering. Moreover, we show that mechanically switched domains have a good retention property. This work opens a new avenue for the deterministic selection of nanoscale ferroelectric domains in low-symmetry materials for non-volatile magnetoelectric devices and multilevel data storage.

Phase diagrams of ferroelectric nanocrystals strained by an elastic matrix

NASA Astrophysics Data System (ADS)

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

2018-01-01

Ferroelectric crystallites embedded into a dielectric matrix experience temperature-dependent elastic strains caused by differences in the thermal expansion of the crystallites and the matrix. Owing to the electrostriction, these lattice strains may affect polarization states of ferroelectric inclusions significantly, making them different from those of a stress-free bulk crystal. Here, using a nonlinear thermodynamic theory, we study the mechanical effect of elastic matrix on the phase states of embedded single-domain ferroelectric nanocrystals. Their equilibrium polarization states are determined by minimizing a special thermodynamic potential that describes the energetics of an ellipsoidal ferroelectric inclusion surrounded by a linear elastic medium. To demonstrate the stability ranges of such states for a given material combination, we construct a phase diagram, where the inclusion’s shape anisotropy and temperature are used as two parameters. The ‘shape-temperature’ phase diagrams are calculated numerically for PbTiO3 and BaTiO3 nanocrystals embedded into representative dielectric matrices generating tensile (silica glass) or compressive (potassium silicate glass) thermal stresses inside ferroelectric inclusions. The developed phase maps demonstrate that the joint effect of thermal stresses and matrix-induced elastic clamping of ferroelectric inclusions gives rise to several important features in the polarization behavior of PbTiO3 and BaTiO3 nanocrystals. In particular, the Curie temperature displays a nonmonotonic variation with the ellipsoid’s aspect ratio, being minimal for spherical inclusions. Furthermore, the diagrams show that the polarization orientation with respect to the ellipsoid’s symmetry axis is controlled by the shape anisotropy and the sign of thermal stresses. Under certain conditions, the mechanical inclusion-matrix interaction qualitatively alters the evolution of ferroelectric states on cooling, inducing a structural transition

Giant Rashba spin splitting in Bi bilayer induced by a 2D ferroelectric substrate

NASA Astrophysics Data System (ADS)

Zhu, Jianbao; Xiao, Di; Zhu, Wenguang

Based on density functional theory calculations, we discover that a Bi layer when placed on the top of a recently predicted 2D ferroelectric material with spontaneous out-of-plane electric polarization can exhibit giant Rashba-type spin splitting of over 200 meV, while the whole system still remains semiconducting. In addition, the magnitude of the Rashba spin splitting can be tuned by switching the diploe orientation of the 2D ferroelectric substrate. This finding provides a promising 2D material system for spintronics.

Ferroelectric properties of Pb(Zr,Ti)O3 films under ion-beam induced strain

NASA Astrophysics Data System (ADS)

Lee, Jung-Kun; Nastasi, Michael

2012-11-01

The influence of an ion-beam induced biaxial stress on the ferroelectric and dielectric properties of Pb(Zr,Ti)O3 (PZT) films is investigated using the ion beam process as a novel approach to control external stress. Tensile stress is observed to decrease the polarization, permittivity, and ferroelectric fatigue resistance of the PZT films whose structure is monoclinic. However, a compressive stress increases all of them in monoclinic PZT films. The dependence of the permittivity on stress is found not to follow the phenomenological theory relating external forces to intrinsic properties of ferroelectric materials. Changes in the ferroelectric and dielectric properties indicate that the application of a biaxial stress modulates both extrinsic and intrinsic properties of PZT films. Different degrees of dielectric non-linearity suggests the density and mobility of non-180o domain walls, and the domain switching can be controlled by an applied biaxial stress and thereby influence the ferroelectric and dielectric properties.

Rewritable ferroelectric vortex pairs in BiFeO3

NASA Astrophysics Data System (ADS)

Li, Yang; Jin, Yaming; Lu, Xiaomei; Yang, Jan-Chi; Chu, Ying-Hao; Huang, Fengzhen; Zhu, Jinsong; Cheong, Sang-Wook

2017-08-01

Ferroelectric vortex in multiferroic materials has been considered as a promising alternative to current memory cells for the merit of high storage density. However, the formation of regular natural ferroelectric vortex is difficult, restricting the achievement of vortex memory device. Here, we demonstrated the creation of ferroelectric vortex-antivortex pairs in BiFeO3 thin films by using local electric field. The evolution of the polar vortex structure is studied by piezoresponse force microscopy at nanoscale. The results reveal that the patterns and stability of vortex structures are sensitive to the poling position. Consecutive writing and erasing processes cause no influence on the original domain configuration. The Z4 proper coloring vortex-antivortex network is then analyzed by graph theory, which verifies the rationality of artificial vortex-antivortex pairs. This study paves a foundation for artificial regulation of vortex, which provides a possible pathway for the design and realization of non-volatile vortex memory devices and logical devices.

Non-volatile memory based on the ferroelectric photovoltaic effect

PubMed Central

Guo, Rui; You, Lu; Zhou, Yang; Shiuh Lim, Zhi; Zou, Xi; Chen, Lang; Ramesh, R.; Wang, Junling

2013-01-01

The quest for a solid state universal memory with high-storage density, high read/write speed, random access and non-volatility has triggered intense research into new materials and novel device architectures. Though the non-volatile memory market is dominated by flash memory now, it has very low operation speed with ~10 μs programming and ~10 ms erasing time. Furthermore, it can only withstand ~105 rewriting cycles, which prevents it from becoming the universal memory. Here we demonstrate that the significant photovoltaic effect of a ferroelectric material, such as BiFeO3 with a band gap in the visible range, can be used to sense the polarization direction non-destructively in a ferroelectric memory. A prototype 16-cell memory based on the cross-bar architecture has been prepared and tested, demonstrating the feasibility of this technique. PMID:23756366

Topological phase transformations and intrinsic size effects in ferroelectric nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mangeri, John; Espinal, Yomery; Jokisaari, Andrea M.

Here, 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 PbTiO 3 or BaTiO 3 nanoparticles embedded in a dielectric medium, including air. The equilibrium polarization topology is strongly affected by particlemore » 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 PbTiO 3 particle, this size is 2 and 3.4 nm, respectively, for high- and low-permittivity media. For the BaTiO 3 particle, it is ~3.6 nm regardless of the medium dielectric strength.« less

Topological phase transformations and intrinsic size effects in ferroelectric nanoparticles

DOE PAGES

Mangeri, John; Espinal, Yomery; Jokisaari, Andrea M.; ...

2017-01-06

Here, 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 PbTiO 3 or BaTiO 3 nanoparticles embedded in a dielectric medium, including air. The equilibrium polarization topology is strongly affected by particlemore » 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 PbTiO 3 particle, this size is 2 and 3.4 nm, respectively, for high- and low-permittivity media. For the BaTiO 3 particle, it is ~3.6 nm regardless of the medium dielectric strength.« less

Analysis and design of ferroelectric-based smart antenna structures

NASA Astrophysics Data System (ADS)

Ramesh, Prashanth; Washington, Gregory N.

2009-03-01

Ferroelectrics in microwave antenna systems offer benefits of electronic tunability, compact size and light weight, speed of operation, high power-handling, low dc power consumption, and potential for low loss and cost. Ferroelectrics allow for the tuning of microwave devices by virtue of the nonlinear dependence of their dielectric permittivity on an applied electric field. Experiments on the field-polarization dependence of ferroelectric thin films show variation in dielectric permittivity of up to 50%. This is in contrast to the conventional dielectric materials used in electrical devices which have a relatively constant permittivity, indicative of the linear field-polarization curve. Ferroelectrics, with their variable dielectric constant introduce greater flexibility in correction and control of beam shapes and beam direction of antenna structures. The motivation behind this research is applying ferroelectrics to mechanical load bearing antenna structures, but in order to develop such structures, we need to understand not just the field-permittivity dependence, but also the coupled electro-thermo-mechanical behavior of ferroelectrics. In this paper, two models are discussed: a nonlinear phenomenological model relating the applied fields, strains and temperature to the dielectric permittivity based on the Devonshire thermodynamic framework, and a phenomenological model relating applied fields and temperature to the dielectric loss tangent. The models attempt to integrate the observed field-permittivity, strain-permittivity and temperature-permittivity behavior into one single unified model and extend the resulting model to better fit experimental data. Promising matches with experimental data are obtained. These relations, coupled with the expression for operating frequency vs. the permittivity are then used to understand the bias field vs. frequency behavior of the antenna. Finally, the effect of the macroscopic variables on the antenna radiation efficiency is

A lead-halide perovskite molecular ferroelectric semiconductor

PubMed Central

Liao, Wei-Qiang; Zhang, Yi; Hu, Chun-Li; Mao, Jiang-Gao; Ye, Heng-Yun; Li, Peng-Fei; Huang, Songping D.; Xiong, Ren-Gen

2015-01-01

Inorganic semiconductor ferroelectrics such as BiFeO3 have shown great potential in photovoltaic and other applications. Currently, semiconducting properties and the corresponding application in optoelectronic devices of hybrid organo-plumbate or stannate are a hot topic of academic research; more and more of such hybrids have been synthesized. Structurally, these hybrids are suitable for exploration of ferroelectricity. Therefore, the design of molecular ferroelectric semiconductors based on these hybrids provides a possibility to obtain new or high-performance semiconductor ferroelectrics. Here we investigated Pb-layered perovskites, and found the layer perovskite (benzylammonium)2PbCl4 is ferroelectric with semiconducting behaviours. It has a larger ferroelectric spontaneous polarization Ps=13 μC cm−2 and a higher Curie temperature Tc=438 K with a band gap of 3.65 eV. This finding throws light on the new properties of the hybrid organo-plumbate or stannate compounds and provides a new way to develop new semiconductor ferroelectrics. PMID:26021758

Optimal configuration of microstructure in ferroelectric materials by stochastic optimization

NASA Astrophysics Data System (ADS)

Jayachandran, K. P.; Guedes, J. M.; Rodrigues, H. C.

2010-07-01

An optimization procedure determining the ideal configuration at the microstructural level of ferroelectric (FE) materials is applied to maximize piezoelectricity. Piezoelectricity in ceramic FEs differs significantly from that of single crystals because of the presence of crystallites (grains) possessing crystallographic axes aligned imperfectly. The piezoelectric properties of a polycrystalline (ceramic) FE is inextricably related to the grain orientation distribution (texture). The set of combination of variables, known as solution space, which dictates the texture of a ceramic is unlimited and hence the choice of the optimal solution which maximizes the piezoelectricity is complicated. Thus, a stochastic global optimization combined with homogenization is employed for the identification of the optimal granular configuration of the FE ceramic microstructure with optimum piezoelectric properties. The macroscopic equilibrium piezoelectric properties of polycrystalline FE is calculated using mathematical homogenization at each iteration step. The configuration of grains characterized by its orientations at each iteration is generated using a randomly selected set of orientation distribution parameters. The optimization procedure applied to the single crystalline phase compares well with the experimental data. Apparent enhancement of piezoelectric coefficient d33 is observed in an optimally oriented BaTiO3 single crystal. Based on the good agreement of results with the published data in single crystals, we proceed to apply the methodology in polycrystals. A configuration of crystallites, simultaneously constraining the orientation distribution of the c-axis (polar axis) while incorporating ab-plane randomness, which would multiply the overall piezoelectricity in ceramic BaTiO3 is also identified. The orientation distribution of the c-axes is found to be a narrow Gaussian distribution centered around 45°. The piezoelectric coefficient in such a ceramic is found to

Domain switching mechanisms in polycrystalline ferroelectrics with asymmetric hysteretic behavior

NASA Astrophysics Data System (ADS)

Anton, Eva-Maria; García, R. Edwin; Key, Thomas S.; Blendell, John E.; Bowman, Keith J.

2009-01-01

A numerical method is presented to predict the effect of microstructure on the local polarization switching of bulk ferroelectric ceramics. The model shows that a built-in electromechanical field develops in a ferroelectric material as a result of the spatial coupling of the grains and the direct physical coupling between the thermomechanical and electromechanical properties of a bulk ceramic material. The built-in fields that result from the thermomechanically induced grain-grain electromechanical interactions result in the appearance of four microstructural switching mechanisms: (1) simple switching, where the c-axes of ferroelectric domains will align with the direction of the applied macroscopic electric field by starting from the core of each grain; (2) grain boundary induced switching, where the domain's switching response will initiate at grain corners and boundaries as a result of the polarization and stress that is locally generated from the strong anisotropy of the dielectric permittivity and the local piezoelectric contributions to polarization from the surrounding material; (3) negative poling, where abutting ferroelectric domains of opposite polarity actively oppose domain switching by increasing their degree of tetragonality by interacting with the surrounding domains that have already switched to align with the applied electrostatic field. Finally, (4) domain reswitching mechanism is observed at very large applied electric fields, and is characterized by the appearance of polarization domain reversals events in the direction of their originally unswitched state. This mechanism is a consequence of the competition between the macroscopic applied electric field, and the induced electric field that results from the neighboring domains (or grains) interactions. The model shows that these built-in electromechanical fields and mesoscale mechanisms contribute to the asymmetry of the macroscopic hysteretic behavior in poled samples. Furthermore, below a

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.

Random electric field instabilities of relaxor ferroelectrics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Arce-Gamboa, Jose R.; Guzman-Verri, Gian G.

Relaxor ferroelectrics are complex oxide materials which are rather unique to study the effects of compositional disorder on phase transitions. Here, we study the effects of quenched cubic random electric fields on the lattice instabilities that lead to a ferroelectric transition and show that, within a microscopic model and a statistical mechanical solution, even weak compositional disorder can prohibit the development of long-range order and that a random field state with anisotropic and power-law correlations of polarization emerges from the combined effect of their characteristic dipole forces and their inherent charge disorder. As a result, we compare and reproduce severalmore » key experimental observations in the well-studied relaxor PbMg 1/3Nb 2/3O 3–PbTiO 3.« less

Random electric field instabilities of relaxor ferroelectrics

DOE PAGES

Arce-Gamboa, Jose R.; Guzman-Verri, Gian G.

2017-06-13

Relaxor ferroelectrics are complex oxide materials which are rather unique to study the effects of compositional disorder on phase transitions. Here, we study the effects of quenched cubic random electric fields on the lattice instabilities that lead to a ferroelectric transition and show that, within a microscopic model and a statistical mechanical solution, even weak compositional disorder can prohibit the development of long-range order and that a random field state with anisotropic and power-law correlations of polarization emerges from the combined effect of their characteristic dipole forces and their inherent charge disorder. As a result, we compare and reproduce severalmore » key experimental observations in the well-studied relaxor PbMg 1/3Nb 2/3O 3–PbTiO 3.« less

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

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)

Recent Progress in Understanding the Shock Response of Ferroelectric Ceramics*

NASA Astrophysics Data System (ADS)

Setchell, Robert E.

2001-06-01

Ferroelectric ceramics exhibit a permanent remanent polarization, and the use of shock depoling of these materials to achieve pulsed sources of electrical power was proposed in the late 1950s. During the following twenty years, extensive studies were conducted to examine the shock response of ferroelectric ceramics primarily based on lead zirconate titanate (PZT). Under limited conditions, relatively simple analytical models were found to adequately describe the observed electrical behavior. In general, however, the studies indicated a complex behavior involving finite-rate depoling kinetics with stress and field dependencies. Dielectric relaxation and shock-induced conductivity were also suggested. Unfortunately, few experimental studies were undertaken over the next twenty years, and the development of more comprehensive models was inhibited. In recent years, a strong interest in advancing numerical simulation capabilities has motivated new experimental studies and corresponding model development. More than seventy gas gun experiments have examined several ferroelectric ceramics, with most experiments on lead zirconate titanate having a Zr:Ti ratio of 95:5 and modified with 2ferroelectric but is near an antiferroelectric phase boundary, and depoling results from a shock-driven phase transition. Experiments have examined unpoled, normally poled, and axially poled PZT 95/5 over broad ranges of shock pressure and peak electric field. The extensive base of new data provides quantitative insights into the stress and field dependencies of depoling kinetics and dielectric properties, and is being actively utilized to develop and refine material response models used in numerical simulations of pulsed power devices.

Chemical Changes in Layered Ferroelectric Semiconductors Induced by Helium Ion Beam

DOE Office of Scientific and Technical Information (OSTI.GOV)

Belianinov, Alex; Burch, Matthew J.; Hysmith, Holland E.

Transitioning to multi-material systems as either interfaced 2D materials or 3D heterostructures can lead to the next generation multi-functional device architectures. Combined direct physical and chemical nanoscale control of these systems offers a new way to tailor material and device functionality as functional structures reach their physical limit. Transition metal thiophosphate (TPS), Cu 1-xIn 1+x/3P 2S 6, that have ferroelectric polarization behavior as layered crystals at room temperature and above make them attractive candidates for direct material sculpting of both chemical and functional properties. The bulk material exhibits stable ferroelectric polarization corroborated by domain structures, rewritable polarization, and hysteresis loops.more » Our previous studies have demonstrated that ferroic order persists on the surface and that spinoidal decomposition of ferroelectric and paraelectric phases occurs in non-stoichiometric Cu/In ratio formulations. Here, we elucidate the chemical changes induced through helium ion irradiation in the TPS family library with varying Cu/In ratio formulations using correlated AFM and ToF-SIMS imaging. We correlate nano- and micro- structures that scale, in area and volume, to the total dose of the helium ion beam, as well as the overall copper concentration in the sample. Furthermore, our ToF-SIMS results show that ion irradiation leads to oxygen penetration as a function of Cu concentration, and proceeds along the Cu domains to the stopping distance of the helium ions in the TPS material. These results opens up new opportunities to understand and implement ferroicly coupled van der Waal devices into an existing framework of 2D heterostructures by locally tuning material chemistry and functionality.« less

Chemical Changes in Layered Ferroelectric Semiconductors Induced by Helium Ion Beam

DOE PAGES

Belianinov, Alex; Burch, Matthew J.; Hysmith, Holland E.; ...

2017-11-30

Transitioning to multi-material systems as either interfaced 2D materials or 3D heterostructures can lead to the next generation multi-functional device architectures. Combined direct physical and chemical nanoscale control of these systems offers a new way to tailor material and device functionality as functional structures reach their physical limit. Transition metal thiophosphate (TPS), Cu 1-xIn 1+x/3P 2S 6, that have ferroelectric polarization behavior as layered crystals at room temperature and above make them attractive candidates for direct material sculpting of both chemical and functional properties. The bulk material exhibits stable ferroelectric polarization corroborated by domain structures, rewritable polarization, and hysteresis loops.more » Our previous studies have demonstrated that ferroic order persists on the surface and that spinoidal decomposition of ferroelectric and paraelectric phases occurs in non-stoichiometric Cu/In ratio formulations. Here, we elucidate the chemical changes induced through helium ion irradiation in the TPS family library with varying Cu/In ratio formulations using correlated AFM and ToF-SIMS imaging. We correlate nano- and micro- structures that scale, in area and volume, to the total dose of the helium ion beam, as well as the overall copper concentration in the sample. Furthermore, our ToF-SIMS results show that ion irradiation leads to oxygen penetration as a function of Cu concentration, and proceeds along the Cu domains to the stopping distance of the helium ions in the TPS material. These results opens up new opportunities to understand and implement ferroicly coupled van der Waal devices into an existing framework of 2D heterostructures by locally tuning material chemistry and functionality.« less

Universal Ferroelectric Switching Dynamics of Vinylidene Fluoride-trifluoroethylene Copolymer Films

PubMed Central

Hu, Wei Jin; Juo, Deng-Ming; You, Lu; Wang, Junling; Chen, Yi-Chun; Chu, Ying-Hao; Wu, Tom

2014-01-01

In this work, switching dynamics of poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] copolymer films are investigated over unprecedentedly wide ranges of temperature and electric field. Remarkably, domain switching of copolymer films obeys well the classical domain nucleation and growth model although the origin of ferroelectricity in organic ferroelectric materials inherently differs from the inorganic counterparts. A lower coercivity limit of 50 MV/m and 180° domain wall energy of 60 mJ/m2 are determined for P(VDF-TrFE) films. Furthermore, we discover in copolymer films an anomalous temperature-dependent crossover behavior between two power-law scaling regimes of frequency-dependent coercivity, which is attributed to the transition between flow and creep motions of domain walls. Our observations shed new light on the switching dynamics of semi-crystalline ferroelectric polymers, and such understandings are critical for realizing their reliable applications. PMID:24759786

Active control of magnetoresistance of organic spin valves using ferroelectricity

PubMed Central

Sun, Dali; Fang, Mei; Xu, Xiaoshan; Jiang, Lu; Guo, Hangwen; Wang, Yanmei; Yang, Wenting; Yin, Lifeng; Snijders, Paul C.; Ward, T. Z.; Gai, Zheng; Zhang, X.-G.; Lee, Ho Nyung; Shen, Jian

2014-01-01

Organic spintronic devices have been appealing because of the long spin lifetime of the charge carriers in the organic materials and their low cost, flexibility and chemical diversity. In previous studies, the control of resistance of organic spin valves is generally achieved by the alignment of the magnetization directions of the two ferromagnetic electrodes, generating magnetoresistance. Here we employ a new knob to tune the resistance of organic spin valves by adding a thin ferroelectric interfacial layer between the ferromagnetic electrode and the organic spacer: the magnetoresistance of the spin valve depends strongly on the history of the bias voltage, which is correlated with the polarization of the ferroelectric layer; the magnetoresistance even changes sign when the electric polarization of the ferroelectric layer is reversed. These findings enable active control of resistance using both electric and magnetic fields, opening up possibility for multi-state organic spin valves. PMID:25008155

Ferroelectric polarization induces electric double layer bistability in electrolyte-gated field-effect transistors.

PubMed

Fabiano, Simone; Crispin, Xavier; Berggren, Magnus

2014-01-08

The dense surface charges expressed by a ferroelectric polymeric thin film induce ion displacement within a polyelectrolyte layer and vice versa. This is because the density of dipoles along the surface of the ferroelectric thin film and its polarization switching time matches that of the (Helmholtz) electric double layers formed at the ferroelectric/polyelectrolyte and polyelectrolyte/semiconductor interfaces. This combination of materials allows for introducing hysteresis effects in the capacitance of an electric double layer capacitor. The latter is advantageously used to control the charge accumulation in the semiconductor channel of an organic field-effect transistor. The resulting memory transistors can be written at a gate voltage of around 7 V and read out at a drain voltage as low as 50 mV. The technological implication of this large difference between write and read-out voltages lies in the non-destructive reading of this ferroelectric memory.

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.

Evaluation of the density of the charge trapped in organic ferroelectric capacitors based on the Mott-Schottky model

NASA Astrophysics Data System (ADS)

Kim, Won-Ho; Kwon, Jin-Hyuk; Park, Gyeong-Tae; Kim, Jae-Hyun; Bae, Jin-Hyuk; Zhang, Xue; Park, Jaehoon

2014-09-01

Organic ferroelectric capacitors were fabricated using pentacene and poly(vinylidene fluoride-trifluoroethylene) (PVDF-TrFE) as an organic semiconductor and a ferroelectric material, respectively. A paraelectric poly(vinyl cinnamate) layer was adopted as an interlayer between the PVDF-TrFE layer and the bottom electrode. The paraelectric interlayer induced a depolarization field opposite to the direction of the polarization formed in the ferroelectric PVDF-TrFE insulator, thereby suppressing spontaneous polarization. As a result, the Mott-Schottky model could be used to evaluate, from the extracted flat-band voltages, the density of the charge trapped in the organic ferroelectric capacitors.

Re-entrant relaxor ferroelectricity of methylammonium lead iodide

DOE PAGES

Guo, Haiyan; Liu, Peixue; Zheng, Shichao; ...

2016-09-24

In this paper, we have performed a piezoresponse force microscopy (PFM) study on methylammonium lead iodide (MAPbI 3) thin films in normal (non-resonance, non-band-excitation) contact mode. In contrast to the ferroelectric Pb 0.76Ca 0.24TiO 3 (PCT) control sample, a typical ferroelectric response was not observed. However, a nonlinear electric field dependence of the local PFM amplitude was found in MAPbI 3, similar to PCT. An analysis combining results on structure, dielectric dispersion, and weak ferroelectricity demonstrates that MAPbI 3 is actually a re-entrant relaxor ferroelectric which, upon cooling, enters into a relaxor phase below its ferroelectric phase transition at ~327more » K, due to the balance between the long range ferroelectric order and structural methylammonium group orientational disorder. The ferroelectricity at room temperature is compromised due to the re-entrant relaxor behavior, causing the poor polarization retention or weak ferroelectricity. Finally, our findings essentially conciliate the conflicting experimental results on MAPbI 3's ferroelectricity and are beneficial both for basic understanding as well as for device applications.« less

K-Band Reflectarray Antenna Based on Ferroelectric Thin Films: What Have We Learned so Far

NASA Technical Reports Server (NTRS)

Miranda, Felix A.; Romanofsky, Robert; Mueller, Carl H.; VanKeuls, Fred

2002-01-01

The Applied RF Technology Branch of the NASA Glenn Research Center, Cleveland, Ohio, has an on-going effort in the area of thin film ferroelectric technology for microwave applications. Particular attention has been given to developing ferroelectric phase shifters for the implementation and experimental demonstration of an electronically steerable reflectarray antenna. In the process of optimizing these material to fit the implementation requirements of the aforementioned antenna, we have accumulated a great deal of information and knowledge in areas such as the effect of the composition of the ferroelectric thin films on phase shifter performance, self assembled monolayers (SAMs) in the metallic/ferroelectric interface and their impact on phase shifter performance, correlation between microstructure and microwave properties, and the effect of selective etching on the overall performance of a thin film-ferroelectric based microwave component, amongst others. We will discuss these issues and will provide an up-dade of the current development status of the reflect-array antenna.

Electron emission from ferroelectrics - a review

NASA Astrophysics Data System (ADS)

Riege, H.

1994-02-01

The strong pulsed emission of electrons from the surface of ferroelectric (FE) materials was discovered at CERN in 1987. Since then many aspects and properties of the method of generation and propagation of electron beams from FE have been studied experimentally. The method is based on macroscopic charge separation and self-emission of electrons under the influence of their own space-charge fields. Hence, this type of emission is not limited by the Langmuir-Child law as are conventional emission methods. Charge separation and electron emission can be achieved by rapid switching of the spontaneous, ferroelectric polarization. Polarization switching may be induced by application of electrical-field or mechanical-pressure pulses, as well as by thermal heating or laser illumination of the ferroelectric emitter. At higher emission intensities plasma formation assists the FE emission and leads to a strong growth of emitted current amplitude, which is no longer limited by the FE material and the surface properties. The most attractive features of FE emission are robustness and ease of manipulation of the emitter cathodes which can be transported through atmospheric air and used without any problems in vacuum, low-pressure gas or plasma environments. Large-area arrangements of multiple emitters, switched in interleaved mode, can produce electron beams of any shape, current amplitude or time structure. The successful application of FE emission in accelerator technology has been demonstrated experimentally in several cases, e.g. for triggering high-power gas switches, for photocathodes in electron guns, and for electron-beam generators intended to generate, neutralize and enhance ion beams in ion sources and ion linacs. Other applications can be envisaged in microwave power generators and in the fields of electronics and vacuum microelectronics.

Piezoelectricity and ferroelectricity of cellular polypropylene electrets films characterized by piezoresponse force microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miao, Hongchen; Sun, Yao; Zhou, Xilong

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 thanmore » 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.« less

Ferroelectricity, Antiferroelectricity, and Ultrathin 2D Electron/Hole Gas in Multifunctional Monolayer MXene.

PubMed

Chandrasekaran, Anand; Mishra, Avanish; Singh, Abhishek Kumar

2017-05-10

The 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 (Sc 2 CO 2 ). The switching of polarization in this new class of ferroelectric materials occurs through a previously unknown intermediate antiferroelectric structure, thus establishing three states for applications in low-dimensional nonvolatile 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 nondegenerate 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.

Patterned Ferroelectric Films for Tunable Microwave Devices

NASA Technical Reports Server (NTRS)

Miranda, Felix A.; Mueller, Carl H.

2008-01-01

Tunable microwave devices based on metal terminals connected by thin ferroelectric films can be made to perform better by patterning the films to include suitably dimensioned, positioned, and oriented constrictions. The patterns can be formed during fabrication by means of selective etching processes. If the width of the ferroelectric film in such a device is reduced at one or more locations, then both the microwave field and any applied DC bias (tuning) electric field become concentrated at those locations. The magnitudes of both the permittivity and the dielectric loss of a ferroelectric material are reduced by application of a DC field. Because the concentration of the DC field in the constriction(s) magnifies the permittivity- and loss-reducing effects of the applied DC voltage, the permittivity and dielectric loss in the constriction(s) are smaller in the constriction(s) than they are in the wider parts of the ferroelectric film. Furthermore, inasmuch as displacement current must flow through either the constriction(s) or the low-loss dielectric substrate, the net effect of the constriction(s) is equivalent to that of incorporating one or more low-loss, low-permittivity region(s) in series with the high-loss, high-permittivity regions. In a series circuit, the properties of the low-capacitance series element (in this case, the constriction) dominate the overall performance. Concomitantly, the capacitance between the metal terminals is reduced. By making the capacitance between the metal terminals small but tunable, a constriction increases the upper limit of the frequency range amenable to ferroelectric tuning. The present patterning concept is expected to be most advantageous for devices and circuits that must operate at frequencies from about 4 to about 60 GHz. A constriction can be designed such that the magnitude of the microwave electric field and the effective width of the region occupied by the microwave electric field become functions of the applied DC

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 BaTiO 3/SrTiO 3 superlattices on SrTiO 3 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. Effectsmore » of electric boundary conditions are investigated by growing the same superlattice alternatively on SrTiO 3 substrates and 20 nm SrRuO 3 thin films on SrTiO 3 substrates. Our experiments provide important insights into the formation and evolution of ferroelectric domains when the sample is ferroelectric during the growth process.« less

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

PubMed Central

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

2015-01-01

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. PMID:26202946

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.

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.

Promising ferroelectricity in 2D group IV tellurides: a first-principles study

NASA Astrophysics Data System (ADS)

Wan, Wenhui; Liu, Chang; Xiao, Wende; Yao, Yugui

2017-09-01

Based on the first-principles calculations, we investigated the ferroelectric properties of two-dimensional (2D) Group-IV tellurides XTe (X = Si, Ge, and Sn), with a focus on GeTe. 2D Group-IV tellurides energetically prefer an orthorhombic phase with a hinge-like structure and an in-plane spontaneous polarization. The intrinsic Curie temperature Tc of monolayer GeTe is as high as 570 K and can be raised quickly by applying a tensile strain. An out-of-plane electric field can effectively decrease the coercive field for the reversal of polarization, extending its potential for regulating the polarization switching kinetics. Moreover, for bilayer GeTe, the ferroelectric phase is still the ground state. Combined with these advantages, 2D GeTe is a promising candidate material for practical integrated ferroelectric applications.

Phonon localization transition in relaxor ferroelectric PZN-5%PT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Manley, Michael E.; Christianson, Andrew D.; Abernathy, Douglas L.

Relaxor ferroelectric behavior occurs in many disordered ferroelectric materials but is not well understood at the atomic level. Recent experiments and theoretical arguments indicate that Anderson localization of phonons instigates relaxor behavior by driving the formation of polar nanoregions (PNRs). Here, we use inelastic neutron scattering to observe phonon localization in relaxor ferroelectric PZN-5%PT (0.95[Pb(Zn 1/3 Nb 2/3)O 3]–0.05PbTiO 3) and detect additional features of the localization process. In the lead, up to phonon localization on cooling, the local resonant modes that drive phonon localization increase in number. The increase in resonant scattering centers is attributed to a known increasemore » in the number of locally off centered Pb atoms on cooling. The transition to phonon localization occurs when these random scattering centers increase to a concentration where the Ioffe-Regel criterion is satisfied for localizing the phonon. Finally, we also model the effects of damped mode coupling on the observed phonons and phonon localization structure.« less

Phonon localization transition in relaxor ferroelectric PZN-5%PT

DOE PAGES

Manley, Michael E.; Christianson, Andrew D.; Abernathy, Douglas L.; ...

2017-03-27

Relaxor ferroelectric behavior occurs in many disordered ferroelectric materials but is not well understood at the atomic level. Recent experiments and theoretical arguments indicate that Anderson localization of phonons instigates relaxor behavior by driving the formation of polar nanoregions (PNRs). Here, we use inelastic neutron scattering to observe phonon localization in relaxor ferroelectric PZN-5%PT (0.95[Pb(Zn 1/3 Nb 2/3)O 3]–0.05PbTiO 3) and detect additional features of the localization process. In the lead, up to phonon localization on cooling, the local resonant modes that drive phonon localization increase in number. The increase in resonant scattering centers is attributed to a known increasemore » in the number of locally off centered Pb atoms on cooling. The transition to phonon localization occurs when these random scattering centers increase to a concentration where the Ioffe-Regel criterion is satisfied for localizing the phonon. Finally, we also model the effects of damped mode coupling on the observed phonons and phonon localization structure.« less

First-principles Studies of Ferroelectricity in BiMnO3 Thin Films

NASA Astrophysics Data System (ADS)

Wang, Yun-Peng; Cheng, Hai-Ping

The ferroelectricity in BiMnO3 thin films is a long-standing problem. We employed a first-principles density functional theory with inclusion of the local Hubbard Coulomb (U) and exchange (J) terms. The parameters U and J are optimized to reproduce the atomic structure and the energy gap of bulk C2/c BiMnO3. With these optimal U and J parameters, the calculated ferromagnetic Curie temperature and lattice dynamics properties agree with experiments. We then studied the ferroelectricity in few-layer BiMnO3 thin films on SrTiO3(001) substrates. Our calculations identified ferroelectricity in monolayer, bilayer and trilayer BiMnO3 thin films. We find that the energy barrier for 90° rotation of electric polarization is about 3 - 4 times larger than that of conventional ferroelectric materials. This work was supported by the US Department of Energy (DOE), Office of Basic Energy Sciences (BES), under Contract No. DE-FG02-02ER45995. Computations were done using the utilities of the National Energy Research Scientific Computing Center (NERSC).

Texture and anisotropy in ferroelectric lead metaniobate

NASA Astrophysics Data System (ADS)

Iverson, Benjamin John

Ferroelectric lead metaniobate, PbNb2O6, is a piezoelectric ceramic typically used because of its elevated Curie temperature and anisotropic properties. However, the piezoelectric constant, d33, is relatively low in randomly oriented ceramics when compared to other ferroelectrics. Crystallographic texturing is often employed to increase the piezoelectric constant because the spontaneous polarization axes of grains are better aligned. In this research, crystallographic textures induced through tape casting are distinguished from textures induced through electrical poling. Texture is described using multiple quantitative approaches utilizing X-ray and neutron time-of-flight diffraction. Tape casting lead metaniobate with an inclusion of acicular template particles induces an orthotropic texture distribution. Templated grain growth from seed particles oriented during casting results in anisotropic grain structures. The degree of preferred orientation is directly linked to the shear behavior of the tape cast slurry. Increases in template concentration, slurry viscosity, and casting velocity lead to larger textures by inducing more particle orientation in the tape casting plane. The maximum 010 texture distributions were two and a half multiples of a random distribution. Ferroelectric texture was induced by electrical poling. Electric poling increases the volume of material oriented with the spontaneous polarization direction in the material. Samples with an initial paraelectric texture exhibit a greater change in the domain volume fraction during electrical poling than randomly oriented ceramics. In tape cast samples, the resulting piezoelectric response is proportional to the 010 texture present prior to poling. This results in property anisotropy dependent on initial texture. Piezoelectric properties measured on the most textured ceramics were similar to those obtained with a commercial standard.

A first-principles study on second-order ferroelectric phase transition in two-dimensional puckered group V materials

NASA Astrophysics Data System (ADS)

Lee, Sang-Hoon; Jhi, Seung-Hoon

We study two-dimensional group V materials (P, As, Sb, and Bi) in puckered honeycomb structure using first-principles calculations. Two factors, the degree of puckering and buckling characterize not only the atomic structure but also the electronic structure and its topological phase. By analyzing the lone-pair character of constituent elements and the softening of the phonon mode, we clarify the origin of the buckling. We show that the phonon softening leads the second-order type structural phase transition from a flat to a buckled configuration. The inversion symmetry breaking associated with the structural transition induces the spontaneous polarization in these homogenous materials. Our calculations suggest that external strains or n-type doping are effective methods to control the degree of buckling. We find that the ferroelectric and non-trivial topological phase can coexist in puckered Bi when tensile strains are applied.

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%.

Simulation studies of nucleation of ferroelectric polarization reversal.

DOE Office of Scientific and Technical Information (OSTI.GOV)

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 LiTaO 3, 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 alsomore » 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.« less

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.

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

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.

Epitaxy of Ferroelectric P(VDF-TrFE) Films via Removable PTFE Templates and Its Application in Semiconducting/Ferroelectric Blend Resistive Memory.

PubMed

Xia, Wei; Peter, Christian; Weng, Junhui; Zhang, Jian; Kliem, Herbert; Jiang, Yulong; Zhu, Guodong

2017-04-05

Ferroelectric polymer based devices exhibit great potentials in low-cost and flexible electronics. To meet the requirements of both low voltage operation and low energy consumption, thickness of ferroelectric polymer films is usually required to be less than, for example, 100 nm. However, decrease of film thickness is also accompanied by the degradation of both crystallinity and ferroelectricity and also the increase of current leakage, which surely degrades device performance. Here we report one epitaxy method based on removable poly(tetrafluoroethylene) (PTFE) templates for high-quality fabrication of ordered ferroelectric polymer thin films. Experimental results indicate that such epitaxially grown ferroelectric polymer films exhibit well improved crystallinity, reduced current leakage and good resistance to electrical breakdown, implying their applications in high-performance and low voltage operated ferroelectric devices. On the basis of this removable PTFE template method, we fabricated organic semiconducting/ferroelectric blend resistive films which presented record electrical performance with operation voltage as low as 5 V and ON/OFF ratio up to 10 5 .

Enhancement of Local Piezoresponse in Polymer Ferroelectrics via Nanoscale Control of Microstructure

DOE PAGES

Choi, Yoon-Young; Sharma, Pankaj; Phatak, Charudatta; ...

2015-02-01

Polymer ferroelectrics are flexible and lightweight electromechanical materials that are widely studied due to their potential application as sensors, actuators, and energy harvesters. However, one of the biggest challenges is their low piezoelectric coefficient. Here, we report a mechanical annealing effect based on local pressure induced by a nanoscale tip that enhances the local piezoresponse. This process can control the nanoscale material properties over a microscale area at room temperature. We attribute this improvement to the formation and growth of beta-phase extended chain crystals via sliding diffusion and crystal alignment along the scan axis under high mechanical stress. We believemore » that this technique can be useful for local enhancement of piezoresponse in ferroelectric polymer thin films.« less

Ferroelectric domain engineering by focused infrared femtosecond pulses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Xin; Shvedov, Vladlen; Sheng, Yan, E-mail: yan.sheng@anu.edu.au

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 monitoringmore » the Čerenkov second harmonic signal, which is sensitive to the appearance of ferroelectric domain walls.« less

Nanopatterned ferroelectrics for ultrahigh density rad-hard nonvolatile memories.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brennecka, Geoffrey L.; Stevens, Jeffrey; Scrymgeour, David

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{submore » 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.« less

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.

First-principles analysis of ferroelectric transition in MnSnO3 and MnTiO3 perovskites

NASA Astrophysics Data System (ADS)

Kang, Sung Gu

2018-06-01

The ferroelectric instabilities of an artificially adopted Pnma structure in low tolerance perovskites have been explored (Kang et al., 2017) [4], where an unstable A-site environment was reported to be the major driving source for the low tolerance perovskites to exhibit ferroelectric instability. This study examined the ferroelectric transition of two magnetic perovskite materials, MnSnO3 and MnTiO3, in Pnma phase. Phase transitions to the Pnma phase at elevated pressures were observed. MnSnO3, which has a lower (larger) tolerance factor (B-site cation radius), showed a higher ferroelectric mode amplitude than MnTiO3. The distribution of the bond length of Mn-O and the mean quadratic elongation (QE) of octahedra (SnO6 or TiO6) were investigated for structural analysis. However, MnTiO3 showed a larger spontaneous polarization than MnSnO3 due to high Born effective charges of titanium. This study is useful because it provides a valuable pathway to the design of promising multiferroic materials.

Understanding the Origins of Large Negative Thermal Expansion in Ferroelectric Perovskites from First Principles

NASA Astrophysics Data System (ADS)

Ritz, Ethan; Benedek, Nicole

Many of the functional properties of ABO3 perovskite oxides (for example, ferroelectricity) are strongly linked to particular phonon modes in the material. In addition, in many cases it is possible to formulate simple guidelines or `rules of thumb' that link crystal structure and chemistry to specific lattice dynamical characteristics. The thermal transport properties of perovskites are thus potentially highly tunable and dynamically controllable with external fields. We use first-principles density functional theory to reveal new details related to the origin of the large negative thermal expansion (NTE) observed for ferroelectric PbTiO3. Although the origin of NTE in this material is often ascribed to ferroelectricity (which arises from the freezing in of a soft, zone-center optical phonon), our results suggest that zone-boundary modes play a major role in driving NTE. In addition, hybridization between different electronic states has a significant effect on the lattice dynamics of PbTiO3 in general, and its NTE behavior in particular. Our work has implications for the understanding of, discovery and design of NTE in perovskites and other families of inorganic materials. This work was supported in part by a NASA Space Technology Research Fellowship.

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.

Transformable ferroelectric control of dynamic magnetic permeability

NASA Astrophysics Data System (ADS)

Jiang, Changjun; Jia, Chenglong; Wang, Fenglong; Zhou, Cai; Xue, Desheng

2018-02-01

Magnetic permeability, which measures the response of a material to an applied magnetic field, is crucial to the performance of magnetic devices and related technologies. Its dynamic value is usually a complex number with real and imaginary parts that describe, respectively, how much magnetic power can be stored and lost in the material. Control of permeability is therefore closely related to energy redistribution within a magnetic system or energy exchange between magnetic and other degrees of freedom via certain spin-dependent interactions. To avoid a high power consumption, direct manipulation of the permeability with an electric field through magnetoelectric coupling leads to high efficiency and simple operation, but remains a big challenge in both the fundamental physics and material science. Here we report unambiguous evidence of ferroelectric control of dynamic magnetic permeability in a Co /Pb (Mg1/3Nb2/3) 0.7Ti0.3O3 (Co/PMN-PT) heterostructure, in which the ferroelectric PMN-PT acts as an energy source for the ferromagnetic Co film via an interfacial linear magnetoelectric interaction. The electric field tuning of the magnitude and line shape of the permeability offers a highly localized means of controlling magnetization with ultralow power consumption. Additionally, the emergence of negative permeability promises a new way of realizing functional nanoscale metamaterials with adjustable refraction index.

Properties of Ferroelectric Perovskite Structures under Non-equilibrium Conditions

NASA Astrophysics Data System (ADS)

Zhang, Qingteng

Ferroelectric materials have received lots of attention thanks to their intriguing properties such as the piezoelectric and pyroelectric effects, as well as the large dielectric constants and the spontaneous polarization which can potentially be used for information storage. In particular, perovskite crystal has a very simple unit cell structure yet a very rich phase transition diagram, which makes it one of the most intensively studied ferroelectric materials. In this dissertation, we use effective Hamiltonian, a first-principles-based computational technique to study the finite-temperature properties of ferroelectric perovskites. We studied temperature-graded (BaxSr 1-x)TiO3 (BST) bulk alloys as well as the dynamics of nanodomain walls (nanowalls) in Pb(Zr xTi1-x)O 3 (PZT) ultra-thin films under the driving force of an AC field. Our computations suggest that, for the temperature-graded BST, the polarization responds to the temperature gradient (TG), with the "up" and "down" offset observed in polarization components along the direction of TG, in agreement with the findings from experiments. For the nanowalls in PZT, the dynamics can be described by the damped-harmonic-oscillator model, and we observed a size-driven transition from resonance to relaxational dynamics at a critical thickness of 7.2 nm. The transition originates from the change in the effective mass of a nanowall as a film thickness increases. Some of the findings may find potential applications in various devices, such as thermal sensors, energy converters, or novel memory units.

Prospects and applications near ferroelectric quantum phase transitions: a key issues review.

PubMed

Chandra, P; Lonzarich, G G; Rowley, S E; Scott, J F

2017-11-01

The emergence of complex and fascinating states of quantum matter in the neighborhood of zero temperature phase transitions suggests that such quantum phenomena should be studied in a variety of settings. Advanced technologies of the future may be fabricated from materials where the cooperative behavior of charge, spin and current can be manipulated at cryogenic temperatures. The progagating lattice dynamics of displacive ferroelectrics make them appealing for the study of quantum critical phenomena that is characterized by both space- and time-dependent quantities. In this key issues article we aim to provide a self-contained overview of ferroelectrics near quantum phase transitions. Unlike most magnetic cases, the ferroelectric quantum critical point can be tuned experimentally to reside at, above or below its upper critical dimension; this feature allows for detailed interplay between experiment and theory using both scaling and self-consistent field models. Empirically the sensitivity of the ferroelectric T c 's to external and to chemical pressure gives practical access to a broad range of temperature behavior over several hundreds of Kelvin. Additional degrees of freedom like charge and spin can be added and characterized systematically. Satellite memories, electrocaloric cooling and low-loss phased-array radar are among possible applications of low-temperature ferroelectrics. We end with open questions for future research that include textured polarization states and unusual forms of superconductivity that remain to be understood theoretically.

Prospects and applications near ferroelectric quantum phase transitions: a key issues review

NASA Astrophysics Data System (ADS)

Chandra, P.; Lonzarich, G. G.; Rowley, S. E.; Scott, J. F.

2017-11-01

The emergence of complex and fascinating states of quantum matter in the neighborhood of zero temperature phase transitions suggests that such quantum phenomena should be studied in a variety of settings. Advanced technologies of the future may be fabricated from materials where the cooperative behavior of charge, spin and current can be manipulated at cryogenic temperatures. The progagating lattice dynamics of displacive ferroelectrics make them appealing for the study of quantum critical phenomena that is characterized by both space- and time-dependent quantities. In this key issues article we aim to provide a self-contained overview of ferroelectrics near quantum phase transitions. Unlike most magnetic cases, the ferroelectric quantum critical point can be tuned experimentally to reside at, above or below its upper critical dimension; this feature allows for detailed interplay between experiment and theory using both scaling and self-consistent field models. Empirically the sensitivity of the ferroelectric T c’s to external and to chemical pressure gives practical access to a broad range of temperature behavior over several hundreds of Kelvin. Additional degrees of freedom like charge and spin can be added and characterized systematically. Satellite memories, electrocaloric cooling and low-loss phased-array radar are among possible applications of low-temperature ferroelectrics. We end with open questions for future research that include textured polarization states and unusual forms of superconductivity that remain to be understood theoretically.

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).

Ferroelectric devices using lead zirconate titanate (PZT) nanoparticles.

PubMed

Paik, Young Hun; Kojori, Hossein Shokri; Kim, Sung Jin

2016-02-19

We successfully demonstrate the synthesis of lead zirconate titanate nanoparticles (PZT NPs) and a ferroelectric device using the synthesized PZT NPs. The crystalline structure and the size of the nanocrystals are studied using x-ray diffraction and transmission electron microscopy, respectively. We observe <100 nm of PZT NPs and this result matches dynamic light scattering measurements. A solution-based low-temperature process is used to fabricate PZT NP-based devices on an indium tin oxide substrate. The fabricated ferroelectric devices are characterized using various optical and electrical measurements and we verify ferroelectric properties including ferroelectric hysteresis and the ferroelectric photovoltaic effect. Our approach enables low-temperature solution-based processes that could be used for various applications. To the best of our knowledge, this low-temperature solution processed ferroelectric device using PZT NPs is the first successful demonstration of its kind.

Ferroelectric devices using lead zirconate titanate (PZT) nanoparticles

NASA Astrophysics Data System (ADS)

Paik, Young Hun; Shokri Kojori, Hossein; Kim, Sung Jin

2016-02-01

We successfully demonstrate the synthesis of lead zirconate titanate nanoparticles (PZT NPs) and a ferroelectric device using the synthesized PZT NPs. The crystalline structure and the size of the nanocrystals are studied using x-ray diffraction and transmission electron microscopy, respectively. We observe <100 nm of PZT NPs and this result matches dynamic light scattering measurements. A solution-based low-temperature process is used to fabricate PZT NP-based devices on an indium tin oxide substrate. The fabricated ferroelectric devices are characterized using various optical and electrical measurements and we verify ferroelectric properties including ferroelectric hysteresis and the ferroelectric photovoltaic effect. Our approach enables low-temperature solution-based processes that could be used for various applications. To the best of our knowledge, this low-temperature solution processed ferroelectric device using PZT NPs is the first successful demonstration of its kind.

Ferroelectric thin-film active sensors for structural health monitoring

NASA Astrophysics Data System (ADS)

Lin, Bin; Giurgiutiu, Victor; Yuan, Zheng; Liu, Jian; Chen, Chonglin; Jiang, Jiechao; Bhalla, Amar S.; Guo, Ruyan

2007-04-01

Piezoelectric wafer active sensors (PWAS) have been proven a valuable tool in structural health monitoring. Piezoelectric wafer active sensors are able to send and receive guided Lamb/Rayleigh waves that scan the structure and detect the presence of incipient cracks and structural damage. In-situ thin-film active sensor deposition can eliminate the bonding layer to improve the durability issue and reduce the acoustic impedance mismatch. Ferroelectric thin films have been shown to have piezoelectric properties that are close to those of single-crystal ferroelectrics but the fabrication of ferroelectric thin films on structural materials (steel, aluminum, titanium, etc.) has not been yet attempted. In this work, in-situ fabrication method of piezoelectric thin-film active sensors arrays was developed using the nano technology approach. Specification for the piezoelectric thin-film active sensors arrays was based on electro-mechanical-acoustical model. Ferroelectric BaTiO3 (BTO) thin films were successfully deposited on Ni tapes by pulsed laser deposition under the optimal synthesis conditions. Microstructural studies by X-ray diffractometer and transmission electron microscopy reveal that the as-grown BTO thin films have the nanopillar structures with an average size of approximately 80 nm in diameter and the good interface structures with no inter-diffusion or reaction. The dielectric and ferroelectric property measurements exhibit that the BTO films have a relatively large dielectric constant, a small dielectric loss, and an extremely large piezoelectric response with a symmetric hysteresis loop. The research objective is to develop the fabrication and optimum design of thin-film active sensor arrays for structural health monitoring applications. The short wavelengths of the micro phased arrays will permit the phased-array imaging of smaller parts and smaller damage than is currently not possible with existing technology.

Giant electromechanical coupling of relaxor ferroelectrics controlled by polar nanoregion vibrations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Manley, Michael E.; Abernathy, Douglas L.; Sahul, Raffi

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(Mg 1/3Nb 2/3)O 3] xPbTiO 3} (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

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

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(Mg 1/3Nb 2/3)O 3] xPbTiO 3} (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

Giant lateral electrostriction in ferroelectric liquid-crystalline elastomers

NASA Astrophysics Data System (ADS)

Lehmann, W.; Skupin, H.; Tolksdorf, C.; Gebhard, E.; Zentel, R.; Krüger, P.; Lösche, M.; Kremer, F.

2001-03-01

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 150MVm-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 100nanometres) ferroelectric liquid-crystalline elastomer films that exhibit 4 per cent strain at only 1.5 MVm-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.

Atomic Layer Engineering of High-κ Ferroelectricity in 2D Perovskites.

PubMed

Li, Bao-Wen; Osada, Minoru; Kim, Yoon-Hyun; Ebina, Yasuo; Akatsuka, Kosho; Sasaki, Takayoshi

2017-08-09

Complex perovskite oxides offer tremendous potential for controlling their rich variety of electronic properties, including high-T C superconductivity, high-κ ferroelectricity, and quantum magnetism. Atomic-scale control of these intriguing properties in ultrathin perovskites is an important challenge for exploring new physics and device functionality at atomic dimensions. Here, we demonstrate atomic-scale engineering of dielectric responses using two-dimensional (2D) homologous perovskite nanosheets (Ca 2 Na m-3 Nb m O 3m+1 ; m = 3-6). In this homologous 2D material, the thickness of the perovskite layers can be incrementally controlled by changing m, and such atomic layer engineering enhances the high-κ dielectric response and local ferroelectric instability. The end member (m = 6) attains a high dielectric constant of ∼470, which is the highest among all known dielectrics in the ultrathin region (<10 nm). These results provide a new strategy for achieving high-κ ferroelectrics for use in ultrascaled high-density capacitors and post-graphene technology.

Self-Assembly of Organic Ferroelectrics by Evaporative Dewetting: A Case of β-Glycine.

PubMed

Seyedhosseini, Ensieh; Romanyuk, Konstantin; Vasileva, Daria; Vasilev, Semen; Nuraeva, Alla; Zelenovskiy, Pavel; Ivanov, Maxim; Morozovska, Anna N; Shur, Vladimir Ya; Lu, Haidong; Gruverman, Alexei; Kholkin, Andrei L

2017-06-14

Self-assembly of ferroelectric materials attracts significant interest because it offers a promising fabrication route to novel structures useful for microelectronic devices such as nonvolatile memories, integrated sensors/actuators, or energy harvesters. In this work, we demonstrate a novel approach for self-assembly of organic ferroelectrics (as exemplified by ferroelectric β-glycine) using evaporative dewetting, which allows forming quasi-regular arrays of nano- and microislands with preferred orientation of polarization axes. Surprisingly, self-assembled islands are crystallographically oriented in a radial direction from the center of organic "grains" formed during dewetting process. The kinetics of dewetting process follows the t -1/2 law, which is responsible for the observed polygon shape of the grain boundaries and island coverage as a function of radial position. The polarization in ferroelectric islands of β-glycine is parallel to the substrate and switchable under a relatively small dc voltage applied by the conducting tip of piezoresponse force microscope. Significant size effect on polarization is observed and explained within the Landau-Ginzburg-Devonshire phenomenological formalism.

Superdomain dynamics in ferroelectric-ferroelastic films: Switching, jamming, and relaxation

NASA Astrophysics Data System (ADS)

Scott, J. F.; Hershkovitz, A.; Ivry, Y.; Lu, H.; Gruverman, A.; Gregg, J. M.

2017-12-01

Recent experimental work shows that ferroelectric switching can occur in large jumps in which ferroelastic superdomains switch together, rather than having the numerous smaller ferroelectric domains switch within them. In this sense, the superdomains play a role analogous to that of Abrikosov vortices in thin superconducting films under the Kosterlitz-Thouless framework, which control the dynamics more than individual Cooper pairs within them do. Here, we examine the dynamics of ferroelastic superdomains in ferroelastic ferroelectrics and their role in switching devices such as memories. Jamming of ferroelectric domains in thin films has revealed an unexpected time dependence of t-1/4 at long times (hours), but it is difficult to discriminate between power-law and exponential relaxation. Other aspects of this work, including spatial period doubling of domains, led to a description of ferroelastic domains as nonlinear processes in a viscoelastic medium, which produce folding and metastable kinetically limited states. This ¼ exponent is a surprising agreement with the well-known value of ¼ for coarsening dynamics in viscoelastic media. We try to establish a link between these two processes, hitherto considered unrelated, and with superdomains and domain bundles. We note also that high-Tc superconductors share many of the ferroelastic domain properties discussed here and that several new solar cell materials and metal-insulator transition systems are ferroelastic.

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.

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.

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

Local and Average Structures in Ferroelectrics under Perturbing Fields

NASA Astrophysics Data System (ADS)

Usher, Tedi-Marie

Ferroelectric and dielectric ceramics are used in a multitude of applications including sonar, micro-positioning, actuators, transducers, and capacitors. The most widely used compositions are lead (Pb)-based, however there is an ongoing effort to reduce lead-based materials in consumer applications. Many lead-free compositions are under investigation; some are already in production and others have been identified as suitable for certain applications. For any such material system, there is a need to thoroughly characterize the structure in order to develop robust structure-property relationships, particularly during in situ application of different stimuli (e.g. electric field and mechanical stress). This work investigates two lead-free material systems of interest, (1-x)Na1/2Bi1/2TiO3 - (x)BaTiO3 (NBT-xBT) and (1-x)BaTiO3 - (x)Bi(Zn1/2Ti1/2)O3 (BT-xBZT), as well as the constituent compounds Na1/2Bi1/2TiO3 and BaTiO3. Both systems exhibit compositional boundaries between unique phases exhibiting different functional properties. Advanced scattering techniques are used to characterize the atomic structures and how they change during in situ application of different stimuli. The long-range, average structures are probed using high-resolution X-ray diffraction (HRXRD) and neutron diffraction (ND) and local scale structures are probed using X-ray or neutron total scattering, which are converted to pair distribution functions (PDFs). First, two in situ ND experiments which investigate structural changes to NBT-xBT in response to uniaxial stresses and electric fields are presented. In response to stresses, different crystallographic directions strain differently. The elastic anisotropy, (i.e., the orientation-dependence of elastic stiffness) for the studied compositions is characterized. A general inverse relationship between elastic anisotropy and piezoelectric anisotropy is demonstrated for three common ferroelectric point groups. In response to electric fields

Scalable ferroelectric MOS capacitors comprised of single crystalline SrZrxTi1-xO3 on Ge.

NASA Astrophysics Data System (ADS)

Moghadam, Reza; Xiao, Z.-Y.; Ahmadi-Majlan, K.; Grimley, E.; Ong, P. V.; Lebeau, J. M.; Chambers, S. A.; Hong, X.; Sushko, P.; Ngai, J. H.

The epitaxial growth of multifunctional oxides on semiconductors has opened a pathway to introduce new functionalities to semiconductor device technologies. In particular, ferroelectric materials integrated on semiconductors could lead to field-effect devices that require very little power to operate, or that possess both logic and memory functionalities. The development of metal-oxide-semiconductor (MOS) capacitors in which the polarization of a ferroelectric gate is coupled to the surface potential of a semiconducting channel is essential in order to realize such field-effect devices. Here we demonstrate that scalable, ferroelectric MOS capacitors can be realized using single crystalline SrZrxTi1-xO3 (x = 0.7) that has been epitaxially grown on Ge. Single crystalline SrZrxTi1-xO3 exhibits characteristics that are ideal for a ferroelectric gate material, namely, a type-I band offset with respect to Ge, large coercive fields and polarization that can be enhanced with electric field. The latter characteristic stems from the relaxor nature of SrZrxTi1-xO3. These properties enable MOS capacitors with 5 nm thick SrZrxTi1-xO3 layers to exhibit a nearly 2 V wide hysteretic window in the capacitance-voltage characteristics. The realization of ferroelectric MOS capacitors with technologically relevant gate thicknesses opens the pathway to practical field effect devices. NSF DMR 1508530.

Development of highly-ordered, ferroelectric inverse opal films using sol gel infiltration

NASA Astrophysics Data System (ADS)

Matsuura, N.; Yang, S.; Sun, P.; Ruda, H. E.

2005-07-01

Highly-ordered, ferroelectric, Pb-doped Ba0.7Sr0.3TiO3, inverse opal films were fabricated by spin-coating a sol gel precursor into a polystyrene artificial opal template followed by heat treatment. Thin films of the ferroelectric were independently studied and were shown to exhibit good dielectric properties and high refractive indices. The excellent quality of the final inverse opal film using this spin-coating infiltration method was confirmed by scanning electron microscopy images and the good correspondence between optical reflection data and theoretical simulations. Using this method, the structural and material parameters of the final ferroelectric inverse opal film were easily adjusted by template heating and through repeated infiltrations, without changes in the initial template or precursor. Also, crack-free inverse opal thin films were fabricated over areas comparable to that of the initial crack-free polystyrene template (˜100 by 100 μm2).

Structural contribution to the ferroelectric fatigue in lead zirconate titanate ceramics

NASA Astrophysics Data System (ADS)

Hinterstein, M.; Rouquette, J.; Haines, J.; Papet, Ph.; Glaum, J.; Knapp, M.; Eckert, J.; Hoffman, M.

2014-09-01

Many ferroelectric devices are based on doped lead zirconate titanate (PZT) ceramics with compositions near the morphotropic phase boundary (MPB), at which the relevant material's properties approach their maximum. Based on a synchrotron x-ray diffraction study of MPB PZT, bulk fatigue is unambiguously found to arise from a less effective field induced tetragonal-to-monoclinic transformation, at which the degradation of the polarization flipping is detected by a less intense and more diffuse anomaly in the atomic displacement parameter of lead. The time dependence of the ferroelectric response on a structural level down to 250 μs confirms this interpretation in the time scale of the piezolectric strain response.

Enhancing interfacial magnetization with a ferroelectric

DOE Office of Scientific and Technical Information (OSTI.GOV)

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

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 [PbZr 0.2Ti 0.8O 3/La 0.8Sr 0.2MnO 3(PZT/LSMO)] heterostructures. We find that the magnetization at the surfaces and interfaces of our LSMO films without PZT are always deterioratedmore » 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 4.0μ B/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

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 [PbZr 0.2Ti 0.8O 3/La 0.8Sr 0.2MnO 3(PZT/LSMO)] heterostructures. We find that the magnetization at the surfaces and interfaces of our LSMO films without PZT are always deterioratedmore » 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 4.0μ B/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

A scaling law for distinct electrocaloric cooling performance in low-dimensional organic, relaxor and anti-ferroelectrics.

PubMed

Shi, Yuping; Huang, Limin; Soh, Ai Kah; Weng, George J; Liu, Shuangyi; Redfern, Simon A T

2017-09-11

Electrocaloric (EC) materials show promise in eco-friendly solid-state refrigeration and integrable on-chip thermal management. While direct measurement of EC thin-films still remains challenging, a generic theoretical framework for quantifying the cooling properties of rich EC materials including normal-, relaxor-, organic- and anti-ferroelectrics is imperative for exploiting new flexible and room-temperature cooling alternatives. Here, we present a versatile theory that combines Master equation with Maxwell relations and analytically relates the macroscopic cooling responses in EC materials with the intrinsic diffuseness of phase transitions and correlation characteristics. Under increased electric fields, both EC entropy and adiabatic temperature changes increase quadratically initially, followed by further linear growth and eventual gradual saturation. The upper bound of entropy change (∆S max ) is limited by distinct correlation volumes (V cr ) and transition diffuseness. The linearity between V cr and the transition diffuseness is emphasized, while ∆S max  = 300 kJ/(K.m 3 ) is obtained for Pb 0.8 Ba 0.2 ZrO 3 . The ∆S max in antiferroelectric Pb 0.95 Zr 0.05 TiO 3 , Pb 0.8 Ba 0.2 ZrO 3 and polymeric ferroelectrics scales proportionally with V cr -2.2 , owing to the one-dimensional structural constraint on lattice-scale depolarization dynamics; whereas ∆S max in relaxor and normal ferroelectrics scales as ∆S max ~ V cr -0.37 , which tallies with a dipolar interaction exponent of 2/3 in EC materials and the well-proven fractional dimensionality of 2.5 for ferroelectric domain walls.

Nano-embossing technology on ferroelectric thin film Pb(Zr0.3,Ti0.7)O3 for multi-bit storage application

PubMed Central

2011-01-01

In this work, we apply nano-embossing technique to form a stagger structure in ferroelectric lead zirconate titanate [Pb(Zr0.3, Ti0.7)O3 (PZT)] films and investigate the ferroelectric and electrical characterizations of the embossed and un-embossed regions, respectively, of the same films by using piezoresponse force microscopy (PFM) and Radiant Technologies Precision Material Analyzer. Attributed to the different layer thickness of the patterned ferroelectric thin film, two distinctive coercive voltages have been obtained, thereby, allowing for a single ferroelectric memory cell to contain more than one bit of data. PMID:21794156

Ferroelectric ceramics in a pyroelectric accelerator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shchagin, A. V., E-mail: shchagin@kipt.kharkov.ua; Belgorod State University, Belgorod 308015; Miroshnik, V. S.

2015-12-07

The applicability of polarized ferroelectric ceramics as a pyroelectric in a pyroelectric accelerator is shown by experiments. The spectra of X-ray radiation of energy up to tens of keV, generated by accelerated electrons, have been measured on heating and cooling of the ceramics in vacuum. It is suggested that curved layers of polarized ferroelectric ceramics be used as elements of ceramic pyroelectric accelerators. Besides, nanotubes and nanowires manufactured from ferroelectric ceramics are proposed for the use in nanometer-scale ceramic pyroelectric nanoaccelerators for future applications in nanotechnologies.

Carrier Density Modulation in Ge Heterostructure by Ferroelectric Switching

DOE PAGES

Ponath, Patrick; Fredrickson, Kurt; Posadas, Agham B.; ...

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-lossmore » 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.« less

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.

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.

Binary Compound Bilayer and Multilayer with Vertical Polarizations: Two-Dimensional Ferroelectrics, Multiferroics, and Nanogenerators.

PubMed

Li, Lei; Wu, Menghao

2017-06-27

Vertical ferroelectricity in two-dimensional (2D) materials is desirable for high-density data storage without quantum tunneling or high power consumption/dissipation, which still remains elusive due to the surface-depolarizing field. Herein, we report the first-principles evidence of 2D vertical ferroelectricity induced by interlayer translation, which exists extensively in the graphitic bilayer of BN, AlN, ZnO, MoS 2 , GaSe, etc.; the bilayer of some 2D ferromagnets like MXene, VS 2 , and MoN 2 can be even multiferroics with switchable magnetizations upon ferroelectric switching, rendering efficient reading and writing for high-density data storage. In particular, the electromechanical coupling between interlayer translation and potential can be used to drive the flow of electrons as nanogenerators for harvesting energy from human activities, ocean waves, mechanical vibration, etc. A ferroelectric superlattice with spatial varying potential can be formed in a bilayer Moire pattern upon a small twist or strain, making it possible to generate periodic n/p doped-domains and shape the periodicity of the potential energy landscape. Finally, some of their multilayer counterparts with wurtzite structures like a ZnO multilayer are revealed to exhibit another type of vertical ferroelectricity with greatly enhanced polarizations.

Ferroelectric FET for nonvolatile memory application with two-dimensional MoSe2 channels

NASA Astrophysics Data System (ADS)

Wang, Xudong; Liu, Chunsen; Chen, Yan; Wu, Guangjian; Yan, Xiao; Huang, Hai; Wang, Peng; Tian, Bobo; Hong, Zhenchen; Wang, Yutao; Sun, Shuo; Shen, Hong; Lin, Tie; Hu, Weida; Tang, Minghua; Zhou, Peng; Wang, Jianlu; Sun, Jinglan; Meng, Xiangjian; Chu, Junhao; Li, Zheng

2017-06-01

Graphene and other two-dimensional materials have received considerable attention regarding their potential applications in nano-electronics. Here, we report top-gate nonvolatile memory field-effect transistors (FETs) with different layers of MoSe2 nanosheets channel gated by ferroelectric film. The conventional gate dielectric of FETs was replaced by a ferroelectric thin film that provides a ferroelectric polarization electric field, and therefore defined as an Fe-FET where the poly (vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) was used as the gate dielectric. Among the devices with MoSe2 channels of different thicknesses, the device with a single layer of MoSe2 exhibited a large hysteresis of electronic transport with an over 105 write/erase ratio, and displayed excellent retention and endurance performance. The possible mechanism of the device’s good properties was qualitatively analyzed using band theory. Additionally, a comprehensive study comparing the memory properties of MoSe2 channels of different thicknesses is presented. Increasing the numbers of MoSe2 layers was found to cause a reduced memory window. However, MoSe2 thickness of 5 nm yielded a write/erase ratio of more than 103. The results indicate that, based on a Fe-FET structure, the combination of two-dimensional semiconductors and organic ferroelectric gate dielectrics shows good promise for future applications in nonvolatile ferroelectric memory.

Solution-Processed Flexible Organic Ferroelectric Phototransistor.

PubMed

Zhao, Qiang; Wang, Hanlin; Jiang, Lang; Zhen, Yonggang; Dong, Huanli; Hu, Wenping

2017-12-20

In this article, we demonstrate ferroelectric insulator, P(VDF-TrFE), can be integrated with red light sensitive polymeric semiconductor, P(DPP-TzBT), toward ferroelectric organic phototransistors (OPTs). This ferroelectricity-modulated phototransistor possesses different nonvolatile and tunable dark current states due to P(VDF-TrFE)'s remnant polarization. As a result, the OPT is endowed with a tunable dark current level ranging from 1 nA to 100 nA. Once the OPT is programmed or electrically polarized, its photo-to-dark (signal-to-noise) ratio can be "flexible" during photodetection process, without gate bias application. This kind of organic ferroelectric phototransistor has great potential in detecting wide ranges of light signals with good linearity. Moreover, its tuning mechanism discussed in this work can be helpful to understand the operation mechanism of organic phototransistor (OPT). It can be promising for novel photodetection application in plastic electronic devices.

Electrical and ferroelectric properties of RF sputtered PZT/SBN on silicon for non-volatile memory applications

NASA Astrophysics Data System (ADS)

Singh, Prashant; Jha, Rajesh Kumar; Singh, Rajat Kumar; Singh, B. R.

2018-02-01

We report the integration of multilayer ferroelectric film deposited by RF magnetron sputtering and explore the electrical characteristics for its application as the gate of ferroelectric field effect transistor for non-volatile memories. PZT (Pb[Zr0.35Ti0.65]O3) and SBN (SrBi2Nb2O9) ferroelectric materials were selected for the stack fabrication due to their large polarization and fatigue free properties respectively. Electrical characterization has been carried out to obtain memory window, leakage current density, PUND and endurance characteristics. Fabricated multilayer ferroelectric film capacitor structure shows large memory window of 17.73 V and leakage current density of the order 10-6 A cm-2 for the voltage sweep of -30 to +30 V. This multilayer gate stack of PZT/SBN shows promising endurance property with no degradation in the remnant polarization for the read/write iteration cycles upto 108.

Voltage Drop in a Ferroelectric Single Layer Capacitor by Retarded Domain Nucleation.

PubMed

Kim, Yu Jin; Park, Hyeon Woo; Hyun, Seung Dam; Kim, Han Joon; Kim, Keum Do; Lee, Young Hwan; Moon, Taehwan; Lee, Yong Bin; Park, Min Hyuk; Hwang, Cheol Seong

2017-12-13

Ferroelectric (FE) capacitor is a critical electric component in microelectronic devices. Among many of its intriguing properties, the recent finding of voltage drop (V-drop) across the FE capacitor while the positive charges flow in is especially eye-catching. This finding was claimed to be direct evidence that the FE capacitor is in negative capacitance (NC) state, which must be useful for (infinitely) high capacitance and ultralow voltage operation of field-effect transistors. Nonetheless, the NC state corresponds to the maximum energy state of the FE material, so it has been widely accepted in the community that the material alleviates that state by forming ferroelectric domains. This work reports a similar V-drop effect from the 150 nm thick epitaxial BaTiO 3 ferroelectric thin film, but the interpretation was completely disparate; the V-drop can be precisely simulated by the reverse domain nucleation and propagation of which charge effect cannot be fully compensated for by the supplied charge from the external charge source. The disappearance of the V-drop effect was also observed by repeated FE switching only up to 10 cycles, which can hardly be explained by the involvement of the NC effect. The retained reverse domain nuclei even after the subsequent poling can explain such behavior.

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.

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

An Intrinsically Switchable Ladder-Type Ferroelectric BST-on-Si Composite FBAR Filter.

PubMed

Lee, Seungku; Mortazawi, Amir

2016-03-01

This paper presents a ladder-type bulk acoustic wave (BAW) intrinsically switchable filter based on ferroelectric thin-film bulk acoustic resonators (FBARs). The switchable filter can be turned on and off by the application of an external bias voltage due to the electrostrictive effect in thin-film ferroelectrics. In this paper, Barium Strontium Titanate (BST) is used as the ferroelectric material. A systematic design approach for switchable ladder-type ferroelectric filters is provided based on required filter specifications. A switchable filter is implemented in the form of a BST-on-Si composite structure to control the effective electromechanical coupling coefficient of FBARs. As an experimental verification, a 2.5-stage intrinsically switchable BST-on-Si composite FBAR filter is designed, fabricated, and measured. Measurement results for a typical BST-on-Si composite FBAR show a resonator mechanical quality factor (Q(m)) of 971, as well as a (Q(m)) × f of 2423 GHz. The filter presented here provides a measured insertion loss of 7.8 dB, out-of-band rejection of 26 dB, and fractional bandwidth of 0.33% at 2.5827 GHz when the filter is in the on state at a dc bias of 40 V. In its off state, the filter exhibits an isolation of 31 dB.

The Role of Partial Surface Charge Compensation in the Properties of Ferroelectric and Antiferroelectric Thin Films

NASA Astrophysics Data System (ADS)

Swedberg, Elena

to investigate the electrocaloric effect in ferroelectric films with partial surface charge compensation led to the prediction that the residual depolarizing field can perform a dual role in the electrocaloric effect in these films. When the depolarizing field creates competition between the monodomain and nanodomain states, we predict an enhancement of the electrocaloric effect due to the frustration that increases the entropy of the state and therefore the electrocaloric temperature change. On the other hand, when the depolarizing field leads to a formation of nanodomains, thin films either exhibit a small electrocaloric effect or lose their electrocaloric properties altogether to the irreversible nanodomain motion. When the residual depolarizing field is weak enough to permit the formation of monodomain phases, the electrocaloric effect is significantly reduced as compared to bulk. We believe that our findings could potentially reveal additional opportunities to optimize solid state cooling technology. While the electrocaloric effect has been a popular topic of interest in recent years [12], there still exists numerous gaps in the fundamental understanding of the effect. In particular, it is presently unknown whether the scaling laws, known to exist for magnetocaloric materials, can be applied to ferroelectric and antiferroelectric electrocalorics. We predict the existence of scaling laws for low-field electrocaloric temperature change in antiferroelectric and ferroelectric materials. With the help of first-principles-based simulations, we showed computationally that the scaling laws exist for antiferroelectric PbZrO3 along with ferroelectrics PbTiO3, BaTiO 3 and KNbO3. Additional evidence of the scaling laws existence are provided using experimental data from the literature. Interestingly, our studies on ferroelectric films predicted the existence of antiferroelectric behavior in ultrathin films with partial surface charge compensation. One may wonder whether it

Pseudocapacitive Sodium Storage by Ferroelectric Sn2 P2 S6 with Layered Nanostructure.

PubMed

Huang, Sheng; Meng, Chao; Xiao, Min; Ren, Shan; Wang, Shuanjin; Han, Dongmei; Li, Yuning; Meng, Yuezhong

2018-04-19

Sodium ion batteries (SIB) are considered promising alternative candidates for lithium ion batteries (LIB) because of the wide availability and low cost of sodium, therefore the development of alternative sodium storage materials with comparable performance to LIB is urgently desired. The sodium ions with larger sizes resist intercalation or alloying because of slow reaction kinetics. Most pseudocapacitive sodium storage materials are based on subtle nanomaterial engineering, which is difficult for large-scale production. Here, ferroelectric Sn 2 P 2 S 6 with layered nanostructure is developed as sodium ion storage material. The ferroelectricity-enhanced pseudocapacitance of sodium ion in the interlayer spacing makes the electrochemical reaction easier and faster, endowing the Sn 2 P 2 S 6 electrode with excellent rate capability and cycle stability. Furthermore, the facile solid state reaction synthesis and common electrode fabrication make the Sn 2 P 2 S 6 that becomes a promising anode material of SIB. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Microwave a.c. conductivity of domain walls in ferroelectric thin films

DOE PAGES

Tselev, Alexander; Yu, Pu; Cao, Ye; ...

2016-05-31

Ferroelectric domain walls are of great interest as elementary building blocks for future electronic devices due to their intrinsic few-nanometre width, multifunctional properties and field-controlled topology. To realize the electronic functions, domain walls are required to be electrically conducting and addressable non-destructively. However, these properties have been elusive because conducting walls have to be electrically charged, which makes them unstable and uncommon in ferroelectric materials. Here we reveal that spontaneous and recorded domain walls in thin films of lead zirconate and bismuth ferrite exhibit large conductance at microwave frequencies despite being insulating at d.c. We explain this effect by morphologicalmore » roughening of the walls and local charges induced by disorder with the overall charge neutrality. a.c. conduction is immune to large contact resistance enabling completely non-destructive walls read-out. Finally, this demonstrates a technological potential for harnessing a.c. conduction for oxide electronics and other materials with poor d.c. conduction, particularly at the nanoscale.« less

Microwave a.c. conductivity of domain walls in ferroelectric thin films

PubMed Central

Tselev, Alexander; Yu, Pu; Cao, Ye; Dedon, Liv R.; Martin, Lane W.; Kalinin, Sergei V.; Maksymovych, Petro

2016-01-01

Ferroelectric domain walls are of great interest as elementary building blocks for future electronic devices due to their intrinsic few-nanometre width, multifunctional properties and field-controlled topology. To realize the electronic functions, domain walls are required to be electrically conducting and addressable non-destructively. However, these properties have been elusive because conducting walls have to be electrically charged, which makes them unstable and uncommon in ferroelectric materials. Here we reveal that spontaneous and recorded domain walls in thin films of lead zirconate and bismuth ferrite exhibit large conductance at microwave frequencies despite being insulating at d.c. We explain this effect by morphological roughening of the walls and local charges induced by disorder with the overall charge neutrality. a.c. conduction is immune to large contact resistance enabling completely non-destructive walls read-out. This demonstrates a technological potential for harnessing a.c. conduction for oxide electronics and other materials with poor d.c. conduction, particularly at the nanoscale. PMID:27240997

Electron emission and beam generation using ferroelectric cathodes

NASA Astrophysics Data System (ADS)

Flechtner, Donald D.

1999-06-01

In 1989, researchers at CERN published the discovery of significant electron emission (1-100 A/cm2) from Lead-Lanthanum-Zirconate- Titanate (PLZT). The publication of these results led to international interest in ferroelectric cathodes studies for use in pulsed power devices. At Cornell University in 1991, experiments with Lead-Zirconate-Titanate (PZT) compositions were begun to study the feasibility of using this ferroelectric material as a cathode in the electron gun section of High Power Traveling Wave Tube Amplifier Experiments. Current-voltage characteristics were documented for diode voltages ranging from 50-500,000 V with anode cathode gaps of.5-6 cm. A linear current-voltage relation was found for voltages less than 50 kV. For diode voltages >=200 kV, a typical Child-Langmuir V3/2 dependence was observed. Additional experiments have demonstrated repetition rates of up to 50 Hz with current densities of >=20 A/cm2. These results have been used in the ongoing design and construction of the electron gun for a 500 kV pulse modulator capable of repetitive operation at 1 Hz. The electron gun uses a PZT 55/45 (Pb(Zr.55,Ti.45 )O3) cathode to produce a <=400 A electron beam focused by a converging magnetic field. Studies of the emission process itself indicate the initial electrons are produced by field emission from the metallic grid applied to the front surface of the cathode. The field emission is induced by the application of a fast rising 1-3 kV, 150 ns pulse to the rear electrode of the 1 mm thick ferroelectric. Field emission can lead to explosive emission from microprotrusions and metal-ferroelectric-vacuum triple points forming a diffuse plasma on the surface of the sample. Under long pulse experiments (1-5 μs), plasma velocities of ~2 cm/μs were measured from gap closure rates. Results from an ion Faraday cup experiment showed ion velocities of 1-2 cm/μs. Experimental evidence indicates the electron emission is dependent on the field emission initiated

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

Photovoltaic Enhancement with Ferroelectric HfO2Embedded in the Structure of Solar Cells

NASA Astrophysics Data System (ADS)

Eskandari, Rahmatollah; Malkinski, Leszek

Enhancing total efficiency of the solar cells is focused on the improving one or all of the three main stages of the photovoltaic effect: absorption of the light, generation of the carriers and finally separation of the carriers. Ferroelectric photovoltaic designs target the last stage with large electric forces from polarized ferroelectric films that can be larger than band gap of the material and the built-in electric fields in semiconductor bipolar junctions. In this project we have fabricated very thin ferroelectric HfO2 films ( 10nm) doped with silicon using RF sputtering method. Doped HfO2 films were capped between two TiN layers ( 20nm) and annealed at temperatures of 800ºC and 1000ºC and Si content was varied between 6-10 mol. % using different size of mounted Si chip on hafnium target. Piezoforce microscopy (PFM) method proved clear ferroelectric properties in samples with 6 mol. % of Si that were annealed at 800ºC. Ferroelectric samples were poled in opposite directions and embedded in the structure of a cell and an enhancement in photovoltaic properties were observed on the poled samples vs unpoled ones with KPFM and I-V measurements. The current work is funded by the NSF EPSCoR LA-SiGMA project under award #EPS-1003897.

Light-Induced Capacitance Tunability in Ferroelectric Crystals.

PubMed

Páez-Margarit, David; Rubio-Marcos, Fernando; Ochoa, Diego A; Del Campo, Adolfo; Fernández, José F; García, José E

2018-06-25

The remote controlling of ferroic properties with light is nowadays a hot and highly appealing topic in materials science. Here, we shed light on some of the unresolved issues surrounding light-matter coupling in ferroelectrics. Our findings show that the capacitance and, consequently, its related intrinsic material property, i.e., the dielectric constant, can be reversibly adjusted through the light power control. High photodielectric performance is exhibited across a wide range of the visible light wavelength because of the wavelength-independence of the phenomenon. We have verified that this counterintuitive behavior can be strongly ascribed to the existence of "locally free charges" at domain wall.

Giant photovoltaic response in band engineered ferroelectric perovskite.

PubMed

Pal, Subhajit; Swain, Atal Bihari; Biswas, Pranab Parimal; Murali, D; Pal, Arnab; Nanda, B Ranjit K; Murugavel, Pattukkannu

2018-05-22

Recently the solar energy, an inevitable part of green energy source, has become a mandatory topics in frontier research areas. In this respect, non-centrosymmetric ferroelectric perovskites with open circuit voltage (V OC ) higher than the bandgap, gain tremendous importance as next generation photovoltaic materials. Here a non-toxic co-doped Ba 1-x (Bi 0.5 Li 0.5 ) x TiO 3 ferroelectric system is designed where the dopants influence the band topology in order to enhance the photovoltaic effect. In particular, at the optimal doping concentration (x opt  ~ 0.125) the sample reveals a remarkably high photogenerated field E OC  = 320 V/cm (V OC  = 16 V), highest ever reported in any bulk polycrystalline non-centrosymmetric systems. The band structure, examined through DFT calculations, suggests that the shift current mechanism is key to explain the large enhancement in photovoltaic effect in this family.

HS-SPM Mapping of Ferroelectric Domain Dynamics with Combined Nanoscale and Nanosecond Resolution

NASA Astrophysics Data System (ADS)

Polomoff, Nicholas Alexander

The unique properties of ferroelectric materials have been applied for a wide variety of device applications. In particular, properties such as spontaneous polarization and domain structure hysteresis at room temperature have rendered its application in nonvolatile memory devices such as FeRAMs. Along with the ever-present drive for smaller memory devices is the demand that they have increased operating speeds, longer retention times, lower power requirements and better overall reliability. It is therefore pertinent that further investigation of the dynamics, kinetics and mechanisms involved with ferroelectric domain polarization reversal at nanoscale lengths and temporal durations be conducted to optimize future ferroelectric based nonvolatile memory devices. Accordingly High Speed Piezoforce Microscopy (HSPFM) will be employed to directly investigate and observe the dynamic nucleation and growth progression of ferroelectric domain polarization reversal processes in thin epitaxial deposited PZT films. The capabilities of HSPFM will allow for in-situ direct observation of nascent dynamic domain polarization reversal events with nanoscale resolution. Correlations and characterization of the thin ferroelectric film samples will be made based on the observed polarization reversal dynamics and switching mechanism with respect to their varying strain states, compositions, and/or orientations. Electrical pulsing schemes will also be employed to enhance the HSPFM procedure to achieve nanoscale temporal resolution of nascent domain nucleation and growth events. A unique pulsing approach is also proposed, and tested, to improve power consumption during switching. Finally, artificial defects will be introduced into the PZT thin film by fabricating arrays of indentations with different shapes and loads. These controlled indents will result in the introduction of different stress states of compression and tension into the ferroelectric thin film. It is hypothesized that these

Spontaneous vortex nanodomain arrays at ferroelectric heterointerfaces.

PubMed

Nelson, Christopher T; Winchester, Benjamin; Zhang, Yi; Kim, Sung-Joo; Melville, Alexander; Adamo, Carolina; Folkman, Chad M; Baek, Seung-Hyub; Eom, Chang-Beom; Schlom, Darrell G; Chen, Long-Qing; Pan, Xiaoqing

2011-02-09

The polarization of the ferroelectric BiFeO(3) sub-jected to different electrical boundary conditions by heterointerfaces is imaged with atomic resolution using a spherical aberration-corrected transmission electron microscope. Unusual triangular-shaped nanodomains are seen, and their role in providing polarization closure is understood through phase-field simulations. Heterointerfaces are key to the performance of ferroelectric devices, and this first observation of spontaneous vortex nanodomain arrays at ferroelectric heterointerfaces reveals properties unlike the surrounding film including mixed Ising-Néel domain walls, which will affect switching behavior, and a drastic increase of in-plane polarization. The importance of magnetization closure has long been appreciated in multidomain ferromagnetic systems; imaging this analogous effect with atomic resolution at ferroelectric heterointerfaces provides the ability to see device-relevant interface issues. Extension of this technique to visualize domain dynamics is envisioned.

Ferroelectric-ferromagnetic coupling in hexagonal YMnO3 film

NASA Astrophysics Data System (ADS)

Cheng, Shaobo; Li, Menglei; Deng, Shiqing; Bao, Shanyong; Tang, Peizhe; Duan, Wenhui; Ma, Jing; Nan, Cewen; Zhu, Jing

Simultaneously achieving ferroelectricity and ferromagnetism in a single phase material is an important research topic in recent decades. Here, we demonstrate that with the modulation of oxygen vacancies, the ferroelectric-ferromagnetic coupling can be realized in the typical hexagonal manganite: YMnO3. The first-principal calculations are used to reveal the importance of oxygen vacancies on the alterations of magnetic behaviors for YMnO3. In order to obtain net magnetic moments, the on-top oxygen vacancies of MnO5 clusters should be created, thus the initial 2D spin frustration structure of Mn ions will be broken. By growing YMnO3 film on Al2O3 substrate, large in-plane compressive strain is induced, thus we can experimentally realize the on-top oxygen vacancies. With the help of SQUID and spherical aberration corrected TEM, the magnetic moments are experimentally measured and the correlations between the crystal structures and magnetic properties can be clearly understood. Our findings may pave a way for future applications of single phase multiferroic materials. National 973 Project of China (2015CB654902, 2011CB606405) and Chinese National Natural Science Foundation (11374174, 51390471).

Implementation of Ferroelectric Memories for Space Applications

NASA Technical Reports Server (NTRS)

Philpy, Stephen C.; Derbenwick, Gary F.; Kamp, David A.; Isaacson, Alan F.

2000-01-01

Ferroelectric random access semiconductor memories (FeRAMs) are an ideal nonvolatile solution for space applications. These memories have low power performance, high endurance and fast write times. By combining commercial ferroelectric memory technology with radiation hardened CMOS technology, nonvolatile semiconductor memories for space applications can be attained. Of the few radiation hardened semiconductor manufacturers, none have embraced the development of radiation hardened FeRAMs, due a limited commercial space market and funding limitations. Government funding may be necessary to assure the development of radiation hardened ferroelectric memories for space applications.

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.

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

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.

Ultrathin Ferroelectric Films: Growth, Characterization, Physics and Applications.

PubMed

Wang, Ying; Chen, Weijin; Wang, Biao; Zheng, Yue

2014-09-11

Ultrathin ferroelectric films are of increasing interests these years, owing to the need of device miniaturization and their wide spectrum of appealing properties. Recent advanced deposition methods and characterization techniques have largely broadened the scope of experimental researches of ultrathin ferroelectric films, pushing intensive property study and promising device applications. This review aims to cover state-of-the-art experimental works of ultrathin ferroelectric films, with a comprehensive survey of growth methods, characterization techniques, important phenomena and properties, as well as device applications. The strongest emphasis is on those aspects intimately related to the unique phenomena and physics of ultrathin ferroelectric films. Prospects and challenges of this field also have been highlighted.

Ultrathin Ferroelectric Films: Growth, Characterization, Physics and Applications

PubMed Central

Wang, Ying; Chen, Weijin; Wang, Biao; Zheng, Yue

2014-01-01

Ultrathin ferroelectric films are of increasing interests these years, owing to the need of device miniaturization and their wide spectrum of appealing properties. Recent advanced deposition methods and characterization techniques have largely broadened the scope of experimental researches of ultrathin ferroelectric films, pushing intensive property study and promising device applications. This review aims to cover state-of-the-art experimental works of ultrathin ferroelectric films, with a comprehensive survey of growth methods, characterization techniques, important phenomena and properties, as well as device applications. The strongest emphasis is on those aspects intimately related to the unique phenomena and physics of ultrathin ferroelectric films. Prospects and challenges of this field also have been highlighted. PMID:28788196

Ferroelectric ferrimagnetic LiFe2F6 : Charge-ordering-mediated magnetoelectricity

NASA Astrophysics Data System (ADS)

Lin, Ling-Fang; Xu, Qiao-Ru; Zhang, Yang; Zhang, Jun-Jie; Liang, Yan-Ping; Dong, Shuai

2017-12-01

Trirutile-type LiFe2F6 is a charge-ordered material with an Fe2 +/Fe3 + configuration. Here, its physical properties, including magnetism, electronic structure, phase transition, and charge ordering, are studied theoretically. On one hand, the charge ordering leads to improper ferroelectricity with a large polarization. On the other hand, its magnetic ground state can be tuned from the antiferromagnetic to ferrimagnetic by moderate compressive strain. Thus, LiFe2F6 can be a rare multiferroic with both large magnetization and polarization. Most importantly, since the charge ordering is the common ingredient for both ferroelectricity and magnetization, the net magnetization may be fully switched by flipping the polarization, rendering intrinsically strong magnetoelectric effects and desirable functions.

Ferroelectric BaTiO3 and LiNbO3 Nanoparticles Dispersed in Ferroelectric Liquid Crystal Mixtures: Electrooptic and Dielectric (Postprint)

DTIC Science & Technology

2016-10-14

Nematic Liquid Crystals allowing for rapidly changing moving pictures during the time frame below about 5-10 ms. Ferroelectric Liquid Crystals (FLCs...could fill this gap bearing some advantages over Nematic Liquid Crystals , mainly a fast switching time in the microsecond range, better optical...AFRL-RX-WP-JA-2017-0210 FERROELECTRIC BaTiO3 AND LiNbO3 NANOPARTICLES DISPERSED IN FERROELECTRIC LIQUID CRYSTAL MIXTURES: ELECTROOPTIC

Magnetically-induced ferroelectricity in the (ND4)2[FeCl5(D2O)] molecular compound

PubMed Central

Alberto Rodríguez-Velamazán, José; Fabelo, Óscar; Millán, Ángel; Campo, Javier; Johnson, Roger D.; Chapon, Laurent

2015-01-01

The number of magnetoelectric multiferroic materials reported to date is scarce, as magnetic structures that break inversion symmetry and induce an improper ferroelectric polarization typically arise through subtle competition between different magnetic interactions. The (NH4)2[FeCl5(H2O)] compound is a rare case where such improper ferroelectricity has been observed in a molecular material. We have used single crystal and powder neutron diffraction to obtain detailed solutions for the crystal and magnetic structures of (NH4)2[FeCl5(H2O)], from which we determined the mechanism of multiferroicity. From the crystal structure analysis, we observed an order-disorder phase transition related to the ordering of the ammonium counterion. We have determined the magnetic structure below TN, at 2 K and zero magnetic field, which corresponds to a cycloidal spin arrangement with magnetic moments contained in the ac-plane, propagating parallel to the c-axis. The observed ferroelectricity can be explained, from the obtained magnetic structure, via the inverse Dzyaloshinskii-Moriya mechanism. PMID:26417890

Strained enabled Ferroelectricity in CaTiO3 Thin Films Probed by Nonlinear Optics and Scanning Probe Microscopy

NASA Astrophysics Data System (ADS)

Vlahos, Eftihia; Kumar, Amit; Denev, Sava; Brooks, Charles; Schlom, Darrell; Eklund, Carl-Johan; Rabe, Karin M.; Fennie, Craig J.; Gopalan, Venkatraman

2009-03-01

Calcium titanate, CaTiO3 is not a ferroelectric in its bulk form. However, first principles calculations predict that biaxially tensile strained CaTiO3 thin films should become ferroelectric. Here, we indeed confirm that strained CaTiO3 films become ferroelectric with a Curie temperature of ˜125K. Optical second harmonic generation (SHG) measurements, polarization studies, and in-situ electric-field measurements for a number of films with different strain values will be presented: CaTiO3/DyScO3(110), CaTiO3/SrTiO3 (100),CaTiO3/GdScO3/NdGaO3(110), CaTiO3/LaSrAlO3(001) as well as for a single crystal CaTiO3. From these studies, we conclude that strained CaTiO3 films are ferroelectric with a point group symmetry of mm2, and show reversible domain switching characteristics under an electric field. We also present results of variable temperature piezoelectric force microscopy for imaging the polar domains in the ferroelectric phase. These results suggest that strain is a valuable tool for inducing polar, long range ferroelectric order in even non-polar ceramic materials such as CaTiO3.

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.

Epitaxial Growth of Thin Ferroelectric Polymer Films on Graphene Layer for Fully Transparent and Flexible Nonvolatile Memory.

PubMed

Kim, Kang Lib; Lee, Wonho; Hwang, Sun Kak; Joo, Se Hun; Cho, Suk Man; Song, Giyoung; Cho, Sung Hwan; Jeong, Beomjin; Hwang, Ihn; Ahn, Jong-Hyun; Yu, Young-Jun; Shin, Tae Joo; Kwak, Sang Kyu; Kang, Seok Ju; Park, Cheolmin

2016-01-13

Enhancing the device performance of organic memory devices while providing high optical transparency and mechanical flexibility requires an optimized combination of functional materials and smart device architecture design. However, it remains a great challenge to realize fully functional transparent and mechanically durable nonvolatile memory because of the limitations of conventional rigid, opaque metal electrodes. Here, we demonstrate ferroelectric nonvolatile memory devices that use graphene electrodes as the epitaxial growth substrate for crystalline poly(vinylidene fluoride-trifluoroethylene) (PVDF-TrFE) polymer. The strong crystallographic interaction between PVDF-TrFE and graphene results in the orientation of the crystals with distinct symmetry, which is favorable for polarization switching upon the electric field. The epitaxial growth of PVDF-TrFE on a graphene layer thus provides excellent ferroelectric performance with high remnant polarization in metal/ferroelectric polymer/metal devices. Furthermore, a fully transparent and flexible array of ferroelectric field effect transistors was successfully realized by adopting transparent poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] semiconducting polymer.

Giant Ferroelectric Polarization in Ultrathin Ferroelectrics via Boundary-Condition Engineering.

PubMed

Xie, Lin; Li, Linze; Heikes, Colin A; Zhang, Yi; Hong, Zijian; Gao, Peng; Nelson, Christopher T; Xue, Fei; Kioupakis, Emmanouil; Chen, Longqing; Schlom, Darrel G; Wang, Peng; Pan, Xiaoqing

2017-08-01

Tailoring and enhancing the functional properties of materials at reduced dimension is critical for continuous advancement of modern electronic devices. Here, the discovery of local surface induced giant spontaneous polarization in ultrathin BiFeO 3 ferroelectric films is reported. Using aberration-corrected scanning transmission electron microscopy, it is found that the spontaneous polarization in a 2 nm-thick ultrathin BiFeO 3 film is abnormally increased up to ≈90-100 µC cm -2 in the out-of-plane direction and a peculiar rumpled nanodomain structure with very large variation in c/a ratios, which is analogous to morphotropic phase boundaries (MPBs), is formed. By a combination of density functional theory and phase-field calculations, it is shown that it is the unique single atomic Bi 2 O 3 - x layer at the surface that leads to the enhanced polarization and appearance of the MPB-like nanodomain structure. This finding clearly demonstrates a novel route to the enhanced functional properties in the material system with reduced dimension via engineering the surface boundary conditions. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Laser Fabrication of Polymer Ferroelectric Nanostructures for Nonvolatile Organic Memory Devices.

PubMed

Martínez-Tong, Daniel E; Rodríguez-Rodríguez, Álvaro; Nogales, Aurora; García-Gutiérrez, Mari-Cruz; Pérez-Murano, Francesc; Llobet, Jordi; Ezquerra, Tiberio A; Rebollar, Esther

2015-09-09

Polymer ferroelectric laser-induced periodic surface structures (LIPSS) have been prepared on ferroelectric thin films of a poly(vinylidene fluoride-trifluoroethylene) copolymer. Although this copolymer does not absorb light at the laser wavelength, LIPSS on the copolymer can be obtained by forming a bilayer with other light-absorbing polymers. The ferroelectric nature of the structured bilayer was proven by piezoresponse force microscopy measurements. Ferroelectric hysteresis was found on both the bilayer and the laser-structured bilayer. We show that it is possible to write ferroelectric information at the nanoscale. The laser-structured ferroelectric bilayer showed an increase in the information storage density of an order of magnitude, in comparison to the original bilayer.

Ferroelectricity in high-density H 2O ice

DOE PAGES

Caracas, Razvan; Hemley, Russell J.

2015-04-01

The origin of longstanding anomalies in experimental studies of the dense solid phases of H 2O ices VII, VIII, and X is examined using a combination of first-principles theoretical methods. We find that a ferroelectric variant of ice VIII is energetically competitive with the established antiferroelectric form under pressure. The existence of domains of the ferroelectric form within anti-ferroelectric ice can explain previously observed splittings in x-ray diffraction data. The ferroelectric form is stabilized by density and is accompanied by the onset of spontaneous polarization. Here, the presence of local electric fields triggers the preferential parallel orientation of the watermore » molecules in the structure, which could be stabilized in bulk using new high-pressure techniques.« less

Negative Thermal Expansion and Ferroelectric Oxides in Electronic Device Composites

NASA Astrophysics Data System (ADS)

Trujillo, Joy Elizabeth

Electronic devices increasingly pervade our daily lives, driving the need to develop components which have material properties that can be designed to target a specific need. The principle motive of this thesis is to investigate the effects of particle size and composition on three oxides which possess electronic and thermal properties essential to designing improved ceramic composites for more efficient, high energy storage devices. A metal matrix composite project used the negative thermal expansion oxide, ZrW2O 8, to offset the high thermal expansion of the metal matrix without sacrificing high thermal conductivity. Composite preparation employed a powder mixing technique to achieve easy composition control and homogenous phase distribution in order to build composites which target a specific coefficient of thermal expansion (CTE). A tailorable CTE material is desirable for overcoming thermomechanical failure in heat sinks or device casings. This thesis also considers the particle size effect on dielectric properties in a common ferroelectric perovskite, Ba1-xSrxTiO 3. By varying the Ba:Sr ratio, the Curie temperature can be adjusted and by reducing the particle size, the dielectric constant can be increased and hysteresis decreased. These conditions could yield anonymously large dielectric constants near room temperature. However, the ferroelectric behavior has been observed to cease below a minimum size of a few tens of nanometers in bulk or thin film materials. Using a new particle slurry approach, electrochemical impedance spectroscopy allows dielectric properties to be determined for nanoparticles, as opposed to conventional methods which measure only bulk or thin film dielectric properties. In this manner, Ba1-xSrxTiO3 was investigated in a new size regime, extending the theory on the ferroelectric behavior to < 10 nm diameter. This knowledge will improve the potential to incorporate high dielectric constant, low loss ferroelectric nanoparticles in many

Quantum spin dynamics at terahertz frequencies in 2D hole gases and improper ferroelectrics

NASA Astrophysics Data System (ADS)

Lloyd-Hughes, J.

2015-08-01

Terahertz time-domain spectroscopy permits the excitations of novel materials to be examined with exquisite precision. Improper ferroelectric materials such as cupric oxide (CuO) exhibit complex magnetic ground states. CuO is antiferromagnetic below 213K, but has an incommensurate cycloidal magnetic phase between 213K and 230K. Remarkably, the cycloidal magnetic phase drives ferroelectricity, where the material becomes polar. Such improper multiferroics are of great contemporary interest, as a better understanding of the science of magnetoelectric materials may lead to their application in actuators, sensors and solid state memories. Improper multiferroics also have novel quasiparticle excitations: electromagnons form when spin-waves become electric-dipole active. By examining the dynamic response of spins as they interact with THz radiation we gain insights into the underlying physics of multi-ferroics. In contrast to improper ferroelectrics, where magnetism drives structural inversion asymmetry (SIA), two-dimensional electronic systems can exhibit non-degenerate spin states as a consequence of SIA created by strain and/or electric fields. We identify and explore the influence of the Rashba spin-orbit interaction upon cyclotron resonance at terahertz frequencies in high-mobility 2D hole gases in germanium quantum wells. An enhanced Rashba spin-orbit interaction can be linked to the strain of the quantum well, while a time-frequency decomposition method permitted the dynamical formation and decay of spin-split cyclotron resonances to be tracked on picosecond timescales. Long spin-decoherence times concurrent with high hole mobilities highlight the potential of Ge quantum wells in spintronics.

Phase-field model simulation of ferroelectric/antiferroelectric materials microstructure evolution under multiphysics loading

NASA Astrophysics Data System (ADS)

Zhang, Jingyi

Ferroelectric (FE) and closely related antiferroelectric (AFE) materials have unique electromechanical properties that promote various applications in the area of capacitors, sensors, generators (FE) and high density energy storage (AFE). These smart materials with extensive applications have drawn wide interest in the industrial and scientific world because of their reliability and tunable property. However, reliability issues changes its paradigms and requires guidance from detailed mechanism theory as the materials applications are pushed for better performance. A host of modeling work were dedicated to study the macro-structural behavior and microstructural evolution in FE and AFE material under various conditions. This thesis is focused on direct observation of domain evolution under multiphysics loading for both FE and AFE material. Landau-Devonshire time-dependent phase field models were built for both materials, and were simulated in finite element software Comsol. In FE model, dagger-shape 90 degree switched domain was observed at preexisting crack tip under pure mechanical loading. Polycrystal structure was tested under same condition, and blocking effect of the growth of dagger-shape switched domain from grain orientation difference and/or grain boundary was directly observed. AFE ceramic model was developed using two sublattice theory, this model was used to investigate the mechanism of energy efficiency increase with self-confined loading in experimental tests. Consistent results was found in simulation and careful investigation of calculation results gave confirmation that origin of energy density increase is from three aspects: self-confinement induced inner compression field as the cause of increase of critical field, fringe leak as the source of elevated saturation polarization and uneven defects distribution as the reason for critical field shifting and phase transition speed. Another important affecting aspect in polycrystalline materials is the

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

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)

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

Thermal fluctuations of ferroelectric nanodomains in a ferroelectric-dielectric PbTiO 3 / SrTiO 3 superlattice

DOE PAGES

Zhang, Qingteng; Dufresne, Eric M.; Chen, Pice; ...

2017-02-27

Ferroelectric-dielectric superlattices consisting of alternating layers of ferroelectric PbTiO 3 and dielectric SrTiO 3 exhibit a disordered striped nanodomain pattern, with characteristic length scales of 6 nm for the domain periodicity and 30 nm for the in-plane coherence of the domain pattern. Spatial disorder in the domain pattern gives rise to coherent hard x-ray scattering patterns exhibiting intensity speckles. We show here using variable-temperature Bragg-geometry x-ray photon correlation spectroscopy that x-ray scattering patterns from the disordered domains exhibit a continuous temporal decorrelation due to spontaneous domain fluctuations. The temporal decorrelation can be described using a compressed exponential function, consistent withmore » what has been observed in other systems with arrested dynamics. The fluctuation speeds up at higher temperatures and the thermal activation energy estimated from the Arrhenius model is 0.35±0.21 eV. As a result, the magnitude of the energy barrier implies that the complicated energy landscape of the domain structures is induced by pinning mechanisms and domain patterns fluctuate via the generation and annihilation of topological defects similar to soft materials such as block copolymers.« less

A phase field approach for the fully coupled thermo-electro-mechanical dynamics of nanoscale ferroelectric actuators

NASA Astrophysics Data System (ADS)

Wang, Dan; Du, Haoyuan; Wang, Linxiang; Melnik, Roderick

2018-05-01

The fully coupled thermo-electro-mechanical properties of nanoscale ferroelectric actuators are investigated by a phase field model. Firstly, the thermal effect is incorporated into the commonly-used phase field model for ferroelectric materials in a thermodynamic consistent way and the governing equation for the temperature field is derived. Afterwards, the modified model is numerically implemented to study a selected prototype of the ferroelectric actuators, where strain associated with electric field-induced non-180° domain switching is employed. The temperature variation and energy flow in the actuation process are presented, which enhances our understanding of the working mechanism of the actuators. Furthermore, the influences of the input voltage frequency and the thermal boundary condition on the temperature variation are demonstrated and carefully discussed in the context of thermal management for real applications.

Ferroelectric and multiferroic domain imaging by Laser-induced photoemission microscopy

NASA Astrophysics Data System (ADS)

Hoefer, Anke; Fechner, Michael; Duncker, Klaus; Mertig, Ingrid; Widdra, Wolf

2013-03-01

The ferroelectric as well as multiferroic surface domain structures of BaTiO3(001) and BiFeO3(001) are imaged based on photoemission electron microscopy (PEEM) by femtosecond laser threshold excitation under UHV conditions. For well-prepared BaTiO3(001), three ferroelectric domain types are clearly discriminable due to work function differences. At room temperature, the surface domains resemble the known ferroelectric domain structure of the bulk. Upon heating above the Curie point of 400 K, the specific surface domain pattern remains up to 500 K. Ab-initio calculations explain this observation by a remaining tetragonal distortion of the topmost unit cells stabilized by a surface relaxation. The (001) surface of the single-phase multiferroic BiFeO3 which is ferroelectric and antiferromagnetic, shows clear ferroelectric work function contrast in PEEM. Additionally, the multiferroic domains show significant linear dichroism. The observation of a varying dichroism for different ferroelectric domains can be explained based on the coupled ferroelectric-antiferromagnetic order in BiFeO3. It demonstrates multiferroic imaging of different domain types within a single, lab-based experiment.

Low-voltage operation of Si-based ferroelectric field effect transistors using organic ferroelectrics, poly(vinylidene fluoride-trifluoroethylene), as a gate dielectric

NASA Astrophysics Data System (ADS)

Miyata, Yusuke; Yoshimura, Takeshi; Ashida, Atsushi; Fujimura, Norifumi

2016-04-01

Si-based metal-ferroelectric-semiconductor (MFS) capacitors have been fabricated using poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] as a ferroelectric gate. The pinhole-free P(VDF-TrFE) thin films with high resistivity were able to be prepared by spin-coating directly onto hydrogen-terminated Si. The capacitance-voltage (C-V) characteristics of the ferroelectric gate field effect transistor (FeFET) using this MFS structure clearly show butterfly-shaped hysteresis originating from the ferroelectricity, indicating carrier modulation on the Si surface at gate voltages below 2 V. The drain current-gate voltage (I D-V G) characteristics also show counterclockwise hysteresis at gate voltages below 5 V. This is the first report on the low-voltage operation of a Si-based FeFET using P(VDF-TrFE) as a gate dielectric. This organic gate FeFET without any insulator layer at the ferroelectric/Si interface should be one of the promising devices for overcoming the critical issues of the FeFET, such as depolarization field and a decrease in the gate voltage.

Modeling and Implementation of HfO2-based Ferroelectric Tunnel Junctions

NASA Astrophysics Data System (ADS)

Pringle, Spencer Allen

HfO2-based ferroelectric tunnel junctions (FTJs) represent a unique opportunity as both a next-generation digital non-volatile memory and as synapse devices in braininspired logic systems, owing to their higher reliability compared to filamentary resistive random-access memory (ReRAM) and higher speed and lower power consumption compared to competing devices, including phase-change memory (PCM) and state-of-the-art FTJ. Ferroelectrics are often easier to deposit and have simpler material structure than films for magnetic tunnel junctions (MTJs). Ferroelectric HfO2 also enables complementary metal-oxide-semiconductor (CMOS) compatibility, since lead zirconate titanate (PZT) and BaTiO3-based FTJs often are not. No other groups have yet demonstrated a HfO2-based FTJ (to best of the author's knowledge) or applied it to a suitable system. For such devices to be useful, system designers require models based on both theoretical physical analysis and experimental results of fabricated devices in order to confidently design control systems. Both the CMOS circuitry and FTJs must then be designed in layout and fabricated on the same die. This work includes modeling of proposed device structures using a custom python script, which calculates theoretical potential barrier heights as a function of material properties and corresponding current densities (ranging from 8x103 to 3x10-2 A/cm 2 with RHRS/RLRS ranging from 5x105 to 6, depending on ferroelectric thickness). These equations were then combined with polynomial fits of experimental timing data and implemented in a Verilog-A behavioral analog model in Cadence Virtuoso. The author proposes tristate CMOS control systems, and circuits, for implementation of FTJ devices as digital memory and presents simulated performance. Finally, a process flow for fabrication of FTJ devices with CMOS is presented. This work has therefore enabled the fabrication of FTJ devices at RIT and the continued investigation of them as applied to any

Ferroelectric-like hysteresis loop originated from non-ferroelectric effects

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, Bora; Seol, Daehee; Lee, Shinbuhm

Piezoresponse force microscopy (PFM) has provided advanced nanoscale understanding and analysis of ferroelectric and piezoelectric properties. In PFM-based studies, electromechanical strain induced by the converse piezoelectric effect is probed and analyzed as a PFM response. However, electromechanical strain can also arise from several non-piezoelectric origins that may lead to a misinterpretation of the observed response. Among them, electrostatic interaction can significantly affect the PFM response. Nonetheless, previous studies explored solely the influence of electrostatic interaction on the PFM response under the situation accompanied with polarization switching. Here, we show the influence of the electrostatic interaction in the absence of polarizationmore » switching by using unipolar voltage sweep. The obtained results reveal that the electromechanical neutralization between piezoresponse of polarization and electrostatic interaction plays a crucial role in the observed ferroelectric-like hysteresis loop despite the absence of polarization switching. Furthermore, our work can provide a basic guideline for the correct interpretation of the hysteresis loop in PFM-based studies.« less

Ferroelectric-like hysteresis loop originated from non-ferroelectric effects

DOE PAGES

Kim, Bora; Seol, Daehee; Lee, Shinbuhm; ...

2016-09-06

Piezoresponse force microscopy (PFM) has provided advanced nanoscale understanding and analysis of ferroelectric and piezoelectric properties. In PFM-based studies, electromechanical strain induced by the converse piezoelectric effect is probed and analyzed as a PFM response. However, electromechanical strain can also arise from several non-piezoelectric origins that may lead to a misinterpretation of the observed response. Among them, electrostatic interaction can significantly affect the PFM response. Nonetheless, previous studies explored solely the influence of electrostatic interaction on the PFM response under the situation accompanied with polarization switching. Here, we show the influence of the electrostatic interaction in the absence of polarizationmore » switching by using unipolar voltage sweep. The obtained results reveal that the electromechanical neutralization between piezoresponse of polarization and electrostatic interaction plays a crucial role in the observed ferroelectric-like hysteresis loop despite the absence of polarization switching. Furthermore, our work can provide a basic guideline for the correct interpretation of the hysteresis loop in PFM-based studies.« less

Bipolar ferroelectric fatigue in (K0.5Na0.5)(Nb0.7Ta0.3)O3 ceramics and improved fatigue endurance on addition of ZnO

NASA Astrophysics Data System (ADS)

Vineetha, P.; Shanmuga Priya, B.; Venkata Saravanan, K.

2018-04-01

Ferroelectric ceramics are the key components in piezoelectric devices used today, thus long term reliability is a major industrial concern. The two important things that have to be considered in the ferroelectric material based device are aging and fatigue. The first one describes degradation with time whereas the later one is characterized by the change of material property during electrical loading. In the present work ferroelectric polarization and bipolar fatigue properties of undoped and ZnO doped lead free (K0.5Na0.5)(Nb0.7Ta0.3)O3 (KNNT) ceramics prepared by solid state reaction method were investigated. X-ray diffraction analysis of the samples reveal perovskite monoclinic phase along with the secondary phase of K2Nb4O11. The ferroelectric studies indicate that ZnO addition reduce fatigue as well as a well saturated hysteresis loop is obtained. The results reveal that addition of ZnO enhances the ferroelectric properties of KNNT ceramics.

Bilayered Hybrid Perovskite Ferroelectric with Giant Two-Photon Absorption.

PubMed

Li, Lina; Shang, Xiaoying; Wang, Sasa; Dong, Ningning; Ji, Chengmin; Chen, Xueyuan; Zhao, Sangen; Wang, Jun; Sun, Zhihua; Hong, Maochun; Luo, Junhua

2018-06-06

Perovskite ferroelectrics with prominent nonlinear optical absorption have attracted great attention in the field of photonics. However, they are traditionally dominated by inorganic oxides and exhibit relatively small nonlinear optical absorption coefficients, which hinder their further applications. Herein, we report a new organic-inorganic hybrid bilayered perovskite ferroelectric, (C 4 H 9 NH 3 ) 2 (NH 2 CHNH 2 )Pb 2 Br 7 (1), showing an above-room-temperature Curie temperature (∼322 K) and notable spontaneous polarization (∼3.8 μC cm -2 ). Significantly, the unique quantum-well structure of 1 results in intriguing two-photon absorption properties with a giant nonlinear optical absorption coefficient as high as 5.76 × 10 3 cm GW -1 , which is almost two-orders of magnitude larger than those of mostly traditional all-inorganic perovskite ferroelectrics. To our best knowledge, 1 is the first example of hybrid ferroelectrics with giant two-photon absorption coefficient. The mechanisms for ferroelectric and two-photon absorption are revealed. This work will shed light on the design of new ferroelectrics with two-photon absorption and promote their potentials in the photonic application.

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

DTIC Science & Technology

2015-07-06

analysis 4. http://wavefun.com 5. MOPAC2012, James J. P. Stewart, Stewart Computational Chemistry, Colorado Springs, CO, USA, HTTP://OpenMOPAC. net ... petri dish of mineral oil (to prevent electrical arcing) ripples in the mineral oil are clearly visible when a voltage is applied to the sample. We...acid. It does not appear to be ferroelectric. However, it is piezoelectric. When placed in a petri dish of mineral oil (to prevent electrical arcing

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.

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

Ultrafast acousto-optic mode conversion in optically birefringent ferroelectrics

NASA Astrophysics Data System (ADS)

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

2016-08-01

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.

Radiation-damage-assisted ferroelectric domain structuring in magnesium-doped lithium niobate

NASA Astrophysics Data System (ADS)

Jentjens, L.; Peithmann, K.; Maier, K.; Steigerwald, H.; Jungk, T.

2009-06-01

Irradiation of 5% magnesium-doped lithium niobate crystals (LiNbO3:Mg) with high-energy, low-mass 3He ions, which are transmitted through the crystal, changes the domain reversal properties of the material. This enables easier domain engineering compared to non-irradiated material and assists the formation of small-sized periodically poled domains in LiNbO3:Mg. Periodic domain structures exhibiting a width of ≈520 nm are obtained in radiation-damaged sections of the crystals. The ferroelectric poling behavior between irradiated and non-treated material is compared.

Intercorrelated In-Plane and Out-of-Plane Ferroelectricity in Ultrathin Two-Dimensional Layered Semiconductor In2Se3.

PubMed

Cui, Chaojie; Hu, Wei-Jin; Yan, Xingxu; Addiego, Christopher; Gao, Wenpei; Wang, Yao; Wang, Zhe; Li, Linze; Cheng, Yingchun; Li, Peng; Zhang, Xixiang; Alshareef, Husam N; Wu, Tom; Zhu, Wenguang; Pan, Xiaoqing; Li, Lain-Jong

2018-02-14

Enriching the functionality of ferroelectric materials with visible-light sensitivity and multiaxial switching capability would open up new opportunities for their applications in advanced information storage with diverse signal manipulation functions. We report experimental observations of robust intralayer ferroelectricity in two-dimensional (2D) van der Waals layered α-In 2 Se 3 ultrathin flakes at room temperature. Distinct from other 2D and conventional ferroelectrics, In 2 Se 3 exhibits intrinsically intercorrelated out-of-plane and in-plane polarization, where the reversal of the out-of-plane polarization by a vertical electric field also induces the rotation of the in-plane polarization. On the basis of the in-plane switchable diode effect and the narrow bandgap (∼1.3 eV) of ferroelectric In 2 Se 3 , a prototypical nonvolatile memory device, which can be manipulated both by electric field and visible light illumination, is demonstrated for advancing data storage technologies.

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.

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.

Fringing field effects in negative capacitance field-effect transistors with a ferroelectric gate insulator

NASA Astrophysics Data System (ADS)

Hattori, Junichi; Fukuda, Koichi; Ikegami, Tsutomu; Ota, Hiroyuki; Migita, Shinji; Asai, Hidehiro; Toriumi, Akira

2018-04-01

We study the effects of fringing electric fields on the behavior of negative-capacitance (NC) field-effect transistors (FETs) with a silicon-on-insulator body and a gate stack consisting of an oxide film, an internal metal film, a ferroelectric film, and a gate electrode using our own device simulator that can properly handle the complicated relationship between the polarization and the electric field in ferroelectric materials. The behaviors of such NC FETs and the corresponding metal-oxide-semiconductor (MOS) FETs are simulated and compared with each other to evaluate the effects of the NC of the ferroelectric film. Then, the fringing field effects are evaluated by comparing the NC effects in NC FETs with and without gate spacers. The fringing field between the gate stack, especially the internal metal film, and the source/drain region induces more charges at the interface of the film with the ferroelectric film. Accordingly, the function of the NC to modulate the gate voltage and the resulting function to improve the subthreshold swing are enhanced. We also investigate the relationships of these fringing field effects to the drain voltage and four design parameters of NC FETs, i.e., gate length, gate spacer permittivity, internal metal film thickness, and oxide film thickness.

Smart Materials for Electromagnetic and Optical Applications

NASA Astrophysics Data System (ADS)

Ramesh, Prashanth

The research presented in this dissertation focuses on the development of solid-state materials that have the ability to sense, act, think and communicate. Two broad classes of materials, namely ferroelectrics and wideband gap semiconductors were investigated for this purpose. Ferroelectrics possess coupled electromechanical behavior which makes them sensitive to mechanical strains and fluctuations in ambient temperature. Use of ferroelectrics in antenna structures, especially those subject to mechanical and thermal loads, requires knowledge of the phenomenological relationship between the ferroelectric properties of interest (especially dielectric permittivity) and the external physical variables, viz. electric field(s), mechanical strains and temperature. To this end, a phenomenological model of ferroelectric materials based on the Devonshire thermodynamic theory was developed. This model was then used to obtain a relationship expressing the dependence of the dielectric permittivity on the mechanical strain, applied electric field and ambient temperature. The relationship is shown to compare well with published experimental data and other related models in literature. A model relating ferroelectric loss tangent to the applied electric field and temperature is also discussed. Subsequently, relationships expressing the dependence of antenna operating frequency and radiation efficiency on those external physical quantities are described. These relationships demonstrate the tunability of load-bearing antenna structures that integrate ferroelectrics when they are subjected to mechanical and thermal loads. In order to address the inability of ferroelectrics to integrate microelectronic devices, a feature needed in a material capable of sensing, acting, thinking and communicating, the material Gallium Nitride (GaN) is pursued next. There is an increasing utilization of GaN in the area of microelectronics due to the advantages it offers over other semiconductors. This

FAST TRACK COMMUNICATION: Interlayer exchange coupling across a ferroelectric barrier

NASA Astrophysics Data System (ADS)

Zhuravlev, M. Ye; Vedyayev, A. V.; Tsymbal, E. Y.

2010-09-01

A new magnetoelectric effect is predicted originating from the interlayer exchange coupling between two ferromagnetic layers separated by an ultrathin ferroelectric barrier. It is demonstrated that ferroelectric polarization switching driven by an external electric field leads to a sizable change in the interlayer exchange coupling. The effect occurs in asymmetric ferromagnet/ferroelectric/ferromagnet junctions due to a change in the electrostatic potential profile across the junction affecting the interlayer coupling. The predicted phenomenon indicates the possibility of switching the magnetic configuration by reversing the polarization of the ferroelectric barrier layer.

Ferroelectric memory evaluation and development system

NASA Astrophysics Data System (ADS)

Bondurant, David W.

Attention is given to the Ramtron FEDS-1, an IBM PC/AT compatible single-board 16-b microcomputer with 8-kbyte program/data memory implemented with nonvolatile ferroelectric dynamic RAM. This is the first demonstration of a new type of solid state nonvolatile read/write memory, the ferroelectric RAM (FRAM). It is suggested that this memory technology will have a significant impact on avionics system performance and reliability.

Measurement of Ferroelectric Films in MFM and MFIS Structures

NASA Astrophysics Data System (ADS)

Anderson, Jackson D.

For many years ferroelectric memory has been used in applications requiring low power, yet mainstream adoption has been stifled due to integration and scaling issues. With the renewed interest in these devices due to the recent discovery of ferroelectricity in HfO2, it is imperative that the properties of these films are well understood. To aid that end, a ferroelectric analysis package has been developed and released on GitHub and PyPI under a creative commons non-commercial share-alike license. This package contains functions for visualization and analysis of data from polarization, leakage current, and FORC measurements as well as basic modeling capability. Functionality is verified via the analysis of lead zirconate titanate (PZT) capacitors, where a multi-domain simulation based on an experimental Preisach density shows decent agreement despite measurement noise. The package is then used in the analysis of ferroelectric HfO2 films deposited in metal-ferroelectric-metal (MFM) and metal-ferroelectric-insulator-semiconductor (MFIS) stacks. 13.5 nm HfO2 films deposited on a semiconductor surface are shown to have a coercive voltage of 2.5 V, rather than the 1.9 V of the film in an MFM stack. This value further increases to 3-5 V when a lightly doped semiconductor depletion and inversion capacitance is added to the stack. The magnitude of this change is more than can be accounted for from the 10% voltage drop across the interfacial oxide layer, indicating that the modified surface properties are impacting the formation of the ferroelectric phase during anneal. In light of this, care should be taken to map out ferroelectric HfO2 properties using the particular physical stack that will be used, rather than using an MFM stack as a proxy.

Low-voltage tunable color in full visible region using ferroelectric liquid-crystal-doped cholesteric liquid-crystal smart materials

NASA Astrophysics Data System (ADS)

Lin, Jia-De; Lin, Jyun-Wei; Lee, Chia-Rong

2018-02-01

Electrical tuning of photonic bandgap (PBG) of cholesteric liquid crystal (CLC) without deformation within the entire visible region at low voltages is not easy to achieve. This study demonstrates low-voltage-tunable PBG in full visible region with less deformation of the PBG based on smart materials of ferroelectric liquid crystal doped CLC (FLC-CLC) integrating with electrothermal film heaters. Experimental results show that the reflective color of the FLC-CLC can be low-voltage-tuned through entire visible region. The induced temperature change is induced by electrically heating the electrothermal film heaters at low voltages at near the smectic-CLC transition temperature. Coaxial electrospinning can be used to develop smart fibrous devices with FLC/CLC-core and polymer-shell which color is tunable in full visible region at low voltages.

Soft tilt and rotational modes in the hybrid improper ferroelectric Ca3Mn2O7

NASA Astrophysics Data System (ADS)

Glamazda, A.; Wulferding, D.; Lemmens, P.; Gao, B.; Cheong, S.-W.; Choi, K.-Y.

2018-03-01

Raman spectroscopy is employed to probe directly the soft rotation and tilting modes, which are two primary order parameters predicted in the hybrid improper ferroelectric material Ca3Mn2O7 . We observe a giant softening of the 107 -cm-1 octahedron tilting mode by 26 cm-1 on heating through the structural transition from a ferroelectric to paraelectric orthorhombic phase. This is contrasted by a small softening of the 150 -cm-1 rotational mode by 6 cm-1. In the intermediate phase, the competing soft modes with different symmetries coexist, bringing about many-faceted anomalies in spin excitations and lattice vibrations. Our work demonstrates that the soft rotation and tilt patterns, relying on a phase-transition path, are a key factor in determining ferroelectric, magnetic, and lattice properties of Ca3Mn2O7 .

A battery-less photo-detector enabled with simultaneous ferroelectric sensing and energy harnessing mechanism

NASA Astrophysics Data System (ADS)

Lai, Szu Cheng; Yao, Kui; Chen, Yi Fan

2013-08-01

A self-sustainable mechanism for simultaneously sensing and harnessing photon energy was proposed and implemented to create a battery-less and wire-less ultraviolet sensor made of ferroelectric lead lanthanum zirconate titanate thin film with in-plane polarization configuration. The mechanism involved accumulating and storing the photovoltaic charge, and transferring the stored charge via a piezoelectric switch to a radio frequency transmitter. The time-interval between the radio frequency pulses generated by the transmitter was inversely proportional to the photo-intensity. The sustainability of the operation was ascribed to the low leakage, high photovoltage, and linear current-voltage characteristics of ferroelectric sensing material instead of semiconductors.

Ferroelectricity in epitaxial Y-doped HfO2 thin film integrated on Si substrate

NASA Astrophysics Data System (ADS)

Lee, K.; Lee, T. Y.; Yang, S. M.; Lee, D. H.; Park, J.; Chae, S. C.

2018-05-01

We report on the ferroelectricity of a Y-doped HfO2 thin film epitaxially grown on Si substrate, with an yttria-stabilized zirconia buffer layer pre-deposited on the substrate. Piezoresponse force microscopy results show the ferroelectric domain pattern, implying the existence of ferroelectricity in the epitaxial HfO2 film. The epitaxially stabilized HfO2 film in the form of a metal-ferroelectric-insulator-semiconductor structure exhibits ferroelectric hysteresis with a clear ferroelectric switching current in polarization-voltage measurements. The HfO2 thin film also demonstrates ferroelectric retention comparable to that of current perovskite-based metal-ferroelectric-insulator-semiconductor structures.

Bandlike Transport in Ferroelectric-Based Organic Field-Effect Transistors

NASA Astrophysics Data System (ADS)

Laudari, A.; Guha, S.

2016-10-01

The dielectric constant of polymer-ferroelectric dielectrics may be tuned by changing the temperature, offering a platform for monitoring changes in interfacial transport with the polarization strength in organic field-effect transistors (FETs). Temperature-dependent transport studies of FETs are carried out from a solution-processed organic semiconductor, 6,13-bis(triisopropylsilylethynyl)pentacene (TIPS-pentacene), using both ferroelectric- and nonferroelectric-gate insulators. Nonferroelectric dielectric-based TIPS-pentacene FETs show a clear activated transport, in contrast to the ferroelectric dielectric polymer, poly(vinylidene fluoride-trifluoroethylene), where a negative temperature coefficient of the mobility is observed in the ferroelectric temperature range. The current-voltage (I -V ) characteristics from TIPS-pentacene diodes signal a space-charge-limited conduction (SCLC) for a discrete set of trap levels, suggesting that charge injection and transport occurs through regions of ordering in the semiconductor. The carrier mobility extracted from temperature-dependent I -V characteristics from the trap-free SCLC region shows a negative coefficient beyond 200 K, similar to the trend observed in FETs with the ferroelectric dielectric. At moderate temperatures, the polarization-fluctuation-dominant transport inherent in a ferroelectric dielectric, in conjunction with the nature of traps, results in an effective detrapping of the shallow-trap states into more mobile states in TIPS-pentacene.

Displacement-type ferroelectric transition with magnetic Mn ions in perovskite Sr1-xBaxMnO3

NASA Astrophysics Data System (ADS)

Sakai, Hideaki; Fujioka, Jun; Fukuda, Tatsuo; Okuyama, Daisuke; Hashizume, Daisuke; Kagawa, Fumitaka; Nakao, Hironori; Murakami, Youich; Arima, Takahisa; Baron, Alfred Q. R.; Taguchi, Yasujiro; Tokura, Yoshinori

2012-02-01

Almost all the proper ferroelectrics with a perovskite structure discovered so far have no d-electrons in the off-center transition metal site, as exemplified by BaTiO3 and Pb(Zr,Ti)O3. This empirical d^0 rule is incompatible with the emergence of magnetism and has significantly restricted the variety of multiferroic materials. In this work, we have discovered a displacement-type ferroelectric transition originating from off-center Mn^4+ ions in antiferromagnetic Mott insulators Sr1-xBaxMnO3. As Ba concentration increases, the perovskite lattice shows the typical soft mode dynamics, and the ferroelectricity shows up for x .45. In addition to the large polarization and high transition temperature comparable to BaTiO3, we demonstrate that the magnetic order suppresses the ferroelectric lattice dilation by ˜70% and increases the soft-phonon energy by ˜50%, indicating gigantic magnetoelectric effects [1]. This work was supported by the FIRST program on ``Quantum Science on Strong Correlation''. [4pt] [1] H. Sakai et al., Phys. Rev. Lett. 107, 137601 (2011).

Removable polytetrafluoroethylene template based epitaxy of ferroelectric copolymer thin films

NASA Astrophysics Data System (ADS)

Xia, Wei; Chen, Qiusong; Zhang, Jian; Wang, Hui; Cheng, Qian; Jiang, Yulong; Zhu, Guodong

2018-04-01

In recent years ferroelectric polymers have shown their great potentials in organic and flexible electronics. To meet the requirements of high-performance and low energy consumption of novel electronic devices and systems, structural and electrical properties of ferroelectric polymer thin films are expected to be further optimized. One possible way is to realize epitaxial growth of ferroelectric thin films via removable high-ordered polytetrafluoroethylene (PTFE) templates. Here two key parameters in epitaxy process, annealing temperature and applied pressure, are systematically studied and thus optimized through structural and electrical measurements of ferroelectric copolymer thin films. Experimental results indicate that controlled epitaxial growth is realized via suitable combination of both parameters. Annealing temperature above the melting point of ferroelectric copolymer films is required, and simultaneously moderate pressure (around 2.0 MPa here) should be applied. Over-low pressure (around 1.0 MPa here) usually results in the failure of epitaxy process, while over-high pressure (around 3.0 MPa here) often results in residual of PTFE templates on ferroelectric thin films.

Zero Thermal Expansion and Semiconducting Properties in PbTiO3-Bi(Co, Ti)O3 Ferroelectric Solid Solutions.

PubMed

Pan, Zhao; Chen, Jun; Jiang, Xingxing; Lin, Zheshuai; Zhang, Linxing; Fan, Longlong; Rong, Yangchun; Hu, Lei; Liu, Hui; Ren, Yang; Kuang, Xiaojun; Xing, Xianran

2017-03-06

Zero thermal expansion (ZTE) behavior is rare but important for both fundamental studies and practical applications of functional materials. Until now, most available ZTE materials are either electrical insulating oxides or conductive metallic compounds. Very few ZTE materials exhibit the semiconductor feature. Here we report a ZTE in a semiconducting ferroelectric of 0.6PbTiO 3 -0.4Bi(Co 0.55 Ti 0.45 )O 3-δ . Its unit cell volume exhibits a negligible change over a broad temperature range from room temperature to 500 °C. The ZTE is supposed to be correlated with the spontaneous volume ferroelectronstriction. Intriguingly, the present ZTE material also exhibits the semiconducting characteristic accompanied by negative temperature coefficient of resistance. The mechanism of electric conduction is attributed to the electronic hopping from one ion (Ti 3+ ) to another (Ti 4+ ). The semiconductor nature has also been confirmed by the noticeable visible-light absorption with the relatively lower band gap (E g ) value of 1.5 eV, while the ferroelectric property can be well-maintained with large polarization. The first-principles calculations reveal that the drastically narrowed E g is related to the Co-Ti substitution. The present multifunctional material containing ZTE, semiconducting, and ferroelectric properties is suggested to enable new applications such as the substrate for solar conversion devices.

A novel readout integrated circuit for ferroelectric FPA detector

NASA Astrophysics Data System (ADS)

Bai, Piji; Li, Lihua; Ji, Yulong; Zhang, Jia; Li, Min; Liang, Yan; Hu, Yanbo; Li, Songying

2017-11-01

Uncooled infrared detectors haves some advantages such as low cost light weight low power consumption, and superior reliability, compared with cryogenically cooled ones Ferroelectric uncooled focal plane array(FPA) are being developed for its AC response and its high reliability As a key part of the ferroelectric assembly the ROIC determines the performance of the assembly. A top-down design model for uncooled ferroelectric readout integrated circuit(ROIC) has been developed. Based on the optical thermal and electrical properties of the ferroelectric detector the RTIA readout integrated circuit is designed. The noise bandwidth of RTIA readout circuit has been developed and analyzed. A novel high gain amplifier, a high pass filter and a low pass filter circuits are designed on the ROIC. In order to improve the ferroelectric FPA package performance and decrease of package cost a temperature sensor is designed on the ROIC chip At last the novel RTIA ROIC is implemented on 0.6μm 2P3M CMOS silicon techniques. According to the experimental chip test results the temporal root mean square(RMS)noise voltage is about 1.4mV the sensitivity of the on chip temperature sensor is 0.6 mV/K from -40°C to 60°C the linearity performance of the ROIC chip is better than 99% Based on the 320×240 RTIA ROIC, a 320×240 infrared ferroelectric FPA is fabricated and tested. Test results shows that the 320×240 RTIA ROIC meets the demand of infrared ferroelectric FPA.

Discovery of stable skyrmionic state in ferroelectric nanocomposites

NASA Astrophysics Data System (ADS)

Nahas, Y.; Prokhorenko, S.; Louis, L.; Gui, Z.; Kornev, I.; Bellaiche, L.

2015-10-01

Non-coplanar swirling field textures, or skyrmions, are now widely recognized as objects of both fundamental interest and technological relevance. So far, skyrmions were amply investigated in magnets, where due to the presence of chiral interactions, these topological objects were found to be intrinsically stabilized. Ferroelectrics on the other hand, lacking such chiral interactions, were somewhat left aside in this quest. Here we demonstrate, via the use of a first-principles-based framework, that skyrmionic configuration of polarization can be extrinsically stabilized in ferroelectric nanocomposites. The interplay between the considered confined geometry and the dipolar interaction underlying the ferroelectric phase instability induces skyrmionic configurations. The topological structure of the obtained electrical skyrmion can be mapped onto the topology of domain-wall junctions. Furthermore, the stabilized electrical skyrmion can be as small as a few nanometers, thus revealing prospective skyrmion-based applications of ferroelectric nanocomposites.

Nonvolatile Ferroelectric Memory Circuit Using Black Phosphorus Nanosheet-Based Field-Effect Transistors with P(VDF-TrFE) Polymer.

PubMed

Lee, Young Tack; Kwon, Hyeokjae; Kim, Jin Sung; Kim, Hong-Hee; Lee, Yun Jae; Lim, Jung Ah; Song, Yong-Won; Yi, Yeonjin; Choi, Won-Kook; Hwang, Do Kyung; Im, Seongil

2015-10-27

Two-dimensional van der Waals (2D vdWs) materials are a class of new materials that can provide important resources for future electronics and materials sciences due to their unique physical properties. Among 2D vdWs materials, black phosphorus (BP) has exhibited significant potential for use in electronic and optoelectronic applications because of its allotropic properties, high mobility, and direct and narrow band gap. Here, we demonstrate a few-layered BP-based nonvolatile memory transistor with a poly(vinylidenefluoride-trifluoroethylene) (P(VDF-TrFE)) ferroelectric top gate insulator. Experiments showed that our BP-based ferroelectric transistors operate satisfactorily at room temperature in ambient air and exhibit a clear memory window. Unlike conventional ambipolar BP transistors, our ferroelectric transistors showed only p-type characteristics due to the carbon-fluorine (C-F) dipole effect of the P(VDF-TrFE) layer, as well as the highest linear mobility value of 1159 cm(2) V(-1) s(-1) with a 10(3) on/off current ratio. For more advanced memory applications beyond unit memory devices, we implemented two memory inverter circuits, a resistive-load inverter circuit and a complementary inverter circuit, combined with an n-type molybdenum disulfide (MoS2) nanosheet. Our memory inverter circuits displayed a clear memory window of 15 V and memory output voltage efficiency of 95%.

Metallic 'Ferroelectrity' in the Pyrochlore Cd 2Re 2O 7

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sergienko, I. A.; Keppens, Veerle; McGuire, M. A.

2004-01-01

A class of materials known as 'ferroelectric metals' was discussed theoretically by Anderson and Blount in 1965, but to date no examples of this class have been reported. Here we present measurements of the elastic moduli of Cd{sub 2}Re{sub 2}O{sub 7} through the 200 K cubic-to-tetragonal phase transition. A Landau analysis of the moduli reveals that the transition is consistent with Cd{sub 2}Re{sub 2}O{sub 7} being classified as a 'ferroelectric metal' in the weaker sense described by Anderson and Blount (loss of a center of symmetry). First-principles calculations of the lattice instabilities indicate that the dominant lattice instability corresponds tomore » a two-fold degenerate mode with Eu symmetry, and that motions of the O ions forming the O octahedra dominate the energetics of the transition.« less

Mechanical switching of ferroelectric domains beyond flexoelectricity

NASA Astrophysics Data System (ADS)

Chen, Weijin; Liu, Jianyi; Ma, Lele; Liu, Linjie; Jiang, G. L.; Zheng, Yue

2018-02-01

The resurgence of interest in flexoelectricity has prompted discussions on the feasibility of switching ferroelectric domains 'non-electrically'. In this work, we perform three-dimensional thermodynamic simulations in combination with ab initio calculations and effective Hamiltonian simulations to demonstrate the great effects of surface screening and surface bonding on ferroelectric domain switching triggered by local tip loading. A three-dimensional simulation scheme has been developed to capture the tip-induced domain switching behavior in ferroelectric thin films by adequately taking into account the surface screening effect and surface bonding effect of the ferroelectric film, as well as the finite elastic stiffness of the substrate and the electrode layers. The major findings are as follows. (i) Compared with flexoelectricity, surface effects can be overwhelming and lead to much more efficient mechanical switching caused by tip loading. (ii) The surface-assisted mechanical switching can be bi-directional without the necessity of reversing strain gradients. (iii) A mode transition from local to propagating domain switching occurs when the screening below a critical value. A ripple effect of domain switching appears with the formation of concentric loop domains. (iv) The ripple effect can lead to 'domain interference' and a deterministic writing of confined loop domain patterns by local excitations. Our study reveals the hidden switching mechanisms of ferroelectric domains and the possible roles of surface in mechanical switching. The ripple effect of domain switching, which is believed to be general in dipole systems, broadens our current knowledge of domain engineering.

Performance of thin-film ferroelectric capacitors for EMC decoupling.

PubMed

Li, Huadong; Subramanyam, Guru

2008-12-01

This paper studied the effects of thin-film ferroelectrics as decoupling capacitors for electromagnetic compatibility applications. The impedance and insertion loss of PZT capacitors were measured and compared with the results from commercial off-the-shelf capacitors. An equivalent circuit model was extracted from the experimental results, and a considerable series resistance was found to exist in ferroelectric capacitors. This resistance gives rise to the observed performance difference around series resonance between ferroelectric PZT capacitors and normal capacitors. Measurements on paraelectric (Ba,Sr)TiO(3)-based integrated varactors do not show this significant resistance. Some analyses were made to investigate the mechanisms, and it was found that it can be due to the hysteresis in the ferroelectric thin films.

Electronic structure of stoichiometric and oxygen-deficient ferroelectric Hf0.5Zr0.5O2.

PubMed

Perevalov, T V; Islamov, D R; Gritsenko, V A; Prosvirin, I P

2018-05-11

The electronic structure of oxygen-deficient Hf 0.5 Zr 0.5 O 2 in the non-centrosymmetric orthorhombic (ferroelectric) phase was investigated by means of x-ray photoelectron spectroscopy and first-principle density functional theory calculations. It was established that a peak in the photoelectron spectra observed at an energy above the valence band top of ferroelectric Hf 0.5 Zr 0.5 O 2 in ion-etched samples was due to oxygen vacancies. A method for evaluating the oxygen vacancies concentration in the material from the comparison of experimental and theoretical photoelectron spectra of the valence band is proposed. It is found that oxygen polyvacancies are not formed in ferroelectric Hf 0.5 Zr 0.5 O 2 : an energy-favorable spatial arrangement of several oxygen vacancies in the crystal corresponds to the configuration formed by noninteracting vacancies distant from each other. The oxygen vacancies in five charged states were simulated. The electron levels in the bandgap caused by charged oxygen vacancies indicate that any type of oxygen vacancies in ferroelectric Hf 0.5 Zr 0.5 O 2 can capture both electrons and holes, i.e. can act as an amphoteric localization center for charge carriers.

Phase-field modeling of chemical control of polarization stability and switching dynamics in ferroelectric thin films

DOE PAGES

Cao, Ye; Kalinin, Sergei V.

2016-12-15

Phase-field simulation (PFS) has revolutionized the understanding of domain structure and switching behavior in ferroelectric thin films and ceramics. Generally, PFS is based on the solution of (a set of) Landau-Ginzburg-Devonshire equations for a defined order parameter field(s) under physical boundary conditions (BCs) of fixed potential or charge. While well matched to the interfaces in bulk materials and devices, these BCs are generally not applicable to free ferroelectric surfaces. Here, we developed a self-consistent phase-field model with BCs based on electrochemical equilibria. We chose Pb(Zr 0.2Ti 0.8)O 3 ultrathin film consisting of (001) oriented single tetragonal domain ( Pz) asmore » a model system and systematically studied the effects of oxygen partial pressure, temperature, and surface ions on the ferroelectric state and compared it with the case of complete screening. We have further explored the polarization switching induced by the oxygen partial pressure and observed pronounced size effect induced by chemical screening. Finally, our paper thus helps to understand the emergent phenomena in ferroelectric thin films brought about by the electrochemical ionic surface compensations.« less

Phase-field modeling of chemical control of polarization stability and switching dynamics in ferroelectric thin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cao, Ye; Kalinin, Sergei V.

Phase-field simulation (PFS) has revolutionized the understanding of domain structure and switching behavior in ferroelectric thin films and ceramics. Generally, PFS is based on the solution of (a set of) Landau-Ginzburg-Devonshire equations for a defined order parameter field(s) under physical boundary conditions (BCs) of fixed potential or charge. While well matched to the interfaces in bulk materials and devices, these BCs are generally not applicable to free ferroelectric surfaces. Here, we developed a self-consistent phase-field model with BCs based on electrochemical equilibria. We chose Pb(Zr 0.2Ti 0.8)O 3 ultrathin film consisting of (001) oriented single tetragonal domain ( Pz) asmore » a model system and systematically studied the effects of oxygen partial pressure, temperature, and surface ions on the ferroelectric state and compared it with the case of complete screening. We have further explored the polarization switching induced by the oxygen partial pressure and observed pronounced size effect induced by chemical screening. Finally, our paper thus helps to understand the emergent phenomena in ferroelectric thin films brought about by the electrochemical ionic surface compensations.« less

Electronic structure of stoichiometric and oxygen-deficient ferroelectric Hf0.5Zr0.5O2

NASA Astrophysics Data System (ADS)

Perevalov, T. V.; Islamov, D. R.; Gritsenko, V. A.; Prosvirin, I. P.

2018-05-01

The electronic structure of oxygen-deficient Hf0.5Zr0.5O2 in the non-centrosymmetric orthorhombic (ferroelectric) phase was investigated by means of x-ray photoelectron spectroscopy and first-principle density functional theory calculations. It was established that a peak in the photoelectron spectra observed at an energy above the valence band top of ferroelectric Hf0.5Zr0.5O2 in ion-etched samples was due to oxygen vacancies. A method for evaluating the oxygen vacancies concentration in the material from the comparison of experimental and theoretical photoelectron spectra of the valence band is proposed. It is found that oxygen polyvacancies are not formed in ferroelectric Hf0.5Zr0.5O2: an energy-favorable spatial arrangement of several oxygen vacancies in the crystal corresponds to the configuration formed by noninteracting vacancies distant from each other. The oxygen vacancies in five charged states were simulated. The electron levels in the bandgap caused by charged oxygen vacancies indicate that any type of oxygen vacancies in ferroelectric Hf0.5Zr0.5O2 can capture both electrons and holes, i.e. can act as an amphoteric localization center for charge carriers.

TOPICAL REVIEW: First principles studies of multiferroic materials

NASA Astrophysics Data System (ADS)

Picozzi, Silvia; Ederer, Claude

2009-07-01

Multiferroics, materials where spontaneous long-range magnetic and dipolar orders coexist, represent an attractive class of compounds, which combine rich and fascinating fundamental physics with a technologically appealing potential for applications in the general area of spintronics. Ab initio calculations have significantly contributed to recent progress in this area, by elucidating different mechanisms for multiferroicity and providing essential information on various compounds where these effects are manifestly at play. In particular, here we present examples of density-functional theory investigations for two main classes of materials: (a) multiferroics where ferroelectricity is driven by hybridization or purely structural effects, with BiFeO3 as the prototype material, and (b) multiferroics where ferroelectricity is driven by correlation effects and is strongly linked to electronic degrees of freedom such as spin-, charge-, or orbital-ordering, with rare-earth manganites as prototypes. As for the first class of multiferroics, first principles calculations are shown to provide an accurate qualitative and quantitative description of the physics in BiFeO3, ranging from the prediction of large ferroelectric polarization and weak ferromagnetism, over the effect of epitaxial strain, to the identification of possible scenarios for coupling between ferroelectric and magnetic order. For the second class of multiferroics, ab initio calculations have shown that, in those cases where spin-ordering breaks inversion symmetry (e.g. in antiferromagnetic E-type HoMnO3), the magnetically induced ferroelectric polarization can be as large as a few µC cm-2. The examples presented point the way to several possible avenues for future research: on the technological side, first principles simulations can contribute to a rational materials design, aimed at identifying spintronic materials that exhibit ferromagnetism and ferroelectricity at or above room temperature. On the

Novel two-dimensional ferroelectric PbTe under tension: A first-principles prediction

NASA Astrophysics Data System (ADS)

Zhang, Xilin; Yang, Zongxian; Chen, Yue

2017-08-01

Enhanced ferroelectricity in two-dimensional (2D) SnTe exhibiting a higher transition temperature (Tc) than its bulk counterpart was recently discovered [Chang et al., Science 353(6296), 274-278 (2016)]. Herein, we report that nonferroelectric PbTe can be transformed into a ferroelectric phase by downsizing to two dimensions with suitable equi-biaxial tension. The crystal structure of the ferroelectric phase of 2D PbTe was determined using evolutionary algorithms and density functional theory. The dynamic stabilities of the predicted new phases were investigated using phonon calculations. To validate our results obtained using PbTe, we have also studied the ferroelectricity in GeTe and SnTe at the 2D level and compared them with the literature. The unequal lattice constants and the relative atomic displacements are found to be responsible for ferroelectricity in 2D GeTe, SnTe, and strained PbTe. This study facilitates the development of new 2D ferroelectrics via strain engineering and promotes the integration of ferroelectric devices.

Emergent Low-Symmetry Phases and Large Property Enhancements in Ferroelectric KNbO 3 Bulk Crystals [Emergent Low-Symmetry Phases with Large Property Enhancement in Ferroelectric KNbO 3 Bulk Crystals

DOE PAGES

Lummen, Tom T. A.; Leung, J.; Kumar, Amit; ...

2017-06-19

The design of new or enhanced functionality in materials is traditionally viewed as requiring the discovery of new chemical compositions through synthesis. Large property enhancements may however also be hidden within already well-known materials, when their structural symmetry is deviated from equilibrium through a small local strain or field. Here, the discovery of enhanced material properties associated with a new metastable phase of monoclinic symmetry within bulk KNbO 3 is reported. This phase is found to coexist with the nominal orthorhombic phase at room temperature, and is both induced by and stabilized with local strains generated by a network ofmore » ferroelectric domain walls. While the local microstructural shear strain involved is only ≈0.017%, the concurrent symmetry reduction results in an optical second harmonic generation response that is over 550% higher at room temperature. Moreover, the meandering walls of the low-symmetry domains also exhibit enhanced electrical conductivity on the order of 1 S m -1. In conclusion, this discovery reveals a potential new route to local engineering of significant property enhancements and conductivity through symmetry lowering in ferroelectric crystals.« less

Ferroelectric order in liquid crystal phases of polar disk-shaped ellipsoids

NASA Astrophysics Data System (ADS)

Bose, Tushar Kanti; Saha, Jayashree

2014-05-01

The demonstration of a spontaneous macroscopic ferroelectric order in liquid phases in the absence of any long range positional order is considered an outstanding problem of both fundamental and technological interest. Recently, we reported that a system of polar achiral disklike ellipsoids can spontaneously exhibit a long searched ferroelectric nematic phase and a ferroelectric columnar phase with strong axial polarization. The major role is played by the dipolar interactions. The model system of interest consists of attractive-repulsive Gay-Berne oblate ellipsoids embedded with two parallel point dipoles positioned symmetrically on the equatorial plane of the ellipsoids. In the present work, we investigate in detail the profound effects of changing the separation between the two symmetrically placed dipoles and the strength of the dipoles upon the existence of different ferroelectric discotic liquid crystal phases via extensive off-lattice N-P-T Monte Carlo simulations. Ferroelectric biaxial phases are exhibited in addition to the uniaxial ferroelectric fluids where the phase biaxiality results from the dipolar interactions. The structures of all the ferroelectric configurations of interest are presented in detail. Simple phase diagrams are determined which include different polar and apolar discotic fluids generated by the system.

Materials for Adaptive Structural Acoustic Control. Volume 2

DTIC Science & Technology

1994-04-11

Cross. Effects of Electrodes and Elecu’oding Methods on Fatigue Behavior in Ferroelectric Materials. Ferroelectrics: Proceedings of IMF8, Gaithersburg...describe the linear piezoelectric behavior of ferroelectric ceramics. We have generalized this model to describe the nonlinear effects resulting from...report some of the nonlinear effects under resonant conditions for a PZT-501A ceramic. Figure 8 shows the complex admittance circles at different

Simultaneous dynamic characterization of charge and structural motion during ferroelectric switching

NASA Astrophysics Data System (ADS)

Kwamen, C.; Rössle, M.; Reinhardt, M.; Leitenberger, W.; Zamponi, F.; Alexe, M.; Bargheer, M.

2017-10-01

Monitoring structural changes in ferroelectric thin films during electric field induced polarization switching is important for a full microscopic understanding of the coupled motion of charges, atoms, and domain walls in ferroelectric nanostructures. We combine standard ferroelectric test sequences of switching and nonswitching electrical pulses with time-resolved x-ray diffraction to investigate the structural response of a nanoscale Pb (Zr0.2Ti0.8) O3 ferroelectric oxide capacitor upon charging, discharging, and polarization reversal. We observe that a nonlinear piezoelectric response of the ferroelectric layer develops on a much longer time scale than the R C time constant of the device. The complex atomic motion during the ferroelectric polarization reversal starts with a contraction of the lattice, whereas the expansive piezoelectric response sets in after considerable charge flow due to the applied voltage pulses on the electrodes of the capacitor. Our simultaneous measurements on a working device elucidate and visualize the complex interplay of charge flow and structural motion and challenges theoretical modeling.

Dynamic amplification of light signals in photorefractive ferroelectric liquid crystal blends containing photoconductive chiral dopant

NASA Astrophysics Data System (ADS)

Sasaki, T.; Hafuri, M.; Suda, T.; Nakano, M.; Funada, K.; Ohta, M.; Terazono, T.; Le, K. V.; Naka, Y.

2017-08-01

Effect of ferroelectricity on the photorefractive effect of ferroelectric liquid crystal blends was investigated. The photorefractive effect of ferroelectric liquid crystal blends strongly depend on the ferroelectricity of the blend. We have prepared a series of ferroelectric liquid crystal blends that contains several concentrations of a chiral compound while keeping a constant concentration of a photoconductive moiety. The photorefractive properties of the ferroelectric liquid crystal blends were discussed with relations to the ferroelectric properties of the blends.

Complete stress-induced depolarization of relaxor ferroelectric crystals without transition through a non-polar phase

NASA Astrophysics Data System (ADS)

Shkuratov, Sergey I.; Baird, Jason; Antipov, Vladimir G.; Hackenberger, Wesley; Luo, Jun; Zhang, Shujun; Lynch, Christopher S.; Chase, Jay B.; Jo, Hwan R.; Roberts, Christopher C.

2018-03-01

The development of relaxor ferroelectric single crystal technology is driven by the ability to tailor ferroelectric properties through domain engineering not achievable in polycrystalline materials. In this study, three types of domain-engineered rhombohedral Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 crystals were subjected to transverse high strain rate loading. The experimental results indicate that the domain configuration has a significant effect on the stress-induced depolarization and the associated charge released. A complete depolarization of the single-domain crystals with 3m symmetry is observed, while multidomain crystals with 4mm and mm2 symmetries retain a fraction of their initial remanent polarization. The complete depolarization of single-domain crystals is unique without transition to a non-polar phase, with a stress-induced charge density of 0.48 C/m2. This is up to three times higher than that of the multidomain crystals and PbZrxTi1-xO3 ferroelectric ceramics that are critical for ultrahigh-power transducer applications. The main offering of this work is to propose a detailed mechanism for complete stress-induced depolarization in ferroelectric crystals which does not involve an intermediate transformation to a non-polar phase.

Ultra-High-Density Ferroelectric Memories

NASA Technical Reports Server (NTRS)

Thakoor, Sarita

1995-01-01

Features include fast input and output via optical fibers. Memory devices of proposed type include thin ferroelectric films in which data stored in form of electric polarization. Assuming one datum stored in region as small as polarization domain, sizes of such domains impose upper limits on achievable storage densities. Limits approach 1 terabit/cm(Sup2) in all-optical versions of these ferroelectric memories and exceeds 1 gigabit/cm(Sup2) in optoelectronic versions. Memories expected to exhibit operational lives of about 10 years, input/output times of about 10 ns, and fatigue lives of about 10(Sup13) cycles.

Giant electroresistance of super-tetragonal BiFeO3-based ferroelectric tunnel junctions.

PubMed

Yamada, Hiroyuki; Garcia, Vincent; Fusil, Stéphane; Boyn, Sören; Marinova, Maya; Gloter, Alexandre; Xavier, Stéphane; Grollier, Julie; Jacquet, Eric; Carrétéro, Cécile; Deranlot, Cyrile; Bibes, Manuel; Barthélémy, Agnès

2013-06-25

Ferroelectric tunnel junctions enable a nondestructive readout of the ferroelectric state via a change of resistance induced by switching the ferroelectric polarization. We fabricated submicrometer solid-state ferroelectric tunnel junctions based on a recently discovered polymorph of BiFeO3 with giant axial ratio ("T-phase"). Applying voltage pulses to the junctions leads to the highest resistance changes (OFF/ON ratio >10,000) ever reported with ferroelectric tunnel junctions. Along with the good retention properties, this giant effect reinforces the interest in nonvolatile memories based on ferroelectric tunnel junctions. We also show that the changes in resistance scale with the nucleation and growth of ferroelectric domains in the ultrathin BiFeO3 (imaged by piezoresponse force microscopy), thereby suggesting potential as multilevel memory cells and memristors.

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)

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

Observation of a periodic array of flux-closure quadrants in strained ferroelectric PbTiO 3 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 PbTiO 3 films, mediated by tensile strain on a GdScO 3 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 PbTiO 3 film thickness. In the vicinity of the core, the strain is sufficient to rupture the lattice, with strainmore » gradients up to 10 9 per meter. We found engineering strain at the nanoscale may facilitate the development of nanoscale ferroelectric devices.« less

A ferroelectric model for the low emissivity highlands on Venus

NASA Technical Reports Server (NTRS)

Shepard, Michael K.; Arvidson, Raymond E.; Brackett, Robert A.; Fegley, Bruce, Jr.

1994-01-01

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 (10(exp 5)) 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.

Zero thermal expansion and semiconducting properties in PbTiO 3 –Bi(Co, Ti)O 3 ferroelectric solid solutions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pan, Zhao; Chen, Jun; Jiang, Xingxing

Zero thermal expansion (ZTE) behavior is rare but important for both fundamental studies and practical applications of functional materials. Up to now, most available ZTE materials are either electrical insulating oxides or conductive metallic compounds. Very few ZTE materials exhibit the semiconductor feature. Here we report a ZTE in semiconducting ferroelectric of 0.6PbTiO 3-0.4Bi(Co 0.55Ti 0.45)O 3-δ. Its unit cell volume exhibits a negligible change over a broad temperature range from room temperature to 500 °C. The ZTE is supposed to be correlated with the spontaneous volume ferroelectronstriction. Intriguingly, the present ZTE material also exhibits the semiconducting characteristic accompanied bymore » negative temperature coefficient of resistance. The mechanism of electric conduction is attributed to the electronic hopping from one ionic (Ti 3+) to another (Ti 4+). The semiconductor nature has also been confirmed by the noticeable visible-light absorption with the relative lower band-gap (E g) value of 1.5 eV, while ferroelectric property can be well maintained with large polarization. The first-principles calculations reveal that the drastically narrowed E g is related to the Co-Ti substitution. Finally, the present multifunctional material containing ZTE, semiconducting and ferroelectric properties is suggested to enable new applications such as the substrate for solar conversion devices.« less

Zero thermal expansion and semiconducting properties in PbTiO 3 –Bi(Co, Ti)O 3 ferroelectric solid solutions

DOE PAGES

Pan, Zhao; Chen, Jun; Jiang, Xingxing; ...

2017-02-16

Zero thermal expansion (ZTE) behavior is rare but important for both fundamental studies and practical applications of functional materials. Up to now, most available ZTE materials are either electrical insulating oxides or conductive metallic compounds. Very few ZTE materials exhibit the semiconductor feature. Here we report a ZTE in semiconducting ferroelectric of 0.6PbTiO 3-0.4Bi(Co 0.55Ti 0.45)O 3-δ. Its unit cell volume exhibits a negligible change over a broad temperature range from room temperature to 500 °C. The ZTE is supposed to be correlated with the spontaneous volume ferroelectronstriction. Intriguingly, the present ZTE material also exhibits the semiconducting characteristic accompanied bymore » negative temperature coefficient of resistance. The mechanism of electric conduction is attributed to the electronic hopping from one ionic (Ti 3+) to another (Ti 4+). The semiconductor nature has also been confirmed by the noticeable visible-light absorption with the relative lower band-gap (E g) value of 1.5 eV, while ferroelectric property can be well maintained with large polarization. The first-principles calculations reveal that the drastically narrowed E g is related to the Co-Ti substitution. Finally, the present multifunctional material containing ZTE, semiconducting and ferroelectric properties is suggested to enable new applications such as the substrate for solar conversion devices.« less

Computational study of textured ferroelectric polycrystals: Dielectric and piezoelectric properties of template-matrix composites

NASA Astrophysics Data System (ADS)

Zhou, Jie E.; Yan, Yongke; Priya, Shashank; Wang, Yu U.

2017-01-01

Quantitative relationships between processing, microstructure, and properties in textured ferroelectric polycrystals and the underlying responsible mechanisms are investigated by phase field modeling and computer simulation. This study focuses on three important aspects of textured ferroelectric ceramics: (i) grain microstructure evolution during templated grain growth processing, (ii) crystallographic texture development as a function of volume fraction and seed size of the templates, and (iii) dielectric and piezoelectric properties of the obtained template-matrix composites of textured polycrystals. Findings on the third aspect are presented here, while an accompanying paper of this work reports findings on the first two aspects. In this paper, the competing effects of crystallographic texture and template seed volume fraction on the dielectric and piezoelectric properties of ferroelectric polycrystals are investigated. The phase field model of ferroelectric composites consisting of template seeds embedded in matrix grains is developed to simulate domain evolution, polarization-electric field (P-E), and strain-electric field (ɛ-E) hysteresis loops. The coercive field, remnant polarization, dielectric permittivity, piezoelectric coefficient, and dissipation factor are studied as a function of grain texture and template seed volume fraction. It is found that, while crystallographic texture significantly improves the polycrystal properties towards those of single crystals, a higher volume fraction of template seeds tends to decrease the electromechanical properties, thus canceling the advantage of ferroelectric polycrystals textured by templated grain growth processing. This competing detrimental effect is shown to arise from the composite effect, where the template phase possesses material properties inferior to the matrix phase, causing mechanical clamping and charge accumulation at inter-phase interfaces between matrix and template inclusions. The computational

Giant electrode effect on tunnelling electroresistance in ferroelectric tunnel junctions.

PubMed

Soni, Rohit; Petraru, Adrian; Meuffels, Paul; Vavra, Ondrej; Ziegler, Martin; Kim, Seong Keun; Jeong, Doo Seok; Pertsev, Nikolay A; Kohlstedt, Hermann

2014-11-17

Among recently discovered ferroelectricity-related phenomena, the tunnelling electroresistance (TER) effect in ferroelectric tunnel junctions (FTJs) has been attracting rapidly increasing attention owing to the emerging possibilities of non-volatile memory, logic and neuromorphic computing applications of these quantum nanostructures. Despite recent advances in experimental and theoretical studies of FTJs, many questions concerning their electrical behaviour still remain open. In particular, the role of ferroelectric/electrode interfaces and the separation of the ferroelectric-driven TER effect from electrochemical ('redox'-based) resistance-switching effects have to be clarified. Here we report the results of a comprehensive study of epitaxial junctions comprising BaTiO(3) barrier, La(0.7)Sr(0.3)MnO(3) bottom electrode and Au or Cu top electrodes. Our results demonstrate a giant electrode effect on the TER of these asymmetric FTJs. The revealed phenomena are attributed to the microscopic interfacial effect of ferroelectric origin, which is supported by the observation of redox-based resistance switching at much higher voltages.

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.

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.

Facilitation of Ferroelectric Switching via Mechanical Manipulation of Hierarchical Nanoscale Domain Structures.

PubMed

Chen, Zibin; Hong, Liang; Wang, Feifei; Ringer, Simon P; Chen, Long-Qing; Luo, Haosu; Liao, Xiaozhou

2017-01-06

Heterogeneous ferroelastic transition that produces hierarchical 90° tetragonal nanodomains via mechanical loading and its effect on facilitating ferroelectric domain switching in relaxor-based ferroelectrics were explored. Combining in situ electron microscopy characterization and phase-field modeling, we reveal the nature of the transition process and discover that the transition lowers by 40% the electrical loading threshold needed for ferroelectric domain switching. Our results advance the fundamental understanding of ferroelectric domain switching behavior.

Electric-field-induced local and mesoscale structural changes in polycrystalline dielectrics and ferroelectrics

DOE PAGES

Usher, Tedi -Marie; Levin, Igor; Daniels, John E.; ...

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, BaTiO 3 andmore » Na ½Bi ½TiO 3, and dielectric SrTiO 3. For Na ½Bi ½TiO 3, 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 BaTiO 3 and SrTiO 3, the local/nanoscale structural changes observed in the PDFs are dominated by piezoelectric lattice strain and ionic polarizability, respectively.« less

Ferroelectricity in Pb 1+δZrO 3 Thin Films

DOE PAGES

Gao, Ran; Reyes-Lillo, Sebastian E.; Xu, Ruijuan; ...

2017-07-16

Antiferroelectric PbZrO 3 is being considered for a wide range of applications where the competition between centrosymmetric and noncentrosymmetric phases is important to the response. Here, we focus on the epitaxial growth of PbZrO 3 thin films and understanding the chemistry structure coupling in Pb 1+δ ZrO 3 (δ = 0, 0.1, 0.2). High-quality, single-phase Pb 1+δZrO 3 films are synthesized via pulsed-laser deposition. Though no significant lattice parameter change is observed in X-ray studies, electrical characterization reveals that while the PbZrO 3 and Pb 1.1ZrO 3 heterostructures remain intrinsically antiferroelectric, the Pb 1.2ZrO 3 heterostructures exhibit a hysteresis loopmore » indicative of ferroelectric response. Furthermore X-ray scattering studies reveal strong quarter-order diffraction peaks in PbZrO 3 and Pb 1.1ZrO 3 heterostructures indicative of antiferroelectricity, while no such peaks are observed for Pb 1.2ZrO 3 heterostructures. Density functional theory calculations suggest the large cation nonstoichiometry is accommodated by incorporation of antisite Pb-Zr defects, which drive the Pb 1.2ZrO 3 heterostructures to a ferroelectric phase with R3c symmetry. In the end, stabilization of metastable phases in materials via chemical nonstoichiometry and defect engineering enables a novel route to manipulate the energy of the ground state of materials and the corresponding material properties.« less

Surface engineering of ferroelectric polymer for the enhanced electrical performance of organic transistor memory

NASA Astrophysics Data System (ADS)

Kim, Do-Kyung; Lee, Gyu-Jeong; Lee, Jae-Hyun; Kim, Min-Hoi; Bae, Jin-Hyuk

2018-05-01

We suggest a viable surface control method to improve the electrical properties of organic nonvolatile memory transistors. For viable surface control, the surface of the ferroelectric insulator in the memory field-effect transistors was modified using a smooth-contact-curing process. For the modification of the ferroelectric polymer, during the curing of the ferroelectric insulators, the smooth surface of a soft elastomer contacts intimately with the ferroelectric surface. This smooth-contact-curing process reduced the surface roughness of the ferroelectric insulator without degrading its ferroelectric properties. The reduced roughness of the ferroelectric insulator increases the mobility of the organic field-effect transistor by approximately eight times, which results in a high memory on–off ratio and a low-voltage reading operation.

Study of the structure and ferroelectric behavior of BaBi4-xLaxTi4O15 ceramics

NASA Astrophysics Data System (ADS)

Khokhar, Anita; Goyal, Parveen K.; Thakur, O. P.; Sreenivas, K.

2015-06-01

The structure and ferroelectric properties of Lanthanum substituted barium bismuth titanate BaBi4-xLaxTi4O15 (0 ≤ x ≤ 0.5) ceramics prepared by solid-state reaction method have been investigated. X-ray diffraction (XRD) confirms the formation of a single phase material. The distribution of lanthanum into the perovskite layers and (Bi2O2)2+ layers of BaBi4Ti4O15 ceramics have been revealed through Raman spectroscopy. At lower value of x, it is seen that La3+ ions prefer to substitute A-site Bi3+ ions in the perovskite layers while for higher x values, La3+ ions get incorporated into the (Bi2O2)2+ layers. A critical La content of x ˜ 0.2 in BaBi4-xLaxTi4O15 is seen to exhibit a large remnant polarization (Pr) with low coercive field (Ec). The improvement in the ferroelectric properties of La substituted BaBi4Ti4O15 ceramics has been explained in terms of changing oxygen vacancy concentration and structural relaxation. Tunable ferroelectric materials can be obtained by manipulating the doping amount of lanthanum ion.

Study of the structure, dielectric and ferroelectric behavior of BaBi4+δTi4O15 ceramics

NASA Astrophysics Data System (ADS)

Khokhar, Anita; Goyal, Parveen K.; Thakur, O. P.; Sreenivas, K.

2016-05-01

The structure and ferroelectric properties of excess bismuth doped barium bismuth titanate BaBi4+δTi4O15 (δ = 2 - 10 wt.%)) ceramics prepared by solid-state reaction method have been investigated. X-ray diffraction (XRD) confirms the formation of a single phase material with a change in the orthorhombic distortion with varying excess of bismuth content. There is no change in the phase transition temperature (Tm) while the relaxor behaviour has been modified significantly with excess of bismuth doping. Saturated hysteresis loops with high remnant polarization (Pr ~ 12.5 µC/cm2), low coercive fields (Ec ~ 26 kV/cm) are measured and a high piezoelectric coefficient (d33 ~ 29 pC/N) is achieved in poled BaBi4Ti4O15 ceramics prepared with up to 8 wt.% of excess bismuth oxide. The improvement in the ferroelectric properties with increase in the excess bismuth content in BaBi4Ti4O15 ceramics has been explained in terms of changing oxygen vacancy concentration and structural relaxation. Tunable ferroelectric materials can be obtained by manipulating the doping amount of excess bismuth.

Thermodynamic Phenomenology for Perovskite Structure Ferroelectric Solid Solutions with Morphotropic Phase Boundaries

DTIC Science & Technology

2005-12-13

American Advanced Study Institute on Science and Technology of Ferroelectric Materials: Rosario Argentina, September 2002. a. Brief History of...zirconium-rich rhombohedral perovskite and the titani - composition. 8,𔄃) um-rich tetragonal perovskite phases. Within recent years, three factors have...of Physics. [DOI: 10.1063/1.1570517] The well-known elastoelectric coupling effects include When reviewing the history of flexoelectric investiga

Synthesis and ferroelectric properties of La-substituted PZFNT

NASA Astrophysics Data System (ADS)

Singh, Pratibha; Singh, Sangeeta; Juneja, J. K.; Prakash, Chandra; Raina, K. K.; Kumar, Vinod; Pant, R. P.

2010-01-01

In this paper we are reporting a systematic study on ferroelectric properties of lanthanum (La) substituted modified lead zirconate titanate (PLZFNT) ceramics which were fabricated by mixed oxide process. La contents were varied in between 0 and 0.01 in steps of 0.0025. The X-ray diffraction study shows single phase for all samples. Silver electrode was deposited on flat surfaces of sintered discs for P-E (polarization vs. electric field) measurements. All compositions exhibited well-defined ferroelectric behavior at room temperature. Hysteresis loops were also recorded at different temperatures for all the compositions which showed typical variation of ferroelectric nature. The PLZFNT composition with 1 mol% of La showed the best retention behavior. The results are discussed.

Investigation of Ferroelectric Domain Walls by Raman Spectroscopy

NASA Astrophysics Data System (ADS)

Stone, Gregory A.

Ferroelectric materials are characterized by an intrinsic spontaneous electric dipole moment that can be manipulated by the application of an electric field. Regions inside the crystal, known as domains, can have the spontaneous dipole moments oriented in a different direction than the surrounding crystal. Due to favorable piezoelectric, pyroelectric, electro-optic, and nonlinear optical properties, ferroelectric materials are attractive for commercial applications. Many devices, such as nonlinear frequency converters, require precisely engineered domain patterns. The properties of domains and their boundaries, known as domain walls, are vital to the performance and limitations of these devices. As a result, ferroelectric domains and the domain walls have been the focus of many scientific studies. Despite all this work, questions remain regarding their properties. This work is aimed at developing a better understanding of the properties of the domain wall using confocal Raman spectroscopy. Raman spectra taken from domain walls in Lithium Niobate and Lithium Tantalate reveal two distinct changes in the Raman spectra: (1) Shifts in frequency of the bulk Raman modes, which persists over a range of 0.2-0.5 mu m from the domain wall. The absence of this effect in defect free stoichiometric Lithium Tantalate indicates that the shifts are related to defects inside the crystal. (2) The presence of Raman modes corresponding to phonons propagating orthogonal to the laser beam axis, which are not collected in the bulk crystal. The phonons also preferential propagate normal to the domain wall. These modes are detected up to 0.35 mum from the domain wall. The observation and separation of these effects was made possible by the optimized spatial resolution (0.23 mum) of a home-built scanning confocal microscope and the fact that degeneracy of the transverse and longitudinal phonon polarization is lifted by polar phonons in Lithium Niobate and Lithium Tantalate. Raman

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.

Coupled ferroelectric polarization and magnetization in spinel FeCr2S4

PubMed Central

Lin, L.; Zhu, H. X.; Jiang, X. M.; Wang, K. F.; Dong, S.; Yan, Z. B.; Yang, Z. R.; Wan, J. G.; Liu, J.-M.

2014-01-01

One of the core issues for multiferroicity is the strongly coupled ferroelectric polarization and magnetization, while so far most multiferroics have antiferromagnetic order with nearly zero magnetization. Magnetic spinel compounds with ferrimagnetic order may be alternative candidates offering large magnetization when ferroelectricity can be activated simultaneously. In this work, we investigate the ferroelectricity and magnetism of spinel FeCr2S4 in which the Fe2+ sublattice and Cr3+ sublattice are coupled in antiparallel alignment. Well defined ferroelectric transitions below the Fe2+ orbital ordering termperature Too = 8.5 K are demonstrated. The ferroelectric polarization has two components. One component arises mainly from the noncollinear conical spin order associated with the spin-orbit coupling, which is thus magnetic field sensitive. The other is probably attributed to the Jahn-Teller distortion induced lattice symmetry breaking, occuring below the orbital ordering of Fe2+. Furthermore, the coupled ferroelectric polarization and magnetization in response to magnetic field are observed. The present work suggests that spinel FeCr2S4 is a multiferroic offering both ferroelectricity and ferrimagnetism with large net magnetization. PMID:25284432

Method for disclosing invisible physical properties in metal-ferroelectric-insulator-semiconductor gate stacks

NASA Astrophysics Data System (ADS)

Sakai, Shigeki; Zhang, Wei; Takahashi, Mitsue

2017-04-01

In metal-ferroelectric-insulator-semiconductor gate stacks of ferroelectric-gate field effect transistors (FeFETs), it is impossible to directly obtain curves of polarization versus electric field (P f-E f) in the ferroelectric layer. The P f-E f behavior is not simple, i.e. the P f-E f curves are hysteretic and nonlinear, and the hysteresis curve width depends on the electric field scan amplitude. Unless the P f-E f relation is known, the field E f strength cannot be solved when the voltage is applied between the gate meal and the semiconductor substrate, and thus P f-E f cannot be obtained after all. In this paper, the method for disclosing the relationships among the polarization peak-to-peak amplitude (2P mm_av), the electric field peak-to-peak amplitude (2E mm_av), and the memory window (E w) in units of the electric field is presented. To get P mm_av versus E mm_av, FeFETs with different ferroelectric-layer thicknesses should be prepared. Knowing such essential physical parameters is helpful and in many cases enough to quantitatively understand the behavior of FeFETs. The method is applied to three groups. The first one consists of SrBi2Ta2O9-based FeFETs. The second and third ones consist of Ca x Sr1-x Bi2Ta2O9-based FeFETs made by two kinds of annealing. The method can clearly differentiate the characters of the three groups. By applying the method, ferroelectric relationships among P mm_av, E mm_av, and E w are well classified in the three groups according to the difference of the material kinds and the annealing conditions. The method also evaluates equivalent oxide thickness (EOT) of a dual layer of a deposited high-k insulator and a thermally-grown SiO2-like interfacial layer (IL). The IL thickness calculated by the method is consistent with cross-sectional image of the FeFETs observed by a transmission electron microscope. The method successfully discloses individual characteristics of the ferroelectric and the insulator layers hidden in the gate stack

On bistable states retention in ferroelectric Langmuir-Blodgett films

NASA Astrophysics Data System (ADS)

Geivandov, A. R.; Palto, S. P.; Yudin, S. G.; Fridkin, V. M.; Blinov, L. M.; Ducharme, S.

2003-08-01

A new insight into the nature of ferroelectricity is emerging from the study of ultra-thin ferroelectric films prepared of poly(vinylidene fluoride with trifluoroethylene) copolymer using Langmuir-Blodgett (LB) technique. Unique properties of these films indicate the existence of two-dimensional ferroelectricity. The retention of two polarized states in ferroelectric polymer LB films is studied using nonlinear dielectric spectroscopy. The technique is based on phase sensitive measurements of nonlinear dielectric spectroscopy. The amplitude of the current response at the 2nd harmonic of the applied voltage is proportional to the magnitude of the remnant polarization, while its phase gives the sign. We have found that 10 - 20 mm thick LB films can show fast switching time and long retention of the two polarized states. Nevertheless, LB films show a pronounced asymmetry in switching to the opposite states. Possible mechanisms of such behavior are discussed.

Polarization-coupled tunable resistive behavior in oxide ferroelectric heterostructures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gruverman, Alexei; Tsymbal, Evgeny Y.; Eom, Chang-Beom

2017-05-03

This research focuses on investigation of the physical mechanism of the electrically and mechanically tunable resistive behavior in oxide ferroelectric heterostructures with engineered interfaces realized via a strong coupling of ferroelectric polarization with tunneling electroresistance and metal-insulator (M-I) transitions. This report describes observation of electrically conductive domain walls in semiconducting ferroelectrics, voltage-free control of resistive switching and demonstration of a new mechanism of electrical control of 2D electron gas (2DEG) at oxide interfaces. The research goals are achieved by creating strong synergy between cutting-edge fabrication of epitaxial single-crystalline complex oxides, nanoscale electrical characterization by scanning probe microscopy and theoretical modelingmore » of the observed phenomena. The concept of the ferroelectric devices with electrically and mechanically tunable nonvolatile resistance represents a new paradigm shift in realization of the next-generation of non-volatile memory devices and low-power logic switches.« less

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.

Study on structural, dielectric, ferroelectric and piezoelectric properties of Ba doped Lead Zirconate Titanate Ceramics

NASA Astrophysics Data System (ADS)

Dipti; Juneja, J. K.; Singh, Sangeeta; Raina, K. K.; Prakash, Chandra

2013-12-01

The perovskite Pb(1-x)BaxZr0.55Ti0.45O3 material (x=0.00, 0.01, 0.02, 0.03, 0.05, and 0.07) was synthesized by solid state reaction route. Green bodies were sintered at 1250 °C. All samples were subjected to X-ray diffraction analysis and they were found to be in single phase. Dielectric properties were studied as a function of temperature and frequency. Ferroelectric properties were studied as a function of temperature. Remnant polarization, saturation polarization and coercive field were determined for all the samples using ferroelectric loops. Piezoelectric properties such as d33 and electromechanical coupling factor (kp) were also measured at room temperature for all samples.

Computational findings of metastable ferroelectric phases of squaric acid

NASA Astrophysics Data System (ADS)

Ishibashi, Shoji; Horiuchi, Sachio; Kumai, Reiji

2018-05-01

Antiferroelectric-to-ferroelectric transitions in squaric acid are simulated by computationally applying a static electric field. Depending on the direction of the electric field, two different metastable ferroelectric (and piezoelectric) phases have been found. One of them corresponds to the experimentally confirmed phase, whereas the other is an optimally polarized phase. The structural details of these phases have been determined as a function of the electric field. The spontaneous polarization values of the phases are 14.5 and 20.5 μ C /cm2, respectively, and are relatively high among those of the existing organic ferroelectrics.

Capacitance-voltage measurement in memory devices using ferroelectric polymer

NASA Astrophysics Data System (ADS)

Nguyen, Chien A.; Lee, Pooi See

2006-01-01

Application of thin polymer film as storing mean for non-volatile memory devices is investigated. Capacitance-voltage (C-V) measurement of metal-ferroelectric-metal device using ferroelectric copolymer P(VDF-TrFE) as dielectric layer shows stable 'butter-fly' curve. The two peaks in C-V measurement corresponding to the largest capacitance are coincidental at the coercive voltages that give rise to zero polarization in the polarization hysteresis measurement. By comparing data of C-V and P-E measurement, a correlation between two types of hysteresis is established in which it reveals simultaneous electrical processes occurring inside the device. These processes are caused by the response of irreversible and reversible polarization to the applied electric field that can be used to present a memory window. The memory effect of ferroelectric copolymer is further demonstrated for fabricating polymeric non-volatile memory devices using metal-ferroelectric-insulator-semiconductor structure (MFIS). By applying different sweeping voltages at the gate, bidirectional flat-band voltage shift is observed in the ferroelectric capacitor. The asymmetrical shift after negative sweeping is resulted from charge accumulation at the surface of Si substrate caused by the dipole direction in the polymer layer. The effect is reversed for positive voltage sweeping.

Ferroelectric field-effect transistors based on solution-processed electrochemically exfoliated graphene

NASA Astrophysics Data System (ADS)

Heidler, Jonas; Yang, Sheng; Feng, Xinliang; Müllen, Klaus; Asadi, Kamal

2018-06-01

Memories based on graphene that could be mass produced using low-cost methods have not yet received much attention. Here we demonstrate graphene ferroelectric (dual-gate) field effect transistors. The graphene has been obtained using electrochemical exfoliation of graphite. Field-effect transistors are realized using a monolayer of graphene flakes deposited by the Langmuir-Blodgett protocol. Ferroelectric field effect transistor memories are realized using a random ferroelectric copolymer poly(vinylidenefluoride-co-trifluoroethylene) in a top gated geometry. The memory transistors reveal ambipolar behaviour with both electron and hole accumulation channels. We show that the non-ferroelectric bottom gate can be advantageously used to tune the on/off ratio.

Graphene-ferroelectric metadevices for nonvolatile memory and reconfigurable logic-gate operations.

PubMed

Kim, Woo Young; Kim, Hyeon-Don; Kim, Teun-Teun; Park, Hyun-Sung; Lee, Kanghee; Choi, Hyun Joo; Lee, Seung Hoon; Son, Jaehyeon; Park, Namkyoo; Min, Bumki

2016-01-27

Memory metamaterials are artificial media that sustain transformed electromagnetic properties without persistent external stimuli. Previous memory metamaterials were realized with phase-change materials, such as vanadium dioxide or chalcogenide glasses, which exhibit memory behaviour with respect to electrically/optically induced thermal stimuli. However, they require a thermally isolated environment for longer retention or strong optical pump for phase-change. Here we demonstrate electrically programmable nonvolatile memory metadevices realised by the hybridization of graphene, a ferroelectric and meta-atoms/meta-molecules, and extend the concept further to establish reconfigurable logic-gate metadevices. For a memory metadevice having a single electrical input, amplitude, phase and even the polarization multi-states were clearly distinguishable with a retention time of over 10 years at room temperature. Furthermore, logic-gate functionalities were demonstrated with reconfigurable logic-gate metadevices having two electrical inputs, with each connected to separate ferroelectric layers that act as the multi-level controller for the doping level of the sandwiched graphene layer.

A strong electro-optically active lead-free ferroelectric integrated on silicon

NASA Astrophysics Data System (ADS)

Abel, Stefan; Stöferle, Thilo; Marchiori, Chiara; Rossel, Christophe; Rossell, Marta D.; Erni, Rolf; Caimi, Daniele; Sousa, Marilyne; Chelnokov, Alexei; Offrein, Bert J.; Fompeyrine, Jean

2013-04-01

The development of silicon photonics could greatly benefit from the linear electro-optical properties, absent in bulk silicon, of ferroelectric oxides, as a novel way to seamlessly connect the electrical and optical domain. Of all oxides, barium titanate exhibits one of the largest linear electro-optical coefficients, which has however not yet been explored for thin films on silicon. Here we report on the electro-optical properties of thin barium titanate films epitaxially grown on silicon substrates. We extract a large effective Pockels coefficient of reff=148 pm V-1, which is five times larger than in the current standard material for electro-optical devices, lithium niobate. We also reveal the tensor nature of the electro-optical properties, as necessary for properly designing future devices, and furthermore unambiguously demonstrate the presence of ferroelectricity. The integration of electro-optical active films on silicon could pave the way towards power-efficient, ultra-compact integrated devices, such as modulators, tuning elements and bistable switches.

Enlarging photovoltaic effect: combination of classic photoelectric and ferroelectric photovoltaic effects

PubMed Central

Zhang, Jingjiao; Su, Xiaodong; Shen, Mingrong; Dai, Zhihua; Zhang, Lingjun; He, Xiyun; Cheng, Wenxiu; Cao, Mengyu; Zou, Guifu

2013-01-01

Converting light energy to electrical energy in photovoltaic devices relies on the photogenerated electrons and holes separated by the built-in potential in semiconductors. Photo-excited electrons in metal electrodes are usually not considered in this process. Here, we report an enhanced photovoltaic effect in the ferroelectric lanthanum-modified lead zirconate titanate (PLZT) by using low work function metals as the electrodes. We believe that electrons in the metal with low work function could be photo-emitted into PLZT and form the dominant photocurrent in our devices. Under AM1.5 (100 mW/cm2) illumination, the short-circuit current and open-circuit voltage of Mg/PLZT/ITO are about 150 and 2 times of those of Pt/PLZT/ITO, respectively. The photovoltaic response of PLZT capacitor was expanded from ultraviolet to visible spectra, and it may have important impact on design and fabrication of high performance photovoltaic devices based on ferroelectric materials. PMID:23811832

Graphene-ferroelectric metadevices for nonvolatile memory and reconfigurable logic-gate operations

NASA Astrophysics Data System (ADS)

Kim, Woo Young; Kim, Hyeon-Don; Kim, Teun-Teun; Park, Hyun-Sung; Lee, Kanghee; Choi, Hyun Joo; Lee, Seung Hoon; Son, Jaehyeon; Park, Namkyoo; Min, Bumki

2016-01-01

Memory metamaterials are artificial media that sustain transformed electromagnetic properties without persistent external stimuli. Previous memory metamaterials were realized with phase-change materials, such as vanadium dioxide or chalcogenide glasses, which exhibit memory behaviour with respect to electrically/optically induced thermal stimuli. However, they require a thermally isolated environment for longer retention or strong optical pump for phase-change. Here we demonstrate electrically programmable nonvolatile memory metadevices realised by the hybridization of graphene, a ferroelectric and meta-atoms/meta-molecules, and extend the concept further to establish reconfigurable logic-gate metadevices. For a memory metadevice having a single electrical input, amplitude, phase and even the polarization multi-states were clearly distinguishable with a retention time of over 10 years at room temperature. Furthermore, logic-gate functionalities were demonstrated with reconfigurable logic-gate metadevices having two electrical inputs, with each connected to separate ferroelectric layers that act as the multi-level controller for the doping level of the sandwiched graphene layer.

Enlarging photovoltaic effect: combination of classic photoelectric and ferroelectric photovoltaic effects.

PubMed

Zhang, Jingjiao; Su, Xiaodong; Shen, Mingrong; Dai, Zhihua; Zhang, Lingjun; He, Xiyun; Cheng, Wenxiu; Cao, Mengyu; Zou, Guifu

2013-01-01

Converting light energy to electrical energy in photovoltaic devices relies on the photogenerated electrons and holes separated by the built-in potential in semiconductors. Photo-excited electrons in metal electrodes are usually not considered in this process. Here, we report an enhanced photovoltaic effect in the ferroelectric lanthanum-modified lead zirconate titanate (PLZT) by using low work function metals as the electrodes. We believe that electrons in the metal with low work function could be photo-emitted into PLZT and form the dominant photocurrent in our devices. Under AM1.5 (100 mW/cm²) illumination, the short-circuit current and open-circuit voltage of Mg/PLZT/ITO are about 150 and 2 times of those of Pt/PLZT/ITO, respectively. The photovoltaic response of PLZT capacitor was expanded from ultraviolet to visible spectra, and it may have important impact on design and fabrication of high performance photovoltaic devices based on ferroelectric materials.

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.

Ferroelectric Fluid Flow Control Valve

NASA Technical Reports Server (NTRS)