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. ).

Design and development of a ferroelectric micro photo detector for the bionic eye

NASA Astrophysics Data System (ADS)

Song, Yang

Driven by no effective therapy for Retinitis Pigmentosa and Age Related Macular Degeneration, artificial vision through the development of an artificial retina that can be implanted into the human eye, is being addressed by the Bionic Eye. This dissertation focuses on the study of a photoferroelectric micro photo detector as an implantable retinal prosthesis for vision restoration in patients with above disorders. This implant uses an electrical signal to trigger the appropriate ocular cells of the vision system without resorting to wiring or electrode implantation. The research work includes fabrication of photoferroelectric thin film micro detectors, characterization of these photoferroelectric micro devices as photovoltaic cells, and Finite Element Method (FEM) modeling of the photoferroelectrics and their device-neuron interface. A ferroelectric micro detector exhibiting the photovoltaic effect (PVE) directly adds electrical potential to the neuron membrane outer wall at the focal adhesion regions. The electrical potential then generates a retinal cell membrane potential deflection through a newly developed Direct-Electric-Field-Coupling (DEFC) model. This model is quite different from the traditional electric current model because instead of current directly working on the cell membrane, the PVE current is used to generate a localized high electric potential in the focal adhesion region by working together with the anisotropic high internal impedance of ferroelectric thin films. General electrodes and silicon photodetectors do not have such anisotropy and high impedance, and thus they cannot generate DEFC. This mechanism investigation is very valuable, because it clearly shows that our artificial retina works in a way that is totally different from the traditional current stimulation methods.

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

Pressure effects on the magnetoelectric properties of a multiferroic triangular-lattice antiferromagnet CuCrO2

NASA Astrophysics Data System (ADS)

Aoyama, Takuya; Miyake, Atsushi; Kagayama, Tomoko; Shimizu, Katsuya; Kimura, Tsuyoshi

2013-03-01

Effects of high pressure exceeding 10 GPa on spin-driven ferroelectricity were investigated for a multiferroic, triangular-lattice antiferromagnet (TLA), CuCrO2. For this purpose, we developed a system which enables us to measure ferroelectric polarization under a pressure of 10 GPa by using a diamond anvil cell. We found that the magnetic transition temperature accompanying the ferroelectric one in CuCrO2 was remarkably enhanced by applying pressure. The result is simply explained by considering the pressure-induced enhancement of inter- and/or intralayer magnetic interaction due to the compression of the lattice. In addition, the coercive electric field for the polarization reversal was also increased with increasing pressure, while the amplitude of the ferroelectric polarization was steeply suppressed at around 8 GPa. A possible origin of the observed pressure effects on the ferroelectric property in the multiferroic TLA is discussed in terms of a ferroelectric-antiferroelectric transition and structural domain rearrangement by uniaxial stress.

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.

Optical second-harmonic-generation probe of two-dimensional ferroelectricity.

PubMed

Aktsipetrov, O A; Misuryaev, T V; Murzina, T V; Blinov, L M; Fridkin, V M; Palto, S P

2000-03-15

Optical second-harmonic generation (SHG) is used as a noninvasive probe of two-dimensional (2D) ferroelectricity in Langmuir-Blodgett (LB) films of the copolymer vinylidene fluoride with trifluoroethylene. The surface 2D ferroelectric-paraelectric phase transition in the topmost layer of the LB films and a thickness-independent (almost 2D) transition in the bulk of these films are observed in temperature studies of SHG.

Flexible, ferroelectric nanoparticle doped polymer dispersed liquid crystal devices for lower switching voltage and nanoenergy generation

NASA Astrophysics Data System (ADS)

Nimmy John, V.; Varanakkottu, Subramanyan Namboodiri; Varghese, Soney

2018-06-01

Flexible polymer dispersed liquid crystal (F-PDLC) devices were fabricated using transparent conducting ITO/PET film. Polymerization induced phase separation (PIPS) method was used for pure and ferroelectric BaTiO3 (BTO) and ZnO doped PDLC devices. The distribution of nanoparticles in the PDLC and the formation of micro cavities were studied using field emission scanning electron microscopy (FESEM). It was observed that the addition of ferroelectric BTO nanoparticles has reduced the threshold voltage (Vth) and saturation voltage (Vsat) of FNP-PDLC by 85% and 41% respectively due to the spontaneous polarization of ferroelectric nanoparticles. The ferroelectric properties of BTO and ZnO in the fabricated devices were investigated using dynamic contact electrostatic force microscopy (DC EFM). Flexing the device can generate a potential due to the piezo-tribo electric effect of the ferroelectric nanomaterial doped in the PDLC matrix, which could be utilized as an energy generating system. The switching voltage after multiple flexing was also studied and found to be in par with non-flexing situations.

Finite-size effects of hysteretic dynamics in multilayer graphene on a ferroelectric

DOE PAGES

Morozovska, Anna N.; Pusenkova, Anastasiia S.; Varenyk, Oleksandr V.; ...

2015-06-11

The origin and influence of finite-size effects on the nonlinear dynamics of space charge stored by multilayer graphene on a ferroelectric and resistivity of graphene channel were analyzed. In this paper, we develop a self-consistent approach combining the solution of electrostatic problems with the nonlinear Landau-Khalatnikov equations for a ferroelectric. The size-dependent behaviors are governed by the relations between the thicknesses of multilayer graphene, ferroelectric film, and the dielectric layer. The appearance of charge and electroresistance hysteresis loops and their versatility stem from the interplay of polarization reversal dynamics and its incomplete screening in an alternating electric field. These featuresmore » are mostly determined by the dielectric layer thickness. The derived analytical expressions for electric fields and space-charge-density distribution in a multilayer system enable knowledge-driven design of graphene-on-ferroelectric heterostructures with advanced performance. We further investigate the effects of spatially nonuniform ferroelectric domain structures on the graphene layers’ conductivity and predict its dramatic increase under the transition from multi- to single-domain state in a ferroelectric. Finally, this intriguing effect can open possibilities for the graphene-based sensors and explore the underlying physical mechanisms in the operation of graphene field-effect transistor with ferroelectric gating.« less

Toroidal ferroelectricity in PbTiO3 nanoparticles.

PubMed

Stachiotti, M G; Sepliarsky, M

2011-04-01

We report from first-principles-based atomistic simulations that ferroelectricity can be sustained in PbTiO(3) nanoparticles of only a few lattice constants in size as a result of a toroidal ordering. We find that size-induced topological transformations lead to the stabilization of a ferroelectric bubble by the alignment of vortex cores along a closed path. These transformations, which are driven by the aspect ratio of the nanostructure, change the topology of the polarization field, producing a rich variety of polar configurations. For sufficiently flat nanostructures, a multibubble state bridges the gap between 0D nanodots and 2D ultrathin films. The thermal properties of the ferroelectric bubbles indicate that this state is suitable for the development of nanometric devices. © 2011 American Physical Society

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 fundamental side, ab initio approaches can be used to explore new mechanisms for ferroelectricity by exploiting electronic correlations that are at play in transition metal oxides, and by suggesting ways to maximize the strength of these effects as well as the corresponding ordering temperatures.

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

Orbital-ordering-driven multiferroicity and magnetoelectric coupling in GeV₄S₈.

PubMed

Singh, Kiran; Simon, Charles; Cannuccia, Elena; Lepetit, Marie-Bernadette; Corraze, Benoit; Janod, Etienne; Cario, Laurent

2014-09-26

We report here the discovery of multiferroicity and large magnetoelectric coupling in the type I orbital order system GeV₄S₈. Our study demonstrates that this clustered compound displays a para-ferroelectric transition at 32 K. This transition originates from an orbital ordering which reorganizes the charge within the transition metal clusters. Below the antiferromagnetic transition at 17 K, the application of a magnetic field significantly affects the ferroelectric polarization, revealing thus a large magnetoelectric coupling. Our study suggests that the application of a magnetic field induces a metamagnetic transition which significantly affects the ferroelectric polarization thanks to an exchange striction phenomenon.

Ferroelectric Fluid Flow Control Valve

NASA Technical Reports Server (NTRS)

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

1999-01-01

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

Mixed electrochemical–ferroelectric states in nanoscale ferroelectrics

DOE PAGES

Yang, Sang Mo; Morozovska, Anna N.; Kumar, Rajeev; ...

2017-05-01

Ferroelectricity on the nanoscale has been the subject of much fascination in condensed-matter physics for over half a century. In recent years, multiple reports claiming ferroelectricity in ultrathin ferroelectric films based on the formation of remnant polarization states, local electromechanical hysteresis loops, and pressure-induced switching were made. But, similar phenomena were reported for traditionally non-ferroelectric materials, creating a significant level of uncertainty in the field. We show that in nanoscale systems the ferroelectric state is fundamentally inseparable from the electrochemical state of the surface, leading to the emergence of a mixed electrochemical–ferroelectric state. We explore the nature, thermodynamics, and thicknessmore » evolution of such states, and demonstrate the experimental pathway to establish its presence. Our analysis reconciles multiple prior studies, provides guidelines for studies of ferroelectric materials on the nanoscale, and establishes the design paradigm for new generations of ferroelectric-based devices.« less

Magnetic structures and excitations in a multiferroic Y-type hexaferrite BaSrCo 2 Fe 11 AlO 22

DOE PAGES

Nakajima, Taro; Tokunaga, Yusuke; Matsuda, Masaaki; ...

2016-11-30

Here, we have investigated magnetic orders and excitations in a Y-type hexaferrite BaSrCo 2Fe 11AlO 22 (BSCoFAO), which was reported to exhibit spin-driven ferroelectricity at room temperature. By means of magnetization, electric polarization, and neutron-diffraction measurements using single-crystal samples, we establish a H-T magnetic phase diagram for magnetic field perpendicular to the c axis (H ⟂c). This system exhibits an alternating longitudinal conical (ALC) magnetic structure in the ground state, and it turns into a non-co-planar commensurate magnetic order with spin-driven ferroelectricity under H ⟂c. The field-induced ferroelectric phase remains as a metastable state after removing magnetic field below 250more » K. This metastability is the key to understanding of magnetic field reversal of the spin-driven electric polarization in this system. Inelastic polarized neutron-scattering measurements in the ALC phase reveal a magnetic excitation at around 7.5 meV, which is attributed to spin components oscillating in a plane perpendicular to the cone axis. This phasonlike excitation is expected to be an electric-field active magnon, i.e., electromagnon excitation, in terms of the magnetostriction mechanism.« less

Magnetic structures and excitations in a multiferroic Y-type hexaferrite BaSrCo2Fe11AlO22

NASA Astrophysics Data System (ADS)

Nakajima, Taro; Tokunaga, Yusuke; Matsuda, Masaaki; Dissanayake, Sachith; Fernandez-Baca, Jaime; Kakurai, Kazuhisa; Taguchi, Yasujiro; Tokura, Yoshinori; Arima, Taka-hisa

2016-11-01

We have investigated magnetic orders and excitations in a Y-type hexaferrite BaSrCo2Fe11AlO22 (BSCoFAO), which was reported to exhibit spin-driven ferroelectricity at room temperature [S. Hirose, K. Haruki, A. Ando, and T. Kimura, Appl. Phys. Lett. 104, 022907 (2014), 10.1063/1.4862432]. By means of magnetization, electric polarization, and neutron-diffraction measurements using single-crystal samples, we establish a H -T magnetic phase diagram for magnetic field perpendicular to the c axis (H⊥c). This system exhibits an alternating longitudinal conical (ALC) magnetic structure in the ground state, and it turns into a non-co-planar commensurate magnetic order with spin-driven ferroelectricity under H⊥c. The field-induced ferroelectric phase remains as a metastable state after removing magnetic field below ˜250 K. This metastability is the key to understanding of magnetic field reversal of the spin-driven electric polarization in this system. Inelastic polarized neutron-scattering measurements in the ALC phase reveal a magnetic excitation at around 7.5 meV, which is attributed to spin components oscillating in a plane perpendicular to the cone axis. This phasonlike excitation is expected to be an electric-field active magnon, i.e., electromagnon excitation, in terms of the magnetostriction mechanism.

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.

Spin-lattice-coupling-mediated magnetoferroelectric phase transition induced by uniaxial pressure in multiferroic CuFe1 -xMxO2 (M =Ga , Al)

NASA Astrophysics Data System (ADS)

Tamatsukuri, Hiromu; Mitsuda, Setsuo; Nakamura, Tenfu; Takata, Kouhei; Nakajima, Taro; Prokes, Karel; Yokaichiya, Fabiano; Kiefer, Klaus

2017-05-01

We have investigated magnetic and ferroelectric (dielectric) properties of multiferroic CuFe0.982Ga0.018O2 , CuFe0.965Ga0.035O2 , and CuFe0.95Al0.05O2 under applied uniaxial pressure p up to 600 MPa. Unlike the results of the almost same experiments on CuFeO2 [Tamatsukuri et al., Phys. Rev. B 94, 174402 (2016), 10.1103/PhysRevB.94.174402], we have found that the application of p induces a new ferroelectric phase, which is different from the well-studied spin-driven ferroelectric phase with helical magnetic ordering, in all the doped samples investigated here. We have also constructed the temperature versus p magnetoelectric phase diagrams of the three samples. The ferroelectric polarization in the p -induced ferroelectric phase lies along the [110] direction as in the helical magnetoferroelectric phase, and its value is comparable with or larger than that in the helical magnetoferroelectric phase. The magnetic structure in the p -induced ferroelectric phase seems to be of a collinear sinusoidal type. Although this magnetic structure itself does not break the inversion symmetry, it is considered to play an important role in the origin of ferroelectricity in the p -induced ferroelectric phase through the spin-lattice coupling in this system.

Giant Magnetoelectric Energy Conversion Utilizing Inter-Ferroelectric Phase Transformations in Ferroics

NASA Astrophysics Data System (ADS)

Finkel, Peter; Staruch, Margo

Phase transition-based electromechanical transduction permits achieving a non-resonant broadband mechanical energy conversion see (Finkel et al Actuators, 5 [1] 2. (2015)) , the idea is based on generation high energy density per cycle , at least 100x of magnitude larger than linear piezoelectric type generators in stress biased [011]cut relaxor ferroelectric Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 (PIN-PMN-PT) single crystal can generate reversible strain >0.35% at remarkably low fields (0.1 MV/m) for tens of millions of cycles. Recently we demonstrated that large strain and polarization rotation can be generated for over 40 x 106cycles with little fatigue by realization of reversible ferroelectric-ferroelectric phase transition in [011] cut PIN-PMN-PT relaxor ferroelectric single crystal while sweeping through the transition with a low applied electric field <0.18 MV/m under mechanical stress. This methodology was extended in the present work to propose magnetoelectric (ME) composite hybrid system comprised of highly magnetostrictive alloymFe81.4Ga18.6 (Galfenol), and lead indium niobate-lead magnesium niobate-lead titanate (PIN-PMN-PT) domain engineered relaxor ferroelectric single crystal. A small time-varying magnetic field applied to this system causes the magnetostrictive element to expand, and the resulting stress forces the phase change in the relaxor ferroelectric single crystal. ME coupling coefficient was fond to achieve 80 V/cm Oe near the FR-FO phase transition that is at least 100X of magnitude higher than any currently reported values.

Generation and Reduction of NOx on Air-Fed Ozonizers

NASA Astrophysics Data System (ADS)

Ehara, Yoshiyasu; Amemiya, Yusuke; Yamamoto, Toshiaki

A generation and reduction of NOx on air-fed ozonizers using a ferroelectric packed bed reactor have been experimentally investigated. The reactors packed with CaTiO3, SrTiO3 and BaTiO3 pellets are examined for ozone generation. An ac voltage is applied to the reactor to generate partial discharge. Ozone concentration and the different nitrogen oxides at downstream of the packed bed reactor were measured with UV absorption ozone monitor and a Fourier transform infrared spectroscope respectively. The dielectric constant of packed ferroelectric pellets influences the discharge characteristic, ozone and NOx generations are varied by the dielectric constant value. Focusing on a discharge pulse current and maximum discharge magnitude, the ferroelectric packed bed plasma reactors have been evaluated on nitrogen oxide and ozone generated concentrations.

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

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.

Computational Simulation of Explosively Generated Pulsed Power Devices

DTIC Science & Technology

2013-03-21

to practical applications. These are the magnetic flux compression generators (FCG), ferromagnetic generators (FMG) and ferroelectric generators (FEG...The first device works on the concept of field interaction between a conducting medium and a magnetic field. The last two devices make use of either... magnetic or electric fields stored in a prepared material (4). This research will focus on the ferroelectric generator as a high voltage source for

Prediction of two-dimensional electron gas mediated magnetoelectric coupling at ferroelectric PbTiO3/SrTiO3 heterostructures

NASA Astrophysics Data System (ADS)

Wei, Lan-ying; Lian, Chao; Meng, Sheng

2017-05-01

First-principles calculations predict the emergence of magnetoelectric coupling mediated by two-dimensional electron gas (2DEG) at the ferroelectric PbTiO3/SrTiO3 heterostructure. Free electrons endowed by naturally existing oxygen vacancies in SrTiO3 are driven to the heterostructure interface under the polarizing field of ferroelectric PbTiO3 to form a 2DEG. The electrons are captured by interfacial Ti atoms, which surprisingly exhibits ferromagnetism even at room temperature with a small critical density of ˜15.5 μ C /cm2 . The ferroelectricity-controlled ferromagnetism mediated by interfacial 2DEG shows strong magnetoelectric coupling strength, enabling convenient control of magnetism by electric field and vice versa. The PbTiO3/SrTiO3 heterostructure is cheap, easily grown, and controllable, promising future applications in low-cost spintronics and information storage at ambient condition.

The role of ferroelectric domain structure in second harmonic generation in random quadratic media.

PubMed

Roppo, Vito; Wang, W; Kalinowski, K; Kong, Y; Cojocaru, C; Trull, J; Vilaseca, R; Scalora, M; Krolikowski, W; Kivshar, Yu

2010-03-01

We study theoretically and numerically the second harmonic generation in a nonlinear crystal with random distribution of ferroelectric domains. We show that the specific features of disordered domain structure greatly affect the emission pattern of the generated harmonics. This phenomena can be used to characterize the degree of disorder in nonlinear photonic structures.

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.

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

Local Atomic Structure Deviation from Average Structure of Na0.5Bi0.5TiO3: Combined X-ray and Neutron Total Scattering Study

DTIC Science & Technology

2013-03-27

part of a new generation of ferroelectric materials used in a multitude of piezoelectric applications. This work examines the short and long range...2211 15. SUBJECT TERMS Na0.5Bi0.5TiO3, ferroelectric , structure, Rietveld, local structure Elena Aksel, Jennifer S. Forrester, Juan C. Nino, Katharine...a new generation of ferroelectric materials used in a multitude of piezoelectric applications. This work examines the short and long range structure

Giant Spin-Driven Ferroelectric Polarization in BiFeO 3 at Room Temperature

DOE PAGES

Lee, Jun Hee; Fishman, Randy S.

2015-11-11

Although BiFeO 3 is the most extensively investigated multiferroic material, its magnetoelectic couplings are barely understood. Here we report a thorough study of the magentoelectric (ME) couplings in spin-cycloidal buk BiFeO 3 using first-principles calculations and microscopic spin-wave models compared with neutron-scattering measurements. We find that huge exchange-striction (ES) polarizations, i.e. the electric response of the magnetic exchange through ferroelectric and antiferrodistortive distortions, is giant enough to dominate over all other ME couplings. We show that BiFeO 3 has a hidden record-high spin-driven polarization ( 3 C/cm 2) at room-temperature. The huge ES polarizations can be tuned by coupling tomore » the antiferrodistortive rotations.« less

Electric-field-driven magnetization reversal in square-shaped nanomagnet-based multiferroic heterostructure

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

Peng, Ren-Ci; Nan, Ce-Wen, E-mail: jzw12@psu.edu, E-mail: cwnan@tsinghua.edu.cn; Wang, J. J., E-mail: jzw12@psu.edu, E-mail: cwnan@tsinghua.edu.cn

Based on phase field modeling and thermodynamic analysis, purely electric-field-driven magnetization reversal was shown to be possible in a multiferroic heterostructure of a square-shaped amorphous Co{sub 40}Fe{sub 40}B{sub 20} nanomagnet on top of a ferroelectric layer through electrostrain. The reversal is made possible by engineering the mutual interactions among the built-in uniaxial magnetic anisotropy, the geometry-dependent magnetic configuration anisotropy, and the magnetoelastic anisotropy. Particularly, the incorporation of the built-in uniaxial anisotropy made it possible to reverse magnetization with one single unipolar electrostrain pulse, which is simpler than previous designs involving the use of bipolar electrostrains and may alleviate ferroelectric fatigue.more » Critical conditions for triggering the magnetization reversal are identified.« less

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.

Power supply

DOEpatents

Hart, Edward J.; Leeman, James E.; MacDougall, Hugh R.; Marron, John J.; Smith, Calvin C.

1976-01-01

An electric power supply employs a striking means to initiate ferroelectric elements which provide electrical energy output which subsequently initiates an explosive charge which initiates a second ferroelectric current generator to deliver current to the coil of a magnetic field current generator, creating a magnetic field around the coil. Continued detonation effects compression of the magnetic field and subsequent generation and delivery of a large output current to appropriate output loads.

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.

Tunneling magnetoresistance and electroresistance in Fe/PbTiO{sub 3}/Fe multiferroic tunnel junctions

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

Dai, Jian-Qing, E-mail: djqkust@sina.com

We perform first-principles electronic structure and spin-dependent transport calculations for a Fe/PbTiO{sub 3}/Fe multiferroic tunnel junction with asymmetric TiO{sub 2}- and PbO-terminated interfaces. We demonstrate that the interfacial electronic reconstruction driven by the in situ screening of ferroelectric polarization, in conjunction with the intricate complex band structure of barrier, play a decisive role in controlling the spin-dependent tunneling. Reversal of ferroelectric polarization results in a transition from insulating to half-metal-like conducting state for the interfacial Pb 6p{sub z} orbitals, which acts as an atomic-scale spin-valve by releasing the tunneling current in antiparallel magnetization configuration as the ferroelectric polarization pointing tomore » the PbO-terminated interface. This effect produces large change in tunneling conductance. Our results open an attractive avenue in designing multiferroic tunnel junctions with excellent performance by exploiting the interfacial electronic reconstruction originated from the in situ screening of ferroelectric polarization.« less

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).

Polarization-induced transport in organic field-effect transistors: the role of ferroelectric dielectrics

NASA Astrophysics Data System (ADS)

Guha, Suchismita; Laudari, Amrit

2017-08-01

The ferroelectric nature of polymer ferroelectrics such as poly(vinylidene fluoride) (PVDF) has been known for over 45 years. However, its role in interfacial transport in organic/polymeric field-effect transistors (FETs) is not that well understood. Dielectrics based on PVDF and its copolymers are a perfect test-bed for conducting transport studies where a systematic tuning of the dielectric constant with temperature may be achieved. The charge transport mechanism in an organic semiconductor often occurs at the intersection of band-like coherent motion and incoherent hopping through localized states. By choosing two small molecule organic semiconductors - pentacene and 6,13 bis(triisopropylsilylethynyl)pentacene (TIPS-pentacene) - along with a copolymer of PVDF (PVDF-TrFe) as the dielectric layer, the transistor characteristics are monitored as a function of temperature. A negative coefficient of carrier mobility is observed in TIPS-pentacene upwards of 200 K with the ferroelectric dielectric. In contrast, TIPS-pentacene FETs show an activated transport with non-ferroelectric dielectrics. Pentacene FETs, on the other hand, show a weak temperature dependence of the charge carrier mobility in the ferroelectric phase of PVDF-TrFE, which is attributed to polarization fluctuation driven transport resulting from a coupling of the charge carriers to the surface phonons of the dielectric layer. Further, we show that there is a strong correlation between the nature of traps in the organic semiconductor and interfacial transport in organic FETs, especially in the presence of a ferroelectric dielectric.

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.

Impact induced depolarization of ferroelectric materials

NASA Astrophysics Data System (ADS)

Agrawal, Vinamra; Bhattacharya, Kaushik

2018-06-01

We study the large deformation dynamic behavior and the associated nonlinear electro-thermo-mechanical coupling exhibited by ferroelectric materials in adiabatic environments. This is motivated by a ferroelectric generator which involves pulsed power generation by loading the ferroelectric material with a shock, either by impact or a blast. Upon impact, a shock wave travels through the material inducing a ferroelectric to nonpolar phase transition giving rise to a large voltage difference in an open circuit situation or a large current in a closed circuit situation. In the first part of this paper, we provide a general continuum mechanical treatment of the situation assuming a sharp phase boundary that is possibly charged. We derive the governing laws, as well as the driving force acting on the phase boundary. In the second part, we use the derived equations and a particular constitutive relation that describes the ferroelectric to nonpolar phase transition to study a uniaxial plate impact problem. We develop a numerical method where the phase boundary is tracked but other discontinuities are captured using a finite volume method. We compare our results with experimental observations to find good agreement. Specifically, our model reproduces the observed exponential rise of charge as well as the resistance dependent Hugoniot. We conclude with a parameter study that provides detailed insight into various aspects of the problem.

Polarization induced optical and electrical control of 2D materials by ferroelectrics

NASA Astrophysics Data System (ADS)

Zafar, Zainab; You, Yumeng

Integration of 2D semiconductors with ferroelectrics can provide a route towards control of polarization-switching by piezoelectric effect, allowing the realization of exciting features of next-generation optoelectronic devices. However, a fundamental understanding of spectroscopic investigation based on ferroelectric switching in ferroelectric/2D heterostructures remains elusive. Here, we demonstrate mechanical writing of nanoscale domains in ferroelectric thin film coupled with 2D materials, facilitated by piezoresponse force microscope (PFM). We propose the use of typical Raman/PL imaging to predict the effect of phase change of ferroelectric on 2D materials. Mechanical writing not only controls the local doping region, but also tunes the transport properties of the channel, as confirmed by its electrical characterization. By Raman/PL spectroscopy, we have identified the domain pattern of different polarizations in terms of amplitude modification of thin ferroelectric and possible shifts in wavenumber/energy of the emission peaks of 2D materials. Therefore, the sensitivity of spectroscopic imaging well corroborates the efficacy of mechanical writing for synthesizing ferroelectric gated 2D devices. Southeast University.

Atomic-scale compensation phenomena at polar interfaces.

PubMed

Chisholm, Matthew F; Luo, Weidong; Oxley, Mark P; Pantelides, Sokrates T; Lee, Ho Nyung

2010-11-05

The interfacial screening charge that arises to compensate electric fields of dielectric or ferroelectric thin films is now recognized as the most important factor in determining the capacitance or polarization of ultrathin ferroelectrics. Here we investigate using aberration-corrected electron microscopy and density-functional theory to show how interfaces cope with the need to terminate ferroelectric polarization. In one case, we show evidence for ionic screening, which has been predicted by theory but never observed. For a ferroelectric film on an insulating substrate, we found that compensation can be mediated by an interfacial charge generated, for example, by oxygen vacancies.

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.

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.

Relaxor ferroelectricity and electric-field-driven structural transformation in the giant lead-free piezoelectric (Ba ,Ca ) (Ti ,Zr ) O3

NASA Astrophysics Data System (ADS)

Brajesh, Kumar; Tanwar, Khagesh; Abebe, Mulualem; Ranjan, Rajeev

2015-12-01

There is great interest in lead-free (B a0.85C a0.15 ) (T i0.90Z r0.10 ) O3 (15/10BCTZ) because of its exceptionally large piezoelectric response [Liu and Ren, Phys. Rev. Lett. 103, 257602 (2009), 10.1103/PhysRevLett.103.257602]. In this paper, we have analyzed the nature of: (i) crystallographic phase coexistence at room temperature, (ii) temperature- and field-induced phase transformation to throw light on the atomistic mechanisms associated with the large piezoelectric response of this system. A detailed temperature-dependent dielectric and lattice thermal expansion study proved that the system exhibits a weak dielectric relaxation, characteristic of a relaxor ferroelectric material on the verge of exhibiting a normal ferroelectric-paraelectric transformation. Careful structural analysis revealed that a ferroelectric state at room temperature is composed of three phase coexistences, tetragonal (P 4 m m )+ orthorhombic(Amm 2 )+rhombohedral(R 3 m ) . We also demonstrate that the giant piezoresponse is associated with a significant fraction of the tetragonal phase transforming to rhombohedral. It is argued that the polar nanoregions associated with relaxor ferroelectricity amplify the piezoresponse by providing an additional degree of intrinsic structural inhomogeneity to the system.

Engineering an Insulating Ferroelectric Superlattice with a Tunable Band Gap from Metallic Components

DOE PAGES

Ghosh, Saurabh; Borisevich, Albina Y.; Pantelides, Sokrates T.

2017-10-25

The recent discovery of “polar metals” with ferroelectriclike displacements offers the promise of designing ferroelectrics with tunable energy gaps by inducing controlled metal-insulator transitions. Here in this work, we employ first-principles calculations to design a metallic polar superlattice from nonpolar metal components and show that controlled intermixing can lead to a true insulating ferroelectric with a tunable band gap. We consider a 2/2 superlattice made of two centrosymmetric metallic oxides, La 0.75Sr 0.25MnO 3 and LaNiO 3, and show that ferroelectriclike displacements are induced. The ferroelectriclike distortion is found to be strongly dependent on the carrier concentration (Sr content). Further,more » we show that a metal-to-insulator (MI) transition is feasible in this system via disproportionation of the Ni sites. Such a disproportionation and, hence, a MI transition can be driven by intermixing of transition metal ions between Mn and Ni layers. Finally, as a result, the energy gap of the resulting ferroelectric can be tuned by varying the degree of intermixing in the experimental fabrication method.« less

Engineering an Insulating Ferroelectric Superlattice with a Tunable Band Gap from Metallic Components

NASA Astrophysics Data System (ADS)

Ghosh, Saurabh; Borisevich, Albina Y.; Pantelides, Sokrates T.

2017-10-01

The recent discovery of "polar metals" with ferroelectriclike displacements offers the promise of designing ferroelectrics with tunable energy gaps by inducing controlled metal-insulator transitions. Here we employ first-principles calculations to design a metallic polar superlattice from nonpolar metal components and show that controlled intermixing can lead to a true insulating ferroelectric with a tunable band gap. We consider a 2 /2 superlattice made of two centrosymmetric metallic oxides, La0.75 Sr0.25 MnO3 and LaNiO3 , and show that ferroelectriclike displacements are induced. The ferroelectriclike distortion is found to be strongly dependent on the carrier concentration (Sr content). Further, we show that a metal-to-insulator (MI) transition is feasible in this system via disproportionation of the Ni sites. Such a disproportionation and, hence, a MI transition can be driven by intermixing of transition metal ions between Mn and Ni layers. As a result, the energy gap of the resulting ferroelectric can be tuned by varying the degree of intermixing in the experimental fabrication method.

Engineering an Insulating Ferroelectric Superlattice with a Tunable Band Gap from Metallic Components

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

Ghosh, Saurabh; Borisevich, Albina Y.; Pantelides, Sokrates T.

The recent discovery of “polar metals” with ferroelectriclike displacements offers the promise of designing ferroelectrics with tunable energy gaps by inducing controlled metal-insulator transitions. Here in this work, we employ first-principles calculations to design a metallic polar superlattice from nonpolar metal components and show that controlled intermixing can lead to a true insulating ferroelectric with a tunable band gap. We consider a 2/2 superlattice made of two centrosymmetric metallic oxides, La 0.75Sr 0.25MnO 3 and LaNiO 3, and show that ferroelectriclike displacements are induced. The ferroelectriclike distortion is found to be strongly dependent on the carrier concentration (Sr content). Further,more » we show that a metal-to-insulator (MI) transition is feasible in this system via disproportionation of the Ni sites. Such a disproportionation and, hence, a MI transition can be driven by intermixing of transition metal ions between Mn and Ni layers. Finally, as a result, the energy gap of the resulting ferroelectric can be tuned by varying the degree of intermixing in the experimental fabrication method.« less

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.

Antiferroelectric Nature of CH3NH3PbI3-xClx Perovskite and Its Implication for Charge Separation in Perovskite Solar Cells

NASA Astrophysics Data System (ADS)

Sewvandi, Galhenage A.; Kodera, Kei; Ma, Hao; Nakanishi, Shunsuke; Feng, Qi

2016-07-01

Perovskite solar cells (PSCs) have been attracted scientific interest due to high performance. Some researchers have suggested anomalous behavior of PSCs to the polarizations due to the ion migration or ferroelectric behavior. Experimental results and theoretical calculations have suggested the possibility of ferroelectricity in organic-inorganic perovskite. However, still no studies have been concretely discarded the ferroelectric nature of perovskite absorbers in PSCs. Hysteresis of P-E (polarization-electric field) loops is an important evidence to confirm the ferroelectricity. In this study, P-E loop measurements, in-depth structural study, analyses of dielectric behavior and the phase transitions of CH3NH3PbI3-xClx perovskite were carried out and investigated. The results suggest that CH3NH3PbI3-xClx perovskite is in an antiferroelectric phase at room temperature. The antiferroelectric phase can be switched to ferroelectric phase by the poling treatment and exhibits ferroelectric-like hysteresis P-E loops and dielectric behavior around room temperature; namely, the perovskite can generate a ferroelectric polarization under PSCs operating conditions. Furthermore, we also discuss the implications of ferroelectric polarization on PSCs charge separation.

Antiferroelectric Nature of CH3NH3PbI3-xClx Perovskite and Its Implication for Charge Separation in Perovskite Solar Cells.

PubMed

Sewvandi, Galhenage A; Kodera, Kei; Ma, Hao; Nakanishi, Shunsuke; Feng, Qi

2016-07-29

Perovskite solar cells (PSCs) have been attracted scientific interest due to high performance. Some researchers have suggested anomalous behavior of PSCs to the polarizations due to the ion migration or ferroelectric behavior. Experimental results and theoretical calculations have suggested the possibility of ferroelectricity in organic-inorganic perovskite. However, still no studies have been concretely discarded the ferroelectric nature of perovskite absorbers in PSCs. Hysteresis of P-E (polarization-electric field) loops is an important evidence to confirm the ferroelectricity. In this study, P-E loop measurements, in-depth structural study, analyses of dielectric behavior and the phase transitions of CH3NH3PbI3-xClx perovskite were carried out and investigated. The results suggest that CH3NH3PbI3-xClx perovskite is in an antiferroelectric phase at room temperature. The antiferroelectric phase can be switched to ferroelectric phase by the poling treatment and exhibits ferroelectric-like hysteresis P-E loops and dielectric behavior around room temperature; namely, the perovskite can generate a ferroelectric polarization under PSCs operating conditions. Furthermore, we also discuss the implications of ferroelectric polarization on PSCs charge separation.

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.

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.

Frequency dependent polarisation switching in h-ErMnO3

NASA Astrophysics Data System (ADS)

Ruff, Alexander; Li, Ziyu; Loidl, Alois; Schaab, Jakob; Fiebig, Manfred; Cano, Andres; Yan, Zewu; Bourret, Edith; Glaum, Julia; Meier, Dennis; Krohns, Stephan

2018-04-01

We report an electric-field poling study of the geometrically-driven improper ferroelectric h-ErMnO3. From a detailed dielectric analysis, we deduce the temperature and the frequency dependent range for which single-crystalline h-ErMnO3 exhibits purely intrinsic dielectric behaviour, i.e., free from the extrinsic so-called Maxwell-Wagner polarisations that arise, for example, from surface barrier layers. In this regime, ferroelectric hysteresis loops as a function of frequency, temperature, and applied electric fields are measured, revealing the theoretically predicted saturation polarisation on the order of 5-6 μC/cm2. Special emphasis is put on frequency dependent polarisation switching, which is explained in terms of domain-wall movement similar to proper ferroelectrics. Controlling the domain walls via electric fields brings us an important step closer to their utilization in domain-wall-based electronics.

Spin-Chirality-Driven Ferroelectricity on a Perfect Triangular Lattice Antiferromagnet

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

Mitamura, H.; Watanuki, R.; Kaneko, Koji

Magnetic field (B) variation of the electrical polarization P c ( ∥c) of the perfect triangular lattice antiferromagnet RbFe(MoO 4) 2 is examined up to the saturation point of the magnetization for B⊥c. P c is observed only in phases for which chirality is predicted in the in-plane magnetic structures. No strong anomaly is observed in P c at the field at which the spin modulation along the c axis, and hence the spin helicity, exhibits a discontinuity to the commensurate state. These results indicate that the ferroelectricity in this compound originates predominantly from the spin chirality, the explanation ofmore » which would require a new mechanism for magnetoferroelectricity. Lastly, the obtained field-temperature phase diagrams of ferroelectricity well agree with those theoretically predicted for the spin chirality of a Heisenberg spin triangular lattice antiferromagnet.« less

Spin-Chirality-Driven Ferroelectricity on a Perfect Triangular Lattice Antiferromagnet

DOE PAGES

Mitamura, H.; Watanuki, R.; Kaneko, Koji; ...

2014-10-01

Magnetic field (B) variation of the electrical polarization P c ( ∥c) of the perfect triangular lattice antiferromagnet RbFe(MoO 4) 2 is examined up to the saturation point of the magnetization for B⊥c. P c is observed only in phases for which chirality is predicted in the in-plane magnetic structures. No strong anomaly is observed in P c at the field at which the spin modulation along the c axis, and hence the spin helicity, exhibits a discontinuity to the commensurate state. These results indicate that the ferroelectricity in this compound originates predominantly from the spin chirality, the explanation ofmore » which would require a new mechanism for magnetoferroelectricity. Lastly, the obtained field-temperature phase diagrams of ferroelectricity well agree with those theoretically predicted for the spin chirality of a Heisenberg spin triangular lattice antiferromagnet.« less

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)

Electron emission and plasma generation in a modulator electron gun using ferroelectric cathode

NASA Astrophysics Data System (ADS)

Chen, Shutao; Zheng, Shuxin; Zhu, Ziqiu; Dong, Xianlin; Tang, Chuanxiang

2006-10-01

Strong electron emission and dense plasma generation have been observed in a modulator electron gun with a Ba 0.67Sr 0.33TiO 3 ferroelectric cathode. Parameter of the modulator electron gun and lifetime of the ferroelectric cathode were investigated. It was shown that electron emission from Ba 0.67Sr 0.33TiO 3 cathode with a positive triggering pulse is a sort of plasma emission. Electrons were emitted by the co-effect of surface plasma and non-compensated negative polarization charges at the surface of the ferroelectric. The element analyses of the graphite collector after emission process was performed to show the ingredient of the plasma consist of Ba, Ti and Cu heavy cations of the ceramic compound and electrode. It was demonstrated the validity of the Child-Langmuir law by introducing the decrease of vacuum gap and increase of emission area caused by the expansion of the surface plasma.

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.

A Multiaxial Molecular Ferroelectric with Highest Curie Temperature and Fastest Polarization Switching.

PubMed

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

2017-10-04

The classical organic ferroelectric, poly(vinylidene fluoride) (PVDF), has attracted much attention as a promising candidate for data storage applications compatible with all-organic electronics. However, it is the low crystallinity, the large coercive field, and the limited thermal stability of remanent polarization that severely hinder large-scale integration. In light of that, we show a molecular ferroelectric thin film of [Hdabco][ReO 4 ] (dabco = 1,4-diazabicyclo[2.2.2]octane) (1), belonging to another class of typical organic ferroelectrics. Remarkably, it displays not only the highest Curie temperature of 499.6 K but also the fastest polarization switching of 100k Hz among all reported molecular ferroelectrics. Combined with the large remanent polarization values (∼9 μC/cm 2 ), the low coercive voltages (∼10 V), and the unique multiaxial ferroelectric nature, 1 becomes a promising and viable alternative to PVDF for data storage applications in next-generation flexible devices, wearable devices, and bionics.

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

Phase transitions and domain structures in multiferroics

NASA Astrophysics Data System (ADS)

Vlahos, Eftihia

2011-12-01

Thin film ferroelectrics and multiferroics are two important classes of materials interesting both from a scientific and a technological prospective. The volatility of lead and bismuth as well as environmental issues regarding the toxicity of lead are two disadvantages of the most commonly used ferroelectric random access memory (FeRAM) materials such as Pb(Zr,Ti)O3 and SrBi2Ta2O9. Therefore lead-free thin film ferroelectrics are promising substitutes as long as (a) they can be grown on technologically important substrates such as silicon, and (b) their T c and Pr become comparable to that of well established ferroelectrics. On the other hand, the development of functional room temperature ferroelectric ferromagnetic multiferroics could lead to very interesting phenomena such as control of magnetism with electric fields and control of electrical polarization with magnetic fields. This thesis focuses on the understanding of material structure-property relations using nonlinear optical spectroscopy. Nonlinear spectroscopy is an excellent tool for probing the onset of ferroelectricity, and domain dynamics in strained ferroelectrics and multiferroics. Second harmonic generation was used to detect ferroelectricity and the antiferrodistortive phase transition in thin film SrTiO3. Incipient ferroelectric CaTiO3 has been shown to become ferroelectric when strained with a combination of SHG and dielectric measurements. The tensorial nature of the induced nonlinear polarization allows for probing of the BaTiO3 and SrTiO3 polarization contributions in nanoscale BaTiO3/SrTiO3 superlattices. In addition, nonlinear optics was used to demonstrate ferroelectricity in multiferroic EuTiO3. Finally, confocal SHG and Raman microscopy were utilized to visualize polar domains in incipient ferroelectric and ferroelastic CaTiO3.

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 Nanophase Materials Sciences, sponsored at Oak Ridge National Laboratory by the Scientific User Facilities Division.

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.

Novel electronic ferroelectricity in an organic charge-order insulator investigated with terahertz-pump optical-probe spectroscopy

PubMed Central

Yamakawa, H.; Miyamoto, T.; Morimoto, T.; Yada, H.; Kinoshita, Y.; Sotome, M.; Kida, N.; Yamamoto, K.; Iwano, K.; Matsumoto, Y.; Watanabe, S.; Shimoi, Y.; Suda, M.; Yamamoto, H. M.; Mori, H.; Okamoto, H.

2016-01-01

In electronic-type ferroelectrics, where dipole moments produced by the variations of electron configurations are aligned, the polarization is expected to be rapidly controlled by electric fields. Such a feature can be used for high-speed electric-switching and memory devices. Electronic-type ferroelectrics include charge degrees of freedom, so that they are sometimes conductive, complicating dielectric measurements. This makes difficult the exploration of electronic-type ferroelectrics and the understanding of their ferroelectric nature. Here, we show unambiguous evidence for electronic ferroelectricity in the charge-order (CO) phase of a prototypical ET-based molecular compound, α-(ET)2I3 (ET:bis(ethylenedithio)tetrathiafulvalene), using a terahertz pulse as an external electric field. Terahertz-pump second-harmonic-generation(SHG)-probe and optical-reflectivity-probe spectroscopy reveal that the ferroelectric polarization originates from intermolecular charge transfers and is inclined 27° from the horizontal CO stripe. These features are qualitatively reproduced by the density-functional-theory calculation. After sub-picosecond polarization modulation by terahertz fields, prominent oscillations appear in the reflectivity but not in the SHG-probe results, suggesting that the CO is coupled with molecular displacements, while the ferroelectricity is electronic in nature. The results presented here demonstrate that terahertz-pump optical-probe spectroscopy is a powerful tool not only for rapidly controlling polarizations, but also for clarifying the mechanisms of ferroelectricity. PMID:26864779

Novel electronic ferroelectricity in an organic charge-order insulator investigated with terahertz-pump optical-probe spectroscopy.

PubMed

Yamakawa, H; Miyamoto, T; Morimoto, T; Yada, H; Kinoshita, Y; Sotome, M; Kida, N; Yamamoto, K; Iwano, K; Matsumoto, Y; Watanabe, S; Shimoi, Y; Suda, M; Yamamoto, H M; Mori, H; Okamoto, H

2016-02-11

In electronic-type ferroelectrics, where dipole moments produced by the variations of electron configurations are aligned, the polarization is expected to be rapidly controlled by electric fields. Such a feature can be used for high-speed electric-switching and memory devices. Electronic-type ferroelectrics include charge degrees of freedom, so that they are sometimes conductive, complicating dielectric measurements. This makes difficult the exploration of electronic-type ferroelectrics and the understanding of their ferroelectric nature. Here, we show unambiguous evidence for electronic ferroelectricity in the charge-order (CO) phase of a prototypical ET-based molecular compound, α-(ET)2I3 (ET:bis(ethylenedithio)tetrathiafulvalene), using a terahertz pulse as an external electric field. Terahertz-pump second-harmonic-generation(SHG)-probe and optical-reflectivity-probe spectroscopy reveal that the ferroelectric polarization originates from intermolecular charge transfers and is inclined 27° from the horizontal CO stripe. These features are qualitatively reproduced by the density-functional-theory calculation. After sub-picosecond polarization modulation by terahertz fields, prominent oscillations appear in the reflectivity but not in the SHG-probe results, suggesting that the CO is coupled with molecular displacements, while the ferroelectricity is electronic in nature. The results presented here demonstrate that terahertz-pump optical-probe spectroscopy is a powerful tool not only for rapidly controlling polarizations, but also for clarifying the mechanisms of ferroelectricity.

FAST TRACK COMMUNICATION: Pyroxenes: a new class of multiferroics

NASA Astrophysics Data System (ADS)

Jodlauk, S.; Becker, P.; Mydosh, J. A.; Khomskii, D. I.; Lorenz, T.; Streltsov, S. V.; Hezel, D. C.; Bohatý, L.

2007-10-01

Pyroxenes with the general formula AMSi2O6 (A = mono- or divalent metal, M = di- or trivalent metal) are shown to be a new class of multiferroic materials. In particular, we have found so far that NaFeSi2O6 becomes ferroelectric in a magnetically ordered state below ~6 K. Similarly, magnetically driven ferroelectricity is also detected in the Li homologues, LiFeSi2O6 (TC~18 K) and LiCrSi2O6 (TC~11 K). In all these monoclinic systems the electric polarization can be strongly modified by magnetic fields. Measurements of magnetic susceptibility, pyroelectric current and dielectric constants (and their dependence on magnetic field) are performed using a natural crystal of aegirine (NaFeSi2O6) and synthetic crystals of LiFeSi2O6 and LiCrSi2O6 grown from melt solution. For NaFeSi2O6 a temperature versus magnetic field phase diagram is proposed. Exchange constants are computed on the basis of ab initio band structure calculations. The possibility of a spiral magnetic structure caused by frustration to be the reason for the origin of the multiferroic behaviour is discussed. We propose that other pyroxenes may also be multiferroic, and that the versatility of this family offers an exceptional opportunity to study general conditions for and mechanisms of magnetically driven ferroelectricity.

Inversion of ferrimagnetic magnetization by ferroelectric switching via a novel magnetoelectric coupling

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

Weng, Yakui; Lin, Lingfang; Dagotto, Elbio

2016-07-12

Although several multiferroic materials or heterostructures have been extensively studied, finding strong magnetoelectric couplings for the electric field control of the magnetization remains challenging. Here, a novel interfacial magnetoelectric coupling based on three components (ferroelectric dipole, magnetic moment, and antiferromagnetic order) is analytically formulated. As an extension of carrier-mediated magnetoelectricity, the new coupling is shown to induce an electric-magnetic hysteresis loop. In addition, realizations employing BiFeO 3 bilayers grown along the [111] axis are proposed. Without involving magnetic phase transitions, the magnetization orientation can be switched by the carrier modulation driven by the field effect, as confirmed using first-principles calculations.

Defect-driven flexochemical coupling in thin ferroelectric films

NASA Astrophysics Data System (ADS)

Eliseev, Eugene A.; Vorotiahin, Ivan S.; Fomichov, Yevhen M.; Glinchuk, Maya D.; Kalinin, Sergei V.; Genenko, Yuri A.; Morozovska, Anna N.

2018-01-01

Using the Landau-Ginzburg-Devonshire theory, we considered the impact of the flexoelectrochemical coupling on the size effects in polar properties and phase transitions of thin ferroelectric films with a layer of elastic defects. We investigated a typical case, when defects fill a thin layer below the top film surface with a constant concentration creating an additional gradient of elastic fields. The defective surface of the film is not covered with an electrode, but instead with an ultrathin layer of ambient screening charges, characterized by a surface screening length. Obtained results revealed an unexpectedly strong effect of the joint action of Vegard stresses and flexoelectric effect (shortly flexochemical coupling) on the ferroelectric transition temperature, distribution of the spontaneous polarization and elastic fields, domain wall structure and period in thin PbTi O3 films containing a layer of elastic defects. A nontrivial result is the persistence of ferroelectricity at film thicknesses below 4 nm, temperatures lower than 350 K, and relatively high surface screening length (˜0.1 nm ) . The origin of this phenomenon is the flexoelectric coupling leading to the rebuilding of the domain structure in the film (namely the cross-over from c-domain stripes to a-type closure domains) when its thickness decreases below 4 nm. The ferroelectricity persistence is facilitated by negative Vegard effect. For positive Vegard effect, thicker films exhibit the appearance of pronounced maxima on the thickness dependence of the transition temperature, whose position and height can be controlled by the defect type and concentration. The revealed features may have important implications for miniaturization of ferroelectric-based devices.

Graphene Exfoliation at a Ferroelectric Domain Wall Induced by the Piezoelectric Effect: Impact on the Conductance of the Graphene Channel

NASA Astrophysics Data System (ADS)

Morozovska, Anna N.; Kurchak, Anatolii I.; Strikha, Maksym V.

2017-11-01

p -n junctions in graphene on ferroelectric substrates have been actively studied, but the impact of the piezoelectric effect in ferroelectric substrate with ferroelectric domain walls (FDWs) on graphene characteristics was not considered. Because of the piezoeffect, ferroelectric domain stripes with opposite spontaneous polarizations elongate or contract depending on the polarity of voltage applied to the substrate. We show that the alternating piezoelectric displacement of the ferroelectric domain surfaces can lead to the alternate stretching and separation of graphene areas at the steps between elongated and contracted domains. Graphene separation at FDWs induced by the piezoeffect can cause unusual effects. In particular, the conductance of the graphene channel in a field-effect transistor increases significantly because electrons in the stretched section scatter on acoustic phonons. At the same time, the graphene conductance is determined by ferroelectric spontaneous polarization and varies greatly in the presence of FDWs. The revealed piezomechanism of graphene conductance control is promising for next generations of graphene-based field-effect transistors, modulators, electrical transducers, and piezoresistive elements. Also, our results propose the method of suspended graphene fabrication based on the piezoeffect in a ferroelectric substrate that does not require any additional technological procedures.

Antiferroelectric Nature of CH3NH3PbI3−xClx Perovskite and Its Implication for Charge Separation in Perovskite Solar Cells

PubMed Central

Sewvandi, Galhenage A.; Kodera, Kei; Ma, Hao; Nakanishi, Shunsuke; Feng, Qi

2016-01-01

Perovskite solar cells (PSCs) have been attracted scientific interest due to high performance. Some researchers have suggested anomalous behavior of PSCs to the polarizations due to the ion migration or ferroelectric behavior. Experimental results and theoretical calculations have suggested the possibility of ferroelectricity in organic-inorganic perovskite. However, still no studies have been concretely discarded the ferroelectric nature of perovskite absorbers in PSCs. Hysteresis of P-E (polarization-electric field) loops is an important evidence to confirm the ferroelectricity. In this study, P-E loop measurements, in-depth structural study, analyses of dielectric behavior and the phase transitions of CH3NH3PbI3−xClx perovskite were carried out and investigated. The results suggest that CH3NH3PbI3−xClx perovskite is in an antiferroelectric phase at room temperature. The antiferroelectric phase can be switched to ferroelectric phase by the poling treatment and exhibits ferroelectric-like hysteresis P-E loops and dielectric behavior around room temperature; namely, the perovskite can generate a ferroelectric polarization under PSCs operating conditions. Furthermore, we also discuss the implications of ferroelectric polarization on PSCs charge separation. PMID:27468802

Enhancement of Local Photovoltaic Current at Ferroelectric Domain Walls in BiFeO3

PubMed Central

Yang, Ming-Min; Bhatnagar, Akash; Luo, Zheng-Dong; Alexe, Marin

2017-01-01

Domain walls, which are intrinsically two dimensional nano-objects exhibiting nontrivial electronic and magnetic behaviours, have been proven to play a crucial role in photovoltaic properties of ferroelectrics. Despite this recognition, the electronic properties of domain walls under illumination until now have been accessible only to macroscopic studies and their effects upon the conduction of photovoltaic current still remain elusive. The lack of understanding hinders the developing of nanoscale devices based on ferroelectric domain walls. Here, we directly characterize the local photovoltaic and photoconductive properties of 71° domain walls on BiFeO3 thin films with a nanoscale resolution. Local photovoltaic current, proven to be driven by the bulk photovoltaic effect, has been probed over the whole illuminated surface by using a specially designed photoelectric atomic force microscopy and found to be significantly enhanced at domain walls. Additionally, spatially resolved photoconductive current distribution reveals a higher density of excited carriers at domain walls in comparison with domains. Our measurements demonstrate that domain wall enhanced photovoltaic current originates from its high conduction rather than the internal electric field. This photoconduction facilitated local photovoltaic current is likely to be a universal property of topological defects in ferroelectric semiconductors. PMID:28216672

Enhancement of Local Photovoltaic Current at Ferroelectric Domain Walls in BiFeO3.

PubMed

Yang, Ming-Min; Bhatnagar, Akash; Luo, Zheng-Dong; Alexe, Marin

2017-02-20

Domain walls, which are intrinsically two dimensional nano-objects exhibiting nontrivial electronic and magnetic behaviours, have been proven to play a crucial role in photovoltaic properties of ferroelectrics. Despite this recognition, the electronic properties of domain walls under illumination until now have been accessible only to macroscopic studies and their effects upon the conduction of photovoltaic current still remain elusive. The lack of understanding hinders the developing of nanoscale devices based on ferroelectric domain walls. Here, we directly characterize the local photovoltaic and photoconductive properties of 71° domain walls on BiFeO 3 thin films with a nanoscale resolution. Local photovoltaic current, proven to be driven by the bulk photovoltaic effect, has been probed over the whole illuminated surface by using a specially designed photoelectric atomic force microscopy and found to be significantly enhanced at domain walls. Additionally, spatially resolved photoconductive current distribution reveals a higher density of excited carriers at domain walls in comparison with domains. Our measurements demonstrate that domain wall enhanced photovoltaic current originates from its high conduction rather than the internal electric field. This photoconduction facilitated local photovoltaic current is likely to be a universal property of topological defects in ferroelectric semiconductors.

Efficient excitation of nonlinear phonons via chirped pulses: Induced structural phase transitions

NASA Astrophysics Data System (ADS)

Itin, A. P.; Katsnelson, M. I.

2018-05-01

Nonlinear phononics play important role in strong laser-solid interactions. We discuss a dynamical protocol for efficient phonon excitation, considering recent inspiring proposals: inducing ferroelectricity in paraelectric perovskites, and inducing structural deformations in cuprates [Subedi et al., Phys. Rev. B 89, 220301(R) (2014), 10.1103/PhysRevB.89.220301; Phys. Rev. B 95, 134113 (2017), 10.1103/PhysRevB.95.134113]. High-frequency phonon modes are driven by midinfrared pulses, and coupled to lower-frequency modes those indirect excitations cause structural deformations. We study in more detail the case of KTaO3 without strain, where it was not possible to excite the needed low-frequency phonon mode by resonant driving of the higher frequency one. Behavior of the system is explained using a reduced model of coupled driven nonlinear oscillators. We find a dynamical mechanism which prevents effective excitation at resonance driving. To induce ferroelectricity, we employ driving with sweeping frequency, realizing so-called capture into resonance. The method can be applied to many other related systems.

Negative Capacitance in BaTiO3/BiFeO3 Bilayer Capacitors.

PubMed

Hou, Ya-Fei; Li, Wei-Li; Zhang, Tian-Dong; Yu, Yang; Han, Ren-Lu; Fei, Wei-Dong

2016-08-31

Negative capacitances provide an approach to reduce heat generations in field-effect transistors during the switch processes, which contributes to further miniaturization of the conventional integrated circuits. Although there are many studies about negative capacitances using ferroelectric materials, the direct observation of stable ferroelectric negative capacitances has rarely been reported. Here, we put forward a dc bias assistant model in bilayer capacitors, where one ferroelectric layer with large dielectric constant and the other ferroelectric layer with small dielectric constant are needed. Negative capacitances can be obtained when external dc bias electric fields are larger than a critical value. Based on the model, BaTiO3/BiFeO3 bilayer capacitors are chosen as study objects, and negative capacitances are observed directly. Additionally, the upward self-polarization effect in the ferroelectric layer reduces the critical electric field, which may provide a method for realizing zero and/or small dc bias assistant negative capacitances.

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

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.

Coexistence of Weak Ferromagnetism and Ferroelectricity in the High Pressure LiNbO3-Type Phase of FeTiO3

NASA Astrophysics Data System (ADS)

Varga, T.; Kumar, A.; Vlahos, E.; Denev, S.; Park, M.; Hong, S.; Sanehira, T.; Wang, Y.; Fennie, C. J.; Streiffer, S. K.; Ke, X.; Schiffer, P.; Gopalan, V.; Mitchell, J. F.

2009-07-01

We report the magnetic and electrical characteristics of polycrystalline FeTiO3 synthesized at high pressure that is isostructural with acentric LiNbO3 (LBO). Piezoresponse force microscopy, optical second harmonic generation, and magnetometry demonstrate ferroelectricity at and below room temperature and weak ferromagnetism below ˜120K. These results validate symmetry-based criteria and first-principles calculations of the coexistence of ferroelectricity and weak ferromagnetism in a series of transition metal titanates crystallizing in the LBO structure.

Coexistence of weak ferromagnetism and ferroelectricity in the high pressure LiNbO3-type phase of FeTiO3.

PubMed

Varga, T; Kumar, A; Vlahos, E; Denev, S; Park, M; Hong, S; Sanehira, T; Wang, Y; Fennie, C J; Streiffer, S K; Ke, X; Schiffer, P; Gopalan, V; Mitchell, J F

2009-07-24

We report the magnetic and electrical characteristics of polycrystalline FeTiO_{3} synthesized at high pressure that is isostructural with acentric LiNbO_{3} (LBO). Piezoresponse force microscopy, optical second harmonic generation, and magnetometry demonstrate ferroelectricity at and below room temperature and weak ferromagnetism below approximately 120 K. These results validate symmetry-based criteria and first-principles calculations of the coexistence of ferroelectricity and weak ferromagnetism in a series of transition metal titanates crystallizing in the LBO structure.

Nanoscale Origins of Ferroelastic Domain Wall Mobility in Ferroelectric Multilayers

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

Huang, Hsin-Hui; Hong, Zijian; Xin, Huolin L.

Here we investigate the nanoscale origins of ferroelastic domain wall motion in ferroelectric multilayer thin films that lead to giant electromechanical responses. We present direct evidence for complex underpinning factors that result in ferroelastic domain wall mobility using a combination of atomic-level aberration corrected scanning transmission electron microscopy and phase-field simulations in model epitaxial (001) tetragonal (T) PbZr xTi 1-xO 3 (PZT)/rhombohedral (R) PbZr xTi 1-xO 3 (PZT) bilayer heterostructures. The local electric dipole distribution is imaged on an atomic scale for a ferroelastic domain wall that nucleates in the R-layer and cuts through the composition breaking the T/R interface.more » Our studies reveal a highly complex polarization rotation domain structure that is nearly on the knife-edge at the vicinity of this wall. Induced phases, namely tetragonal-like and rhombohedral-like monoclinic were observed close to the interface, and exotic domain arrangements, such as a half-four-fold closure structure, are observed. Phase field simulations show this is due to the minimization of the excessive elastic and electrostatic energies driven by the enormous strain gradient present at the location of the ferroelastic domain walls. Thus, in response to an applied stimulus, such as an electric field, any polarization reorientation must minimize the elastic and electrostatic discontinuities due to this strain gradient, which would induce a dramatic rearrangement of the domain structure. This insight into the origins of ferroelastic domain wall motion will allow researchers to better “craft” such multilayered ferroelectric systems with precisely tailored domain wall functionality and enhanced sensitivity, which can be exploited for the next generation of integrated piezoelectric technologies.« less

Nanoscale Origins of Ferroelastic Domain Wall Mobility in Ferroelectric Multilayers

DOE PAGES

Huang, Hsin-Hui; Hong, Zijian; Xin, Huolin L.; ...

2016-10-31

Here we investigate the nanoscale origins of ferroelastic domain wall motion in ferroelectric multilayer thin films that lead to giant electromechanical responses. We present direct evidence for complex underpinning factors that result in ferroelastic domain wall mobility using a combination of atomic-level aberration corrected scanning transmission electron microscopy and phase-field simulations in model epitaxial (001) tetragonal (T) PbZr xTi 1-xO 3 (PZT)/rhombohedral (R) PbZr xTi 1-xO 3 (PZT) bilayer heterostructures. The local electric dipole distribution is imaged on an atomic scale for a ferroelastic domain wall that nucleates in the R-layer and cuts through the composition breaking the T/R interface.more » Our studies reveal a highly complex polarization rotation domain structure that is nearly on the knife-edge at the vicinity of this wall. Induced phases, namely tetragonal-like and rhombohedral-like monoclinic were observed close to the interface, and exotic domain arrangements, such as a half-four-fold closure structure, are observed. Phase field simulations show this is due to the minimization of the excessive elastic and electrostatic energies driven by the enormous strain gradient present at the location of the ferroelastic domain walls. Thus, in response to an applied stimulus, such as an electric field, any polarization reorientation must minimize the elastic and electrostatic discontinuities due to this strain gradient, which would induce a dramatic rearrangement of the domain structure. This insight into the origins of ferroelastic domain wall motion will allow researchers to better “craft” such multilayered ferroelectric systems with precisely tailored domain wall functionality and enhanced sensitivity, which can be exploited for the next generation of integrated piezoelectric technologies.« less

Influence of anisotropic strain on the dielectric and ferroelectric properties of SrTiO3 thin films on DyScO3 substrates

NASA Astrophysics Data System (ADS)

Biegalski, M. D.; Vlahos, E.; Sheng, G.; Li, Y. L.; Bernhagen, M.; Reiche, P.; Uecker, R.; Streiffer, S. K.; Chen, L. Q.; Gopalan, V.; Schlom, D. G.; Trolier-McKinstry, S.

2009-06-01

The in-plane dielectric and ferroelectric properties of coherent anisotropically strained SrTiO3 thin films grown on orthorhombic (101) DyScO3 substrates were examined as a function of the angle between the applied electric field and the principal directions of the substrate. The dielectric permittivity revealed two distinct maxima as a function of temperature along the [100]p and [010]p SrTiO3 pseudocubic directions. These data, in conjunction with optical second-harmonic generation, show that the switchable ferroelectric polarization develops first predominantly along the in-plane axis with the larger tensile strain before developing a polarization component along the perpendicular direction with smaller strain as well, leading to domain twinning at the lower temperature. Finally, weak signatures in the dielectric and second-harmonic generation response were detected at the SrTiO3 tilt transition close to 165 K. These studies indicate that anisotropic biaxial strain can lead to new ferroelectric domain reorientation transitions that are not observed in isotropically strained films.

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.

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.

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

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 properties and phase transformation behavior which can be tailored by modifying the chemical composition, processing conditions, and the loading history (poling). This results in optimization of system performance by tailoring material properties and phase transformation behavior. This approach applied to three ferroelectric phase transformation-based applications: 1. Ferroelectric energy generation 2. Ferroelectric high-energy storage capacitor 3. Ferroelectric thermal energy harvesting. This dissertation has addressed tuning the large field properties for phase transformation-based systems.

Polarization curling and flux closures in multiferroic tunnel junctions

NASA Astrophysics Data System (ADS)

Peters, Jonathan J. P.; Apachitei, Geanina; Beanland, Richard; Alexe, Marin; Sanchez, Ana M.

2016-11-01

Formation of domain walls in ferroelectrics is not energetically favourable in low-dimensional systems. Instead, vortex-type structures are formed that are driven by depolarization fields occurring in such systems. Consequently, polarization vortices have only been experimentally found in systems in which these fields are deliberately maximized, that is, in films between insulating layers. As such configurations are devoid of screening charges provided by metal electrodes, commonly used in electronic devices, it is wise to investigate if curling polarization structures are innate to ferroelectricity or induced by the absence of electrodes. Here we show that in unpoled Co/PbTiO3/(La,Sr)MnO3 ferroelectric tunnel junctions, the polarization in active PbTiO3 layers 9 unit cells thick forms Kittel-like domains, while at 6 unit cells there is a complex flux-closure curling behaviour resembling an incommensurate phase. Reducing the thickness to 3 unit cells, there is an almost complete loss of switchable polarization associated with an internal gradient.

Polarization curling and flux closures in multiferroic tunnel junctions

PubMed Central

Peters, Jonathan J. P.; Apachitei, Geanina; Beanland, Richard; Alexe, Marin; Sanchez, Ana M.

2016-01-01

Formation of domain walls in ferroelectrics is not energetically favourable in low-dimensional systems. Instead, vortex-type structures are formed that are driven by depolarization fields occurring in such systems. Consequently, polarization vortices have only been experimentally found in systems in which these fields are deliberately maximized, that is, in films between insulating layers. As such configurations are devoid of screening charges provided by metal electrodes, commonly used in electronic devices, it is wise to investigate if curling polarization structures are innate to ferroelectricity or induced by the absence of electrodes. Here we show that in unpoled Co/PbTiO3/(La,Sr)MnO3 ferroelectric tunnel junctions, the polarization in active PbTiO3 layers 9 unit cells thick forms Kittel-like domains, while at 6 unit cells there is a complex flux-closure curling behaviour resembling an incommensurate phase. Reducing the thickness to 3 unit cells, there is an almost complete loss of switchable polarization associated with an internal gradient. PMID:27848970

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.

Electrically reversible cracks in an intermetallic film controlled by an electric field

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

Liu, Z. Q.; Liu, J. H.; Biegalski, M. D.

Cracks in solid-state materials are typically irreversible. We report electrically reversible opening and closing of nanoscale cracks in an intermetallic thin film grown on a ferroelectric substrate driven by a small electric field (~0.83 kV/cm). Accordingly, a nonvolatile colossal electroresistance on-off ratio of more than 10 8 is measured across the cracks in the intermetallic film at room temperature. Cracks are easily formed with low-frequency voltage cycling and remain stable when the device is operated at high frequency, which offers intriguing potential for next-generation high-frequency memory applications. Moreover, endurance testing demonstrates that the opening and closing of such cracks canmore » reach over 10 7 cycles under 10-μs pulses, without catastrophic failure of the film.« less

Electrically reversible cracks in an intermetallic film controlled by an electric field

DOE PAGES

Liu, Z. Q.; Liu, J. H.; Biegalski, M. D.; ...

2018-01-03

Cracks in solid-state materials are typically irreversible. We report electrically reversible opening and closing of nanoscale cracks in an intermetallic thin film grown on a ferroelectric substrate driven by a small electric field (~0.83 kV/cm). Accordingly, a nonvolatile colossal electroresistance on-off ratio of more than 10 8 is measured across the cracks in the intermetallic film at room temperature. Cracks are easily formed with low-frequency voltage cycling and remain stable when the device is operated at high frequency, which offers intriguing potential for next-generation high-frequency memory applications. Moreover, endurance testing demonstrates that the opening and closing of such cracks canmore » reach over 10 7 cycles under 10-μs pulses, without catastrophic failure of the film.« less

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.

Polarization-dependent interfacial coupling modulation of ferroelectric photovoltaic effect in PZT-ZnO heterostructures

NASA Astrophysics Data System (ADS)

Pan, Dan-Feng; Bi, Gui-Feng; Chen, Guang-Yi; Zhang, Hao; Liu, Jun-Ming; Wang, Guang-Hou; Wan, Jian-Guo

2016-03-01

Recently, ferroelectric perovskite oxides have drawn much attention due to potential applications in the field of solar energy conversion. However, the power conversion efficiency of ferroelectric photovoltaic effect currently reported is far below the expectable value. One of the crucial problems lies in the two back-to-back Schottky barriers, which are formed at the ferroelectric-electrode interfaces and blocking most of photo-generated carriers to reach the outside circuit. Herein, we develop a new approach to enhance the ferroelectric photovoltaic effect by introducing the polarization-dependent interfacial coupling effect. Through inserting a semiconductor ZnO layer with spontaneous polarization into the ferroelectric ITO/PZT/Au film, a p-n junction with strong polarization-dependent interfacial coupling effect is formed. The power conversion efficiency of the heterostructure is improved by nearly two orders of magnitude and the polarization modulation ratio is increased about four times. It is demonstrated that the polarization-dependent interfacial coupling effect can give rise to a great change in band structure of the heterostructure, not only producing an aligned internal electric field but also tuning both depletion layer width and potential barrier height at PZT-ZnO interface. This work provides an efficient way in developing highly efficient ferroelectric-based solar cells and novel optoelectronic memory devices.

Polarization-dependent interfacial coupling modulation of ferroelectric photovoltaic effect in PZT-ZnO heterostructures.

PubMed

Pan, Dan-Feng; Bi, Gui-Feng; Chen, Guang-Yi; Zhang, Hao; Liu, Jun-Ming; Wang, Guang-Hou; Wan, Jian-Guo

2016-03-08

Recently, ferroelectric perovskite oxides have drawn much attention due to potential applications in the field of solar energy conversion. However, the power conversion efficiency of ferroelectric photovoltaic effect currently reported is far below the expectable value. One of the crucial problems lies in the two back-to-back Schottky barriers, which are formed at the ferroelectric-electrode interfaces and blocking most of photo-generated carriers to reach the outside circuit. Herein, we develop a new approach to enhance the ferroelectric photovoltaic effect by introducing the polarization-dependent interfacial coupling effect. Through inserting a semiconductor ZnO layer with spontaneous polarization into the ferroelectric ITO/PZT/Au film, a p-n junction with strong polarization-dependent interfacial coupling effect is formed. The power conversion efficiency of the heterostructure is improved by nearly two orders of magnitude and the polarization modulation ratio is increased about four times. It is demonstrated that the polarization-dependent interfacial coupling effect can give rise to a great change in band structure of the heterostructure, not only producing an aligned internal electric field but also tuning both depletion layer width and potential barrier height at PZT-ZnO interface. This work provides an efficient way in developing highly efficient ferroelectric-based solar cells and novel optoelectronic memory devices.

Integrating Epitaxial-Like Pb(Zr,Ti)O3 Thin-Film into Silicon for Next-Generation Ferroelectric Field-Effect Transistor

PubMed Central

Park, Jae Hyo; Kim, Hyung Yoon; Jang, Gil Su; Seok, Ki Hwan; Chae, Hee Jae; Lee, Sol Kyu; Kiaee, Zohreh; Joo, Seung Ki

2016-01-01

The development of ferroelectric random-access memory (FeRAM) technology with control of grain boundaries would result in a breakthrough for new nonvolatile memory devices. The excellent piezoelectric and electrical properties of bulk ferroelectrics are degraded when the ferroelectric is processed into thin films because the grain boundaries then form randomly. Controlling the nature of nucleation and growth are the keys to achieving a good crystalline thin-film. However, the sought after high-quality ferroelectric thin-film has so far been thought to be impossible to make, and research has been restricted to atomic-layer deposition which is extremely expensive and has poor reproducibility. Here we demonstrate a novel epitaxial-like growth technique to achieve extremely uniform and large rectangular-shaped grains in thin-film ferroelectrics by dividing the nucleation and growth phases. With this technique, it is possible to achieve 100-μm large uniform grains, even made available on Si, which is large enough to fabricate a field-effect transistor in each grain. The electrical and reliability test results, including endurance and retention test results, were superior to other FeRAMs reported so far and thus the results presented here constitute the first step toward the development of FeRAM using epitaxial-like ferroelectric thin-films. PMID:27005886

Polarization-dependent interfacial coupling modulation of ferroelectric photovoltaic effect in PZT-ZnO heterostructures

PubMed Central

Pan, Dan-Feng; Bi, Gui-Feng; Chen, Guang-Yi; Zhang, Hao; Liu, Jun-Ming; Wang, Guang-Hou; Wan, Jian-Guo

2016-01-01

Recently, ferroelectric perovskite oxides have drawn much attention due to potential applications in the field of solar energy conversion. However, the power conversion efficiency of ferroelectric photovoltaic effect currently reported is far below the expectable value. One of the crucial problems lies in the two back-to-back Schottky barriers, which are formed at the ferroelectric-electrode interfaces and blocking most of photo-generated carriers to reach the outside circuit. Herein, we develop a new approach to enhance the ferroelectric photovoltaic effect by introducing the polarization-dependent interfacial coupling effect. Through inserting a semiconductor ZnO layer with spontaneous polarization into the ferroelectric ITO/PZT/Au film, a p-n junction with strong polarization-dependent interfacial coupling effect is formed. The power conversion efficiency of the heterostructure is improved by nearly two orders of magnitude and the polarization modulation ratio is increased about four times. It is demonstrated that the polarization-dependent interfacial coupling effect can give rise to a great change in band structure of the heterostructure, not only producing an aligned internal electric field but also tuning both depletion layer width and potential barrier height at PZT-ZnO interface. This work provides an efficient way in developing highly efficient ferroelectric-based solar cells and novel optoelectronic memory devices. PMID:26954833

Lack of ferroelectricity in PbTiO3 at high pressures

NASA Astrophysics Data System (ADS)

Cohen, R. E.; Ahart, Muhtar; Hemley, Russell J.

The classic ferroelectric PbTiO3 continues to surprise. It was believed that ferroelectrics would become paraelectric under pressure, and this was observed in Raman experiments on PbTiO3. We predicted a morphotropic phase transition under pressure and verified it experimentally. At higher pressures it become paraelectric, but DFT predicted higher pressure ferroelectricity, and this seemed confirmed by experiments. New Second Harmonic Generation (SHG) measurements on PbTiO3 to 100 GPa and down to 10 K find no evidence for ferroelectricity above 20 GPa. Our DFT computations show centrosymmetric I4mcm as most stable from 20-90 GPa; I4mcm is the ground state of SrTiO3, and the rotations quench the polar instability. We predict a polar I4cm structure above 90 GPa, but the double well depth is very small. This work has been supported by the US ONR, ERC Advanced Grant ToMCaT, EFREE, CDAC, NSF and the Carnegie Institution for Science.

Three-dimensional imaging of vortex structure in a ferroelectric nanoparticle driven by an electric field.

PubMed

Karpov, D; Liu, Z; Rolo, T Dos Santos; Harder, R; Balachandran, P V; Xue, D; Lookman, T; Fohtung, E

2017-08-17

Topological defects of spontaneous polarization are extensively studied as templates for unique physical phenomena and in the design of reconfigurable electronic devices. Experimental investigations of the complex topologies of polarization have been limited to surface phenomena, which has restricted the probing of the dynamic volumetric domain morphology in operando. Here, we utilize Bragg coherent diffractive imaging of a single BaTiO 3 nanoparticle in a composite polymer/ferroelectric capacitor to study the behavior of a three-dimensional vortex formed due to competing interactions involving ferroelectric domains. Our investigation of the structural phase transitions under the influence of an external electric field shows a mobile vortex core exhibiting a reversible hysteretic transformation path. We also study the toroidal moment of the vortex under the action of the field. Our results open avenues for the study of the structure and evolution of polar vortices and other topological structures in operando in functional materials under cross field configurations.Imaging of topological states of matter such as vortex configurations has generally been limited to 2D surface effects. Here Karpov et al. study the volumetric structure and dynamics of a vortex core mediated by electric-field induced structural phase transition in a ferroelectric BaTiO 3 nanoparticle.

Mesoscopic Free Path of Nonthermalized Photogenerated Carriers in a Ferroelectric Insulator.

PubMed

Gu, Zongquan; Imbrenda, Dominic; Bennett-Jackson, Andrew L; Falmbigl, Matthias; Podpirka, Adrian; Parker, Thomas C; Shreiber, Daniel; Ivill, Mathew P; Fridkin, Vladimir M; Spanier, Jonathan E

2017-03-03

We show how finite-size scaling of a bulk photovoltaic effect-generated electric field in epitaxial ferroelectric insulating BaTiO_{3}(001) films and a photo-Hall response involving the bulk photovoltaic current reveal a large room-temperature mean free path of photogenerated nonthermalized electrons. Experimental determination of mesoscopic ballistic optically generated carrier transport opens a new paradigm for hot electron-based solar energy conversion, and for facile control of ballistic transport distinct from existing low-dimensional semiconductor interfaces, surfaces, layers, or other structures.

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.

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.

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.

Hollandites as a new class of multiferroics

PubMed Central

Liu, Shuangyi; Akbashev, Andrew R.; Yang, Xiaohao; Liu, Xiaohua; Li, Wanlu; Zhao, Lukas; Li, Xue; Couzis, Alexander; Han, Myung-Geun; Zhu, Yimei; Krusin-Elbaum, Lia; Li, Jackie; Huang, Limin; Billinge, Simon J. L.; Spanier, Jonathan E.; O'Brien, Stephen

2014-01-01

Discovery of new complex oxides that exhibit both magnetic and ferroelectric properties is of great interest for the design of functional magnetoelectrics, in which research is driven by the technologically exciting prospect of controlling charges by magnetic fields and spins by applied voltages, for sensors, 4-state logic, and spintronics. Motivated by the notion of a tool-kit for complex oxide design, we developed a chemical synthesis strategy for single-phase multifunctional lattices. Here, we introduce a new class of multiferroic hollandite Ba-Mn-Ti oxides not apparent in nature. BaMn3Ti4O14.25, designated BMT-134, possesses the signature channel-like hollandite structure, contains Mn4+ and Mn3+ in a 1:1 ratio, exhibits an antiferromagnetic phase transition (TN ~ 120 K) with a weak ferromagnetic ordering at lower temperatures, ferroelectricity, a giant dielectric constant at low frequency and a stable intrinsic dielectric constant of ~200 (1-100 MHz). With evidence of correlated antiferromagnetic and ferroelectric order, the findings point to an unexplored family of structures belonging to the hollandite supergroup with multifunctional properties, and high potential for developing new magnetoelectric materials. PMID:25160888

Epitaxial Bi2 FeCrO6 Multiferroic Thin Film as a New Visible Light Absorbing Photocathode Material.

PubMed

Li, Shun; AlOtaibi, Bandar; Huang, Wei; Mi, Zetian; Serpone, Nick; Nechache, Riad; Rosei, Federico

2015-08-26

Ferroelectric materials have been studied increasingly for solar energy conversion technologies due to the efficient charge separation driven by the polarization induced internal electric field. However, their insufficient conversion efficiency is still a major challenge. Here, a photocathode material of epitaxial double perovskite Bi(2) FeCrO(6) multiferroic thin film is reported with a suitable conduction band position and small bandgap (1.9-2.1 eV), for visible-light-driven reduction of water to hydrogen. Photoelectrochemical measurements show that the highest photocurrent density up to -1.02 mA cm(-2) at a potential of -0.97 V versus reversible hydrogen electrode is obtained in p-type Bi(2) FeCrO(6) thin film photocathode grown on SrTiO(3) substrate under AM 1.5G simulated sunlight. In addition, a twofold enhancement of photocurrent density is obtained after negatively poling the Bi(2) FeCrO(6) thin film, as a result of modulation of the band structure by suitable control of the internal electric field gradient originating from the ferroelectric polarization in the Bi(2) FeCrO(6) films. The findings validate the use of multiferroic Bi(2) FeCrO(6) thin films as photocathode materials, and also prove that the manipulation of internal fields through polarization in ferroelectric materials is a promising strategy for the design of improved photoelectrodes and smart devices for solar energy conversion. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Exploring Anomalous Polarization Dynamics in Organometallic Halide Perovskites

DOE PAGES

Ahmadi, Mahshid; Collins, Liam; Puretzky, Alexander; ...

2018-01-22

Organometallic halide perovskites (OMHPs) have attracted broad attention as prospective materials for optoelectronic applications. Among the many anomalous properties of these materials, of special interest are the ferroelectric properties including both classical and relaxor-like components, as a potential origin of slow dynamics, field enhancement, and anomalous mobilities. Here, ferroelectric properties of the three representative OMHPs are explored, including FAPb xSn 1–xI 3 (x = 0, x = 0.85) and FA 0.85MA 0.15PbI 3 using band excitation piezoresponse force microscopy and contact mode Kelvin probe force microscopy, providing insight into long- and short-range dipole and charge dynamics in these materials andmore » probing ferroelectric density of states. Furthermore, second-harmonic generation in thin films of OMHPs is observed, providing a direct information on the noncentrosymmetric polarization in such materials. Overall, the data provide strong evidence for the presence of ferroelectric domains in these systems; however, the domain dynamics is suppressed by fast ion dynamics. These materials hence present the limit of ferroelectric materials with spontaneous polarization dynamically screened by ionic and electronic carriers.« less

Exploring Anomalous Polarization Dynamics in Organometallic Halide Perovskites

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

Ahmadi, Mahshid; Collins, Liam; Puretzky, Alexander

Organometallic halide perovskites (OMHPs) have attracted broad attention as prospective materials for optoelectronic applications. Among the many anomalous properties of these materials, of special interest are the ferroelectric properties including both classical and relaxor-like components, as a potential origin of slow dynamics, field enhancement, and anomalous mobilities. Here, ferroelectric properties of the three representative OMHPs are explored, including FAPb xSn 1–xI 3 (x = 0, x = 0.85) and FA 0.85MA 0.15PbI 3 using band excitation piezoresponse force microscopy and contact mode Kelvin probe force microscopy, providing insight into long- and short-range dipole and charge dynamics in these materials andmore » probing ferroelectric density of states. Furthermore, second-harmonic generation in thin films of OMHPs is observed, providing a direct information on the noncentrosymmetric polarization in such materials. Overall, the data provide strong evidence for the presence of ferroelectric domains in these systems; however, the domain dynamics is suppressed by fast ion dynamics. These materials hence present the limit of ferroelectric materials with spontaneous polarization dynamically screened by ionic and electronic carriers.« less

Fabrication of PVDF-TrFE based bilayered PbTiO3/PVDF-TrFE films capacitor

NASA Astrophysics Data System (ADS)

Nurbaya, Z.; Wahid, M. H.; Rozana, M. D.; Annuar, I.; Alrokayan, S. A. H.; Khan, H. A.; Rusop, M.

2016-07-01

Development of high performance capacitor is reaching towards new generation where the ferroelectric materials take places as the active dielectric layer. The motivation of this study is to produce high capacitance device with long life cycle. This was configured by preparing bilayered films where lead titanate as an active dielectric layer and stacked with the top dielectric layer, poly(vinyledenefluoride-trifluoroethylene). Both of them are being referred that have one in common which is ferroelectric behavior. Therefore the combination of ceramic and polymer ferroelectric material could perform optimum dielectric characteristic for capacitor applications. The fabrication was done by simple sol-gel spin coating method that being varied at spinning speed property for polymer layers, whereas maintaining the ceramic layer. The characterization of PVDF-TrFE/PbTiO3 was performed according to metal-insulator-metal stacked capacitor measurement which includes structural, dielectric, and ferroelectric measurement.

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

Optically controlled electroresistance and electrically controlled photovoltage in ferroelectric tunnel junctions

PubMed Central

Jin Hu, Wei; Wang, Zhihong; Yu, Weili; Wu, Tom

2016-01-01

Ferroelectric tunnel junctions (FTJs) have recently attracted considerable interest as a promising candidate for applications in the next-generation non-volatile memory technology. In this work, using an ultrathin (3 nm) ferroelectric Sm0.1Bi0.9FeO3 layer as the tunnelling barrier and a semiconducting Nb-doped SrTiO3 single crystal as the bottom electrode, we achieve a tunnelling electroresistance as large as 105. Furthermore, the FTJ memory states could be modulated by light illumination, which is accompanied by a hysteretic photovoltaic effect. These complimentary effects are attributed to the bias- and light-induced modulation of the tunnel barrier, both in height and width, at the semiconductor/ferroelectric interface. Overall, the highly tunable tunnelling electroresistance and the correlated photovoltaic functionalities provide a new route for producing and non-destructively sensing multiple non-volatile electronic states in such FTJs. PMID:26924259

p - n Junction Dynamics Induced in a Graphene Channel by Ferroelectric-Domain Motion in the Substrate

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

Kurchak, Anatolii I.; Eliseev, Eugene A.; Kalinin, Sergei V.

The p - n junction dynamics induced in a graphene channel by stripe-domain nucleation, motion, and reversal in a ferroelectric substrate is explored using a self-consistent approach based on Landau-Ginzburg-Devonshire phenomenology combined with classical electrostatics. Relatively low gate voltages are required to induce the hysteresis of ferroelectric polarization and graphene charge in response to the periodic gate voltage. Pronounced nonlinear hysteresis of graphene conductance with a wide memory window corresponds to high amplitudes of gate voltage. Also, we reveal the extrinsic size effect in the dependence of the graphene-channel conductivity on its length. We predict that the top-gate–dielectric-layer–graphene-channel–ferroelectric-substrate nanostructure consideredmore » here can be a promising candidate for the fabrication of the next generation of modulators and rectifiers based on the graphene p - n junctions.« less

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.

Simultaneous Stress and Field Control of Sustainable Switching of Ferroelectric Phases

PubMed Central

Finkel, P.; Staruch, M.; Amin, A.; Ahart, M.; Lofland, S.E.

2015-01-01

In ferroelectrics, manifestation of a strong electromechanical coupling is attributed to both engineered domain morphology and phase transformations. However, realization of large sustainable and reversible strains and polarization rotation has been limited by fatigue, nonlinearity and hysteresis losses. Here, we demonstrate that large strain and polarization rotation can be generated for over 40 × 106 cycles with little fatigue by realization of a reversible ferroelectric-ferroelectric phase transition in [011] cut Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 (PIN-PMN-PT) relaxor ferroelectric single crystal. Direct tuning of this effect through combination of stress and applied electric field, confirmed both macroscopically and microscopically with x-ray and Raman scattering, reveals the local symmetry while sweeping through the transition with a low applied electric field (<0.2 MV/m) under mechanical stress. The observed change in local symmetry as determined by x-ray scattering confirms a proposed polarization rotation mechanism corresponding to a transition between rhombohedral and orthorhombic phases. These results shed more light onto the nature of this reversible transformation between two ferroelectric phases and advance towards the development of a wide range of ferroic and multiferroic devices. PMID:26345729

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.

Physical Origin of Transient Negative Capacitance in a Ferroelectric Capacitor

NASA Astrophysics Data System (ADS)

Chang, Sou-Chi; Avci, Uygar E.; Nikonov, Dmitri E.; Manipatruni, Sasikanth; Young, Ian A.

2018-01-01

Transient negative differential capacitance, the dynamic reversal of transient capacitance in an electrical circuit, is of highly technological and scientific interest since it probes the foundation of ferroelectricity. We study a resistor-ferroelectric capacitor (R -FEC) network through a series of coupled equations based on Kirchhoff's law, electrostatics, and Landau theory. We show that transient negative capacitance (NC) in a R -FEC circuit originates from the mismatch in switching rate between the free charge on the metal plate and the bound charge in a ferroelectric (FE) capacitor during the polarization switching. This transient free charge-polarization mismatch is driven by the negative curvature of the FE free-energy landscape, and it is also analytically shown that a free-energy profile with a negative curvature is the only physical system that can describe transient NC in a R -FEC circuit. Furthermore, transient NC induced by the free charge-polarization mismatch is justified by its dependence on both external resistance and the intrinsic FE viscosity coefficient. The depolarization effect on FE capacitors emphasizes the importance of negative curvature to transient NC and also implies that transient and steady-state NC cannot be observed in a FE capacitor simultaneously. Finally, using the transient NC measurements, a procedure to experimentally determine the viscosity coefficient is presented to provide more insight into the relation between transient NC and the FE free-energy profile.

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 system under similar physical conditions. At intermediate dopant concentration, the material undergoes a diffuse phase transition smeared within a temperature range to a ferroelectric state. A further increase in the dopant concentration makes the transition sharper and closer to the conventional ferroelectric transition. The results obtained are compared with the behavior of the K1-xLixTaO 3 relaxor ferroelectric.

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 acoustically isolate the resonator from the damping effect of the substrate, enhancing the quality factor and temperature compensation.

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.

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

A Force to Reckon With

NASA Technical Reports Server (NTRS)

1999-01-01

Through a licensing agreement with NASA, Face International Corporation has successfully commercialized ferroelectric actuator/sensor technology developed at Langley Research Center. Face International manufactures both ferroelectric actuators and sensors under the trademark "Thunder" (Thin Layer Composite Unimorph Ferroelectric Driver and Sensor). As actuators the Thunder technology provides a high level of movement not seen before in piezoelectric devices. Crystal structures generate electricity when stressed and move when voltage is applied. As sensors, the technology can be used in such applications as microphones, non-destructive testing, and vibration sensing. Thunder technology is being researched as a noise reduction device for aircraft engines. The technology is durable enough to be used in harsh environments, making it applicable to many commercial applications.

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.

Metal-ferroelectric-metal capacitor based persistent memory for electronic product code class-1 generation-2 uhf passive radio-frequency identification tag

NASA Astrophysics Data System (ADS)

Yoon, Bongno; Sung, Man Young; Yeon, Sujin; Oh, Hyun S.; Kwon, Yoonjoo; Kim, Chuljin; Kim, Kyung-Ho

2009-03-01

With the circuits using metal-ferroelectric-metal (MFM) capacitor, rf operational signal properties are almost the same or superior to those of polysilicon-insulator-polysilicon, metal-insulator-metal, and metal-oxide-semiconductor (MOS) capacitors. In electronic product code global class-1 generation-2 uhf radio-frequency identification (RFID) protocols, the MFM can play a crucial role in satisfying the specifications of the inventoried flag's persistence times (Tpt) for each session (S0-S3, SL). In this paper, we propose and design a new MFM capacitor based memory scheme of which persistence time for S1 flag is measured at 2.2 s as well as indefinite for S2, S3, and SL flags during the period of power-on. A ferroelectric random access memory embedded RFID tag chip is fabricated with an industry-standard complementary MOS process. The chip size is around 500×500 μm2 and the measured power consumption is about 10 μW.

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

Tailoring Electronic Properties in Semiconducting Perovskite Materials through Octahedral Control

NASA Astrophysics Data System (ADS)

Choquette, Amber K.

Perovskite oxides, which take the chemical formula ABO 3, are a very versatile and interesting materials family, exhibiting properties that include ferroelectricity, ferromagnetism, mixed ionic/electronic conductivity, metal-insulator behavior and multiferroicity. Key to these functionalities is the network of BO6 corner-connected octahedra, which are known to distort and rotate, directly altering electronic and ferroic properties. By controlling the BO6 octahedral distortions and rotations through cationic substitutions, the use of strain engineering, or through the formation of superlattice structures, the functional properties of perovskites can be tuned. Motivating the use of structure-driven design in oxide heterostructures is the prediction of hybrid improper ferroelectricity in A'BO3/ABO3 superlattices. Two key design rules to realizing hybrid improper ferroelectricity are the growth of high quality superlattice structures with odd periodicities of the A / A' layers, and the control of the octahedral rotation pattern. My work explores the rotational response in perovskite oxides to strain and interface effects in thin films of RFeO3 ( R = La, Eu). I demonstrate a synchrotron x-ray diffraction technique to identify the rotation pattern that is present in the films. I then establish substrate imprinting as a key tool for controlling the rotation patterns in heterostructures, providing a means to realize the necessary structural variants of the predicted hybrid improper ferroelectricity in superlattices. In addition, by pairing measured diffraction data with a structure factor calculation, I demonstrate how one can extract both A-site and oxygen atomic positions in single crystal perovskite oxide films. Finally, I show results from (LaFeO 3)n/(EuFeO3)n superlattices (n = 1-5), synthesized to test the motivating predictions of hybrid improper ferroelectricity in oxide superlattices.

Multidimensional dynamic piezoresponse measurements. Unraveling local relaxation behavior in relaxor-ferroelectrics via big data

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

Vasudevan, Rama K.; Zhang, Shujun; Okatan, Mahmut Baris

Compositional and charge disorder in ferroelectric relaxors lies at the heart of the unusual properties of these systems, such as aging and non-ergodicity, polarization rotations, and a host of temperature and field-driven phase transitions. However, much information about the field-dynamics of the polarization in the prototypical ferroelectric relaxor (1-x)Pb(Mg 1/3Nb 2/3)O 3-xPbTiO 3 (PMN-xPT) remains unprobed at the mesoscopic level. We use a piezoresponse force microscopy-based dynamic multimodal relaxation spectroscopy technique, enabling the study of ferroelectric switching and polarization relaxation at mesoscopic length scales, and carry out measurements on a PMN-0.28PT sample with minimal polishing. Results indicate that beyond amore » threshold DC bias the average relaxation increases as the system attempts to relax to the previous state. Phenomenological fitting reveals the presence of mesoscale heterogeneity in relaxation amplitudes and clearly suggests the presence of two distinct amplitudes. Independent component analysis reveals the presence of a disorder component of the relaxation, which is found to be strongly anti-correlated with the maximum piezoresponse at that location, suggesting smaller disorder effects where the polarization reversal is large and vice versa. The disorder in the relaxation amplitudes is postulated to arise from rhombohedral and field-induced tetragonal phase in the crystal, with each phase associated with its own relaxation amplitude. As a result, these studies highlight the crucial importance of the mixture of ferroelectric phases in the compositions in proximity of the morphotropic phase boundary in governing the local response and further highlight the ability of PFM voltage and time spectroscopies, in conjunction with big-data multivariate analyses, to locally map disorder and correlate it with parameters governing the dynamic behavior.« less

Multidimensional dynamic piezoresponse measurements. Unraveling local relaxation behavior in relaxor-ferroelectrics via big data

DOE PAGES

Vasudevan, Rama K.; Zhang, Shujun; Okatan, Mahmut Baris; ...

2015-08-19

Compositional and charge disorder in ferroelectric relaxors lies at the heart of the unusual properties of these systems, such as aging and non-ergodicity, polarization rotations, and a host of temperature and field-driven phase transitions. However, much information about the field-dynamics of the polarization in the prototypical ferroelectric relaxor (1-x)Pb(Mg 1/3Nb 2/3)O 3-xPbTiO 3 (PMN-xPT) remains unprobed at the mesoscopic level. We use a piezoresponse force microscopy-based dynamic multimodal relaxation spectroscopy technique, enabling the study of ferroelectric switching and polarization relaxation at mesoscopic length scales, and carry out measurements on a PMN-0.28PT sample with minimal polishing. Results indicate that beyond amore » threshold DC bias the average relaxation increases as the system attempts to relax to the previous state. Phenomenological fitting reveals the presence of mesoscale heterogeneity in relaxation amplitudes and clearly suggests the presence of two distinct amplitudes. Independent component analysis reveals the presence of a disorder component of the relaxation, which is found to be strongly anti-correlated with the maximum piezoresponse at that location, suggesting smaller disorder effects where the polarization reversal is large and vice versa. The disorder in the relaxation amplitudes is postulated to arise from rhombohedral and field-induced tetragonal phase in the crystal, with each phase associated with its own relaxation amplitude. As a result, these studies highlight the crucial importance of the mixture of ferroelectric phases in the compositions in proximity of the morphotropic phase boundary in governing the local response and further highlight the ability of PFM voltage and time spectroscopies, in conjunction with big-data multivariate analyses, to locally map disorder and correlate it with parameters governing the dynamic behavior.« less

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 in PbTiO3 nanocrystals and suppressing in BaTiO3 inclusions some transformations occurring in their bulk counterpart. The constructed phase maps open the possibility to calculate dielectric properties of strained PbTiO3 and BaTiO3 nanocrystals and ferroelectric nanocomposites comprising such crystallites.

Critical Role of Monoclinic Polarization Rotation in High-Performance Perovskite Piezoelectric Materials.

PubMed

Liu, Hui; Chen, Jun; Fan, Longlong; Ren, Yang; Pan, Zhao; Lalitha, K V; Rödel, Jürgen; Xing, Xianran

2017-07-07

High-performance piezoelectric materials constantly attract interest for both technological applications and fundamental research. The understanding of the origin of the high-performance piezoelectric property remains a challenge mainly due to the lack of direct experimental evidence. We perform in situ high-energy x-ray diffraction combined with 2D geometry scattering technology to reveal the underlying mechanism for the perovskite-type lead-based high-performance piezoelectric materials. The direct structural evidence reveals that the electric-field-driven continuous polarization rotation within the monoclinic plane plays a critical role to achieve the giant piezoelectric response. An intrinsic relationship between the crystal structure and piezoelectric performance in perovskite ferroelectrics has been established: A strong tendency of electric-field-driven polarization rotation generates peak piezoelectric performance and vice versa. Furthermore, the monoclinic M_{A} structure is the key feature to superior piezoelectric properties as compared to other structures such as monoclinic M_{B}, rhombohedral, and tetragonal. A high piezoelectric response originates from intrinsic lattice strain, but little from extrinsic domain switching. The present results will facilitate designing high-performance perovskite piezoelectric materials by enhancing the intrinsic lattice contribution with easy and continuous polarization rotation.

Multiferroicity in the generic easy-plane triangular lattice antiferromagnet RbFe(MoO4)2

NASA Astrophysics Data System (ADS)

White, J. S.; Niedermayer, Ch.; Gasparovic, G.; Broholm, C.; Park, J. M. S.; Shapiro, A. Ya.; Demianets, L. A.; Kenzelmann, M.

2013-08-01

RbFe(MoO4)2 is a quasi-two-dimensional (quasi-2D) triangular lattice antiferromagnet (TLA) that displays a zero-field magnetically driven multiferroic phase with a chiral spin structure. By inelastic neutron scattering, we determine quantitatively the spin Hamiltonian. We show that the easy-plane anisotropy is nearly 1/3 of the dominant spin exchange, making RbFe(MoO4)2 an excellent system for studying the physics of the model 2D easy-plane TLA. Our measurements demonstrate magnetic-field-induced fluctuations in this material to stabilize the generic finite-field phases of the 2D XY TLA. We further explain how Dzyaloshinskii-Moriya interactions can generate ferroelectricity only in the zero-field phase. Our conclusion is that multiferroicity in RbFe(MoO4)2, and its absence at high fields, results from the generic properties of the 2D XY TLA.

Ferroelectric nanoparticle-embedded sponge structure triboelectric generators

NASA Astrophysics Data System (ADS)

Park, Daehoon; Shin, Sung-Ho; Yoon, Ick-Jae; Nah, Junghyo

2018-05-01

We report high-performance triboelectric nanogenerators (TENGs) employing ferroelectric nanoparticles (NPs) embedded in a sponge structure. The ferroelectric BaTiO3 NPs inside the sponge structure play an important role in increasing surface charge density by polarized spontaneous dipoles, enabling the packaging of TENGs even with a minimal separation gap. Since the friction surfaces are encapsulated in the packaged device structure, it suffers negligible performance degradation even at a high relative humidity of 80%. The TENGs also demonstrated excellent mechanical durability due to the elasticity and flexibility of the sponge structure. Consequently, the TENGs can reliably harvest energy even under harsh conditions. The approach introduced here is a simple, effective, and reliable way to fabricate compact and packaged TENGs for potential applications in wearable energy-harvesting devices.

Non-resonant electromechanical energy harvesting using inter-ferroelectric phase transitions

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

Pérez Moyet, Richard; Rossetti, George A., E-mail: george.rossetti-jr@uconn.edu; Stace, Joseph

Non-resonant electromechanical energy harvesting is demonstrated under low frequency excitation (<50 Hz) using [110]{sub C}-poled lead indium niobate-lead magnesium niobate-lead titanate relaxor ferroelectric single crystals with compositions near the morphotropic phase boundary. The efficiency of power generation at the stress-induced phase transition between domain-engineered rhombohedral and orthorhombic ferroelectric states is as much as four times greater than is obtained in the linear piezoelectric regime under identical measurement conditions but during loading below the coercive stress of the phase change. The phase transition mode of electromechanical transduction holds potential for non-resonant energy harvesting from low-frequency vibrations and does not require mechanical frequencymore » up-conversion.« less

Ferroelectric nanoparticle-embedded sponge structure triboelectric generators.

PubMed

Park, Daehoon; Shin, Sung-Ho; Yoon, Ick-Jae; Nah, Junghyo

2018-05-04

We report high-performance triboelectric nanogenerators (TENGs) employing ferroelectric nanoparticles (NPs) embedded in a sponge structure. The ferroelectric BaTiO 3 NPs inside the sponge structure play an important role in increasing surface charge density by polarized spontaneous dipoles, enabling the packaging of TENGs even with a minimal separation gap. Since the friction surfaces are encapsulated in the packaged device structure, it suffers negligible performance degradation even at a high relative humidity of 80%. The TENGs also demonstrated excellent mechanical durability due to the elasticity and flexibility of the sponge structure. Consequently, the TENGs can reliably harvest energy even under harsh conditions. The approach introduced here is a simple, effective, and reliable way to fabricate compact and packaged TENGs for potential applications in wearable energy-harvesting devices.

Intrinsic Two-Dimensional Ferroelectricity with Dipole Locking

NASA Astrophysics Data System (ADS)

Xiao, Jun; Zhu, Hanyu; Wang, Ying; Feng, Wei; Hu, Yunxia; Dasgupta, Arvind; Han, Yimo; Wang, Yuan; Muller, David A.; Martin, Lane W.; Hu, PingAn; Zhang, Xiang

2018-06-01

Out-of-plane ferroelectricity with a high transition temperature in ultrathin films is important for the exploration of new domain physics and scaling down of memory devices. However, depolarizing electrostatic fields and interfacial chemical bonds can destroy this long-range polar order at two-dimensional (2D) limit. Here we report the experimental discovery of the locking between out-of-plane dipoles and in-plane lattice asymmetry in atomically thin In2Se3 crystals, a new stabilization mechanism leading to our observation of intrinsic 2D out-of-plane ferroelectricity. Through second harmonic generation spectroscopy and piezoresponse force microscopy, we found switching of out-of-plane electric polarization requires a flip of nonlinear optical polarization that corresponds to the inversion of in-plane lattice orientation. The polar order shows a very high transition temperature (˜700 K ) without the assistance of extrinsic screening. This finding of intrinsic 2D ferroelectricity resulting from dipole locking opens up possibilities to explore 2D multiferroic physics and develop ultrahigh density memory devices.

Fabrication of PVDF-TrFE based bilayered PbTiO{sub 3}/PVDF-TrFE films capacitor

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

Nurbaya, Z., E-mail: nurbayazainal@gmail.com; Razak School of Engineering and Advanced Technology, Universiti Teknologi Malaysia, 54100 Kuala Lumpur; Wahid, M. H.

2016-07-06

Development of high performance capacitor is reaching towards new generation where the ferroelectric materials take places as the active dielectric layer. The motivation of this study is to produce high capacitance device with long life cycle. This was configured by preparing bilayered films where lead titanate as an active dielectric layer and stacked with the top dielectric layer, poly(vinyledenefluoride-trifluoroethylene). Both of them are being referred that have one in common which is ferroelectric behavior. Therefore the combination of ceramic and polymer ferroelectric material could perform optimum dielectric characteristic for capacitor applications. The fabrication was done by simple sol-gel spin coatingmore » method that being varied at spinning speed property for polymer layers, whereas maintaining the ceramic layer. The characterization of PVDF-TrFE/PbTiO3 was performed according to metal-insulator-metal stacked capacitor measurement which includes structural, dielectric, and ferroelectric measurement.« less

Out-of-Plane Piezoelectricity and Ferroelectricity in Layered α-In2Se3 Nanoflakes.

PubMed

Zhou, Yu; Wu, Di; Zhu, Yihan; Cho, Yujin; He, Qing; Yang, Xiao; Herrera, Kevin; Chu, Zhaodong; Han, Yu; Downer, Michael C; Peng, Hailin; Lai, Keji

2017-09-13

Piezoelectric and ferroelectric properties in the two-dimensional (2D) limit are highly desired for nanoelectronic, electromechanical, and optoelectronic applications. Here we report the first experimental evidence of out-of-plane piezoelectricity and ferroelectricity in van der Waals layered α-In 2 Se 3 nanoflakes. The noncentrosymmetric R3m symmetry of the α-In 2 Se 3 samples is confirmed by scanning transmission electron microscopy, second-harmonic generation, and Raman spectroscopy measurements. Domains with opposite polarizations are visualized by piezo-response force microscopy. Single-point poling experiments suggest that the polarization is potentially switchable for α-In 2 Se 3 nanoflakes with thicknesses down to ∼10 nm. The piezotronic effect is demonstrated in two-terminal devices, where the Schottky barrier can be modulated by the strain-induced piezopotential. Our work on polar α-In 2 Se 3 , one of the model 2D piezoelectrics and ferroelectrics with simple crystal structures, shows its great potential in electronic and photonic applications.

Ferroelectricity-induced resistive switching in Pb(Zr0.52Ti0.48)O3/Pr0.7Ca0.3MnO3/Nb-doped SrTiO3 epitaxial heterostructure

NASA Astrophysics Data System (ADS)

Md. Sadaf, Sharif; Mostafa Bourim, El; Liu, Xinjun; Hasan Choudhury, Sakeb; Kim, Dong-Wook; Hwang, Hyunsang

2012-03-01

We investigated the effect of a ferroelectric Pb(Zr0.52Ti0.48)O3 (PZT) thin film on the generation of resistive switching in a stacked Pr0.7Ca0.3MnO3 (PCMO)/Nb-doped SrTiO3 (Nb:STO) heterostructure forming a p-n junction. To promote the ferroelectric effect, the thin PZT active layer was deposited on an epitaxially grown p-type PCMO film on a lattice-matched n-type Nb:STO single crystal. It was concluded that the observed resistive switching behavior in the all-perovskite Pt/PZT/PCMO/Nb:STO heterostructure was related to the modulation of PCMO/Nb:STO p-n junction's depletion width, which was caused either by the PZT ferroelectric polarization field effect, the electrochemical drift of oxygen ions under an electric field, or both simultaneously.

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.

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.

Investigations on the defect dipole induced pyroelectric current in multiferroic GdMnO3 system

NASA Astrophysics Data System (ADS)

Pal, A.; Dhana Sekhar, C.; Venimadhav, A.; Prellier, W.; Murugavel, P.

2018-01-01

Pyroelectric current measurements on the orthorhombic GdMnO3 polycrystalline sample are done to explore the intrinsic and extrinsic contributions. The measurements reveal poling temperature dependent pyrocurrent peaks at 20, 50 and 108 K. The pyrocurrent at 20 K and at 108 K are attributed to ferroelectric transition induced by the incommensurate spiral magnetic ordering of Mn spins and the release of trapped charges from the localized states, respectively. A detailed analysis on the broad pyrocurrent signal at 50 K suggests that it could be attributed to the thermally stimulated depolarization current effect due to the relaxation of defect dipoles induced by negatively charged Mn3+ ions and excess holes localized at Mn4+ sites. Importantly, the effect of the electric field due to the defect dipoles on the ferroelectric state is highlighted. The temperature dependent dielectric measurements under the magnetic field brought out the correlation between pyroelectric and dielectric properties. The influence of poling temperature dependent extrinsic effects on pyrocurrent suggests the choice of poling temperature on the study of polarization and the resultant multiferroicity in a spin-driven ferroelectric rare earth manganite system.

Imaging the Dynamics of the Ferroelectric Stripe Phase Near a Field-Driven Phase Transition in Bismuth Ferrite

NASA Astrophysics Data System (ADS)

Laanait, Nouamane; Li, Qian; Zhang, Zhan; Kalinin, Sergei

Electric field-driven phase transitions in multiferroic systems such as Bismuth Ferrite could potentially host interesting domain dynamics due to the coexistence of multiple order parameters. Structural imaging of these dynamics under a host of elastic and electric boundary conditions is therefore of interest. Here, we present X-ray diffraction microscopy (XDM) studies of the domain wall dynamics in a bismuth ferrite thin-film near the field-driven transition from rhombohedral to monoclinic (R to M). XDM is a novel full-field imaging technique that uses Bragg diffraction contrast to image structural configurations with sub-100nm lateral resolutions and fast acquisition times (milliseconds to seconds per image). We find that under electric fields 100 kV/cm, a bismuth ferrite thin-film (100 nm BiFeO3/DyScO3 (110)) undergoes a structural phase transition but that this new phase (M) is pinned by the preexisting ferroelectric/ferroelastic stripe phase (R). At higher fields ( 300 kV/cm), we observe unusually slow domain wall dynamics in the stripe phase, consisting of periodicity doubling, domain wall roughening and crowding. These observed ferroelastic domain wall spatial dynamics are weakly constrained by the crystal symmetry of the orthorhombic substrate but exhibit nonlinear dynamics more commonly associated with disordered nematic systems. This work was supported by the Eugene P. Wigner Fellowship program at Oak Ridge National Laboratory, a U.S. Department of Energy facility.

Combinatorial and High Throughput Discovery of High Temperature Piezoelectric Ceramics

DTIC Science & Technology

2011-10-10

the known candidate piezoelectric ferroelectric perovskites. Unlike most computational studies on crystal chemistry, where the starting point is some...studies on crystal chemistry, where the starting point is some form of electronic structure calculation, we use a data driven approach to initiate our...experimental measurements reported in the literature. Given that our models are based solely on crystal and electronic structure data and did not

Study of carrier energetics in ITO/P(VDF-TrFE)/pentacene/Au diode by using electric-field-induced optical second harmonic generation measurement and charge modulation spectroscopy

NASA Astrophysics Data System (ADS)

Otsuka, Takako; Taguchi, Dai; Manaka, Takaaki; Iwamoto, Mitsumasa

2017-02-01

By using electric-field-induced optical second harmonic generation (EFISHG) measurement and charge modulation spectroscopy (CMS), we studied carrier behavior and polarization reversal in ITO/ poly(vinylidene fluoride trifluoroethylene) (P(VDF-TrFE))/pentacene/Au diodes with a ferroelectric P(VDF-TrFE) layer in terms of carrier energetics. The current-voltage (I-V) characteristics of the diodes showed three-step polarization reversal in the dark. However, the I-V was totally different under illumination and exhibited two-step behavior. EFISHG probed the internal electric field in the pentacene layer and accounted for the polarization reversal change due to charge accumulation at the pentacene/P(VDF-TrFE) interface. CMS probed the related carrier energetics and indicated that exciton dissociation in pentacene molecular states governed carrier accumulation at the pentacene/ferroelectric interface, leading to different polarization reversal processes in the dark and under light illumination. Combining EFISHG measurement and CMS provides us a way to study carrier energetics that govern polarization reversal in ferroelectric P(VDF-TrFE)/pentacene diodes.

Manipulation of Dy-Mn coupling and ferrielectric phase diagram of DyMn2O5: The effect of Y substitution of Dy

NASA Astrophysics Data System (ADS)

Zhao, Z. Y.; Wang, Y. L.; Lin, L.; Liu, M. F.; Li, X.; Yan, Z. B.; Liu, J.-M.

2015-11-01

DyMn2O5 is an extraordinary example in the family of multiferroic manganites and it accommodates both the 4f and 3d magnetic ions with strong Dy-Mn (4f-3d) coupling. The electric polarization origin is believed to arise not only from the Mn spin interactions but also from the Dy-Mn coupling. Starting from proposed scenario on ferrielectricity in DyMn2O5 where the exchange-strictions associated with the Mn3+-Mn4+-Mn3+ blocks and Dy3+-Mn4+-Dy3+ blocks generate the two ferroelectric sublattices, we perform a set of characterizations on the structure, magnetism, and electric polarization of Dy1-xYxMn2O5 in order to investigate the roles of Dy-Mn coupling in manipulating the ferrielectricity. It is revealed that the non-magnetic Y substitution of Dy suppresses gradually the Dy3+ spin ordering and the Dy-Mn coupling. Consequently, the ferroelectric sublattice generated by the exchange striction associated with the Dy3+-Mn4+-Dy3+ blocks is destabilized, but the ferroelectric sublattice generated by the exchange striction associated with the Mn3+-Mn4+-Mn3+ blocks remains less perturbed, enabling the ferrielectricity-ferroelectricity transitions with the Y substitution. A phenomenological ferrielectric domain model is suggested to explain the polarization reversal induced by the Y substitution. The present work presents a possible scenario of the multiferroic mechanism in not only DyMn2O5 but probably also other RMn2O5 members with strong 4f-3d coupling.

Pulsed hybrid field emitter

DOEpatents

Sampayan, Stephen E.

1998-01-01

A hybrid emitter exploits the electric field created by a rapidly depoled ferroelectric material. Combining the emission properties of a planar thin film diamond emitter with a ferroelectric alleviates the present technological problems associated with both types of emitters and provides a robust, extremely long life, high current density cathode of the type required by emerging microwave power generation, accelerator technology and display applications. This new hybrid emitter is easy to fabricate and not susceptible to the same failures which plague microstructure field emitter technology. Local electrode geometries and electric field are determined independently from those for optimum transport and brightness preservation. Due to the large amount of surface charge created on the ferroelectric, the emitted electrons have significant energy, thus eliminating the requirement for specialized phosphors in emissive flat-panel displays.

Pulsed hybrid field emitter

DOEpatents

Sampayan, S.E.

1998-03-03

A hybrid emitter exploits the electric field created by a rapidly depoled ferroelectric material. Combining the emission properties of a planar thin film diamond emitter with a ferroelectric alleviates the present technological problems associated with both types of emitters and provides a robust, extremely long life, high current density cathode of the type required by emerging microwave power generation, accelerator technology and display applications. This new hybrid emitter is easy to fabricate and not susceptible to the same failures which plague microstructure field emitter technology. Local electrode geometries and electric field are determined independently from those for optimum transport and brightness preservation. Due to the large amount of surface charge created on the ferroelectric, the emitted electrons have significant energy, thus eliminating the requirement for specialized phosphors in emissive flat-panel displays. 11 figs.

Novel Photovoltaic Devices Using Ferroelectric Material and Colloidal Quantum Dots

NASA Astrophysics Data System (ADS)

Paik, Young Hun

As the global concern for the financial and environmental costs of traditional energy resources increases, research on renewable energy, most notably solar energy, has taken center stage. Many alternative photovoltaic (PV) technologies for 'the next generation solar cell' have been extensively studied to overcome the Shockley-Queisser 31% efficiency limit as well as tackle the efficiency vs. cost issues. This dissertation focuses on the novel photovoltaic mechanism for the next generation solar cells using two inorganic nanomaterials, nanocrystal quantum dots and ferroelectric nanoparticles. Lead zirconate titanate (PZT) materials are widely studied and easy to synthesize using solution based chemistry. One of the fascinating properties of the PZT material is a Bulk Photovoltaic effect (BPVE). This property has been spotlighted because it can produce very high open circuit voltage regardless of the electrical bandgap of the materials. However, the poor optical absorption of the PZT materials and the required high temperature to form the ferroelectric crystalline structure have been obstacles to fabricate efficient photovoltaic devices. Colloidal quantum dots also have fascinating optical and electrical properties such as tailored absorption spectrum, capability of the bandgap engineering due to the wide range of material selection and quantum confinement, and very efficient carrier dynamics called multiple exciton generations. In order to utilize these properties, many researchers have put numerous efforts in colloidal quantum dot photovoltaic research and there has been remarkable progress in the past decade. However, several drawbacks are still remaining to achieve highly efficient photovoltaic device. Traps created on the large surface area, low carrier mobility, and lower open circuit voltage while increasing the absorption of the solar spectrum is main issues of the nanocrystal based photovoltaic effect. To address these issues and to take the advantages of the two materials, this dissertation focused on material synthesis for low cost solution process for both materials, fabrication of various device structures and electrical/optical characterization to understand the underlying physics. We successfully demonstrated lead sulfide quantum dots (PbS QDs) and lead zirconate titanate nanoparticles (PZT NPs) in an aqueous solution and fabricated a photosensitive device. Solution based low-temperature process was used to fabricate a PbS QD and a PZT NP device. We exhibited a superior photoresponse and ferroelectric photovoltaic properties with the novel PZT NP device and studied the physics on domain wall effect and internal polarity effect. PZT NP was mainly investigated because PZT NP device is the first report as a photosensitive device with a successful property demonstration, as we know of. PZT's crystalline structure and the size of the nanocrystals were studied using X-ray diffraction and TEM (Transmission electron microscopy) respectively. We observed < 100 nm of PZT NPs and this result matched with DLS (dynamic light scattering) measurement. We fabricated ferroelectric devices using the PZT NPs for the various optical and electrical characterizations and verified ferroelectric properties including ferroelectric hysteresis loop. We also observed a typical ferroelectric photovoltaic effect from a PZT NP based device which was fabricated on an ITO substrate. We synthesized colloidal quantum dots (CQD) with the inexpensive soluble process. Fabricated PbS QD was used for the hybrid device with PZT thin films. J-V measured and the result shows superior open circuit voltage characteristics compared to conventional PbS QD PV devices, and resulting the improvement of the solar cell efficiency. This Ferroelectrics and Quantum Dots (FE-QDs) device also the first trial and the success as we know of.

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 polymer ranging from 1D supramolecular structures to true 3D coordination polymers is covered in Chapter 4. The observation of a new 2D Kagome lattice and unique layered perovskite-type bismuth-based coordination polymers and their photoluminescence properties is the focus of Chapter 5. In chapters 6 and 7, a successful approach to implement our novel hybrid strategy for synthesizing enantiomerically pure single crystals consisting of Second Order Jahn Teller (SOJT)-possessing main group metal cations, specifically bismuth and tin, and homochiral ligands or unsymmetric ligands is discussed. The new MOMs with polar space groups exhibit second harmonic generation and have potential for ferroelectric properties.

Strong second harmonic generation in two-dimensional ferroelectric IV-monochalcogenides

NASA Astrophysics Data System (ADS)

Panday, Suman Raj; Fregoso, Benjamin M.

2017-11-01

The two-dimensional ferroelectrics GeS, GeSe, SnS and SnSe are expected to have large spontaneous in-plane electric polarization and enhanced shift-current response. Using density functional methods, we show that these materials also exhibit the largest effective second harmonic generation reported so far. It can reach magnitudes up to 10~nm~V-1 which is about an order of magnitude larger than that of prototypical GaAs. To rationalize this result we model the optical response with a simple one-dimensional two-band model along the spontaneous polarization direction. Within this model the second-harmonic generation tensor is proportional to the shift-current response tensor. The large shift current and second harmonic responses of GeS, GeSe, SnS and SnSe make them promising non-linear materials for optoelectronic applications.

Polarization induced self-doping in epitaxial Pb(Zr0.20Ti0.80)O3 thin films

PubMed Central

Pintilie, Lucian; Ghica, Corneliu; Teodorescu, Cristian Mihail; Pintilie, Ioana; Chirila, Cristina; Pasuk, Iuliana; Trupina, Lucian; Hrib, Luminita; Boni, Andra Georgia; Georgiana Apostol, Nicoleta; Abramiuc, Laura Elena; Negrea, Raluca; Stefan, Mariana; Ghica, Daniela

2015-01-01

The compensation of the depolarization field in ferroelectric layers requires the presence of a suitable amount of charges able to follow any variation of the ferroelectric polarization. These can be free carriers or charged defects located in the ferroelectric material or free carriers coming from the electrodes. Here we show that a self-doping phenomenon occurs in epitaxial, tetragonal ferroelectric films of Pb(Zr0.2Ti0.8)O3, consisting in generation of point defects (vacancies) acting as donors/acceptors. These are introducing free carriers that partly compensate the depolarization field occurring in the film. It is found that the concentration of the free carriers introduced by self-doping increases with decreasing the thickness of the ferroelectric layer, reaching values of the order of 1026 m−3 for 10 nm thick films. One the other hand, microscopic investigations show that, for thicknesses higher than 50 nm, the 2O/(Ti+Zr+Pb) atomic ratio increases with the thickness of the layers. These results suggest that the ratio between the oxygen and cation vacancies varies with the thickness of the layer in such a way that the net free carrier density is sufficient to efficiently compensate the depolarization field and to preserve the outward direction of the polarization. PMID:26446442

Low-energy electron diffraction from ferroelectric surfaces: Dead layers and surface dipoles in clean Pb(Zr ,Ti )O 3(001 )

NASA Astrophysics Data System (ADS)

Teodorescu, Cristian M.; Pintilie, Lucian; Apostol, Nicoleta G.; Costescu, Ruxandra M.; Lungu, George A.; Hrib, LuminiÅ£a.; Trupinǎ, Lucian; Tǎnase, Liviu C.; Bucur, Ioana C.; Bocîrnea, Amelia E.

2017-09-01

The positions of the low energy electron diffraction (LEED) spots from ferroelectric single crystal films depend on its polarization state, due to electric fields generated outside of the sample. One may derive the surface potential energy, yielding the depth where the mobile charge carriers compensating the depolarization field are located (δ ). On ferroelectric Pb (Zr ,Ti ) O3 (001) samples, surface potential energies are between 6.7 and 10.6 eV, and δ values are unusually low, in the range of 1.8 ±0.4 Å . When δ is introduced in the values of the band bending inside the ferroelectric, a considerably lower value of the dielectric constant and/or of the polarization near the surface than their bulk values is obtained, evidencing either that the intrinsic `dielectric constant' of the material has this lower value or the existence of a `dead layer' at the free surface of clean ferroelectric films. The inwards polarization of these films is explained in the framework of the present considerations by the formation of an electron sheet on the surface. Possible explanations are suggested for discrepancies between the values found for surface potential energies from LEED experiments and those derived from the transition between mirror electron microscopy and low energy electron microscopy.

Electric field driven evolution of topological domain structure in hexagonal manganites

NASA Astrophysics Data System (ADS)

Yang, K. L.; Zhang, Y.; Zheng, S. H.; Lin, L.; Yan, Z. B.; Liu, J.-M.; Cheong, S.-W.

2017-10-01

Controlling and manipulating the topological state represents an important topic in condensed matters for both fundamental researches and applications. In this work, we focus on the evolution of a real-space topological domain structure in hexagonal manganites driven by electric field, using the analytical and numerical calculations based on the Ginzburg-Landau theory. It is revealed that the electric field drives a transition of the topological domain structure from the type-I pattern to the type-II one. In particular, it is identified that a high electric field can enforce the two antiphase-plus-ferroelectric (AP +FE ) domain walls with Δ Φ =π /3 to approach each other and to merge into one domain wall with Δ Φ = 2 π /3 eventually if the electric field is sufficiently high, where Δ Φ is the difference in the trimerization phase between two neighboring domains. Our simulations also reveal that the vortex cores of the topological structure can be disabled at a sufficiently high critical electric field by suppressing the structural trimerization therein, beyond which the vortex core region is replaced by a single ferroelectric domain without structural trimerization (Q = 0 ). Our results provide a stimulating reference for understanding the manipulation of real-space topological domain structure in hexagonal manganites.

Multiple caloric effects in (Ba0.865Ca0.135Zr0.1089Ti0.8811Fe0.01)O3 ferroelectric ceramic

NASA Astrophysics Data System (ADS)

Patel, Satyanarayan; Chauhan, Aditya; Vaish, Rahul

2015-07-01

Multiple caloric effects have been investigated for Fe-doped bulk (Ba0.865Ca0.135Zr0.1089Ti0.8811Fe0.01)O3 (BCZTO-Fe) ferroelectric ceramic. Indirect predictions were made using Maxwell's relations in conjunction with data from experimental observations. It was revealed that bulk BCZTO-Fe has huge untapped potential for solid-state refrigeration. A peak electrocaloric effect of 0.45 K (347 K) was predicted for 0-3 kV.mm-1 electric field, significantly higher than other BCZTO based materials. A maximum elastocaloric cooling of 1.4 K (298 K) was achieved for applied stress of 0-200 MPa. Finally, an unforeseen component of electric field driven caloric effect has been reported as inverse piezocaloric effect, with a maximum temperature change of 0.28 K (298 K).

Magnetic structure driven ferroelectricity and large magnetoelectric coupling in antiferromagnet Co4Nb2O9

NASA Astrophysics Data System (ADS)

Srivastava, P.; Chaudhary, S.; Maurya, V.; Saha, J.; Kaushik, S. D.; Siruguri, V.; Patnaik, S.

2018-05-01

Synthesis and extensive structural, pyroelectric, magnetic, dielectric and magneto-electric characterizations are reported for polycrystalline Co4Nb2O9 towards unraveling the multiferroic ground state. Magnetic measurements confirm that Co4Nb2O9 becomes an anti-ferromagnet at around 28 K. Associated with the magnetic phase transition, a sharp peak in pyroelectric current indicates the appearance of strong magneto-electric coupling below Neel temperature (TN) along with large coupling constant upto 17.8 μC/m2T. Using temperature oscillation technique, we establish Co4Nb2O9 to be a genuine multiferroic with spontaneous electric polarization in the anti-ferromagnetic state in the absence of magnetic field poling. This is in agreement with our low temperature neutron diffraction studies that show the magnetic structure of Co4Nb2O9 to be that of a non-collinear anti-ferromagnet with ferroelectric ground state.

Composition-driven magnetic and structural phase transitions in Bi1-xPrxFe1-xMnxO3 multiferroics

NASA Astrophysics Data System (ADS)

Khomchenko, V. A.; Ivanov, M. S.; Karpinsky, D. V.; Paixão, J. A.

2017-09-01

Magnetic ferroelectrics continue to attract much attention as promising multifunctional materials. Among them, BiFeO3 is distinguished by exceptionally high transition temperatures and, thus, is considered as a prototype room-temperature multiferroic. Since its properties are known to be strongly affected by chemical substitution, recognition of the doping-related factors determining the multiferroic behavior of the material would pave the way towards designing the structures with enhanced magnetoelectric functionality. In this paper, we report on the crystal structure and magnetic and local ferroelectric properties of the Bi1-xPrxFe1-xMnxO3 (x ≤ 0.3) compounds prepared by a solid state reaction method. The polar R3c structure specific to the parent BiFeO3 has been found to be unstable with respect to doping for x ≳ 0.1. Depending on the Pr/Mn concentration, either the antipolar PbZrO3-like or nonpolar PrMnO3-type structure can be observed. It has been shown that the non-ferroelectric compounds are weak ferromagnetic with the remanent/spontaneous magnetization linearly decreasing with an increase in x. The samples containing the polar R3c phase exhibit a mixed antiferromagnetic/weak ferromagnetic behavior. The origin of the magnetic phase separation taking place in the ferroelectric phase is discussed as related to the local, doping-introduced structural heterogeneity contributing to the suppression of the cycloidal antiferromagnetic ordering characteristic of the pure BiFeO3.

Ferroelectricity in CaTiO3 Single Crystal Surfaces and Thin Films and Probed by Nonlinear Optics and Raman Spectroscopy

NASA Astrophysics Data System (ADS)

Vlahos, Eftihia; Lummen, Tom; Haislmaier, Ryan; Denev, Sava; Brooks, Charles; Biegalski, Michael; Schlom, Darrell; Eklund, Carl-Johan; Rabe, Karin; Fennie, Craig; Gopalan, Venkatraman

2011-03-01

Bulk CaTi O3 has a centrosymmetric point group and is not polar or ferroelectric. However, we present surprising results that show highly regular polar domains in single crystals of CaTi O3 . Confocal Second Harmonic Generation (SHG) and Raman imaging studies were carried out on perovskite CaTi O3 crystal surfaces. They reveal large, crystallographic polar domains at room temperature, with in-plane polarization components delineated by twin walls. SHG analysis indicates that the highest symmetry of the polar surface is m (space group P c) with polarization in the m plane. In addition, we present results of the polar domain structure imaged before and after the application of an external electric field. Finally, we present the SHG studies of CaTi O3 thin films grown using reactive Molecular Beam Epitaxy (MBE); these films are predicted by theory to be ferroelectric and are shown experimentally, both with SHG and in-plane dielectric measurements, to be ferroelectric for temperatures less than ~ 150 K with group symmetry mm2.

Strain-induced tetragonal distortions and multiferroic properties in polycrystalline Sr1 -xB axMn O3 (x =0.43 -0.45 ) perovskites

NASA Astrophysics Data System (ADS)

Somaily, H.; Kolesnik, S.; Mais, J.; Brown, D.; Chapagain, K.; Dabrowski, B.; Chmaissem, O.

2018-05-01

We report the structure-property phase diagram of unique single-ion type-1 multiferroic pseudocubic Sr1 -xB axMn O3 perovskites. Employing a specially designed multistep reduction-oxidation synthesis technique, we have synthesized Sr1 -xB axMn O3 compositions in their polycrystalline form with a significantly extended Ba solubility limit that is only rivaled by a very limited number of crystals and thin films grown under nonequilibrium conditions. Understanding the multiferroic interplay with structure in Sr1 -xB axMn O3 is of great importance as it opens the door wide to the development of newer materials from the parent (A A' ) (B B' ) O3 system with enhanced properties. To this end, using a combination of time-of-flight neutron and synchrotron x-ray scattering techniques, we determined the exact structures and quantified the Mn and oxygen polar distortions above and below the ferroelectric Curie temperature TC and the Néel temperature TN. In its ferroelectric state, the system crystalizes in the noncentrosymmetric tetragonal P 4 m m space group, which gives rise to a large electric dipole moment Ps, in the z direction, of 18.4 and 29.5 μ C /c m2 for x =0.43 and 0.45, respectively. The two independently driven ferroelectric and magnetic order parameters are single-handedly accommodated by the Mn sublattice leading to a novel strain-assisted multiferroic behavior in agreement with many theoretical predictions. Our neutron diffraction results demonstrate the large and tunable suppression of the ferroelectric order at the onset of AFM ordering and confirm the coexistence and strong coupling of the two ferroic orders below TN. The refined magnetic moments confirm the strong covalent bonding between Mn and the oxygen anions, which is necessary for stabilizing the ferroelectric phase.

Non-linear optical probing of strain-enabled ferroelectricity in CaTiO3 thin films

NASA Astrophysics Data System (ADS)

Vlahos, Eftihia; Brooks, Charles; Ecklund, Carl Johan; Biegalski, Mike; Rabe, Karin; Schlom, Darrell; Gopalan, Venkatraman

2010-03-01

First principles calculations predict CaTiO3, under tensile strain, to become ferroelectric with a spontaneous polarization of up to 0.5 C/m^2. Comparative second harmonic generation (SHG) studies of a series of strained CaTiO3 thin films were undertaken in order to determine their transition temperature and point group symmetry. The epitaxial strain ranged from -1.7% to 3.3%. Symmetry analysis of the SHG polar plots confirms that for the samples under tensile strain, the polarization is along the <110>p directions and the point group of the ferroelectric phase is mm2. SHG ``hysteresis'' loops were also obtained; these show clear switching. The experimental results are in excellent agreement with the first principles calculations predictions, and low temperature dielectric measurements that were performed on the same samples.

Feasibility study of ferromagnetic/ferroelectric films for enhanced microwave devices

NASA Technical Reports Server (NTRS)

Ijiri, Yumi

2005-01-01

This report summarizes exploratory work conducted to assess the feasibility of ferromagnetic/ferroelectric films for next-generation microwave devices. From literature review, it is established that while an increasing number of ferroelectric/ferromagnetic composites are being investigated, a number have transition temperatures that are too low and structures that are not robust enough for low cost, room temperature antenna arrays. On the other hand, several promising systems are identified, including the multiferroic BiFeO3 and a composite system of Ba/SrTiO3 and a related perovskite manganite. It is suggested that when the NASA pulsed laser deposition chamber is fully operational, thin films of these systems be investigated. In preparation for such work, we have reconfirmed several structural features of an existing Ba/SrTiO3 film using the x-ray diffractometer at Oberlin College.

Molecular dynamics simulations of ferroelectric domain formation by oxygen vacancy

NASA Astrophysics Data System (ADS)

Zhu, Lin; You, Jeong Ho; Chen, Jinghong; Yeo, Changdong

2018-05-01

An oxygen vacancy, known to be detrimental to ferroelectric properties, has been investigated numerically for the potential uses to control ferroelectric domains in films using molecular dynamics simulations based on the first-principles effective Hamiltonian. As an electron donor, an oxygen vacancy generates inhomogeneous electrostatic and displacement fields which impose preferred polarization directions near the oxygen vacancy. When the oxygen vacancies are placed at the top and bottom interfaces, the out-of-plane polarizations are locally developed near the interfaces in the directions away from the interfaces. These polarizations from the interfaces are in opposite directions so that the overall out-of-plane polarization becomes significantly reduced. In the middle of the films, the in-plane domains are formed with containing 90° a 1/a 2 domain walls and the films are polarized along the [1 1 0] direction even when no electric field is applied. With oxygen vacancies placed at the top interface only, the films exhibit asymmetric hysteresis loops, confirming that the oxygen vacancies are one of the possible sources of ferroelectric imprint. It has been qualitatively demonstrated that the domain structures in the imprint films can be turned on and off by controlling an external field along the thickness direction. This study shows qualitatively that the oxygen vacancies can be utilized for tuning ferroelectric domain structures in films.

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

Characteristics Of Ferroelectric Logic Gates Using a Spice-Based Model

NASA Technical Reports Server (NTRS)

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

2005-01-01

A SPICE-based model of an n-channel ferroelectric field effect transistor has been developed based on both theoretical and empirical data. This model was used to generate the I-V characteristic of several logic gates. The use of ferroelectric field effect transistors in memory circuits is being developed by several organizations. The use of FFETs in other circuits, both analog and digital needs to be better understood. The ability of FFETs to have different characteristics depending on the initial polarization can be used to create logic gates. These gates can have properties not available to standard CMOS logic gates, such as memory, reconfigurability and memory. This paper investigates basic properties of FFET logic gates. It models FFET inverter, NAND gate and multi-input NAND gate. The I-V characteristics of the gates are presented as well as transfer characteristics and timing. The model used is a SPICE-based model developed from empirical data from actual Ferroelectric transistors. It simulates all major characteristics of the ferroelectric transistor, including polarization, hysteresis and decay. Contrasts are made of the differences between FFET logic gates and CMOS logic gates. FFET parameters are varied to show the effect on the overall gate. A recodigurable gate is investigated which is not possible with CMOS circuits. The paper concludes that FFETs can be used in logic gates and have several advantages over standard CMOS gates.

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.

Investigation about relationships between the symmetries of ferroelectric crystal Ca0.28Ba0.72Nb2O6 and second-harmonic patterns

NASA Astrophysics Data System (ADS)

Xu, Tianxiang; Yu, Haohai; Zhang, Huaijin; Wang, Jiyang

2015-08-01

The broadband quasi-phase matching (QPM) process in a uniaxial ferroelectric crystal Ca0.28Ba0.72Nb2O6 (CBN-28) was demonstrated with the second-harmonic wavelength range from 450 nm to 650 nm, and the relationship between the symmetries of CBN-28 and the second-harmonic patterns was experimentally and theoretically investigated based on the random anti-parallel domains in the crystal and QPM conditions. The dependences of frequency-doubled patterns on the wavelength and anisotropy of the nonlinear crystal were also studied, and the frequency-doubled photons were found to be trapped on circles. By analyzing the light-matter interacting Hamiltonians, the trapping force for second-harmonic photons was found to be centripetal and tunable by the fundamental lasers, and the variation tendencies of the rotational velocity of second-harmonic generation photons could also be predicated. The results indicate that the CBN-28 ferroelectric crystal is a promising nonlinear optical material for the generation of broadband frequency-doubled waves, and the analysis on centripetal force based on the interaction Hamiltonians may provide a novel recognition for the investigation of QPM process to be further studied.

Enhancement of local piezoelectric properties of a perforated ferroelectric thin film visualized via piezoresponse force microscopy

NASA Astrophysics Data System (ADS)

Ivanov, M. S.; Sherstyuk, N. E.; Mishina, E. D.; Khomchenko, V. A.; Tselev, A.; Mukhortov, V. M.; Paixão, J. A.; Kholkin, A. L.

2017-10-01

The local piezoresponse in a Ba0.8Sr0.2TiO3 epitaxial ferroelectric film perforated by cylindrical channels has been investigated experimentally by means of piezoresponse force microscopy (PFM). A large enhancement of the effective values for both lateral and vertical components of piezoelectric tensor was experimentally detected in the perforated film as compared to non-perforated structure—by a factor of 8 for the lateral and by a factor 2 for the vertical piezoresponse. This result is consistent with the previously reported enhancement of the optical second harmonic generation over perforated films observed in macroscopic experiments. We assume that a possible mechanism for the increased PFM response is due to reduction of stress and clamping in the film imposed by the substrate. The obtained insight is critical for understanding nanoscale piezo- and ferroelectric responses in photonic crystals fabricated by focused ion beam milling.

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.

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.

Selective Deposition of Silver Oxide on Single-Domain Ferroelectric Nanoplates and Their Efficient Visible-Light Photoactivity.

PubMed

Chen, Fang; Ren, Zhaohui; Gong, Siyu; Li, Xiang; Shen, Ge; Han, Gaorong

2016-08-16

In this work, single-crystal and single-domain PbTiO3 nanoplates are employed as substrates to prepare Ag2 O/PbTiO3 composite materials through a photodeposition method. It is revealed that silver oxide nanocrystals with an average size of 63 nm are selectively deposited on the positive polar surface of the ferroelectric substrate. The possible mechanism leading to the formation of silver oxide is that silver ions are first reduced to silver and then oxidized by oxygen generation. The composite shows an efficient photodegradation performance towards rhodamine B (RhB) and methyl orange (MO) under visible-light irradiation. Such highly efficient photoactivity can be attributed to the ferroelectric polarization effect of the substrate, which promotes the separation of photogenerated electrons and holes at the interface. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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.

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

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

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.

Optical second harmonic images of 90 deg domain structure in BaTiO3 and periodically inverted antiparallel domains in LiTaO3

NASA Astrophysics Data System (ADS)

Uesu, Y.; Kurimura, S.; Yamamoto, Y.

1995-04-01

Applied is a microscope to observations of 90 deg ferroelectric domain structure in BaTiO3 and inverted periodically are ferroelectric domains in LiTaO3. It is founded that the second harmonic generation microscope gives information which cannot be obtained by ordinary optical microscopes. The developed nonlinear optical microscope builds two dimensional second harmonic image of a specimen with inhomogenous distribution of d(sub ijk) and applied the microscope to observations of inhomogeneity in some nonlinear-optical organic microcrystals.

Strain-Driven Nanoscale Phase Competition near the Antipolar-Nonpolar Phase Boundary in Bi0.7La0.3FeO3 Thin Films.

PubMed

Dedon, Liv R; Chen, Zuhuang; Gao, Ran; Qi, Yajun; Arenholz, Elke; Martin, Lane W

2018-05-02

Complex-oxide materials tuned to be near phase boundaries via chemistry/composition, temperature, pressure, etc. are known to exhibit large susceptibilities. Here, we observe a strain-driven nanoscale phase competition in epitaxially constrained Bi 0.7 La 0.3 FeO 3 thin films near the antipolar-nonpolar phase boundary and explore the evolution of the structural, dielectric, (anti)ferroelectric, and magnetic properties with strain. We find that compressive and tensile strains can stabilize an antipolar PbZrO 3 -like Pbam phase and a nonpolar Pnma orthorhombic phase, respectively. Heterostructures grown with little to no strain exhibit a self-assembled nanoscale mixture of the two orthorhombic phases, wherein the relative fraction of each phase can be modified with film thickness. Subsequent investigation of the dielectric and (anti)ferroelectric properties reveals an electric-field-driven phase transformation from the nonpolar phase to the antipolar phase. X-ray linear dichroism reveals that the antiferromagnetic-spin axes can be effectively modified by the strain-induced phase transition. This evolution of antiferromagnetic-spin axes can be leveraged in exchange coupling between the antiferromagnetic Bi 0.7 La 0.3 FeO 3 and a ferromagnetic Co 0.9 Fe 0.1 layer to tune the ferromagnetic easy axis of the Co 0.9 Fe 0.1 . These results demonstrate that besides chemical alloying, epitaxial strain is an alternative and effective way to modify subtle phase relations and tune physical properties in rare earth-alloyed BiFeO 3 . Furthermore, the observation of antiferroelectric-antiferromagnetic properties in the Pbam Bi 0.7 La 0.3 FeO 3 phase could be of significant scientific interest and great potential in magnetoelectric devices because of its dual antiferroic nature.

Recent Advances in the Development of Ferroelectric Generators

DTIC Science & Technology

2013-06-01

multi FEG- VIG oscillator operating at only 20% maximum voltage (Fig. 4) can generate 10s of kV/m fields at 3 m. The waveform in Fig. 5 was produced...Figure 5. Waveforms produced by a Radiance multi-FEG array driving a VIG (Courtesy of Zachary Roberts, Radiance). This requires large antennas to

A new non-destructive readout by using photo-recovered surface potential contrast

NASA Astrophysics Data System (ADS)

Wang, Le; Jin, Kui-Juan; Gu, Jun-Xing; Ma, Chao; He, Xu; Zhang, Jiandi; Wang, Can; Feng, Yu; Wan, Qian; Shi, Jin-An; Gu, Lin; He, Meng; Lu, Hui-Bin; Yang, Guo-Zhen

2014-11-01

Ferroelectric random access memory is still challenging in the feature of combination of room temperature stability, non-destructive readout and high intensity storage. As a non-contact and non-destructive information readout method, surface potential has never been paid enough attention because of the unavoidable decay of the surface potential contrast between oppositely polarized domains. That is mainly due to the recombination of the surface movable charges around the domain walls. Here, by introducing a laser beam into the combination of piezoresponse force microscopy and Kelvin probe force microscopy, we demonstrate that the surface potential contrast of BiFeO3 films can be recovered under light illumination. The recovering mechanism is understood based on the redistribution of the photo-induced charges driven by the internal electric field. Furthermore, we have created a 12-cell memory pattern based on BiFeO3 films to show the feasibility of such photo-assisted non-volatile and non-destructive readout of the ferroelectric memory.

Investigation about relationships between the symmetries of ferroelectric crystal Ca{sub 0.28}Ba{sub 0.72}Nb{sub 2}O{sub 6} and second-harmonic patterns

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

Xu, Tianxiang; Yu, Haohai, E-mail: haohaiyu@sdu.edu.cn; Zhang, Huaijin, E-mail: huaijinzhang@sdu.edu.cn

2015-08-07

The broadband quasi-phase matching (QPM) process in a uniaxial ferroelectric crystal Ca{sub 0.28}Ba{sub 0.72}Nb{sub 2}O{sub 6} (CBN-28) was demonstrated with the second-harmonic wavelength range from 450 nm to 650 nm, and the relationship between the symmetries of CBN-28 and the second-harmonic patterns was experimentally and theoretically investigated based on the random anti-parallel domains in the crystal and QPM conditions. The dependences of frequency-doubled patterns on the wavelength and anisotropy of the nonlinear crystal were also studied, and the frequency-doubled photons were found to be trapped on circles. By analyzing the light-matter interacting Hamiltonians, the trapping force for second-harmonic photons was found tomore » be centripetal and tunable by the fundamental lasers, and the variation tendencies of the rotational velocity of second-harmonic generation photons could also be predicated. The results indicate that the CBN-28 ferroelectric crystal is a promising nonlinear optical material for the generation of broadband frequency-doubled waves, and the analysis on centripetal force based on the interaction Hamiltonians may provide a novel recognition for the investigation of QPM process to be further studied.« less

Relaxor ferroelectricity, ferromagnetic and optical second harmonic properties in lanthanum lithium niobate (La0.05Li0.85NbO3) nanoparticles

NASA Astrophysics Data System (ADS)

Díaz-Moreno, Carlos A.; Ding, Yu; Li, Chunqiang; Portelles, Jorge; Heiras, J.; Hurtado-Macias, A.; Farias, J. R.; González-Hernández, J.; Yacamán, M. J.; López, Jorge

2017-07-01

Relaxor ferroelectricity, ferromagnetism and Second Harmonic Generation properties were founded and studied as a function of a reduction heat treatment at 650 °C in a Ar-5%H2 atmosphere in stoichiometric La0.05Li0.85NbO3 nanoparticles of 40 nm. A diffuse dielectric anomaly related with relaxor behavior from 25 °C to 800 °C in a frequency range from 100 Hz to 1 MHz was founded. It also shows ferromagnetic anhysterestic type and ferroelectric hysteresis loops at room temperature with a magnetic spin remnant of 2.5 × 10-3 emu/g and polarization saturation of 0.235 μC/cm2, remnant polarization of 0.141 μC/cm2, coercive field of 1.35 kV/cm, respectively. It shows very good second harmonic generation signal at 450 nm and 500 nm. High Resolution Transmission Electron Microscopy, X-ray Photoelectron Spectroscopy and Raman spectroscopy, indicate an ABO3 perovskite structure, new electronic binding energy structure for La (5s, 4d), Li (1s), Nb (4s, 3d, 4p) and oxygen (1s, 2s) and new vibrations modes on octahedron NbO6 related to multiferroic single phase nanoparticles, respectively.

Preface to ISIF 2009 special issue of Journal of Applied Physics : science and technology of integrated functionalities.

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

Auciello, O.; Dey, S.; Paz de Araujo, C.

2011-05-01

The science and technology of ferroelectric thin films and their applications have attracted many researchers and experienced tremendous progress in the past 20 years. The recent worldwide increase in commercial applications of ferroelectric devices such as smart cards based on nonvolatile ferroelectric random access memories is a symbol of both the maturity and the acceptance of the technology. The 21st International Symposium on Integrated Ferroelectrics (ISIF 2009), held on September 22 to October 2, 2009 in Colorado Springs, CO, provided a forum for the academic and national laboratories research community and industry to present and share their new findings, achievements,more » and opinions on integrated ferroelectrics and their applications. The International Symposium on Integrated Ferroelectrics hosted the ISIF 2009. This was the first year where the ISIF held the conference in its new format under the name of International Symposium on Integrated Functionalities. The General Chairs of the ISIF in consultation with the Advisory Board and the ISIF community decided to revise the focus of the conference in order to broaden the scope to the science and technology of multifunctional materials and devices. This decision was taken in view that a new paradigm in materials, materials integration, and devices is emerging with a view to the development of a new generation of micro- and nanoscale multifunctional devices. The program included three plenary presentations on diverse topics such as 'The Role of Nonvolatile Memory in Ubiquitous Computing,' 'Ferroelectrics and High Density Memory Technology,' 'Nanoscale Ferroelectrics and Interfaces: Size Effects,' four tutorial lectures on diverse topics, such as 'Magnetic Memory Applications,' 'Ferroelectrics and Ferroelectric Devices,' 'Challenges for High-K Dielectrics on High Mobility Channels,' 'Solar Cell Materials,' one poster session, and eight oral sessions. Thanks to the great efforts made by the ISIF organization committee and the session chairs, the conference successfully achieved its objectives and the work presented reflected very well the most recent advances of integrated ferroelectrics and their applications, as well as advances in other areas related to the new theme of Integrated Functionalities. Many aspects of ferroelectric, piezoelectric, high-K dielectric, magnetic, and phase change materials, including the science and technology of these materials in thin film form, integration with other thin film materials (metals or oxide electrodes), and fabrication of micro- and nanostructures based on these heterostructure layers, and device architecture and physics, were addressed from the experimental point of view. Work on theory and computer simulations of the mentioned materials and devices were discussed also with a view to the promising applications to multifunctional devices. In addition, the ISIF 2009 featured discussions of alternative nonvolatile memory concepts and materials, such as phase change memories, research on multiferroics and magnetoelectric materials, ferroelectric photovoltaics, and new directions on the science of perovskites such as biomolecular/polarizable interfaces, and bio-ferroelectric and other oxide interfaces. Following the standard submission and peer review process of Journal of Applied Physics, the selected papers presented in ISIF 2009 in Colorado Springs are published in this special issue. We believe that the papers in this special issue represent the forefront contributions to ISIF 2009 in the various areas of fundamental and applied science of integrated ferroelectrics and functionalities and their applications. We would like to take this opportunity to thank the following organizations and companies for their support and sponsorship for ISIF 2009, namely: Aixact Systems GMBH, Radiant Technologies, Symetrix Corporation, and Taylor and Francis Publishers. We would also like to thank the conference and session chairs, advisory and organizing committee members for their hard work that resulted in a very successful ISIF 2009, now in its new future-looking modality of Integrated Functionalities.« less

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.

Multiferroic behavior in CdCr2X4(X=S,Se)

NASA Astrophysics Data System (ADS)

Hemberger, J.; Lunkenheimer, P.; Fichtl, R.; Weber, S.; Tsurkan, V.; Loidl, A.

2006-05-01

The recently discovered multiferroic material CdCr2S4 shows a coexistence of ferromagnetism and relaxor ferroelectricity together with a colossal magnetocapacitive effect. The complex dielectric permittivity of this compound and of the structurally related CdCr2Se4 was studied by means of broadband dielectric spectroscopy using different electrode materials. The observed magnetocapacitive coupling at the magnetic transition is driven by enormous changes of the relaxation dynamics induced by the development of magnetic order.

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.

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

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.

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

Material System Engineering for Advanced Electrocaloric Cooling Technology

NASA Astrophysics Data System (ADS)

Qian, Xiaoshi

Electrocaloric effect refers to the entropy change and/or temperature change in dielectrics caused by the electric field induced polarization change. Recent discovery of giant ECE provides an opportunity to realize highly efficient cooling devices for a broad range of applications ranging from household appliances to industrial applications, from large-scale building thermal management to micro-scale cooling devices. The advances of electrocaloric (EC) based cooling device prototypes suggest that highly efficient cooling devices with compact size are achievable, which could lead to revolution in next generation refrigeration technology. This dissertation focuses on both EC based materials and cooling devices with their recent advances that address practical issues. Based on better understandings in designing an EC device, several EC material systems are studied and improved to promote the performances of EC based cooling devices. In principle, applying an electric field to a dielectric would cause change of dipolar ordering states and thus a change of dipolar entropy. Giant ECE observed in ferroelectrics near ferroelectric-paraelectric (FE-PE) transition temperature is owing to the large dipolar orientation change, between random-oriented dipolar states in paraelectric phase and spontaneous-ordered dipolar states in ferroelectric phases, which is induced by external electric fields. Besides pursuing large ECE, studies on EC cooling devices indicated that EC materials are required to possess wide operational temperature window, in which large ECE can be maintained for efficient operations. Although giant ECE was first predicted in ferroelectric polymers, where the large effect exhibits near FEPE phase transition, the narrow operation temperature window poses obstacles for these normal ferroelectrics to be conveniently perform in wide range of applications. In this dissertation, we demonstrated that the normal ferroelectric polymers can be converted to relaxor ferroelectric polymers which possess both giant ECE (27 Kelvin temperature drop) and much wider operating temperature window (over 50 kelvin covering RT) by proper defect modification which delicately tailors ferroelectrics in meso-, micro- and molecular scales. In addition, in order to be practical, EC device requires EC material can be driven at low electric fields upon achieve the large ECE. It is demonstrated in this dissertation that by facially modifying materials structure in meso-, micro- and molecular scale, lowfield ECE can be greatly improved. Large ECE, induced by low electric fields and existing in wide temperature window, is a major improvement in EC materials for practical applications. Besides EC polymers, this thesis also investigated EC ceramics. Due to several unique opportunities offered by the EC ceramics, Ba(ZrxTi 1-x)O3 (BZT), that is studied. (i) This class of EC ceramics offers a possibility to explore the invariant critical point (ICP), which maximizes the number of coexistent phase and provides a nearly vanishing energy barrier for switching among different phases. As demonstrated in this thesis, the BZT bulk ceramics at x˜ 0.2 exhibits a large adiabatic temperature drop DeltaTc=4.5 K, a large isothermal entropy change DeltaS = 8 Jkg-1K-1, a large EC coefficient (|DeltaT c/DeltaE| = 0.52x10-6 KmV-1 and DeltaS/DeltaE=0.93x10 -6 Jmkg-1K-1V-1) over a wide operating temperature range Tspan>30K. (ii) The thermal conductivity of EC ceramics is in general, much higher than that of EC polymers, and consequently they will allow EC cooling configurations which are not accessible by the EC polymers. Moreover, in the same device configuration, the high thermal conductivity of EC ceramics (kappa> 5 W/mK, compared with EC polymer, ˜ 0.25 W/mK) allows higher operation frequency and therefore a higher cooling power. (iii) Well-established fabrication processes of multilayer ceramic capacitor (MLCC) provide a foundation for the EC ceramic toward mass production. In this thesis, BZT thick film double layers have been fabricated and large ECE has been directly measured. EC induced temperature drop (DeltaT) around 6.3 °C and entropy change (DeltaS) of 11.0 Jkg-1K -1 are observed under an electric field of DeltaE=14.6 MV/m at 40 °C was observed in BZT thick film double layers. The result encourages further investigations on ECE in MLCC for practical applications. (Abstract shortened by ProQuest.).

Ultrahigh energy density harvested from domain-engineered relaxor ferroelectric single crystals under high strain rate loading

NASA Astrophysics Data System (ADS)

Shkuratov, Sergey I.; Baird, Jason; Antipov, Vladimir G.; Talantsev, Evgueni F.; Chase, Jay B.; Hackenberger, Wesley; Luo, Jun; Jo, Hwan R.; Lynch, Christopher S.

2017-04-01

Relaxor ferroelectric single crystals have triggered revolution in electromechanical systems due to their superior piezoelectric properties. Here the results are reported on experimental studies of energy harvested from (1-y-x)Pb(In1/2Nb1/2)O3-(y)Pb(Mg1/3Nb2/3)O3-(x)PbTiO3 (PIN-PMN-PT) crystals under high strain rate loading. Precise control of ferroelectric properties through composition, size and crystallographic orientation of domains made it possible to identify single crystals that release up to three times more electric charge density than that produced by PbZr0.52Ti0.48O3 (PZT 52/48) and PbZr0.95Ti0.05O3 (PZT 95/5) ferroelectric ceramics under identical loading conditions. The obtained results indicate that PIN-PMN-PT crystals became completely depolarized under 3.9 GPa compression. It was found that the energy density generated in the crystals during depolarization in the high voltage mode is four times higher than that for PZT 52/48 and 95/5. The obtained results promise new single crystal applications in ultrahigh-power transducers that are capable of producing hundreds kilovolt pulses and gigawatt-peak power microwave radiation.

Ultrahigh energy density harvested from domain-engineered relaxor ferroelectric single crystals under high strain rate loading

PubMed Central

Shkuratov, Sergey I.; Baird, Jason; Antipov, Vladimir G.; Talantsev, Evgueni F.; Chase, Jay B.; Hackenberger, Wesley; Luo, Jun; Jo, Hwan R.; Lynch, Christopher S.

2017-01-01

Relaxor ferroelectric single crystals have triggered revolution in electromechanical systems due to their superior piezoelectric properties. Here the results are reported on experimental studies of energy harvested from (1-y-x)Pb(In1/2Nb1/2)O3–(y)Pb(Mg1/3Nb2/3)O3–(x)PbTiO3 (PIN-PMN-PT) crystals under high strain rate loading. Precise control of ferroelectric properties through composition, size and crystallographic orientation of domains made it possible to identify single crystals that release up to three times more electric charge density than that produced by PbZr0.52Ti0.48O3 (PZT 52/48) and PbZr0.95Ti0.05O3 (PZT 95/5) ferroelectric ceramics under identical loading conditions. The obtained results indicate that PIN-PMN-PT crystals became completely depolarized under 3.9 GPa compression. It was found that the energy density generated in the crystals during depolarization in the high voltage mode is four times higher than that for PZT 52/48 and 95/5. The obtained results promise new single crystal applications in ultrahigh-power transducers that are capable of producing hundreds kilovolt pulses and gigawatt-peak power microwave radiation. PMID:28440336

Enhanced piezoelectricity in A B O3 ferroelectrics via intrinsic stress-driven flattening of the free-energy profile

NASA Astrophysics Data System (ADS)

Feng, Yu; Li, Wei-Li; Yu, Yang; Jia, He-Nan; Qiao, Yu-Long; Fei, Wei-Dong

2017-11-01

An approach to greatly enhance the piezoelectric properties (˜4 00 pC/N) of the tetragonal BaTi O3 polycrystal using a small number of A -site acceptor-donor substitutions [D. Xu et al., Acta Mater. 79, 84 (2014), 10.1016/j.actamat.2014.07.023] has been proposed. In this study, Pb (ZrTi ) O3 (PZT) based polycrystals with various crystal symmetries (tetragonal, rhombohedral, and so on) were chosen to investigate the piezoelectricity enhancement mechanism. X-ray diffraction results show that doping generates an intrinsic uniaxial compressive stress along the [001] pc direction in the A B O3 lattices. Piezoelectric maps in the parameter space of temperature and Ti concentration in the PZT and doped system show a more significant enhancement effect of L i+-A l3 + codoping in tetragonal PZT than in the rhombohedral phase. Phenomenological thermodynamic analysis indicates that the compressive stress results in more serious flattening of the free-energy profile in tetragonal PZT, compared with that in the rhombohedral phase. The chemical stress obtained by this acceptor-donor codoping can be utilized to optimize the piezoelectric performance on the tetragonal-phase site of the morphotropic phase boundary in the PZT system. The present study provides a promising route to the large piezoelectric effect induced by chemical-stress-driven flattening of the free-energy profile.

Room temperature metastable monoclinic phase in BaTiO3 crystals

NASA Astrophysics Data System (ADS)

Lummen, Tom; Wang, Jianjun; Holt, Martin; Kumar, Amit; Vlahos, Eftihia; Denev, Sava; Chen, Long-Qing; Gopalan, Venkatraman

2011-03-01

Low-symmetry monoclinic phases in ferroelectric materials are of considerable interest, due to their associated enhanced electromechanical coupling. Such phases have been found in Pb-based perovskite solid solutions such as lead zirconate titanate (PZT), where they form structural bridges between the rhombohedral and tetragonal ground states in compositional space. In this work, we directly image such a monoclinic phase in BaTi O3 crystals at room-temperature, using optical second harmonic generation, Raman, and X-ray microscopic imaging techniques. Phase-field modeling indicates that ferroelectric domain microstructures in BaTi O3 induce local inhomogeneous stresses in the crystals, which can effectively trap the transient intermediate monoclinic structure that occurs across the thermal orthorhombic-tetragonal phase boundary. The induced metastable monoclinic domains are ferroelectrically soft, being easily moved by electric fields as low as 0.5 kV cm-1 . Stabilizing such intermediate low-symmetry phases could very well lead to Pb-free materials with enhanced piezoelectric properties.

Single-domain multiferroic BiFeO 3 films

DOE PAGES

Kuo, Chang -Yang; Hu, Z.; Yang, J. C.; ...

2016-09-01

The strong coupling between antiferromagnetism and ferroelectricity at room temperature found in BiFeO 3 generates high expectations for the design and development of technological devices with novel functionalities. However, the multi-domain nature of the material tends to nullify the properties of interest and complicates the thorough understanding of the mechanisms that are responsible for those properties. Here we report the realization of a BiFeO 3 material in thin film form with single-domain behaviour in both its magnetism and ferroelectricity: the entire film shows its antiferromagnetic axis aligned along the crystallographic b axis and its ferroelectric polarization along the c axis.more » With this we are able to reveal that the canted ferromagnetic moment due to the Dzyaloshinskii–Moriya interaction is parallel to the a axis. Moreover, by fabricating a Co/BiFeO 3 heterostructure, we demonstrate that the ferromagnetic moment of the Co film does couple directly to the canted moment of BiFeO 3.« less

Relaxation of ferroelectric states in 2D distributions of quantum dots: EELS simulation

NASA Astrophysics Data System (ADS)

Cortés, C. M.; Meza-Montes, L.; Moctezuma, R. E.; Carrillo, J. L.

2016-06-01

The relaxation time of collective electronic states in a 2D distribution of quantum dots is investigated theoretically by simulating EELS experiments. From the numerical calculation of the probability of energy loss of an electron beam, traveling parallel to the distribution, it is possible to estimate the damping time of ferroelectric-like states. We generate this collective response of the distribution by introducing a mean field interaction among the quantum dots, and then, the model is extended incorporating effects of long-range correlations through a Bragg-Williams approximation. The behavior of the dielectric function, the energy loss function, and the relaxation time of ferroelectric-like states is then investigated as a function of the temperature of the distribution and the damping constant of the electronic states in the single quantum dots. The robustness of the trends and tendencies of our results indicate that this scheme of analysis can guide experimentalists to develop tailored quantum dots distributions for specific applications.

Power conversion efficiency exceeding the Shockley-Queisser limit in a ferroelectric insulator

NASA Astrophysics Data System (ADS)

Spanier, Jonathan E.; Fridkin, Vladimir M.; Rappe, Andrew M.; Akbashev, Andrew R.; Polemi, Alessia; Qi, Yubo; Gu, Zongquan; Young, Steve M.; Hawley, Christopher J.; Imbrenda, Dominic; Xiao, Geoffrey; Bennett-Jackson, Andrew L.; Johnson, Craig L.

2016-09-01

Ferroelectric absorbers, which promote carrier separation and exhibit above-gap photovoltages, are attractive candidates for constructing efficient solar cells. Using the ferroelectric insulator BaTiO3 we show how photogeneration and the collection of hot, non-equilibrium electrons through the bulk photovoltaic effect (BPVE) yields a greater-than-unity quantum efficiency. Despite absorbing less than a tenth of the solar spectrum, the power conversion efficiency of the BPVE device under 1 sun illumination exceeds the Shockley-Queisser limit for a material of this bandgap. We present data for devices that feature a single-tip electrode contact and an array with 24 tips (total planar area of 1 × 1 μm2) capable of generating a current density of 17 mA cm-2 under illumination of AM1.5 G. In summary, the BPVE at the nanoscale provides an exciting new route for obtaining high-efficiency photovoltaic solar energy conversion.

Stoichiometry as key to ferroelectricity in compressively strained SrTiO{sub 3} films

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

Haislmaier, R. C.; Engel-Herbert, R.; Gopalan, V.

2016-07-18

While strain is a powerful tuning parameter for inducing ferroelectricity in thin film oxides, the role of stoichiometry control is critical, but far less explored. A series of compressively strained SrTiO{sub 3} films on (001) (LaAlO{sub 3}){sub 0.3}(Sr{sub 2}AlTaO{sub 6}){sub 0.35} substrates were grown by hybrid molecular beam epitaxy where the Ti cation was supplied using a metal-organic titanium tetraisopropoxide molecule that helps systematically and precisely control Sr:Ti stoichiometry in the resulting films. A stoichiometric growth window is located through X-ray diffraction and in-situ reflection high-energy electron diffraction measurements, which show a minimum out-of-plane lattice parameter as well as constantmore » growth rate within the stoichiometric growth window range. Using temperature dependent optical second harmonic generation (SHG) characterization, a ferroelectric-to-paraelectric transition at T ∼ 180 K is observed for a stoichiometric SrTiO{sub 3} film, as well as a higher temperature structural transition at T ∼ 385 K. Using SHG polarimetry modeling, the polar point group symmetry is determined to be tetragonal 4mm with the polarization pointing out-of-plane of the film. The SHG coefficients, d{sub 31}/d{sub 15}=3 and d{sub 33}/d{sub 15}=21, were determined at 298 K. The ferroelectric transition disappears in films grown outside the growth window, thus proving the critical role of stoichiometry control in realizing strain-induced ferroelectricity.« less

Old and new ideas in ferroelectric liquid crystal technology

NASA Astrophysics Data System (ADS)

Lagerwall, Sven T.; Matuszczyk, M.; Matuszczyk, T.

1998-02-01

Ferroelectric liquid crystals (FLC) are to conventional liquid crystal what Gallium Arsenide is to Silicon in the semiconductor area. The first generation of FLC displays in now present on the market and has some outstanding features based on the symmetric bistability which may be achieved in these materials. One of the greatest challenges for the next generation is to achieve an analog grey scale out of an essentially digital principle. We will analyze in some detail which major problems had to be solved to reach the present state and show how the final steps could be taken toward a new state-of-the-art level in liquid crystal devices. In the last decade university research and industrial R and D have almost equally contributed to treat the very serious complications caused by the so-called chevron structures We will review this important topic in particular detail.

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.

Effect of temperature-driven phase transition on energy-storage and -release properties of Pb0.97La0.02[Zr0.55Sn0.30Ti0.15]O3 ceramics

NASA Astrophysics Data System (ADS)

Xu, Ran; Tian, Jingjing; Zhu, Qingshan; Feng, Yujun; Wei, Xiaoyong; Xu, Zhuo

2017-07-01

Temperature-driven phase transition of Pb0.97La0.02[Zr0.55Sn0.30Ti0.15]O3 ceramics was studied, and the consecutive ferroelectric-antiferroelectric-paraelectric (FE-AFE-PE) switching was confirmed. The materials have better dielectric tunability (-82% to 50%) in the AFE state than in the FE state. Also, the phase transition influences the energy-storage and -release performance significantly. A sharp increase in releasable energy density and efficiency was observed due to the temperature-driven FE-AFE transition. Highest releasable energy density, current density, and peak power density were achieved at 130 °C, which was attributed to the highest backward transition field. The stored charge was released completely in AFE and PE states in the microseconds scale, while only a small part of it was released in the FE state. The above results indicate the huge impact of temperature-driven phase transition on dielectrics' performance, which is significant when developing AFE materials working in a wide temperature range.

Self-Positioned Nanosized Mask for Transparent and Flexible Ferroelectric Polymer Nanodiodes Array.

PubMed

Hyun, Seung; Kwon, Owoong; Choi, Chungryong; Vincent Joseph, Kanniyambatti L; Kim, Yunseok; Kim, Jin Kon

2016-10-12

High density arrays of ferroelectric polymer nanodiodes have gained strong attention for next-generation transparent and flexible nonvolatile resistive memory. Here, we introduce a facile and innovative method to fabricate ferroelectric polymer nanodiode array on an ITO-coated poly(ethylene terephthalate) (PET) substrate by using block copolymer self-assembly and oxygen plasma etching. First, polystyrene-block-poly(2-vinylpyridine) copolymer (PS-b-P2VP) micelles were spin-coated on poly(vinylidene fluoride-ran-trifluoroethylene) copolymer (P(VDF-TrFE)) film/ITO-coated PET substrate. After the sample was immersed in a gold precursor (HAuCl 4 ) containing solution, which strongly coordinates with nitrogen group in P2VP, oxygen plasma etching was performed. During the plasma etching, coordinated gold precursors became gold nanoparticles (GNPs), which successfully acted as self-positioned etching mask to fabricate a high density array of P(VDF-TrFE)) nanoislands with GNP at the top. Each nanoisland shows clearly individual diode property, as confirmed by current-voltage (I-V) curve. Furthermore, due to the transparent and flexible nature of P(VDF-TrFE)) nanoisland as well as the substrate, the P(VDF-TrFE) nanodiode array was highly tranparent, and the diode property was maintained even after a large number of bendings (for instance, 1000 times). The array could be used as the next-generation tranparent and flexible nonvolatile memory device.

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

Strain-induced tetragonal distortions and multiferroic properties in polycrystalline Sr 1 - x B a x Mn O 3 ( x = 0.43 - 0.45 ) perovskites

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

Somaily, H.; Kolesnik, S.; Mais, J.

Here, we report a comprehensive structure-property phase diagram of unique single-ion type-1 multiferroic pseudocubic Sr 1-xBa xMnO 3 perovskites. Employing a specially designed multi-step reduction-oxidation synthesis technique, we describe the successful synthesis of previously unknown Sr 1-xBa xMnO 3 compositions in their polycrystalline form with a significantly extended Ba solubility limit that is only rivaled by a very limited number of crystals and thin films grown under non-equilibrium conditions. Understanding the multiferroic interplay with structure in Sr 1-xBa xMnO 3 is of great importance as it opens the door wide to the development of newer materials from the parent (AA’)(BB’)more » O 3 system with enhanced properties. To this end, using a combination of time-of-flight neutron and synchrotron x-ray scattering techniques, we determined the exact structures and quantified the Mn and oxygen polar distortions above and below T C and T N. In its ferroelectric state, the system crystalizes in the noncentrosymmetric tetragonal P4mm space group which gives rise to a large electric dipole moment P s, in the z-direction, of 18.4 and 29.5 µC/cm 2 for x = 0.43 and 0.45, respectively. The two independently driven ferroelectric and magnetic order parameters are single-handedly accommodated by the Mn sublattice leading to a novel strain-assisted multiferroic behavior in agreement with many theoretical predictions. Our neutron diffraction results demonstrate the large and tunable suppression of the ferroelectric order at the onset of AFM ordering and confirm the coexistence and strong coupling of the two ferroic orders below T N. The refined magnetic moments confirm the strong covalent bonding between Mn and the oxygen anions which is necessary for stabilizing the ferroelectric phase.« less

Strain-induced tetragonal distortions and multiferroic properties in polycrystalline Sr 1 - x B a x Mn O 3 ( x = 0.43 - 0.45 ) perovskites

DOE PAGES

Somaily, H.; Kolesnik, S.; Mais, J.; ...

2018-05-17

Here, we report a comprehensive structure-property phase diagram of unique single-ion type-1 multiferroic pseudocubic Sr 1-xBa xMnO 3 perovskites. Employing a specially designed multi-step reduction-oxidation synthesis technique, we describe the successful synthesis of previously unknown Sr 1-xBa xMnO 3 compositions in their polycrystalline form with a significantly extended Ba solubility limit that is only rivaled by a very limited number of crystals and thin films grown under non-equilibrium conditions. Understanding the multiferroic interplay with structure in Sr 1-xBa xMnO 3 is of great importance as it opens the door wide to the development of newer materials from the parent (AA’)(BB’)more » O 3 system with enhanced properties. To this end, using a combination of time-of-flight neutron and synchrotron x-ray scattering techniques, we determined the exact structures and quantified the Mn and oxygen polar distortions above and below T C and T N. In its ferroelectric state, the system crystalizes in the noncentrosymmetric tetragonal P4mm space group which gives rise to a large electric dipole moment P s, in the z-direction, of 18.4 and 29.5 µC/cm 2 for x = 0.43 and 0.45, respectively. The two independently driven ferroelectric and magnetic order parameters are single-handedly accommodated by the Mn sublattice leading to a novel strain-assisted multiferroic behavior in agreement with many theoretical predictions. Our neutron diffraction results demonstrate the large and tunable suppression of the ferroelectric order at the onset of AFM ordering and confirm the coexistence and strong coupling of the two ferroic orders below T N. The refined magnetic moments confirm the strong covalent bonding between Mn and the oxygen anions which is necessary for stabilizing the ferroelectric phase.« less

Solvent-Dependent Delamination, Restacking, and Ferroelectric Behavior in a New Charge-Separated Layered Compound: [NH4 ][Ag3 (C9 H5 NO4 S)2 (C13 H14 N2 )2 ]⋅8 H2 O.

PubMed

Sushrutha, Sringeri Ramesh; Mohana, Shivanna; Pal, Somnath; Natarajan, Srinivasan

2017-01-03

A new anionic coordination polymer, [NH 4 ][Ag 3 (C 9 H 5 NO 4 S) 2 (C 13 H 14 N 2 ) 2 ]⋅8 H 2 O, with a two-dimensional structure, has been synthesized by a reaction between silver nitrate, 8-hydroxyquinoline-5-sulfonic acid (HQS), and 4,4'-trimethylene dipyridine (TMDP). The compound stabilizes in a noncentrosymmetric space group, and the lattice water molecules and the charge-compensating [NH 4 ] + group occupy the inter-lamellar spaces. The lattice water molecules can be fully removed and reinserted, which is accompanied by a crystalline-amorphous-crystalline transformation. This transformation resembles the collapse/delamination and restacking of the layers. To the best of our knowledge, this is the first observation of delamination and restacking in an inorganic coordination polymer that contains silver. The presence of a natural dipole (the anionic framework and cationic ammonium ions) along with the noncentrosymmetric space group gives rise to the room-temperature ferroelectric behavior of the compound. The ferroelectric behavior is also water-dependent and exhibits a ferroelectric-paraelectric transformation. The temperature-dependent dielectric measurements indicate that the ferroelectric/ paraelectric transformation occurs at 320 K. This transformation has also been investigated by using in-situ IR spectroscopy and PXRD studies. The second-harmonic generation (SHG) study indicated values that are comparable to some of the known SHG solids, such as potassium dihydrogen phosphate (KDP) and urea. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Atomically engineered ferroic layers yield a room-temperature magnetoelectric multiferroic

NASA Astrophysics Data System (ADS)

Mundy, Julia A.; Brooks, Charles M.; Holtz, Megan E.; Moyer, Jarrett A.; Das, Hena; Rébola, Alejandro F.; Heron, John T.; Clarkson, James D.; Disseler, Steven M.; Liu, Zhiqi; Farhan, Alan; Held, Rainer; Hovden, Robert; Padgett, Elliot; Mao, Qingyun; Paik, Hanjong; Misra, Rajiv; Kourkoutis, Lena F.; Arenholz, Elke; Scholl, Andreas; Borchers, Julie A.; Ratcliff, William D.; Ramesh, Ramamoorthy; Fennie, Craig J.; Schiffer, Peter; Muller, David A.; Schlom, Darrell G.

2016-09-01

Materials that exhibit simultaneous order in their electric and magnetic ground states hold promise for use in next-generation memory devices in which electric fields control magnetism. Such materials are exceedingly rare, however, owing to competing requirements for displacive ferroelectricity and magnetism. Despite the recent identification of several new multiferroic materials and magnetoelectric coupling mechanisms, known single-phase multiferroics remain limited by antiferromagnetic or weak ferromagnetic alignments, by a lack of coupling between the order parameters, or by having properties that emerge only well below room temperature, precluding device applications. Here we present a methodology for constructing single-phase multiferroic materials in which ferroelectricity and strong magnetic ordering are coupled near room temperature. Starting with hexagonal LuFeO3—the geometric ferroelectric with the greatest known planar rumpling—we introduce individual monolayers of FeO during growth to construct formula-unit-thick syntactic layers of ferrimagnetic LuFe2O4 (refs 17, 18) within the LuFeO3 matrix, that is, (LuFeO3)m/(LuFe2O4)1 superlattices. The severe rumpling imposed by the neighbouring LuFeO3 drives the ferrimagnetic LuFe2O4 into a simultaneously ferroelectric state, while also reducing the LuFe2O4 spin frustration. This increases the magnetic transition temperature substantially—from 240 kelvin for LuFe2O4 (ref. 18) to 281 kelvin for (LuFeO3)9/(LuFe2O4)1. Moreover, the ferroelectric order couples to the ferrimagnetism, enabling direct electric-field control of magnetism at 200 kelvin. Our results demonstrate a design methodology for creating higher-temperature magnetoelectric multiferroics by exploiting a combination of geometric frustration, lattice distortions and epitaxial engineering.

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.

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

Ferroelectric translational antiphase boundaries in nonpolar materials

PubMed Central

Wei, Xian-Kui; Tagantsev, Alexander K.; Kvasov, Alexander; Roleder, Krystian; Jia, Chun-Lin; Setter, Nava

2014-01-01

Ferroelectric materials are heavily used in electro-mechanics and electronics. Inside the ferroelectric, domain walls separate regions in which the spontaneous polarization is differently oriented. Properties of ferroelectric domain walls can differ from those of the domains themselves, leading to new exploitable phenomena. Even more exciting is that a non-ferroelectric material may have domain boundaries that are ferroelectric. Many materials possess translational antiphase boundaries. Such boundaries could be interesting entities to carry information if they were ferroelectric. Here we show first that antiphase boundaries in antiferroelectrics may possess ferroelectricity. We then identify these boundaries in the classical antiferroelectric lead zirconate and evidence their polarity by electron microscopy using negative spherical-aberration imaging technique. Ab initio modelling confirms the polar bi-stable nature of the walls. Ferroelectric antiphase boundaries could make high-density non-volatile memory; in comparison with the magnetic domain wall memory, they do not require current for operation and are an order of magnitude thinner. PMID:24398704

Ferroelectric memory based on molybdenum disulfide and ferroelectric hafnium oxide

NASA Astrophysics Data System (ADS)

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

Recently, ferroelectric hafnium oxide (HfO2) was discovered as a new type of ferroelectric material with the advantages of high coercive field, excellent scalability (down to 2.5 nm), and good compatibility with CMOS processing. In this work, we demonstrate, for the first time, 2D ferroelectric memories with molybdenum disulfide (MoS2) as the channel material and aluminum doped HfO2 as the ferroelectric gate dielectric. A 16 nm thick layer of HfO2, doped with 5.26% aluminum, was deposited via atomic layer deposition (ALD), then subjected to rapid thermal annealing (RTA) at 1000 °C, and the polarization-voltage characteristics of the resulting metal-ferroelectric-metal (MFM) capacitors were measured, showing a remnant polarization of 0.6 μC/cm2. Ferroelectric memories with embedded ferroelectric hafnium oxide stacks and monolayer MoS2 were fabricated. The transfer characteristics after program and erase pulses revealed a clear ferroelectric memory window. In addition, endurance (up to 10,000 cycles) of the devices were tested and effects associated with ferroelectric materials, such as the wake-up effect and polarization fatigue, were observed. This research can potentially lead to advances of 2D materials in low-power logic and memory applications.

Pressure, temperature, and electric field dependence of phase transformations in niobium modified 95/5 lead zirconate titanate

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

Dong, Wen D.; Carlos Valadez, J.; Gallagher, John A.

2015-06-28

Ceramic niobium modified 95/5 lead zirconate-lead titanate (PZT) undergoes a pressure induced ferroelectric to antiferroelectric phase transformation accompanied by an elimination of polarization and a volume reduction. Electric field and temperature drive the reverse transformation from the antiferroelectric to ferroelectric phase. The phase transformation was monitored under pressure, temperature, and electric field loading. Pressures and temperatures were varied in discrete steps from 0 MPa to 500 MPa and 25 °C to 125 °C, respectively. Cyclic bipolar electric fields were applied with peak amplitudes of up to 6 MV m{sup −1} at each pressure and temperature combination. The resulting electric displacement–electric field hysteresis loops weremore » open “D” shaped at low pressure, characteristic of soft ferroelectric PZT. Just below the phase transformation pressure, the hysteresis loops took on an “S” shape, which split into a double hysteresis loop just above the phase transformation pressure. Far above the phase transformation pressure, when the applied electric field is insufficient to drive an antiferroelectric to ferroelectric phase transformation, the hysteresis loops collapse to linear dielectric behavior. Phase stability maps were generated from the experimental data at each of the temperature steps and used to form a three dimensional pressure–temperature–electric field phase diagram.« less

A controllable robust multiferroic GaTeCl monolayer with colossal 2D ferroelectricity and desirable multifunctionality.

PubMed

Zhang, Shi-Hao; Liu, Bang-Gui

2018-03-29

We propose through first-principles investigation that the GaTeCl monolayer is an excellent two-dimensional (2D) multiferroic with giant mechanical anisotropy. The calculated phonon spectrum, molecular dynamic simulations, and elastic moduli confirm its dynamic and mechanical stability, and our cleavage energy analysis shows that exfoliating one GaTeCl monolayer from the existing GaTeCl bulk is feasible. The calculated in-plane ferroelectric polarization reaches 578 pC m-1. The energy barriers per formula unit of the ferroelastic 90° rotational and ferroelectric reversal transitions are 476 meV and 754 meV, respectively, being the greatest in the 2D multiferroics family so far. Importantly, on the other hand, a tensile stress of 4.7 N m-1 perpendicular to the polarization can drive the polarization to rotate by 90°. These can make the GaTeCl monolayer have not only robust ferroelasticity and ferroelectricity but also easy mechanical controllability. Furthermore, the GaTeCl monolayer has giant piezoelectricity and optical second harmonic generation, especially in the range of visible light, and a tensile stress of 0.3 N m-1 along the polarization can make the indirect gap transit to the direct gap. These interesting mechanical, electronic, and optical properties of the GaTeCl monolayer show its great potential in high-performance multi-functional applications.

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).

Plasmonic Antennas for Optical Nanocrystallography and Femtosecond Spatio-Temporal Control

NASA Astrophysics Data System (ADS)

Berweger, Samuel

Controlling optical fields on nanometer length scales has been a long standing problem in optics, driven by the desire to image spatial inhomogeneities of condensed matter on the natural length scales of molecular, electronic, or lattice correlations. The concept of optical antennas based on plasmon resonant nanostructures has emerged as an attractive solution for concentrating and confining light to the nanoscale with a high degree of spatial confinement achieved in the evanescent field. This dissertation focuses on the fundamental characteristics of the antenna properties of plasmonic metal tips and their application for nanometer-resolved optical scanning probe spectroscopy and imaging. First this work demonstrates the extension of tip-enhanced Raman scattering (TERS) to optical nanocrystallography in order to study ferroelectric domain order by using the symmetry selective Raman selection rules for polar phonon modes in combination with the polarization-dependent TERS enhancement. After the derivation of the polar phonon TERS selection rules, ferroelectric domains arising from finite size effects within individual BaTiO3 nanorods are imaged. The second part of this work explores the fundamental characteristics and applications of adiabatic surface plasmon polariton (SPP) nanofocusing as an optical antenna for far- to near-field mode transformation. This process, resulting from the radius-dependent index of refraction experienced by SPP's propagating on tapered waveguides, is shown to result in a nanoconfined optical excitation at the apex of Au tips 10's of nm in size. To demonstrate the general application for background-free spectroscopy, adiabatic nanofocusing TERS is shown to improve contrast and sensitivity, and enables the extension to the near-IR spectral range. Lastly, due to the phase, wavelength, and amplitude independent nanofocusing mechanism, the independent and simultaneous nanometer-femtosecond spatio-temporal control of ultrafast pulses is possible. Combining the frequency domain shaping of optical transients with nanofocusing, we demonstrate the deterministic control of pulses as short as 16 fs and the generation of arbitrary waveforms at the tip apex. These results demonstrate the capability of these plasmonic optical antennas to not only generate enhanced optical fields for the study of matter on the nanoscale, but also to control ultrafast nano-optical excitations with applications for imaging and spectroscopy.

NMR evidence of charge fluctuations in multiferroic CuBr2

NASA Astrophysics Data System (ADS)

Wang, Rui-Qi; Zheng, Jia-Cheng; Chen, Tao; Wang, Peng-Shuai; Zhang, Jin-Shan; Cui, Yi; Wang, Chao; Li, Yuan; Xu, Sheng; Yuan, Feng; Yu, Wei-Qiang

2018-03-01

We report combined magnetic susceptibility, dielectric constant, nuclear quadruple resonance (NQR), and zero-field nuclear magnetic resonance (NMR) measurements on single crystals of multiferroics CuBr2. High quality of the sample is demonstrated by the sharp magnetic and magnetic-driven ferroelectric transition at {T}{{N}}={T}{{C}}≈ 74 K. The zero-field 79Br and 81Br NMR are resolved below T N. The spin-lattice relaxation rates reveal charge fluctuations when cooled below 60 K. Evidences of an increase of NMR linewidth, a reduction of dielectric constant, and an increase of magnetic susceptibility are also seen at low temperatures. These data suggest an emergent instability which competes with the spiral magnetic ordering and the ferroelectricity. Candidate mechanisms are discussed based on the quasi-one-dimensional nature of the magnetic system. Project supported by the Ministry of Science and Technology of China (Grant No. 2016YFA0300504), the National Natural Science Foundation of China (Grant No. 11374364), the Fundamental Research Funds for the Central Universities of China, and the Research Funds of Renmin University, China (Grant No. 14XNLF08).

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.

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.

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

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.

Giant elastic tunability in strained BiFeO 3 near an electrically induced phase transition

DOE PAGES

Yu, Pu; Vasudevan, Rama K.; Tselev, Alexander; ...

2015-11-24

Elastic anomalies are signatures of phase transitions in condensed matters and have traditionally been studied using various techniques spanning from neutron scattering to static mechanical testing. Here, using band-excitation elastic/piezoresponse spectroscopy, we probed sub-MHz elastic dynamics of a tip bias-induced rhombohedral–tetragonal phase transition of strained (001)-BiFeO 3 (rhombohedral) ferroelectric thin films from ~10 3 nm 3 sample volumes. Near this transition, we observed that the Young's modulus intrinsically softens by over 30% coinciding with 2-3 folds enhancement of local piezoresponse. Coupled with phase-field modeling, we also addressed the influence of polarization switching and mesoscopic structural heterogeneities (e.g., domain walls) onmore » the kinetics of this phase transition, thereby providing fresh insights into the morphotropic phase boundary (MPB) in ferroelectrics. Moreover, the giant electrically tunable elastic stiffness and corresponding electromechanical properties observed here suggest potential applications of BiFeO 3 in next-generation frequency-agile electroacoustic devices, based on utilization of the soft modes underlying successive ferroelectric phase transitions.« less

Highly mobile ferroelastic domain walls in compositionally graded ferroelectric thin films

DOE PAGES

Damodaran, Anoop; Okatan, M. B.; Kacher, J.; ...

2016-02-15

Domains and domain walls are critical in determining the response of ferroelectrics, and the ability to controllably create, annihilate, or move domains is essential to enable a range of next-generation devices. Whereas electric-field control has been demonstrated for ferroelectric 180° domain walls, similar control of ferroelastic domains has not been achieved. Here, using controlled composition and strain gradients, we demonstrate deterministic control of ferroelastic domains that are rendered highly mobile in a controlled and reversible manner. Through a combination of thin-film growth, transmission-electron-microscopy-based nanobeam diffraction and nanoscale band-excitation switching spectroscopy, we show that strain gradients in compositionally graded PbZr 1-xTimore » xO 3 heterostructures stabilize needle-like ferroelastic domains that terminate inside the film. These needle-like domains are highly labile in the out-of-plane direction under applied electric fields, producing a locally enhanced piezoresponse. This work demonstrates the efficacy of novel modes of epitaxy in providing new modalities of domain engineering and potential for as-yet-unrealized nanoscale functional devices.« less

Shift current bulk photovoltaic effect in polar materials—hybrid and oxide perovskites and beyond

DOE PAGES

Tan, Liang Z.; Zheng, Fan; Young, Steve M.; ...

2016-08-26

Here, the bulk photovoltaic effect (BPVE) refers to the generation of a steady photocurrent and above-bandgap photovoltage in a single-phase homogeneous material lacking inversion symmetry. The mechanism of BPVE is decidedly different from the typical p–n junction-based photovoltaic mechanism in heterogeneous materials. Recently, there has been renewed interest in ferroelectric materials for solar energy conversion, inspired by the discovery of above-bandgap photovoltages in ferroelectrics, the invention of low bandgap ferroelectric materials and the rapidly improving power conversion efficiency of metal halide perovskites. However, as long as the nature of the BPVE and its dependence on composition and structure remain poorlymore » understood, materials engineering and the realisation of its true potential will be hampered. In this review article, we survey the history, development and recent progress in understanding the mechanisms of BPVE, with a focus on the shift current mechanism, an intrinsic BPVE that is universal to all materials lacking inversion symmetry. In addition to explaining the theory of shift current, materials design opportunities and challenges will be discussed for future applications of the BPVE.« less

Highly mobile ferroelastic domain walls in compositionally graded ferroelectric thin films

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

Damodaran, Anoop; Okatan, M. B.; Kacher, J.

Domains and domain walls are critical in determining the response of ferroelectrics, and the ability to controllably create, annihilate, or move domains is essential to enable a range of next-generation devices. Whereas electric-field control has been demonstrated for ferroelectric 180° domain walls, similar control of ferroelastic domains has not been achieved. Here, using controlled composition and strain gradients, we demonstrate deterministic control of ferroelastic domains that are rendered highly mobile in a controlled and reversible manner. Through a combination of thin-film growth, transmission-electron-microscopy-based nanobeam diffraction and nanoscale band-excitation switching spectroscopy, we show that strain gradients in compositionally graded PbZr 1-xTimore » xO 3 heterostructures stabilize needle-like ferroelastic domains that terminate inside the film. These needle-like domains are highly labile in the out-of-plane direction under applied electric fields, producing a locally enhanced piezoresponse. This work demonstrates the efficacy of novel modes of epitaxy in providing new modalities of domain engineering and potential for as-yet-unrealized nanoscale functional devices.« less

Giant elastic tunability in strained BiFeO3 near an electrically induced phase transition

PubMed Central

Li, Q; Cao, Y.; Yu, P.; Vasudevan, R. K.; Laanait, N.; Tselev, A.; Xue, F.; Chen, L. Q.; Maksymovych, P.; Kalinin, S. V.; Balke, N.

2015-01-01

Elastic anomalies are signatures of phase transitions in condensed matters and have traditionally been studied using various techniques spanning from neutron scattering to static mechanical testing. Here, using band-excitation elastic/piezoresponse spectroscopy, we probed sub-MHz elastic dynamics of a tip bias-induced rhombohedral−tetragonal phase transition of strained (001)-BiFeO3 (rhombohedral) ferroelectric thin films from ∼103 nm3 sample volumes. Near this transition, we observed that the Young's modulus intrinsically softens by over 30% coinciding with two- to three-fold enhancement of local piezoresponse. Coupled with phase-field modelling, we also addressed the influence of polarization switching and mesoscopic structural heterogeneities (for example, domain walls) on the kinetics of this phase transition, thereby providing fresh insights into the morphotropic phase boundary in ferroelectrics. Furthermore, the giant electrically tunable elastic stiffness and corresponding electromechanical properties observed here suggest potential applications of BiFeO3 in next-generation frequency-agile electroacoustic devices, based on the utilization of the soft modes underlying successive ferroelectric phase transitions. PMID:26597483

Integrating Partial Polarization into a Metal-Ferroelectric-Semiconductor Field Effect Transistor Model

NASA Technical Reports Server (NTRS)

MacLeod, Todd C.; Ho, Fat Duen

1999-01-01

The ferroelectric channel in a Metal-Ferroelectric-Semiconductor Field Effect Transistor (MFSFET) can partially change its polarization when the gate voltage near the polarization threshold voltage. This causes the MFSFET Drain current to change with repeated pulses of the same gate voltage near the polarization threshold voltage. A previously developed model [11, based on the Fermi-Dirac function, assumed that for a given gate voltage and channel polarization, a sin-le Drain current value would be generated. A study has been done to characterize the effects of partial polarization on the Drain current of a MFSFET. These effects have been described mathematically and these equations have been incorporated into a more comprehensive mathematical model of the MFSFET. The model takes into account the hysteresis nature of the MFSFET and the time dependent decay as well as the effects of partial polarization. This model defines the Drain current based on calculating the degree of polarization from previous gate pulses, the present Gate voltage, and the amount of time since the last Gate volta-e pulse.

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.

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.

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%.

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.

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.

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.

Origin of the magnetic-field controlled polarization reversal in multiferroic TbMn2 O 5

NASA Astrophysics Data System (ADS)

Leo, N.; Meier, D.; Pisarev, R. V.; Park, S.; Cheong, S.-W.; Fiebig, M.

2011-03-01

The interplay of multi-dimensional complex magnetic order parameters leads to interesting effects like magnetically induced ferroelectricity. A particular interesting example is TbMn 2 O5 because of the associated magnetic-field controllable electric polarization. By optical second harmonic generation we show that the gigantic magnetoelectric effect originates in three independent ferroelectric contributions. Two of these are manganese-generated. The third contribution is related to the magnetism of the Tb 3+ sublattice and has not been identified so far. It mediates the remarkable magnetic-field induced polarization reversal. This model is verified by experiments on the isostructural YMn 2 O5 where Y3+ ions are nonmagnetic and only two polarization contributions are present and no magnetoelectric coupling is observed. These results underline the importance of the 3 d - 4 f -interaction for the intricate magnetoelectric coupling in the class of isostructural RMn 2 O5 compounds. This work was supported by the DFG through SFB 608.

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

Adaptive strain prompting a pseudo-morphotropic phase boundary in ferroelectric (1-x ) Na0.5Bi0.5TiO3-x BaTiO3

NASA Astrophysics Data System (ADS)

Datta, K.; Neder, R. B.; Richter, A.; Göbbels, M.; Neuefeind, J. C.; Mihailova, B.

2018-05-01

The understanding of the atomistic origin of the morphotropic phase boundary (MPB) occurring in composition-temperature phase diagrams of ferroelectric solid solutions is a key topic in material science because materials often exhibit anomalous properties at the MPB. Here we reveal mesoscopic-scale structural correlations for a leading Pb-free ferroelectric system, (1 -x ) Na0.5Bi0.5TiO3-x BaTiO3 (NBT-x BT ), by examining atomic pair distribution functions and Raman scattering data at ambient conditions. We demonstrate that the amplification of the piezoelectric properties of NBT-x BT at the MPB are predominantly driven by an easy switchability resulting from a progressive decoupling between strain and polarization as the Ba content increases from zero to the critical MPB composition. It was observed that as Ba content increases towards MPB, competing local correlations, such as A-site chemical order, antiferrodistortive correlations of correlated BO6 tilts, and antipolar Bi shifts, are reduced, which in turn renders favorable conditions for easy switching of local dipoles under external fields. In addition, the evolving characteristics of the atomic dynamics as a function of composition suggest that the local potential functions of the cations are not completely flat at the MPB. Altogether, our results reveal atomistic mechanisms responsible for the observed elevated MPB properties in the case of NBT-x BT which imply that the so-called MPB of NBT-x BT should not be categorized as originally introduced for Pb-containing solid solutions.

Ultrafast light-induced symmetry changes in single BaTiO 3 nanowires

DOE PAGES

Kuo, Yi -Hong; Nah, Sanghee; He, Kai; ...

2017-01-23

The coupling of light to nanoscale ferroelectric materials enables novel means of controlling their coupled degrees of freedom and engineering new functionality. Here we present femtosecond time-resolution nonlinear-optical measurements of light-induced dynamics within single ferroelectric barium titanate nanowires. By analyzing the time-dependent and polarization-dependent second harmonic intensity generated by the nanowire, we identify its crystallographic orientation and then make use of this information in order to probe its dynamic structural response and change in symmetry. Here, we show that photo-excitation leads to ultrafast, non-uniform modulations in the second order nonlinear susceptibility tensor, indicative of changes in the local symmetry ofmore » the nanostructure occurring on sub-picosecond time-scales.« less

Flexible ferroelectric element based on van der Waals heteroepitaxy.

PubMed

Jiang, Jie; Bitla, Yugandhar; Huang, Chun-Wei; Do, Thi Hien; Liu, Heng-Jui; Hsieh, Ying-Hui; Ma, Chun-Hao; Jang, Chi-Yuan; Lai, Yu-Hong; Chiu, Po-Wen; Wu, Wen-Wei; Chen, Yi-Chun; Zhou, Yi-Chun; Chu, Ying-Hao

2017-06-01

We present a promising technology for nonvolatile flexible electronic devices: A direct fabrication of epitaxial lead zirconium titanate (PZT) on flexible mica substrate via van der Waals epitaxy. These single-crystalline flexible ferroelectric PZT films not only retain their performance, reliability, and thermal stability comparable to those on rigid counterparts in tests of nonvolatile memory elements but also exhibit remarkable mechanical properties with robust operation in bent states (bending radii down to 2.5 mm) and cycling tests (1000 times). This study marks the technological advancement toward realizing much-awaited flexible yet single-crystalline nonvolatile electronic devices for the design and development of flexible, lightweight, and next-generation smart devices with potential applications in electronics, robotics, automotive, health care, industrial, and military systems.

Flexible ferroelectric element based on van der Waals heteroepitaxy

PubMed Central

Jiang, Jie; Bitla, Yugandhar; Huang, Chun-Wei; Do, Thi Hien; Liu, Heng-Jui; Hsieh, Ying-Hui; Ma, Chun-Hao; Jang, Chi-Yuan; Lai, Yu-Hong; Chiu, Po-Wen; Wu, Wen-Wei; Chen, Yi-Chun; Zhou, Yi-Chun; Chu, Ying-Hao

2017-01-01

We present a promising technology for nonvolatile flexible electronic devices: A direct fabrication of epitaxial lead zirconium titanate (PZT) on flexible mica substrate via van der Waals epitaxy. These single-crystalline flexible ferroelectric PZT films not only retain their performance, reliability, and thermal stability comparable to those on rigid counterparts in tests of nonvolatile memory elements but also exhibit remarkable mechanical properties with robust operation in bent states (bending radii down to 2.5 mm) and cycling tests (1000 times). This study marks the technological advancement toward realizing much-awaited flexible yet single-crystalline nonvolatile electronic devices for the design and development of flexible, lightweight, and next-generation smart devices with potential applications in electronics, robotics, automotive, health care, industrial, and military systems. PMID:28630922

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.

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.

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 .

Fabrication and characterization of piezoelectric micromachined ultrasonic transducers with thick composite PZT films.

PubMed

Wang, Zhihong; Zhu, Weiguang; Zhu, Hong; Miao, Jianmin; Chao, Chen; Zhao, Changlei; Tan, Ooi Kiang

2005-12-01

Ferroelectric microelectromechanical systems (MEMS) has been a growing area of research in past decades, in which ferroelectric films are combined with silicon technology for a variety of applications, such as piezo-electric micromachined ultrasonic transducers (pMUTs), which represent a new approach to ultrasound detection and generation. For ultrasound-radiating applications, thicker PZT films are preferred because generative force and response speed of the diaphragm-type transducers increase with increasing film thickness. However, integration of 4- to 20-microm thick PZT films on silicon wafer, either the deposition or the patterning, is still a bottleneck in the micromachining process. This paper reports on a diaphragm-type pMUT. A composite coating technique based on chemical solution deposition and high-energy ball milled powder has been used to fabricate thick PZT films. Micromachining of the pMUTs using such thick films has been investigated. The fabricated pMUT with crack-free PZT films up to 7-microm thick was evaluated as an ultrasonic transmitter. The generated sound pressure level of up to 120 dB indicates that the fabricated pMUT has very good ultrasound-radiating performance and, therefore, can be used to compose pMUT arrays for generating ultrasound beam with high directivity in numerous applications. The pMUT arrays also have been demonstrated.

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.

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

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.

Momentum-resolved observations of the phonon instability driving geometric improper ferroelectricity in yttrium manganite

DOE PAGES

Bansal, Dipanshu; Niedziela, Jennifer L.; Sinclair, Ryan; ...

2018-01-02

Magnetoelectrics offer tantalizing opportunities for devices coupling ferroelectricity and magnetism but remain difficult to realize. Breakthrough strategies could circumvent the mutually exclusive origins of magnetism and ferroelectricity by exploiting the interaction of multiple phonon modes in geometric improper and hybrid improper ferroelectrics. Yet, the proposed instability of a zone-boundary phonon mode, driving the emergence of ferroelectricity via coupling to a polar mode, remains to be directly observed. Here, we provide previously missing evidence for this scenario in the archetypal improper ferroelectric, yttrium manganite, through comprehensive scattering measurements of the atomic structure and phonons, supported with first-principles simulations. Our experiments andmore » theoretical modeling resolve the origin of the unusual temperature dependence of the polarization and rule out a reported double-step ferroelectric transition. These results emphasize the critical role of phonon anharmonicity in rationalizing lattice instabilities in improper ferroelectrics and show that including these effects in simulations could facilitate the design of magnetoelectrics.« less

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

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.

Momentum-resolved observations of the phonon instability driving geometric improper ferroelectricity in yttrium manganite

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

Bansal, Dipanshu; Niedziela, Jennifer L.; Sinclair, Ryan

Magnetoelectrics offer tantalizing opportunities for devices coupling ferroelectricity and magnetism but remain difficult to realize. Breakthrough strategies could circumvent the mutually exclusive origins of magnetism and ferroelectricity by exploiting the interaction of multiple phonon modes in geometric improper and hybrid improper ferroelectrics. Yet, the proposed instability of a zone-boundary phonon mode, driving the emergence of ferroelectricity via coupling to a polar mode, remains to be directly observed. Here, we provide previously missing evidence for this scenario in the archetypal improper ferroelectric, yttrium manganite, through comprehensive scattering measurements of the atomic structure and phonons, supported with first-principles simulations. Our experiments andmore » theoretical modeling resolve the origin of the unusual temperature dependence of the polarization and rule out a reported double-step ferroelectric transition. These results emphasize the critical role of phonon anharmonicity in rationalizing lattice instabilities in improper ferroelectrics and show that including these effects in simulations could facilitate the design of magnetoelectrics.« less

Momentum-resolved observations of the phonon instability driving geometric improper ferroelectricity in yttrium manganite.

PubMed

Bansal, Dipanshu; Niedziela, Jennifer L; Sinclair, Ryan; Garlea, V Ovidiu; Abernathy, Douglas L; Chi, Songxue; Ren, Yang; Zhou, Haidong; Delaire, Olivier

2018-01-02

Magnetoelectrics offer tantalizing opportunities for devices coupling ferroelectricity and magnetism but remain difficult to realize. Breakthrough strategies could circumvent the mutually exclusive origins of magnetism and ferroelectricity by exploiting the interaction of multiple phonon modes in geometric improper and hybrid improper ferroelectrics. Yet, the proposed instability of a zone-boundary phonon mode, driving the emergence of ferroelectricity via coupling to a polar mode, remains to be directly observed. Here, we provide previously missing evidence for this scenario in the archetypal improper ferroelectric, yttrium manganite, through comprehensive scattering measurements of the atomic structure and phonons, supported with first-principles simulations. Our experiments and theoretical modeling resolve the origin of the unusual temperature dependence of the polarization and rule out a reported double-step ferroelectric transition. These results emphasize the critical role of phonon anharmonicity in rationalizing lattice instabilities in improper ferroelectrics and show that including these effects in simulations could facilitate the design of magnetoelectrics.

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

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

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%.

Hidden transition in multiferroic and magnetodielectric CuCrO2 evidenced by ac-susceptibility

NASA Astrophysics Data System (ADS)

Shukla, Kaushak K.; Pal, Arkadeb; Singh, Abhishek; Singh, Rahul; Saha, J.; Sinha, A. K.; Ghosh, A. K.; Patnaik, S.; Awasthi, A. M.; Chatterjee, Sandip

2017-04-01

Ferroelectric polarization, magnetic-field dependence of the dielectric constant and ac and dc magnetizations of frustrated CuCrO2 have been measured. A new spin freezing transition below 32 K is observed which is thermally driven. The nature of the spin freezing is to be a single-ion process. Dilution by the replacements of Cr ions by magnetic Mn ions showed suppression of the spin freezing transition suggesting it to be fundamentally a single-ion freezing process. The observed freezing, which is seemingly associated to geometrical spin frustration, represents a novel form of magnetic glassy behavior.

Correlation of Microwave Dielectric Properties and Microstructure of Unpatterned Ferroelectric Thin Films

DTIC Science & Technology

2003-04-03

technique. Ba acetate, Sr acetate, and Ti isopropoxide were used as precursors to form BST. Acetic acid and 2-methoxyethanol were used as solvents and...resulting from the generation of oxygen vacancy can hop between different titanium ions and provide a mechanism for dielectric losses, 2+the

Strain-induced phenomenon in complex oxide thin films

NASA Astrophysics Data System (ADS)

Haislmaier, Ryan

Complex oxide materials wield an immense spectrum of functional properties such as ferroelectricity, ferromagnetism, magnetoelectricity, optoelectricity, optomechanical, magnetoresistance, superconductivity, etc. The rich coupling between charge, spin, strain, and orbital degrees of freedom makes this material class extremely desirable and relevant for next generation electronic devices and technologies which are trending towards nanoscale dimensions. Development of complex oxide thin film materials is essential for realizing their integration into nanoscale electronic devices, where theoretically predicted multifunctional capabilities of oxides could add tremendous value. Employing thin film growth strategies such as epitaxial strain and heterostructure interface engineering can greatly enhance and even unlock novel material properties in complex oxides, which will be the main focus of this work. However, physically incorporating oxide materials into devices remains a challenge. While advancements in molecular beam epitaxy (MBE) of thin film oxide materials has led to the ability to grow oxide materials with atomic layer precision, there are still major limitations such as controlling stoichiometric compositions during growth as well as creating abrupt interfaces in multi-component layered oxide structures. The work done in this thesis addresses ways to overcome these limitations in order to harness intrinsic material phenomena. The development of adsorption-controlled stoichiometric growth windows of CaTiO3 and SrTiO3 thin film materials grown by hybrid MBE where Ti is supplied using metal-organic titanium tetraisopropoxide material is thoroughly outlined. These growth windows enable superior epitaxial strain-induced ferroelectric and dielectric properties to be accessed as demonstrated by chemical, structural, electrical, and optical characterization techniques. For tensile strained CaTiO3 and compressive strained SrTiO 3 films, the critical effects of nonstoichiometry on ferroelectric properties are investigated, where enhanced ferroelectric responses are only found for stoichiometric films grown inside of the growth windows, whereas outside of the optimal growth window conditions, ferroelectric properties are greatly deteriorated and eventually disappear for highly nonstoichiometric film compositions. Utilizing these stoichiometric growth windows, high temperature polar phase transitions are discovered for compressively strained CaTiO3 films with transition temperatures in excess of 700 K, rendering this material as a strong candidate for high temperature electronic applications. Beyond the synthesis of single phase materials using hybrid MBE, a methodology is presented for constructing layered (SrTiO3)n/(CaTiO 3)n superlattice structures, where precise control over the unit cell layering thickness (n) is demonstrated using in-situ reflection high energy electron diffraction. The effects of interface roughness and layering periodicity (n) on the strain-induced ferroelectric properties for a series of n=1-10 (SrTiO3)n/(CaTiO3) n superlattice films are investigated. It is found that the stabilization of a ferroelectric phase is independent of n, but is however strongly dominated by the degree of interface roughness which is quantified by measuring the highest nth order X-ray diffraction peak splitting of each superlattice film. A counter-intuitive realization is made whereby a critical amount of interface roughness is required in order to enable the formation of the predicted strain-stabilized ferroelectric phase, whereas sharp interfaces actually suppress this ferroelectric phase from manifesting. It is shown how high-quality complex oxide superlattices can be constructed using hybrid MBE technique, allowing the ability to control layered materials at the atomic scale. Furthermore, a detailed growth methodology is provided for constructing a layered n=4 SrO(SrTiO3)n Ruddlesden-Popper (RP) phase by hybrid MBE, where the ability to deposit single monolayers of SrO and TiO2 is utilized to build the RP film structure over a time period of 5 hours. This is the first time that a thin film RP phase has been grown using hybrid MBE, where an a stable control over the fluxes is demonstrated during relatively long time periods of growth, which advantageously facilitates the synthesis of high-quality RP materials with excellent structural and chemical homogeneity. Additionally, this work demonstrates some major advancements in optical second harmonic generation (SHG) characterization techniques of ferroelectric thin film materials. The SHG characterization techniques developed here proved to be the 'bread-and-butter' for most of the work performed in this thesis, providing a powerful tool for identifying the existence of strain-induced ferroelectric phases, including their temperature dependence and polar symmetry. The work presented in this dissertation will hopefully provide a preliminary road map for future hybrid MBE growers, scientists and researchers, to develop and investigate epitaxial strain and heterostructure layering induced phenomena in other complex oxide systems.

PLL jitter reduction by utilizing a ferroelectric capacitor as a VCO timing element.

PubMed

Pauls, Greg; Kalkur, Thottam S

2007-06-01

Ferroelectric capacitors have steadily been integrated into semiconductor processes due to their potential as storage elements within memory devices. Polarization reversal within ferroelectric capacitors creates a high nonlinear dielectric constant along with a hysteresis profile. Due to these attributes, a phase-locked loop (PLL), when based on a ferroelectric capacitor, has the advantage of reduced cycle-to-cycle jitter. PLLs based on ferroelectric capacitors represent a new research area for reduction of oscillator jitter.

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.

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 Field Effect Transistor Model Using Partitioned Ferroelectric Layer and Partial Polarization

NASA Technical Reports Server (NTRS)

MacLeod, Todd C.; Ho, Fat D.

2004-01-01

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

Molecular Catalysis at Polarized Interfaces Created by Ferroelectric BaTiO3 (Postprint)

DTIC Science & Technology

2017-02-06

product ratio to 4.5 : 1.0. Next, 4b was attached to various ferroelectric and non-ferroelectric oxides studied . Reactions performed with 2 mM 1 and...interfaces without applying a voltage. We studied the effects of ferroelectric oxides on the selectivity of an Rh porphyrin-catalyzed carbene...rearrangement. The addition of ferroelectric BaTiO3 nanoparticles to the reaction solution changed the product ratio in the same direction and by a similar

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

Visible Light-Induced Photocatalytic and Antibacterial Activity of Li-Doped Bi0.5Na0.45K0.5TiO3-BaTiO3 Ferroelectric Ceramics

NASA Astrophysics Data System (ADS)

Kushwaha, H. S.; Halder, Aditi; Jain, D.; Vaish, Rahul

2015-11-01

The visible light-active ferroelectric photocatalyst Bi0.5Na0.45Li0.05K0.5TiO3-BaTiO3 (BNKLBT) was synthesized by a solid-state method and its photocatalytic, photoelectrochemical, and antibacterial properties were investigated. In a chronoamperometric study the current density under visible light was 30 μA/cm2, which is three times more than that observed under dark conditions. The compound's visible light photocatalytic activity was investigated for degradation of an organic dye (methyl orange) and an estrogenic pollutant (estriol).The kinetic rate constants calculated for photocatalytic degradation of methyl orange and estriol were 0.007 and 0.056 min-1, respectively. High photocatalytic and photoelectrochemical activity was a result of effective separation of photo-generated charge carriers, because of the ferroelectric nature of the catalyst. The effect of different charge-trapping agents on photocatalytic degradation was studied to investigate the effect of active species and the degradation pathway. Antimicrobial activity was investigated for Escherichia coli and Aspergillus flavus. The anti-bacterial action of BNKLBT was compared with that of the commercial antibiotic kanamycin (k30).

Polarization and resistive switching behavior of ferroelectric tunnel junctions with transition metal dichalcogenides

NASA Astrophysics Data System (ADS)

Li, Tao; Lipatov, Alexey; Sharma, Pankaj; Lee, Hyungwoo; Eom, Chang-Beom; Sinitskii, Alexander; Gruverman, Alexei; Alexei Gruverman Team; Alexander Sinitskii Team; Chang-Beom Eom Team

Transition metal dichalcogenides (TMDs) are emerging 2-dimensional (2D) materials of the MX2 type, where M is a transition metal atom (Mo, W, Ti, Sn, Zr, etc.) and X is a chalcogen atom (S, Se, or Te.). Comparing to graphene, TMDs have a sizable band gap and can be metal, half-metal, semiconductor or superconductor. Their band structures can be tuned by external bias voltage, mechanical force, or light illumination. Their rich physical properties make TMDs potential candidates for a variety of applications in nanoelectronics and optoelectronics. Ferroelectric tunnel junctions (FTJs) are actively studied as a next-generation of non-volatile memory elements. An FTJ comprises a ferroelectric tunnel barrier sandwiched between two electrodes. In this work, we investigate the resistive switching behavior of MoS2/BaTiO3-based FTJs. The ON/OFF ratio can be modulated via electric or mechanical control of the switched polarization fraction opening a possibility of tunable electroresistance effect. Effect of optical illumination on the polarization reversal dynamics has been observed and analyzed based on the polarization-induced modulation of the MoS2 layered electronic properties.

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 appropriate systems.

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 material-dependent operating temperature, the predicted built-in electric fields can potentially drive the aging and electrical fatigue of the system to further skew the shape of the hysteresis loops.

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.

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 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%.

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

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

Room-temperature ferroelectricity of SrTiO{sub 3} films modulated by cation concentration

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

Yang, Fang; Zhang, Qinghua; Yang, Zhenzhong

2015-08-24

The room-temperature ferroelectricity of SrTiO{sub 3} is promising for oxide electronic devices controlled by multiple fields. An effective way to control the ferroelectricity is highly demanded. Here, we show that the off-centered antisite-like defects in SrTiO{sub 3} films epitaxially grown on Si (001) play the determinative role in the emergence of room-temperature ferroelectricity. The density of these defects changes with the film cation concentration sensitively, resulting in a varied coercive field of the ferroelectric behavior. Consequently, the room-temperature ferroelectricity of SrTiO{sub 3} films can be effectively modulated by tuning the temperature of metal sources during the molecular beam epitaxy growth.more » Such an easy and reliable modulation of the ferroelectricity enables the flexible engineering of multifunctional oxide electronic devices.« 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

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.

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.

Theoretical model for thin ferroelectric films and the multilayer structures based on them

NASA Astrophysics Data System (ADS)

Starkov, A. S.; Pakhomov, O. V.; Starkov, I. A.

2013-06-01

A modified Weiss mean-field theory is used to study the dependence of the properties of a thin ferroelectric film on its thickness. The possibility of introducing gradient terms into the thermodynamic potential is analyzed using the calculus of variations. An integral equation is introduced to generalize the well-known Langevin equation to the case of the boundaries of a ferroelectric. An analysis of this equation leads to the existence of a transition layer at the interface between ferroelectrics or a ferroelectric and a dielectric. The permittivity of this layer is shown to depend on the electric field direction even if the ferroelectrics in contact are homogeneous. The results obtained in terms of the Weiss model are compared with the results of the models based on the correlation effect and the presence of a dielectric layer at the boundary of a ferroelectric and with experimental data.

Electro-Active Transducer Using Radial Electric Field To Produce/Motion Sense Out-Of-Plane Transducer

NASA Technical Reports Server (NTRS)

Bryant, Robert G. (Inventor); Fox, Robert L. (Inventor)

2006-01-01

An electro-active transducer includes a ferroelectric material sandwiched by first and second electrode patterns. When the device is used as an actuator, the first and second electrode patterns are configured to introduce an electric field into the ferroelectric material when voltage is applied to the electrode patterns. When the device is used as a sensor. the first and second electrode patterns are configured to introduce an electric field into the ferroelectric material when the ferroelectric material experiences deflection in a direction substantially perpendicular thereto. In each case, the electrode patterns are designed to cause the electric field to: i) originate at a region of the ferroelectric material between the first and second electrode patterns. and ii) extend radially outward from the region of the ferroelectric material (at which the electric field originates) and substantially parallel to the ferroelectric material s plane.

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

Switchable electric polarization and ferroelectric domains in a metal-organic-framework

DOE PAGES

Jain, Prashant; Stroppa, Alessandro; Nabok, Dmitrii; ...

2016-09-30

Multiferroics and magnetoelectrics with coexisting and coupled multiple ferroic orders are materials promising new technological advances. While most studies have focused on single-phase or heterostructures of inorganic materials, a new class of materials called metal–organic frameworks (MOFs) has been recently proposed as candidate materials demonstrating interesting new routes for multiferroism and magnetoelectric coupling. Herein, we report on the origin of multiferroicity of (CH 3) 2NH 2Mn(HCOO) 3 via direct observation of ferroelectric domains using second-harmonic generation techniques. For the first time, we observe how these domains are organized (sized in micrometer range), and how they are mutually affected by appliedmore » electric and magnetic fields. Lastly, calculations provide an estimate of the electric polarization and give insights into its microscopic origin.« less

Ferroelectric Emission Cathodes for Low-Power Electric Propulsion

NASA Technical Reports Server (NTRS)

Kovaleski, Scott D.; Burke, Tom (Technical Monitor)

2002-01-01

Low- or no-flow electron emitters are required for low-power electric thrusters, spacecraft plasma contactors, and electrodynamic tether systems to reduce or eliminate the need for propellant/expellant. Expellant-less neutralizers can improve the viability of very low-power colloid thrusters, field emission electric propulsion devices, ion engines, Hall thrusters, and gridded vacuum arc thrusters. The NASA Glenn Research Center (GRC) is evaluating ferroelectric emission (FEE) cathodes as zero expellant flow rate cathode sources for the applications listed above. At GRC, low voltage (100s to approx. 1500 V) operation of FEE cathodes is examined. Initial experiments, with unipolar, bipolar, and RF burst applied voltage, have produced current pulses 250 to 1000 ns in duration with peak currents of up to 2 A at voltages at or below 1500 V. In particular, FEE cathodes driven by RF burst voltages from 1400 to 2000 V peak to peak, at burst frequencies from 70 to 400 kHz, emitted average current densities from 0.1 to 0.7 A/sq cm. Pulse repeatability as a function of input voltage has been initially established. Reliable emission has been achieved in air background at pressures as high as 10(exp -6) Torr.

Oxyhalides: A new class of high-TC multiferroic materials

PubMed Central

Zhao, Li; Fernández-Díaz, Maria Teresa; Tjeng, Liu Hao; Komarek, Alexander C.

2016-01-01

Magnetoelectric multiferroics have attracted enormous attention in the past years because of their high potential for applications in electronic devices, which arises from the intrinsic coupling between magnetic and ferroelectric ordering parameters. The initial finding in TbMnO3 has triggered the search for other multiferroics with higher ordering temperatures and strong magnetoelectric coupling for applications. To date, spin-driven multiferroicity is found mainly in oxides, as well as in a few halogenides. We report multiferroic properties for synthetic melanothallite Cu2OCl2, which is the first discovery of multiferroicity in a transition metal oxyhalide. Measurements of pyrocurrent and the dielectric constant in Cu2OCl2 reveal ferroelectricity below the Néel temperature of ~70 K. Thus, melanothallite belongs to a new class of multiferroic materials with an exceptionally high critical temperature. Powder neutron diffraction measurements reveal an incommensurate magnetic structure below TN, and all magnetic reflections can be indexed with a propagation vector [0.827(7), 0, 0], thus discarding the claimed pyrochlore-like “all-in–all-out” spin structure for Cu2OCl2, and indicating that this transition metal oxyhalide is, indeed, a spin-induced multiferroic material. PMID:27386552

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

Aparnadevi, N.; Department of Nuclear Physics, University of Madras, Guindy Campus, Chennai 600 025; Saravana Kumar, K.

Phase pure NdFeO{sub 3} has been achieved using high energy ball milling of oxide precursors with subsequent sintering. It is established that structural arrangement of NdFeO{sub 3} regulates the multifunctional feature of the material. Rietveld refinement of the room temperature X-ray diffraction pattern shows that the Fe-O-Fe bond angle significantly favors the super exchange interaction, which is predominantly antiferromagnetic in nature. Magnetization measurement illustrates antiferromagnetic behaviour with a weak ferromagnetic component caused by the canted nature of the Fe{sup 3+} spins at room temperature. Absorption bands in the visible ambit, apparent from the UV-Vis diffuse reflectance studies, is found duemore » to the crystal ligand field of octahedral oxygen environment of Fe{sup 3+} ions. The direct band gap is estimated to be 2.39 eV from the diffuse reflectance spectrum. The lossy natured ferroelectric loop having a maximum polarization of 0.23 μC/cm{sup 2} at room temperature is found to be driven by the non-collinear magnetic structure with reverse Dzyaloshinskii–Moriya effect. Magnetic field has influence on the dielectric constant as evident from the impedance spectroscopy, indicating the strong coupling between ferroelectric and the magnetic structure of NdFeO{sub 3}.« less

Electric modulation of conduction in multiferroic Ca-doped BiFeO3 films.

PubMed

Yang, C-H; Seidel, J; Kim, S Y; Rossen, P B; Yu, P; Gajek, M; Chu, Y H; Martin, L W; Holcomb, M B; He, Q; Maksymovych, P; Balke, N; Kalinin, S V; Baddorf, A P; Basu, S R; Scullin, M L; Ramesh, R

2009-06-01

Many interesting materials phenomena such as the emergence of high-Tc superconductivity in the cuprates and colossal magnetoresistance in the manganites arise out of a doping-driven competition between energetically similar ground states. Doped multiferroics present a tantalizing evolution of this generic concept of phase competition. Here, we present the observation of an electronic conductor-insulator transition by control of band-filling in the model antiferromagnetic ferroelectric BiFeO3 through Ca doping. Application of electric field enables us to control and manipulate this electronic transition to the extent that a p-n junction can be created, erased and inverted in this material. A 'dome-like' feature in the doping dependence of the ferroelectric transition is observed around a Ca concentration of approximately 1/8, where a new pseudo-tetragonal phase appears and the electric modulation of conduction is optimized. Possible mechanisms for the observed effects are discussed on the basis of the interplay of ionic and electronic conduction. This observation opens the door to merging magnetoelectrics and magnetoelectronics at room temperature by combining electronic conduction with electric and magnetic degrees of freedom already present in the multiferroic BiFeO3.

Electric modulation of conduction in multiferroic Ca-doped BiFeO3 films

NASA Astrophysics Data System (ADS)

Yang, C.-H.; Seidel, J.; Kim, S. Y.; Rossen, P. B.; Yu, P.; Gajek, M.; Chu, Y. H.; Martin, L. W.; Holcomb, M. B.; He, Q.; Maksymovych, P.; Balke, N.; Kalinin, S. V.; Baddorf, A. P.; Basu, S. R.; Scullin, M. L.; Ramesh, R.

2009-06-01

Many interesting materials phenomena such as the emergence of high-Tc superconductivity in the cuprates and colossal magnetoresistance in the manganites arise out of a doping-driven competition between energetically similar ground states. Doped multiferroics present a tantalizing evolution of this generic concept of phase competition. Here, we present the observation of an electronic conductor-insulator transition by control of band-filling in the model antiferromagnetic ferroelectric BiFeO3 through Ca doping. Application of electric field enables us to control and manipulate this electronic transition to the extent that a p-n junction can be created, erased and inverted in this material. A `dome-like' feature in the doping dependence of the ferroelectric transition is observed around a Ca concentration of ~1/8, where a new pseudo-tetragonal phase appears and the electric modulation of conduction is optimized. Possible mechanisms for the observed effects are discussed on the basis of the interplay of ionic and electronic conduction. This observation opens the door to merging magnetoelectrics and magnetoelectronics at room temperature by combining electronic conduction with electric and magnetic degrees of freedom already present in the multiferroic BiFeO3.

Tunable short-wavelength spin wave excitation from pinned magnetic domain walls

PubMed Central

Van de Wiele, Ben; Hämäläinen, Sampo J.; Baláž, Pavel; Montoncello, Federico; van Dijken, Sebastiaan

2016-01-01

Miniaturization of magnonic devices for wave-like computing requires emission of short-wavelength spin waves, a key feature that cannot be achieved with microwave antennas. In this paper, we propose a tunable source of short-wavelength spin waves based on highly localized and strongly pinned magnetic domain walls in ferroelectric-ferromagnetic bilayers. When driven into oscillation by a microwave spin-polarized current, the magnetic domain walls emit spin waves with the same frequency as the excitation current. The amplitude of the emitted spin waves and the range of attainable excitation frequencies depend on the availability of domain wall resonance modes. In this respect, pinned domain walls in magnetic nanowires are particularly attractive. In this geometry, spin wave confinement perpendicular to the nanowire axis produces a multitude of domain wall resonances enabling efficient spin wave emission at frequencies up to 100 GHz and wavelengths down to 20 nm. At high frequency, the emission of spin waves in magnetic nanowires becomes monochromatic. Moreover, pinning of magnetic domain wall oscillators onto the same ferroelectric domain boundary in parallel nanowires guarantees good coherency between spin wave sources, which opens perspectives towards the realization of Mach-Zehnder type logic devices and sensors. PMID:26883893

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.

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

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.

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

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.

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.

Interrelationship between flexoelectricity and strain gradient elasticity in ferroelectric nanofilms: A phase field study

NASA Astrophysics Data System (ADS)

Jiang, Limei; Xu, Xiaofei; Zhou, Yichun

2016-12-01

With the development of the integrated circuit technology and decreasing of the device size, ferroelectric films used in nano ferroelectric devices become thinner and thinner. Along with the downscaling of the ferroelectric film, there is an increasing influence of two strain gradient related terms. One is the strain gradient elasticity and the other one is flexoelectricity. To investigate the interrelationship between flexoelectricity and strain gradient elasticity and their combined effect on the domain structure in ferroelectric nanofilms, a phase field model of flexoelectricity and strain gradient elasticity on the ferroelectric domain evolution is developed based on Mindlin's theory of strain-gradient elasticity. Weak form is derived and implemented in finite element formulations for numerically solving the model equations. The simulation results show that upper bounds for flexoelectric coefficients can be enhanced by increasing strain gradient elasticity coefficients. While a large flexoelectricity that exceeds the upper bound can induce a transition from a ferroelectric state to a modulated/incommensurate state, a large enough strain gradient elasticity may lead to a conversion from an incommensurate state to a ferroelectric state. Strain gradient elasticity and the flexoelectricity have entirely opposite effects on polarization. The observed interrelationship between the strain gradient elasticity and flexoelectricity is rationalized by an analytical solution of the proposed theoretical model. The model proposed in this paper could help us understand the mechanism of phenomena observed in ferroelectric nanofilms under complex electromechanical loads and provide some guides on the practical application of ferroelectric nanofilms.

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.

Optical spectroscopic study of multiferroic BiFeO3 and LuFe2O4

NASA Astrophysics Data System (ADS)

Xu, Xiaoshan

2010-03-01

Iron-based multiferroics such as BiFeO3 and LuFe2O4 exhibit the highest magnetic and ferroelectric ordering temperatures among known multiferroics. LuFe2O4 is a frustrated system with several phase transitions that result in electronically driven multiferroicity. To understand how this peculiar multiferroic mechanism correlates with magnetism, we studied electronic excitations by optical spectroscopy and other complementary techniques. We show that the charge order, which determines the dielectric properties, is due to the ``order by fluctuation'' mechanism, evidenced by the onset of charge fluctuation well below the charge ordering transition. We also find a low temperature monoclinic distortion driven by both temperature and magnetic field, indicating strong coupling between structure, magnetism and charge order. BiFeO3 is the only known single phase multiferroics with room temperature magnetism and ferroelectricity. To investigate the spin-charge coupling, we measured the optical properties of BiFeO3. We find that the absorption onset occurs due to on-site Fe^3+ excitations at 1.41 and 1.90 eV. Temperature and magnetic-field-induced spectral changes reveal complex interactions between on-site crystal-field and magnetic excitations in the form of magnon sidebands. The sensitivity of the magnon sidebands allows us to map out the magnetic-field temperature phase diagram which demonstrates optical evidence for spin spiral quenching above 20 T and suggests a spin domain reorientation near 10 T. Work done in collaboration with T.V. Brinzari, R.C. Rai, M. Angst, R.P. Hermann, A.D. Christianson, J.-W. Kim, Z. Islam, B.C. Sales, D. Mandrus, S. Lee, Y.H. Chu, L. W. Martin, A. Kumar, R. Ramesh, S.W. Cheong, S. McGill, and J.L. Musfeldt.

Piezoelectric control of magnetoelectric coupling driven non-volatile memory switching and self cooling effects in FE/FSMA multiferroic heterostructures

NASA Astrophysics Data System (ADS)

Singh, Kirandeep; Kaur, Davinder

2017-02-01

The manipulation of magnetic states and materials' spin degree-of-freedom via a control of an electric (E-) field has been recently pursued to develop magnetoelectric (ME) coupling-driven electronic data storage devices with high read/write endurance, fast dynamic response, and low energy dissipation. One major hurdle for this approach is to develop reliable materials which should be compatible with prevailing silicon (Si)-based complementary metal-oxide-semiconductor (CMOS) technology, simultaneously allowing small voltage for the tuning of magnetization switching. In this regard, multiferroic heterostructures where ferromagnetic (FM) and ferroelectric (FE) layers are alternatively grown on conventional Si substrates are promising as the piezoelectric control of magnetization switching is anticipated to be possible by an E-field. In this work, we study the ferromagnetic shape memory alloys based PbZr0.52Ti0.48O3/Ni50Mn35In15 (PZT/Ni-Mn-In) multiferroic heterostructures, and investigate their potential for CMOS compatible non-volatile magnetic data storage applications. We demonstrate the voltage-impulse controlled nonvolatile, reversible, and bistable magnetization switching at room temperature in Si-integrated PZT/Ni-Mn-In thin film multiferroic heterostructures. We also thoroughly unveil the various intriguing features in these materials, such as E-field tuned ME coupling and magnetocaloric effect, shape memory induced ferroelectric modulation, improved fatigue endurance as well as Refrigeration Capacity (RC). This comprehensive study suggests that these novel materials have a great potential for the development of unconventional nanoscale memory and refrigeration devices with self-cooling effect and enhanced refrigeration efficiency, thus providing a new venue for their applications.

Space-charge-mediated anomalous ferroelectric switching in P(VDF-TrEE) polymer films.

PubMed

Hu, Weijin; Wang, Zhihong; Du, Yuanmin; Zhang, Xi-Xiang; Wu, Tom

2014-11-12

We report on the switching dynamics of P(VDF-TrEE) copolymer devices and the realization of additional substable ferroelectric states via modulation of the coupling between polarizations and space charges. The space-charge-limited current is revealed to be the dominant leakage mechanism in such organic ferroelectric devices, and electrostatic interactions due to space charges lead to the emergence of anomalous ferroelectric loops. The reliable control of ferroelectric switching in P(VDF-TrEE) copolymers opens doors toward engineering advanced organic memories with tailored switching characteristics.

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.

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.

Organometal Halide Perovskite Solar Absorbers and Ferroelectric Nanocomposites for Harvesting Solar Energy

NASA Astrophysics Data System (ADS)

Hettiarachchi, Chaminda Lakmal

Organometal halide perovskite absorbers such as methylammonium lead iodide chloride (CH3NH3PbI3-xClx), have emerged as an exciting new material family for photovoltaics due to its appealing features that include suitable direct bandgap with intense light absorbance, band gap tunability, ultra-fast charge carrier generation, slow electron-hole recombination rates, long electron and hole diffusion lengths, microsecond-long balanced carrier mobilities, and ambipolarity. The standard method of preparing CH3NH3PbI3-xClx perovskite precursors is a tedious process involving multiple synthesis steps and, the chemicals being used (hydroiodic acid and methylamine) are quite expensive. This work describes a novel, single-step, simple, and cost-effective solution approach to prepare CH3NH3PbI3-xClx thin films by the direct reaction of the commercially available CH3NH 3Cl (or MACl) and PbI2. A detailed analysis of the structural and optical properties of CH3NH3PbI3-xCl x thin films deposited by aerosol assisted chemical vapor deposition is presented. Optimum growth conditions have been identified. It is shown that the deposited thin films are highly crystalline with intense optical absorbance. Charge carrier separation of these thin films can be enhanced by establishing a local internal electric field that can reduce electron-hole recombination resulting in increased photo current. The intrinsic ferroelectricity in nanoparticles of Barium Titanate (BaTiO3 -BTO) embedded in the solar absorber can generate such an internal field. A hybrid structure of CH3NH 3PbI3-xClx perovskite and ferroelectric BTO nanocomposite FTO/TiO2/CH3NH3PbI3-xClx : BTO/P3HT/Cu as a new type of photovoltaic device is investigated. Aerosol assisted chemical vapor deposition process that is scalable to large-scale manufacturing was used for the growth of the multilayer structure. TiO 2 and P3HT with additives were used as ETL and HTL respectively. The growth process of the solar absorber layer includes the nebulization of a mixture of PbI2 and CH3NH3Cl perovskite precursors and BTO nanoparticles dissolved in DMF, and injection of the aerosol into the growth chamber and subsequent deposition on TiO2. While high percentage of BTO in the film increases the carrier separation, it also leads to reduced carrier generation. A model was developed to guide the optimum BTO nanoparticle concentration in the nanocomposite films. Characterization of perovskite solar cells indicated that ferroelectric polarization of BTO nanoparticles leads to the increase of the width of depletion regions in the perovskite layer hence the photo current was increased by one order of magnitude after poling the devices. The ferroelectric polarization of BTO nanoparticles within the perovskite solar absorber provides a new perspective for tailoring the working mechanism and photovoltaic performance of perovskite solar cells.

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

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

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

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 energy barriers. The energy difference between a hydrogen contaminated PTO and a pure PTO is considered as an energy penalty term induced by hydrogen contamination. Then, the effective Hamiltonian with the energy penalty is employed in MD simulations to investigate the effects of hydrogen contamination on the ferroelectric responses of PTO films. The hysteresis loops are presented and analyzed for PTO films with various concentrations of hydrogen impurities and thicknesses. Hydrogen contamination reduces the remnant polarization, especially for thin films. As the concentration of hydrogen impurities increases, the critical thickness increases. By analyzing the vertical cross section snapshots, it has been found that the hydrogen impurities near interfaces affect the polarization throughout the entire PTO film. To study the effect of the dead layer (depolarization field), the soft modes in the top and bottom layers are constrained to be zero, which gives rise to the reduced polarization and increased critical thickness. Negative capacitance is a new and hot topic, which was recently observed by experiment. It is a transient effect that correlated with depolarization field. Some preliminary results and application of negative capacitance are discussed.

Polycrystalline ferroelectric or multiferroic oxide articles on biaxially textured substrates and methods for making same

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

Goyal, Amit; Shin, Junsoo

A polycrystalline ferroelectric and/or multiferroic oxide article includes a substrate having a biaxially textured surface; at least one biaxially textured buffer layer supported by the substrate; and a biaxially textured ferroelectric or multiferroic oxide layer supported by the buffer layer. Methods for making polycrystalline ferroelectric and/or multiferroic oxide articles are also disclosed.

Oxygen-vacancy-related dielectric relaxation in SrBi2Ta1.8V0.2O9 ferroelectrics

NASA Astrophysics Data System (ADS)

Wu, Yun; Forbess, Mike J.; Seraji, Seana; Limmer, Steven J.; Chou, Tammy P.; Cao, Guozhong

2001-05-01

The strontium bismuth tantalate vanadate, SrBi2Ta1.8V0.2O9, (SBTV) layered perovskite ferroelectrics were made by solid state powder sintering. It was found that the SBTV ferroelectrics had the same crystal structure as that of strontium bismuth tantalate, SrBi2Ta2O9 (SBT), but an increased paraferroelectric transition temperature at ˜360 °C as compared to 305 °C for SBT. In addition, SBTV ferroelectrics showed a frequency dispersion at low frequencies and broadened dielectric peaks at the paraferroelectric transition temperature that shifted to a higher temperature with a reduced frequency. However, after a postsintering annealing at 850 °C in air for 60 h, SBTV ferroelectrics showed reduced dielectric constants and tangent loss, particularly at high temperatures. In addition, no frequency dependence of paraferroelectric transition was found in the annealed SBTV ferroelectrics. Furthermore, there was a significant reduction in dc conductivity with annealing. The prior results implied that the dielectric relaxation in the as-sintered SBTV ferroelectrics was most likely due to the oxygen-vacancy-related dielectric relaxation instead of relaxor ferroelectric behavior.

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-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.

Ferroelectricity in Ruddlesden-Popper Chalcogenide Perovskites for Photovoltaic Application: The Role of Tolerance Factor.

PubMed

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

2017-12-07

Chalcogenide perovskites with optimal band gap and desirable light absorption are promising for photovoltaic devices, whereas the absence of ferroelectricity limits their potential in applications. On the basis of first-principles calculations, we reveal the underlying mechanism of the paraelectric nature of Ba 3 Zr 2 S 7 observed in experiments and demonstrate a general rule for the appearance of ferroelectricity in chalcogenide perovskites with Ruddlesden-Popper (RP) A 3 B 2 X 7 structures. Group theoretical analysis shows that the tolerance factor is the primary factor that dominates the ferroelectricity. Both Ba 3 Zr 2 S 7 and Ba 3 Hf 2 S 7 with large tolerance factor are paraelectric because of the suppression of in-phase rotation that is indispensable to hybrid improper ferroelectricity. In contrast, Ca 3 Zr 2 S 7 , Ca 3 Hf 2 S 7 , Ca 3 Zr 2 Se 7 , and Ca 3 Hf 2 S 7 with small tolerance factor exhibit in-phase rotation and can be stable in the ferroelectric Cmc2 1 ground state with nontrivial polarization. These findings not only provide useful guidance to engineering ferroelectricity in RP chalcogenide perovskites but also suggest potential ferroelectric semiconductors for photovoltaic applications.

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.

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

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 by the voltage applied to rear surface of the ferroelectric; however, for current pulse durations on the order of microseconds, the surface plasma expansion into the gap can dominate current flow.

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

Moghadam, Reza M.; Xiao, Zhiyong; Ahmadi-Majlan, Kamyar

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 low-power field-effect devices that can be used for logic or memory. Essential to realizing such field-effect devices is the development of ferroelectric metal-oxide-semiconductor (MOS) capacitors, in which the polarization of a ferroelectric gate is coupled to the surface potential of a semiconducting channel. Here we demonstrate that ferroelectric MOS capacitors can be realized using single crystalline SrZrxTi1-xO3 (x= 0.7) that has been epitaxially grown on Ge. We find that themore » ferroelectric properties of SrZrxTi1-xO3 are exceptionally robust, as gate layers as thin as 5 nm give rise to hysteretic capacitance-voltage characteristics that are 2 V in width. The development of ferroelectric MOS capacitors with gate thicknesses that are technologically relevant opens a pathway to realize scalable ferroelectric field-effect devices.« less

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.

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)

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

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.

Size effects and realiability of barium strontium titanate thin films

NASA Astrophysics Data System (ADS)

Parker, Charles Bernard

Thin films of (Ba,Sr)TiO3 (BST) deposited by Liquid Source MOCVD were investigated. BST is a candidate dielectric for future-generation DRAM and as a tunable dielectric. Two areas of both scientific and commercial interest were investigated. The first area is the effect of decreasing dimension on ferroelectric properties. Several theories of size effects in ferroelectrics were evaluated. The dielectric response of a set of BST films of thicknesses from 15 to 580 nm was measured from 85 to 580 K. These films were extensively characterized and the boundary conditions that often influence size effects measurements were considered, including strain, finite screening length in the electrode, depolarization fields in the ferroelectric, atmospheric effects, control of stochiometry, and others. The data set was compared to the theoretical predictions and it was determined that Finite Size Scaling provided the best fit to the data. Using this theory, the predicted dielectric response was compared to the requirements of future generations of DRAM and was found to be sufficient, if film strain can be controlled. The second area is reliability. The types of lifetime-limiting electrical failure observed in BST are resistance degradation, time dependant dielectric breakdown (tddb), and noisy breakdown. Previous work on BST reliability has largely focused on resistance degradation at high temperature. This condition is only a small subset of experimental space. This work extends the understanding of BST failure into the low temperature regime and evaluates the effects of both DC and AC stress. It was found that tddb is the dominant failure mode at low temperature and resistance degradation is the dominant failure modes at high temperature. Synthesizing this work with previous work on resistance degradation allowed a failure framework to be developed. Rigorous extrapolation of resistance degradation and tddb lifetimes was compared to the requirements of future generations of DRAM and was found that while resistance degradation will not limit device lifetimes, tddb will. Refinement of BST processing will be necessary to reduce the defect causing tddb failure.

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.

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

Voltage control of magnetic single domains in Ni discs on ferroelectric BaTiO3

NASA Astrophysics Data System (ADS)

Ghidini, M.; Zhu, B.; Mansell, R.; Pellicelli, R.; Lesaine, A.; Moya, X.; Crossley, S.; Nair, B.; Maccherozzi, F.; Barnes, C. H. W.; Cowburn, R. P.; Dhesi, S. S.; Mathur, N. D.

2018-06-01

For 1 µm-diameter Ni discs on a BaTiO3 substrate, the local magnetization direction is determined by ferroelectric domain orientation as a consequence of growth strain, such that single-domain discs lie on single ferroelectric domains. On applying a voltage across the substrate, ferroelectric domain switching yields non-volatile magnetization rotations of 90°, while piezoelectric effects that are small and continuous yield non-volatile magnetization reversals that are non-deterministic. This demonstration of magnetization reversal without ferroelectric domain switching implies reduced fatigue, and therefore represents a step towards applications.

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 the metallic-like to nonmetallic transition. These results show that the thermoelectric properties found in SBN upon reduction are due to a change from (Srx,Ba1-x)Nb2O6-delta toward (Srx,Ba1-x)1.2Nb2O6-delta and the resulting carrier concentration associated with the additional Sr2+ and Ba2+ cations on the A-site. Relaxor ferroelectricity perturbs the electron transport, but is not a cause of enhanced thermoelectric properties. This points toward A-site doped tungsten bronze materials in general as interesting thermoelectric materials. Future work revolving around decreasing the octahedral tilt angle, increasing the d-orbital overlap, and determining the necessity of ferroelectric-thermoelectric coupling in relation to thermal conductivity could result in further optimization within this new interesting family of thermoelectric oxides. (Abstract shortened by ProQuest.).

Understanding the spin-driven polarizations in Bi MO3 (M = 3 d transition metals) multiferroics

NASA Astrophysics Data System (ADS)

Kc, Santosh; Lee, Jun Hee; Cooper, Valentino R.

Bismuth ferrite (BiFeO3) , a promising multiferroic, stabilizes in a perovskite type rhombohedral crystal structure (space group R3c) at room temperature. Recently, it has been reported that in its ground state it possess a huge spin-driven polarization. To probe the underlying mechanism of this large spin-phonon response, we examine these couplings within other Bi based 3 d transition metal oxides Bi MO3 (M = Ti, V, Cr, Mn, Fe, Co, Ni) using density functional theory. Our results demonstrate that this large spin-driven polarization is a consequence of symmetry breaking due to competition between ferroelectric distortions and anti-ferrodistortive octahedral rotations. Furthermore, we find a strong dependence of these enhanced spin-driven polarizations on the crystal structure; with the rhombohedral phase having the largest spin-induced atomic distortions along [111]. These results give us significant insights into the magneto-electric coupling in these materials which is essential to the magnetic and electric field control of electric polarization and magnetization in multiferroic based devices. Research is supported by the US Department of Energy, Office of Science, Basic Energy Sciences, Materials Science and Engineering Division and the Office of Science Early Career Research Program (V.R.C) and used computational resources at NERSC.

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-principles-based modeling of electric-field-induced phenomena in ferroelectric/antiferroelectric nanowires in order to address the aforementioned questions. (Abstract shortened by ProQuest.).

Perovskite oxides for visible-light-absorbing ferroelectric and photovoltaic materials.

PubMed

Grinberg, Ilya; West, D Vincent; Torres, Maria; Gou, Gaoyang; Stein, David M; Wu, Liyan; Chen, Guannan; Gallo, Eric M; Akbashev, Andrew R; Davies, Peter K; Spanier, Jonathan E; Rappe, Andrew M

2013-11-28

Ferroelectrics have recently attracted attention as a candidate class of materials for use in photovoltaic devices, and for the coupling of light absorption with other functional properties. In these materials, the strong inversion symmetry breaking that is due to spontaneous electric polarization promotes the desirable separation of photo-excited carriers and allows voltages higher than the bandgap, which may enable efficiencies beyond the maximum possible in a conventional p-n junction solar cell. Ferroelectric oxides are also stable in a wide range of mechanical, chemical and thermal conditions and can be fabricated using low-cost methods such as sol-gel thin-film deposition and sputtering. Recent work has shown how a decrease in ferroelectric layer thickness and judicious engineering of domain structures and ferroelectric-electrode interfaces can greatly increase the current harvested from ferroelectric absorber materials, increasing the power conversion efficiency from about 10(-4) to about 0.5 per cent. Further improvements in photovoltaic efficiency have been inhibited by the wide bandgaps (2.7-4 electronvolts) of ferroelectric oxides, which allow the use of only 8-20 per cent of the solar spectrum. Here we describe a family of single-phase solid oxide solutions made from low-cost and non-toxic elements using conventional solid-state methods: [KNbO3]1 - x[BaNi1/2Nb1/2O3 - δ]x (KBNNO). These oxides exhibit both ferroelectricity and a wide variation of direct bandgaps in the range 1.1-3.8 electronvolts. In particular, the x = 0.1 composition is polar at room temperature, has a direct bandgap of 1.39 electronvolts and has a photocurrent density approximately 50 times larger than that of the classic ferroelectric (Pb,La)(Zr,Ti)O3 material. The ability of KBNNO to absorb three to six times more solar energy than the current ferroelectric materials suggests a route to viable ferroelectric semiconductor-based cells for solar energy conversion and other applications.

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

DTIC Science & Technology

2006-03-31

crystals by the flux method and modified Bridgman technique, the growth results were hardly reproducible, and the quality of the crystals was still a serious... growth . 2.2.1.2.2) Solution Bridgman Growth A modified Bridgman method using excess of PbO as solvent was developed for the growth of PZNT91/9 crystals ...of growth , the grown crystal can be rotated via the A120 3 rod which was driven by a motor at a speed of 0 to 30 rmp. Figure 15(b) gives the

Realization of anomalous multiferroicity in free-standing graphene with magnetic adatoms

NASA Astrophysics Data System (ADS)

Marques, Y.; Ricco, L. S.; Dessotti, F. A.; Machado, R. S.; Shelykh, I. A.; de Souza, M.; Seridonio, A. C.

2016-11-01

It is generally believed that free-standing graphene does not demonstrate any ferroic properties. In the present work we revise this statement and show that a single graphene sheet with a pair of magnetic adatoms can be driven into ferroelectric (FE) and multiferroic (MF) phases by tuning the Dirac cones slope. The transition into the FE phase occurs gradually, but an anomalous MF phase appears abruptly by means of a quantum phase transition. Our findings suggest that such features should exist in graphene recently investigated by scanning tunneling microscopy [H. González-Herrero et al., Science 352, 437 (2016), 10.1126/science.aad8038].

Diffraction study of duty-cycle error in ferroelectric quasi-phase-matching gratings with Gaussian beam illumination

NASA Astrophysics Data System (ADS)

Dwivedi, Prashant Povel; Kumar, Challa Sesha Sai Pavan; Choi, Hee Joo; Cha, Myoungsik

2016-02-01

Random duty-cycle error (RDE) is inherent in the fabrication of ferroelectric quasi-phase-matching (QPM) gratings. Although a small RDE may not affect the nonlinearity of QPM devices, it enhances non-phase-matched parasitic harmonic generations, limiting the device performance in some applications. Recently, we demonstrated a simple method for measuring the RDE in QPM gratings by analyzing the far-field diffraction pattern obtained by uniform illumination (Dwivedi et al. in Opt Express 21:30221-30226, 2013). In the present study, we used a Gaussian beam illumination for the diffraction experiment to measure noise spectra that are less affected by the pedestals of the strong diffraction orders. Our results were compared with our calculations based on a random grating model, demonstrating improved resolution in the RDE estimation.

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.

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

NASA Astrophysics Data System (ADS)

Swedberg, Elena

Ferroelectric and antiferroelectric ultrathin films have attracted a lot of attention recently due to their remarkable properties and their potential to allow for device miniaturization in numerous applications. However, when the ferroelectric films are scaled down, it brings about an unavoidable depolarizing field. A partial surface charge compensation allows to control the residual depolarizing field and manipulate the properties of ultrathin ferroelectric films. In this dissertation we take advantage of atomistic first-principles-based simulations to expand our understanding of the role of the partial surface charge compensation in the properties of ferroelectric and antiferroelectric ultrathin films. The application of our computational methodology to study the effect of the partial surface charge compensation in ferroelectric ultrathin films led to the prediction that, depending on the quality of the surface charge compensation, ferroelectric thin films respond to an electric field in a qualitatively different manner. They can be tuned to behave like a linear dielectric, a ferroelectric or even an antiferroelectric. This effect was shown to exist in films with different mechanical boundary conditions and different crystal symmetries. There are a number of potential applications where such properties of ferroelectric thin films can be used. One of these potential applications is energy storage. We will show that, in the antiferroelectric regime, ferroelectric thin films exhibit drastic enhancement of energy storage density which is a desirable property. One of the most promising applications of ferroelectric ultrathin films that emerged only recently is the harvesting of the giant electrocaloric effect. Interestingly, despite numerous studies of the electrocaloric effect in ferroelectric thin films, it is presently unknown how a residual depolarizing field affects the electrocaloric properties of such films. Application of state-of-the-art computational methods 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 is possible to stabilize the ferroelectric phase in antiferroelectric films and what role the surface charge screening would play in such a transition. Motivated to address these fundamental questions, we used computational experiments to study antiferroelectric ultrathin films with a residual depolarizing field. Our studies led to the following predictions. We found that PbZrO3 thin films exhibit the ferroelectric phase upon scaling down and under the condition of efficient surface charge compensation. We also found a strong competition between the antiferroelectric and ferroelectric phases for the thin films of the critical size associated with antiferroelectric-ferroelectric phase transition. This finding motivated us to study the electrocaloric effect in PbZrO3 thin films with antiferroelectric-ferroelectric phase competition. We found that high tunability of the phase transition by the electric field leads to a wide range of temperatures associated with a strong electrocaloric effect. In addition, we found that epitaxial strain provides further tunability to the electrocaloric properties. In summary, our studies led to a broader and deeper understanding of the abundantly many roles surface charge compensation plays in ultrathin ferroelectrics and 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.

Polarization and interface charge coupling in ferroelectric/AlGaN/GaN heterostructure

NASA Astrophysics Data System (ADS)

Zhang, Min; Kong, Yuechan; Zhou, Jianjun; Xue, Fangshi; Li, Liang; Jiang, Wenhai; Hao, Lanzhong; Luo, Wenbo; Zeng, Huizhong

2012-03-01

Asymmetrical shift behaviors of capacitance-voltage (C-V) curve with opposite direction are observed in two AlGaN/GaN metal-ferroelectric-semiconductor (MFS) heterostructures with Pb(Zr,Ti)O3 and LiNbO3 gate dielectrics. By incorporating the switchable polar nature of the ferroelectric into a self-consistent calculation, the coupling effect between the ferroelectric and the interface charges is disclosed. The opposite initial orientation of ferroelectric dipoles determined by the interface charges is essentially responsible for the different C-V characteristics. A critical fixed charge density of -1.27 × 1013cm-2 is obtained, which plays a key role in the dependence of the C-V characteristic on the ferroelectric polarization. The results pave the way for design of memory devices based on MFS structure with heteropolar interface.

Bandgap behavior and singularity of the domain-induced light scattering through the pressure-induced ferroelectric transition in relaxor ferroelectric AxBa1-xNb2O6 (A: Sr,Ca)

NASA Astrophysics Data System (ADS)

Ruiz-Fuertes, J.; Gomis, O.; Segura, A.; Bettinelli, M.; Burianek, M.; Mühlberg, M.

2018-01-01

In this letter, we have investigated the electronic structure of AxBa1-xNb2O6 relaxor ferroelectrics on the basis of optical absorption spectroscopy in unpoled single crystals with A = Sr and Ca under high pressure. The direct character of the fundamental transition could be established by fitting Urbach's rule to the photon energy dependence of the absorption edge yielding bandgaps of 3.44(1) eV and 3.57(1) eV for A = Sr and Ca, respectively. The light scattering by ferroelectric domains in the pre-edge spectral range has been studied as a function of composition and pressure. After confirming with x-ray diffraction the occurrence of the previously observed ferroelectric to paraelelectric phase transition at 4 GPa, the light scattering produced by micro- and nano-ferroelectric domains at 3.3 eV in Ca0.28Ba0.72Nb2O6 has been probed. The direct bandgap remains virtually constant under compression with a drop of only 0.01 eV around the phase transition. Interestingly, we have also found that light scattering by the polar nanoregions in the paraelectric phase is comparable to the dispersion due to ferroelectric microdomains in the ferroelectric state. Finally, we have obtained that the bulk modulus of the ferroelectric phase of Ca0.28Ba0.72Nb2O6 is B0 = 222(9) GPa.

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.

Changing Dielectrics into Multiferroics---Alchemy Enabled by Strain

NASA Astrophysics Data System (ADS)

Schlom, Darrell

2011-03-01

Ferroelectric ferromagnets are exceedingly rare, fundamentally interesting multiferroic materials. The properties of what few compounds simultaneously exhibit these phenomena pale in comparison to useful ferroelectrics or ferromagnets: their spontaneous polarizations (Ps) or magnetizations (Ms) are smaller by a factor of 1000 or more. The same holds for (magnetic or electric) field-induced multiferroics. Recently, however, Fennie and Rabe proposed a new route to ferroelectric ferromagnets---transforming magnetically ordered insulators that are neither ferroelectric nor ferromagnetic, of which there are many, into ferroelectric ferromagnets using a single control parameter: strain. The system targeted, EuTi O3 , was predicted to simultaneously exhibit strong ferromagnetism (Ms ~ ~ ~7~μB /Eu) and strong ferroelectricity (Ps ~ ~ ~10~ μ C/cm2) under large biaxial compressive strain. These values are orders of magnitude higher than any known ferroelectric ferromagnet and rival the best materials that are solely ferroelectric or ferromagnetic. Hindered by the absence of an appropriate substrate to provide the desired compression, we show 3 both experimentally and theoretically the emergence of a multiferroic state under biaxial tension with the unexpected benefit that even lower misfits are required, thereby enabling higher quality crystalline films. The resulting genesis of a strong ferromagnetic ferroelectric points the way to high temperature manifestations of this spin-phonon coupling mechanism. Our work demonstrates that a single experimental parameter, strain, simultaneously controls multiple order parameters and is a viable alternative tuning parameter to composition for creating multiferroics. C.J. Fennie and K.M. Rabe, Phys. Rev. Lett. 97 (2006) 267602.

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.

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

Determination of ferroelectric contributions to electromechanical response by frequency dependent piezoresponse force microscopy.

PubMed

Seol, Daehee; Park, Seongjae; Varenyk, Olexandr V; Lee, Shinbuhm; Lee, Ho Nyung; Morozovska, Anna N; Kim, Yunseok

2016-07-28

Hysteresis loop analysis via piezoresponse force microscopy (PFM) is typically performed to probe the existence of ferroelectricity at the nanoscale. However, such an approach is rather complex in accurately determining the pure contribution of ferroelectricity to the PFM. Here, we suggest a facile method to discriminate the ferroelectric effect from the electromechanical (EM) response through the use of frequency dependent ac amplitude sweep with combination of hysteresis loops in PFM. Our combined study through experimental and theoretical approaches verifies that this method can be used as a new tool to differentiate the ferroelectric effect from the other factors that contribute to the EM response.

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

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

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.

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.

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.

Determination of ferroelectric contributions to electromechanical response by frequency dependent piezoresponse force microscopy

PubMed Central

Seol, Daehee; Park, Seongjae; Varenyk, Olexandr V.; Lee, Shinbuhm; Lee, Ho Nyung; Morozovska, Anna N.; Kim, Yunseok

2016-01-01

Hysteresis loop analysis via piezoresponse force microscopy (PFM) is typically performed to probe the existence of ferroelectricity at the nanoscale. However, such an approach is rather complex in accurately determining the pure contribution of ferroelectricity to the PFM. Here, we suggest a facile method to discriminate the ferroelectric effect from the electromechanical (EM) response through the use of frequency dependent ac amplitude sweep with combination of hysteresis loops in PFM. Our combined study through experimental and theoretical approaches verifies that this method can be used as a new tool to differentiate the ferroelectric effect from the other factors that contribute to the EM response. PMID:27466086

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.

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.

Electro-active device using radial electric field piezo-diaphragm for sonic applications

NASA Technical Reports Server (NTRS)

Bryant, Robert G. (Inventor); Fox, Robert L. (Inventor)

2005-01-01

An electro-active transducer for sonic applications includes a ferroelectric material sandwiched by first and second electrode patterns to form a piezo-diaphragm coupled to a mounting frame. When the device is used as a sonic actuator, the first and second electrode patterns are configured to introduce an electric field into the ferroelectric material when voltage is applied to the electrode patterns. When the device is used as a sonic sensor, the first and second electrode patterns are configured to introduce an electric field into the ferroelectric material when the ferroelectric material experiences deflection in a direction substantially perpendicular thereto. In each case, the electrode patterns are designed to cause the electric field to: i) originate at a region of the ferroelectric material between the first and second electrode patterns, and ii) extend radially outward from the region of the ferroelectric material (at which the electric field originates) and substantially parallel to the plane of the ferroelectric material. The mounting frame perimetrically surrounds the peizo-diaphragm and enables attachment of the piezo-diaphragm to a housing.

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.

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

Effect of surface ionic screening on the polarization reversal scenario in ferroelectric thin films: Crossover from ferroionic to antiferroionic states

DOE PAGES

Morozovska, Anna N.; Eliseev, Eugene A.; Kurchak, Anatolii I.; ...

2017-12-08

Nonlinear electrostatic interaction between the surface ions of electrochemical nature and ferroelectric dipoles gives rise to the coupled ferroionic states in nanoscale ferroelectrics. Here, we investigated the role of the surface ions formation energy value on the polarization states and polarization reversal mechanisms, domain structure and corresponding phase diagrams of ferroelectric thin films. Using 3D finite elements modeling we analyze the distribution and hysteresis loops of ferroelectric polarization and ionic charge, and dynamics of the domain states. These calculations performed over large parameter space delineate the regions of single- and poly- domain ferroelectric, ferroionic, antiferroionic and non-ferroelectric states as amore » function of surface ions formation energy, film thickness, applied voltage and temperature. We further map the analytical theory for 1D system onto effective Landau-Ginzburg free energy and establish the correspondence between the 3D numerical and 1D analytical results. In conclusion, this approach allows performing the overview of the ferroionic system phase diagrams and exploring the specifics of switching and domain evolution phenomena.« less

Structure and Dynamics of Domains in Ferroelectric Nanostructures. In-situ TEM Studies

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

Pan, Xiaoqing

2015-06-30

The goal of this project was to explore the structure and dynamic behaviors of ferroelectric domains in ferroelectric thin films and nanostructures by advanced transmission electron microscopy (TEM) techniques in close collaboration with phase field modeling. The experimental techniques used include aberration-corrected sub-Å resolution TEM and in-situ TEM using a novel scanning tunneling microscopy (STM) - TEM holder that allows the direct observation of nucleation and dynamic evolution of ferroelectric domains under applied electric field. Specifically, this project was aimed to (1) to study the roles of static electrical boundary conditions and electrical charge in controlling the equilibrium domain structuresmore » of BiFeO 3 thin films with controlled substrate constraints, (2) to explore the fundamental mechanisms of ferroelectric domain nucleation, growth, and switching under an applied electric field in both uniform thin films and nanostructures, and to understand the roles of crystal defects such as dislocations and interfaces in these processes, (3) to understand the physics of ferroelectric domain walls and the influence of defects on the electrical switching of ferroelectric domains.« less

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.

Effect of surface ionic screening on the polarization reversal scenario in ferroelectric thin films: Crossover from ferroionic to antiferroionic states

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

Morozovska, Anna N.; Eliseev, Eugene A.; Kurchak, Anatolii I.

Nonlinear electrostatic interaction between the surface ions of electrochemical nature and ferroelectric dipoles gives rise to the coupled ferroionic states in nanoscale ferroelectrics. Here, we investigated the role of the surface ions formation energy value on the polarization states and polarization reversal mechanisms, domain structure and corresponding phase diagrams of ferroelectric thin films. Using 3D finite elements modeling we analyze the distribution and hysteresis loops of ferroelectric polarization and ionic charge, and dynamics of the domain states. These calculations performed over large parameter space delineate the regions of single- and poly- domain ferroelectric, ferroionic, antiferroionic and non-ferroelectric states as amore » function of surface ions formation energy, film thickness, applied voltage and temperature. We further map the analytical theory for 1D system onto effective Landau-Ginzburg free energy and establish the correspondence between the 3D numerical and 1D analytical results. In conclusion, this approach allows performing the overview of the ferroionic system phase diagrams and exploring the specifics of switching and domain evolution phenomena.« less

Study of Maxwell–Wagner (M–W) relaxation behavior and hysteresis observed in bismuth titanate layered structure obtained by solution combustion synthesis using dextrose as fuel

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

Subohi, Oroosa, E-mail: oroosa@gmail.com; Shastri, Lokesh; Kumar, G.S.

2014-01-01

Graphical abstract: X-ray diffraction studies show that phase formation and crystallinity was reached only after calcinations at 800 °C. Dielectric constant versus temperature curve shows ferroelectric to paraelectric transition temperature (T{sub c}) to be 650 °C. Complex impedance curves show deviation from Debye behavior. The material shows a thin PE Loop with low remnant polarization due to high conductivity in the as prepared sample. - Highlights: • Bi{sub 4}Ti{sub 3}O{sub 12} is synthesized using solution combustion technique with dextrose as fuel. • Dextrose has high reducing capacity (+24) and generates more no. of moles of gases. • Impedance studies showmore » that the sample follows Maxwell–Wagner relaxation behavior. • Shows lower remnant polarization due to higher c-axis ratio. - Abstract: Structural, dielectric and ferroelectric properties of bismuth titanate (Bi{sub 4}Ti{sub 3}O{sub 12}) obtained by solution combustion technique using dextrose as fuel is studied extensively in this paper. Dextrose is used as fuel as it has high reducing valancy and generates more number of moles of gases during the reaction. X-ray diffraction studies show that phase formation and crystallinity was reached only after calcinations at 800 °C. Dielectric constant versus temperature curve shows ferroelectric to paraelectric transition temperature (T{sub c}) to be 650 °C. The dielectric loss is very less (tan δ < 1) at lower temperatures but increases around T{sub c} due to structural changes in the sample. Complex impedance curves show deviation from Debye behavior. The material shows a thin PE Loop with low remnant polarization due to high conductivity in the as prepared sample.« less

Domain alignment within ferroelectric/dielectric PbTiO 3 /SrTiO 3 superlattice nanostructures

DOE PAGES

Park, Joonkyu; Mangeri, John; Zhang, Qingteng; ...

2018-01-01

The ferroelectric domain pattern within lithographically defined PbTiO 3/SrTiO 3ferroelectric/dielectric heteroepitaxial superlattice nanostructures is strongly influenced by the edges of the structures.

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.

Theoretical Methods of Domain Structures in Ultrathin Ferroelectric Films: A Review

PubMed Central

Liu, Jianyi; Chen, Weijin; Wang, Biao; Zheng, Yue

2014-01-01

This review covers methods and recent developments of the theoretical study of domain structures in ultrathin ferroelectric films. The review begins with an introduction to some basic concepts and theories (e.g., polarization and its modern theory, ferroelectric phase transition, domain formation, and finite size effects, etc.) that are relevant to the study of domain structures in ultrathin ferroelectric films. Basic techniques and recent progress of a variety of important approaches for domain structure simulation, including first-principles calculation, molecular dynamics, Monte Carlo simulation, effective Hamiltonian approach and phase field modeling, as well as multiscale simulation are then elaborated. For each approach, its important features and relative merits over other approaches for modeling domain structures in ultrathin ferroelectric films are discussed. Finally, we review recent theoretical studies on some important issues of domain structures in ultrathin ferroelectric films, with an emphasis on the effects of interfacial electrostatics, boundary conditions and external loads. PMID:28788198

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.

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

Advantages and Challenges of Relaxor-PbTiO3 Ferroelectric Crystals for Electroacoustic Transducers- A Review.

PubMed

Zhang, Shujun; Li, Fei; Jiang, Xiaoning; Kim, Jinwook; Luo, Jun; Geng, Xuecang

2015-03-01

Relaxor-PbTiO 3 (PT) based ferroelectric crystals with the perovskite structure have been investigated over the last few decades due to their ultrahigh piezoelectric coefficients ( d 33 > 1500 pC/N) and electromechanical coupling factors ( k 33 > 90%), far outperforming state-of-the-art ferroelectric polycrystalline Pb(Zr,Ti)O 3 ceramics, and are at the forefront of advanced electroacoustic applications. In this review, the performance merits of relaxor-PT crystals in various electroacoustic devices are presented from a piezoelectric material viewpoint. Opportunities come from not only the ultrahigh properties, specifically coupling and piezoelectric coefficients, but through novel vibration modes and crystallographic/domain engineering. Figure of merits (FOMs) of crystals with various compositions and phases were established for various applications, including medical ultrasonic transducers, underwater transducers, acoustic sensors and tweezers. For each device application, recent developments in relaxor-PT ferroelectric crystals were surveyed and compared with state-of-the-art polycrystalline piezoelectrics, with an emphasis on their strong anisotropic features and crystallographic uniqueness, including engineered domain - property relationships. This review starts with an introduction on electroacoustic transducers and the history of piezoelectric materials. The development of the high performance relaxor-PT single crystals, with a focus on their uniqueness in transducer applications, is then discussed. In the third part, various FOMs of piezoelectric materials for a wide range of ultrasound applications, including diagnostic ultrasound, therapeutic ultrasound, underwater acoustic and passive sensors, tactile sensors and acoustic tweezers, are evaluated to provide a thorough understanding of the materials' behavior under operational conditions. Structure-property-performance relationships are then established. Finally, the impacts and challenges of relaxor-PT crystals are summarized to guide on-going and future research in the development of relaxor-PT crystals for the next generation electroacoustic transducers.

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

Advantages and Challenges of Relaxor-PbTiO3 Ferroelectric Crystals for Electroacoustic Transducers- A Review

PubMed Central

Zhang, Shujun; Li, Fei; Jiang, Xiaoning; Kim, Jinwook; Luo, Jun; Geng, Xuecang

2014-01-01

Relaxor-PbTiO3 (PT) based ferroelectric crystals with the perovskite structure have been investigated over the last few decades due to their ultrahigh piezoelectric coefficients (d33 > 1500 pC/N) and electromechanical coupling factors (k33 > 90%), far outperforming state-of-the-art ferroelectric polycrystalline Pb(Zr,Ti)O3 ceramics, and are at the forefront of advanced electroacoustic applications. In this review, the performance merits of relaxor-PT crystals in various electroacoustic devices are presented from a piezoelectric material viewpoint. Opportunities come from not only the ultrahigh properties, specifically coupling and piezoelectric coefficients, but through novel vibration modes and crystallographic/domain engineering. Figure of merits (FOMs) of crystals with various compositions and phases were established for various applications, including medical ultrasonic transducers, underwater transducers, acoustic sensors and tweezers. For each device application, recent developments in relaxor-PT ferroelectric crystals were surveyed and compared with state-of-the-art polycrystalline piezoelectrics, with an emphasis on their strong anisotropic features and crystallographic uniqueness, including engineered domain - property relationships. This review starts with an introduction on electroacoustic transducers and the history of piezoelectric materials. The development of the high performance relaxor-PT single crystals, with a focus on their uniqueness in transducer applications, is then discussed. In the third part, various FOMs of piezoelectric materials for a wide range of ultrasound applications, including diagnostic ultrasound, therapeutic ultrasound, underwater acoustic and passive sensors, tactile sensors and acoustic tweezers, are evaluated to provide a thorough understanding of the materials’ behavior under operational conditions. Structure-property-performance relationships are then established. Finally, the impacts and challenges of relaxor-PT crystals are summarized to guide on-going and future research in the development of relaxor-PT crystals for the next generation electroacoustic transducers. PMID:25530641

Recognition of exchange striction as the origin of magnetoelectric coupling in multiferroics

NASA Astrophysics Data System (ADS)

Yahia, G.; Damay, F.; Chattopadhyay, S.; Balédent, V.; Peng, W.; Elkaim, E.; Whitaker, M.; Greenblatt, M.; Lepetit, M.-B.; Foury-Leylekian, P.

2017-05-01

The magnetoelectric coupling, a phenomenon inducing magnetic (electric) polarization by application of an external electric (magnetic) field and first conjectured by Curie in 1894, is observed in most of the multiferroics and used for many applications in various fields such as data storage or sensing. However, its microscopic origin is a long-standing controversy in the scientific community. An intense revival of interest developed in the beginning of the 21st century due to the emergence of multiferroic frustrated magnets in which the ferroelectricity is magnetically induced and which present an inherent strong magnetoelectric coupling. The Dzyaloshinskii-Moriya interaction (DMI) well accounts for such ferroelectricity in systems with a noncollinear magnetic order such as the RMnO3 manganites. The DMI effect is, however, inadequate for systems presenting ferroelectricity induced by quasicollinear spin arrangements such as the prominent RMn2O5 manganites. Among different microscopic mechanisms proposed to resolve this incompatibility, the exchange-striction model stands as the most invoked candidate. In this scenario, the polar atomic displacements originate from the release of a frustration caused by the magnetic order. Despite its theoretical description 15 years ago, this mechanism had yet to be unambiguously validated experimentally. The breakthrough finally comes from SmMn2O5 presenting a unique magnetic order revealed by powder neutron diffraction. The unique orientation of its magnetic moment establishes the missing element that definitely validates the exchange striction as the effective mechanism for the spin-induced ferroelectricity in this series. More generally, this is a proof of concept that validates this model on actual systems, facilitating the development of a new generation of multiferroics with unrivaled magnetoelectric properties.

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

Determination of ferroelectric contributions to electromechanical response by frequency dependent piezoresponse force microscopy

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

Seol, Daehee; Park, Seongjae; Varenyk, Olexandr V.

Hysteresis loop analysis via piezoresponse force microscopy (PFM) is typically performed to probe the existence of ferroelectricity at the nanoscale. But, such an approach is rather complex in accurately determining the pure contribution of ferroelectricity to the PFM. We suggest a facile method to discriminate the ferroelectric effect from the electromechanical (EM) response through the use of frequency dependent ac amplitude sweep with combination of hysteresis loops in PFM. This combined study through experimental and theoretical approaches verifies that this method can be used as a new tool to differentiate the ferroelectric effect from the other factors that contribute tomore » the EM response.« less

Out-of-plane three-stable-state ferroelectric switching: Finding the missing middle states

NASA Astrophysics Data System (ADS)

Lee, Jin Hong; Chu, Kanghyun; Kim, Kwang-Eun; Seidel, Jan; Yang, Chan-Ho

2016-03-01

By realizing a nonvolatile third intermediate ferroelectric state through anisotropic misfit strain, we demonstrate electrical switching among three stable out-of-plane polarizations in bismuth ferrite thin films grown on (110) pc-oriented gadolinium scandate substrates (where pc stands for pseudocubic) by the use of an asymmetric external electric field at the step edge of a bottom electrode. We employ phenomenological Landau theory, in conjunction with electrical poling experiments using piezoresponse force microscopy, to understand the role of anisotropic misfit strain and an in-plane electric field in stabilization of multiple ferroelectric states and their competition. Our finding provides a useful insight into multistep ferroelectric switching in rhombohedral ferroelectrics.

Determination of ferroelectric contributions to electromechanical response by frequency dependent piezoresponse force microscopy

DOE PAGES

Seol, Daehee; Park, Seongjae; Varenyk, Olexandr V.; ...

2016-07-28

Hysteresis loop analysis via piezoresponse force microscopy (PFM) is typically performed to probe the existence of ferroelectricity at the nanoscale. But, such an approach is rather complex in accurately determining the pure contribution of ferroelectricity to the PFM. We suggest a facile method to discriminate the ferroelectric effect from the electromechanical (EM) response through the use of frequency dependent ac amplitude sweep with combination of hysteresis loops in PFM. This combined study through experimental and theoretical approaches verifies that this method can be used as a new tool to differentiate the ferroelectric effect from the other factors that contribute tomore » the EM response.« 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.

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

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

NASA Astrophysics Data System (ADS)

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

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

Structure-property relationship of supramolecular ferroelectric [H-66dmbp][Hca] accompanied by high polarization, competing structural phases, and polymorphs.

PubMed

Kobayashi, Kensuke; Horiuchi, Sachio; Ishibashi, Shoji; Kagawa, Fumitaka; Murakami, Youichi; Kumai, Reiji

2014-12-22

Three polymorphic forms of 6,6'-dimethyl-2,2'-bipyridinium chloranilate crystals were characterized to understand the origin of polarization properties and the thermal stability of ferroelectricity. According to the temperature-dependent permittivity, differential scanning calorimetry, and X-ray diffraction, structural phase transitions were found in all polymorphs. Notably, the ferroelectric α-form crystal, which has the longest hydrogen bond (2.95 Å) among the organic acid/base-type supramolecular ferroelectrics, transformed from a polar structure (space group, P21) into an anti-polar structure (space group, P21/c) at 378 K. The non-ferroelectric β- and γ-form crystals also exhibited structural rearrangements around hydrogen bonds. The hydrogen-bonded geometry and ferroelectric properties were compared with other supramolecular ferroelectrics. A positive relationship between the phase-transition temperature (TC ) and hydrogen-bond length () was observed, and was attributed to the potential barrier height for proton off-centering or order/disorder phenomena. The optimized spontaneous polarization (Ps ) agreed well with the results of the first-principles calculations, and could be amplified by separating the two equilibrium positions of protons with increasing . These data consistently demonstrated that stretching is a promising way to enhance the polarization performance and thermal stability of hydrogen-bonded organic ferroelectrics. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Pyroelectric energy conversion with large energy and power density in relaxor ferroelectric thin films

NASA Astrophysics Data System (ADS)

Pandya, Shishir; Wilbur, Joshua; Kim, Jieun; Gao, Ran; Dasgupta, Arvind; Dames, Chris; Martin, Lane W.

2018-05-01

The need for efficient energy utilization is driving research into ways to harvest ubiquitous waste heat. Here, we explore pyroelectric energy conversion from low-grade thermal sources that exploits strong field- and temperature-induced polarization susceptibilities in the relaxor ferroelectric 0.68Pb(Mg1/3Nb2/3)O3-0.32PbTiO3. Electric-field-driven enhancement of the pyroelectric response (as large as -550 μC m-2 K-1) and suppression of the dielectric response (by 72%) yield substantial figures of merit for pyroelectric energy conversion. Field- and temperature-dependent pyroelectric measurements highlight the role of polarization rotation and field-induced polarization in mediating these effects. Solid-state, thin-film devices that convert low-grade heat into electrical energy are demonstrated using pyroelectric Ericsson cycles, and optimized to yield maximum energy density, power density and efficiency of 1.06 J cm-3, 526 W cm-3 and 19% of Carnot, respectively; the highest values reported to date and equivalent to the performance of a thermoelectric with an effective ZT ≈ 1.16 for a temperature change of 10 K. Our findings suggest that pyroelectric devices may be competitive with thermoelectric devices for low-grade thermal harvesting.

Dynamic X-ray diffraction imaging of the ferroelectric response in bismuth ferrite

DOE PAGES

Laanait, Nouamane; Saenrang, Wittawat; Zhou, Hua; ...

2017-03-21

In this study, X-ray diffraction imaging is rapidly emerging as a powerful technique by which one can capture the local structure of crystalline materials at the nano- and meso-scale. Here, we present investigations of the dynamic structure of epitaxial monodomain BiFeO 3 thin-films using a novel full-field Bragg diffraction imaging modality. By taking advantage of the depth penetration of hard X-rays and their exquisite sensitivity to the atomic structure, we imaged in situ and in operando, the electric field-driven structural responses of buried BiFeO 3 epitaxial thin-films in micro-capacitor devices, with sub-100 nm lateral resolution. These imaging investigations were carriedmore » out at acquisition frame rates that reached up to 20 Hz and data transfer rates of 40 MB/s, while accessing diffraction contrast that is sensitive to the entire three-dimensional unit cell configuration. We mined these large datasets for material responses by employing matrix decomposition techniques, such as independent component analysis. We found that this statistical approach allows the extraction of the salient physical properties of the ferroelectric response of the material, such as coercive fields and transient spatiotemporal modulations in their piezoelectric response, and also facilitates their decoupling from extrinsic sources that are instrument specific.« less

Studies of Ion Beam Charge Neutralization by Ferroelectric Plasma Sources

NASA Astrophysics Data System (ADS)

Stepanov, A.; Gilson, E. P.; Grisham, L.; Davidson, R. C.

2013-10-01

Space-charge forces limit the possible transverse compression of high perveance ion beams that are used in ion-beam-driven high energy density physics applications; the minimum radius to which a beam can be focused is an increasing function of perveance. The limit can be overcome if a plasma is introduced in the beam path between the focusing element and the target in order to neutralize the space charge of the beam. This concept has been implemented on the Neutralized Drift Compression eXperiment (NDCX) at LBNL using Ferroelectric Plasma Sources (FEPS). In our experiment at PPPL, we propagate a perveance-dominated ion beam through a FEPS to study the effect of the neutralizing plasma on the beam envelope and its evolution in time. A 30-60 keV space-charge-dominated Argon beam is focused with an Einzel lens into a FEPS located at the beam waist. The beam is intercepted downstream from the FEPS by a movable Faraday cup that provides time-resolved 2D current density profiles of the beam spot on target. We report results on: (a) dependence of charge neutralization on FEPS plasma density; (b) effects on beam emittance, and (c) time evolution of the beam envelope after the FEPS pulse. Research supported by the U.S. Department of Energy.

Pyroelectric energy conversion with large energy and power density in relaxor ferroelectric thin films.

PubMed

Pandya, Shishir; Wilbur, Joshua; Kim, Jieun; Gao, Ran; Dasgupta, Arvind; Dames, Chris; Martin, Lane W

2018-05-01

The need for efficient energy utilization is driving research into ways to harvest ubiquitous waste heat. Here, we explore pyroelectric energy conversion from low-grade thermal sources that exploits strong field- and temperature-induced polarization susceptibilities in the relaxor ferroelectric 0.68Pb(Mg 1/3 Nb 2/3 )O 3 -0.32PbTiO 3 . Electric-field-driven enhancement of the pyroelectric response (as large as -550 μC m -2  K -1 ) and suppression of the dielectric response (by 72%) yield substantial figures of merit for pyroelectric energy conversion. Field- and temperature-dependent pyroelectric measurements highlight the role of polarization rotation and field-induced polarization in mediating these effects. Solid-state, thin-film devices that convert low-grade heat into electrical energy are demonstrated using pyroelectric Ericsson cycles, and optimized to yield maximum energy density, power density and efficiency of 1.06 J cm -3 , 526 W cm -3 and 19% of Carnot, respectively; the highest values reported to date and equivalent to the performance of a thermoelectric with an effective ZT ≈ 1.16 for a temperature change of 10 K. Our findings suggest that pyroelectric devices may be competitive with thermoelectric devices for low-grade thermal harvesting.

Polarization Control via He-Ion Beam Induced Nanofabrication in Layered Ferroelectric Semiconductors

DOE PAGES

Belianinov, Alex; Iberi, Vighter; Tselev, Alexander; ...

2016-02-23

Rapid advanced in nanoscience rely on continuous improvements of matter manipulation at near atomic scales. Currently, well characterized, robust, resist-based lithography carries the brunt of the nanofabrication process. However, use of local electron, ion and physical probe methods is also expanding, driven largely by their ability to fabricate without the multi-step preparation processes that can result in contamination from resists and solvents. Furthermore, probe based methods extend beyond nanofabrication to nanomanipulation and imaging, vital ingredients to rapid transition to prototyping and testing of layered 2D heterostructured devices. In this work we demonstrate that helium ion interaction, in a Helium Ionmore » Microscope (HIM), with the surface of bulk copper indium thiophosphate CuM IIIP 2X 6 (M = Cr, In; X= S, Se), (CITP) results in the control of ferroelectric domains, and growth of cylindrical nanostructures with enhanced conductivity; with material volumes scaling with the dosage of the beam. The nanostructures are oxygen rich, sulfur poor, and with the copper concentration virtually unchanged as confirmed by Energy Dispersive X-ray (EDX). Scanning Electron Microscopy (SEM) imaging contrast as well as Scanning Microwave Microscopy (SMM) measurements suggest enhanced conductivity in the formed particle, whereas Atomic Force Microscopy (AFM) measurements indicate that the produced structures have lower dissipation and a lower Young s modulus.« less

Enhanced fatigue and retention in ferroelectric thin film memory capacitors by post-top electrode anneal treatment

NASA Technical Reports Server (NTRS)

Thakoor, Sarita (Inventor)

1992-01-01

Thin film ferroelectric capacitors comprising a ferroelectric film sandwiched between electrodes for nonvolatile memory operations are rendered more stable by subjecting the capacitors to an anneal following deposition of the top electrode. The anneal is done so as to form the interface between the ferroelectric film and the top electrode. Heating in an air oven, laser annealing, or electron bombardment may be used to form the interface. Heating in an air oven is done at a temperature at least equal to the crystallization temperature of the ferroelectric film. Where the ferroelectric film comprises lead zirconate titanate, annealing is done at about 550 to 600 C for about 10 to 15 minutes. The formation treatment reduces the magnitude of charge associated with the nonswitching pulse in the thin film ferroelectric capacitors. Reduction of this charge leads to significantly more stable nonvolatile memory operations in both digital and analog memory devices. The formation treatment also reduces the ratio of change of the charge associated with the nonswitching pulse as a function of retention time. These improved memory devices exhibit greater performance in retention and reduced fatigue in memory arrays.

Enhanced fatigue and retention in ferroelectric thin film memory capacitors by post-top electrode anneal treatment

NASA Technical Reports Server (NTRS)

Thakoor, Sarita (Inventor)

1994-01-01

Thin film ferroelectric capacitors (10) comprising a ferroelectric film (18) sandwiched between electrodes (16 and 20) for nonvolatile memory operations are rendered more stable by subjecting the capacitors to an anneal following deposition of the top electrode (20). The anneal is done so as to form the interface (22) between the ferroelectric film and the top electrode. Heating in an air oven, laser annealing, or electron bombardment may be used to form the interface. Heating in an air oven is done at a temperature at least equal to the crystallization temperature of the ferroelectric film. Where the ferroelectric film comprises lead zirconate titanate, annealing is done at about 550.degree. to 600.degree. C. for about 10 to 15 minutes. The formation treatment reduces the magnitude of charge associated with the non-switching pulse in the thin film ferroelectric capacitors. Reduction of this charge leads to significantly more stable nonvolatile memory operations in both digital and analog memory devices. The formation treatment also reduces the ratio of change of the charge associated with the non-switching pulse as a function of retention time. These improved memory devices exhibit greater performance in retention and reduced fatigue in memory arrays.

Synthetic magnetoelectric coupling in a nanocomposite multiferroic

DOE PAGES

Jain, P.; Wang, Q.; Roldan, M.; ...

2015-03-13

Given the paucity of single phase multiferroic materials (with large ferromagnetic moment), composite systems seem an attractive solution to realize magnetoelectric coupling between ferromagnetic and ferroelectric order parameters. Despite having antiferromagnetic order, BiFeO₃ (BFO) has nevertheless been a key material due to excellent ferroelectric properties at room temperature. We studied a superlattice composed of 8 repetitions of 6 unit cells of La₀.₇Sr₀.₃MnO₃ (LSMO) grown on 5 unit cells of BFO. Significant net uncompensated magnetization in BFO, an insulating superlattice, is demonstrated using polarized neutron reflectometry. Remarkably, the magnetization enables magnetic field to change the dielectric properties of the superlattice, whichmore » we cite as an example of synthetic magnetoelectric coupling. Importantly, controlled creation of magnetic moment in BFO is a much needed path toward design and implementation of integrated oxide devices for next generation magnetoelectric data storage platforms.« less

Strain-assisted magnetization reversal in Co/Ni multilayers with perpendicular magnetic anisotropy

PubMed Central

Gopman, D. B.; Dennis, C. L.; Chen, P. J.; Iunin, Y. L.; Finkel, P.; Staruch, M.; Shull, R. D.

2016-01-01

Multifunctional materials composed of ultrathin magnetic films with perpendicular magnetic anisotropy combined with ferroelectric substrates represent a new approach toward low power, fast, high density spintronics. Here we demonstrate Co/Ni multilayered films with tunable saturation magnetization and perpendicular anisotropy grown directly on ferroelectric PZT [Pb(Zr0.52Ti0.48)O3] substrate plates. Electric fields up to ±2 MV/m expand the PZT by 0.1% and generate at least 0.02% in-plane compression in the Co/Ni multilayered film. Modifying the strain with a voltage can reduce the coercive field by over 30%. We also demonstrate that alternating in-plane tensile and compressive strains (less than 0.01%) can be used to propagate magnetic domain walls. This ability to manipulate high anisotropy magnetic thin films could prove useful for lowering the switching energy for magnetic elements in future voltage-controlled spintronic devices. PMID:27297638

Multi-floor cascading ferroelectric nanostructures: multiple data writing-based multi-level non-volatile memory devices.

PubMed

Hyun, Seung; Kwon, Owoong; Lee, Bom-Yi; Seol, Daehee; Park, Beomjin; Lee, Jae Yong; Lee, Ju Hyun; Kim, Yunseok; Kim, Jin Kon

2016-01-21

Multiple data writing-based multi-level non-volatile memory has gained strong attention for next-generation memory devices to quickly accommodate an extremely large number of data bits because it is capable of storing multiple data bits in a single memory cell at once. However, all previously reported devices have failed to store a large number of data bits due to the macroscale cell size and have not allowed fast access to the stored data due to slow single data writing. Here, we introduce a novel three-dimensional multi-floor cascading polymeric ferroelectric nanostructure, successfully operating as an individual cell. In one cell, each floor has its own piezoresponse and the piezoresponse of one floor can be modulated by the bias voltage applied to the other floor, which means simultaneously written data bits in both floors can be identified. This could achieve multi-level memory through a multiple data writing process.

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.

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.

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.

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

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.

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.

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

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.

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.

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.

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.

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.

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

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.

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

Lomenzo, Patrick D.; Nishida, Toshikazu, E-mail: nishida@ufl.edu; Takmeel, Qanit

Ferroelectric HfO{sub 2}-based thin films, which can exhibit ferroelectric properties down to sub-10 nm thicknesses, are a promising candidate for emerging high density memory technologies. As the ferroelectric thickness continues to shrink, the electrode-ferroelectric interface properties play an increasingly important role. We investigate the TaN interface properties on 10 nm thick Si-doped HfO{sub 2} thin films fabricated in a TaN metal-ferroelectric-metal stack which exhibit highly asymmetric ferroelectric characteristics. To understand the asymmetric behavior of the ferroelectric characteristics of the Si-doped HfO{sub 2} thin films, the chemical interface properties of sputtered TaN bottom and top electrodes are probed with x-ray photoelectron spectroscopy. Ta-Omore » bonds at the bottom electrode interface and a significant presence of Hf-N bonds at both electrode interfaces are identified. It is shown that the chemical heterogeneity of the bottom and top electrode interfaces gives rise to an internal electric field, which causes the as-grown ferroelectric domains to preferentially polarize to screen positively charged oxygen vacancies aggregated at the oxidized bottom electrode interface. Electric field cycling is shown to reduce the internal electric field with a concomitant increase in remanent polarization and decrease in relative permittivity. Through an analysis of pulsed transient switching currents, back-switching is observed in Si-doped HfO{sub 2} thin films with pinched hysteresis loops and is shown to be influenced by the internal electric field.« less

Performance Enhancement of Tunable Bandpass Filters Using Selective Etched Ferroelectric Thin Films

NASA Technical Reports Server (NTRS)

Miranda, Felix A.; Mueller, Carl H.; VanKeuls, Fred W.; Subramanyam, Guru; Vignesparamoorthy, Sivaruban

2003-01-01

The inclusion of voltage-tunable barium strontium titanate (BSTO) thin films into planar band pass filters offers tremendous potential to increase their versatility. The ability to tune the passband so as to correct for minor deviations in manufacturing tolerances, or to completely reconfigure the operating frequencies of a microwave communication system, are highly sought-after goals. However, use of ferroelectric films in these devices results in higher dielectric losses, which in turn increase the insertion loss and decrease the quality factors of the filters. This study explores the use of patterned ferroelectric layers to minimize dielectric losses without degrading tunability. Patterning the ferroelectric layers enables us to constrict the width of the ferroelectric layers between the coupled microstrip lines, and minimize losses due to ferroelectric layers. Coupled one-pole microstrip bandpass filters with fundamental resonances at approx. 7.2 GHz and well defined harmonic resonances at approx. 14.4 and approx. 21.6 GHz, were designed, simulated and tested. For one of the filters, experimental results verified that its center frequency was tunable by 528 MHz at a center frequency of 21.957 GHz, with insertion losses varying from 4.3 to 2.5 dB, at 0 and 3.5 V/micron, respectively. These data demonstrate that the tuning-to-loss figure of merit of tunable microstrip filters can be greatly improved using patterned ferroelectric thin films as the tuning element, and tuning can be controlled by engineering the ferroelectric constriction in the coupled sections.

Electrical transport through Pb(Zr,Ti)O3 p-n and p-p heterostructures modulated by bound charges at a ferroelectric surface: Ferroelectric p-n diode

NASA Astrophysics Data System (ADS)

Watanabe, Yukio

1999-05-01

Current through (Pb,La)(Zr,Ti)O3 ferroelectrics on perovskite semiconductors is found to exhibit diode characteristics of which polarity is universally determined by the carrier conduction-type semiconductors. A persisting highly reproducible resistance modulation by a dc voltage, which has a short retention, is observed and is ascribed to a band bending of the ferroelectric by the formation of charged traps. This interpretation is consistent with a large relaxation current observed at a low voltage. On the other hand, a reproducible resistance modulation by a pulse voltage, which has a long retention, is observed in metal/(Pb,La)(Zr,Ti)O3/SrTiO3:Nb but not in metal/(Pb,La)(Zr,Ti)O3/(La,Sr)2CuO4 and is attributed to a possible band bending due to the spontaneous polarization (P) switching. The observed current voltage (IV) characteristics, the polarity dependence, the relaxation, and the modulation are explicable, if we assume a p-n or a p-p junction at the ferroelectric semiconductor interface (p: hole conduction type, n: electron conduction type). The analysis suggests that an intrinsically inhomogeneous P (∇P) near the ferroelectric/metal interface is likely very weak or existing in a very thin layer, when a reaction of the metal with the ferroelectric is eliminated. Additionally, the various aspects of transport through ferroelectrics are explained as a transport in the carrier depleted region.

Periodically poled potassium niobate for second-harmonic generation at 463 nm.

PubMed

Meyn, J P; Klein, M E; Woll, D; Wallenstein, R; Rytz, D

1999-08-15

We report on the fabrication and characterization of quasi-phase-matched potassium niobate crystals for second-harmonic generation. Periodic 30-mum -pitch antiparallel ferroelectric domains are fabricated by means of poling in an electrical field. Both birefrigence and periodic phase shift of the generated second harmonic contribute to phase matching when the d(31) nonlinear optical tensor element is used. 3.8 mW of second-harmonic radiation at 463 nm is generated by frequency doubling of the output of master-oscillator power-amplifier diode laser in a 5-mm-long crystal. The measured effective nonlinear coefficient is 3.7pm/V. The measured spectral acceptance bandwidth of 0.25 nm corresponds to the theoretical value.

Strain-controlled skyrmion creation and propagation in ferroelectric/ferromagnetic hybrid wires

NASA Astrophysics Data System (ADS)

Li, Zhi; Zhang, Youguang; Huang, Yangqi; Wang, Chengxiang; Zhang, Xichao; Liu, Yan; Zhou, Yan; Kang, Wang; Koli, Shradha Chandrashekhar; Lei, Na

2018-06-01

The control of magnetic skyrmion creation and pinning through strain is studied by micromagnetic simulations. A single stable skyrmion can be created by a vertical strain pulse on Pd/Fe/Ir hybrid structure on Pb(Zr1-xTix)O3 nanowire with -1.8 V pulse voltage from 1.2 ns to 2.0 ns. Then the skyrmion is pinned by the vertical strain independent of the polarity during its propagation in the wire driven by the current. The proposed device integrates strain-controlled skyrmion creation and pinning in a single nanowire structure, which would open a new route for skyrmion-based memory and logic devices with ultra-low power consumption.

First-principles calculation of the bulk photovoltaic effect in bismuth ferrite.

PubMed

Young, Steve M; Zheng, Fan; Rappe, Andrew M

2012-12-07

We compute the bulk photovoltaic effect (BPVE) in BiFeO(3) using first-principles shift current theory, finding good agreement with experimental results. Furthermore, we reconcile apparently contradictory observations: by examining the contributions of all photovoltaic response tensor components and accounting for the geometry and ferroelectric domain structure of the experimental system, we explain the apparent lack of BPVE response in striped polydomain samples that is at odds with the significant response observed in monodomain samples. We reveal that the domain-wall-driven response in striped polydomain samples is partially mitigated by the BPVE, suggesting that enhanced efficiency could be obtained in materials with cooperative rather than antagonistic interaction between the two mechanisms.

Electrical conduction at domain walls in multiferroic BiFeO3

NASA Astrophysics Data System (ADS)

Seidel, Jan; Martin, Lane; He, Qing; Zhan, Qian; Chu, Ying-Hao; Rother, Axel; Hawkridge, Michael; Maksymovych, Peter; Yu, Pu; Gajek, Martin; Balke, Nina; Kalinin, Sergei; Gemming, Sybille; Wang, Feng; Catalán, Gustau; Scott, James; Spaldin, Nicola; Orenstein, Joseph; Ramesh, Ramamoorthy

2009-03-01

We report the observation of room temperature electronic conductivity at ferroelectric domain walls in BiFeO3. The origin and nature of the observed conductivity is probed using a combination of conductive atomic force microscopy, high resolution transmission electron microscopy and first-principles density functional computations. We show that a structurally driven change in both the electrostatic potential and local electronic structure (i.e., a decrease in band gap) at the domain wall leads to the observed electrical conductivity. We estimate the conductivity in the wall to be several orders of magnitude higher than for the bulk material. Additionally we demonstrate the potential for device applications of such conducting nanoscale features.

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.

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

Gelinck, G. H., E-mail: Gerwin.Gelinck@tno.nl; Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven; Breemen, A. J. J. M. van

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.

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.

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.

Structurally frustrated relaxor ferroelectric behavior in CaCu{sub 3}Ti{sub 4}O{sub 12}

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

Liu Yun; Withers, Ray L.; Wei Xiaoyong

2005-10-01

Direct diffraction evidence for structurally frustrated relaxor ferroelectric behavior in the form of one-dimensionally correlated, off-center displacements of Ti ions within the TiO{sub 6} octahedra of CaCu{sub 3}Ti{sub 4}O{sub 12} (CCTO) has been obtained. When coupled with the observation of a ferroelectric effect, important implications for the understanding of the extraordinary dielectric properties of CCTO arise. That the incipient ferroelectric behavior is correlated only along one-dimensional <001> columns of TiO{sub 6} octahedra in the absence of an applied electric field offers a crucial insight into the underlying nature of CCTO and suggests the existence of a unique class of structurallymore » frustrated, ferroelectric relaxors.« less

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.

Hysteresis Analysis Based on the Ferroelectric Effect in Hybrid Perovskite Solar Cells.

PubMed

Wei, Jing; Zhao, Yicheng; Li, Heng; Li, Guobao; Pan, Jinlong; Xu, Dongsheng; Zhao, Qing; Yu, Dapeng

2014-11-06

The power conversion efficiency (PCE) of CH3NH3PbX3 (X = I, Br, Cl) perovskite solar cells has been developed rapidly from 6.5 to 18% within 3 years. However, the anomalous hysteresis found in I-V measurements can cause an inaccurate estimation of the efficiency. We attribute the phenomena to the ferroelectric effect and build a model based on the ferroelectric diode to explain it. The ferroelectric effect of CH3NH3PbI3-xClx is strongly suggested by characterization methods and the E-P (electrical field-polarization) loop. The hysteresis in I-V curves is found to greatly depend on the scan range as well as the velocity, which is well explained by the ferroelectric diode model. We also find that the current signals show exponential decay in ∼10 s under prolonged stepwise measurements, and the anomalous hysteresis disappears using these stabilized current values. The experimental results accord well with the model based on ferroelectric properties and prove that prolonged stepwise measurement is an effective way to evaluate the real efficiency of perovskite solar cells. Most importantly, this work provides a meaningful perspective that the ferroelectric effect (if it really exists) should be paid special attention in the optimization of perovskite solar cells.

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.

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.

Losses in Ferroelectric Materials

PubMed Central

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

2015-01-01

Ferroelectric materials are the best dielectric and piezoelectric materials known today. Since the discovery of barium titanate in the 1940s, lead zirconate titanate ceramics in the 1950s and relaxor-PT single crystals (such as lead magnesium niobate-lead titanate and lead zinc niobate-lead titanate) in the 1980s and 1990s, perovskite ferroelectric materials have been the dominating piezoelectric materials for electromechanical devices, and are widely used in sensors, actuators and ultrasonic transducers. Energy losses (or energy dissipation) in ferroelectrics are one of the most critical issues for high power devices, such as therapeutic ultrasonic transducers, large displacement actuators, SONAR projectors, and high frequency medical imaging transducers. The losses of ferroelectric materials have three distinct types, i.e., elastic, piezoelectric and dielectric losses. People have been investigating the mechanisms of these losses and are trying hard to control and minimize them so as to reduce performance degradation in electromechanical devices. There are impressive progresses made in the past several decades on this topic, but some confusions still exist. Therefore, a systematic review to define related concepts and clear up confusions is urgently in need. With this objective in mind, we provide here a comprehensive review on the energy losses in ferroelectrics, including related mechanisms, characterization techniques and collections of published data on many ferroelectric materials to provide a useful resource for interested scientists and engineers to design electromechanical devices and to gain a global perspective on the complex physical phenomena involved. More importantly, based on the analysis of available information, we proposed a general theoretical model to describe the inherent relationships among elastic, dielectric, piezoelectric and mechanical losses. For multi-domain ferroelectric single crystals and ceramics, intrinsic and extrinsic energy loss mechanisms are discussed in terms of compositions, crystal structures, temperature, domain configurations, domain sizes and grain boundaries. The intrinsic and extrinsic contributions to the total energy dissipation are quantified. In domain engineered ferroelectric single crystals and ceramics, polarization rotations, domain wall motions and mechanical wave scatterings at grain boundaries are believed to control the mechanical quality factors of piezoelectric resonators. We show that a thorough understanding on the kinetic processes is critical in analyzing energy loss behavior and other time-dependent properties in ferroelectric materials. At the end of the review, existing challenges in the study and control of losses in ferroelectric materials are analyzed, and future perspective in resolving these issues is discussed. PMID:25814784

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 rejection, and constant bandwidth is designed, simulated, fabricated and measured. The filters are fabricated using barium strontium titanate (BST) varactors. Electromagnetic simulations and measured results of the tunable two-pole ferroelectric filter are analyzed to explore the origins of high insertion loss in ferroelectric filters. The results indicate that the high-permittivity of the BST (a ferroelectric) not only makes the filters tunable and compact, but also increases the conductive loss of the ferroelectric-based tunable resonators which translates into high insertion loss in ferroelectric filters.

Losses in Ferroelectric Materials.

PubMed

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

2015-03-01

Ferroelectric materials are the best dielectric and piezoelectric materials known today. Since the discovery of barium titanate in the 1940s, lead zirconate titanate ceramics in the 1950s and relaxor-PT single crystals (such as lead magnesium niobate-lead titanate and lead zinc niobate-lead titanate) in the 1980s and 1990s, perovskite ferroelectric materials have been the dominating piezoelectric materials for electromechanical devices, and are widely used in sensors, actuators and ultrasonic transducers. Energy losses (or energy dissipation) in ferroelectrics are one of the most critical issues for high power devices, such as therapeutic ultrasonic transducers, large displacement actuators, SONAR projectors, and high frequency medical imaging transducers. The losses of ferroelectric materials have three distinct types, i.e., elastic, piezoelectric and dielectric losses. People have been investigating the mechanisms of these losses and are trying hard to control and minimize them so as to reduce performance degradation in electromechanical devices. There are impressive progresses made in the past several decades on this topic, but some confusions still exist. Therefore, a systematic review to define related concepts and clear up confusions is urgently in need. With this objective in mind, we provide here a comprehensive review on the energy losses in ferroelectrics, including related mechanisms, characterization techniques and collections of published data on many ferroelectric materials to provide a useful resource for interested scientists and engineers to design electromechanical devices and to gain a global perspective on the complex physical phenomena involved. More importantly, based on the analysis of available information, we proposed a general theoretical model to describe the inherent relationships among elastic, dielectric, piezoelectric and mechanical losses. For multi-domain ferroelectric single crystals and ceramics, intrinsic and extrinsic energy loss mechanisms are discussed in terms of compositions, crystal structures, temperature, domain configurations, domain sizes and grain boundaries. The intrinsic and extrinsic contributions to the total energy dissipation are quantified. In domain engineered ferroelectric single crystals and ceramics, polarization rotations, domain wall motions and mechanical wave scatterings at grain boundaries are believed to control the mechanical quality factors of piezoelectric resonators. We show that a thorough understanding on the kinetic processes is critical in analyzing energy loss behavior and other time-dependent properties in ferroelectric materials. At the end of the review, existing challenges in the study and control of losses in ferroelectric materials are analyzed, and future perspective in resolving these issues is discussed.

First-principles approach to the dynamic magnetoelectric couplings for the non-reciprocal directional dichroism in BiFeO 3

DOE PAGES

Kezsmarki, I.; Fishman, Randy Scott

2016-04-18

Due to the complicated magnetic and crystallographic structures of BiFeO 3, its magnetoelectric (ME) couplings and microscopic model Hamiltonian remain poorly understood. By employing a firstprinciples approach, we uncover all possibleMEcouplings associated with the spin-current (SC) and exchange-striction (ES) polarizations, and construct an appropriate Hamiltonian for the long-range spin-cycloid in BiFeO 3. First-principles calculations are used to understand the microscopic origins of theMEcouplings.Wefind that inversion symmetries broken by ferroelectric and antiferroelectric distortions induce the SC and the ES polarizations, which cooperatively produce the dynamicME effects in BiFeO 3. A model motivated by first principles reproduces the absorption difference of counter-propagatingmore » light beams called non-reciprocal directional dichroism. The current paper focuses on the spin-driven (SD) polarizations produced by a dynamic electric field, i.e. the dynamic MEcouplings. Due to the inertial properties of Fe, the dynamic SD polarizations differ significantly from the static SD polarizations. Our systematic approach can be generally applied to any multiferroic material, laying the foundation for revealing hiddenMEcouplings on the atomic scale and for exploiting opticalMEeffects in the next generation of technological devices such as optical diodes.« less

Structural, optical and vibrational properties of self-assembled Pbn+1(Ti1−xFex)nO3n+1−δ Ruddlesden-Popper superstructures

PubMed Central

Doig, K. I.; Peters, J. J. P.; Nawaz, S.; Walker, D.; Walker, M.; Lees, M. R.; Beanland, R.; Sanchez, A. M.; McConville, C. F.; Palkar, V. R.; Lloyd-Hughes, J.

2015-01-01

Bulk crystals and thin films of PbTi1−xFexO3−δ (PTFO) are multiferroic, exhibiting ferroelectricity and ferromagnetism at room temperature. Here we report that the Ruddlesden-Popper phase Pbn+1(Ti1−xFex)nO3n+1−δ forms spontaneously during pulsed laser deposition of PTFO on LaAlO3 substrates. High-resolution transmission electron microscopy, x-ray diffraction and x-ray photoemission spectroscopy were utilised to perform a structural and compositional analysis, demonstrating that and . The complex dielectric function of the films was determined from far-infrared to ultraviolet energies using a combination of terahertz time-domain spectroscopy, Fourier transform spectroscopy, and spectroscopic ellipsometry. The simultaneous Raman and infrared activity of phonon modes and the observation of second harmonic generation establishes a non-centrosymmetric point group for Pbn+1(Ti0.5Fe0.5)nO3n+1−δ, a prerequisite for (but not proof of) ferroelectricity. No evidence of macroscopic ferromagnetism was found in SQUID magnetometry. The ultrafast optical response exhibited coherent magnon oscillations compatible with local magnetic order, and additionally was used to study photocarrier cooling on picosecond timescales. An optical gap smaller than that of BiFeO3 and long photocarrier lifetimes may make this system interesting as a ferroelectric photovoltaic. PMID:25591924

Phenomenological description of depoling current in Pb0.99Nb0.02(Zr0.95Ti0.05)0.98O3 ferroelectric ceramics under shock wave compression: Relaxation model

NASA Astrophysics Data System (ADS)

Jiang, Dongdong; Du, Jinmei; Gu, Yan; Feng, Yujun

2012-05-01

By assuming a relaxation process for depolarization associated with the ferroelectric (FE) to antiferroelectric (AFE) phase transition in Pb0.99Nb0.02(Zr0.95Ti0.05)0.98O3 ferroelectric ceramics under shock wave compression, we build a new model for the depoling current, which is different from both the traditional constant current source (CCS) model and the phase transition kinetics (PTK) model. The characteristic relaxation time and new-equilibrated polarization are dependent on both the shock pressure and electric field. After incorporating a Maxwell s equation, the relaxation model developed applies to all the depoling currents under short-circuit condition and high-impedance condition. Influences of shock pressure, load resistance, dielectric property, and electrical conductivity on the depoling current are also discussed. The relaxation model gives a good description about the suppressing effect of the self-generated electric field on the FE-to-AFE phase transition at low shock pressures, which cannot be described by the traditional models. After incorporating a time- and electric-field-dependent repolarization, this model predicts that the high-impedance current eventually becomes higher than the short-circuit current, which is consistent with the experimental results in the literature. Finally, we make the comparison between our relaxation model and the traditional CCS model and PTK model.

Radiation Response of Emerging FeRAM Technology

NASA Technical Reports Server (NTRS)

Nguyen, D. N.; Scheick, L. Z.

2001-01-01

The test results of measurements performed on two different sizes of ferroelectric random access memory (FeRAM) suggest the degradation is due to the low radiation tolerance of sense amplifiers and reference voltage generators which are based on commercial complementary metal oxide semiconductor (CMOS) technology. This paper presents total ionizing dose (TID) testing of 64Kb Ramtron FM1608 and 256Kb Ramtron FM1808.

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.

Effect of geometric configuration on the electrocaloric properties of nanoscale ferroelectric materials

NASA Astrophysics Data System (ADS)

Hou, Xu; Li, Huiyu; Shimada, Takahiro; Kitamura, Takayuki; Wang, Jie

2018-03-01

The electrocaloric properties of ferroelectrics are highly dependent on the domain structure in the materials. For nanoscale ferroelectric materials, the domain structure is greatly influenced by the geometric configuration of the system. Using a real-space phase field model based on the Ginzburg-Landau theory, we investigate the effect of geometric configurations on the electrocaloric properties of nanoscale ferroelectric materials. The ferroelectric hysteresis loops under different temperatures are simulated for the ferroelectric nano-metamaterials with square, honeycomb, and triangular Archimedean geometric configurations. The adiabatic temperature changes (ATCs) for three ferroelectric nano-metamaterials under different electric fields are calculated from the Maxwell relationship based on the hysteresis loops. It is found that the honeycomb specimen exhibits the largest ATC of Δ T = 4.3 °C under a field of 391.8 kV/cm among three geometric configurations, whereas the square specimen has the smallest ATC of Δ T = 2.7 °C under the same electric field. The different electrocaloric properties for three geometric configurations stem from the different domain structures. There are more free surfaces perpendicular to the electric field in the square specimen than the other two specimens, which restrict more polarizations perpendicular to the electric field, resulting in a small ATC. Due to the absence of free surfaces perpendicular to the electric field in the honeycomb specimen, the change of polarization with temperature in the direction of the electric field is more easy and thus leads to a large ATC. The present work suggests a novel approach to obtain the tunable electrocaloric properties in nanoscale ferroelectric materials by designing their geometric configurations.

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

Domain topology and domain switching kinetics in a hybrid improper ferroelectric

PubMed Central

Huang, F. -T.; Xue, F.; Gao, B.; Wang, L. H.; Luo, X.; Cai, W.; Lu, X. -Z.; Rondinelli, J. M.; Chen, L. Q.; Cheong, S. -W.

2016-01-01

Charged polar interfaces such as charged ferroelectric walls or heterostructured interfaces of ZnO/(Zn,Mg)O and LaAlO3/SrTiO3, across which the normal component of electric polarization changes suddenly, can host large two-dimensional conduction. Charged ferroelectric walls, which are energetically unfavourable in general, were found to be mysteriously abundant in hybrid improper ferroelectric (Ca,Sr)3Ti2O7 crystals. From the exploration of antiphase boundaries in bilayer-perovskites, here we discover that each of four polarization-direction states is degenerate with two antiphase domains, and these eight structural variants form a Z4 × Z2 domain structure with Z3 vortices and five distinct types of domain walls, whose topology is directly relevant to the presence of abundant charged walls. We also discover a zipper-like nature of antiphase boundaries, which are the reversible creation/annihilation centres of pairs of two types of ferroelectric walls (and also Z3-vortex pairs) in 90° and 180° polarization switching. Our results demonstrate the unexpectedly rich nature of hybrid improper ferroelectricity. PMID:27215944

Enhanced energy harvesting in commercial ferroelectric materials

NASA Astrophysics Data System (ADS)

Patel, Satyanarayan; Chauhan, Aditya; Vaish, Rahul

2014-04-01

Ferroelectric materials are used in a number of applications ranging from simple sensors and actuators to ferroelectric random access memories (FRAMs), transducers, health monitoring system and microelectronics. The multiphysical coupling ability possessed by these materials has been established to be useful for energy harvesting applications. However, conventional energy harvesting techniques employing ferroelectric materials possess low energy density. This has prevented the successful commercialization of ferroelectric based energy harvesting systems. In this context, the present study aims at proposing a novel approach for enhanced energy harvesting using commercially available ferroelectric materials. This technique was simulated to be used for two commercially available piezoelectric materials namely PKI-552 and APCI-840, soft and hard lead-zirconate-titanate (PZT) pervoskite ceramics, respectively. It was observed that a maximum energy density of 348 kJm-3cycle-1 can be obtained for cycle parameters of (0-1 ton compressive stress and 1-25 kV.cm-1 electric field) using APCI-840. The reported energy density is several hundred times larger than the maximum energy density reported in the literature for vibration harvesting systems.

Effect of surface ionic screening on the polarization reversal scenario in ferroelectric thin films: Crossover from ferroionic to antiferroionic states

NASA Astrophysics Data System (ADS)

Morozovska, Anna N.; Eliseev, Eugene A.; Kurchak, Anatolii I.; Morozovsky, Nicholas V.; Vasudevan, Rama K.; Strikha, Maksym V.; Kalinin, Sergei V.

2017-12-01

Nonlinear electrostatic interaction between the surface ions of electrochemical nature and ferroelectric dipoles gives rise to the coupled ferroionic states in nanoscale ferroelectrics. Here, we investigate the role of the surface ion formation energy on the polarization states and its reversal mechanisms, domain structure, and corresponding phase diagrams of ferroelectric thin films. Using 3D finite element modeling, we analyze the distribution and hysteresis loops of ferroelectric polarization and ionic charge, and the dynamics of the domain states. These calculations performed over large parameter space delineate the regions of single- and polydomain ferroelectric, ferroionic, antiferroionic, and nonferroelectric states as a function of surface ion formation energy, film thickness, applied voltage, and temperature. We further map the analytical theory for 1D systems onto an effective Landau-Ginzburg free energy and establish the correspondence between the 3D numerical and 1D analytical results. This approach allows us to perform an overview of the ferroionic system phase diagrams and explore the specifics of polarization reversal and domain evolution phenomena.

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.

A -Site Ordered Double Perovskite CaMnTi 2 O 6 as a Multifunctional Piezoelectric and Ferroelectric–Photovoltaic Material

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

Gou, Gaoyang; Charles, Nenian; Shi, Jing

2017-09-11

The double perovskite CaMnTi2O6, is a rare A site ordered perovskite oxide that exhibits a sizable ferroelectric polarization and relatively high Curie temperature. Using first-principles calculations combined with detailed symmetry analyses, we identify the origin of the ferroelectricity in CaMnTi2O6. We further explore the material properties of CaMnTi2O6, including its ferroelectric polarization, dielectric and piezoelectric responses, magnetic order, electronic structure, and optical absorption coefficient. It is found that CaMnTi2O6 exhibits room-temperature-stable ferroelectricity and moderate piezoelectric responses. Moreover, CaMnTi2O6 is predicted to have a semiconducting energy band gap similar to that of BiFeO3, and its band gap can further be tuned-viamore » distortions of the planar Mn-O bond lengths. CaMnTi2O6 exemplifies a new class of single-phase semiconducting ferroelectric perovskites for potential applications in ferroelectric photovoltaic solar cells.« less

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.

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.

Electro-Active Device Using Radial Electric Field Piezo-Diaphragm for Control of Fluid Movement

NASA Technical Reports Server (NTRS)

Bryant, Robert G. (Inventor); Working, Dennis C. (Inventor)

2005-01-01

A fluid-control electro-active device includes a piezo-diaphragm made from a ferroelectric material sandwiched by first and second electrode patterns configured to introduce an electric field into the ferroelectric material when voltage is applied thereto. The electric field originates at a region of the ferroelectric material between the first and second electrode patterns, and extends radially outward from this region of the ferroelectric material and substantially parallel to the plane of the ferroelectric material. The piezo-diaphragm deflects symmetrically about this region in a direction substantially perpendicular to the electric field. An annular region coupled to and extending radially outward from the piezo-diaphragm perimetrically borders the piezo-diaphragm, A housing is connected to the region and at least one fluid flow path with piezo-diaphragm disposed therein.

Finite size effects in ferroelectric-semiconductor thin films under open-circuit electric boundary conditions

DOE PAGES

Eliseev, Eugene A.; Kalinin, Sergei V.; Morozovska, Anna N.

2015-01-21

General features of finite size effects in the ferroelectric-semiconductor film under open-circuit electric boundary conditions are analyzed using Landau-Ginzburg-Devonshire theory and continuum media electrostatics. The temperature dependence of the film critical thickness, spontaneous polarization and depolarization field profiles of the open-circuited films are found to be significantly different from the characteristics of short-circuited ones. In particular, we predict the re-entrant type transition boundary between the mono-domain and poly-domain ferroelectric states due to reduced internal screening efficiency and analyzed possible experimental scenarios created by this mechanism. Performed analysis is relevant for the quantitative description of free-standing ferroelectric films phase diagrams andmore » polar properties. Also our results can be useful for the explanation of the scanning-probe microscopy experiments on free ferroelectric surfaces.« less

Microstructure research for ferroelectric origin in the strained Hf0.5Zr0.5O2 thin film via geometric phase analysis

NASA Astrophysics Data System (ADS)

Bi, Han; Sun, Qingqing; Zhao, Xuebing; You, Wenbin; Zhang, David Wei; Che, Renchao

2018-04-01

Recently, non-volatile semiconductor memory devices using a ferroelectric Hf0.5Zr0.5O2 film have been attracting extensive attention. However, at the nano-scale, the phase structure remains unclear in a thin Hf0.5Zr0.5O2 film, which stands in the way of the sustained development of ferroelectric memory nano-devices. Here, a series of electron microscopy evidences have illustrated that the interfacial strain played a key role in inducing the orthorhombic phase and the distorted tetragonal phase, which was the origin of the ferroelectricity in the Hf0.5Zr0.5O2 film. Our results provide insight into understanding the association between ferroelectric performances and microstructures of Hf0.5Zr0.5O2-based systems.

Writing and Reading of Ultrathin Ferroelectric Domains on Commensurate SrTiO3 on Silicon

NASA Astrophysics Data System (ADS)

Levy, Jeremy; Cen, Cheng; Sleasman, Charles R.; Warusawithana, Maitri; Schlom, Darrell G.

2008-03-01

Ferroelectricity in ultrathin epitaxial SrTiO3 grown commensurately by oxide-molecular beam epitaxy (MBE) on silicon substrates was investigated using piezoforce microscopy (PFM). A series of samples containing n molecular layers (ML) of SrTiO3 (n = 3, 4, 5, 6, 8, 10, 20) was grown on silicon substrates. Room-temperature ferroelectricity was observed for samples containing n = 5, 6, 8, 10 ML. Temperature-dependent measurements indicate that the sample with n = 5 exhibits a ferroelectric phase transition at Tc˜317 K. Sample with n = 6 remains ferroelectric up to at least 393K. Polar domains created on the n = 6 was found to be stable at room temperature for more than 72 hours. The implications of these results for fundamental and device-related applications will be discussed briefly.

Al-, Y-, and La-doping effects favoring intrinsic and field induced ferroelectricity in HfO2: A first principles study

NASA Astrophysics Data System (ADS)

Materlik, Robin; Künneth, Christopher; Falkowski, Max; Mikolajick, Thomas; Kersch, Alfred

2018-04-01

III-valent dopants have shown to be most effective in stabilizing the ferroelectric, crystalline phase in atomic layer deposited, polycrystalline HfO2 thin films. On the other hand, such dopants are commonly used for tetragonal and cubic phase stabilization in ceramic HfO2. This difference in the impact has not been elucidated so far. The prospect is a suitable doping to produce ferroelectric HfO2 ceramics with a technological impact. In this paper, we investigate the impact of Al, Y, and La doping, which have experimentally proven to stabilize the ferroelectric Pca21 phase in HfO2, in a comprehensive first-principles study. Density functional theory calculations reveal the structure, formation energy, and total energy of various defects in HfO2. Most relevant are substitutional electronically compensated defects without oxygen vacancy, substitutional mixed compensated defects paired with a vacancy, and ionically compensated defect complexes containing two substitutional dopants paired with a vacancy. The ferroelectric phase is strongly favored with La and Y in the substitutional defect. The mixed compensated defect favors the ferroelectric phase as well, but the strongly favored cubic phase limits the concentration range for ferroelectricity. We conclude that a reduction of oxygen vacancies should significantly enhance this range in Y doped HfO2 thin films. With Al, the substitutional defect hardly favors the ferroelectric phase before the tetragonal phase becomes strongly favored with the increasing concentration. This could explain the observed field induced ferroelectricity in Al-doped HfO2. Further Al defects are investigated, but do not favor the f-phase such that the current explanation remains incomplete for Al doping. According to the simulation, doping alone shows clear trends, but is insufficient to replace the monoclinic phase as the ground state. To explain this fact, some other mechanism is needed.

Fractal model of polarization switching kinetics in ferroelectrics under nonequilibrium conditions of electron irradiation

NASA Astrophysics Data System (ADS)

Maslovskaya, A. G.; Barabash, T. K.

2018-03-01

The paper presents the results of the fractal and multifractal analysis of polarization switching current in ferroelectrics under electron irradiation, which allows statistical memory effects to be estimated at dynamics of domain structure. The mathematical model of formation of electron beam-induced polarization current in ferroelectrics was suggested taking into account the fractal nature of domain structure dynamics. In order to realize the model the computational scheme was constructed using the numerical solution approximation of fractional differential equation. Evidences of electron beam-induced polarization switching process in ferroelectrics were specified at a variation of control model parameters.

Microwave properties of film Ba x Sr1 - x TiO3 ferroelectric variconds with a magnesium-containing additive

NASA Astrophysics Data System (ADS)

Tumarkin, A. V.; Tepina, E. R.; Nenasheva, E. A.; Kartenko, N. F.; Kozyrev, A. B.

2012-06-01

The electrophysical properties of bulk ceramics based on Ba x Sr1 - x TiO3 solid solutions with a Mg-containing additive and planar variconds based on ferroelectric films obtained by the ion-plasma sputtering of targets with different elemental compositions are studied. Controllability n( U) = C(0)/ C( U) and the dielectric loss tangent (tanδ) of ferroelectric variconds are measured as functions of the elemental composition of the ferroelectric. The figure of merit of the variconds is estimated, and the film composition providing the best electrophysical parameters is determined.

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.

Solitons in thin-film ferroelectric material

NASA Astrophysics Data System (ADS)

Boudoue Hubert, Malwe; Justin, Mibaile; Kudryashov, Nikolai A.; Betchewe, Gambo; Douvagai; Doka, Serge Y.

2018-07-01

Through the Landau–Ginzburg–Devonshire mean field theory, the equation governing the behavior of the polarization field in ferroelectric material is derived. Ferroelectric material is subjected to a standing electric field which inhibits remanent polarization and facilitates the access to the instantaneous polarization. Some transformations turn the equation into a well-known ordinary differential equation. As a result, dark soliton and cnoidal waves, which have not yet been observed in ferroelectrics, are obtained. Also, a bright soliton is found. It exists in a given range of temperatures and has an amplitude and a width which vary inversely with temperature.

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.

Understanding Polymorphism Formation in Electrospun Fibers of Immiscible Poly(vinylidene fluoride) Blends

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

G Zhong; L Zhang; R Su

2011-12-31

Effects of electric poling, mechanical stretching, and dipolar interaction on the formation of ferroelectric ({beta} and/or {gamma}) phases in poly(vinylidene fluoride) (PVDF) have been studied in electrospun fibers of PVDF/polyacrylonitrile (PAN) and PVDF/polysulfone (PSF) blends with PVDF as the minor component, using wide-angle X-ray diffraction and Fourier transform infrared techniques. Experimental results of as-electrospun neat PVDF fibers (beaded vs. bead-free) showed that mechanical stretching during electrospinning, rather than electric poling, was effective to induce ferroelectric phases. For as-electrospun PVDF blend fibers with the non-polar PSF matrix, mechanical stretching during electrospinning again was capable of inducing some ferroelectric phases in additionmore » to the major paraelectric ({alpha}) phase. However, after removing the mechanical stretching in a confined melt-recrystallization process, only the paraelectric phase was obtained. For as-electrospun PVDF blend fibers with the polar (or ferroelectric) PAN matrix, strong intermolecular interactions between polar PAN and PVDF played an important role in the ferroelectric phase formation in addition to the mechanical stretching effect during electrospinning. Even after the removal of mechanical stretching through the confined melt-recrystallization process, a significant amount of ferroelectric phases persisted. Comparing the ferroelectric phase formation between PVDF/PSF and PVDF/PAN blend fibers, we concluded that the local electric field-dipole interactions were the determining factor for the nucleation and growth of polar PVDF phases.« less

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.

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.

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.

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.

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.

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.

A review of molecular beam epitaxy of ferroelectric BaTiO3 films on Si, Ge and GaAs substrates and their applications

PubMed Central

Mazet, Lucie; Yang, Sang Mo; Kalinin, Sergei V; Schamm-Chardon, Sylvie; Dubourdieu, Catherine

2015-01-01

SrTiO3 epitaxial growth by molecular beam epitaxy (MBE) on silicon has opened up the route to the monolithic integration of various complex oxides on the complementary metal-oxide–semiconductor silicon platform. Among functional oxides, ferroelectric perovskite oxides offer promising perspectives to improve or add functionalities on-chip. We review the growth by MBE of the ferroelectric compound BaTiO3 on silicon (Si), germanium (Ge) and gallium arsenide (GaAs) and we discuss the film properties in terms of crystalline structure, microstructure and ferroelectricity. Finally, we review the last developments in two areas of interest for the applications of BaTiO3 films on silicon, namely integrated photonics, which benefits from the large Pockels effect of BaTiO3, and low power logic devices, which may benefit from the negative capacitance of the ferroelectric. PMID:27877816

Incipient ferroelectricity of water molecules confined to nano-channels of beryl

NASA Astrophysics Data System (ADS)

Gorshunov, B. P.; Torgashev, V. I.; Zhukova, E. S.; Thomas, V. G.; Belyanchikov, M. A.; Kadlec, C.; Kadlec, F.; Savinov, M.; Ostapchuk, T.; Petzelt, J.; Prokleška, J.; Tomas, P. V.; Pestrjakov, E. V.; Fursenko, D. A.; Shakurov, G. S.; Prokhorov, A. S.; Gorelik, V. S.; Kadyrov, L. S.; Uskov, V. V.; Kremer, R. K.; Dressel, M.

2016-09-01

Water is characterized by large molecular electric dipole moments and strong interactions between molecules; however, hydrogen bonds screen the dipole-dipole coupling and suppress the ferroelectric order. The situation changes drastically when water is confined: in this case ordering of the molecular dipoles has been predicted, but never unambiguously detected experimentally. In the present study we place separate H2O molecules in the structural channels of a beryl single crystal so that they are located far enough to prevent hydrogen bonding, but close enough to keep the dipole-dipole interaction, resulting in incipient ferroelectricity in the water molecular subsystem. We observe a ferroelectric soft mode that causes Curie-Weiss behaviour of the static permittivity, which saturates below 10 K due to quantum fluctuations. The ferroelectricity of water molecules may play a key role in the functioning of biological systems and find applications in fuel and memory cells, light emitters and other nanoscale electronic devices.

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

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.

Synthesis, characterization, properties, and applications of nanosized ferroelectric, ferromagnetic, or multiferroic materials

DOE PAGES

Dhak, Debasis; Hong, Seungbum; Das, Soma; ...

2015-01-01

Recently, there has been an enormous increase in research activity in the field of ferroelectrics and ferromagnetics especially in multiferroic materials which possess both ferroelectric and ferromagnetic properties simultaneously. However, the ferroelectric, ferromagnetic, and multiferroic properties should be further improved from the utilitarian and commercial viewpoints. Nanostructural materials are central to the evolution of future electronics and information technologies. Ferroelectrics and ferromagnetics have already been established as a dominant branch in electronics sector because of their diverse applications. The ongoing dimensional downscaling of materials to allow packing of increased numbers of components into integrated circuits provides the momentum for evolutionmore » of nanostructural devices. Nanoscaling of the above materials can result in a modification of their functionality. Furthermore, nanoscaling can be used to form high density arrays of nanodomain nanostructures, which is desirable for miniaturization of devices.« less

Tunnel junctions with multiferroic barriers

NASA Astrophysics Data System (ADS)

Gajek, Martin; Bibes, Manuel; Fusil, Stéphane; Bouzehouane, Karim; Fontcuberta, Josep; Barthélémy, Agnès; Fert, Albert

2007-04-01

Multiferroics are singular materials that can exhibit simultaneously electric and magnetic orders. Some are ferroelectric and ferromagnetic and provide the opportunity to encode information in electric polarization and magnetization to obtain four logic states. However, such materials are rare and schemes allowing a simple electrical readout of these states have not been demonstrated in the same device. Here, we show that films of La0.1Bi0.9MnO3 (LBMO) are ferromagnetic and ferroelectric, and retain both ferroic properties down to a thickness of 2nm. We have integrated such ultrathin multiferroic films as barriers in spin-filter-type tunnel junctions that exploit the magnetic and ferroelectric degrees of freedom of LBMO. Whereas ferromagnetism permits read operations reminiscent of magnetic random access memories (MRAM), the electrical switching evokes a ferroelectric RAM write operation. Significantly, our device does not require the destructive ferroelectric readout, and therefore represents an advance over the original four-state memory concept based on multiferroics.

Tunnel junctions with multiferroic barriers.

PubMed

Gajek, Martin; Bibes, Manuel; Fusil, Stéphane; Bouzehouane, Karim; Fontcuberta, Josep; Barthélémy, Agnès; Fert, Albert

2007-04-01

Multiferroics are singular materials that can exhibit simultaneously electric and magnetic orders. Some are ferroelectric and ferromagnetic and provide the opportunity to encode information in electric polarization and magnetization to obtain four logic states. However, such materials are rare and schemes allowing a simple electrical readout of these states have not been demonstrated in the same device. Here, we show that films of La(0.1)Bi(0.9)MnO(3) (LBMO) are ferromagnetic and ferroelectric, and retain both ferroic properties down to a thickness of 2 nm. We have integrated such ultrathin multiferroic films as barriers in spin-filter-type tunnel junctions that exploit the magnetic and ferroelectric degrees of freedom of LBMO. Whereas ferromagnetism permits read operations reminiscent of magnetic random access memories (MRAM), the electrical switching evokes a ferroelectric RAM write operation. Significantly, our device does not require the destructive ferroelectric readout, and therefore represents an advance over the original four-state memory concept based on multiferroics.

Electrooptic crystal growth and properties

NASA Astrophysics Data System (ADS)

1994-02-01

A new member in the tungsten-bronze family of ferroelectric lead potassium niobate (PKN), with general formula Pb(1-x)K(2x)Nb2O6, has been grown as bulk single crystal. Growth of PKN with charge composition x = 0.23 has been achieved using the Czochralski technique of crystal pulling. Large diameter boules were grown in platinum crucibles at temperatures between 1280 and 1300 C. Crystallographic studies were conducted using x ray diffraction techniques. The samples were characterized for ferroelectric properties between 25 and 600 C and for optical absorption. This paper presents the crystal synthesis and the results of ferroelectric and optical characterization. Bulk single crystals of potassium tantalate niobate, KTa(1-x)Nb(x)O3, ferroelectric with different values of Ta/Nb ratios have been grown by temperature gradient transport technique (TGTT). A second attached paper presents the results of the crystal growth experiments, ferroelectric characterization techniques, and properties of potassium tantalate niobate crystals.

Imprint control of BaTiO 3 thin films via chemically induced surface polarization pinning

DOE PAGES

Lee, Hyungwoo; Kim, Tae Heon; Patzner, Jacob J.; ...

2016-02-22

Surface-adsorbed polar molecules can significantly alter the ferroelectric properties of oxide thin films. Thus, fundamental understanding and controlling the effect of surface adsorbates are crucial for the implementation of ferroelectric thin film devices, such as ferroelectric tunnel junctions. Herein, we report an imprint control of BaTiO 3 (BTO) thin films by chemically induced surface polarization pinning in the top few atomic layers of the water-exposed BTO films. Our studies based on synchrotron X-ray scattering and coherent Bragg rod analysis demonstrate that the chemically induced surface polarization is not switchable but reduces the polarization imprint and improves the bistability of ferroelectricmore » phase in BTO tunnel junctions. Here, we conclude that the chemical treatment of ferroelectric thin films with polar molecules may serve as a simple yet powerful strategy to enhance functional properties of ferroelectric tunnel junctions for their practical applications.« less

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.

Simulation of interface dislocations effect on polarization distribution of ferroelectric thin films

NASA Astrophysics Data System (ADS)

Zheng, Yue; Wang, Biao; Woo, C. H.

2006-02-01

Effects of interfacial dislocations on the properties of ferroelectric thin films are investigated, using the dynamic Ginzburg-Landau equation. Our results confirm the existence of a dead layer near the film/substrate interface. Due to the combined effects of the dislocations and the near-surface eigenstrain relaxation, the ferroelectric properties of about one-third of the film volume suffers.

Homo-junction ferroelectric field-effect-transistor memory device using solution-processed lithium-doped zinc oxide thin films

NASA Astrophysics Data System (ADS)

Nayak, Pradipta K.; Caraveo-Frescas, J. A.; Bhansali, Unnat. S.; Alshareef, H. N.

2012-06-01

High performance homo-junction field-effect transistor memory devices were prepared using solution processed transparent lithium-doped zinc oxide thin films for both the ferroelectric and semiconducting active layers. A highest field-effect mobility of 8.7 cm2/Vs was obtained along with an Ion/Ioff ratio of 106. The ferroelectric thin film transistors showed a low sub-threshold swing value of 0.19 V/dec and a significantly reduced device operating voltage (±4 V) compared to the reported hetero-junction ferroelectric transistors, which is very promising for low-power non-volatile memory applications.

Lattice-Rotation Vortex at the Charged Monoclinic Domain Boundary in a Relaxor Ferroelectric Crystal

NASA Astrophysics Data System (ADS)

Shao, Yu-Tsun; Zuo, Jian-Min

2017-04-01

We present evidence of lattice-rotation vortices having an average radius of ˜7 nm at the ferroelectric domain boundary of (1 -x )Pb (Zn1 /3Nb2 /3)O3-xPbTiO3 (x =0.08 ). Maps of crystal orientations and domain symmetry breaking are obtained using scanning convergent beam electron diffraction, which show fractional rotation vortices near the 50° monoclinic domain walls. The merging of 2D and 1D topological defects is consistent with inhomogeneous boundary charge and expected to have a large impact on the domain-switching mechanisms in relaxor ferroelectric crystals and ferroelectric devices.

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.

Ferroelectric properties of a triphenylene derivative with polar functional groups in the crystalline state

NASA Astrophysics Data System (ADS)

Sugita, Atsushi; Suzuki, Kyoko; Tasaka, Shigeru

2004-06-01

We studied ferroelectric ordering in a triphenylene derivative embedded with electric dipoles [2,3,6,7,10,11-hexakis (4-octyloxy-benzoyloxy) triphenylene (HOBPT)] in a crystalline state. Experimental results indicate that the ferroelectricity in HOBPT is caused by an ordered orientation of CO dipoles. Our experiments also reveal that dielectric anomaly due to ferroelectric paraelectric phase transition occurs at 380 K . A photovoltaic effect was observed in an electrically treated thin film of HOBPT. The phenomenon results from a high charge mobility due to the π-π stack between adjacent molecules as well as an internal electric field derived by the residual polarization.

Nondestructive Memory Elements Based on Polymeric Langmuir-Blodgett Thin Films

NASA Astrophysics Data System (ADS)

Reece, T. J.; Ducharme, S.

2007-03-01

Ferroelectric field effect transistors (FeFETs) have attracted much attention recently because of their low power consumption and fast nondestructive readout. Among the ferroelectric thin films used in FET devices; the ferroelectric copolymer of polyvinylidene fluoride, PVDF (C2H2F2), with trifluoroethylene, TrFE (C2HF3), has distinct advantages, including low dielectric constant, low processing temperature, low cost and compatibility with organic semiconductors. By employing the Langmuir-Blodgett technique, we are able to deposit films as thin as 1.8 nm. We discuss the characterization, modeling and fabrication of metal-ferroelectric-insulator-semiconductor (MFIS) structures incorporating these films.

On the persistence of polar domains in ultrathin ferroelectric capacitors.

PubMed

Zubko, Pavlo; Lu, Haidong; Bark, Chung-Wung; Martí, Xavi; Santiso, José; Eom, Chang-Beom; Catalan, Gustau; Gruverman, Alexei

2017-07-19

The instability of ferroelectric ordering in ultra-thin films is one of the most important fundamental issues pertaining realization of a number of electronic devices with enhanced functionality, such as ferroelectric and multiferroic tunnel junctions or ferroelectric field effect transistors. In this paper, we investigate the polarization state of archetypal ultrathin (several nanometres) ferroelectric heterostructures: epitaxial single-crystalline BaTiO 3 films sandwiched between the most habitual perovskite electrodes, SrRuO 3 , on top of the most used perovskite substrate, SrTiO 3 . We use a combination of piezoresponse force microscopy, dielectric measurements and structural characterization to provide conclusive evidence for the ferroelectric nature of the relaxed polarization state in ultrathin BaTiO 3 capacitors. We show that even the high screening efficiency of SrRuO 3 electrodes is still insufficient to stabilize polarization in SrRuO 3 /BaTiO 3 /SrRuO 3 heterostructures at room temperature. We identify the key role of domain wall motion in determining the macroscopic electrical properties of ultrathin capacitors and discuss their dielectric response in the light of the recent interest in negative capacitance behaviour.

Charge ordering, ferroelectric, and magnetic domains in LuFe{sub 2}O{sub 4} observed by scanning probe microscopy

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

Yang, I. K.; Jeong, Y. H., E-mail: yhj@postech.ac.kr; Kim, Jeehoon

2015-04-13

LuFe{sub 2}O{sub 4} is a multiferroic system which exhibits charge order, ferroelectricity, and ferrimagnetism simultaneously below ∼230 K. The ferroelectric/charge order domains of LuFe{sub 2}O{sub 4} are imaged with both piezoresponse force microscopy (PFM) and electrostatic force microscopy (EFM), while the magnetic domains are characterized by magnetic force microscopy (MFM). Comparison of PFM and EFM results suggests that the proposed ferroelectricity in LuFe{sub 2}O{sub 4} is not of usual displacive type but of electronic origin. Simultaneous characterization of ferroelectric/charge order and magnetic domains by EFM and MFM, respectively, on the same surface of LuFe{sub 2}O{sub 4} reveals that both domains havemore » irregular patterns of similar shape, but the length scales are quite different. The domain size is approximately 100 nm for the ferroelectric domains, while the magnetic domain size is much larger and gets as large as 1 μm. We also demonstrate that the origin of the formation of irregular domains in LuFe{sub 2}O{sub 4} is not extrinsic but intrinsic.« less

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.

Ferroelectric properties of full plasma-enhanced ALD TiN/La:HfO{sub 2}/TiN stacks

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

Chernikova, A. G.; Kuzmichev, D. S.; Negrov, D. V.

2016-06-13

We report the possibility of employment of low temperature (≤330 °C) plasma-enhanced atomic layer deposition for the formation of both electrodes and hafnium-oxide based ferroelectric in the metal-insulator-metal structures. The structural and ferroelectric properties of La doped HfO{sub 2}-based layers and its evolution with the change of both La content (2.1, 3.7 and 5.8 at. %) and the temperature of the rapid thermal processing (550–750 °C) were investigated in detail. Ferroelectric properties emerged only for 2.1 and 3.7 at. % of La due to the structural changes caused by the given doping levels. Ferroelectric properties were also found to depend strongly on annealing temperature,more » with the most robust ferroelectric response for lowest La concentration and intermediate 650 °C annealing temperature. The long term wake-up effect and such promising endurance characteristics as 3 × 10{sup 8} switches by bipolar voltage cycles with 30 μs duration and ± 3 MV/cm amplitude without any decrease of remnant polarization value were demonstrated.« less

Electric and ferroelectric properties of PZT/BLT multilayer films prepared by photochemical metal-organic deposition

NASA Astrophysics Data System (ADS)

Park, Hyeong-Ho; Lee, Hong-Sub; Park, Hyung-Ho; Hill, Ross H.; Hwang, Yun Taek

2009-01-01

The electric and ferroelectric properties of lead zirconate titanate (PZT) and lanthanum-substituted bismuth titanate (BLT) multilayer films prepared using photosensitive precursors were characterized. The electric and ferroelectric properties were investigated by studying the effect of the stacking order of four ferroelectric layers of PZT or BLT in 4-PZT, PZT/2-BLT/PZT, BLT/2-PZT/BLT, and 4-BLT multilayer films. The remnant polarization values of the 4-BLT and BLT/2-PZT/BLT multilayer films were 12 and 17 μC/cm 2, respectively. Improved ferroelectric properties of the PZT/BLT multilayer films were obtained by using a PZT intermediate layer. The films which contained a BLT layer on the Pt substrate had improved leakage currents of approximately two orders of magnitude and enhanced fatigue resistances compared to the films with a PZT layer on the Pt substrate. These improvements are due to the reduced number of defects and space charges near the Pt electrodes. The PZT/BLT multilayer films prepared by photochemical metal-organic deposition (PMOD) possessed enhanced electric and ferroelectric properties, and allow direct patterning to fabricate micro-patterned systems without dry etching.

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.

Lattice rotation vortex observed between polar nanoregions in relaxor-ferroelectric (1-x)Pb(Zn1/3Nb2/3) O3-xPbTiO3 single crystal

NASA Astrophysics Data System (ADS)

Shao, Yu-Tsun; Zuo, Jian-Min

Domain walls (DWs) play a critical role in determining the polarization switching behavior in relaxor-based ferroelectric crystals. The domains in relaxor-ferroelectric crystals consist of polar nanoregions (PNRs) and their interface is poorly understood. Here, we report an energy-filtered (EF-) scanning convergent beam electron diffraction (SCBED) study for the identification of PNRs and determination of their interface. With the aid of electro dynamical diffraction simulation, nanometer-sized PNRs having monoclinic Pm (MC) symmetry in single crystal PZN- 8%PT were identified. Lattice rotation vortices having an average radius of 7 nm at the 50° DWs were revealed by maps of crystal orientations, domain configurations, symmetry breaking. Such measurements suggest the merging of 2D and 1D topological defects, with implications for domain-switching mechanisms in relaxor ferroelectric crystals. The interplay between polarization, charge, and strain degrees of freedom suggests a complex landscape of topological defects in ferroelectrics that may be explored for a new form of nanoscale ferroelectric devices. Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign.

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.

Plasma-Assisted Dry Etching of Ferroelectric Capacitor Modules and Application to a 32M Ferroelectric Random Access Memory Devices with Submicron Feature Sizes

NASA Astrophysics Data System (ADS)

Lee, Sang-Woo; Joo, Suk-Ho; Cho, Sung Lae; Son, Yoon-Ho; Lee, Kyu-Mann; Nam, Sang-Don; Park, Kun-Sang; Lee, Yong-Tak; Seo, Jung-Suk; Kim, Young-Dae; An, Hyeong-Geun; Kim, Hyoung-Joon; Jung, Yong-Ju; Heo, Jang-Eun; Lee, Moon-Sook; Park, Soon-Oh; Chung, U-In; Moon, Joo-Tae

2002-11-01

In the manufacturing of a 32M ferroelectric random access memory (FRAM) device on the basis of 0.25 design rule (D/R), one of the most difficult processes is to pattern a submicron capacitor module while retaining good ferroelectric properties. In this paper, we report the ferroelectric property of patterned submicron capacitor modules with a stack height of 380 nm, where the 100 nm-thick Pb(Zr, Ti)O3 (PZT) films were prepared by the sol-gel method. After patterning, overall sidewall slope was approximately 70° and cell-to-cell node separation was made to be 80 nm to prevent possible twin-bit failure in the device. Finally, several heat treatment conditions were investigated to retain the ferroelectric property of the patterned capacitor. It was found that rapid thermal processing (RTP) treatment yields better properties than conventional furnace annealing. This result is directly related to the near-surface chemistry of the PZT films, as confirmed by X-ray photoelectron spectroscopy (XPS) analysis. The resultant switching polarization value of the submicron capacitor was approximately 30 μC/cm2 measured at 3 V.

Effect of material constants on power output in piezoelectric vibration-based generators.

PubMed

Takeda, Hiroaki; Mihara, Kensuke; Yoshimura, Tomohiro; Hoshina, Takuya; Tsurumi, Takaaki

2011-09-01

A possible power output estimation based on material constants in piezoelectric vibration-based generators is proposed. A modified equivalent circuit model of the generator was built and was validated by the measurement results in the generator fabricated using potassium sodium niobate-based and lead zirconate titanate (PZT) ceramics. Subsequently, generators with the same structure using other PZT-based and bismuth-layered structure ferroelectrics ceramics were fabricated and tested. The power outputs of these generators were expressed as a linear functions of the term composed of electromechanical coupling coefficients k(sys)(2) and mechanical quality factors Q*(m) of the generator. The relationship between device constants (k(sys)(2) and Q*(m)) and material constants (k(31)(2) and Q(m)) was clarified. Estimation of the power output using material constants is demonstrated and the appropriate piezoelectric material for the generator is suggested.

Piezoelectricity and Ferroelectricity in Amino Acid Glycine =

NASA Astrophysics Data System (ADS)

Seyedhosseini, Ensieh

Bioorganic ferroelectrics and piezoelectrics are becoming increasingly important in view of their intrinsic compatibility with biological environment and biofunctionality combined with strong piezoelectric effect and switchable polarization at room temperature. Here we study piezoelectricity and ferroelectricity in the smallest amino acid glycine, representing a broad class of non-centrosymmetric amino acids. Glycine is one of the basic and important elements in biology, as it serves as a building block for proteins. Three polymorphic forms with different physical properties are possible in glycine (alpha, beta and gamma), Of special interest for various applications are non-centrosymmetric polymorphs: beta-glycine and gamma-glycine. The most useful beta-polymorph being ferroelectric took much less attention than the other due to its instability under ambient conditions. In this work, we could grow stable microcrystals of beta-glycine by the evaporation of aqueous solution on a (111)Pt/Ti/SiO2/Si substrate as a template. The effects of the solution concentration and Pt-assisted nucleation on the crystal growth and phase evolution were characterized by X-ray diffraction analysis and Raman spectroscopy. In addition, spin-coating technique was used for the fabrication of highly aligned nano-islands of beta-glycine with regular orientation of the crystallographic axes relative the underlying substrate (Pt). Further we study both as-grown and tip-induced domain structures and polarization switching in the beta-glycine molecular systems by Piezoresponse Force Microscopy (PFM) and compare the results with molecular modeling and computer simulations. We show that beta-glycine is indeed a room-temperature ferroelectric and polarization can be switched by applying a bias to non-polar cuts via a conducting tip of atomic force microscope (AFM). Dynamics of these in-plane domains is studied as a function of applied voltage and pulse duration. The domain shape is dictated by both internal and external polarization screening mediated by defects and topographic features. Thermodynamic theory is applied to explain the domain propagation induced by the AFM tip. Our findings suggest that beta-glycine is a uniaxial ferroelectric with the properties controlled by the charged domain walls which in turn can be manipulated by external bias. Besides, nonlinear optical properties of beta-glycine were investigated by a second harmonic generation (SHG) method. SHG method confirmed that the 2-fold symmetry is preserved in as-grown crystals, thus reflecting the expected P21 symmetry of the beta-phase. Spontaneous polarization direction is found to be parallel to the monoclinic [010] axis and directed along the crystal length. These data are confirmed by computational molecular modeling. Optical measurements revealed also relatively high values of the nonlinear optical susceptibility (50% greater than in the z-cut quartz). The potential of using stable beta-glycine crystals in various applications are discussed in this work.

Multi-floor cascading ferroelectric nanostructures: multiple data writing-based multi-level non-volatile memory devices

NASA Astrophysics Data System (ADS)

Hyun, Seung; Kwon, Owoong; Lee, Bom-Yi; Seol, Daehee; Park, Beomjin; Lee, Jae Yong; Lee, Ju Hyun; Kim, Yunseok; Kim, Jin Kon

2016-01-01

Multiple data writing-based multi-level non-volatile memory has gained strong attention for next-generation memory devices to quickly accommodate an extremely large number of data bits because it is capable of storing multiple data bits in a single memory cell at once. However, all previously reported devices have failed to store a large number of data bits due to the macroscale cell size and have not allowed fast access to the stored data due to slow single data writing. Here, we introduce a novel three-dimensional multi-floor cascading polymeric ferroelectric nanostructure, successfully operating as an individual cell. In one cell, each floor has its own piezoresponse and the piezoresponse of one floor can be modulated by the bias voltage applied to the other floor, which means simultaneously written data bits in both floors can be identified. This could achieve multi-level memory through a multiple data writing process.Multiple data writing-based multi-level non-volatile memory has gained strong attention for next-generation memory devices to quickly accommodate an extremely large number of data bits because it is capable of storing multiple data bits in a single memory cell at once. However, all previously reported devices have failed to store a large number of data bits due to the macroscale cell size and have not allowed fast access to the stored data due to slow single data writing. Here, we introduce a novel three-dimensional multi-floor cascading polymeric ferroelectric nanostructure, successfully operating as an individual cell. In one cell, each floor has its own piezoresponse and the piezoresponse of one floor can be modulated by the bias voltage applied to the other floor, which means simultaneously written data bits in both floors can be identified. This could achieve multi-level memory through a multiple data writing process. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr07377d

Dielectric Characterization of a Nonlinear Optical Material

PubMed Central

Lunkenheimer, P.; Krohns, S.; Gemander, F.; Schmahl, W. W.; Loidl, A.

2014-01-01

Batisite was reported to be a nonlinear optical material showing second harmonic generation. Using dielectric spectroscopy and polarization measurements, we provide a thorough investigation of the dielectric and charge-transport properties of this material. Batisite shows the typical characteristics of a linear lossy dielectric. No evidence for ferro- or antiferroelectric polarization is found. As the second-harmonic generation observed in batisite points to a non-centrosymmetric structure, this material is piezoelectric, but most likely not ferroelectric. In addition, we found evidence for hopping charge transport of localized charge carriers and a relaxational process at low temperatures. PMID:25109553

Magnetic Biasing of a Ferroelectric Hysteresis Loop in a Multiferroic Orthoferrite

NASA Astrophysics Data System (ADS)

Tokunaga, Y.; Taguchi, Y.; Arima, T.; Tokura, Y.

2014-01-01

In a multiferroic orthoferrite Dy0.7Tb0.3FeO3, which shows electric-field-(E-)driven magnetization (M) reversal due to a tight clamping between polarization (P) and M, a gigantic effect of magnetic-field (H) biasing on P-E hysteresis loops is observed in the case of rapid E sweeping. The magnitude of the bias E field can be controlled by varying the magnitude of H, and its sign can be reversed by changing the sign of H or the relative clamping direction between P and M. The origin of this unconventional biasing effect is ascribed to the difference in the Zeeman energy between the +P and -P states coupled with the M states with opposite sign.

Conduction at domain walls in oxide multiferroics

NASA Astrophysics Data System (ADS)

Seidel, J.; Martin, L. W.; He, Q.; Zhan, Q.; Chu, Y.-H.; Rother, A.; Hawkridge, M. E.; Maksymovych, P.; Yu, P.; Gajek, M.; Balke, N.; Kalinin, S. V.; Gemming, S.; Wang, F.; Catalan, G.; Scott, J. F.; Spaldin, N. A.; Orenstein, J.; Ramesh, R.

2009-03-01

Domain walls may play an important role in future electronic devices, given their small size as well as the fact that their location can be controlled. Here, we report the observation of room-temperature electronic conductivity at ferroelectric domain walls in the insulating multiferroic BiFeO3. The origin and nature of the observed conductivity are probed using a combination of conductive atomic force microscopy, high-resolution transmission electron microscopy and first-principles density functional computations. Our analyses indicate that the conductivity correlates with structurally driven changes in both the electrostatic potential and the local electronic structure, which shows a decrease in the bandgap at the domain wall. Additionally, we demonstrate the potential for device applications of such conducting nanoscale features.

Conduction at domain walls in oxide multiferroics.

PubMed

Seidel, J; Martin, L W; He, Q; Zhan, Q; Chu, Y-H; Rother, A; Hawkridge, M E; Maksymovych, P; Yu, P; Gajek, M; Balke, N; Kalinin, S V; Gemming, S; Wang, F; Catalan, G; Scott, J F; Spaldin, N A; Orenstein, J; Ramesh, R

2009-03-01

Domain walls may play an important role in future electronic devices, given their small size as well as the fact that their location can be controlled. Here, we report the observation of room-temperature electronic conductivity at ferroelectric domain walls in the insulating multiferroic BiFeO(3). The origin and nature of the observed conductivity are probed using a combination of conductive atomic force microscopy, high-resolution transmission electron microscopy and first-principles density functional computations. Our analyses indicate that the conductivity correlates with structurally driven changes in both the electrostatic potential and the local electronic structure, which shows a decrease in the bandgap at the domain wall. Additionally, we demonstrate the potential for device applications of such conducting nanoscale features.

Similarity between the response of memristive and memcapacitive circuits subjected to ramped voltage

NASA Astrophysics Data System (ADS)

Kanygin, Mikhail A.; Katkov, Mikhail V.; Pershin, Yuriy V.

2017-07-01

We report a similar feature in the response of resistor-memristor and capacitor-memcapacitor circuits with threshold-type memory devices driven by triangular waveform voltage. In both cases, the voltage across the memory device is stabilized during the switching of the memory device state. While in the memristive circuit this feature is observed when the applied voltage changes in one direction, the memcapacitive circuit with a ferroelectric memcapacitor demonstrates the voltage stabilization effect at both sweep directions. The discovered behavior of capacitor-memcapacitor circuit is also demonstrated experimentally. We anticipate that our observation can be used in the design of electronic circuits with emergent memory devices as well as in the identification and characterization of memory effects in threshold-type memory devices.

Evaluation of domain randomness in periodically poled lithium niobate by diffraction noise measurement.

PubMed

Dwivedi, Prashant Povel; Choi, Hee Joo; Kim, Byoung Joo; Cha, Myoungsik

2013-12-16

Random duty-cycle errors (RDE) in ferroelectric quasi-phase-matching (QPM) devices not only affect the frequency conversion efficiency, but also generate non-phase-matched parasitic noise that can be detrimental to some applications. We demonstrate an accurate but simple method for measuring the RDE in periodically poled lithium niobate. Due to the equivalence between the undepleted harmonic generation spectrum and the diffraction pattern from the QPM grating, we employed linear diffraction measurement which is much simpler than tunable harmonic generation experiments [J. S. Pelc, et al., Opt. Lett.36, 864-866 (2011)]. As a result, we could relate the RDE for the QPM device to the relative noise intensity between the diffraction orders.

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.

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.