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Sample records for ferroelectric recording technology

  1. Ferroelectric Based Technologies for Accelerators

    SciTech Connect

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

    2009-01-22

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

  2. Records Reaching Recording Data Technologies

    NASA Astrophysics Data System (ADS)

    Gresik, G. W. L.; Siebe, S.; Drewello, R.

    2013-07-01

    The goal of RECORDS (Reaching Recording Data Technologies) is the digital capturing of buildings and cultural heritage objects in hard-to-reach areas and the combination of data. It is achieved by using a modified crane from film industry, which is able to carry different measuring systems. The low-vibration measurement should be guaranteed by a gyroscopic controlled advice that has been , developed for the project. The data were achieved by using digital photography, UV-fluorescence photography, infrared reflectography, infrared thermography and shearography. Also a terrestrial 3D laser scanner and a light stripe topography scanner have been used The combination of the recorded data should ensure a complementary analysis of monuments and buildings.

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

    NASA Astrophysics Data System (ADS)

    Aoki, Tomonori; Hiranaga, Yoshiomi; Cho, Yasuo

    2016-05-01

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

  4. Actual information storage with a recording density of 4 Tbit/in.2 in a ferroelectric recording medium

    NASA Astrophysics Data System (ADS)

    Tanaka, Kenkou; Cho, Yasuo

    2010-08-01

    A new method to achieve real information recording with a density above 1 Tbit/in.2 in ferroelectric data storage systems is proposed. In this system, data bits were written in the form of the polarization direction, and the data were read by scanning nonlinear dielectric microscopy technique. The domain-switching characteristics of the virgin and inversely prepolarized media were compared, and the conditions of the pulse voltage for writing were optimized. As a result, actual data containing 64×64 bits were recorded at an areal density of 4 Tbit/in.2. The bit error rate was evaluated to be 1.2×10-2.

  5. Recording and Reproduction in Ultrahigh-Density Ferroelectric Medium LiTaO3 through Lubricant Layer

    NASA Astrophysics Data System (ADS)

    Mori, Shuntato; Takahashi, Hirokazu; Maeda, Takanori; Onoe, Atsushi

    2008-10-01

    It is indispensable to reduce the friction between a ferroelectric recording medium and probe tips, and to eliminate the wear of tips to improve reliability toward the practical use in the ferroelectric probe memory (FPM) we are studying. Perfluoropolyether (PFPE) lubricant of 20 nm thickness was spread uniformly on a congruent LiTaO3 (CLT) ferroelectric recording medium as one of the measures against friction and wear. We conducted a polarization domain measurement and a dot array recording experiment with the lubricated CLT where frictional forces were reduced by 70%. The polarization signals of the medium were successfully measured with a high signal-to-noise ratio and recorded as dot arrays of 1.2 Tbit/in.2 density through the lubricant.

  6. Current Development Status and Future Challenges of Ferroelectric Random Access Memory Technologies

    NASA Astrophysics Data System (ADS)

    Lee, Sungyung; Kim, Kinam

    2006-04-01

    For ferroelectric random access memory (FRAM) to be beneficial in future mobile devices, high-density FRAM with nm scaled cell should be developed. We have succeeded in scaling further the cell size of one-pass transistor and one-storage capacitor (1T1C) FRAM down to 0.27 μm2 at 150 nm technology node. Owing to new SrRuO3 (SRO) electrode technology along with ultrathin PbZrTiO3 (PZT) using metal organic chemical vapor deposition (MOCVD) technology, two-dimensional (2-D) metal-insulator-metal (MIM) ferroelectric capacitor was successfully scaled down vertically to 200 nm. By the application of a new double hard mask capacitor etching technology, 0.11-μm2-area 200-nm-thick 2-D PZT capacitor was successfully isolated with 180 nm spacing. As a result, a high remanent polarization of 40 μC/cm2 was obtained at 1.6 V on a 0.11 μm2 ferroelectric storage capacitor of the 0.27 μm2 cell 1T1C FRAM. Great advances in three-dimensional (3-D) ferroelectric capacitor, which is essential for 6-8 F2 cell 1T1C FRAM at nm scaled technology node, have been made by introducing a new atomic layer deposition (ALD) method for 3-D electrode and a novel MOCVD PZT deposition for 3-D PZT. As a result, for the first time, robust hysteresis was obtained from a 3-D PZT capacitor.

  7. Robust Two-Dimensional Stack Capacitor Technologies for 64 Mbit One-Transistor-One-Capacitor Ferroelectric Random Access Memory

    NASA Astrophysics Data System (ADS)

    Jung, Ju-Young; Joo, Heung-Jin; Park, Jung-Hoon; Kang, Seung-Kuk; Kim, Hwi-San; Choi, Do-Yeon; Kim, Jai-Hyun; Lee, Eun-Sun; Hong, Young-Ki; Kim, Hyun-Ho; Jung, Dong-Jin; Kang, Young-Min; Lee, Sung-Yung; Jeong, Hong-Sik; Kim, Kinam

    2007-04-01

    It is very important to develop capacitor module technologies such as robust Pb(ZrxTi1-x)O3 (PZT) film technology at nm scaled PZT thickness and damage minimized ferroelectric capacitor etching technology are crucial for the success of high density one-transistor-one-capacitor (1T1C) ferroelectric random access memory (FRAM). We resolved this issue from the change of the capacitor etching system and optimization of the PZT/SrRuO3 (SRO) deposition process. As a result, we realized a highly reliable sensing window for 64 Mbit 1T1C FRAM that were realized by novel technologies such as robust MOCVD PZT deposition technologies, optimized SRO electrode and damage minimized ferroelectric capacitor etching technologies.

  8. 1 Tbit/in.2 Very-High-Density Recording in Mass-Productive Polycrystalline Ferroelectric Thin Film Media

    NASA Astrophysics Data System (ADS)

    Fujimoto, Kenjiro; Kawano, Takahiro; Onoe, Atsushi; Tamura, Masahiro; Umeda, Masaru; Toda, Masayuki

    2009-07-01

    We demonstrate very-high-density ferroelectric recording experiments of 1 Tbit/in.2 in polycrystalline Pb(Zr,Ti)O3 (PZT) thin film for the first time. A high-quality polycrystalline PZT thin film was successfully deposited on a silicon substrate with a SrRuO3 (SRO) electrode by metal-organic chemical vapor deposition (MOCVD). The roughness of the PZT film was reduced to less than 1 nm by chemical mechanical polishing (CMP). The PZT film has very high controllability for domain inversion. Our fabrication process also enables high productivity. Therefore, our PZT film has potential to be a mass-productive ferroelectric recording medium for high-density storage systems.

  9. Ferroelectric memory

    NASA Astrophysics Data System (ADS)

    Vorotilov, K. A.; Sigov, A. S.

    2012-05-01

    The current status of developments in the field of ferroelectric memory devices has been considered. The rapidly growing market of non-volatile memory devices has been analyzed, and the current state of the art and prospects for the scaling of parameters of non-volatile memory devices of different types have been considered. The basic constructive and technological solutions in the field of the design of ferroelectric memory devices, as well as the "roadmaps" of the development of this technology, have been discussed.

  10. Recording vocalizations with Bluetooth technology.

    PubMed

    Gaona-González, Andrés; Santillán-Doherty, Ana María; Arenas-Rosas, Rita Virginia; Muñoz-Delgado, Jairo; Aguillón-Pantaleón, Miguel Angel; Ordoñez-Gómez, José Domingo; Márquez-Arias, Alejandra

    2011-06-01

    We propose a method for capturing vocalizations that is designed to avoid some of the limiting factors found in traditional bioacoustical methods, such as the impossibility of obtaining continuous long-term registers or analyzing amplitude due to the continuous change of distance between the subject and the position of the recording system. Using Bluetooth technology, vocalizations are captured and transmitted wirelessly into a receiving system without affecting the quality of the signal. The recordings of the proposed system were compared to those obtained as a reference, which were based on the coding of the signal with the so-called pulse-code modulation technique in WAV audio format without any compressing process. The evaluation showed p < .05 for the measured quantitative and qualitative parameters. We also describe how the transmitting system is encapsulated and fixed on the animal and a way to video record a spider monkey's behavior simultaneously with the audio recordings. PMID:21359909

  11. Polymer ferroelectric field-effect memory device with SnO channel layer exhibits record hole mobility

    PubMed Central

    Caraveo-Frescas, J. A.; Khan, M. A.; Alshareef, H. N.

    2014-01-01

    Here we report for the first time a hybrid p-channel polymer ferroelectric field-effect transistor memory device with record mobility. The memory device, fabricated at 200°C on both plastic polyimide and glass substrates, uses ferroelectric polymer P(VDF-TrFE) as the gate dielectric and transparent p-type oxide (SnO) as the active channel layer. A record mobility of 3.3 cm2V−1s−1, large memory window (∼16 V), low read voltages (∼−1 V), and excellent retention characteristics up to 5000 sec have been achieved. The mobility achieved in our devices is over 10 times higher than previously reported polymer ferroelectric field-effect transistor memory with p-type channel. This demonstration opens the door for the development of non-volatile memory devices based on dual channel for emerging transparent and flexible electronic devices. PMID:24912617

  12. 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

  13. Video recording technology and its prospects

    NASA Astrophysics Data System (ADS)

    Oshima, Hideo

    1994-06-01

    The progress of broadcasting digitization technologies has produced digital VTRs for field use which are quickly replacing the conventional analog versions. In parallel with these developments, advanced high-density recording and image-data compression technologies have created the possibility for home VTRs to be digitized as well so that they may even be able to record/play back Hi-Vision programs. This paper discusses the current status and future prospects of video recording technology centering on digital VTRs.

  14. Photonic quantum technologies (Presentation Recording)

    NASA Astrophysics Data System (ADS)

    O'Brien, Jeremy L.

    2015-09-01

    The impact of quantum technology will be profound and far-reaching: secure communication networks for consumers, corporations and government; precision sensors for biomedical technology and environmental monitoring; quantum simulators for the design of new materials, pharmaceuticals and clean energy devices; and ultra-powerful quantum computers for addressing otherwise impossibly large datasets for machine learning and artificial intelligence applications. However, engineering quantum systems and controlling them is an immense technological challenge: they are inherently fragile; and information extracted from a quantum system necessarily disturbs the system itself. Of the various approaches to quantum technologies, photons are particularly appealing for their low-noise properties and ease of manipulation at the single qubit level. We have developed an integrated waveguide approach to photonic quantum circuits for high performance, miniaturization and scalability. We will described our latest progress in generating, manipulating and interacting single photons in waveguide circuits on silicon chips.

  15. Ultra-high density recording technologies

    NASA Technical Reports Server (NTRS)

    Kryder, Mark H.

    1993-01-01

    The Engineering Research Center in Data Storage Systems at Carnegie Mellon University in cooperation with the National Storage Industry Consortium has selected goals of achieving 10 Gbit/sq in. recording density in magnetic and magneto-optic disk recording and 1 terabyte/cubic in. magnetic tape recording technologies. This talk describes the approaches being taken and the status of research leading to these goals.

  16. Ferroelectric Pump

    NASA Technical Reports Server (NTRS)

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

    2000-01-01

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

  17. DataPlay's mobile recording technology

    NASA Astrophysics Data System (ADS)

    Bell, Bernard W., Jr.

    2002-01-01

    A small rotating memory device which utilizes optical prerecorded and writeable technology to provide a mobile recording technology solution for digital cameras, cell phones, music players, PDA's, and hybrid multipurpose devices have been developed. This solution encompasses writeable, read only, and encrypted storage media.

  18. Printed dose-recording tag based on organic complementary circuits and ferroelectric nonvolatile memories

    PubMed Central

    Nga Ng, Tse; Schwartz, David E.; Mei, Ping; Krusor, Brent; Kor, Sivkheng; Veres, Janos; Bröms, Per; Eriksson, Torbjörn; Wang, Yong; Hagel, Olle; Karlsson, Christer

    2015-01-01

    We have demonstrated a printed electronic tag that monitors time-integrated sensor signals and writes to nonvolatile memories for later readout. The tag is additively fabricated on flexible plastic foil and comprises a thermistor divider, complementary organic circuits, and two nonvolatile memory cells. With a supply voltage below 30 V, the threshold temperatures can be tuned between 0 °C and 80 °C. The time-temperature dose measurement is calibrated for minute-scale integration. The two memory bits are sequentially written in a thermometer code to provide an accumulated dose record. PMID:26307438

  19. Memory Technologies and Data Recorder Design

    NASA Technical Reports Server (NTRS)

    Strauss, Karl F

    2009-01-01

    Missions, both near Earth and deep space, are under consideration that will require data recorder capacities of such magnitude as to be unthinkable just a few years ago. Concepts requiring well over 16,000 GB of storage are being studied. To achieve this capacity via "normal means" was considered incredible as recently as 2004. This paper is presented in two parts. Part I describes the analysis of data recorder capacities for missions as far back as 35 years and provides a projection of data capacities required 20 years from now based upon missions either nearing launch, or in the planning stage. The paper presents a similar projection of memory device capacities as baselined in the ITRS - the International Technology Roadmap for Semiconductors. Using known Total Ionizing Dose tolerance going back as far as a decade, a projection of total dose tolerance is made for two prime technologies out to the year 2028.

  20. Supramolecular ferroelectrics

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

  1. Ferroelectric random access memories.

    PubMed

    Ishiwara, Hiroshi

    2012-10-01

    Ferroelectric random access memory (FeRAM) is a nonvolatile memory, in which data are stored using hysteretic P-E (polarization vs. electric field) characteristics in a ferroelectric film. In this review, history and characteristics of FeRAMs are first introduced. It is described that there are two types of FeRAMs, capacitor-type and FET-type, and that only the capacitor-type FeRAM is now commercially available. In chapter 2, properties of ferroelectric films are discussed from a viewpoint of FeRAM application, in which particular attention is paid to those of Pb(Zr,Ti)O3, SrBi2Ta2O9, and BiFeO3. Then, cell structures and operation principle of the capacitor-type FeRAMs are discussed in chapter 3. It is described that the stacked technology of ferroelectric capacitors and development of new materials with large remanent polarization are important for fabricating high-density memories. Finally, in chapter 4, the optimized gate structure in ferroelectric-gate field-effect transistors is discussed and experimental results showing excellent data retention characteristics are presented. PMID:23421123

  2. New Approach on Logic Application of Ferroelectric Random Access Memory Technology

    NASA Astrophysics Data System (ADS)

    Takayama, Masao; Koyama, Shinzo; Nozawa, Hiroshi

    2002-11-01

    In this paper, a new approach is described to solve some problems that occur when ferroelectric random access memory (FeRAM) is applied to logic circuits, particularly RSA cryptography. Application of a programmable switch device to RSA-based cryptography processing circuits was explored. RSA-based cryptography processing circuits have been designed as code conversion circuits. The capacity of the code conversion programmable AND gate and FeRAM and the translation rate have been investigated as a function of bit length. As a result, a problem of huge capacity at the practical bit length can be predicted theoretically. To solve this problem, we propose a new scheme for circuits and a new algorithm of logic operation using the binomial theorem.

  3. Ferroelectric HfO2 for Emerging Ferroelectric Semiconductor Devices

    NASA Astrophysics Data System (ADS)

    Florent, Karine

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

  4. Technology Acceptance of Electronic Medical Records by Nurses

    ERIC Educational Resources Information Center

    Stocker, Gary

    2010-01-01

    The purpose of this study was to evaluate the Technology Acceptance Model's (TAM) relevance of the intention of nurses to use electronic medical records in acute health care settings. The basic technology acceptance research of Davis (1989) was applied to the specific technology tool of electronic medical records (EMR) in a specific setting…

  5. Student Record Automating Using Desktop Computer Technologies.

    ERIC Educational Resources Information Center

    Almerico, Gina M.; Baker, Russell K.; Matassini, Norma

    Teacher education programs nationwide are required by state and federal governments to maintain comprehensive student records of all current and graduated students in their programs. A private, mid-sized university established a faculty team to analyze record-keeping procedures to comply with these government requirements. The team's mandate was…

  6. 42 CFR 425.506 - Electronic health records technology.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 42 Public Health 3 2012-10-01 2012-10-01 false Electronic health records technology. 425.506 Section 425.506 Public Health CENTERS FOR MEDICARE & MEDICAID SERVICES, DEPARTMENT OF HEALTH AND HUMAN... Standards and Reporting § 425.506 Electronic health records technology. (a) ACOs, ACO participants, and...

  7. 42 CFR 425.506 - Electronic health records technology.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 42 Public Health 3 2014-10-01 2014-10-01 false Electronic health records technology. 425.506 Section 425.506 Public Health CENTERS FOR MEDICARE & MEDICAID SERVICES, DEPARTMENT OF HEALTH AND HUMAN... Standards and Reporting § 425.506 Electronic health records technology. (a) ACOs, ACO participants, and...

  8. 42 CFR 425.506 - Electronic health records technology.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 42 Public Health 3 2013-10-01 2013-10-01 false Electronic health records technology. 425.506 Section 425.506 Public Health CENTERS FOR MEDICARE & MEDICAID SERVICES, DEPARTMENT OF HEALTH AND HUMAN... Standards and Reporting § 425.506 Electronic health records technology. (a) ACOs, ACO participants, and...

  9. Electronic Health Records: Describing Technological Stressors of Nurse Educators.

    PubMed

    Burke, Mary S; Ellis, D Michele

    2016-01-01

    The purpose of this study was to describe the technological stressors that nurse educators experienced when using electronic health records while teaching clinical courses. Survey results indicated that educators had mild to moderate technological stress when teaching the use of electronic health records to students in clinical nursing courses. PMID:26164324

  10. The United States Department of Energy Office of Industrial Technology`s Technology Benefits Recording System

    SciTech Connect

    Hughes, K.R.; Moore, N.L.

    1994-09-01

    The U.S. Department of Energy (DOE) Office of Industrial Technology`s (OIT`s) Technology Benefits Recording System (TBRS) was developed by Pacific Northwest Laboratory (PNL). The TBRS is used to organize and maintain records of the benefits accrued from the use of technologies developed with the assistance of OIT. OIT has had a sustained emphasis on technology deployment. While individual program managers have specific technology deployment goals for each of their ongoing programs, the Office has also established a separate Technology Deployment Division whose mission is to assist program managers and research and development partners commercialize technologies. As part of this effort, the Technology Deployment Division developed an energy-tracking task which has been performed by PNL since 1977. The goal of the energy-tracking task is to accurately assess the energy savings impact of OIT-developed technologies. In previous years, information on OIT-sponsored technologies existed in a variety of forms--first as a hardcopy, then electronically in several spreadsheet formats that existed in multiple software programs. The TBRS was created in 1993 for OIT and was based on information collected in all previous years from numerous industrial contacts, vendors, and plants that have installed OIT-sponsored technologies. The TBRS contains information on technologies commercialized between 1977 and the present, as well as information on emerging technologies in the late development/early commercialization stage of the technology life cycle. For each technology, details on the number of units sold and the energy saved are available on a year-by-year basis. Information regarding environmental benefits, productivity and competitiveness benefits, or impact that the technology may have had on employment is also available.

  11. Integrating Records Management (RM) and Information Technology (IT)

    SciTech Connect

    NUSBAUM,ANNA W.; CUSIMANO,LINDA J.

    2000-03-02

    Records Managers are continually exploring ways to integrate their services with those offered by Information Technology-related professions to capitalize on the advantages of providing customers a total solution to managing their records and information. In this day and age, where technology abounds, there often exists a fear on the part of records management that this integration will result in a loss of identity and the focus of one's own mission - a fear that records management may become subordinated to the fast-paced technology fields. They need to remember there is strength in numbers and it benefits RM, IT, and the customer when they can bring together the unique offerings each possess to reach synergy for the benefit of all the corporations. Records Managers, need to continually strive to move ''outside the records management box'', network, expand their knowledge, and influence the IT disciplines to incorporate the concept of ''management'' into their customer solutions.

  12. Perpendicular recording technology on rigid disks

    NASA Astrophysics Data System (ADS)

    Suenaga, T.; Takeno, H.

    1994-06-01

    We have studied a flying single-pole head and CoCrTa/NiFe double magnetic recording. The media consisted of electro-plated Ni-Fe underlayer and sputtered Co-Cr-Ta recording layer. The 'pancake' type head formed four-layered 60 turns, the pole width is 7 μm, and the flying height is 0.075 μm. We have confirmed that a combination of such medium and head is capable of achieving 300 Mbits/in 2.

  13. 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.

  14. Electronic Record Systems and Individual Privacy. Federal Government Information Technology.

    ERIC Educational Resources Information Center

    Congress of the U.S., Washington, DC. Office of Technology Assessment.

    This report considers the privacy issues raised by the growth of the new technology being applied to the personal information collected, maintained, and disseminated by the Federal Government. Four major areas are addressed: (1) technological developments relevant to government record systems; (2) current and prospective Federal agency use of…

  15. Ferroelectric memory element based on thin film field effect transistor

    NASA Astrophysics Data System (ADS)

    Poghosyan, A. R.; Aghamalyan, N. R.; Elbakyan, E. Y.; Guo, R.; Hovsepyan, R. K.

    2013-09-01

    We report the preparation and investigation of ferroelectric field effect transistors (FET) using ZnO:Li films with high field mobility of the charge carriers as a FET channel and as a ferroelectric active element simultaneously. The possibility for using of ferroelectric FET based on the ZnO:Li films in the ZnO:Li/LaB6 heterostructure as a bi-stable memory element for information recording is shown. The proposed ferroelectric memory structure does not manifest a fatigue after multiple readout of once recorded information.

  16. 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.

  17. Polarization of ferroelectric films through electrolyte

    NASA Astrophysics Data System (ADS)

    Toss, Henrik; Sani, Negar; Fabiano, Simone; Simon, Daniel T.; Forchheimer, Robert; Berggren, Magnus

    2016-03-01

    A simplified model is developed to understand the field and potential distribution through devices based on a ferroelectric film in direct contact with an electrolyte. Devices based on the ferroelectric polymer polyvinylidenefluoride-trifluoroethylene (PVDF-TrFE) were produced—in metal-ferroelectric-metal, metal-ferroelectric-dielectric-metal, and metal-ferroelectric-electrolyte-metal architectures—and used to test the model, and simulations based on the model and these fabricated devices were performed. From these simulations we find indication of progressive polarization of the films. Furthermore, the model implies that there is a relation between the separation of charge within the devices and the observed open circuit voltage. This relation is confirmed experimentally. The ability to polarize ferroelectric polymer films through aqueous electrolytes, combined with the strong correlation between the properties of the electrolyte double layer and the device potential, opens the door to a variety of new applications for ferroelectric technologies, e.g. regulation of cell culture growth and release, steering molecular self-assembly, or other large area applications requiring aqueous environments.

  18. Polarization of ferroelectric films through electrolyte.

    PubMed

    Toss, Henrik; Sani, Negar; Fabiano, Simone; Simon, Daniel T; Forchheimer, Robert; Berggren, Magnus

    2016-03-16

    A simplified model is developed to understand the field and potential distribution through devices based on a ferroelectric film in direct contact with an electrolyte. Devices based on the ferroelectric polymer polyvinylidenefluoride-trifluoroethylene (PVDF-TrFE) were produced--in metal-ferroelectric-metal, metal-ferroelectric-dielectric-metal, and metal-ferroelectric-electrolyte-metal architectures--and used to test the model, and simulations based on the model and these fabricated devices were performed. From these simulations we find indication of progressive polarization of the films. Furthermore, the model implies that there is a relation between the separation of charge within the devices and the observed open circuit voltage. This relation is confirmed experimentally. The ability to polarize ferroelectric polymer films through aqueous electrolytes, combined with the strong correlation between the properties of the electrolyte double layer and the device potential, opens the door to a variety of new applications for ferroelectric technologies, e.g. regulation of cell culture growth and release, steering molecular self-assembly, or other large area applications requiring aqueous environments. PMID:26885704

  19. Fast Switching Ferroelectric Materials for Accelerator Applications

    NASA Astrophysics Data System (ADS)

    Kanareykin, A.; Nenasheva, E.; Yakovlev, V.; Dedyk, A.; Karmanenko, S.; Kozyrev, A.; Osadchy, V.; Kosmin, D.; Schoessow, P.; Semenov, A.

    2006-11-01

    Fast switching (<10 nsec) measurement results on the recently developed BST(M) (barium strontium titanium oxide composition with magnesium-based additions) ferroelectric materials are presented. These materials can be used as the basis for new advanced technology components suitable for high-gradient accelerators. A ferroelectric ceramic has an electric field-dependent dielectric permittivity that can be altered by applying a bias voltage. Ferroelectric materials offer significant benefits for linear collider applications, in particular, for switching and control elements where a very short response time of <10 nsec is required. The measurement results presented here show that the new BST(M) ceramic exhibits a high tunability factor: a bias field of 40-50 kV/cm reduces the permittivity by a factor of 1.3-1.5. The recently developed technology of gold biasing contact deposition on large diameter (110 cm) thin wall ferroelectric rings allowed ˜few nsec switching times in witness sample experiments. The ferroelectric rings can be used at high pulsed power (tens of megawatts) for X-band components as well as at high average power in the range of a few kilowatts for the L-band phase-shifter, under development for optimization of the ILC rf coupling. Accelerator applications include fast active X-band and Ka-band high-power ferroelectric switches, high-power X-band and L-band phase shifters, and tunable dielectric-loaded accelerating structures.

  20. Review of past, present, and future of recording technology

    NASA Astrophysics Data System (ADS)

    Al-Jibouri, Abdul-Rahman

    2003-03-01

    The revolution of information storage and recording has been advanced significantly over the past two decades. Since the development of computers in early 1950s by IBM, the data (information) was stored on magnetic disc by inducing magnetic flux to define the pit direction. The first disc was developed by IBM with diameter of 25inch to store around 10 kByte. After four decades, the disc drive has become more advanced by reducing the drive size, increasing ariel density and cost reduction. The introduction of new computer operating systems and the Internet resulted in the need to develop high ariel density in the 1990s. Therefore, the disc drive manufacturers were pushed harder to develop new technologies at low cost to survive the competitive market. The disc drives, which are based on media (where the data/information is stored) and the head (which will write and read data/information). The head and disc are separated and with the current technology the spacing between the disc and head is about 40nm. A new technology based on magnetic recording was developed to serve the audio market. This technology is called magnetic type, it is similar to the disc drive, but the media is based on tape rather than rigid disc. Another difference being the head and media are in direct contact. Magnetic tape was developed for audio application and a few years later this technology was extended to allow and accept another technology, called video. This allows consumers to record and view movies in their home. The magnetic tape also used the computer industries for back up data. Magnetic tape is still used in computers and has advanced further over the past decade, companies like Quantum Corp has developed digital linear tape.

  1. Molecule-displacive ferroelectricity in organic supramolecular solids

    PubMed Central

    Ye, Heng-Yun; Zhang, Yi; Noro, Shin-ichiro; Kubo, Kazuya; Yoshitake, Masashi; Liu, Zun-Qi; Cai, Hong-Ling; Fu, Da-Wei; Yoshikawa, Hirofumi; Awaga, Kunio; Xiong, Ren-Gen; Nakamura, Takayoshi

    2013-01-01

    Ferroelectricity is essential to many forms of current technology, ranging from sensors and actuators to optical or memory devices. In this circumstance, organic ferroelectrics are of particular importance because of their potential application in tomorrow's organic devices, and several pure organic ferroelectrics have been recently developed. However, some problems, such as current leakage and/or low working frequencies, make their application prospects especially for ferroelectric memory (FeRAM) not clear. Here, we describe the molecule-displacive ferroelectricity of supramolecular adducts of tartaric acid and 1,4-diazabicyclo[2.2.2]octane N,N′-dioxide. The adducts show large spontaneous polarization, high rectangularity of the ferroelectric hysteresis loops even at high operation frequency (10 kHz), and high performance in polarization switching up to 1 × 106 times without showing fatigue. It opens great perspectives in terms of applications, especially in organic FeRAM. PMID:23873392

  2. Molecule-displacive ferroelectricity in organic supramolecular solids

    NASA Astrophysics Data System (ADS)

    Ye, Heng-Yun; Zhang, Yi; Noro, Shin-Ichiro; Kubo, Kazuya; Yoshitake, Masashi; Liu, Zun-Qi; Cai, Hong-Ling; Fu, Da-Wei; Yoshikawa, Hirofumi; Awaga, Kunio; Xiong, Ren-Gen; Nakamura, Takayoshi

    2013-07-01

    Ferroelectricity is essential to many forms of current technology, ranging from sensors and actuators to optical or memory devices. In this circumstance, organic ferroelectrics are of particular importance because of their potential application in tomorrow's organic devices, and several pure organic ferroelectrics have been recently developed. However, some problems, such as current leakage and/or low working frequencies, make their application prospects especially for ferroelectric memory (FeRAM) not clear. Here, we describe the molecule-displacive ferroelectricity of supramolecular adducts of tartaric acid and 1,4-diazabicyclo[2.2.2]octane N,N'-dioxide. The adducts show large spontaneous polarization, high rectangularity of the ferroelectric hysteresis loops even at high operation frequency (10 kHz), and high performance in polarization switching up to 1 × 106 times without showing fatigue. It opens great perspectives in terms of applications, especially in organic FeRAM.

  3. Electron emission from ferroelectrics

    NASA Astrophysics Data System (ADS)

    Zhang, Weiming

    Ferroelectric emission (FE) was discovered at CERN in 1988. However, a diverse array of results and explanations concerning FE have appeared. This dissertation focused on understanding the influence of material properties and external parameters on this complex process. The sample preparation, pulse generator and other experimental techniques are described. Plasma emission (PE), FE and mixed PE and FE were observed and described. The field enhancement at the electrode-dielectric-vacuum triple point was suggested to be the basis for PE. An apparent delay time, instability, visible light generation and strong electrode erosion are features of PE. Comparatively, FE does not require an extraction field, exhibits no apparent delay time and a relatively stable emission, and generates either no or a very weak light signal. A direct relationship between the switching current and emission current exists for the FE. Different FE characteristics of antiferroelectric PLZT 2/95/5, "normal" ferroelectric PLZT 8/65/35 and nonferroelectric PLZT 15/65/35 were described. The strong relationship between the emission and switching current was demonstrated. Repeatable emission is exhibited by 2/95/5, which can also be pulsed at high frequency due to its fast antiferroelectric <=> ferroelectric phase transition. The strong degradation of FE from 8/65/35 was attributed to decrease in the remanent polarization. While no emission signal was detected from 15/65/35, which can be interpreted as an additional evidence that electron emission from the above two PLZT was indeed FE process. Based on the field and domain switching distribution model, sample geometry effect on FE was predicted, and verified using the results from different groups. Electron emission energy distribution of PLZT 8/65/35 showed a very narrow energy distribution (FWHM ≈ 10 eV to 20 eV), and the emission energy was on the order of the applied pulse potential. The possible application of FE for emissive flat panel

  4. Science and technology of thin films and interfacial layers in ferroelectric and high-dielectric constant heterostructures and application to devices.

    SciTech Connect

    Auciello, O.; Materials Science Division

    2006-01-01

    The fabrication of the next generation of complex oxide thin film-based micro and nanoscale devices, such as, for example, low and high density nonvolatile ferroelectric random access memories (FeRAMS), high-dielectric constant (K) high-frequency devices, and the next generation of complimentary metal oxide semiconductor (CMOS) nanoscale devices based on high-K dielectrics, require understanding and control of film growth and interface processes as well as development of materials integration strategies with atomic scale control. In recent years, we developed and applied a unique combination of integrated film synthesis/in situ characterization and ex situ analytical techniques capable of providing information about thin film surface and interface processes at the atomic scale as required for the development of the devices mentioned above. These techniques are also useful for establishing composition-microstructure-property relationships critical for the integration of oxide thin films with semiconductor device platforms for the development of a whole new generation of micro and nanodevices based on film technologies beyond semiconductors and specifically silicon. Our recent work has been focused on developing diffusion barrier layers and heterostructured bottom electrodes that play a critical role in high-density FeRAM integration. We demonstrated that TiAl layers can be used as a material with a double diffusion barrier/bottom electrode functionality for integration of ferroelectric capacitors CMOS devices for fabrication of FeRAMs. We also demonstrated that control of interfaces is critical to the integration of high-K dielectric films with appropriate substrates for the fabrication of high-performance high-frequency devices, and here again a diffusion barrier such as the TiAl layer developed by our group is critical for such integration. These studies revealed that when properly oxidized, nanoscale thick amorphous Ti-Al-O layers exhibit properties that make

  5. A Ferroelectric Oxide Made Directly on Silicon

    SciTech Connect

    Warusawithana, M.; Cen, C; Sleasman, C; Woicik, J; Li, Y; Fitting Kourkoutis, L; Klug, J; Li, H; Ryan, P; et. al.

    2009-01-01

    Metal oxide semiconductor field-effect transistors, formed using silicon dioxide and silicon, have undergone four decades of staggering technological advancement. With fundamental limits to this technology close at hand, alternatives to silicon dioxide are being pursued to enable new functionality and device architectures. We achieved ferroelectric functionality in intimate contact with silicon by growing coherently strained strontium titanate (SrTiO{sub 3}) films via oxide molecular beam epitaxy in direct contact with silicon, with no interfacial silicon dioxide. We observed ferroelectricity in these ultrathin SrTiO{sub 3} layers by means of piezoresponse force microscopy. Stable ferroelectric nanodomains created in SrTiO{sub 3} were observed at temperatures as high as 400 kelvin.

  6. 36 CFR 1236.14 - What must agencies do to protect records against technological obsolescence?

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... protect records against technological obsolescence? 1236.14 Section 1236.14 Parks, Forests, and Public... Systems § 1236.14 What must agencies do to protect records against technological obsolescence? Agencies... in which the records are originally created or captured. To successfully protect records...

  7. 36 CFR 1236.14 - What must agencies do to protect records against technological obsolescence?

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... protect records against technological obsolescence? 1236.14 Section 1236.14 Parks, Forests, and Public... Systems § 1236.14 What must agencies do to protect records against technological obsolescence? Agencies... in which the records are originally created or captured. To successfully protect records...

  8. 36 CFR 1236.14 - What must agencies do to protect records against technological obsolescence?

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... protect records against technological obsolescence? 1236.14 Section 1236.14 Parks, Forests, and Public... Systems § 1236.14 What must agencies do to protect records against technological obsolescence? Agencies... in which the records are originally created or captured. To successfully protect records...

  9. 36 CFR 1236.14 - What must agencies do to protect records against technological obsolescence?

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... protect records against technological obsolescence? 1236.14 Section 1236.14 Parks, Forests, and Public... Systems § 1236.14 What must agencies do to protect records against technological obsolescence? Agencies... in which the records are originally created or captured. To successfully protect records...

  10. 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

  11. Emission from ferroelectric cathodes

    SciTech Connect

    Sampayan, S.E.; Caporaso, G.J.; Holmes, C.L.; Lauer, E.J.; Prosnitz, D.; Trimble, D.O.; Westenskow, G.A.

    1993-05-17

    We have recently initiated an investigation of electron emission from ferroelectric cathodes. Our experimental apparatus consisted of an electron diode and a 250 kV, 12 ohm, 70 ns pulsed high voltage power source. A planar triode modulator driven by a synthesized waveform generator initiates the polarization inversion and allows inversion pulse tailoring. The pulsed high voltage power source is capable of delivering two high voltage pulses within 50 ns of each other and is capable of operating at a sustained repetition rate of 5 Hz. Our initial measurements indicate that emission current densities above the Child-Langmuir Space Charge Limit are possible. We explain this effect to be based on a non-zero initial energy of the emitted electrons. We also determined that this effect is strongly coupled to relative timing between the inversion pulse and application of the main anode-cathode pulse. We also have initiated brightness measurements of the emitted beam. As in our previous measurements at this Laboratory, we performed the measurement using a pepper pot technique. Beam-let profiles are recorded with a fast phosphor and gated cameras. We describe our apparatus and preliminary measurements.

  12. Magnetic Recording Media Technology for the Tb/in2 Era"

    ScienceCinema

    Bertero, Gerardo [Western Digital

    2010-09-01

    Magnetic recording has been the technology of choice of massive storage of information. The hard-disk drive industry has recently undergone a major technological transition from longitudinal magnetic recording (LMR) to perpendicular magnetic recording (PMR). However, convention perpendicular recording can only support a few new product generations before facing insurmountable physical limits. In order to support sustained recording areal density growth, new technological paradigms, such as energy-assisted recording and bit-patterined media recording are being contemplated and planned. In this talk, we will briefly discuss the LMR-to-PMR transition, the extendibility of current PMR recording, and the nature and merits of new enabling technologies. We will also discuss a technology roadmap toward recording densities approaching 10 Tv/in2, approximately 40 times higher than in current disk drives.

  13. Magnetic Recording Media Technology for the Tb/in2 Era"

    SciTech Connect

    Bertero, Gerardo

    2010-04-07

    Magnetic recording has been the technology of choice of massive storage of information. The hard-disk drive industry has recently undergone a major technological transition from longitudinal magnetic recording (LMR) to perpendicular magnetic recording (PMR). However, convention perpendicular recording can only support a few new product generations before facing insurmountable physical limits. In order to support sustained recording areal density growth, new technological paradigms, such as energy-assisted recording and bit-patterined media recording are being contemplated and planned. In this talk, we will briefly discuss the LMR-to-PMR transition, the extendibility of current PMR recording, and the nature and merits of new enabling technologies. We will also discuss a technology roadmap toward recording densities approaching 10 Tv/in2, approximately 40 times higher than in current disk drives.

  14. Magnetic Recording Media Technology for the Tb/In2 Era

    SciTech Connect

    Bertero, Gerardo

    2010-04-07

    Magnetic recording has been the technology of choice of massive storage of information. The hard-disk drive industry has recently undergone a major technological transition from longitudinal magnetic recording (LMR) to perpendicular magnetic recording (PMR). However, convention perpendicular recording can only support a few new product generations before facing insurmountable physical limits. In order to support sustained recording areal density growth, new technological paradigms, such as energy-assisted recording and bit-patterined media recording are being contemplated and planned. In this talk, we will briefly discuss the LMR-to-PMR transition, the extendibility of current PMR recording, and the nature and merits of new enabling technologies. We will also discuss a technology roadmap toward recording densities approaching 10 Tv/in2, approximately 40 times higher than in current disk drives.

  15. Ferroelectric plasma thruster for microspacecraft propulsion

    SciTech Connect

    Kemp, Mark A.; Kovaleski, Scott D.

    2006-12-01

    This paper presents a technology in microthruster design: the ferroelectric plasma thruster (FEPT). The FEPT utilizes an applied rf electric field to create plasma on the surface of a ferroelectric dielectric. Acceleration of ions from this plasma provides thrust. Advantages of the FEPT include emission of both electrons and ions leading to self-neutralization, creation of plasma, and acceleration of ions with a single power supply, and application of thrust in a short amount of time. We present the concept of the thruster, operational physics, as well as experimental results demonstrating plasma creation and ion acceleration. These results along with plasma spectroscopy allow us to calculate thruster parameters.

  16. The origin of ferroelectricity in magnetoelectric YMnO3.

    PubMed

    Van Aken, Bas B; Palstra, Thomas T M; Filippetti, Alessio; Spaldin, Nicola A

    2004-03-01

    Understanding the ferroelectrocity in magnetic ferroelectric oxides is of both fundamental and technological importance. Here, we identify the nature of the ferroelectric phase transition in the hexagonal manganite, YMnO(3), using a combination of single-crystal X-ray diffraction, thorough structure analysis and first-principles density-functional calculations. The ferroelectric phase is characterized by a buckling of the layered MnO(5) polyhedra, accompanied by displacements of the Y ions, which lead to a net electric polarization. Our calculations show that the mechanism is driven entirely by electrostatic and size effects, rather than the usual changes in chemical bonding associated with ferroelectric phase transitions in perovskite oxides. As a result, the usual indicators of structural instability, such as anomalies in Born effective charges on the active ions, do not hold. In contrast to the chemically stabilized ferroelectrics, this mechanism for ferroelectricity permits the coexistence of magnetism and ferroelectricity, and so suggests an avenue for designing novel magnetic ferroelectrics. PMID:14991018

  17. Super Stable Ferroelectrics with High Curie Point

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

  18. Super Stable Ferroelectrics with High Curie Point

    PubMed Central

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

    2016-01-01

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

  19. Super Stable Ferroelectrics with High Curie Point.

    PubMed

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

    2016-01-01

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

  20. Ferroelectricity in spiral magnets.

    PubMed

    Mostovoy, Maxim

    2006-02-17

    It was recently observed that the ferroelectrics showing the strongest sensitivity to an applied magnetic field are spiral magnets. We present a phenomenological theory of inhomogeneous ferroelectric magnets, which describes their thermodynamics and magnetic field behavior, e.g., dielectric susceptibility anomalies at magnetic transitions and sudden flops of electric polarization in an applied magnetic field. We show that electric polarization can also be induced at domain walls and that magnetic vortices carry electric charge. PMID:16606047

  1. Determining the influence of ferroelectric polarization on electrical characteristics in organic ferroelectric field-effect transistors

    NASA Astrophysics Data System (ADS)

    Fu, Zong-Yuan; Zhang, Jian-Chi; Hu, Jing-Hang; Jiang, Yu-Long; Ding, Shi-Jin; Zhu, Guo-Dong

    2015-05-01

    Organic ferroelectric field-effect transistors (OFeFETs) are regarded as a promising technology for low-cost flexible memories. However, the electrical instability is still a critical obstacle, which limits the commercialization process. Based on already established models for polarization in ferroelectrics and charge transport in OFeFETs, simulation work is performed to determine the influence of polarization fatigue and ferroelectric switching transient on electrical characteristics in OFeFETs. The polarization fatigue results in the decrease of the on-state drain current and the memory window width and thus degrades the memory performance. The output measurements during the ferroelectric switching process show a hysteresis due to the instable polarization. In the on/off measurements, a large writing/erasing pulse frequency weakens the polarization modulation and thus results in a small separation between on- and off-state drain currents. According to the electrical properties of the ferroelectric layer, suggestions are given to obtain optimal electrical characterization for OFeFETs. Project supported by the National Key Technologies R&D Program, China (Grant No. 2009ZX02302-002), the National Natural Science Foundation of China (Grant Nos. 61376108, 61076076, and 61076068), NSAF, China (Grant No. U1430106), the Science and Technology Commission of Shanghai Municipality, China (Grant No. 13NM1400600), and Zhuo Xue Plan in Fudan University, China.

  2. Losses in Ferroelectric Materials

    PubMed Central

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

    2015-01-01

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

  3. Flat panel ferroelectric electron emission display system

    DOEpatents

    Sampayan, S.E.; Orvis, W.J.; Caporaso, G.J.; Wieskamp, T.F.

    1996-04-16

    A device is disclosed which can produce a bright, raster scanned or non-raster scanned image from a flat panel. Unlike many flat panel technologies, this device does not require ambient light or auxiliary illumination for viewing the image. Rather, this device relies on electrons emitted from a ferroelectric emitter impinging on a phosphor. This device takes advantage of a new electron emitter technology which emits electrons with significant kinetic energy and beam current density. 6 figs.

  4. Flat panel ferroelectric electron emission display system

    DOEpatents

    Sampayan, Stephen E.; Orvis, William J.; Caporaso, George J.; Wieskamp, Ted F.

    1996-01-01

    A device which can produce a bright, raster scanned or non-raster scanned image from a flat panel. Unlike many flat panel technologies, this device does not require ambient light or auxiliary illumination for viewing the image. Rather, this device relies on electrons emitted from a ferroelectric emitter impinging on a phosphor. This device takes advantage of a new electron emitter technology which emits electrons with significant kinetic energy and beam current density.

  5. Ferroelectric optical image comparator

    SciTech Connect

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

    1989-08-30

    The property of ferroelectric ceramics such as lead lanthanum zirconate titanate (PLZT) to store information has been known for many years. This relates to the property of ferroelectric ceramic materials to become permanently polarized when an electric signal is applied to the material. A ferroelectric optical image comparator has a lead lanthanum zirconate titanate thin-film device which is constructed with a semi-transparent or transparent conductive first electrode on one side of the thin film, a conductive metal second electrode on the other side of the thin film, and the second electrode is in contact with a nonconducting substrate. A photoinduced current in the device represents the dot product between a stored image and an image projected onto the first electrode. One-dimensional autocorrelations are performed by measuring this current while displacing the projected image. 5 figs.

  6. Applications of modern ferroelectrics.

    PubMed

    Scott, J F

    2007-02-16

    Long viewed as a topic in classical physics, ferroelectricity can be described by a quantum mechanical ab initio theory. Thin-film nanoscale device structures integrated onto Si chips have made inroads into the semiconductor industry. Recent prototype applications include ultrafast switching, cheap room-temperature magnetic-field detectors, piezoelectric nanotubes for microfluidic systems, electrocaloric coolers for computers, phased-array radar, and three-dimensional trenched capacitors for dynamic random access memories. Terabit-per-square-inch ferroelectric arrays of lead zirconate titanate have been reported on Pt nanowire interconnects and nanorings with 5-nanometer diameters. Finally, electron emission from ferroelectrics yields cheap, high-power microwave devices and miniature x-ray and neutron sources. PMID:17303745

  7. Frequency Dependent Microwave Impedance Microscopy of Ferroelectric Domain Walls

    NASA Astrophysics Data System (ADS)

    Johnston, Scott; Shen, Zhi-Xun

    ABO3 ferroelectrics are known to exhibit domain wall conductivity which is of great fundamental and technological interest. Microwave Impedance Microscopy is a near field measurement technique which allows local, non-contact measurement of AC conductivity and permittivity. In this work, Microwave Impedance Microscopy over a wide frequency range is used to probe the electrical properties of domain walls in ABO3 ferroelectrics. An unexpected, strong frequency dependence in the microwave dissipation near domain walls is observed.

  8. Symmetry breaking in molecular ferroelectrics.

    PubMed

    Shi, Ping-Ping; Tang, Yuan-Yuan; Li, Peng-Fei; Liao, Wei-Qiang; Wang, Zhong-Xia; Ye, Qiong; Xiong, Ren-Gen

    2016-07-11

    Ferroelectrics are inseparable from symmetry breaking. Accompanying the paraelectric-to-ferroelectric phase transition, the paraelectric phase adopting one of the 32 crystallographic point groups is broken into subgroups belonging to one of the 10 ferroelectric point groups, i.e. C1, C2, C1h, C2v, C4, C4v, C3, C3v, C6 and C6v. The symmetry breaking is captured by the order parameter known as spontaneous polarization, whose switching under an external electric field results in a typical ferroelectric hysteresis loop. In addition, the responses of spontaneous polarization to other external excitations are related to a number of physical effects such as second-harmonic generation, piezoelectricity, pyroelectricity and dielectric properties. Based on these, this review summarizes recent developments in molecular ferroelectrics since 2011 and focuses on the relationship between symmetry breaking and ferroelectricity, offering ideas for exploring high-performance molecular ferroelectrics. PMID:27051889

  9. Local polarization dynamics in ferroelectric materials

    NASA Astrophysics Data System (ADS)

    Kalinin, Sergei V.; Morozovska, Anna N.; Qing Chen, Long; Rodriguez, Brian J.

    2010-05-01

    Ferroelectrics and multiferroics have recently emerged as perspective materials for information technology and data storage applications. The combination of extremely narrow domain wall width and the capability to manipulate polarization by electric field opens the pathway toward ultrahigh (>10 TBit inch-2) storage densities and small (sub-10 nm) feature sizes. The coupling between polarization and chemical and transport properties enables applications in ferroelectric lithography and electroresistive devices. The progress in these applications, as well as fundamental studies of polarization dynamics and the role of defects and disorder on domain nucleation and wall motion, requires the capability to probe these effects on the nanometer scale. In this review, we summarize the recent progress in applications of piezoresponse force microscopy (PFM) for imaging, manipulation and spectroscopy of ferroelectric switching processes. We briefly introduce the principles and relevant instrumental aspects of PFM, with special emphasis on resolution and information limits. The local imaging studies of domain dynamics, including local switching and relaxation accessed through imaging experiments and spectroscopic studies of polarization switching, are discussed in detail. Finally, we review the recent progress on understanding and exploiting photochemical processes on ferroelectric surfaces, the role of surface adsorbates, and imaging and switching in liquids. Beyond classical applications, probing local bias-induced transition dynamics by PFM opens the pathway to studies of the influence of a single defect on electrochemical and solid state processes, thus providing model systems for batteries, fuel cells and supercapacitor applications.

  10. Local Polarization Dynamics in Ferroelectric Materials

    SciTech Connect

    Kalinin, Sergei V; Morozovska, A. N.; Chen, L. Q.; Rodriguez, Brian J

    2010-01-01

    Ferroelectrics and multiferroics have recently emerged as perspective materials for information technology and data storage applications. The combination of extremely narrow domain wall width and the capability to manipulate polarization by electric field opens the pathway towards ultrahigh (>10 TBit/in2) storage densities and small (sub-10 nm) feature sizes. The coupling between polarization and chemical and transport properties enables applications in ferroelectric lithography and electroresistive devices. The progress in these applications, as well as fundamental studies of polarization dynamics and the role of defects and disorder on domain nucleation and wall motion, requires the capability to probe these effects on the nanometer scale. In this review, we summarize recent progress in applications of Piezoresponse Force Microscopy (PFM) for imaging, manipulation, and spectroscopy of ferroelectric switching processes. We briefly introduce the principles and relevant instrumental aspects of PFM, with special emphasis on resolution and information limits. The local imaging studies of domain dynamics, including local switching and relaxation accessed through imaging experiments, and spectroscopic studies of polarization switching, are discussed in detail. Finally, we briefly review the recent progress on photochemical processes on ferroelectric surfaces, the role of surface adsorbates, and imaging and switching in liquids. Beyond classical applications, probing local bias-induced transition dynamics by PFM opens the pathway to studies of the influence of a single defect on electrochemical and solid state processes, thus providing model systems for batteries, fuel cells, and supercapacitor applications.

  11. 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.

  12. 75 FR 1446 - Rate of Payment for Medical Records Received Through Health Information Technology (IT) Necessary...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-01-11

    ... ADMINISTRATION Rate of Payment for Medical Records Received Through Health Information Technology (IT) Necessary... national rate of Federal payment for medical records received through health IT. SUMMARY: We have set $15... records through health IT in response to a request. We will pay the uniform national rate to a...

  13. Technologies for Text: Storage and Retrieval of Linguistic Records.

    ERIC Educational Resources Information Center

    Friedman, Edward A.

    This learning module, one in a series developed in a project on "Technology and the Liberal Arts," is an introduction to emerging technological developments for information storage. A historical sketch is provided of text technologies leading up to widespread use of the typewriter toward the end of the 19th century. This is followed by an analysis…

  14. Domains in Ferroelectric Nanostructures

    NASA Astrophysics Data System (ADS)

    Gregg, Marty

    2010-03-01

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

  15. Discovery of stable skyrmionic state in ferroelectric nanocomposites.

    PubMed

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

    2015-01-01

    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. PMID:26436432

  16. Discovery of stable skyrmionic state in ferroelectric nanocomposites

    PubMed Central

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

    2015-01-01

    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. PMID:26436432

  17. 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.

  18. Using Tablet Technology and Recording Software to Enhance Pedagogy

    ERIC Educational Resources Information Center

    Radosevich, David J.; Kahn, Patricia

    2006-01-01

    A key benefit of information technology in educational settings is its ability to support engaged, interactive learning experiences consistent with constructivist principles. At the same time, educators are continually searching for low threshold technologies that integrate well in traditional learning environments, that do not require a high…

  19. Health information technology and electronic health records in neurologic practice.

    PubMed

    Esper, Gregory J; Drogan, Oksana; Henderson, William S; Becker, Amanda; Avitzur, Orly; Hier, Daniel B

    2010-05-01

    The tipping point for electronic health records (EHR) has been reached and universal adoption in the United States is now inevitable. Neurologists will want to choose their electronic health record prudently. Careful selection, contracting, planning, and training are essential to successful implementation. Neurologists need to examine their workflow carefully and make adjustments to ensure that efficiency is increased. Neurologists will want to achieve a significant return on investment and qualify for all applicable financial incentives from payers, including CMS. EHRs are not just record-keeping tools but play an important role in quality improvement, evidence-based medicine, pay for performance, patient education, bio-surveillance, data warehousing, and data exchange. PMID:20202501

  20. Promoting Independence through Assistive Technology: Evaluating Audio Recorders to Support Grocery Shopping

    ERIC Educational Resources Information Center

    Bouck, Emily C.; Satsangi, Rajiv; Bartlett, Whitney; Weng, Pei-Lin

    2012-01-01

    In light of a positive research base regarding technology-based self-operating prompting systems (e.g., iPods), yet a concern about the sustainability of such technologies after a research project is completed, this study sought to explore the effectiveness and efficiency of an audio recorder, a low-cost, more commonly accessible technology to…

  1. 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

  2. Digital Recording Technology in the Writing Classroom: Sampling as Citing

    ERIC Educational Resources Information Center

    Duffy, W. Keith

    2004-01-01

    For the last few years, the author has been implementing a pedagogy that infuses musical composition--specifically the recording of electronic music--into his first-year composition courses. The author and his students have been quite surprised by the theoretical and practical connections that exist between the production of popular electronic…

  3. Isotopic, Ecological and Technological Investigations of the Land Snail Record

    ERIC Educational Resources Information Center

    Faber, Meredith L.

    2012-01-01

    In the ever-evolving landscape of the natural world, change is the only constant. Investigating how life accommodates that change can provide valuable insights into the biological, ecological and geological history of our planet. The fossil record is replete with examples of organisms which failed to survive in the wake of ongoing environmental…

  4. 78 FR 17722 - Technological Upgrades to Registration and Recordation Functions

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-03-22

    ... a comprehensive business process reengineering initiative intended to update the Office's technology platform and improve operational efficiency. With the assistance of outside consultants and business... to an electronic system, which included the development of related new business processes and...

  5. Measuring the evolution of the drivers of technological innovation in the patent record.

    PubMed

    Buchanan, Andrew; Packard, Norman H; Bedau, Mark A

    2011-01-01

    We argue that technology changes over time by an evolutionary process that is similar in important respects to biological evolution. The process is adaptive in the sense that technologies are selected because of their specific adaptive value and not at random, but this adaptive evolutionary process differs from the Darwinian process of random variation followed by natural selection. We find evidence for the adaptive evolution of technology in the US patent record, specifically, the public bibliographic information of all utility patents issued in the United States from 1976 through 2010. Patents record certain innovations in the evolution of technology. The 1976-2010 patent record is huge, containing almost four million patents. We use a patent's incoming citations to measure its impact on subsequent patented innovations. Weighting innovative impact by the dissimilarity between parent and child technologies reveals that many of the most fecund inventions are door-opening technologies that spawn innovations in widely diverse categories. PMID:21370957

  6. Super-crystals in composite ferroelectrics

    PubMed Central

    Pierangeli, D.; Ferraro, M.; Di Mei, F.; Di Domenico, G.; de Oliveira, C. E. M.; Agranat, A. J.; DelRe, E.

    2016-01-01

    As atoms and molecules condense to form solids, a crystalline state can emerge with its highly ordered geometry and subnanometric lattice constant. In some physical systems, such as ferroelectric perovskites, a perfect crystalline structure forms even when the condensing substances are non-stoichiometric. The resulting solids have compositional disorder and complex macroscopic properties, such as giant susceptibilities and non-ergodicity. Here, we observe the spontaneous formation of a cubic structure in composite ferroelectric potassium–lithium–tantalate–niobate with micrometric lattice constant, 104 times larger than that of the underlying perovskite lattice. The 3D effect is observed in specifically designed samples in which the substitutional mixture varies periodically along one specific crystal axis. Laser propagation indicates a coherent polarization super-crystal that produces an optical X-ray diffractometry, an ordered mesoscopic state of matter with important implications for critical phenomena and applications in miniaturized 3D optical technologies. PMID:26907725

  7. Super-crystals in composite ferroelectrics.

    PubMed

    Pierangeli, D; Ferraro, M; Di Mei, F; Di Domenico, G; de Oliveira, C E M; Agranat, A J; DelRe, E

    2016-01-01

    As atoms and molecules condense to form solids, a crystalline state can emerge with its highly ordered geometry and subnanometric lattice constant. In some physical systems, such as ferroelectric perovskites, a perfect crystalline structure forms even when the condensing substances are non-stoichiometric. The resulting solids have compositional disorder and complex macroscopic properties, such as giant susceptibilities and non-ergodicity. Here, we observe the spontaneous formation of a cubic structure in composite ferroelectric potassium-lithium-tantalate-niobate with micrometric lattice constant, 10(4) times larger than that of the underlying perovskite lattice. The 3D effect is observed in specifically designed samples in which the substitutional mixture varies periodically along one specific crystal axis. Laser propagation indicates a coherent polarization super-crystal that produces an optical X-ray diffractometry, an ordered mesoscopic state of matter with important implications for critical phenomena and applications in miniaturized 3D optical technologies. PMID:26907725

  8. Super-crystals in composite ferroelectrics

    NASA Astrophysics Data System (ADS)

    Pierangeli, D.; Ferraro, M.; di Mei, F.; di Domenico, G.; de Oliveira, C. E. M.; Agranat, A. J.; Delre, E.

    2016-02-01

    As atoms and molecules condense to form solids, a crystalline state can emerge with its highly ordered geometry and subnanometric lattice constant. In some physical systems, such as ferroelectric perovskites, a perfect crystalline structure forms even when the condensing substances are non-stoichiometric. The resulting solids have compositional disorder and complex macroscopic properties, such as giant susceptibilities and non-ergodicity. Here, we observe the spontaneous formation of a cubic structure in composite ferroelectric potassium-lithium-tantalate-niobate with micrometric lattice constant, 104 times larger than that of the underlying perovskite lattice. The 3D effect is observed in specifically designed samples in which the substitutional mixture varies periodically along one specific crystal axis. Laser propagation indicates a coherent polarization super-crystal that produces an optical X-ray diffractometry, an ordered mesoscopic state of matter with important implications for critical phenomena and applications in miniaturized 3D optical technologies.

  9. Students' Satisfaction and Valuation of Web-Based Lecture Recording Technologies

    ERIC Educational Resources Information Center

    Taplin, Ross H.; Low, Lee Hun; Brown, Alistair M.

    2011-01-01

    This paper explores students' satisfaction and valuation of web-based lecture recording technologies (WBLT) that enable students to download recordings of lectures they could not attend or wish to review for revision purposes. The study was undertaken among undergraduates and postgraduates in accounting at an Australian university. In addition to…

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

    SciTech Connect

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

    2014-09-15

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

  11. Automated System Tests Ferroelectric Capacitors

    NASA Technical Reports Server (NTRS)

    Lakata, Mark; Thakoor, Sarita

    1994-01-01

    Polarization-switching parameters measured under computer control. Ferroelectric-capacitor-testing system applies voltage pulses and measures responses of ferroelectric capacitor to determine write; "time dependence of polarization," polarization-retention and fatigue characteristics of capacitor. Highly integrated setup quite flexible, versatile, and interactive, and allows convenient computer storage and analysis of data.

  12. 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.

  13. Conduction at a ferroelectric interface

    DOE PAGESBeta

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

    2014-11-05

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

  14. Conduction at a ferroelectric interface

    SciTech Connect

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

    2014-11-05

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

  15. Advances in Processing of Bulk Ferroelectric Materials

    NASA Astrophysics Data System (ADS)

    Galassi, Carmen

    The development of ferroelectric bulk materials is still under extensive investigation, as new and challenging issues are growing in relation to their widespread applications. Progress in understanding the fundamental aspects requires adequate technological tools. This would enable controlling and tuning the material properties as well as fully exploiting them into the scale production. Apart from the growing number of new compositions, interest in the first ferroelectrics like BaTiO3 or PZT materials is far from dropping. The need to find new lead-free materials, with as high performance as PZT ceramics, is pushing towards a full exploitation of bariumbased compositions. However, lead-based materials remain the best performing at reasonably low production costs. Therefore, the main trends are towards nano-size effects and miniaturisation, multifunctional materials, integration, and enhancement of the processing ability in powder synthesis. Also, in control of dispersion and packing, to let densification occur in milder conditions. In this chapter, after a general review of the composition and main properties of the principal ferroelectric materials, methods of synthesis are analysed with emphasis on recent results from chemical routes and cold consolidation methods based on the colloidal processing.

  16. 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).

  17. Ferroelectric optical image comparator

    DOEpatents

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

    1993-11-30

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

  18. Ferroelectric optical image comparator

    DOEpatents

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

    1993-01-01

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

  19. Nanoscale bit formation in highly (111)-oriented ferroelectric thin films deposited on glass substrates for high-density storage media

    NASA Astrophysics Data System (ADS)

    Kim, Dae Hong; Kim, Yong Kwan; Hong, Seungbum; Kim, Yunseok; Baik, Sunggi

    2011-06-01

    PbTiO3 (PTO) ferroelectric films on Pt(111) bottom electrode layers covering Ta/glass were prepared using pulsed laser deposition. X-ray diffraction patterns revealed that the PTO films were preferentially (111)-oriented. The films were highly crystalline and had a smooth surface with root mean square (RMS) roughness of 1.5 nm. Ferroelectric properties of the PTO films were characterized using piezoresponse force microscopy (PFM). PFM techniques achieved ferroelectric polarization bits with a minimum width of 22 nm, which corresponds to a potential recording density of 1.3 Tbit/in2 in ferroelectric storage devices.

  20. Nanoscale bit formation in highly (111)-oriented ferroelectric thin films deposited on glass substrates for high-density storage media.

    PubMed

    Kim, Dae Hong; Kim, Yong Kwan; Hong, Seungbum; Kim, Yunseok; Baik, Sunggi

    2011-06-17

    PbTiO(3) (PTO) ferroelectric films on Pt(111) bottom electrode layers covering Ta/glass were prepared using pulsed laser deposition. X-ray diffraction patterns revealed that the PTO films were preferentially (111)-oriented. The films were highly crystalline and had a smooth surface with root mean square (RMS) roughness of 1.5 nm. Ferroelectric properties of the PTO films were characterized using piezoresponse force microscopy (PFM). PFM techniques achieved ferroelectric polarization bits with a minimum width of 22 nm, which corresponds to a potential recording density of 1.3 Tbit/in(2) in ferroelectric storage devices. PMID:21508503

  1. Nanoscale bit formation in highly (111)-oriented ferroelectric thin films deposited on glass substrates for high-density storage media.

    SciTech Connect

    Kim, D. H.; Kim, Y. K.; Hong, S.; Kim, Y.; Baik, S.

    2011-04-21

    PbTiO{sub 3} (PTO) ferroelectric films on Pt(111) bottom electrode layers covering Ta/glass were prepared using pulsed laser deposition. X-ray diffraction patterns revealed that the PTO films were preferentially (111)-oriented. The films were highly crystalline and had a smooth surface with root mean square (RMS) roughness of 1.5 nm. Ferroelectric properties of the PTO films were characterized using piezoresponse force microscopy (PFM). PFM techniques achieved ferroelectric polarization bits with a minimum width of 22 nm, which corresponds to a potential recording density of 1.3 Tbit/in{sup 2} in ferroelectric storage devices.

  2. Coupled ferromagnetism and ferroelectricity in superlattices of non-ferroelectric antiferromagnetic manganites

    NASA Astrophysics Data System (ADS)

    Burton, J. D.; Rogdakis, K.; Seo, J. W.; Viskadourakis, Z.; Wang, Y.; Ah Qune, L.; Choi, E.; Tsymbal, E.; Lee, J.; Panagopoulos, C.

    2013-03-01

    Complex oxide heterostructures present a promising avenue for the design of multifunctional properties which may find application in a variety of technological systems. In heterostructures composed of transition metal oxides the disruption introduced by an interface can affect the balance of the competing interactions among spins, charges and orbitals. This has led to the emergence of properties absent in the original building blocks of a heterostructure. We will report on the discovery of magnetically tunable ferroelectricity in artificial tri-layer superlattices consisting of non-ferroelectric and non-ferromagnetic components: NdMnO3/SrMnO3/LaMnO3. Ferroelectricity was observed below 40 K exhibiting strong tunability by superlattice periodicity. Furthermore, magnetoelectric coupling resulted in 150% magnetic modulation of the polarization. First-principles calculations indicate that broken space inversion symmetry and mixed valency give rise to the observed behavior. This discovery highlights the importance of tri-layered systems for the engineering of emergent properties in oxide heterostructures. 1 University of Nebraska - Lincoln, 2 Foundation for Research and Technology - Hellas, Heraklion, Greece, 3 Nanyang Technological University, Nanyang, Singapore, 4 Sungkyunkwan University, Suwon, Republic of Korea

  3. Ferroelectricity in corundum derivatives

    NASA Astrophysics Data System (ADS)

    Ye, Meng; Vanderbilt, David

    2016-04-01

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

  4. Ferroelectricity in corundum derivatives

    NASA Astrophysics Data System (ADS)

    Ye, Meng; Vanderbilt, David

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

  5. Spectroscopic signature for ferroelectric ice

    NASA Astrophysics Data System (ADS)

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

    2014-09-01

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

  6. Ferroelectricity and tunneling electroresistance effect in asymmetric ferroelectric tunnel junctions

    NASA Astrophysics Data System (ADS)

    Tao, L. L.; Wang, J.

    2016-06-01

    We report the investigation on the ferroelectricity and tunneling electroresistance (TER) effect in PbTiO3 (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 the 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.

  7. Hierarchical dielectric orders in layered ferroelectrics Bi2SiO5

    PubMed Central

    Kim, Younghun; Kim, Jungeun; Fujiwara, Akihiko; Taniguchi, Hiroki; Kim, Sungwng; Tanaka, Hiroshi; Sugimoto, Kunihisa; Kato, Kenichi; Itoh, Mitsuru; Hosono, Hideo; Takata, Masaki

    2014-01-01

    Electric dipole engineering is now an emerging technology for high electron-mobility transistors, ferroelectric random access memory and multiferroic devices etc. Although various studies to provide insight into dipole moment behaviour, such as phase transition, order and disorder states, have been reported, macroscopic spontaneous polarization has been mainly discussed so far. Here, visualization of the electric dipole arrangement in layered ferroelectrics Bi2SiO5 by means of combined analysis of maximum entropy charge density and electrostatic potential distribution analysis based on synchrotron radiation X-ray powder diffraction data is reported. It was found that the hierarchical dipole orders, the weak-ferroelectric and ferroelectric configurations, were observed in the Bi2O2 and the SiO3 layers, respectively, and the ferrielectric configuration was realised by the interlayer interaction. This discovery provides a new method to visualize the local polarization in ferroelectric materials. PMID:25075334

  8. Hierarchical dielectric orders in layered ferroelectrics Bi2SiO5.

    PubMed

    Kim, Younghun; Kim, Jungeun; Fujiwara, Akihiko; Taniguchi, Hiroki; Kim, Sungwng; Tanaka, Hiroshi; Sugimoto, Kunihisa; Kato, Kenichi; Itoh, Mitsuru; Hosono, Hideo; Takata, Masaki

    2014-05-01

    Electric dipole engineering is now an emerging technology for high electron-mobility transistors, ferroelectric random access memory and multiferroic devices etc. Although various studies to provide insight into dipole moment behaviour, such as phase transition, order and disorder states, have been reported, macroscopic spontaneous polarization has been mainly discussed so far. Here, visualization of the electric dipole arrangement in layered ferroelectrics Bi2SiO5 by means of combined analysis of maximum entropy charge density and electrostatic potential distribution analysis based on synchrotron radiation X-ray powder diffraction data is reported. It was found that the hierarchical dipole orders, the weak-ferroelectric and ferroelectric configurations, were observed in the Bi2O2 and the SiO3 layers, respectively, and the ferrielectric configuration was realised by the interlayer interaction. This discovery provides a new method to visualize the local polarization in ferroelectric materials. PMID:25075334

  9. [New technologies in primary care: people, machines, records, and networks. SESPAS Report 2012].

    PubMed

    Alfaro, Mercedes; Bonis, Julio; Bravo, Rafael; Fluiters, Enrique; Minué, Sergio

    2012-03-01

    The new technologies and the importance of their development in primary care are clear. Technology is important insofar as it helps to resolve practical problems that arise when attempts are made to improve patient care. Many applications can be found under the heading of "new information and communication technologies" in healthcare, but the present article focusses on two of the most significant examples: the electronic health record and the Internet, bearing in mind that the aims being sought and the people using these applications are more significant than the technologies themselves. PMID:22336322

  10. Anharmonic lattice interactions in improper ferroelectrics for multiferroic design.

    PubMed

    Young, Joshua; Stroppa, Alessandro; Picozzi, Silvia; Rondinelli, James M

    2015-07-22

    The design and discovery of new multiferroics, or materials that display both ferroelectricity and long-range magnetic order, is of fundamental importance for new electronic technologies based on low-power consumption. Far too often, however, the mechanisms causing these properties to arise are incompatible or occur at ordering temperatures below room temperature. One design strategy which has gained considerable interest is to begin with a magnetic material, and find novel ways to induce a spontaneous electric polarization within the structure. To this end, anharmonic interactions coupling multiple lattice modes have been used to lift inversion symmetry in magnetic dielectrics. Here we provide an overview of the microscopic mechanisms by which various types of cooperative atomic displacements result in ferroelectricity through anharmonic multi-mode coupling, as well as the types of materials most conducive to these lattice instabilities. The review includes a description of the origins of the displacive modes, a classification of possible non-polar lattice modes, as well as how their coupling can produce spontaneous polarizations. We then survey the recent improper ferroelectric literature, and describe how the materials discussed fall within a proposed classification scheme, offering new directions for the theoretical design of magnetic ferroelectrics. Finally, we offer prospects for the future discovery of new magnetic improper ferroelectrics, as well as detail remaining challenges and open questions facing this exciting new field. PMID:26125654

  11. Ferroelectricity in molecular solids: a review of electrodynamic properties.

    PubMed

    Tomić, S; Dressel, M

    2015-09-01

    In conventional ferroelectrics the polarization is induced either by the relative displacement of positive and negative ions due to a lattice distortion or by the collective alignment of permanent electric dipoles. Strongly correlated materials with the inversion-symmetry-broken ground states feature electronic ferroelectricity, a phenomenon which has recently caught the attention of condensed matter physicists due to its great fundamental and technological importance. The discovery of electronic ferroelectricity in one and two-dimensional molecular solids is an exciting development because they show a rich variety of nonlinear properties and complex electrodynamics, including nontrivial emergent excitations. We summarize key experimental results, sketch the current theoretical understanding and outline promising prospects of this phenomenon which have great potential for future electronic devices. PMID:26214019

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

    NASA Technical Reports Server (NTRS)

    MacLeod, Todd C.; Ho, Fat Duen

    1999-01-01

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

  13. Negative-pressure-induced enhancement in a freestanding ferroelectric

    NASA Astrophysics Data System (ADS)

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

    2015-10-01

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

  14. Tunnel electroresistance through organic ferroelectrics

    PubMed Central

    Tian, B. B.; Wang, J. L.; Fusil, S.; Liu, Y.; Zhao, X. L.; Sun, S.; Shen, H.; Lin, T.; Sun, J. L.; Duan, C. G.; Bibes, M.; Barthélémy, A.; Dkhil, B.; Garcia, V.; Meng, X. J.; Chu, J. H.

    2016-01-01

    Organic electronics is emerging for large-area applications such as photovoltaic cells, rollable displays or electronic paper. Its future development and integration will require a simple, low-power organic memory, that can be written, erased and readout electrically. Here we demonstrate a non-volatile memory in which the ferroelectric polarisation state of an organic tunnel barrier encodes the stored information and sets the readout tunnel current. We use high-sensitivity piezoresponse force microscopy to show that films as thin as one or two layers of ferroelectric poly(vinylidene fluoride) remain switchable with low voltages. Submicron junctions based on these films display tunnel electroresistance reaching 1,000% at room temperature that is driven by ferroelectric switching and explained by electrostatic effects in a direct tunnelling regime. Our findings provide a path to develop low-cost, large-scale arrays of organic ferroelectric tunnel junctions on silicon or flexible substrates. PMID:27143121

  15. 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.

  16. Tunnel electroresistance through organic ferroelectrics.

    PubMed

    Tian, B B; Wang, J L; Fusil, S; Liu, Y; Zhao, X L; Sun, S; Shen, H; Lin, T; Sun, J L; Duan, C G; Bibes, M; Barthélémy, A; Dkhil, B; Garcia, V; Meng, X J; Chu, J H

    2016-01-01

    Organic electronics is emerging for large-area applications such as photovoltaic cells, rollable displays or electronic paper. Its future development and integration will require a simple, low-power organic memory, that can be written, erased and readout electrically. Here we demonstrate a non-volatile memory in which the ferroelectric polarisation state of an organic tunnel barrier encodes the stored information and sets the readout tunnel current. We use high-sensitivity piezoresponse force microscopy to show that films as thin as one or two layers of ferroelectric poly(vinylidene fluoride) remain switchable with low voltages. Submicron junctions based on these films display tunnel electroresistance reaching 1,000% at room temperature that is driven by ferroelectric switching and explained by electrostatic effects in a direct tunnelling regime. Our findings provide a path to develop low-cost, large-scale arrays of organic ferroelectric tunnel junctions on silicon or flexible substrates. PMID:27143121

  17. Tunnel electroresistance through organic ferroelectrics

    NASA Astrophysics Data System (ADS)

    Tian, B. B.; Wang, J. L.; Fusil, S.; Liu, Y.; Zhao, X. L.; Sun, S.; Shen, H.; Lin, T.; Sun, J. L.; Duan, C. G.; Bibes, M.; Barthélémy, A.; Dkhil, B.; Garcia, V.; Meng, X. J.; Chu, J. H.

    2016-05-01

    Organic electronics is emerging for large-area applications such as photovoltaic cells, rollable displays or electronic paper. Its future development and integration will require a simple, low-power organic memory, that can be written, erased and readout electrically. Here we demonstrate a non-volatile memory in which the ferroelectric polarisation state of an organic tunnel barrier encodes the stored information and sets the readout tunnel current. We use high-sensitivity piezoresponse force microscopy to show that films as thin as one or two layers of ferroelectric poly(vinylidene fluoride) remain switchable with low voltages. Submicron junctions based on these films display tunnel electroresistance reaching 1,000% at room temperature that is driven by ferroelectric switching and explained by electrostatic effects in a direct tunnelling regime. Our findings provide a path to develop low-cost, large-scale arrays of organic ferroelectric tunnel junctions on silicon or flexible substrates.

  18. Ferroelectric infrared detector and method

    DOEpatents

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

    2010-03-30

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

  19. Optical Imaging of Nonuniform Ferroelectricity and Strain at the Diffraction Limit.

    PubMed

    Vlasin, Ondrej; Casals, Blai; Dix, Nico; Gutiérrez, Diego; Sánchez, Florencio; Herranz, Gervasi

    2015-01-01

    We have imaged optically the spatial distributions of ferroelectricity and piezoelectricity at the diffraction limit. Contributions to the birefringence from electro-optics--linked to ferroelectricity--as well as strain--arising from converse piezoelectric effects--have been recorded simultaneously in a BaTiO3 thin film. The concurrent recording of electro-optic and piezo-optic mappings revealed that, far from the ideal uniformity, the ferroelectric and piezoelectric responses were strikingly inhomogeneous, exhibiting significant fluctuations over the scale of the micrometer. The optical methods here described are appropriate to study the variations of these properties simultaneously, which are of great relevance when ferroelectrics are downscaled to small sizes for applications in data storage and processing. PMID:26522345

  20. Enrichment of Bibliographic Records of Online Catalogs through OCR and SGML Technology.

    ERIC Educational Resources Information Center

    Peis, Eduardo; Fernandez-Molina, J. Carlos

    1998-01-01

    Presents research on using scanner technology to capture the contents pages of collective monographs, extract bibliographic information, and process this information with a standardized language, such as SGML, for tagging electronic documents. Results confirmed the feasibility of developing a system to automatically enrich records in online…

  1. A Community Health Record: Improving Health Through Multisector Collaboration, Information Sharing, and Technology.

    PubMed

    King, Raymond J; Garrett, Nedra; Kriseman, Jeffrey; Crum, Melvin; Rafalski, Edward M; Sweat, David; Frazier, Renee; Schearer, Sue; Cutts, Teresa

    2016-01-01

    We present a framework for developing a community health record to bring stakeholders, information, and technology together to collectively improve the health of a community. It is both social and technical in nature and presents an iterative and participatory process for achieving multisector collaboration and information sharing. It proposes a methodology and infrastructure for bringing multisector stakeholders and their information together to inform, target, monitor, and evaluate community health initiatives. The community health record is defined as both the proposed framework and a tool or system for integrating and transforming multisector data into actionable information. It is informed by the electronic health record, personal health record, and County Health Ranking systems but differs in its social complexity, communal ownership, and provision of information to multisector partners at scales ranging from address to zip code. PMID:27609300

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

    NASA Astrophysics Data System (ADS)

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

    2016-01-01

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

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

    PubMed Central

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

    2016-01-01

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

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

    PubMed

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

    2016-01-01

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

  5. Ferroelectricity in undoped hafnium oxide

    NASA Astrophysics Data System (ADS)

    Polakowski, Patrick; Müller, Johannes

    2015-06-01

    We report the observation of ferroelectric characteristics in undoped hafnium oxide thin films in a thickness range of 4-20 nm. The undoped films were fabricated using atomic layer deposition (ALD) and embedded into titanium nitride based metal-insulator-metal (MIM) capacitors for electrical evaluation. Structural as well as electrical evidence for the appearance of a ferroelectric phase in pure hafnium oxide was collected with respect to film thickness and thermal budget applied during titanium nitride electrode formation. Using grazing incidence X-Ray diffraction (GIXRD) analysis, we observed an enhanced suppression of the monoclinic phase fraction in favor of an orthorhombic, potentially, ferroelectric phase with decreasing thickness/grain size and for a titanium nitride electrode formation below crystallization temperature. The electrical presence of ferroelectricity was confirmed using polarization measurements. A remanent polarization Pr of up to 10 μC cm-2 as well as a read/write endurance of 1.6 × 105 cycles was measured for the pure oxide. The experimental results reported here strongly support the intrinsic nature of the ferroelectric phase in hafnium oxide and expand its applicability beyond the doped systems.

  6. Ferroelectricity in undoped hafnium oxide

    SciTech Connect

    Polakowski, Patrick; Müller, Johannes

    2015-06-08

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

  7. A wireless recording system that utilizes Bluetooth technology to transmit neural activity in freely moving animals.

    PubMed

    Hampson, Robert E; Collins, Vernell; Deadwyler, Sam A

    2009-09-15

    A new wireless transceiver is described for recording individual neuron firing from behaving rats utilizing Bluetooth transmission technology and a processor onboard for discrimination of neuronal waveforms and associated time stamps. This universal brain activity transmitter (UBAT) is attached to rodents via a backpack and amplifier headstage and can transmit 16 channels of captured neuronal firing data via a Bluetooth transceiver chip over very large and unconstrained distances. The onboard microprocessor of the UBAT allows flexible online control over waveform isolation criteria via transceiver instruction and the two-way communication capacity allows for closed-loop applications between neural events and behavioral or physiological processes which can be modified by transceiver instructions. A detailed description of the multiplexer processing of channel data as well as examples of neuronal recordings in different behavioral testing contexts is provided to demonstrate the capacity for robust transmission within almost any laboratory environment. A major advantage of the UBAT is the long transmission range and lack of object-based line of sight interference afforded by Bluetooth technology, allowing flexible recording capabilities within multiple experimental paradigms without interruption. Continuous recordings over very large distance separations from the monitor station are demonstrated providing experimenters with recording advantages not previously available with other telemetry devices. PMID:19524612

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

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

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

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

    PubMed

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

    2016-01-01

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

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

    PubMed Central

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

    2016-01-01

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

  11. Ferroelectric Polymer Composite with Enhanced Breakdown Strength

    NASA Astrophysics Data System (ADS)

    Han, Kuo; Gadinski, Matthew; Wang, Qing

    2013-03-01

    Numerous efforts have been made in the past decades to improve the energy storage capability of dielectric capacitors by incorporating ceramic addictives into polymers. Ferroelectric polymers have been particularly interesting as matrix for dielectric composites because of their highest dielectric permittivity and energy density. However, most polymer composites suffer from significantly reduced breakdown strength, which compromises the potential gain in energy density. In this work, various metallic alkoxide were introduced into the functionalized ferroelectric poly(vinylidene fluoride-co- chlorotrifluoroethylene), P(VDF-CTFE), via covalent bonding. The composite with the optimized composition exhibited the Weibull statistical breakdown strength of 504.8 MV/m, 67.6 % higher than the pristine polymer. The enhanced breakdown strength was mainly ascribed to the cross-linking and the formation of deep traps, which effectively reduced the conduction and further lowered the energy loss. Additionally, the homogeneous dispersion of the inorganic phase and the small contrast in permittivity between the polymer and amorphous oxides also contribute to the improved dielectric strength. The dielectric spectra of the composites have been recorded at varied temperatures and frequencies, which revealed the presence of the interfacial polarization layer in the composites.

  12. Stress effects in ferroelectric perovskite thin-films

    NASA Astrophysics Data System (ADS)

    Zednik, Ricardo Johann

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

  13. Ferroelectric memory based on nanostructures

    NASA Astrophysics Data System (ADS)

    Liu, Xingqiang; Liu, Yueli; Chen, Wen; Li, Jinchai; Liao, Lei

    2012-06-01

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

  14. Ferroelectric memory based on nanostructures

    PubMed Central

    2012-01-01

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

  15. 77 FR 42764 - Distribution of the 2005, 2006, 2007 and 2008 Digital Audio Recording Technology Royalty Funds...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-07-20

    ... Copyright Royalty Board Distribution of the 2005, 2006, 2007 and 2008 Digital Audio Recording Technology... the digital audio recording technology royalty fees in the 2005, 2006, 2007 and 2008 Musical Works... Judges issued an order granting certain claimants' (i.e., Broadcast Music, Inc., the American Society...

  16. 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.

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

    PubMed

    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. PMID:25353817

  18. Ferroelectric domain formation in discotic liquid crystals: Monte Carlo study on the influence of boundary conditions.

    PubMed

    Bose, Tushar Kanti; Saha, Jayashree

    2015-10-01

    The realization of a spontaneous macroscopic ferroelectric order in fluids of anisotropic mesogens is a topic of both fundamental and technological interest. Recently we demonstrated that a system of dipolar achiral disklike ellipsoids can exhibit long-searched ferroelectric liquid crystalline phases of dipolar origin. In the present work, extensive off-lattice Monte Carlo simulations are used to investigate the phase behavior of the system under the influences of the electrostatic boundary conditions that restrict any global polarization. We find that the system develops strongly ferroelectric slablike domains periodically arranged in an antiferroelectric fashion. Exploring the phase behavior at different dipole strengths, we find existence of the ferroelectric nematic and ferroelectric columnar order inside the domains. For higher dipole strengths, a biaxial phase is also obtained with a similar periodic array of ferroelectric slabs of antiparallel polarizations. We have studied the depolarizing effects by using both the Ewald summation and the spherical cutoff techniques. We present and compare the results of the two different approaches of considering the depolarizing effects in this anisotropic system. It is explicitly shown that the domain size increases with the system size as a result of considering a longer range of dipolar interactions. The system exhibits pronounced system size effects for stronger dipolar interactions. The results provide strong evidence to the novel understanding that the dipolar interactions are indeed sufficient to produce long-range ferroelectric order in anisotropic fluids. PMID:26565261

  19. 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.

  20. Atomistic simulations of caloric effects in ferroelectrics

    NASA Astrophysics Data System (ADS)

    Lisenkov, Sergey; Ponomareva, Inna

    2013-03-01

    The materials that exhibit large caloric effects have emerged as promising candidates for solid-state refrigeration which is an energy-efficient and environmentally friendly alternative to the conventional refrigeration technology. However, despite recent ground breaking discoveries of giant caloric effects in some materials they appear to remain one of nature's rarities. Here we use atomistic simulations to study electrocaloric and elastocaloric effects in Ba0.5Sr0.5TiO3 and PbTiO3 ferroelectrics. Our study reveals the intrinsic features of such caloric effects in ferroelectrics and their potential to exhibit giant caloric effects. Some of the findings include the coexistence of negative and positive electrocaloric effects in one material and an unusual field-driven transition between them as well as the coexistence of multiple giant caloric effects in Ba0.5Sr0.5TiO3 alloys. These findings could potentially lead to new paradigms for cooling devices. This work is partially supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering under award DE-SC0005245.

  1. New Advanced Technologies to Provide Decentralised and Secure Access to Medical Records: Case Studies in Oncology

    PubMed Central

    Quantin, Catherine; Coatrieux, Gouenou; Allaert, François André; Fassa, Maniane; Bourquard, Karima; Boire, Jean-Yves; de Vlieger, Paul; Maigne, Lydia; Breton, Vincent

    2009-01-01

    The main problem for health professionals and patients in accessing information is that this information is very often distributed over many medical records and locations. This problem is particularly acute in cancerology because patients may be treated for many years and undergo a variety of examinations. Recent advances in technology make it feasible to gain access to medical records anywhere and anytime, allowing the physician or the patient to gather information from an “ephemeral electronic patient record”. However, this easy access to data is accompanied by the requirement for improved security (confidentiality, traceability, integrity, ...) and this issue needs to be addressed. In this paper we propose and discuss a decentralised approach based on recent advances in information sharing and protection: Grid technologies and watermarking methodologies. The potential impact of these technologies for oncology is illustrated by the examples of two experimental cases: a cancer surveillance network and a radiotherapy treatment plan. It is expected that the proposed approach will constitute the basis of a future secure “google-like” access to medical records. PMID:19718446

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

    SciTech Connect

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

    2010-08-19

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

  3. Guide to the Records Relating to Science and Technology in the British Public Record Office: A RAMP Study.

    ERIC Educational Resources Information Center

    Jubb, Michael

    Prepared under contract with the International Council on Archives (ICA), this guide provides descriptions of all classes of public records held by the British Public Record Office (PRO) which are likely to contain scientific or technical information. The PRO is responsible for keeping and making available to the public those records of the…

  4. Coherent coupling in ferroelectric superlattices

    SciTech Connect

    Li, S.; Eastman, J.A.; Vetrone, J.; Newnham, R.E.; Cross, L.E.

    1996-07-01

    The phase transition and dielectric behavior of ferroelectric multilayers have been discussed. The coherent interaction between ultra-thin layers can be significantly strong, resulting in a broad diffuse phase transition. The thicknesses of layers and their spatial distributions hold the keys of enhancing dielectric properties in a broad temperature range.

  5. Pulse-modulated multilevel data storage in an organic ferroelectric resistive memory diode

    PubMed Central

    Lee, Jiyoul; van Breemen, Albert J. J. M.; Khikhlovskyi, Vsevolod; Kemerink, Martijn; Janssen, Rene A. J.; Gelinck, Gerwin H.

    2016-01-01

    We demonstrate multilevel data storage in organic ferroelectric resistive memory diodes consisting of a phase-separated blend of P(VDF-TrFE) and a semiconducting polymer. The dynamic behaviour of the organic ferroelectric memory diode can be described in terms of the inhomogeneous field mechanism (IFM) model where the ferroelectric components are regarded as an assembly of randomly distributed regions with independent polarisation kinetics governed by a time-dependent local field. This allows us to write and non-destructively read stable multilevel polarisation states in the organic memory diode using controlled programming pulses. The resulting 2-bit data storage per memory element doubles the storage density of the organic ferroelectric resistive memory diode without increasing its technological complexity, thus reducing the cost per bit. PMID:27080264

  6. Pulse-modulated multilevel data storage in an organic ferroelectric resistive memory diode

    NASA Astrophysics Data System (ADS)

    Lee, Jiyoul; van Breemen, Albert J. J. M.; Khikhlovskyi, Vsevolod; Kemerink, Martijn; Janssen, Rene A. J.; Gelinck, Gerwin H.

    2016-04-01

    We demonstrate multilevel data storage in organic ferroelectric resistive memory diodes consisting of a phase-separated blend of P(VDF-TrFE) and a semiconducting polymer. The dynamic behaviour of the organic ferroelectric memory diode can be described in terms of the inhomogeneous field mechanism (IFM) model where the ferroelectric components are regarded as an assembly of randomly distributed regions with independent polarisation kinetics governed by a time-dependent local field. This allows us to write and non-destructively read stable multilevel polarisation states in the organic memory diode using controlled programming pulses. The resulting 2-bit data storage per memory element doubles the storage density of the organic ferroelectric resistive memory diode without increasing its technological complexity, thus reducing the cost per bit.

  7. Solving certain dental records problems with technology--the Canadian solution in the Thailand tsunami response.

    PubMed

    Sweet, David

    2006-05-15

    Each natural or man-made disaster presents a different set of circumstances and, as a consequence, each event results in new challenges for response teams. The very large number of deceased victims in recent tragic events is certainly one of the enormous challenges that can tax many different resources for identification specialists. But there are other significant challenges. And during the response, some of these seem insurmountable. They can be solved if we embrace technologies outside the customary disciplines. The Canadian identification effort following the December 2004 tsunami involved responders from several disciplines. Each discipline faced challenges in many different and special areas that were difficult and in some cases previously unseen. This paper presents examples of the ways the Canadian identification team used Internet technology to solve problems that were encountered when it became necessary to duplicate victims' dental, medical and personal records, and transport these records halfway around the world. Digital images of the records were saved at high resolution in multi-page PDF files. These images were made available to on-site personnel using an encrypted, password-secured website. PMID:16542803

  8. Genetic data and electronic health records: a discussion of ethical, logistical and technological considerations

    PubMed Central

    Shoenbill, Kimberly; Fost, Norman; Tachinardi, Umberto; Mendonca, Eneida A

    2014-01-01

    Objective The completion of sequencing the human genome in 2003 has spurred the production and collection of genetic data at ever increasing rates. Genetic data obtained for clinical purposes, as is true for all results of clinical tests, are expected to be included in patients’ medical records. With this explosion of information, questions of what, when, where and how to incorporate genetic data into electronic health records (EHRs) have reached a critical point. In order to answer these questions fully, this paper addresses the ethical, logistical and technological issues involved in incorporating these data into EHRs. Materials and methods This paper reviews journal articles, government documents and websites relevant to the ethics, genetics and informatics domains as they pertain to EHRs. Results and discussion The authors explore concerns and tasks facing health information technology (HIT) developers at the intersection of ethics, genetics, and technology as applied to EHR development. Conclusions By ensuring the efficient and effective incorporation of genetic data into EHRs, HIT developers will play a key role in facilitating the delivery of personalized medicine. PMID:23771953

  9. Web technology for emergency medicine and secure transmission of electronic patient records.

    PubMed

    Halamka, J D

    1998-01-01

    The American Heritage dictionary defines the word "web" as "something intricately contrived, especially something that ensnares or entangles." The wealth of medical resources on the World Wide Web is now so extensive, yet disorganized and unmonitored, that such a definition seems fitting. In emergency medicine, for example, a field in which accurate and complete information, including patients' records, is urgently needed, more than 5000 Web pages are available today, whereas fewer than 50 were available in December 1994. Most sites are static Web pages using the Internet to publish textbook material, but new technology is extending the scope of the Internet to include online medical education and secure exchange of clinical information. This article lists some of the best Web sites for use in emergency medicine and then describes a project in which the Web is used for transmission and protection of electronic medical records. PMID:9673087

  10. New devices using ferroelectric thin films

    SciTech Connect

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

    1989-01-01

    Recent developments in the fabrication technologies of ferroelectric thin films in general and of PZT (lead zirconate titanate) and PLZT (lead lanthanum zirconate titanate) thin films in particular have suggested the feasibility of several new devices. Integrated optical devices for information processing and high-speed switching, high-density optical information processing and storage devices and spatial light modulators are some of the applications currently being investigated for these films. Ongoing studies of the longitudinal electrooptic effects and the photosensitivities of PZT and PLZT thin films have established the feasibility of erasable/rewritable optical memories with fast switching and potentially long lifetimes compared to current magneto-optic thin film devices. Some properties of PZT thin films and of new devices based on those properties are described in this paper. 15 refs., 5 figs., 1 tab.

  11. Fork gratings based on ferroelectric liquid crystals.

    PubMed

    Ma, Y; Wei, B Y; Shi, L Y; Srivastava, A K; Chigrinov, V G; Kwok, H-S; Hu, W; Lu, Y Q

    2016-03-21

    In this article, we disclose a fork grating (FG) based on the photo-aligned ferroelectric liquid crystal (FLC). The Digital Micro-mirror Device based system is used as a dynamic photomask to generated different holograms. Because of controlled anchoring energy, the photo alignment process offers optimal conditions for the multi-domain FLC alignment. Two different electro-optical modes namely DIFF/TRANS and DIFF/OFF switchable modes have been proposed where the diffraction can be switched either to no diffraction or to a completely black state, respectively. The FLC FG shows high diffraction efficiency and fast response time of 50µs that is relatively faster than existing technologies. Thus, the FLC FG may pave a good foundation toward optical vertices generation and manipulation that could find applications in a variety of devices. PMID:27136779

  12. Automated integration of continuous glucose monitor data in the electronic health record using consumer technology.

    PubMed

    Kumar, Rajiv B; Goren, Nira D; Stark, David E; Wall, Dennis P; Longhurst, Christopher A

    2016-05-01

    The diabetes healthcare provider plays a key role in interpreting blood glucose trends, but few institutions have successfully integrated patient home glucose data in the electronic health record (EHR). Published implementations to date have required custom interfaces, which limit wide-scale replication. We piloted automated integration of continuous glucose monitor data in the EHR using widely available consumer technology for 10 pediatric patients with insulin-dependent diabetes. Establishment of a passive data communication bridge via a patient's/parent's smartphone enabled automated integration and analytics of patient device data within the EHR between scheduled clinic visits. It is feasible to utilize available consumer technology to assess and triage home diabetes device data within the EHR, and to engage patients/parents and improve healthcare provider workflow. PMID:27018263

  13. Leveraging electronic healthcare record standards and semantic web technologies for the identification of patient cohorts

    PubMed Central

    Fernández-Breis, Jesualdo Tomás; Maldonado, José Alberto; Marcos, Mar; Legaz-García, María del Carmen; Moner, David; Torres-Sospedra, Joaquín; Esteban-Gil, Angel; Martínez-Salvador, Begoña; Robles, Montserrat

    2013-01-01

    Background The secondary use of electronic healthcare records (EHRs) often requires the identification of patient cohorts. In this context, an important problem is the heterogeneity of clinical data sources, which can be overcome with the combined use of standardized information models, virtual health records, and semantic technologies, since each of them contributes to solving aspects related to the semantic interoperability of EHR data. Objective To develop methods allowing for a direct use of EHR data for the identification of patient cohorts leveraging current EHR standards and semantic web technologies. Materials and methods We propose to take advantage of the best features of working with EHR standards and ontologies. Our proposal is based on our previous results and experience working with both technological infrastructures. Our main principle is to perform each activity at the abstraction level with the most appropriate technology available. This means that part of the processing will be performed using archetypes (ie, data level) and the rest using ontologies (ie, knowledge level). Our approach will start working with EHR data in proprietary format, which will be first normalized and elaborated using EHR standards and then transformed into a semantic representation, which will be exploited by automated reasoning. Results We have applied our approach to protocols for colorectal cancer screening. The results comprise the archetypes, ontologies, and datasets developed for the standardization and semantic analysis of EHR data. Anonymized real data have been used and the patients have been successfully classified by the risk of developing colorectal cancer. Conclusions This work provides new insights in how archetypes and ontologies can be effectively combined for EHR-driven phenotyping. The methodological approach can be applied to other problems provided that suitable archetypes, ontologies, and classification rules can be designed. PMID:23934950

  14. About the deformation of ferroelectric hystereses

    SciTech Connect

    Schenk, T. Yurchuk, E.; Mueller, S.; Schroeder, U.; Starschich, S.; Böttger, U.; Mikolajick, T.

    2014-12-15

    Studying ferroelectric hafnium oxide with focus on memory applications for the past years, discussions frequently involved the shape of measured polarization hystereses, its relation to the device performance, and how to optimize it. A perfect model-like hysteresis is of nearly rectangular shape and all deviations from this situation have to have a certain physical origin. Different phenomena and their impact on the shape of the polarization hystereses were reported in literature: Aging, imprint, fatigue, or dielectric interface layers to name a few examples. A collection of these phenomena is not easily found up to now. Thus, filling or at least reducing this gap is one of the goals of this work. Moreover, observing a pinched, slanted, or displaced hysteresis, it is quite tempting to try the reverse approach: a derivation of potential structural origins for this curve shape. First, the basics of the dynamic hysteresis measurement and the ferroelectric memories are briefly reviewed. The figures of interest are derived to ensure a proper assessment of imperfections in the hysteresis shape and their influence. It is discussed how a closer look on the polarization loop helps to draw conclusions on what might have caused such a shape or at least how to rule out some phenomena if the expected indications are not reflected in the present curve. Of course, further structural or electrical studies, as they are exemplarily pointed out, are indispensable to find the root cause(s) for the deviations from the ideal hysteresis. But sophisticated methods are not always accessible straightaway and, moreover, a pointer on where to start is always helpful. Especially, the transient currents recorded during a dynamic hysteresis measurement are stressed as a valuable instrument for this purpose. Despite their known potential, these currents are seldom shown in literature.

  15. Wearable Technology Surveillance Data for the Personal Health Record Using the Omaha System: Noise Exposure, Cardiovascular and Stress Biomarkers.

    PubMed

    Kerr, Madeleine J; Chin, Dal Lae; Monsen, Karen A; Hong, OiSaeng

    2016-01-01

    This poster describes a method to prepare noise and health data from wearable technology for standardized representation in the electronic personal health record thus enabling individuals to identify noise-related health risks. Using a case study approach, the authors demonstrate transformation of data to the Omaha System standardized terminology in order to depict the data graphically in a personal health record. PMID:27332479

  16. Optical Imaging of Nonuniform Ferroelectricity and Strain at the Diffraction Limit

    PubMed Central

    Vlasin, Ondrej; Casals, Blai; Dix, Nico; Gutiérrez, Diego; Sánchez, Florencio; Herranz, Gervasi

    2015-01-01

    We have imaged optically the spatial distributions of ferroelectricity and piezoelectricity at the diffraction limit. Contributions to the birefringence from electro-optics –linked to ferroelectricity– as well as strain –arising from converse piezoelectric effects– have been recorded simultaneously in a BaTiO3 thin film. The concurrent recording of electro-optic and piezo-optic mappings revealed that, far from the ideal uniformity, the ferroelectric and piezoelectric responses were strikingly inhomogeneous, exhibiting significant fluctuations over the scale of the micrometer. The optical methods here described are appropriate to study the variations of these properties simultaneously, which are of great relevance when ferroelectrics are downscaled to small sizes for applications in data storage and processing. PMID:26522345

  17. Ferroelectric Stirling-Cycle Refrigerator

    NASA Technical Reports Server (NTRS)

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

    1999-01-01

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

  18. Employee problems and their consequences in the technology industry: evidence from surveys and counseling records.

    PubMed

    Wang, Ching-Wen; Lin, Po-Chang; Sha, Chyuan

    2014-06-01

    To support employees' work and health, organizations should help employees cope with common problems. Previous studies have focused primarily on work-related problems across multiple industries rather than on evaluating industry-specific issues. Here, two approaches identified common work and non-work employee problems in the technology industry with the strongest correlations with psychosomatic health and life satisfaction. Study 1 used questionnaires to identify the problems that were perceived as the most frequent by lower-level employees (N = 355) working in the technology industry. Study 2 evaluated employees' coping behaviors by analyzing (with permission) counseling records collected from an employee assistance service company (N = 276). Employees reported a variety of problems; work problems were the only problems (of the top 5 problems) reported in both studies. Several problems emerged in the counseling records (e.g., legal issues, career development, family and marriage problems, and emotional problems) but not in the surveys. Future research should apply these observations to develop scales for measuring employee stressors. PMID:25074298

  19. 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.

  20. Performance improvement indicators of the Medical Records Department and Information Technology (IT) in hospitals

    PubMed Central

    Ajami, Sima; Ketabi, Saedeh; Torabiyan, Fatemeh

    2015-01-01

    Medical Record Department (MRD) has a vital role in making short and long term plans to improve health system services. The aim of this study was to describe performance improvement indicators of hospital MRD and information technology (IT). Collection of Data: A search was conducted in various databases, through related keywords in articles, books, and abstracts of conferences from 2001 to 2009. About 58 articles and books were available which were evaluated and finally 15 of them were selected based on their relevance to the study. MRD must be capable of supporting tasks such as patient care and continuity, institute management processes, medical education programs, medical research, communication between different wards of a hospital and administrative and medical staff. The use of IT in MRD can facilitate access to department, expedite communication within and outside department, reduce space with electronic medical records, reduce costs, accelerate activities such as coding by use of coding guide software and facilitate retrieval of records that will ultimately improve the performance of MRD. PMID:26150874

  1. Ferroelectric-dielectric tunable composites

    NASA Astrophysics Data System (ADS)

    Sherman, Vladimir O.; Tagantsev, Alexander K.; Setter, Nava; Iddles, David; Price, Tim

    2006-04-01

    The dielectric response of ferroelectric-dielectric composites is theoretically addressed. Dielectric permittivity, tunability (relative change of the permittivity driven by dc electric field), and loss tangent are evaluated for various composite models. The analytical results for small dielectric concentration and relative tunability are obtained in terms of the traditional electrostatic consideration. The results for large tunability are obtained numerically. A method is proposed for the evaluation of the tunability and loss at large concentrations of the dielectric. The basic idea of the method is to reformulate the effective medium approach in terms of electrical energies stored and dissipated in the composite. The important practical conclusion of the paper is that, for random ferroelectric-dielectric composite, the addition of small amounts of a linear dielectric into the tunable ferroelectric results in an increase of the tunability of the mixture. The loss tangent of such composites is shown to be virtually unaffected by the addition of moderate amounts of the low-loss dielectric. The experimental data for (Ba,Sr)TiO3 based composites are analyzed in terms of the theory developed and shown to be in a reasonable agreement with the theoretical results.

  2. Electrocaloric effect in relaxor ferroelectrics

    NASA Astrophysics Data System (ADS)

    Pirc, R.; Kutnjak, Z.; Blinc, R.; Zhang, Q. M.

    2011-10-01

    A theoretical model for the electrocaloric effect (ECE) in relaxor ferroelectrics is presented. By solving a self-consistent relation for the ECE temperature change ΔT and minimizing numerically the mean field free energy for relaxors, the field and temperature dependence of ΔT is calculated. The corresponding harmonic Landau coefficient a =a(T), which differs from the ferroelectric case by always being positive, is derived from the spherical random bond-random field model, and the fourth-order coefficient b is treated as a phenomenological parameter, which can be either positive or negative. For b <0, a line of field-induced first-order relaxor-to-ferroelectric phase transitions exists in relaxors, which terminates at a liquid-vapor type critical point ECP,TCP. The critical behavior close to ECP,TCP is analyzed. It is shown that near the first-order phase transition a temperature or field interval or gap formally appears, where ΔT cannot be found. However, domain formation in the coexistence range should restore the continuous behavior of the ECE observed in real systems. Finally, it is shown that the ECE responsivity R1=ΔT /E reaches a maximum near the critical point, in agreement with recent experiments.

  3. A diode for ferroelectric domain-wall motion

    PubMed Central

    Whyte, J.R.; Gregg, J.M.

    2015-01-01

    For over a decade, controlling domain-wall injection, motion and annihilation along nanowires has been the preserve of the nanomagnetics research community. Revolutionary technologies have resulted, like racetrack memory and domain-wall logic. Until recently, equivalent research in analogous ferroic materials did not seem important. However, with the discovery of sheet conduction, the control of domain walls in ferroelectrics has become vital for the future of what has been termed ‘domain-wall electronics'. Here we report the creation of a ferroelectric domain-wall diode, which allows a single direction of motion for all domain walls, irrespective of their polarity, under a series of alternating electric field pulses. The diode's sawtooth morphology is central to its function. Domain walls can move readily in the direction in which thickness increases gradually, but are prevented from moving in the other direction by the sudden thickness increase at the sawtooth edge. PMID:26059779

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

    NASA Technical Reports Server (NTRS)

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

    2011-01-01

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

  5. LTCC Phase Shifters Based on Tunable Ferroelectric Composite Thick Films

    NASA Astrophysics Data System (ADS)

    Nikfalazar, M.; Kohler, C.; Heunisch, A.; Wiens, A.; Zheng, Y.; Schulz, B.; Mikolajek, M.; Sohrabi, M.; Rabe, T.; Binder, J. R.; Jakoby, R.

    2015-11-01

    This paper presents, the investigation of tunable components based on LTCC technology, implementing ferroelectric tunable thick-film dielectric. The tunable loaded line phase shifters are fabricated with metal-insulator-metal (MIM) varactors to demonstrate the capabilities of this method for packaging of the tunable components. The MIM varactors consist of one tunable dielectric paste layer that is printed between two silver layers. The tunable ferroelectric paste is optimized for LTCC sintering temperature around 850°C. The phase shifters are fabricated in two different process. They were achieved a figure of merit of 24°/dB (phase shift 192°) at 3 GHz and 18°/dB (phase shift 98°) at 4.4 GHz by using seven unit cells that each unit cell consisting of two MIM varactors.

  6. Ferroelectrically driven spatial carrier density modulation in graphene

    NASA Astrophysics Data System (ADS)

    Baeumer, Christoph; Saldana-Greco, Diomedes; Martirez, John Mark P.; Rappe, Andrew M.; Shim, Moonsub; Martin, Lane W.

    2015-01-01

    The next technological leap forward will be enabled by new materials and inventive means of manipulating them. Among the array of candidate materials, graphene has garnered much attention; however, due to the absence of a semiconducting gap, the realization of graphene-based devices often requires complex processing and design. Spatially controlled local potentials, for example, achieved through lithographically defined split-gate configurations, present a possible route to take advantage of this exciting two-dimensional material. Here we demonstrate carrier density modulation in graphene through coupling to an adjacent ferroelectric polarization to create spatially defined potential steps at 180°-domain walls rather than fabrication of local gate electrodes. Periodic arrays of p-i junctions are demonstrated in air (gate tunable to p-n junctions) and density functional theory reveals that the origin of the potential steps is a complex interplay between polarization, chemistry, and defect structures in the graphene/ferroelectric couple.

  7. Ferroelectrically driven spatial carrier density modulation in graphene.

    PubMed

    Baeumer, Christoph; Saldana-Greco, Diomedes; Martirez, John Mark P; Rappe, Andrew M; Shim, Moonsub; Martin, Lane W

    2015-01-01

    The next technological leap forward will be enabled by new materials and inventive means of manipulating them. Among the array of candidate materials, graphene has garnered much attention; however, due to the absence of a semiconducting gap, the realization of graphene-based devices often requires complex processing and design. Spatially controlled local potentials, for example, achieved through lithographically defined split-gate configurations, present a possible route to take advantage of this exciting two-dimensional material. Here we demonstrate carrier density modulation in graphene through coupling to an adjacent ferroelectric polarization to create spatially defined potential steps at 180°-domain walls rather than fabrication of local gate electrodes. Periodic arrays of p-i junctions are demonstrated in air (gate tunable to p-n junctions) and density functional theory reveals that the origin of the potential steps is a complex interplay between polarization, chemistry, and defect structures in the graphene/ferroelectric couple. PMID:25609217

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

  9. Magnetic and Ferroelectric Anisotropy in Multiferroic FeVO4

    NASA Astrophysics Data System (ADS)

    Abdelhamid, Ehab; Dixit, Ambesh; Kimura, Kenta; Kimura, Tsuyoshi; Jayakumar, Onattu; Naik, Vaman; Naik, Ratna; Lawes, Gavin; Nadgorny, Boris

    FeVO4 has been studied as a model system for understanding the magnetoelectric interaction mechanisms in low symmetry multiferroics. Triclinic FeVO4 is characterized by two antiferromagnetic phase transitions, occurring at TN 1 = 22 K and TN 2 = 15 K, with the latter transition signaling a break in the space inversion symmetry, accompanied by the development of a non-collinear magnetic order which induces ferroelectricity. Earlier measurements on polycrystalline FeVO4 doped with magnetic (Cr and Mn) as well as non magnetic (Zn) dopants indicate the stability of the two antiferromagnetic transition temperatures. In this work, single crystals of both undoped and doped FeVO4 were grown from flux. To track the changes in lattice parameters induced by changing the doping concentration (measured by EDAX), XRD and Raman spectra were obtained. By recording the magnetization along two different crystal orientations, we were able to confirm the easy magnetic axis in this structure. Finally, we obtain the crystal's ferroelectric polarization along two different directions in an attempt to further understand the mechanism responsible for the ferroelectric transition. This work is supported by the NSF under DMR-1306449.

  10. Polyimide thin-film dielectrics on ferroelectrics

    NASA Technical Reports Server (NTRS)

    Galiardi, R. V.

    1977-01-01

    Conducting layers of multi-layered thin-film ferroelectric device, such as is used in liquid crystal/ferroelectric display, can be electrically isolated using thin-film layer of polyimide. Ease of application and high electrical-breakdown strength allow dependable and economical means of providing dielectric for other thin-film microelectronic devices.

  11. A concept of ferroelectric microparticle propulsion thruster

    SciTech Connect

    Yarmolich, D.; Vekselman, V.; Krasik, Ya. E.

    2008-02-25

    A space propulsion concept using charged ferroelectric microparticles as a propellant is suggested. The measured ferroelectric plasma source thrust, produced mainly by microparticles emission, reaches {approx}9x10{sup -4} N. The obtained trajectories of microparticles demonstrate that the majority of the microparticles are positively charged, which permits further improvement of the thruster.

  12. 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

  13. Using Semantic Web Technologies for Cohort Identification from Electronic Health Records for Clinical Research

    PubMed Central

    Pathak, Jyotishman; Kiefer, Richard C.; Chute, Christopher G.

    2012-01-01

    The ability to conduct genome-wide association studies (GWAS) has enabled new exploration of how genetic variations contribute to health and disease etiology. One of the key requirements to perform GWAS is the identification of subject cohorts with accurate classification of disease phenotypes. In this work, we study how emerging Semantic Web technologies can be applied in conjunction with clinical data stored in electronic health records (EHRs) to accurately identify subjects with specific diseases for inclusion in cohort studies. In particular, we demonstrate the role of using Resource Description Framework (RDF) for representing EHR data and enabling federated querying and inferencing via standardized Web protocols for identifying subjects with Diabetes Mellitus. Our study highlights the potential of using Web-scale data federation approaches to execute complex queries. PMID:22779040

  14. The "epic" challenge of optimizing antimicrobial stewardship: the role of electronic medical records and technology.

    PubMed

    Kullar, Ravina; Goff, Debra A; Schulz, Lucas T; Fox, Barry C; Rose, Warren E

    2013-10-01

    Antimicrobial stewardship programs (ASPs) are established means for institutions to improve patient outcomes while reducing the emergence of resistant bacteria. With the increased adoption and evolution of electronic medical records (EMRs), there is a need to assimilate the tools of ASPs into EMRs, using decision support and feedback. Third-party software vendors provide the mainstay for integration of individual institutional EMR and ASP efforts. Epic is the leading implementer of EMR technology in the United States. A collaboration of physicians and pharmacists are working closely with Epic to provide a more comprehensive platform of ASP tools that may be institutionally individualized. We review the historical relationship between ASPs and the EMR, cite examples of Epic stewardship tools from 3 academic medical centers' ASPs, discuss limitations of these Epic tools, and conclude with the current process in evolution to integrate ASP tools and decision support capacities directly into Epic's EMR. PMID:23667260

  15. Using semantic web technologies for cohort identification from electronic health records for clinical research.

    PubMed

    Pathak, Jyotishman; Kiefer, Richard C; Chute, Christopher G

    2012-01-01

    The ability to conduct genome-wide association studies (GWAS) has enabled new exploration of how genetic variations contribute to health and disease etiology. One of the key requirements to perform GWAS is the identification of subject cohorts with accurate classification of disease phenotypes. In this work, we study how emerging Semantic Web technologies can be applied in conjunction with clinical data stored in electronic health records (EHRs) to accurately identify subjects with specific diseases for inclusion in cohort studies. In particular, we demonstrate the role of using Resource Description Framework (RDF) for representing EHR data and enabling federated querying and inferencing via standardized Web protocols for identifying subjects with Diabetes Mellitus. Our study highlights the potential of using Web-scale data federation approaches to execute complex queries. PMID:22779040

  16. Novel acoustic technology for studying free-ranging shark social behaviour by recording individuals' interactions.

    PubMed

    Guttridge, Tristan L; Gruber, Samuel H; Krause, Jens; Sims, David W

    2010-01-01

    Group behaviours are widespread among fish but comparatively little is known about the interactions between free-ranging individuals and how these might change across different spatio-temporal scales. This is largely due to the difficulty of observing wild fish groups directly underwater over long enough time periods to quantify group structure and individual associations. Here we describe the use of a novel technology, an animal-borne acoustic proximity receiver that records close-spatial associations between free-ranging fish by detection of acoustic signals emitted from transmitters on other individuals. Validation trials, held within enclosures in the natural environment, on juvenile lemon sharks Negaprion brevirostris fitted with external receivers and transmitters, showed receivers logged interactions between individuals regularly when sharks were within 4 m ( approximately 4 body lengths) of each other, but rarely when at 10 m distance. A field trial lasting 17 days with 5 juvenile lemon sharks implanted with proximity receivers showed one receiver successfully recorded association data, demonstrating this shark associated with 9 other juvenile lemon sharks on 128 occasions. This study describes the use of acoustic underwater proximity receivers to quantify interactions among wild sharks, setting the scene for new advances in understanding the social behaviours of marine animals. PMID:20174465

  17. Novel Acoustic Technology for Studying Free-Ranging Shark Social Behaviour by Recording Individuals' Interactions

    PubMed Central

    Guttridge, Tristan L.; Gruber, Samuel H.; Krause, Jens; Sims, David W.

    2010-01-01

    Group behaviours are widespread among fish but comparatively little is known about the interactions between free-ranging individuals and how these might change across different spatio-temporal scales. This is largely due to the difficulty of observing wild fish groups directly underwater over long enough time periods to quantify group structure and individual associations. Here we describe the use of a novel technology, an animal-borne acoustic proximity receiver that records close-spatial associations between free-ranging fish by detection of acoustic signals emitted from transmitters on other individuals. Validation trials, held within enclosures in the natural environment, on juvenile lemon sharks Negaprion brevirostris fitted with external receivers and transmitters, showed receivers logged interactions between individuals regularly when sharks were within 4 m (∼4 body lengths) of each other, but rarely when at 10 m distance. A field trial lasting 17 days with 5 juvenile lemon sharks implanted with proximity receivers showed one receiver successfully recorded association data, demonstrating this shark associated with 9 other juvenile lemon sharks on 128 occasions. This study describes the use of acoustic underwater proximity receivers to quantify interactions among wild sharks, setting the scene for new advances in understanding the social behaviours of marine animals. PMID:20174465

  18. Crack instability of ferroelectric solids under alternative electric loading

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

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

  19. 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.

  20. 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.

  1. 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)

    1997-01-01

    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.

  2. Applying semantic web technologies for phenome-wide scan using an electronic health record linked Biobank

    PubMed Central

    2012-01-01

    Background The ability to conduct genome-wide association studies (GWAS) has enabled new exploration of how genetic variations contribute to health and disease etiology. However, historically GWAS have been limited by inadequate sample size due to associated costs for genotyping and phenotyping of study subjects. This has prompted several academic medical centers to form “biobanks” where biospecimens linked to personal health information, typically in electronic health records (EHRs), are collected and stored on a large number of subjects. This provides tremendous opportunities to discover novel genotype-phenotype associations and foster hypotheses generation. Results In this work, we study how emerging Semantic Web technologies can be applied in conjunction with clinical and genotype data stored at the Mayo Clinic Biobank to mine the phenotype data for genetic associations. In particular, we demonstrate the role of using Resource Description Framework (RDF) for representing EHR diagnoses and procedure data, and enable federated querying via standardized Web protocols to identify subjects genotyped for Type 2 Diabetes and Hypothyroidism to discover gene-disease associations. Our study highlights the potential of Web-scale data federation techniques to execute complex queries. Conclusions This study demonstrates how Semantic Web technologies can be applied in conjunction with clinical data stored in EHRs to accurately identify subjects with specific diseases and phenotypes, and identify genotype-phenotype associations. PMID:23244446

  3. Using Technology to Improve Cancer Care: Social Media, Wearables, and Electronic Health Records.

    PubMed

    Fisch, Michael J; Chung, Arlene E; Accordino, Melissa K

    2016-01-01

    Digital engagement has become pervasive in the delivery of cancer care. Internet- and cellular phone-based tools and systems are allowing large groups of people to engage with each other and share information. Health systems and individual health professionals are adapting to this revolution in consumer and patient behavior by developing ways to incorporate the benefits of technology for the purpose of improving the quality of medical care. One example is the use of social media platforms by oncologists to foster interaction with each other and to participate with the lay public in dialogue about science, medicine, and cancer care. In addition, consumer devices and sensors (wearables) have provided a new, growing dimension of digital engagement and another layer of patient-generated health data to foster better care and research. Finally, electronic health records have become the new standard for oncology care delivery, bringing new opportunities to measure quality in real time and follow practice patterns, as well as new challenges as providers and patients seek ways to integrate this technology along with other forms of digital engagement to produce more satisfaction in the process of care along with measurably better outcomes. PMID:27249700

  4. High photovoltages in ferroelectric ceramics

    NASA Technical Reports Server (NTRS)

    Brody, P. S.

    1976-01-01

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

  5. 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.

  6. Quasi-two-dimensional ferroelectricity in KNbO3/KTaO3 superlattices

    NASA Astrophysics Data System (ADS)

    Lebedev, A. I.

    2011-12-01

    First-principles density functional theory is used to calculate the phonon spectrum in the paraelectric phase, the ground-state structure and polarization distribution in the polar phase, and energies of ferro- and antiferroelectrically ordered phases of free-standing (KNbO3)1(KTaO3) n ferroelectric superlattices with n = 1-7. It is established that quasi-two-dimensional ferroelectricity with polarization oriented in the layer plane, which weakly interacts with polarization in neighboring layers, appears in potassium niobate layers with a thickness of one unit cell in the superlattices. The possibility of using of such ferroelectric superlattices as a medium for three-dimensional information recording is shown.

  7. Negative capacitance in multidomain ferroelectric superlattices.

    PubMed

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

    2016-06-23

    The stability of spontaneous electrical polarization in ferroelectrics is fundamental to many of their current applications, which range from the simple electric cigarette lighter to non-volatile random access memories. Research on nanoscale ferroelectrics reveals that their behaviour is profoundly different from that in bulk ferroelectrics, which could lead to new phenomena with potential for future devices. As ferroelectrics become thinner, maintaining a stable polarization becomes increasingly challenging. On the other hand, intentionally destabilizing this polarization can cause the effective electric permittivity of a ferroelectric to become negative, enabling it to behave as a negative capacitance when integrated in a heterostructure. Negative capacitance has been proposed as a way of overcoming fundamental limitations on the power consumption of field-effect transistors. However, experimental demonstrations of this phenomenon remain contentious. The prevalent interpretations based on homogeneous polarization models are difficult to reconcile with the expected strong tendency for domain formation, but the effect of domains on negative capacitance has received little attention. Here we report negative capacitance in a model system of multidomain ferroelectric-dielectric superlattices across a wide range of temperatures, in both the ferroelectric and paraelectric phases. Using a phenomenological model, we show that domain-wall motion not only gives rise to negative permittivity, but can also enhance, rather than limit, its temperature range. Our first-principles-based atomistic simulations provide detailed microscopic insight into the origin of this phenomenon, identifying the dominant contribution of near-interface layers and paving the way for its future exploitation. PMID:27296225

  8. New perspectives for ferroelectric LC-polymers

    SciTech Connect

    Brehmer, M.; Gebhard, E.; Wittig, T.

    1996-10-01

    LC-Elastomers prepared from ferroelectric LC-polymers are interesting materials for two reasons. From a materials point of view they are interesting because of their ferroelectric, piezoelectric and pyrroelectric properties. From a scientific point of view they are fascinating because they allow us to study the interplay of electric and mechanical forces in a rubbery material The coupling between the director reorientation and the network can be modified by crosslinking at the end of the mesogens or in the range of the polymer chains . In the last case the coupling is minimal. Besides the planar orientation in SSFLC-cells, free standing films offer the possibility of a homeotropic alignment of smectic liquid crystals ferroelectric LC elastomers of a different topology can be obtained by mixing a low molar mass or an oligomeric ferroelectric LC with a bifunctional crosslinkable: liquid crystal and performing photochemically a crosslinking reaction in one switching state of the smectic C* phase. As a result non crosslinkable ferroelectric LC will form micro-droplets surrounded by a densely crosslinked network, which is formed by the crosslinked non-ferroelectric liquid crystals. This gives a two phasic Volume or Network Stabilized Ferroelectric Liquid Crystal.

  9. 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.

  10. Ultrafast Photovoltaic Response in Ferroelectric Nanolayers

    SciTech Connect

    Daranciang, Dan

    2012-02-15

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

  11. Strong ultrasonic microwaves in ferroelectric ceramics.

    PubMed

    Arlt, G

    1998-01-01

    It is well known that ferroelectric materials have piezoelectric properties which allow the transformation of electrical signals into mechanical signals and vice versa. The transducer action normally is restricted to frequencies up to the mechanical resonance frequency of the sample. There are, however, two mechanisms which allow transducer action in ferroelectric ceramics at much higher frequencies: one is the normal piezoelectric effect in a ferroelectric ceramic in which the crystallites have periodic domain structures, the other is a domain wall effect in which ferroelastic domain walls in a periodic domain structure are powerful shear wave emitters. Both mechanisms give rise to extensive dielectric losses in ceramics at microwave frequencies. PMID:18244152

  12. Ferroelectric ceramics in a pyroelectric accelerator

    SciTech Connect

    Shchagin, A. V.; Miroshnik, V. S.; Volkov, V. I.; Oleinik, A. N.

    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.

  13. Emission from ferroelectric cathodes. Revision 1

    SciTech Connect

    Sampayan, S.E.; Caporaso, G.J.; Holmes, C.L.; Lauer, E.J.; Prosnitz, D.; Trimble, D.O.; Westenskow, G.A.

    1993-05-01

    The authors have recently initiated an investigation of electron emission from ferroelectric cathodes. The experimental apparatus consisted of an electron diode and a 250 kV, 12 ohm, 70 ns pulsed high voltage power source. A planar triode modulator driven by a synthesized waveform generator initiates the polarization inversion and allows inversion pulse tailoring. The pulsed high voltage power source is capable of delivering two high voltage pulses within 50 {mu}s of each other and is capable of operating at a sustained repetition rate of 5 Hz. The initial measurements indicate that emission current densities above the Child-Langmuir Space Charge Limit, J{sub CL}, are possible. They explain this effect to be based on a non-zero initial energy of the emitted electrons. They also determined that this effect is strongly coupled to relative timing between the inversion pulse and application of the main anode-cathode pulse. They also have initiated brightness measurements of the emitted beam and estimate a preliminary lower bound to be on the order of 10{sup 9} A/m{sup 2}-rad{sup 2} for currents close to J{sub CL} and factor of two less at currents over 4J{sub CL}. As in previous measurements at this Laboratory, they performed the measurement using a pepper pot technique. Beamlet profiles are recorded with a fast phosphor and gated cameras. They describe their apparatus and preliminary measurements.

  14. 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.

  15. Ionic field effect and memristive phenomena in single-point ferroelectric domain switching

    SciTech Connect

    Ievlev, Anton; Morozovska, A. N.; Eliseev, E. A.; Shur, Vladimir Ya.; Kalinin, Sergei V

    2014-01-01

    Electric field induced polarization switching underpins most functional applications of ferroelectric materials in information technology, materials science, and optoelectronics. In the last 20 years, much attention has been focused on the switching of individual domains using scanning probe microscopy, both as model of ferroelectric data storage and approach to explore fundamental physics of ferroelectric switching. The classical picture of tip induced switching includes formation of cylindrical domain oriented along the tip field, with the domain size is largely determined by the tip-induced field distribution and domain wall motion kinetics. The polarization screening is recognized as a necessary precondition to the stability of ferroelectric phase; however, screening processes are generally considered to be uniformly efficient and not leading to changes in switching behavior. Here, we demonstrate that single-point tip-induced polarization switching can give rise to a surprisingly broad range of domain morphologies, including radial and angular instabilities. These behaviors are traced to the surface screening charge dynamics, which in some cases can even give rise to anomalous switching against the electric field (ionic field effect). The implications of these behaviors for ferroelectric materials and devices are discussed.

  16. 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. PMID:26132841

  17. Economic externalities of health information technology. A game theoretic model for electronic health record adoption.

    PubMed

    Woodside, Joseph M

    2007-01-01

    A presidential executive order in 2004 called for widespread adoption of electronic health records within 10 years. Proponents have shown this will lead to safe, affordable and consumer-oriented healthcare. Current EHR adoption has not kept pace; some estimates suggest that EHR adoption will occur over a significantly longer period. Implementation costs and return on investment are listed, among other reasons, as the predominant factors limiting rapid adoption. A widespread EHR adoption plateau is expected, with entities being unable or unwilling to adopt EHRs. This will lead to incentive-based requirements to achieve widespread adoption and the full potential of EHRs. This paper looks at externalities of health information technology between the major entities--payors, providers and consumers. These externalities necessitate implementation of incentive-based programs to achieve benefit equilibrium. Game theory is employed to model the behavior of these entities to capture the most equitable outcome. Prescriptive analysis is utilized to interpret and suggest optimal adoption behavior. PMID:19195278

  18. Automation of Presentation Record Production Based on Rich-Media Technology Using SNT Petri Nets Theory

    PubMed Central

    Martiník, Ivo

    2015-01-01

    Rich-media describes a broad range of digital interactive media that is increasingly used in the Internet and also in the support of education. Last year, a special pilot audiovisual lecture room was built as a part of the MERLINGO (MEdia-rich Repository of LearnING Objects) project solution. It contains all the elements of the modern lecture room determined for the implementation of presentation recordings based on the rich-media technologies and their publication online or on-demand featuring the access of all its elements in the automated mode including automatic editing. Property-preserving Petri net process algebras (PPPA) were designed for the specification and verification of the Petri net processes. PPPA does not need to verify the composition of the Petri net processes because all their algebraic operators preserve the specified set of the properties. These original PPPA are significantly generalized for the newly introduced class of the SNT Petri process and agent nets in this paper. The PLACE-SUBST and ASYNC-PROC algebraic operators are defined for this class of Petri nets and their chosen properties are proved. The SNT Petri process and agent nets theory were significantly applied at the design, verification, and implementation of the programming system ensuring the pilot audiovisual lecture room functionality. PMID:26258164

  19. TaN interface properties and electric field cycling effects on ferroelectric Si-doped HfO2 thin films

    NASA Astrophysics Data System (ADS)

    Lomenzo, Patrick D.; Takmeel, Qanit; Zhou, Chuanzhen; Fancher, Chris M.; Lambers, Eric; Rudawski, Nicholas G.; Jones, Jacob L.; Moghaddam, Saeed; Nishida, Toshikazu

    2015-04-01

    Ferroelectric HfO2-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 HfO2 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 HfO2 thin films, the chemical interface properties of sputtered TaN bottom and top electrodes are probed with x-ray photoelectron spectroscopy. Ta-O 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 HfO2 thin films with pinched hysteresis loops and is shown to be influenced by the internal electric field.

  20. Optically controlled electroresistance and electrically controlled photovoltage in ferroelectric tunnel junctions

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

    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.

  1. Novel Capacitor Structure Using Sidewall Spacer for Highly Reliable Ferroelectric Random Access Memory Device

    NASA Astrophysics Data System (ADS)

    Kim, Hyun-Ho; Park, Jung-Hoon; Song, Yoon-Jong; Jang, Nak-Won; Joo, Heung-Jin; Kang, Seung-Kuk; Joo, Seok-Ho; Lee, Sung-Young; Kim, Kinam

    2004-04-01

    Since ferroelectric capacitors prepared by 1-mask etching are degraded after the etching, we systematically investigated the origin of the degradation. It was found that the major degradation originates from the formation of the nonstoichiometric and amorphorized Pb(ZrxTi1-x)O3 (PZT) layer on the sidewall of the PZT film during etching of the bottom electrode (BE). Therefore, to eliminate the undesired etch-damaged layer, we developed a novel etching technology using a ferroelectric (FE) sidewall spacer, which results in the enhancement of the remnant polarization after completing the capacitor etching process. Using the novel FE sidewall spacer, the sensing margin of bit-line-developed voltage was improved to 400 mV, which can guarantee highy reliable high-density ferroelectric random access memory (FRAM) devices.

  2. Optically controlled electroresistance and electrically controlled photovoltage in ferroelectric tunnel junctions.

    PubMed

    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 10(5). 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

  3. 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

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

    PubMed Central

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

    2013-01-01

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

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

    SciTech Connect

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

    2007-01-01

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

  6. Interface control of bulk ferroelectric polarization

    PubMed Central

    Yu, P.; Luo, W.; Yi, D.; Zhang, J. X.; Rossell, M. D.; Yang, C.-H.; You, L.; Singh-Bhalla, G.; Yang, S. Y.; He, Q.; Ramasse, Q. M.; Erni, R.; Martin, L. W.; Chu, Y. H.; Pantelides, S. T.; Pennycook, S. J.; Ramesh, R.

    2012-01-01

    The control of material interfaces at the atomic level has led to novel interfacial properties and functionalities. In particular, the study of polar discontinuities at interfaces between complex oxides lies at the frontier of modern condensed matter research. Here we employ a combination of experimental measurements and theoretical calculations to demonstrate the control of a bulk property, namely ferroelectric polarization, of a heteroepitaxial bilayer by precise atomic-scale interface engineering. More specifically, the control is achieved by exploiting the interfacial valence mismatch to influence the electrostatic potential step across the interface, which manifests itself as the biased-voltage in ferroelectric hysteresis loops and determines the ferroelectric state. A broad study of diverse systems comprising different ferroelectrics and conducting perovskite underlayers extends the generality of this phenomenon. PMID:22647612

  7. 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

    2011-02-01

    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. PMID:21247184

  8. Thermally tunable ferroelectric thin film photonic crystals.

    SciTech Connect

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

    2008-01-01

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

  9. Graduate Employment Outcomes for Qualifying Library and Records Management Courses at Curtin University of Technology, 1998-2002

    ERIC Educational Resources Information Center

    Genoni, Paul; Smith, Kerry

    2005-01-01

    This paper reports on the results of a survey of destinations for students from librarianship and records management courses at Curtin University of Technology for the period 1998-2002. The survey includes the type of work currently being undertaken by graduates, the security of tenure in their position, the level of professionalism in their…

  10. The 10 to the 8th power bit solid state spacecraft data recorder. [utilizing bubble domain memory technology

    NASA Technical Reports Server (NTRS)

    Murray, G. W.; Bohning, O. D.; Kinoshita, R. Y.; Becker, F. J.

    1979-01-01

    The results are summarized of a program to demonstrate the feasibility of Bubble Domain Memory Technology as a mass memory medium for spacecraft applications. The design, fabrication and test of a partially populated 10 to the 8th power Bit Data Recorder using 100 Kbit serial bubble memory chips is described. Design tradeoffs, design approach and performance are discussed. This effort resulted in a 10 to the 8th power bit recorder with a volume of 858.6 cu in and a weight of 47.2 pounds. The recorder is plug reconfigurable, having the capability of operating as one, two or four independent serial channel recorders or as a single sixteen bit byte parallel input recorder. Data rates up to 1.2 Mb/s in a serial mode and 2.4 Mb/s in a parallel mode may be supported. Fabrication and test of the recorder demonstrated the basic feasibility of Bubble Domain Memory technology for such applications. Test results indicate the need for improvement in memory element operating temperature range and detector performance.

  11. An epitaxial ferroelectric tunnel junction on silicon.

    PubMed

    Li, Zhipeng; Guo, Xiao; Lu, Hui-Bin; Zhang, Zaoli; Song, Dongsheng; Cheng, Shaobo; Bosman, Michel; Zhu, Jing; Dong, Zhili; Zhu, Weiguang

    2014-11-12

    Epitaxially grown functional perovskites on silicon (001) and the ferroelectricity of a 3.2 nm thick BaTiO3 barrier layer are demonstrated. The polarization-switching-induced change in tunneling resistance is measured to be two orders of magnitude. The obtained results suggest the possibility of integrating ferroelectric tunnel junctions as binary data storage media in non-volatile memory cells on a silicon platform. PMID:25200550

  12. Multiscale dynamics in relaxor ferroelectrics

    NASA Astrophysics Data System (ADS)

    Toulouse, Jean; Cai, L.; Pattnaik, R. K.; Boatner, L. A.

    2014-01-01

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

  13. Negative Capacitance transients in a ferroelectric capacitor

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

    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 phase transition, could provide a solution, but a direct measurement of negative capacitance has so far been elusive. Here we demonstrate the negative differential capacitance in a thin, single crystalline ferroelectric film, by constructing a simple R-C network and monitoring the voltage dynamics across the ferroelectric capacitor6. 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. The results are analyzed on the basis of the Landau-Khalatnikov equation, which shows that as the ferroelectric polarization switches its direction, it passes through the unstable negative capacitance region resulting in the characteristic ``negative capacitance transients.'' Analysis of this ``inductance''-like behavior from a capacitor allows us to calculate the value of the negative capacitance directly and presents an unprecedented insight into the intrinsic energy profile of the ferroelectric material.

  14. Negative Capacitance in a Ferroelectric Capacitor

    NASA Astrophysics Data System (ADS)

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

    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 phase transition, could provide a solution, but a direct measurement of negative capacitance has so far been elusive. Here we demonstrate the negative differential capacitance in an epitaxial ferroelectric film, by constructing a simple R-C network and monitoring the voltage dynamics across the ferroelectric capacitor. 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. The results are analyzed on the basis of the Landau-Khalatnikov equation, which shows that as the ferroelectric polarization switches its direction, it passes through the unstable negative capacitance region. Analysis of this behavior from a capacitor presents an unprecedented insight into the intrinsic energy profile of the ferroelectric material.

  15. 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.

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

    SciTech Connect

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

    2010-09-01

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

  17. Synthesis, deposition and characterization of ferroelectric films for electrooptic devices

    NASA Astrophysics Data System (ADS)

    Tunaboylu, Bahadir

    The use of integrable ferroelectric electro-optic thin films is a revolutionary approach in the development of high-speed, low-voltage and high-contrast ratio integrated electro-optic spatial light modulators (SLM) for free-space optoelectronic interconnects. Thin films offer improved performance over bulk ferroelectric (FE) materials because of their lower modulator capacitance and operation at high speeds with low switching energies. Integration of ferroelectric thin films with silicon technology will also impact both the uncooled infrared sensor and dynamic and nonvolatile memory technologies. Ferroelectrics such as lead lanthanum zirconate titanate (PLZT) and patassium tantalate niobate (KTN) present great potential for SLMs due to their large electro-optic (EO) effect in the bulk form. The development of thin-film SLMs require electro-optic films of high optical quality with good dielectric and EO properties. High quality thin films of PLZT and KTN were deposited using RF magnetron sputtering on r-plane sapphire substrates which offer integration capability with semiconductor devices. PLZT films with extremely large peak dielectric constant, 2800 at the Curie temperature of 180sp°C, were achieved with remarkably low dissipation loss factor <0.04. The dielectric frequency dispersion was determined to be very small up to 1 Mhz. Also, the absorption of the light in the films was very low. A giant effective quadratic electrooptic effect was demonstrated in PLZT films. These results represent a huge leap forward for the FE-SLM technology with respect to the goal of fully integrated thin film electrooptic light modulators. Microstructural development and phase transformation kinetics in PLZT films were also analyzed for the first time and are presented here. Energy required for the formation of desirable perovskite phase was determined to be 322 kJ/mol. Single-phase PLZT films with larger average grain size showed higher dielectric constants and better EO

  18. Exploring Healthcare Consumer Acceptance of Personal Health Information Management Technology through Personal Health Record Systems

    ERIC Educational Resources Information Center

    Wu, Huijuan

    2013-01-01

    Healthcare technologies are evolving from a practitioner-centric model to a patient-centric model due to the increasing need for technology that directly serves healthcare consumers, including healthy people and patients. Personal health information management (PHIM) technology is one of the technologies designed to enhance an individual's ability…

  19. Application of video recording technology to improve husbandry and reproduction in the carmine bee-eater (Merops n. nubicus).

    PubMed

    Ferrie, Gina M; Sky, Christy; Schutz, Paul J; Quinones, Glorieli; Breeding, Shawnlei; Plasse, Chelle; Leighty, Katherine A; Bettinger, Tammie L

    2016-01-01

    Incorporating technology with research is becoming increasingly important to enhance animal welfare in zoological settings. Video technology is used in the management of avian populations to facilitate efficient information collection on aspects of avian reproduction that are impractical or impossible to obtain through direct observation. Disney's Animal Kingdom(®) maintains a successful breeding colony of Northern carmine bee-eaters. This African species is a cavity nester, making their nesting behavior difficult to study and manage in an ex situ setting. After initial research focused on developing a suitable nesting environment, our goal was to continue developing methods to improve reproductive success and increase likelihood of chicks fledging. We installed infrared bullet cameras in five nest boxes and connected them to a digital video recording system, with data recorded continuously through the breeding season. We then scored and summarized nesting behaviors. Using remote video methods of observation provided much insight into the behavior of the birds in the colony's nest boxes. We observed aggression between birds during the egg-laying period, and therefore immediately removed all of the eggs for artificial incubation which completely eliminated egg breakage. We also used observations of adult feeding behavior to refine chick hand-rearing diet and practices. Although many video recording configurations have been summarized and evaluated in various reviews, we found success with the digital video recorder and infrared cameras described here. Applying emerging technologies to cavity nesting avian species is a necessary addition to improving management in and sustainability of zoo avian populations. PMID:26661620

  20. Integration and Electrical Properties of Novel Ferroelectric Capacitors for 0.25 μm 1 Transistor 1 Capacitor Ferroelectric Random Access Memory (1T1C FRAM)

    NASA Astrophysics Data System (ADS)

    Song, Y. J.; Jang, N. W.; Jung, D. J.; Kim, H. H.; Joo, H. J.; Lee, S. Y.; Lee, K. M.; Joo, S. H.; Park, S. O.; Kim, Kinam

    2002-04-01

    Since the space margin between capacitors has been greatly reduced in 32 Mb high-density ferroelectric random access memory (FRAM) with a 0.25 μm design rule, considering the limitation of current etching technology, the stack height of ferroelectric capacitors should be minimized for stable node separation. In this paper, novel capacitors with a total thickness of 4000 Å were prepared using a seeding layer, low temperature processing, and optimal top electrode annealing. The 1000 Å Pb(Zr1-xTix)O3 (PZT) films showed excellent structural and ferroelectric properties such as strong (111) orientation and large remanent polarization of 40 μC/cm2. The low stack capacitors were then implemented into 0.6 μm and prototype 0.25 μm FRAM. Compared to a conventional capacitor stack, the ferroelectric capacitors exhibited adequate sensing margin of 250 fC, thus giving rise to a fully working die of 4 Mb FRAM. Therefore, it was clearly demonstrated that the novel capacitors can enable the realization of a high-density 32 Mb FRAM device with a 0.25 μm design rule.

  1. Highly Stable Etch Stopper Technology for 0.25 μm 1 Transistor 1 Capacitor (1T1C) 32 Mega-Bit Ferroelectric Random Access Memory (FRAM)

    NASA Astrophysics Data System (ADS)

    Jang, Nak-Won; Song, Yoon-Jong; Joo, Suk-Ho; Lee, Kyu-Mann; Kim, Hyun-Ho; Joo, Heung-Jin; Park, Jung-Hoon; Lee, Sang-Woo; Lee, Sung-Yung; Kim, Kinam

    2003-04-01

    Since current 32 Mb high-density ferroelectric random access memory (FRAM) shows very narrow sensing window, it is strongly desired to improve the sensing widow for generating a reliable high yield. In this paper, we propose a TiAlN oxygen stopping layer for enhancing the diffusion barrier layer, which makes it possible to reduce the bottom stack height from 180 nm to 90 nm, resulting in the increase of effective cell area and cell charge. In addition to the enhanced diffusion barrier, we developed a stable PE-SiN etch stopper for replacing Ir noble metal etch stopper that has strong stress variation and eventually deteriorates the cell charge distribution. By using TiAlN oxygen stopping layer and PE-SiN etch stopper, the 32 Mb FRAM device shows very wide sensing window of 100 fC, which guarantees a reliable high yield.

  2. Magnetic Recording.

    ERIC Educational Resources Information Center

    Lowman, Charles E.

    A guide to the technology of magnetic recorders used in such fields as audio recording, broadcast and closed-circuit television, instrumentation recording, and computer data systems is presented. Included are discussions of applications, advantages, and limitations of magnetic recording, its basic principles and theory of operation, and its…

  3. Influence of interfacial dislocations on hysteresis loops of ferroelectric films

    NASA Astrophysics Data System (ADS)

    Li, Y. L.; Hu, S. Y.; Choudhury, S.; Baskes, M. I.; Saxena, A.; Lookman, T.; Jia, Q. X.; Schlom, D. G.; Chen, L. Q.

    2008-11-01

    We investigated the influence of dislocations, located at the interface of a ferroelectric film and its underlying substrate, on the ferroelectric hysteresis loop including the remanent polarization and coercive field using phase-field simulations. We considered epitaxial ferroelectric BaTiO3 films and found that the hysteresis loop is strongly dependent on the type and density of interfacial dislocations. The dislocations that stabilize multiple ferroelectric variants and domains reduce the coercive field, and consequently, the corresponding remanent polarization also decreases.

  4. Scientific and Technological Information in Transactional Files in Government Records and Archives: A RAMP Study.

    ERIC Educational Resources Information Center

    Wimalaratne, K. D. G.

    This long-term Records and Archives Administration Programme (RAMP) study is designed to assist archivists, records managers, and information specialists in identifying for current use and possible archival selection those transactional or case files that contain scientific and technical information (STI), particularly in those instances where…

  5. Improving the Quality of Nursing Home Care and Medical-Record Accuracy with Direct Observational Technologies

    ERIC Educational Resources Information Center

    Schnelle, John F.; Osterweil, Dan; Simmons, Sandra F.

    2005-01-01

    Nursing home medical-record documentation of daily-care occurrence may be inaccurate, and information is not documented about important quality-of-life domains. The inadequacy of medical record data creates a barrier to improving care quality, because it supports an illusion of care consistent with regulations, which reduces the motivation and…

  6. Ferroelectric and dielectric properties of ferrite-ferroelectric ceramic composites

    SciTech Connect

    Elena Ciomaga, Cristina; Maria Neagu, Alexandra; Valentin Pop, Mihai; Mitoseriu, Liliana; Airimioaei, Mirela; Tascu, Sorin; Schileo, Giorgio; Galassi, Carmen

    2013-02-21

    Particulate composites of ferrite and ferroelectric phases with xNiFe{sub 2}O{sub 4} (NF) and (1 - x)Pb{sub 0.988}(Zr{sub 0.52}Ti{sub 0.48}){sub 0.976}Nb{sub 0.024}O{sub 3} (where x = 2, 10, 20, 30, 50, 70, and 100 wt. %) were prepared in situ by sol-gel method. The presence of a diphase composition was confirmed by X-ray diffraction while the microstructure of the composites was studied by scanning electron microscopy revealing a good mixing of the two phases and a good densification of the bulk ceramics. The dielectric permittivity shows usual dielectric dispersion behavior with increasing frequency due to Maxwell-Wagner interfacial polarization. AC conductivity measurements made in frequency range 1 Hz-1 MHz suggest that the conduction process is due to mixed polaron hopping. The effect of NF phase concentration on the P-E and M-H hysteresis behavior and dielectric properties of the composites was investigated. At low NF concentration a sharp ferro-paraelectric transition peak can be observed at around 360 Degree-Sign C while for higher NF concentrations a trend to a diffuse phase transition occurs. All the composite samples exhibit typical ferromagnetic hysteresis loops, indicating the presence of ordered magnetic structure.

  7. Applications of Domain Engineering in Ferroelectrics for Photonic Applications

    NASA Astrophysics Data System (ADS)

    Scrymgeour, D. A.

    The advent of the laser in the early 1960's brought a surge of interest in techniques to modify, deflect, and change the frequency of laser light. These functions are extensively used today in such technological applications as displays, telecommunications, analog to digital conversion, printing, and data storage devices. Of the many competing technologies, optical devices fabricated in ferroelectric materials like lithium niobate and lithium tantalate offer a versatile solid-state platform to do all of these functions integrated seamlessly in the same device. By patterning these crystals into periodic gratings, the wavelength of light can be converted to different wavelengths through nonlinear optical effects to create new laser sources not readily available. If the domains are patterned into the shape of lenses or prisms, light passing through the crystal can be focused and deflected through the electro-optic effect. By precisely creating the domain structures in ferroelectric crystals, these functions and others can be combined in a single device offering large design flexibility, compactness, and utility.

  8. 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.

  9. Charting the use of electronic health records and other information technologies among child health providers

    PubMed Central

    Menachemi, Nir; Ettel, Donna L; Brooks, Robert G; Simpson, Lisa

    2006-01-01

    Background Previous studies regarding the use of information technologies (IT) specifically among pediatricians and other physicians who treat children are lacking. As such, the objective of this study is to examine the use of electronic health record (EHR) systems and other IT applications among pediatricians and other child health providers (CHPs) in Florida. Methods We focus on pediatricians and other CHPs who responded to a state-wide physician survey of IT use. CHPs included general pediatricians, pediatric sub-specialists, and family physicians who self-reported a practice composition of at least 20% children. We compared general pediatricians to other CHPs and all CHPs (including pediatricians) to other physicians with respect to computer and internet availability, and to the use of personal digital assistants and EHRs. Those with an EHR were also compared regarding the availability of key functions available in their system. Statistical analyses included chi-square analysis and logistic regression models which controlled for numerous factors. Results A total of 4,203 surveys (28.2% response) including 1,021 CHPs, were returned. General pediatricians (13.7%) were significantly less likely to be using an EHR than both CHP family physicians (26.1%) and pediatric sub-specialists (29.6%; p < .001). In multivariate analysis, only general pediatricians were significantly less likely than other physicians to indicate the use of an EHR system (OR = .43; 95% C.I. = .29 – .64). Overall, CHPs were less likely to have key functions available in their EHR system including electronic prescribing (53.3% vs. 61.9%; p = .028), and electronic order entry (47.7% vs. 57.2%; p = .017) among others. General pediatricians and pediatric sub-specialists frequently lagged behind CHP family physicians with respect to key EHR functions. In contrast, CHPs had growth charts (51.3% vs. 24.0%; p < .001) and weight-based dosing functions (35.5% vs.22.7%; p < .001) more frequently than

  10. Strain-Induced Ferroelectric Topological Insulator.

    PubMed

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

    2016-03-01

    Ferroelectricity and band topology are two extensively studied yet distinct properties of insulators. Nonetheless, their coexistence has never been observed in a single material. Using first-principles calculations, we demonstrate that a noncentrosymmetric perovskite structure of CsPbI3 allows for the simultaneous presence of ferroelectric and topological orders with appropriate strain engineering. Metallic topological surface states create an intrinsic short-circuit condition, helping stabilize bulk polarization. Exploring diverse structural phases of CsPbI3 under pressure, we identify that the key structural feature for achieving a ferroelectric topological insulator is to suppress PbI6 cage rotation in the perovskite structure, which could be obtained via strain engineering. Ferroelectric control over the density of topological surface states provides a new paradigm for device engineering, such as perfect-focusing Veselago lens and spin-selective electron collimator. Our results suggest that CsPbI3 is a simple model system for ferroelectric topological insulators, enabling future studies exploring the interplay between conventional symmetry-breaking and topological orders and their novel applications in electronics and spintronics. PMID:26814668

  11. 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.

  12. Ferroelectric properties of niobium-doped strontium bismuth tantalate films

    NASA Astrophysics Data System (ADS)

    Golosov, D. A.; Zavadski, S. M.; Kolos, V. V.; Turtsevich, A. S.

    2016-01-01

    The characteristics of ferroelectric thin films of strontium bismuth tantalate (SBT) and niobium-doped strontium bismuth tantalate (SBTN) deposited by radio-frequency (RF) magnetron sputtering on Pt/TiO2/SiO2/Si substrates were investigated. For the formation of the structure of the ferroelectric material, the deposited films were subjected to a subsequent annealing at temperatures of 970-1070 K in an O2 atmosphere. The results of the X-ray diffraction analysis demonstrated that, in contrast to SBT films, in which the Aurivillius phase is formed only at annealing temperatures of 1050-1070 K, the formation of this phase in SBTN films is observed already at a temperature of 970 K. The dependences of the dielectric permittivity, remanent polarization, and coercive force of the SBT and SBTN films on the subsequent annealing conditions were determined. It was found that, upon doping of the SBT films with niobium, the remanent polarization increases by a factor of approximately three, the Curie temperature increases by 50 K, and the dielectric permittivity also increases. It was revealed that, in contrast to the SBT films, the polarization of the SBTN films is observed already at an annealing temperature of approximately 970 K. It was shown that the replacement of SBT films by SBTN films in the manufacture of high-density nonvolatile ferroelectric randomaccess memory (FeRAM) capacitor modules makes it possible to decrease the synthesis temperature from 1070 to 990-1000 K, which improves the compatibility with the planar technology of semiconductor devices. However, it turned out that an increase in the coercive field makes niobium-doped SBT films less attractive for the use in FeRAM.

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

    NASA Astrophysics Data System (ADS)

    Fan, Zhen; Chen, Jingsheng; Wang, John

    2016-05-01

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

  14. 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.

  15. Fabrication of ferroelectric polymer nanostructures on flexible substrates by soft-mold reverse nanoimprint lithography.

    PubMed

    Song, Jingfeng; Lu, Haidong; Li, Shumin; Tan, Li; Gruverman, Alexei; Ducharme, Stephen

    2016-01-01

    Conventional nanoimprint lithography with expensive rigid molds is used to pattern ferroelectric polymer nanostructures on hard substrate for use in, e.g., organic electronics. The main innovation here is the use of inexpensive soft polycarbonate molds derived from recordable DVDs and reverse nanoimprint lithography at low pressure, which is compatible with flexible substrates. This approach was implemented to produce regular stripe arrays with a spacing of 700 nm from vinylidene fluoride co trifluoroethylene ferroelectric copolymer on flexible polyethylene terephthalate substrates. The nanostructures have very stable and switchable piezoelectric response and good crystallinity, and are highly promising for use in organic electronics enhanced or complemented by the unique properties of the ferroelectric polymer, such as bistable polarization, piezoelectric response, pyroelectric response, or electrocaloric function. The soft-mold reverse nanoimprint lithography also leaves little or no residual layer, affording good isolation of the nanostructures. This approach reduces the cost and facilitates large-area, high-throughput production of isolated functional polymer nanostructures on flexible substrates for the increasing application of ferroelectric polymers in flexible electronics. PMID:26597076

  16. Fabrication of ferroelectric polymer nanostructures on flexible substrates by soft-mold reverse nanoimprint lithography

    NASA Astrophysics Data System (ADS)

    Song, Jingfeng; Lu, Haidong; Li, Shumin; Tan, Li; Gruverman, Alexei; Ducharme, Stephen

    2016-01-01

    Conventional nanoimprint lithography with expensive rigid molds is used to pattern ferroelectric polymer nanostructures on hard substrate for use in, e.g., organic electronics. The main innovation here is the use of inexpensive soft polycarbonate molds derived from recordable DVDs and reverse nanoimprint lithography at low pressure, which is compatible with flexible substrates. This approach was implemented to produce regular stripe arrays with a spacing of 700 nm from vinylidene fluoride co trifluoroethylene ferroelectric copolymer on flexible polyethylene terephthalate substrates. The nanostructures have very stable and switchable piezoelectric response and good crystallinity, and are highly promising for use in organic electronics enhanced or complemented by the unique properties of the ferroelectric polymer, such as bistable polarization, piezoelectric response, pyroelectric response, or electrocaloric function. The soft-mold reverse nanoimprint lithography also leaves little or no residual layer, affording good isolation of the nanostructures. This approach reduces the cost and facilitates large-area, high-throughput production of isolated functional polymer nanostructures on flexible substrates for the increasing application of ferroelectric polymers in flexible electronics.

  17. 2009 Mississippi Curriculum Framework: Postsecondary Health Information Technology. (Program CIP-51.0707-Medical Records Technology/Technician)

    ERIC Educational Resources Information Center

    Hoffman, Casey; Jones, Robin; McGuffee, Michelle; Scott, Nena

    2009-01-01

    As the world economy continues to evolve, businesses and industries must adopt new practices and processes in order to survive. Quality and cost control, work teams and participatory management, and an infusion of technology are transforming the way people work and do business. Employees are now expected to read, write, and communicate…

  18. Short range magnetic exchange interaction favors ferroelectricity

    PubMed Central

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

    2016-01-01

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

  19. Short range magnetic exchange interaction favors ferroelectricity

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

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

  20. Short range magnetic exchange interaction favors ferroelectricity.

    PubMed

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

    2016-01-01

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

  1. Optical Temperature Sensor Through Upconversion Emission from the Er3+ Doped SrBi8Ti7O27 Ferroelectrics

    NASA Astrophysics Data System (ADS)

    Zou, Hua; Wang, Xusheng; Hu, Yifeng; Zhu, Xiaoqing; Sui, Yongxing; Song, Zhitang

    2016-06-01

    Er doped SrBi8Ti7O27 (SBT) ferroelectric ceramics were prepared by a solid-state reaction technique. By Er doping, the intensive green upconversion emissions were recorded under 980 nm diode laser excitation with 20 mW. The fluorescence spectrum was investigated in the temperature range of 150-580 K. By the fluorescence intensity ratio technique, the green emission band was studied as a function of temperature with a maximum sensing sensitivity of 0.0028 at 510 K. These results indicate that the Er doped SBT ferroelectric ceramics are promising multifunctional sensing materials.

  2. Ferroelectric Cathodes in Transverse Magnetic Fields

    SciTech Connect

    Alexander Dunaevsky; Yevgeny Raitses; Nathaniel J. Fisch

    2002-07-29

    Experimental investigations of a planar ferroelectric cathode in a transverse magnetic field up to 3 kGs are presented. It is shown that the transverse magnetic field affects differently the operation of ferroelectric plasma cathodes in ''bright'' and ''dark'' modes in vacuum. In the ''bright'' mode, when the surface plasma is formed, the application of the transverse magnetic field leads to an increase of the surface plasma density. In the ''dark'' mode, the magnetic field inhibits the development of electron avalanches along the surface, as it does similarly in other kinds of surface discharges in the pre-breakdown mode.

  3. Switching Characteristics of Ferroelectric Transistor Inverters

    NASA Technical Reports Server (NTRS)

    Laws, Crystal; Mitchell, Coey; MacLeod, Todd C.; Ho, Fat D.

    2010-01-01

    This paper presents the switching characteristics of an inverter circuit using a ferroelectric field effect transistor, FeFET. The propagation delay time characteristics, phl and plh are presented along with the output voltage rise and fall times, rise and fall. The propagation delay is the time-delay between the V50% transitions of the input and output voltages. The rise and fall times are the times required for the output voltages to transition between the voltage levels V10% and V90%. Comparisons are made between the MOSFET inverter and the ferroelectric transistor inverter.

  4. Probing nanoscale ferroelectricity by ultraviolet Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Tenne, Dmitri

    2007-03-01

    Conventional vibrational spectroscopies operating in visible and infrared range fail to measure the phonon spectra of nanoscale ferroelectric structures because of extremely weak signals and the overwhelming substrate contribution. In this talk, application of ultraviolet (UV) Raman spectroscopy for studies of lattice dynamics and ferroelectric phase transitions in nanoscale ferroelectrics will be presented. We demonstrate that UV Raman spectroscopy is an effective technique allowing the observation of phonons and determination of the ferroelectric phase transition temperature (Tc) in nanoscale ferroelectrics, specifically, BaTiO3/SrTiO3 superlattices having the ferroelectric BaTiO3 layers as thin as 1 unit cell, and single BaTiO3 layers as thin as 4 nm. BaTiO3/SrTiO3 superlattices and ultrathin BaTiO3 films studied were grown by molecular beam epitaxy on SrTiO3 as well as GdScO3 and DyScO3 substrates. Excellent epitaxial quality and atomically abrupt interfaces are evidenced by X-ray diffraction and high resolution transmission electron microscopy. UV Raman results show that one-unit-cell thick BaTiO3 layers in BaTiO3/SrTiO3 superlattices are ferroelectric with the Tc as high as 250 K, and induce the polarization in much thicker SrTiO3 layers adjacent to them. The Tc in superlattices was tuned by hundreds of degrees from ˜170 to 650 K by varying the thicknesses of BaTiO3 and SrTiO3 layers. Using scandate substrates enables growth of superlattices with systematically changed coherent strain, thus allowing studying the stress effect on the ferroelectric phase transitions. UV Raman data are supported by the thermodynamic calculations of polarization in superlattices as a function of temperature. The work was done in collaboration with A. Soukiassian, W. Tian, D.G. Schlom, Y.L. Li, L.-Q. Chen, X.X. Xi (Pennsylvania State University), A. Bruchhausen, A. Fainstein (Centro Atomico Bariloche & Instituto Balseiro, Argentina), R. S. Katiyar (University of Puerto Rico), A

  5. New Dielectric Resonances in Mesoscopic Ferroelectrics

    NASA Astrophysics Data System (ADS)

    Pattnaik, R.; Toulouse, J.

    1997-12-01

    A new type of dielectric resonance has been observed in several mixed ferroelectrics, KTa1-xNbxO3 (KTN), K1-xLixTaO3 (KLT), and PbMg1/3Nb2/3O3 (PMN), also known as relaxor ferroelectrics. This resonance and its metastability (persistence over long periods of time) in KTN in the paraelectric phase provides clear evidence, in relaxors, for the presence of permanent polar nanoregions and strong polarization-strain coupling. The frequencies calculated from the elastic constant reveal the unexpected clamped nature of the resonance. These results point to the essential role of polar regions in the relaxor behavior.

  6. 95 GHz gyrotron with ferroelectric cathode.

    PubMed

    Einat, M; Pilossof, M; Ben-Moshe, R; Hirshbein, H; Borodin, D

    2012-11-01

    Ferroelectric cathodes were reported as a feasible electron source for microwave tubes. However, due to the surface plasma emission characterizing this cathode, operation of millimeter wave tubes based on it remains questionable. Nevertheless, the interest in compact high power sources of millimeter waves and specifically 95 GHz is continually growing. In this experiment, a ferroelectric cathode is used as an electron source for a gyrotron with the output frequency extended up to 95 GHz. Power above a 5 kW peak and ~0.5 μs pulses are reported; a duty cycle of 10% is estimated to be achievable. PMID:23215293

  7. First-principles study of interface doping in ferroelectric junctions

    PubMed Central

    Wang, Pin-Zhi; Cai, Tian-Yi; Ju, Sheng; Wu, Yin-Zhong

    2016-01-01

    Effect of atomic monolayer insertion on the performance of ferroelectric tunneling junction is investigated in SrRuO3/BaTiO3/SrRuO3 heterostrucutures. Based on first-principles calculations, the atomic displacement, orbital occupancy, and ferroelectric polarization are studied. It is found that the ferroelectricity is enhanced when a (AlO2)− monolayer is inserted between the electrode SRO and the barrier BTO, where the relatively high mobility of doped holes effectively screen ferroelectric polarization. On the other hand, for the case of (LaO)+ inserted layer, the doped electrons resides at the both sides of middle ferroelectric barrier, making the ferroelectricity unfavorable. Our findings provide an alternative avenue to improve the performance of ferroelectric tunneling junctions. PMID:27063704

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

    PubMed

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

    2015-06-23

    Ferroelectricity in functional materials remains one of the most fascinating areas of modern science in the past several decades. In the last several years, the rapid development of piezoresponse force microscopy (PFM) and spectroscopy revealed the presence of electromechanical hysteresis loops and bias-induced remnant polar states in a broad variety of materials including many inorganic oxides, polymers, and biosystems. In many cases, this behavior was interpreted as the ample evidence for ferroelectric nature of the system. Here, we systematically analyze PFM responses on ferroelectric and nonferroelectric materials and demonstrate that mechanisms unrelated to ferroelectricity can induce ferroelectric-like characteristics through charge injection and electrostatic forces on the tip. 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 the end, we apply the developed measurement protocols to an unknown ferroelectric material. PMID:26035634

  9. Carrier Density Modulation in Ge Heterostructure by Ferroelectric Switching

    SciTech Connect

    Ponath, Patrick; Fredrickson, Kurt; Posadas, Agham B.; Ren, Yuan; Vasudevan, Rama K.; Okatan, Mahmut Baris; Jesse, Stephen; Aoki, Toshihiro; McCartney, Martha; Smith, David J.; Kalinin, Sergei V.; Lai, Keji; Demkov, Alexander A.

    2015-01-14

    The development of nonvolatile logic through direct coupling of spontaneous ferroelectric polarization with semiconductor charge carriers is nontrivial, with many issues, including epitaxial ferroelectric growth, demonstration of ferroelectric switching, and measurable semiconductor modulation. Here we report a true ferroelectric field effect carrier density modulation in an underlying Ge(001) substrate by switching of the ferroelectric polarization in the epitaxial c-axis-oriented BaTiO3 (BTO) grown by molecular beam epitaxy (MBE) on Ge. Using density functional theory, we demonstrate that switching of BTO polarization results in a large electric potential change in Ge. Aberration-corrected electron microscopy confirms the interface sharpness, and BTO tetragonality. Electron-energy-loss spectroscopy (EELS) indicates the absence of any low permittivity interlayer at the interface with Ge. Using piezoelectric force microscopy (PFM), we confirm the presence of fully switchable, stable ferroelectric polarization in BTO that appears to be single domain. Using microwave impedance microscopy (MIM), we clearly demonstrate a ferroelectric field effect.

  10. 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%.

  11. Room Temperature Ferroelectricity in Ultrathin SnTe Films

    NASA Astrophysics Data System (ADS)

    Chang, Kai; Liu, Junwei; Lin, Haicheng; Zhao, Kun; Zhong, Yong; Ji, Shuai-Hua; He, Ke; Wang, Lili; Ma, Xucun; Fu, Liang; Chen, Xi; Xue, Qi-Kun

    2015-03-01

    The ultrathin SnTe films with several unit cell thickness grown on graphitized SiC(0001) surface have been studied by the scanning tunneling microscopy and spectroscopy (STM/S). The domain structures, local lattice distortion and the electronic band bending at film edges induced by the in-plane spontaneous polarization along < 110 > have been revealed at atomic scale. The experiments at variant temperature show that the Curie temperature Tc of the one unit cell thick (two atomic layers) SnTe film is as high as 280K, much higher than that of the bulk counterpart (~100K) and the 2-4 unit cell thick films even indicate robust ferroelectricity at room temperature. This Tc enhancement is attributed to the stress-free interface, larger electronic band gap and greatly reduced Sn vacancy concentration in the ultrathin films. The lateral domain size varies from several tens to several hundreds of nanometers, and the spontaneous polarization direction could be modified by STM tip. Those properties of ultrathin SnTe films show the potential application on ferroelectric devices. The work was financially supported by Ministry of Science and Technology of China, National Science Foundation and Ministry of Education of China.

  12. 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.

  13. Ultrafast acousto-optic mode conversion in optically birefringent ferroelectrics.

    PubMed

    Lejman, Mariusz; Vaudel, Gwenaelle; Infante, Ingrid C; Chaban, Ievgeniia; Pezeril, Thomas; Edely, Mathieu; Nataf, Guillaume F; Guennou, Mael; Kreisel, Jens; Gusev, Vitalyi E; Dkhil, Brahim; Ruello, Pascal

    2016-01-01

    The ability to generate efficient giga-terahertz coherent acoustic phonons with femtosecond laser makes acousto-optics a promising candidate for ultrafast light processing, which faces electronic device limits intrinsic to complementary metal oxide semiconductor technology. Modern acousto-optic devices, including optical mode conversion process between ordinary and extraordinary light waves (and vice versa), remain limited to the megahertz range. Here, using coherent acoustic waves generated at tens of gigahertz frequency by a femtosecond laser pulse, we reveal the mode conversion process and show its efficiency in ferroelectric materials such as BiFeO3 and LiNbO3. Further to the experimental evidence, we provide a complete theoretical support to this all-optical ultrafast mechanism mediated by acousto-optic interaction. By allowing the manipulation of light polarization with gigahertz coherent acoustic phonons, our results provide a novel route for the development of next-generation photonic-based devices and highlight new capabilities in using ferroelectrics in modern photonics. PMID:27492493

  14. Interface-induced nonswitchable domains in ferroelectric thin films

    NASA Astrophysics Data System (ADS)

    Han, Myung-Geun; Marshall, Matthew S. J.; Wu, Lijun; Schofield, Marvin A.; Aoki, Toshihiro; Twesten, Ray; Hoffman, Jason; Walker, Frederick J.; Ahn, Charles H.; Zhu, Yimei

    2014-08-01

    Engineering domains in ferroelectric thin films is crucial for realizing technological applications including non-volatile data storage and solar energy harvesting. Size and shape of domains strongly depend on the electrical and mechanical boundary conditions. Here we report the origin of nonswitchable polarization under external bias that leads to energetically unfavourable head-to-head domain walls in as-grown epitaxial PbZr0.2Ti0.8O3 thin films. By mapping electrostatic potentials and electric fields using off-axis electron holography and electron-beam-induced current with in situ electrical biasing in a transmission electron microscope, we show that electronic band bending across film/substrate interfaces locks local polarization direction and further produces unidirectional biasing fields, inducing nonswitchable domains near the interface. Presence of oxygen vacancies near the film surface, as revealed by electron-energy loss spectroscopy, stabilizes the charged domain walls. The formation of charged domain walls and nonswitchable domains reported in this study can be an origin for imprint and retention loss in ferroelectric thin films.

  15. 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

  16. 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.

  17. 36 CFR 1236.14 - What must agencies do to protect records against technological obsolescence?

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... must design and implement migration strategies to counteract hardware and software dependencies of... hardware and software in such a way as to retain the functionality and integrity of the electronic records... necessary conversion of storage media to provide compatibility with current hardware and software; and...

  18. Unit Record Equipment-Basic (Course Outline), Data Processing Technology: 8025.14.

    ERIC Educational Resources Information Center

    Dade County Public Schools, Miami, FL.

    This outline provides a guide for the instructor of unit record equipment at the tenth, eleventh, and twelfth grade levels. The first week is spent reviewing punched card principles, and the remaining hours are devoted to learning the purpose, operation, and principles of control panel wiring for the interpreter, reproducing punch, accounting…

  19. From "Mystery Train" to "Cyberspace Sadie": References to Technology in Blues Recordings, 1923-2003

    ERIC Educational Resources Information Center

    Cooper, B. Lee

    2006-01-01

    Over the past eight decades the lyrics of blues recordings have provided valuable insights into the opinions and feelings of singers and songwriters. Commentaries concerning workplace relations, self esteem, romantic involvements, financial security, clothing styles, alcohol use, religion, health, death, and other universal human issues have been…

  20. Patch-clamp recording in brain slices with improved slicer technology.

    PubMed

    Geiger, J R P; Bischofberger, J; Vida, I; Fröbe, U; Pfitzinger, S; Weber, H J; Haverkampf, K; Jonas, P

    2002-01-01

    The use of advanced patch-clamp recording techniques in brain slices, such as simultaneous recording from multiple neurons and recording from dendrites or presynaptic terminals, demands slices of the highest quality. In this context the mechanics of the tissue slicer are an important factor. Ideally, a tissue slicer should generate large-amplitude and high-frequency movements of the cutting blade in a horizontal axis, with minimal vibrations in the vertical axis. We developed a vibroslicer that fulfils these in part conflicting requirements. The oscillator is a permanent-magnet-coil-leaf-spring system. Using an auto-resonant mechano-electrical feedback circuit, large horizontal oscillations (up to 3 mm peak-to-peak) with high frequency ( approximately 90 Hz) are generated. To minimize vertical vibrations, an adjustment mechanism was employed that allowed alignment of the cutting edge of the blade with the major axis of the oscillation. A vibroprobe device was used to monitor vertical vibrations during adjustment. The system is based on the shading of the light path between a light-emitting diode (LED) and a photodiode. Vibroprobe monitoring revealed that the vibroslicer, after appropriate adjustment, generated vertical vibrations of <1 microm, significantly less than many commercial tissue slicers. Light- and electron-microscopic analysis of surface layers of slices cut with the vibroslicer showed that cellular elements, dendritic processes and presynaptic terminals are well preserved under these conditions, as required for patch-clamp recording from these structures. PMID:11810221

  1. Study of ferroelectric-thin-film thickness effects on metal-ferroelectric-SiO2-Si transistors

    NASA Astrophysics Data System (ADS)

    Lin, Yih-Yin; Singh, Jasprit

    2002-06-01

    This article examines the thickness effects of ferroelectric films on gate tunneling suppression and charge control in metal-ferroelectric-insulator-semiconductor field-effect transistors (MFISFETs). The formalism used is based on a blocking-layer model for the ferroelectric film and a self-consistent solution of the Poisson and Schrödinger equation. We show that with a polar ferroelectric the threshold voltage of the FET can be altered by controlling the ferroelectric film thickness. We also study the thickness dependence of the capacitance-voltage curve and the surface charge density and the effects of ferroelectric hysteresis. The tunneling probability and leakage current calculation in a MFISFET device are provided in this article. Ferroelectrics-based transistors show higher sheet charges and lower tunneling currents than oxide-based devices.

  2. An investigation of the effect of nurses’ technology readiness on the acceptance of mobile electronic medical record systems

    PubMed Central

    2013-01-01

    Background Adopting mobile electronic medical record (MEMR) systems is expected to be one of the superior approaches for improving nurses’ bedside and point of care services. However, nurses may use the functions for far fewer tasks than the MEMR supports. This may depend on their technological personality associated to MEMR acceptance. The purpose of this study is to investigate nurses’ personality traits in regard to technology readiness toward MEMR acceptance. Methods The study used a self-administered questionnaire to collect 665 valid responses from a large hospital in Taiwan. Structural Equation modeling was utilized to analyze the collected data. Results Of the four personality traits of the technology readiness, the results posit that nurses are optimistic, innovative, secure but uncomfortable about technology. Furthermore, these four personality traits were all proven to have a significant impact on the perceived ease of use of MEMR while the perceived usefulness of MEMR was significantly influenced by the optimism trait only. The results also confirmed the relationships between the perceived components of ease of use, usefulness, and behavioral intention in the Technology Acceptance Model toward MEMR usage. Conclusions Continuous educational programs can be provided for nurses to enhance their information technology literacy, minimizing their stress and discomfort about information technology. Further, hospital should recruit, either internally or externally, more optimistic nurses as champions of MEMR by leveraging the instrument proposed in this study. Besides, nurses’ requirements must be fully understood during the development of MEMR to ensure that MEMR can meet the real needs of nurses. The friendliness of user interfaces of MEMR and the compatibility of nurses’ work practices as these will also greatly enhance nurses’ willingness to use MEMR. Finally, the effects of technology personality should not be ignored, indicating that hospitals

  3. 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.

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

    PubMed

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

    2015-11-24

    The effect of a ferroelectric polarization field on the charge transport in a two-dimensional (2D) material was examined using a graphene monolayer on a hexagonal boron nitride (hBN) field-effect transistor (FET) fabricated using a ferroelectric single-crystal substrate, (1-x)[Pb(Mg1/3Nb2/3)O3]-x[PbTiO3] (PMN-PT). In this configuration, the intrinsic properties of graphene were preserved with the use of an hBN flake, and the influence of the polarization field from PMN-PT could be distinguished. During a wide-range gate-voltage (VG) sweep, a sharp inversion of the spontaneous polarization affected the graphene channel conductance asymmetrically as well as an antihysteretic behavior. Additionally, a transition from antihysteresis to normal ferroelectric hysteresis occurred, depending on the V(G) sweep range relative to the ferroelectric coercive field. We developed a model to interpret the complex coupling among antihysteresis, current saturation, and sudden conductance variation in relation with the ferroelectric switching and the polarization-assisted charge trapping, which can be generalized to explain the combination of 2D structured materials with ferroelectrics. PMID:26487348

  5. Ferroelectric control of a Mott insulator

    PubMed Central

    Yamada, Hiroyuki; Marinova, Maya; Altuntas, Philippe; Crassous, Arnaud; Bégon-Lours, Laura; Fusil, Stéphane; Jacquet, Eric; Garcia, Vincent; Bouzehouane, Karim; Gloter, Alexandre; Villegas, Javier E.; Barthélémy, Agnès; Bibes, Manuel

    2013-01-01

    The electric field control of functional properties is an important goal in oxide-based electronics. To endow devices with memory, ferroelectric gating is interesting, but usually weak compared to volatile electrolyte gating. Here, we report a very large ferroelectric field-effect in perovskite heterostructures combining the Mott insulator CaMnO3 and the ferroelectric BiFeO3 in its “supertetragonal” phase. Upon polarization reversal of the BiFeO3 gate, the CaMnO3 channel resistance shows a fourfold variation around room temperature, and a tenfold change at ~200 K. This is accompanied by a carrier density modulation exceeding one order of magnitude. We have analyzed the results for various CaMnO3 thicknesses and explain them by the electrostatic doping of the CaMnO3 layer and the presence of a fixed dipole at the CaMnO3/BiFeO3 interface. Our results suggest the relevance of ferroelectric gates to control orbital- or spin-ordered phases, ubiquitous in Mott systems, and pave the way toward efficient Mott-tronics devices. PMID:24089020

  6. Ferroelectric polarization reversal in single crystals

    NASA Technical Reports Server (NTRS)

    Stadler, Henry L.

    1992-01-01

    Research on the reversal of polarization in ferroelectric crystals is reviewed. Particular attention is given to observation methods for polarization reversal, BaTiO3 polarization reversal, crystal thickness dependence of polarization reversal, and domain wall movement during polarization reversal in TGS.

  7. Large magnetocapacitance in electronic ferroelectric manganite systems

    SciTech Connect

    Chowdhury, Ujjal; Goswami, Sudipta; Bhattacharya, Dipten; Midya, Arindam; Mandal, P.; Das, Pintu; Mukovskii, Ya. M.

    2013-11-21

    We have observed a sizable positive magnetocapacitance (∼5%–90%) in perovskite Pr{sub 0.55}Ca{sub 0.45}MnO{sub 3} and bilayer Pr(Sr{sub 0.1}Ca{sub 0.9}){sub 2}Mn{sub 2}O{sub 7} system under 5 T magnetic field across 20–100 K below the magnetic transition point T{sub N}. The magnetodielectric effect, on the other hand, exhibits a crossover: (a) from positive to negative for the perovskite system and (b) from negative to positive for the bilayer system over the same temperature range. The bilayer Pr(Sr{sub 0.1}Ca{sub 0.9}){sub 2}Mn{sub 2}O{sub 7} system exhibits a sizable anisotropy as well. We have also noticed the influence of magnetic field on the dielectric relaxation characteristics of these systems. These systems belong to a class of improper ferroelectrics and are expected to exhibit charge/orbital order driven ferroelectric polarization below the transition point T{sub CO}. Large magnetocapacitance in these systems shows a typical multiferroic behavior even though the ferroelectric polarization is small in comparison to that of other ferroelectrics.

  8. Strain Tuning of Ferroelectric Thin Films *

    NASA Astrophysics Data System (ADS)

    Schlom, Darrell G.; Chen, Long-Qing; Eom, Chang-Beom; Rabe, Karin M.; Streiffer, Stephen K.; Triscone, Jean-Marc

    2007-08-01

    Predictions and measurements of the effect of biaxial strain on the properties of epitaxial ferroelectric thin films and superlattices are reviewed. Results for single-layer ferroelectric films of biaxially strained SrTiO3, BaTiO3, and PbTiO3 as well as PbTiO3/SrTiO3 and BaTiO3/SrTiO3 superlattices are described. Theoretical approaches, including first principles, thermodynamic analysis, and phase-field models, are applied to these biaxially strained materials, the assumptions and limitations of each technique are explained, and the predictions are compared. Measurements of the effect of biaxial strain on the paraelectric-to-ferroelectric transition temperature (TC) are shown, demonstrating the ability of percent-level strains to shift TC by hundreds of degrees in agreement with the predictions that predated such experiments. Along the way, important experimental techniques for characterizing the properties of strained ferroelectric thin films and superlattices, as well as appropriate substrates on which to grow them, are mentioned.

  9. Ferroelectric polarization reversal via successive ferroelastic transitions.

    PubMed

    Xu, Ruijuan; Liu, Shi; Grinberg, Ilya; Karthik, J; Damodaran, Anoop R; Rappe, Andrew M; Martin, Lane W

    2015-01-01

    Switchable polarization makes ferroelectrics a critical component in memories, actuators and electro-optic devices, and potential candidates for nanoelectronics. Although many studies of ferroelectric switching have been undertaken, much remains to be understood about switching in complex domain structures and in devices. In this work, a combination of thin-film epitaxy, macro- and nanoscale property and switching characterization, and molecular dynamics simulations are used to elucidate the nature of switching in PbZr(0.2)Ti(0.8)O3 thin films. Differences are demonstrated between (001)-/(101)- and (111)-oriented films, with the latter exhibiting complex, nanotwinned ferroelectric domain structures with high densities of 90° domain walls and considerably broadened switching characteristics. Molecular dynamics simulations predict both 180° (for (001)-/(101)-oriented films) and 90° multi-step switching (for (111)-oriented films) and these processes are subsequently observed in stroboscopic piezoresponse force microscopy. These results have implications for our understanding of ferroelectric switching and offer opportunities to change domain reversal speed. PMID:25344784

  10. Ferroelectric control of metal-insulator transition

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

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

  11. Ferroelectric Devices Emit Charged Particles and Radiation

    NASA Technical Reports Server (NTRS)

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

    2005-01-01

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

  12. Photovoltaics with Ferroelectrics: Current Status and Beyond.

    PubMed

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

    2016-07-01

    Ferroelectrics carry a switchable spontaneous electric polarization. This polarization is usually coupled to strain, making ferroelectrics good piezoelectrics. When coupled to magnetism, they become so-called multiferroic systems, a field that has been widely investigated since 2003. While ferroelectrics are birefringent and non-linear optically transparent materials, the coupling of polarization with optical properties has received, since 2009, renewed attention, triggered notably by low-bandgap ferroelectrics suitable for sunlight spectrum absorption and original photovoltaic effects. Consequently, power conversion efficiencies up to 8.1% were recently achieved and values of 19.5% were predicted, making photoferroelectrics promising photovoltaic alternatives. This article aims at providing an up-to-date review on this emerging and rapidly progressing field by highlighting several important issues and parameters, such as the role of domain walls, ways to tune the bandgap, consequences arising from the polarization switchability, and the role of defects and contact electrodes, as well as the downscaling effects. Beyond photovoltaicity, other polarization-related processes are also described, like light-induced deformation (photostriction) or light-assisted chemical reaction (photostriction). It is hoped that this overview will encourage further avenues to be explored and challenged and, as a byproduct, will inspire other research communities in material science, e.g., so-called hybrid halide perovskites. PMID:27135419

  13. Giant Electroresistive Ferroelectric Diode on 2DEG

    PubMed Central

    Kim, Shin-Ik; Jin Gwon, Hyo; Kim, Dai-Hong; Keun Kim, Seong; Choi, Ji-Won; Yoon, Seok-Jin; Jung Chang, Hye; Kang, Chong-Yun; Kwon, Beomjin; Bark, Chung-Wung; Hong, Seong-Hyeon; Kim, Jin-Sang; Baek, Seung-Hyub

    2015-01-01

    Manipulation of electrons in a solid through transmitting, storing, and switching is the fundamental basis for the microelectronic devices. Recently, the electroresistance effect in the ferroelectric capacitors has provided a novel way to modulate the electron transport by polarization reversal. Here, we demonstrate a giant electroresistive ferroelectric diode integrating a ferroelectric capacitor into two-dimensional electron gas (2DEG) at oxide interface. As a model system, we fabricate an epitaxial Au/Pb(Zr0.2Ti0.8)O3/LaAlO3/SrTiO3 heterostructure, where 2DEG is formed at LaAlO3/SrTiO3 interface. This device functions as a two-terminal, non-volatile memory of 1 diode-1 resistor with a large I+/I− ratio (>108 at ±6 V) and Ion/Ioff ratio (>107). This is attributed to not only Schottky barrier modulation at metal/ferroelectric interface by polarization reversal but also the field-effect metal-insulator transition of 2DEG. Moreover, using this heterostructure, we can demonstrate a memristive behavior for an artificial synapse memory, where the resistance can be continuously tuned by partial polarization switching, and the electrons are only unidirectionally transmitted. Beyond non-volatile memory and logic devices, our results will provide new opportunities to emerging electronic devices such as multifunctional nanoelectronics and neuromorphic electronics. PMID:26014446

  14. A Model for Ferroelectric Phase Shifters

    NASA Technical Reports Server (NTRS)

    Romanofsky, Robert R.; Qureshi, A. Haq

    2000-01-01

    Novel microwave phase shifters consisting of coupled microstrip lines on thin ferroelectric films have been demonstrated recently. A theoretical model useful for predicting the propagation characteristics (insertion phase shift, dielectric loss, impedance, and bandwidth) is presented here. The model is based on a variational solution for line capacitance and coupled strip transmission line theory.

  15. Quantum criticality in a uniaxial organic ferroelectric

    NASA Astrophysics Data System (ADS)

    Rowley, S. E.; Hadjimichael, M.; Ali, M. N.; Durmaz, Y. C.; Lashley, J. C.; Cava, R. J.; Scott, J. F.

    2015-10-01

    Tris-sarcosine calcium chloride (TSCC) is a highly uniaxial ferroelectric with a Curie temperature of approximately 130 K. By suppressing ferroelectricity with bromine substitution on the chlorine sites, pure single crystals were tuned through a ferroelectric quantum phase transition. The resulting quantum critical regime was investigated in detail and was found to persist up to temperatures of at least 30-40 K. The nature of long-range dipole interactions in uniaxial materials, which lead to non-analytical terms in the free-energy expansion in the polarization, predict a dielectric susceptibility varying as 1/T 3close to the quantum critical point. Rather than this, we find that the dielectric susceptibility varies as 1/T 2 as expected and observed in better known multi-axial systems. We explain this result by identifying the ultra-weak nature of the dipole moments in the TSCC family of crystals. Interestingly, we observe a shallow minimum in the inverse dielectric function at low temperatures close to the quantum critical point in paraelectric samples that may be attributed to the coupling of quantum polarization and strain fields. Finally, we present results of the heat capacity and electro-caloric effect and explain how the time dependence of the polarization in ferroelectrics and paraelectrics should be considered when making quantitative estimates of temperature changes induced by applied electric fields.

  16. Intrinsic ferroelectric switching from first principles

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

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

  17. Intrinsic ferroelectric switching from first principles.

    PubMed

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

    2016-06-16

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

  18. Using agent-based technology to create a cost effective, integrated, multimedia view of the electronic medical record.

    PubMed Central

    Lowe, H. J.; Walker, W. K.; Vries, J. K.

    1995-01-01

    Image Engine is multi-user, client-server database for the storage, retrieval and sharing of a wide range of digitized biomedical images under development at the University of Pittsburgh. This paper provides an overview of the system and describes the use of agent-based technology to integrate clinical information from the Image Engine database and the MARS clinical information system at the University of Pittsburgh Medical Center. Agent-mediated links provide a mechanism for combining clinical data from multiple databases to create a unified, multimedia view of the electronic medical record. Images Figure 1 PMID:8563320

  19. Interaction of Terahertz Radiation with Ferroelectrics

    NASA Astrophysics Data System (ADS)

    Nelson, Keith

    2007-03-01

    Ferroelectric crystals have long been used as acoustic transducers and receivers. An extensive toolset has been developed for MHz-frequency acoustic wave generation, control, guidance, and readout. In recent years, an analogous toolset has been developed for terahertz wave transduction and detection. Femtosecond optical pulses irradiate ferroelectric crystals to generate responses in the 0.1-5 THz frequency range that are admixtures of electromagnetic and polar lattice vibrational excitations called phonon-polaritons. Spatiotemporal femtosecond pulse shaping may be used to generate additional optical pulses that arrive at specified times and sample locations for control and manipulation of the THz waves. Femtosecond laser machining may be used for fabrication of waveguides, resonators, and other structures that are integrated into the ferroelectric host crystal. Finally, real-space imaging of the THz fields can be executed with variably delayed femtosecond probe pulses, permitting direct visualization of THz wave spatial and temporal evolution. This ``polaritonics'' toolset enables multiplexed generation of arbitrary THz waveforms and use of the waveforms within the ferroelectric host crystal or after projection into free space or an adjacent medium. The polaritonics platform will be reviewed and several new developments and applications will be presented. These include spectroscopy of relaxor ferroelectrics, whose temperature-dependent dielectric responses in the GHz-THz regime reveal complex polarization dynamics on well separated fast and slow time scales; direct measurement of phonon-polariton lattice vibrational displacements through femtosecond time-resolved x-ray diffraction; generation of high polariton field amplitudes and pulse energies; use of large-amplitude polariton waves to drive nonlinear lattice vibrational responses; and enhancement of optical-to-THz conversion efficiency through a pseudo-phase-matching approach that circumvents the very large

  20. A methodology for incorporating web technologies into a computer-based patient record, with contributions from cognitive science.

    PubMed

    Webster, Charles

    2002-12-18

    Cognitive science is a rich source of insight for creative use of new Web technologies by medical informatics workers. I outline a project to Web-enable an existing computer-based patient record (CPR) in the context of ideas from philosophy, linguistics, artificial intelligence, and cognitive psychology. Web prototypes play an important role (a) because Web technology lends itself to rapid prototype development, and (b) because prototypes help team members bridge among disparate medical, computing, and business ontologies. Six Web-enabled CPR prototypes were created and ranked. User scenarios were generated using a user communication matrix. Resulting prototypes were compared according to the degree to which they satisfied medical, computing, and business constraints. In a different organization, or at different time, candidate prototypes and their ranking might have been different. However, prototype generation and comparison are fundamentally influenced by factors usefully understood in a cognitive science framework. PMID:12467789

  1. Implementation of electronic medical records requires more than new software: Lessons on integrating and managing health technologies from Mbarara, Uganda.

    PubMed

    Madore, Amy; Rosenberg, Julie; Muyindike, Winnie R; Bangsberg, David R; Bwana, Mwebesa B; Martin, Jeffrey N; Kanyesigye, Michael; Weintraub, Rebecca

    2015-12-01

    Implementation lessons: • Technology alone does not necessarily lead to improvement in health service delivery, in contrast to the common assumption that advanced technology goes hand in hand with progress. • Implementation of electronic medical record (EMR) systems is a complex, resource-intensive process that, in addition to software, hardware, and human resource investments, requires careful planning, change management skills, adaptability, and continuous engagement of stakeholders. • Research requirements and goals must be balanced with service delivery needs when determining how much information is essential to collect and who should be interfacing with the EMR system. • EMR systems require ongoing monitoring and regular updates to ensure they are responsive to evolving clinical use cases and research questions. • High-quality data and analyses are essential for EMRs to deliver value to providers, researchers, and patients. PMID:26699355

  2. Secretly Recording the Police: The Confluence of Communication, Culture, and Technology in the Public Sphere

    ERIC Educational Resources Information Center

    Schaefer, Zachary A.

    2012-01-01

    Mobile communication technologies have changed the way that police do their job. Since the Rodney King beating outside of Los Angeles in 1991, literally thousands of police brutality videos have surfaced on the internet that document perceived acts of violence carried out against seemingly defenseless perpetrators. Police organizations throughout…

  3. Assessing Factors Affecting Physician's Intention to Adopt Biometric Authentication Technology in Electronic Medical Records

    ERIC Educational Resources Information Center

    Corazao, Cesar E.

    2014-01-01

    The Health Insurance Portability and Accountability Act of 1996 (HIPAA) regulated the privacy and security of patient information. Since HIPPA became a law, hospital operators have struggled to comply fully with its security and privacy provisions. The proximity-based biometric authentication (PBBA) technology evolved in last decade to help…

  4. Unintended Consequences: New Materialist Perspectives on Library Technologies and the Digital Record

    ERIC Educational Resources Information Center

    Manoff, Marlene

    2013-01-01

    Digital technology has irrevocably altered the nature of the archive. Drawing on materialist critiques and the evolving field of media archaeology, this essay explores new strategies for understanding the implications of computer networks in libraries. Although a significant portion of the contemporary literature within Library and Information…

  5. Correlationally Assessing the Relationship of Information Technology Investments in Electronic Medical Records to Business Value

    ERIC Educational Resources Information Center

    Richardson, Daniel J.

    2009-01-01

    The lag in information exchange and assimilation adoption experienced by modern primary care physicians in the conduct of evidence based medicine may be affecting health care system productivity and patient quality of care. Further, interest in whether or not information technology (IT) investments show an increase in business value has increased…

  6. Concurrent bandgap narrowing and polarization enhancement in epitaxial ferroelectric nanofilms

    NASA Astrophysics Data System (ADS)

    Tyunina, Marina; Yao, Lide; Chvostova, Dagmar; Dejneka, Alexandr; Kocourek, Tomas; Jelinek, Miroslav; Trepakov, Vladimir; van Dijken, Sebastiaan

    2015-04-01

    Perovskite-type ferroelectric (FE) crystals are wide bandgap materials with technologically valuable optical and photoelectric properties. Here, versatile engineering of electronic transitions is demonstrated in FE nanofilms of KTaO3, KNbO3 (KNO), and NaNbO3 (NNO) with a thickness of 10-30 unit cells. Control of the bandgap is achieved using heteroepitaxial growth of new structural phases on SrTiO3 (001) substrates. Compared to bulk crystals, anomalous bandgap narrowing is obtained in the FE state of KNO and NNO films. This effect opposes polarization-induced bandgap widening, which is typically found for FE materials. Transmission electron microscopy and spectroscopic ellipsometry measurements indicate that the formation of higher-symmetry structural phases of KNO and NNO produces the desirable red shift of the absorption spectrum towards visible light, while simultaneously stabilizing robust FE order. Tuning of optical properties in FE films is of interest for nanoscale photonic and optoelectronic devices.

  7. Recording and Reading Alchemy and Art-Technology in Medieval and Premodern German Recipe Collections.

    PubMed

    Neven, Sylvie

    2016-01-01

    In the Middle Ages and the premodern period knowledge of alchemical practices and materials was transmitted via collections of recipes often grouped concomitantly with art-technological instructions. In both alchemy and chemical technology particular importance is placed on artisanal and craft practices. Both are concerned with the description of colours. Both require procedures involving precise and specifically defined actions, prescriptions and ingredients. Assuming that alchemical and artistic texts have the same textual format, this raises the question: were they produced, diffused and read by the same people? This paper investigates the authorship and the context of production behind a sample of German alchemical manuscripts dating from the fourteenth to the sixteenth century. It scrutinizes their process of production, compilation and dissemination. This paper also sheds light on the various types of marginalia, and correlates them with their diverse functions. It thus delivers significant information about the readers and users of these manuscripts. PMID:27071299

  8. 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. PMID:26788984

  9. 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.

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

    PubMed

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

    2014-01-01

    Relaxor ferroelectrics exemplify a class of functional materials where interplay between disorder and phase instability results in inhomogeneous nanoregions. Although known for about 30 years, there is no definitive explanation for polar nanoregions (PNRs). Here we show that ferroelectric phonon localization drives PNRs in relaxor ferroelectric PMN-30%PT using neutron scattering. At the frequency of a preexisting resonance mode, nanoregions of standing ferroelectric phonons develop with a coherence length equal to one wavelength and the PNR size. Anderson localization of ferroelectric phonons by resonance modes explains our observations and, with nonlinear slowing, the PNRs and relaxor properties. Phonon localization at additional resonances near the zone edges explains competing antiferroelectric distortions known to occur at the zone edges. Our results indicate the size and shape of PNRs that are not dictated by complex structural details, as commonly assumed, but by phonon resonance wave vectors. This discovery could guide the design of next generation relaxor ferroelectrics. PMID:24718289

  11. Ferroelectric domain engineering by focused infrared femtosecond pulses

    SciTech Connect

    Chen, Xin; Shvedov, Vladlen; Sheng, Yan; Karpinski, Pawel; Koynov, Kaloian; Wang, Bingxia; Trull, Jose; Cojocaru, Crina; Krolikowski, Wieslaw

    2015-10-05

    We demonstrate infrared femtosecond laser-induced inversion of ferroelectric domains. This process can be realised solely by using tightly focused laser pulses without application of any electric field prior to, in conjunction with, or subsequent to the laser irradiation. As most ferroelectric crystals like LiNbO{sub 3}, LiTaO{sub 3}, and KTiOPO{sub 4} are transparent in the infrared, this optical poling method allows one to form ferroelectric domain patterns much deeper inside a ferroelectric crystal than by using ultraviolet light and hence can be used to fabricate practical devices. We also propose in situ diagnostics of the ferroelectric domain inversion process by monitoring the Čerenkov second harmonic signal, which is sensitive to the appearance of ferroelectric domain walls.

  12. Ferroelectric domain wall motion induced by polarized light.

    PubMed

    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

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

    PubMed

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

    2016-03-21

    Ferroelectric materials are important components of sensors, actuators and non-volatile memories. However, possible device configurations are limited due to the need to provide screening charges to ferroelectric interfaces to avoid depolarization. Here we show that, by alternating ferroelectric and semiconducting nanowires over an insulating substrate, the ferroelectric dipole moment can be stabilized by injected free charge carriers accumulating laterally in the neighboring semiconducting nanowires. This lateral electrostatic coupling between ferroelectric and semiconducting nanowires offers new opportunities to design new device architectures. As an example, we demonstrate the fabrication of an elementary non-volatile memory device in a transistor-like configuration, of which the source-drain current exhibits a typical hysteretic behavior with respect to the poling voltage. The potential for size reduction intrinsic to the nanostructured hybrid layer offers opportunities for the development of strongly miniaturized ferroelectric and piezoelectric devices. PMID:26927694

  14. Ferroelectricity and Phase Transitions in Monolayer Group-IV Monochalcogenides.

    PubMed

    Fei, Ruixiang; Kang, Wei; Yang, Li

    2016-08-26

    Ferroelectricity usually fades away as materials are thinned down below a critical value. We reveal that the unique ionic-potential anharmonicity can induce spontaneous in-plane electrical polarization and ferroelectricity in monolayer group-IV monochalcogenides MX (M=Ge, Sn; X=S, Se). An effective Hamiltonian has been successfully extracted from the parametrized energy space, making it possible to study the ferroelectric phase transitions in a single-atom layer. The ferroelectricity in these materials is found to be robust and the corresponding Curie temperatures are higher than room temperature, making them promising for realizing ultrathin ferroelectric devices of broad interest. We further provide the phase diagram and predict other potentially two-dimensional ferroelectric materials. PMID:27610884

  15. 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

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

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

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

  17. Giant Resistive Switching via Control of Ferroelectric Charged Domain Walls.

    PubMed

    Li, Linze; Britson, Jason; Jokisaari, Jacob R; Zhang, Yi; Adamo, Carolina; Melville, Alexander; Schlom, Darrell G; Chen, Long-Qing; Pan, Xiaoqing

    2016-08-01

    Controlled switching of resistivity in ferroelectric thin films is demonstrated by writing and erasing stable, nanoscale, strongly charged domain walls using an in situ transmission electron microscopy technique. The resistance can be read nondestructively and presents the largest off/on ratio (≈10(5) ) ever reported in room-temperature ferroelectric devices, opening new avenues for engineering ferroelectric thin-film devices. PMID:27213756

  18. The development and design of an electronic patient record using open source web-based technology.

    PubMed

    Syed-Mohamad, Sharifa Mastura; Ali, Siti Hawa; Mat-Husin, Mohd Nazri

    2010-01-01

    This paper describes the method used to develop the One Stop Crisis Centre (OSCC) Portal, an open source web-based electronic patient record system (EPR) for the One Stop Crisis Center, Hospital Universiti Sains Malaysia (HUSM) in Kelantan, Malaysia. Features and functionalities of the system are presented to demonstrate the workflow. Use of the OSCC Portal improved data integration and data communication and contributed to improvements in care management. With implementation of the OSCC portal, improved coordination between disciplines and standardisation of data in HUSM were noticed. It is expected that this will in turn result in improved data confidentiality and data integrity. The collected data will also be useful for quality assessment and research. Other low-resource centers with limited computer hardware and access to open-source software could benefit from this endeavour. PMID:20335647

  19. Ferroelectric switching behavior in morphology controlled ferroelectric-semiconductor polymer blends for organic memory

    NASA Astrophysics Data System (ADS)

    Lim, Eunhee; Su, Gregory; Kramer, Edward; Chabinyc, Michael

    2015-03-01

    Memory is a fundamental component of all modern electronic systems. Organic ferroelectric memories are advantageous because they are thin and lightweight devices that can be made printable, foldable, and stretchable. Organic ferroelectric memories comprise a physical blend of an organic semiconducting polymer and an insulating ferroelectric polymer as the active layer in a thin film diode. Controlling the thin film morphology in these blends is important for electrical properties of the resulting device. We have found that when a semiconducting thiophene polymer with polar alkanoate side chains (P3EPT) is blended with well-studied ferroelectric polymer poly [(vinylidenefluoride-co-trifluoroethylene] P (VDF-TrFE), the resulting film has low surface roughness and more controllable domain sizes compared to the widely used poly (3-hexylthiophene). This difference allows more reliable study of the ferroelectric switching behavior in devices with domain size of about 100nm. The influence of the 3D composition measured by a combination of methods, including soft x-ray microscopy, on the electrical characteristics will be presented.

  20. Patients welcome the Sickle Cell Disease Mobile Application to Record Symptoms via Technology (SMART).

    PubMed

    Shah, Nirmish; Jonassaint, Jude; De Castro, Laura

    2014-01-01

    The widespread use of mobile phones among patients provides a unique opportunity for the development of mobile health intervention designed specifically for sickle cell disease, which will improve self-management as well as health care delivery. Our objective was to determine the receptiveness of patients with sickle cell disease to technology and a mobile application (app) designed for sickle cell disease. Phase I included 100 patients who completed a survey inquiring about receptiveness to technology and use of mobile devices to self-manage and communicate with providers. Phase II surveyed 17 additional patients who tested a newly developed sickle cell disease app, to report its usability and utility. In Phase I, on a 0-10 Likert scale where 0 is not comfortable, and 10 is extremely comfortable, 87.0% of participants reported >5 comfort level using a mobile device for health care management. Participants were comfortable with texting (81.0%) and emailing (77.0%) but not with social media (40.0%). Most participants (84.0%) owned computer devices (desktops, laptops, tablets, or iPads), and 92.0% owned mobile devices. In Phase II, participants reported that the app tested was useful to track pain (88.0%), and 94.0% reported that it was easy to use, practical, and useful for health self-management. All reported that the app was useful to help one communicate with providers. Following the use of our app, patients found it an extremely valuable tool for tracking pain, health management, and communicating with providers. We conclude that mobile technology might provide an appropriate venue for sickle cell disease healthcare management. PMID:24512633

  1. FAST TRACK COMMUNICATION: Interlayer exchange coupling across a ferroelectric barrier

    NASA Astrophysics Data System (ADS)

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

    2010-09-01

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

  2. 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.

  3. Ferroelectric nanostructure having switchable multi-stable vortex states

    DOEpatents

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

    2009-09-22

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

  4. Dual Nature of Improper Ferroelectricity in a Magnetoelectric Multiferroic

    SciTech Connect

    Picozzi, S.; Yamauchi, K.; Sanyal, B.; Sergienko, Ivan A; Dagotto, Elbio R

    2007-01-01

    Using first-principles calculations, we study the microscopic origin of ferroelectricity (FE) induced by magnetic order in the orthorhombic HoMnO3. We obtain the largest ferroelectric polarization observed in the whole class of improper magnetic ferroelectrics to date. We find that the two proposed mechanisms for FE in multiferroics, lattice and electronic based, are simultaneously active in this compound: a large portion of the ferroelectric polarization arises due to quantum-mechanical effects of electron orbital polarization, in addition to the conventional polar atomic displacements. An interesting mechanism for switching the magnetoelectric domains by an electric field via a 180 coherent rotation of Mn spins is also proposed.

  5. Domain switching of fatigued ferroelectric thin films

    SciTech Connect

    Tak Lim, Yun; Yeog Son, Jong E-mail: hoponpop@ulsan.ac.kr; Shin, Young-Han E-mail: hoponpop@ulsan.ac.kr

    2014-05-12

    We investigate the domain wall speed of a ferroelectric PbZr{sub 0.48}Ti{sub 0.52}O{sub 3} (PZT) thin film using an atomic force microscope incorporated with a mercury-probe system to control the degree of electrical fatigue. The depolarization field in the PZT thin film decreases with increasing the degree of electrical fatigue. We find that the wide-range activation field previously reported in ferroelectric domains result from the change of the depolarization field caused by the electrical fatigue. Domain wall speed exhibits universal behavior to the effective electric field (defined by an applied electric field minus the depolarization field), regardless of the degree of the electrical fatigue.

  6. Vertical Transport in Ferroelectric/Superconductor Heterostructures

    NASA Astrophysics Data System (ADS)

    Begon-Lours, Laura; Trastoy, Juan; Bernard, Rozenn; Jacquet, Eric; Carretero, Cecile; Bouzehouane, Karim; Fusil, Stephane; Garcia, Vincent; Xavier, Stephane; Girod, Stephanie; Deranlot, Cyrile; Bibes, Manuel; Barthelemy, Agnes; Villegas, Javier E.

    2015-03-01

    We study electric field-effects in superconducting films by measuring vertical transport in ferroelectric/superconductor heterostructures. These are based on ultrathin (4 to 8 nm thick) BiFeO3-Mn grown on YBa2Cu3O7 by pulsed laser deposition. Nanoscale contacts are defined on the BiFeO3 via a series of nanofabrication steps which include e-beam lithography, metal deposition (Nb or Co capped with Pt) and lift-off. Conductive-tip atomic force microscopy and piezoresponse force microscopy are used to characterize the transport across the ferroelectric barrier as a function of its polarization (up/down). The observed electro-resistance, measured at various temperatures, allows studying the different electric-field screening in the normal and superconducting states. Work supported by DIM Oxymore.

  7. Magnetocaloric effect in ferroelectric Ising chain magnet

    NASA Astrophysics Data System (ADS)

    Qi, Yan; Liu, Jia; Yu, Nai-sen; Du, An

    2016-05-01

    We investigate the magnetocaloric effect (MCE) in multiferroic chain system by adopting the elastic Ising-chain model. Based on the transfer-matrix method, the magnetothermal quantities of characterizing MCE behaviors including the entropy, entropy change and adiabatic cooling rate are rigorously determined. Combined with analysis of ground-state, we mainly discuss results in an antiferromagnetic regime associated with ferroelectric transition. Our results show that the entropy change is greatly enhanced near the saturation field as frustration parameter varies in this regime, and accompanied with remarkable inverse MCE, indicating the enormous potential of multiferroic system in low-temperature refrigeration. Meanwhile we also observe a prominent temperature variation in the isoentropy curves close to zero-temperature ferroelectric transition, but this enhancing MCE signal is very sensitive to the thermal fluctuations, and can be strongly suppressed even under a small temperature.

  8. 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.

  9. Block copolymer/ferroelectric nanoparticle nanocomposites

    NASA Astrophysics Data System (ADS)

    Pang, Xinchang; He, Yanjie; Jiang, Beibei; Iocozzia, James; Zhao, Lei; Guo, Hanzheng; Liu, Jin; Akinc, Mufit; Bowler, Nicola; Tan, Xiaoli; Lin, Zhiqun

    2013-08-01

    Nanocomposites composed of diblock copolymer/ferroelectric nanoparticles were formed by selectively constraining ferroelectric nanoparticles (NPs) within diblock copolymer nanodomains via judicious surface modification of ferroelectric NPs. Ferroelectric barium titanate (BaTiO3) NPs with different sizes that are permanently capped with polystyrene chains (i.e., PS-functionalized BaTiO3NPs) were first synthesized by exploiting amphiphilic unimolecular star-like poly(acrylic acid)-block-polystyrene (PAA-b-PS) diblock copolymers as nanoreactors. Subsequently, PS-functionalized BaTiO3 NPs were preferentially sequestered within PS nanocylinders in the linear cylinder-forming polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) diblock copolymer upon mixing the BaTiO3 NPs with PS-b-PMMA. The use of PS-b-PMMA diblock copolymers, rather than traditional homopolymers, offers the opportunity for controlling the spatial organization of PS-functionalized BaTiO3 NPs in the PS-b-PMMA/BaTiO3 NP nanocomposites. Selective solvent vapor annealing was utilized to control the nanodomain orientation in the nanocomposites. Vertically oriented PS nanocylinders containing PS-functionalized BaTiO3 NPs were yielded after exposing the PS-b-PMMA/BaTiO3 NP nanocomposite thin film to acetone vapor, which is a selective solvent for PMMA block. The dielectric properties of nanocomposites in the microwave frequency range were investigated. The molecular weight of PS-b-PMMA and the size of BaTiO3 NPs were found to exert an apparent influence on the dielectric properties of the resulting nanocomposites.Nanocomposites composed of diblock copolymer/ferroelectric nanoparticles were formed by selectively constraining ferroelectric nanoparticles (NPs) within diblock copolymer nanodomains via judicious surface modification of ferroelectric NPs. Ferroelectric barium titanate (BaTiO3) NPs with different sizes that are permanently capped with polystyrene chains (i.e., PS-functionalized BaTiO3NPs) were

  10. Porous ferroelectrics for energy harvesting applications

    NASA Astrophysics Data System (ADS)

    Roscow, J.; Zhang, Y.; Taylor, J.; Bowen, C. R.

    2015-11-01

    This paper provides an overview of energy harvesting using ferroelectric materials, with a particular focus on the energy harvesting capabilities of porous ferroelectric ceramics for both piezo- and pyroelectric harvesting. The benefits of introducing porosity into ferro- electrics such as lead zirconate titanate (PZT) has been known for over 30 years, but the potential advantages for energy harvesting from both ambient vibrations and temperature fluctuations have not been studied in depth. The article briefly discusses piezoelectric and pyro- electric energy harvesting, before evaluating the potential benefits of porous materials for increasing energy harvesting figures of merits and electromechanical/electrothermal coupling factors. Established processing routes are evaluated in terms of the final porous structure and the resulting effects on the electrical, thermal and mechanical properties.

  11. 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

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

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

    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.

  13. A Role for Semantic Web Technologies in Patient Record Data Collection

    NASA Astrophysics Data System (ADS)

    Ogbuji, Chimezie

    Business Process Management Systems (BPMS) are a component of the stack of Web standards that comprise Service Oriented Architecture (SOA). Such systems are representative of the architectural framework of modern information systems built in an enterprise intranet and are in contrast to systems built for deployment on the larger World Wide Web. The REST architectural style is an emerging style for building loosely coupled systems based purely on the native HTTP protocol. It is a coordinated set of architectural constraints with a goal to minimize latency, maximize the independence and scalability of distributed components, and facilitate the use of intermediary processors.Within the development community for distributed, Web-based systems, there has been a debate regarding themerits of both approaches. In some cases, there are legitimate concerns about the differences in both architectural styles. In other cases, the contention seems to be based on concerns that are marginal at best. In this chapter, we will attempt to contribute to this debate by focusing on a specific, deployed use case that emphasizes the role of the Semantic Web, a simple Web application architecture that leverages the use of declarative XML processing, and the needs of a workflow system. The use case involves orchestrating a work process associated with the data entry of structured patient record content into a research registry at the Cleveland Clinic's Clinical Investigation department in the Heart and Vascular Institute.

  14. Electrically induced mechanical precompression of ferroelectric plates

    DOEpatents

    Chen, P.J.

    1987-03-02

    A method of electrically inducing mechanical precompression of ferroelectric plate covered with electrodes utilizes the change in strains of the plate as functions of applied electric field. A first field polarizes and laterally shrinks the entire plate. An outer portion of the electrodes are removed, and an opposite field partially depolarizes and expands the central portion of the plate against the shrunk outer portion. 2 figs.

  15. Ferroelectricity in (K@C60)n

    NASA Astrophysics Data System (ADS)

    Clougherty, Dennis P.

    2000-09-01

    A theoretical analysis of the ground state of long-chain (K@C60)n is presented. Within mean field theory, a ferroelectric ground state is found to be stable because of the pseudo-Jahn-Teller mixing of the b1u and the b2g band with a zone-center optical phonon involving the displacement of the endohedral K- ions. A phase diagram for this model is derived in the narrow bandwidth regime.

  16. Electrically induced mechanical precompression of ferroelectric plates

    DOEpatents

    Chen, Peter J.

    1987-01-01

    A method of electrically inducing mechanical precompression of a ferroelectric plate covered with electrodes utilizes the change in strains of the plate as functions of applied electric field. A first field polarizes and laterally shrinks the entire plate. An outer portion of the electrodes are removed, and an opposite field partially depolarizes and expands the central portion of the plate against the shrunk outer portion.

  17. TaN interface properties and electric field cycling effects on ferroelectric Si-doped HfO{sub 2} thin films

    SciTech Connect

    Lomenzo, Patrick D.; Nishida, Toshikazu; Takmeel, Qanit; Zhou, Chuanzhen; Fancher, Chris M.; Jones, Jacob L.; Lambers, Eric; Rudawski, Nicholas G.; Moghaddam, Saeed

    2015-04-07

    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-O 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.

  18. Wear-time recording during early Class III facemask treatment using TheraMon chip technology.

    PubMed

    Stocker, Bruce; Willmann, Jan H; Wilmes, Benedict; Vasudavan, Sivabalan; Drescher, Dieter

    2016-09-01

    Successful intervention in a developing Class III malocclusion with facemask protraction therapy depends on a patient's ability to adhere to the recommendations for duration of appliance wear. In this article, we report the introduction of a novel approach for tracking of the duration of application of a protraction facemask, with the incorporation of a "FaceMon" sensor (TheraMon, microelectronic system; MC Technology GmbH, Hargelsberg, Austria) to track wear time. A 9-year-old boy with a Class III malocclusion was successfully treated with a modified alternate rapid maxillary expansion and constriction protocol and intermittent application of a hybrid hyrax-protraction facemask combination. The average duration of wear of the facemask was measured at 10.8 hours per day. The use of an objective measuring device may have implications for the development of treatment strategies, since patient responses may be able to calibrated in relation to compliance. PMID:27585783

  19. Prediction of a native ferroelectric metal

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

  20. Ferroelectricity in underdoped La-based cuprates.

    PubMed

    Viskadourakis, Z; Sunku, S S; Mukherjee, S; Andersen, B M; Ito, T; Sasagawa, T; Panagopoulos, C

    2015-01-01

    Doping a "parent" antiferromagnetic Mott insulator in cuprates leads to short-range electronic correlations and eventually to high-Tc superconductivity. However, the nature of charge correlations in the lightly doped cuprates remains unclear. Understanding the intermediate electronic phase in the phase diagram (between the parent insulator and the high-Tc superconductor) is expected to elucidate the complexity both inside and outside the superconducting dome, and in particular in the underdoped region. One such phase is ferroelectricity whose origin and relation to the properties of high-Tc superconductors is subject of current research. Here we demonstrate that ferroelectricity and the associated magnetoelectric coupling are in fact common in La-214 cuprates namely, La2-xSrxCuO4, La2LixCu1-xO4 and La2CuO4+x. It is proposed that ferroelectricity may result from local CuO6 octahedral distortions, associated with the dopant atoms and clustering of the doped charge carriers, which break spatial inversion symmetry at the local scale whereas magnetoelectric coupling can be tuned through Dzyaloshinskii-Moriya interaction. PMID:26486276

  1. Ferroelectricity in underdoped La-based cuprates

    PubMed Central

    Viskadourakis, Z.; Sunku, S. S.; Mukherjee, S.; Andersen, B. M.; Ito, T.; Sasagawa, T.; Panagopoulos, C.

    2015-01-01

    Doping a “parent” antiferromagnetic Mott insulator in cuprates leads to short-range electronic correlations and eventually to high-Tc superconductivity. However, the nature of charge correlations in the lightly doped cuprates remains unclear. Understanding the intermediate electronic phase in the phase diagram (between the parent insulator and the high-Tc superconductor) is expected to elucidate the complexity both inside and outside the superconducting dome, and in particular in the underdoped region. One such phase is ferroelectricity whose origin and relation to the properties of high-Tc superconductors is subject of current research. Here we demonstrate that ferroelectricity and the associated magnetoelectric coupling are in fact common in La-214 cuprates namely, La2-xSrxCuO4, La2LixCu1-xO4 and La2CuO4+x. It is proposed that ferroelectricity may result from local CuO6 octahedral distortions, associated with the dopant atoms and clustering of the doped charge carriers, which break spatial inversion symmetry at the local scale whereas magnetoelectric coupling can be tuned through Dzyaloshinskii-Moriya interaction. PMID:26486276

  2. WFL: Microwave Applications of Thin Ferroelectric Films

    NASA Technical Reports Server (NTRS)

    Romanofsky, Robert

    2013-01-01

    We have developed a family of tunable microwave circuits, operating from X- through Ka-band, based on laser ablated BaxSr1-xTiO films on lanthanum aluminate and magnesium oxide substrates. Circuits include voltage controlled oscillators, filters, phase shifters and antennas. A review of the basic theory of operation of these devices will be presented along with measured performance. Emphasis has been on low-loss phase shifters to enable a new phased array architecture. The critical role of phase shifter loss and transient response in reflectarray antennas will be discussed. The Ferroelectric Reflectarray Critical Components Space Experiment was launched on the penultimate Space Shuttle, STS-134, in May of 2011. It included a bank of ferroelectric phase shifters with two different stoichiometries as well as ancillary electronics. The experiment package and status will be reported. In addition, unusual results of a Van der Pauw measurement involving a ferroelectric film grown on buffered high resisitivity silicon will be discussed.

  3. Ferroelectric-carbon nanotube memory devices.

    PubMed

    Kumar, Ashok; Shivareddy, Sai G; Correa, Margarita; Resto, Oscar; Choi, Youngjin; Cole, Matthew T; Katiyar, Ram S; Scott, James F; Amaratunga, Gehan A J; Lu, Haidong; Gruverman, Alexei

    2012-04-27

    One-dimensional ferroelectric nanostructures, carbon nanotubes (CNT) and CNT-inorganic oxides have recently been studied due to their potential applications for microelectronics. Here, we report coating of a registered array of aligned multi-wall carbon nanotubes (MWCNT) grown on silicon substrates by functional ferroelectric Pb(Zr,Ti)O3 (PZT) which produces structures suitable for commercial prototype memories. Microstructural analysis reveals the crystalline nature of PZT with small nanocrystals aligned in different directions. First-order Raman modes of MWCNT and PZT/MWCNT/n-Si show the high structural quality of CNT before and after PZT deposition at elevated temperature. PZT exists mostly in the monoclinic Cc/Cm phase, which is the origin of the high piezoelectric response in the system. Low-loss square piezoelectric hysteresis obtained for the 3D bottom-up structure confirms the switchability of the device. Current-voltage mapping of the device by conducting atomic force microscopy (c-AFM) indicates very low transient current. Fabrication and functional properties of these hybrid ferroelectric-carbon nanotubes is the first step towards miniaturization for future nanotechnology sensors, actuators, transducers and memory devices. PMID:22460805

  4. A Cryogenic GaAs PHEMT/ Ferroelectric Ku-Band Tunable Oscillator

    NASA Technical Reports Server (NTRS)

    Romanofsky, Robert R.; Miranda, Felix A.; VanKeuls, Fred W.

    1998-01-01

    A Ku-band tunable oscillator operated at and below 77 K is described. The oscillator is based on two separate technologies: a 0.25 mm GaAs pseudomorphic high electron mobility transistor (PHEMT) circuit optimized for cryogenic operation, and a gold microstrip ring resonator patterned on a thin ferroelectric (SrTiO3) film which was laser ablated onto a LaAlO3 substrate. A tuning range of up to 3% of the center frequency was achieved by applying dc bias between the ring resonator and ground plane. To the best of our knowledge, this is the first tunable oscillator based on a thin film ferroelectric structure demonstrated in the microwave frequency range. The design methodology of the oscillator and the performance characteristics of the tunable resonator are described.

  5. Ferromagnetism induced by entangled charge and orbital orderings in ferroelectric titanate perovskites.

    PubMed

    Bristowe, N C; Varignon, J; Fontaine, D; Bousquet, E; Ghosez, Ph

    2015-01-01

    In magnetic materials, the Pauli exclusion principle typically drives anti-alignment between electron spins on neighbouring species resulting in antiferromagnetic behaviour. Ferromagnetism exhibiting spontaneous spin alignment is a fairly rare behaviour, but once materialized is often associated with itinerant electrons in metals. Here we predict and rationalize robust ferromagnetism in an insulating oxide perovskite structure based on the popular titanate series. In half-doped layered titanates, the combination of Jahn-Teller and oxygen breathing motions opens a band gap and creates an unusual charge and orbital ordering of the Ti d electrons. It is argued that this intriguingly intricate electronic network favours the elusive inter-site ferromagnetic (FM) ordering, on the basis of intra-site Hund's rules. Finally, we find that the layered oxides are also ferroelectric with a spontaneous polarization approaching that of BaTiO3. The concepts are general and design principles of the technologically desirable FM ferroelectric multiferroics are presented. PMID:25807180

  6. Studies of ferroelectric heterostructure thin films, interfaces, and device-related processes via in situ analytical techniques.

    SciTech Connect

    Aggarwal, S.; Auciello, O.; Dhote, A. M.; Gao, Y.; Gruen, D. M.; Im, J.; Irene, E. A.; Krauss, A. R.; Muller, A. H.; Ramesh, R.

    1999-06-29

    The science and technology of ferroelectric thin films has experienced an explosive development during the last ten years. Low-density non-volatile ferroelectric random access memories (NVFRAMS) are now incorporated in commercial products such as ''smart cards'', while high permittivity capacitors are incorporated in cellular phones. However, substantial work is still needed to develop materials integration strategies for high-density memories. We have demonstrated that the implementation of complementary in situ characterization techniques is critical to understand film growth and device processes relevant to device development. We are using uniquely integrated time of flight ion scattering and recoil spectroscopy (TOF-ISARS) and spectroscopic ellipsometry (SE) techniques to perform in situ, real-time studies of film growth processes in the high background gas pressure required to growth ferroelectric thin films. TOF-ISARS provides information on surface processes, while SE permits the investigation of buried interfaces as they are being formed. Recent studies on SrBi{sub 2}Ta{sub 2}O{sub 9} (SBT) and Ba{sub x}Sr{sub 1{minus}x}TiO{sub 3} (BST) film growth and interface processes are discussed. Direct imaging of ferroelectric domains under applied electric fields can provide valuable information to understand domain dynamics in ferroelectric films. We discuss results of piezoresponse scanning force microscopy (SFM) imaging for nanoscale studies of polarization reversal and retention loss in Pb(Zr{sub x}Ti{sub 1{minus}x})O{sub 3} (PZT)-based capacitors. Another powerful technique suitable for in situ, real-time characterization of film growth processes and ferroelectric film-based device operation is based on synchrotrons X-ray scattering, which is currently being implemented at Argonne National Laboratory.

  7. Ab initio study of shear strain effects on ferroelectricity at PbTiO3 thin films

    NASA Astrophysics Data System (ADS)

    Van Truong, Do; Hung, Nguyen Tuan; Shimada, Takahiro; Kitamura, Takayuki

    2012-08-01

    Ferroelectric thin film with the perovskite ABO3 structure have been widely used in technology applications, e.g., actuators in MEMS/NEMS and nonvolatile random access memories (FeRAM). In order to clarify the effect of the shear strain on the ferroelectricity, the PbTiO3 thin film as a typical one is chosen. The focus of this study is to put on the PbO-terminated (1​ × ​1) and c(2​ × ​2) surfaces and the TiO2-terminated (1​ × ​1) surface. Based on ab initio density functional theory calculations with the local density approximation, we have found out that in both the PbO and TiO2-terminated (1​ × ​1) models, the ferroelectricity in the PbO layers was enhanced under the positive shear strain while it was suppressed under the negative one. For the TiO2 layers, the ferroelectricity was slightly enhanced and sharply suppressed under the positive and negative shear strains, respectively. In the PbO-terminated (2​ × ​2) model, the AFE phase was suppressed by the FE phase under the positive shear strain while the opposite trend was found under the negative shear strain. For the PbO layers, the ferroelectricity was enhanced under the positive and negative shear strains. For the TiO2 layers, the influence of the negative shear strain on the ferroelectricity was larger than that of the positive one. In addition, the ideal strength of the PbTiO3 thin film with the different terminations was investigated as well.

  8. Polarization and polarization fatigue in ferroelectrics

    NASA Astrophysics Data System (ADS)

    Du, Xiaofeng

    This thesis addresses some fundamental issues in ferroelectricity and its applications through a computational and experimental effort. It focuses on a variety of perovskite-type ferroelectric oxides and investigates the physical basis for spontaneous polarization, domain wall dynamics, and texture development in thin film applications. The dipole-dipole interactions between ionic species in perovskite-type materials have been calculated to determine the local field and the lattice instability. Different ferroelectric and anti-ferroelectric polarization transitions can be realized by taking into account the structure distortion of the parent perovskites. We find the local field is enhanced by short range disorder and its nature varies from disorder to disorder, causing polarization transitions in non-(100) directions. The molecular field theory has also been extended to layered perovskites, which favors in-plane polarization over c-polarization. These theoretical predictions are in agreement with the experimental observations of various perovskites and layered perovskites in both single crystal and thin film forms. Domain switching in PZT has been studied by probing the frequency dependency of polarization hysteresis. A picture of thermally activated domain wall movement is established from the frequency spectra of coercive field. The field dependence of domain wall bulging and the nature of the binding between pinning obstacles and the walls are inferred from such a study. Consistent with this picture, polarization fatigue can be defined as a process of increasing the resistance from pinning defects to domain wall motion. The chemical species that act as pinning defects have been identified through model experiments that control carrier injection, electrode interfaces, and film compositions. Based on these observations, a methodology is proposed to evaluate and predict the fatigue damage of both PZT and layered perovskite thin films. Processing of layered

  9. 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.

  10. Microscopic theory of superconductor-ferroelectric heterostructures: Interface charge redistribution

    NASA Astrophysics Data System (ADS)

    Pavlenko, N.; Schwabl, F.

    2003-03-01

    We present a theory of periodic ferroelectric-superconductor (FE-S) heterostructures containing ferroelectric layers sandwiched between superconducting planes. We analyze the electronic charge-carrier redistribution at the FE-S interface in the presence of the spontaneous polarization in the ferroelectric layer. On the other hand, we study the influence of the superconductor on the structural dynamics in the ferroelectric layer. The effect of FE-S contacts on the ferroelectrics is found to be crucial leading to a structural transformation from the state with the homogeneous-type polarization to the phase with a set of asymmetric stable polarization domains. FE-S interface phenomena induce a decrease of the temperature of the transition to the symmetric phase with two symmetric (negative and positive) polarization domains. Nevertheless, even above the ferroelectric critical temperature, we find in the ferroelectric layer a stable contact-induced enhanced spontaneous polarization. The domain structure in the symmetric phase appears as the response to the charge-carrier redistribution at the contact with the superconducting subsystem. An increase of the FE-S interface coupling results in a complex nonmonotonic behavior of the superconducting transition temperature and finally, for the strong-coupling regime, in a complete suppression of the superconductivity. The results are expected to be especially important for the analysis of high-temperature cuprate superconductor films grown on perovskite-type ferroelectrics.

  11. 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.

  12. 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.

  13. Novel Ferroelectric Liquid Crystals with Very Large Spontaneous Polarization

    NASA Astrophysics Data System (ADS)

    Nakauchi, Jun; Uematsu, Mioko; Sakashita, Keiichi; Kageyama, Yoshitaka; Hayashi, Seiji; Ikemoto, Tetsuya; Mori, Kenji

    1989-07-01

    Several ferroelectric liquid crystals derived from a new optically active (2S, 5R)-2-hydroxy-5-hexyl-δ-valerolactone have been synthesized, and their mesomorphic and ferroelectric properties have been investigated. Very large spontaneous polarization (Ps) has been observed in these compounds, one of which shows an extremly large Ps value: as high as 320 nC/cm2.

  14. Integration of lead zirconium titanate thin films for high density ferroelectric random access memory

    NASA Astrophysics Data System (ADS)

    Kim, Kinam; Lee, Sungyung

    2006-09-01

    Interests are being focused on types of nonvolatile memories such as ferroelectric random access memory (FRAM), phase change random access memory, or magnetoresistance random access memory due to their distinct memory properties such as excellent write performance which conventional nonvolatile memories do not possess. Among these types of nonvolatile memories, FRAM whose cell structure and operation are almost identical to dynamic random access memory (DRAM) can ideally realize cell size and speed of DRAM. Thus FRAM is the most appropriate candidate for future universal memory where all memory functions are performed with a single chip solution. Due to the poor ferroelectric properties of downscaled ultrathin lead zirconium titanate (PZT) capacitors as well as technical issues such as hydrogen and plasma related degradation arising from embedding ferroelectric metal-insulator-metal capacitors into conventional complementary metal oxide semiconductor processes, current FRAM still falls far below its ideally attainable cell size and performance. In this paper, based upon PZT capacitor, current mass-productive one pass transistor and one storage capacitor (1T1C), capacitor over bit line (COB) cell technologies are introduced upon which cell size of 0.937μm2 at 250nm minimum feature size technology node has been realized. And then, most recent 1T1C, COB cell technologies are discussed from which cell size of 0.27μm2 at 150nm minimum feature size technology node has been realized, and finally future three dimensional capacitor technologies for the FRAM with cell size of less than 0.08μm2 beyond 100nm minimum feature size technology node are suggested.

  15. Ferroelectric opening switches for large-scale pulsed power drivers.

    SciTech Connect

    Brennecka, Geoffrey L.; Rudys, Joseph Matthew; Reed, Kim Warren; Pena, Gary Edward; Tuttle, Bruce Andrew; Glover, Steven Frank

    2009-11-01

    Fast electrical energy storage or Voltage-Driven Technology (VDT) has dominated fast, high-voltage pulsed power systems for the past six decades. Fast magnetic energy storage or Current-Driven Technology (CDT) is characterized by 10,000 X higher energy density than VDT and has a great number of other substantial advantages, but it has all but been neglected for all of these decades. The uniform explanation for neglect of CDT technology is invariably that the industry has never been able to make an effective opening switch, which is essential for the use of CDT. Most approaches to opening switches have involved plasma of one sort or another. On a large scale, gaseous plasmas have been used as a conductor to bridge the switch electrodes that provides an opening function when the current wave front propagates through to the output end of the plasma and fully magnetizes the plasma - this is called a Plasma Opening Switch (POS). Opening can be triggered in a POS using a magnetic field to push the plasma out of the A-K gap - this is called a Magnetically Controlled Plasma Opening Switch (MCPOS). On a small scale, depletion of electron plasmas in semiconductor devices is used to affect opening switch behavior, but these devices are relatively low voltage and low current compared to the hundreds of kilo-volts and tens of kilo-amperes of interest to pulsed power. This work is an investigation into an entirely new approach to opening switch technology that utilizes new materials in new ways. The new materials are Ferroelectrics and using them as an opening switch is a stark contrast to their traditional applications in optics and transducer applications. Emphasis is on use of high performance ferroelectrics with the objective of developing an opening switch that would be suitable for large scale pulsed power applications. Over the course of exploring this new ground, we have discovered new behaviors and properties of these materials that were here to fore unknown. Some of

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

    PubMed

    Liu, Man; Wang, Jie

    2015-01-01

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

  17. Toward Ferroelectric Control of Monolayer MoS2.

    PubMed

    Nguyen, Ariana; Sharma, Pankaj; Scott, Thomas; Preciado, Edwin; Klee, Velveth; Sun, Dezheng; Lu, I-Hsi Daniel; Barroso, David; Kim, SukHyun; Shur, Vladimir Ya; Akhmatkhanov, Andrey R; Gruverman, Alexei; Bartels, Ludwig; Dowben, Peter A

    2015-05-13

    The chemical vapor deposition (CVD) of molybdenum disulfide (MoS2) single-layer films onto periodically poled lithium niobate is possible while maintaining the substrate polarization pattern. The MoS2 growth exhibits a preference for the ferroelectric domains polarized "up" with respect to the surface so that the MoS2 film may be templated by the substrate ferroelectric polarization pattern without the need for further lithography. MoS2 monolayers preserve the surface polarization of the "up" domains, while slightly quenching the surface polarization on the "down" domains as revealed by piezoresponse force microscopy. Electrical transport measurements suggest changes in the dominant carrier for CVD MoS2 under application of an external voltage, depending on the domain orientation of the ferroelectric substrate. Such sensitivity to ferroelectric substrate polarization opens the possibility for ferroelectric nonvolatile gating of transition metal dichalcogenides in scalable devices fabricated free of exfoliation and transfer. PMID:25909996

  18. 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.

  19. Giant electrocaloric effect in ferroelectric nanotubes near room temperature

    PubMed Central

    Liu, Man; Wang, Jie

    2015-01-01

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

  20. Magnetoelectric Coupling, Ferroelectricity, and Magnetic Memory Effect in Double Perovskite La3Ni2NbO9.

    PubMed

    Dey, K; Indra, A; De, D; Majumdar, S; Giri, S

    2016-05-25

    We observe ferroelectricity in an almost unexplored double perovskite La3Ni2NbO9. Ferroelectricity appears below ∼60 K, which is found to be correlated with the significant magnetostriction. A reasonably large value of spontaneous electric polarization is recorded to be ∼260 μC/m(2) at 10 K for E = 5 kV/cm, which decreases signifi- cantly upon application of a magnetic field (H), suggesting considerable magnetoelectric coupling. The dielectric permittivity is also influenced by H below the ferroelectric transition. The magnetodielectric response scales linearly to the squared magnetization, as described by the Ginzburg-Landau theory. Meticulous studies of static and dynamic features of dc magnetization and frequency dependent ac susceptibility results suggest spin-glass state below 29 K. Intrinsic magnetic memory effect is observed from zero-field cooled magnetization and isothermal remanent magnetization studies, also pointing spin-glass state below 29 K. Appearance of ferroelectricity together with a significant magnetoelectric coupling in absence of conventional long-range magnetic order is promising for searching new magnetoelectric materials. PMID:27136317

  1. The Modification of Ferroelectric Surfaces for Catalysis

    NASA Astrophysics Data System (ADS)

    Herdiech, Matthew William

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

  2. Robust Three-Metallization Back End of Line Process for 0.18 μm Embedded Ferroelectric Random Access Memory

    NASA Astrophysics Data System (ADS)

    Kang, Seung-Kuk; Rhie, Hyoung-Seub; Kim, Hyun-Ho; Koo, Bon-Jae; Joo, Heung-Jin; Park, Jung-Hun; Kang, Young-Min; Choi, Do-Hyun; Lee, Sung-Young; Jeong, Hong-Sik; Kim, Kinam

    2005-04-01

    We developed ferroelectric random access memory (FRAM)-embedded smartcards in which FRAM replaces electrically erasable PROM (EEPROM) and static random access memory (SRAM) to improve the read/write cycle time and endurance of data memories during operation, in which the main time delay retardation observed in EEPROM embedded smartcards occurs because of slow data update time. EEPROM-embedded smartcards have EEPROM, ROM, and SRAM. To utilize FRAM-embedded smartcards, we should integrate submicron ferroelectric capacitors into embedded logic complementary metal oxide semiconductor (CMOS) without the degradation of the ferroelectric properties. We resolved this process issue from the viewpoint of the back end of line (BEOL) process. As a result, we realized a highly reliable sensing window for FRAM-embedded smartcards that were realized by novel integration schemes such as tungsten and barrier metal (BM) technology, multilevel encapsulating (EBL) layer scheme and optimized intermetallic dielectrics (IMD) technology.

  3. Ferroelectricity and ferroelectric resistive switching in sputtered Hf0.5Zr0.5O2 thin films

    NASA Astrophysics Data System (ADS)

    Fan, Zhen; Xiao, Juanxiu; Wang, Jingxian; Zhang, Lei; Deng, Jinyu; Liu, Ziyan; Dong, Zhili; Wang, John; Chen, Jingsheng

    2016-06-01

    Ferroelectric properties and ferroelectric resistive switching (FE-RS) of sputtered Hf0.5Zr0.5O2 (HZO) thin films were investigated. The HZO films with the orthorhombic phase were obtained without capping or post-deposition annealing. Ferroelectricity was demonstrated by polarization-voltage (P-V) hysteresis loops measured in a positive-up negative-down manner and piezoresponse force microscopy. However, defects such as oxygen vacancies caused the films to become leaky. The observed ferroelectricity and semiconducting characteristics led to the FE-RS effect. The FE-RS effect may be explained by a polarization modulated trap-assisted tunneling model. Our study not only provides a facile route to develop ferroelectric HfO2-based thin films but also explores their potential applications in FE-RS memories.

  4. Studies of ferroelectric heterostructure thin films and interfaces via in situ analytical techniques.

    SciTech Connect

    Auciello, O.; Dhote, A.; Gao, Y.; Gruen, D. M.; Im, J.; Irene, E. A.; Krauss, A. R.; Mueller, A. H.; Ramesh, R.

    1999-08-30

    The science and technology of ferroelectric thin films has experienced an explosive development during the last ten years. Low-density non-volatile ferroelectric random access memories (NVFRAMs) are now incorporated in commercial products such as ''smart cards'', while high permittivity capacitors are incorporated in cellular phones. However, substantial work is still needed to develop materials integration strategies for high-density memories. We have demonstrated that the implementation of complementary in situ characterization techniques is critical to understand film growth and interface processes, which play critical roles in film microstructure and properties. We are using uniquely integrated time of flight ion scattering and recoil spectroscopy (TOF-ISARS) and spectroscopic ellipsometry (SE) techniques to perform in situ, real-time studies of film growth processes in the high background gas pressure required to growth ferroelectric thin films. TOF-ISARS provides information on surface processes, while SE permits the investigation of buried interfaces as they are being formed. Recent studies on SrBi{sub 2}Ta{sub 2}O{sub 9} (SBT) and Ba{sub x}Sr{sub 1{minus}x}TiO{sub 3} (BST) film growth and interface processes are discussed.

  5. Modeling and simulation study of novel Double Gate Ferroelectric Junctionless (DGFJL) transistor

    NASA Astrophysics Data System (ADS)

    Mehta, Hema; Kaur, Harsupreet

    2016-09-01

    In this work we have proposed an analytical model for Double Gate Ferroelectric Junctionless Transistor (DGFJL), a novel device, which incorporates the advantages of both Junctionless (JL) transistor and Negative Capacitance phenomenon. A complete drain current model has been developed by using Landau-Khalatnikov equation and parabolic potential approximation to analyze device behavior in different operating regions. It has been demonstrated that DGFJL transistor acts as a step-up voltage transformer and exhibits subthreshold slope values less than 60 mV/dec. In order to assess the advantages offered by the proposed device, extensive comparative study has been done with equivalent Double Gate Junctionless Transistor (DGJL) transistor with gate insulator thickness same as ferroelectric gate stack thickness of DGFJL transistor. It is shown that incorporation of ferroelectric layer can overcome the variability issues observed in JL transistors. The device has been studied over a wide range of parameters and bias conditions to comprehensively investigate the device design guidelines to obtain a better insight into the application of DGFJL as a potential candidate for future technology nodes. The analytical results so derived from the model have been verified with simulated results obtained using ATLAS TCAD simulator and a good agreement has been found.

  6. Low-temperature integration of lead-based ferroelectric capacitors on Si with diffusion barrier layer

    NASA Astrophysics Data System (ADS)

    Liu, B. T.; Maki, K.; Aggarwal, S.; Nagaraj, B.; Nagarajan, V.; Salamanca-Riba, L.; Ramesh, R.; Dhote, A. M.; Auciello, O.

    2002-05-01

    Ferroelectric lead zirconate titanate thin films have been integrated on silicon substrates using Ti-Al-based conducting diffusion barriers produced by sputter deposition. The microstructure of the Ti-Al barrier layer was systematically altered through changes in the sputtering conditions, specifically the power density and deposition pressure. We find that the crystallinity of the Ti-Al film strongly correlates with sputtering power density and ambient i.e., it is amorphous at low power density and/or high deposition pressure, and polycrystalline at high power density and/or low deposition pressure. Electron energy loss spectroscopy studies demonstrate that the amorphous Ti-Al (a-Ti-Al) films contain a higher concentration of dissolved oxygen than crystalline Ti-Al. A low temperature sol-gel process has been used to prepare Pb(Zr,Ti)O3 PZT films at 450 °C on conducting Si wafers with a-Ti-Al conducting barrier layer and La-Sr-Co-O top and bottom electrodes. The excellent ferroelectric properties obtained with the a-Ti-Al barrier provide a promising approach for integration of PZT-based capacitors with silicon transistor technology for the fabrication of nonvolatile ferroelectric memories.

  7. Four-state ferroelectric spin-valve

    PubMed Central

    Quindeau, Andy; Fina, Ignasi; Marti, Xavi; Apachitei, Geanina; Ferrer, Pilar; Nicklin, Chris; Pippel, Eckhard; Hesse, Dietrich; Alexe, Marin

    2015-01-01

    Spin-valves had empowered the giant magnetoresistance (GMR) devices to have memory. The insertion of thin antiferromagnetic (AFM) films allowed two stable magnetic field-induced switchable resistance states persisting in remanence. In this letter, we show that, without the deliberate introduction of such an AFM layer, this functionality is transferred to multiferroic tunnel junctions (MFTJ) allowing us to create a four-state resistive memory device. We observed that the ferroelectric/ferromagnetic interface plays a crucial role in the stabilization of the exchange bias, which ultimately leads to four robust electro tunnel electro resistance (TER) and tunnel magneto resistance (TMR) states in the junction. PMID:25961513

  8. Emergence of ferroelectricity in antiferroelectric nanostructures.

    PubMed

    Mani, B K; Herchig, R; Glazkova, E; Lisenkov, S; Ponomareva, I

    2016-05-13

    First-principles-based finite-temperature simulations are used to predict the emergence of ferroelectricity in antiferroelectric nanostructures made of PbZrO3. The phenomenon is expected to occur in antiferroelectric nanodots, nanowires, and thin films with good surface charge compensation and can be explained by the recently proposed surface effect [1]. Our computations provide a microscopic insight into the equilibrium phases, phase competition, and electrical properties of PbZrO3 nanostructures. The dependence of these properties on the electrical boundary conditions and nanostructure size is investigated. PMID:27039877

  9. Asymmetry in ferroelectric polymer laminate composites

    SciTech Connect

    Newman, B.A.; Scheinbeim, J.I.; Su, Ji

    1996-10-01

    Studies of the ferroelectric and piezoelectric properties of composite bilaminates of poly(vinylidene fluoride) and nylon 11 films have shown that the properties of the bilaminates cannot be understood solely in terms of the properties of the individual components. Further, the properties of films which are polarized with the positive voltage on the nylon 11 side are different from those having the positive voltage on the poly(vinylidene fluoride) side. This asymmetry is interpreted as resulting from a region of space charge trapped at the interface between the two layers.

  10. Piezoelectric activity in Perovskite ferroelectric crystals.

    PubMed

    Li, Fei; Wang, Linghang; Jin, Li; Lin, Dabin; Li, Jinglei; Li, Zhenrong; Xu, Zhuo; Zhang, Shujun

    2015-01-01

    Perovskite ferroelectrics (PFs) have been the dominant piezoelectric materials for various electromechanical applications, such as ultrasonic transducers, sensors, and actuators, to name a few. In this review article, the development of PF crystals is introduced, focusing on the crystal growth and piezoelectric activity. The critical factors responsible for the high piezoelectric activity of PFs (i.e., phase transition, monoclinic phase, domain size, relaxor component, dopants, and piezoelectric anisotropy) are surveyed and discussed. A general picture of the present understanding on the high piezoelectricity of PFs is described. At the end of this review, potential approaches to further improve the piezoelectricity of PFs are proposed. PMID:25585387

  11. Ferroelectric domain gratings and Barkhausen spikes in potassium lithium tantalate niobate

    SciTech Connect

    Tong, X.; Yariv, A.; Zhang, M.; Agranat, A.J.; Hofmeister, R.; Leyva, V.

    1997-04-01

    The observation of Barkhausen current spikes during the recording of volume phase holograms in potassium lithium tantalate niobate is reported on. These spikes are due to the ferroelectric domain reversal induced by photorefractive space charge fields. Both {open_quotes}small{close_quotes} (1 nA) and {open_quotes}large{close_quotes} (100 nA) spikes are observed, which correspond to micro and macro domain reversal, respectively. The diffraction efficiency can change as much as 50{percent} during a single macrodomain switching. {copyright} {ital 1997 American Institute of Physics.}

  12. A lead-halide perovskite molecular ferroelectric semiconductor.

    PubMed

    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

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

    SciTech Connect

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

    2015-07-13

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

  14. 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

  15. 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

  16. Carrier Density Modulation in Ge Heterostructure by Ferroelectric Switching

    DOE PAGESBeta

    Ponath, Patrick; Fredrickson, Kurt; Posadas, Agham B.; Ren, Yuan; Vasudevan, Rama K.; Okatan, Mahmut Baris; Jesse, Stephen; Aoki, Toshihiro; McCartney, Martha; Smith, David J.; et al

    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

  17. Unravelling and controlling hidden imprint fields in ferroelectric capacitors

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

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

    PubMed

    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

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

    DOE PAGESBeta

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

    2015-07-13

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

  20. Integrated non-planar ferroelectric nanostructures

    NASA Astrophysics Data System (ADS)

    Nonnenmann, Stephen Sommers

    Ferroelectrics (FEs) exhibit stable spontaneous polarization states in the absence of an applied electric field, analogous to other ferroic systems such as ferromagnetics and ferroelastics. Incomplete screening of surface charges along the FE-electrode interface creates a potential gradient across the FE layer. This yields a depolarizing field which greatly suppresses polarization, particularily in systems approaching finite sizes, where surface and interface effects exhibit far more influence than in the bulk. Identifying mechanisms for reducing the detrimental effects of the depolarizing field and maintaining FE stability in finite dimensions remains the largest obstacle in FEs realizing their potential as next generation devices such as electrocaloric coolers, actuators, sensors, photovoltaics, and non-volatile memory elements. This thesis aims to develop a reproducible, versatile synthetic approach towards cylindrical conductive core-ferroelectric perovskite oxide shell nanostructures. The inherent finite curvature produces surface-tension based stresses which may be used to nonlinearily couple to charge, thus mitigating the destabilizing effects of the depolarizing field. This study will show that FE stability is enhanced in curved nanostructures as compared to their planar counterparts. Piezoresponse force microscopy, a modified scan probe technique, will be used to elucidate these effects via imaging and static hysteresis collection. The improved FE stability enables the demonstration of a single, integrated FE field effect transistor test structure, showing nanoscale integration of a FE layer in direct contact with silicon, a notable challenge in developing semiconductor industrial applications.

  1. Development of ferroelectric electron beam diodes

    SciTech Connect

    Flechtner, D.; Ivers, J.D.; Kerslick, G.A.; Nation, J.A.; Schaechter, L.; Zhang, G.

    1995-12-31

    The authors are currently investigating the use of ferroelectric ceramics for electron beam generation. These materials exhibit a spontaneous (saturation) polarization, P{sub s}, of up to 100{mu}C/cm{sup 2}. Emission occurs when the polarization state of the ferroelectric is changed rapidly by an applied electric field, and a fraction of the surface screening charge is released at a gridded electrode. Using a Lead-Zirconate-Titanate (PZT) ceramic as the electron source in a planar 14kV diode geometry they have measured diode current densities of up to 40A/cm{sup 2} with a 5cm gap. The normalized rms emittance of this beam has been measured to be 12{pi} mm-mrad at 8A. Recent results from experiments to extend operation of this diode up to 70 kV, 300 ns pulses will be reported. They are also designing a 20--30 kV, 1 {micro}s system that will be operated in a repetition rate mode. They are planning to use such a system as part of their program to develop compact X-band sources with average power levels in the hundreds of watts range. Using simulation codes, such as EGUN, together with results from analytical work TWT structures are being designed for use with these sources. The advantages of using PPM focusing in both cylindrical or sheet beam configurations are also under investigation.

  2. Functional ferroelectric tunnel junctions on silicon

    NASA Astrophysics Data System (ADS)

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

    2015-07-01

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

  3. Functional ferroelectric tunnel junctions on silicon

    PubMed Central

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

    2015-01-01

    The quest for solid state non-volatility memory devices on silicon with high storage density, high speed, low power consumption has attracted intense research on new materials and novel device architectures. Although flash memory dominates in the non-volatile memory market currently, it has drawbacks, such as low operation speed, and limited cycle endurance, which prevents it from becoming the “universal memory”. In this report, we demonstrate ferroelectric tunnel junctions (Pt/BaTiO3/La0.67Sr0.33MnO3) epitaxially grown on silicon substrates. X-ray diffraction spectra and high resolution transmission electron microscope images prove the high epitaxial quality of the single crystal perovskite films grown on silicon. Furthermore, the write speed, data retention and fatigue properties of the device compare favorably with flash memories. The results prove that the silicon-based ferroelectric tunnel junction is a very promising candidate for application in future non-volatile memories. PMID:26215429

  4. Ferroelectric Liquid Crystals In Aerodynamic Testing

    NASA Technical Reports Server (NTRS)

    Parmar, Devendra S.; Holmes, Harlan K.

    1994-01-01

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

  5. Improper ferroelectricity: A theoretical and experimental investigation

    NASA Astrophysics Data System (ADS)

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

    1984-02-01

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

  6. Prediction of a native ferroelectric metal

    PubMed Central

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

    2016-01-01

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

  7. Raman spectroscopic studies of disordered ferroelectric oxides

    NASA Astrophysics Data System (ADS)

    Savvinov, Alexey A.

    Relaxational properties of compositionally disordered AB03 perovskite oxides were studied. These oxides are the prototypical soft ferroelectric (FE) mode systems, and their interesting dipolar relaxational properties are determined by their long, strongly temperature-dependent correlation lengths for the dipolar interactions. The simple cases involve dilute chemical substitutions in the incipient ferroelectrics KTaO3 and SrTiO3, which exhibit relatively weak, low-temperature Debye-type relaxations. More complicated dipolar interactions are seen in B-site disordered Nb-doped KTaO3, which exhibits glass-like relaxor and relaxor-to-ferroelectric crossover behaviors at low temperatures. Finally, there is a class of more complex perovskites represented by PMN, PZN-PT and the PLT that exhibit strong, high-temperature relaxor and/or ferroelectric properties. The renewed interest in the KTa1-xNbxO (KTN) mixed perovskite materials, especially in high quality thin films, is connected with their remarkable dielectric properties in the dilute compositions. Off-center Nb ions in the highly polarizable KTaO3 lattice provide a drastic increase in the dielectric peak, up to 20 times in comparison with the pure KTaO3 and KNbO3. The effects of the substrate and the symmetry-breaking defects on their vibration spectra were studied by micro-Raman spectroscopy. An anomalous residual intensity of the forbidden first-order scattering modes in the cubic paraelectric phase of the KTN films was connected with the formation of polar microregions even far above the bulk Tc. On the whole, the KTN film behavior shows the existence of specific defects enhancing the perovskite unit cell in the film so that the activity of off-center Nb ions increases in producing larger electric dipoles and extending the precursor phase above Tc. In diluted compositions with low Nb concentrations KTN materials exhibit formation of polar nano regions and relaxor like behavior. This behavior is analogous with

  8. Ferroelectric based catalysis: Switchable surface chemistry

    NASA Astrophysics Data System (ADS)

    Kakekhani, Arvin; Ismail-Beigi, Sohrab

    2015-03-01

    We describe a new class of catalysts that uses an epitaxial monolayer of a transition metal oxide on a ferroelectric substrate. The ferroelectric polarization switches the surface chemistry between strongly adsorptive and strongly desorptive regimes, circumventing difficulties encountered on non-switchable catalytic surfaces where the Sabatier principle dictates a moderate surface-molecule interaction strength. This method is general and can, in principle, be applied to many reactions, and for each case the choice of the transition oxide monolayer can be optimized. Here, as a specific example, we show how simultaneous NOx direct decomposition (into N2 and O2) and CO oxidation can be achieved efficiently on CrO2 terminated PbTiO3, while circumventing oxygen (and sulfur) poisoning issues. One should note that NOx direct decomposition has been an open challenge in automotive emission control industry. Our method can expand the range of catalytically active elements to those which are not conventionally considered for catalysis and which are more economical, e.g., Cr (for NOx direct decomposition and CO oxidation) instead of canonical precious metal catalysts. Primary support from Toyota Motor Engineering and Manufacturing, North America, Inc.

  9. Benefits and Risks of Electronic Medical Record (EMR): An Interpretive Analysis of Healthcare Consumers' Perceptions of an Evolving Health Information Systems Technology

    ERIC Educational Resources Information Center

    Thompson, Chester D.

    2013-01-01

    The purpose of this study is to explore healthcare consumers' perceptions of their Electronic Medical Records (EMRs). Although there have been numerous studies regarding EMRs, there have been minimal, if any, research that explores healthcare consumers' awareness of this technology and the social implications that result. As consumers' health…

  10. High temperature coefficient of resistance for a ferroelectric tunnel junction

    SciTech Connect

    Zhao, Xiaolin; Tian, Bobo; Liu, Bolu; Wang, Xudong; Huang, Hai; Wang, Jianlu E-mail: xjmeng@mail.sitp.ac.cn; Zou, Yuhong; Sun, Shuo; Lin, Tie; Han, Li; Sun, Jinglan; Meng, Xiangjian E-mail: xjmeng@mail.sitp.ac.cn; Chu, Junhao

    2015-08-10

    An infrared detector is proposed that is based on a ferroelectric tunnel junction (FTJ) working under bolometer-like principles. Electron tunneling, either direct or indirect, through the ferroelectric barrier depends on the temperature of the devices. During tunneling, infrared radiation alters the polarization of the ferroelectric film via pyroelectricity, resulting in a change in the barrier height of the tunnel junction. A high temperature coefficient of resistance of up to −3.86% was observed at room temperature. These results show that the FTJ structure has potential to be adapted for use in uncooled infrared detectors.

  11. Tunable and stable in time ferroelectric imprint through polarization coupling

    NASA Astrophysics Data System (ADS)

    Ghosh, Anirban; Koster, Gertjan; Rijnders, Guus

    2016-06-01

    Here we demonstrate a method to tune a ferroelectric imprint, which is stable in time, based on the coupling between the non-switchable polarization of ZnO and switchable polarization of PbZrxTi(1-x)O3. SrRuO3/PbZrxTi(1-x)O3/ZnO/SrRuO3 heterostructures were grown with different ZnO thicknesses. It is shown that the coercive voltages and ferroelectric imprint vary linearly with the thickness of ZnO. It is also demonstrated that the ferroelectric imprint remains stable with electric field cycling and electric field stress assisted aging.

  12. High temperature coefficient of resistance for a ferroelectric tunnel junction

    NASA Astrophysics Data System (ADS)

    Zhao, Xiaolin; Wang, Jianlu; Tian, Bobo; Liu, Bolu; Wang, Xudong; Huang, Hai; Zou, Yuhong; Sun, Shuo; Lin, Tie; Han, Li; Sun, Jinglan; Meng, Xiangjian; Chu, Junhao

    2015-08-01

    An infrared detector is proposed that is based on a ferroelectric tunnel junction (FTJ) working under bolometer-like principles. Electron tunneling, either direct or indirect, through the ferroelectric barrier depends on the temperature of the devices. During tunneling, infrared radiation alters the polarization of the ferroelectric film via pyroelectricity, resulting in a change in the barrier height of the tunnel junction. A high temperature coefficient of resistance of up to -3.86% was observed at room temperature. These results show that the FTJ structure has potential to be adapted for use in uncooled infrared detectors.

  13. Switching dynamics of ferroelectric Langmuir-Blodgett copolymer films

    NASA Astrophysics Data System (ADS)

    Othon, Christina M.

    Ferroelectric switching dynamics in ferroelectric copolymer films of poly(vinylidene fluoride-trifluoroethylene) can vary over nine orders of magnitude; 100 seconds for the slowest ultrathin (1-50 nm) Langmuir-Blodgett films to 100 ns for the fastest polymorphous spin-coat films (˜50 mum thick). These ultra-thin films share many of the same ferroelectric properties of bulk films such as polarization, phase transition temperatures, crystalline structure, and high electrical resistance (>10 MO). The slow nature of switching in ultrathin films is believed to be caused by the intrinsic nature of the switching. The polarization is no longer switching by nucleation and domain wall growth enabled by defects and nanostructures in the polymorphous samples. We investigate this hypothesis by the introduction of defects in the form of nucleation sites and/or grain boundaries by electron irradiation, production of individual ferroelectric nano-crystals, and the introduction of domain wall boundaries through Direct Laser Interference Patterning (DLIP). Electron-irradiation was performed for a large range of doses from 16 to 110 Mrad, on ultra thin films 36 nm thick. It was thought that the defects introduced by electron irradiation could act as nucleation sites, promoting faster switching. However, the primary effect of electron irradiation was the decrease in crystallinity and therefore the fraction of ferroelectric material. Even for lower doses the increase in switching speed was negligible in comparison to the loss of ferroelectricity. The introduction of false domain walls through laser annealing was used to produce more complex and controlled shapes than given by the nanomesas. We investigated patterning by continuous-wave direct write, and by pulsed laser irradiation DLIP. We have demonstrated the ability to pattern films reversibly into films of ferroelectric regions surrounded by paraelectric phase, as well as irreversibly ferroelectric regions surrounded by melted

  14. Domain-Enhanced Interlayer Coupling in Ferroelectric/Paraelectric Superlattices

    NASA Astrophysics Data System (ADS)

    Stephanovich, V. A.; Luk'yanchuk, I. A.; Karkut, M. G.

    2005-02-01

    We investigate the ferroelectric phase transition and domain formation in a periodic superlattice consisting of alternate ferroelectric (FE) and paraelectric (PE) layers of nanometric thickness. We find that the polarization domains formed in the different FE layers can interact with each other via the PE layers. By coupling the electrostatic equations with those obtained by minimizing the Ginzburg-Landau functional, we calculate the critical temperature of transition Tc as a function of the FE/PE superlattice wavelength Λ and quantitatively explain the recent experimental observation of a thickness dependence of the ferroelectric transition temperature in KTaO3/KNbO3 strained-layer superlattices.

  15. Electrocaloric effect in ferroelectric nanowires from atomistic simulations

    PubMed Central

    Herchig, R.; Chang, C.-M.; Mani, B. K.; Ponomareva, I.

    2015-01-01

    Electrocaloric effect is presently under active investigation owing to both the recent discoveries of giant electrocaloric effects and its potential for solid state cooling applications. We use first-principles-based direct simulations to predict the electrocaloric temperature change in ferroelectric ultrathin nanowires. Our findings suggest that in nanowires with axial polarization direction the maximum electrocaloric response is reduced when compared to bulk, while the room temperature electrocaloric properties can be enhanced by tuning the ferroelectric transition temperature. The potential of ferroelectric nanowires for electrocaloric cooling applications is discussed. PMID:26612267

  16. Thin-Layer Composite Unimorph Ferroelectric Driver Sensor Properties

    NASA Technical Reports Server (NTRS)

    Mossi, Karla M.; Selby, Gregory V.; Bryant, Robert G.

    1998-01-01

    Tests were conducted on 13 different configurations of a new class of piezoelectric devices called THUNDER (thin layer composite unimorph ferroelectric driver and sensor). These configurations consisted of a combination of 1, 3, 5, 7, and 9 layers of 25.4 micron thick aluminium as a backing material, with and without a top layer of 25.4 micrometer aluminum. All of these configurations used the same piezoelectric ceramic wafer (PZT-5A) with dimensions of 5.08 x 3.81 x 0.018 cm. The above configurations were tested at two stages of the manufacturing process: before and after repoling. The parameters measured included frequency, driving voltage. displacement, capacitance, and radius of curvature. An optic sensor recorded the displacement at a fixed voltage(100 - 400 V peak to peak) over a predetermined frequency range (1 - 1000 Hz). These displacement measurements were performed using a computer that controlled the process of activating and measuring the displacement of the device. A parameter alpha was defined which can be used to predict the which configuration will produce the most displacement for a free standing device.

  17. Less Contact Ballistogram Recording during Sleep as a Perspective Technology for the Medical Monitoring System in a Mission to Mars

    NASA Astrophysics Data System (ADS)

    Baevsky, R. M.; Bogomolov, V. V.; Funtova, I. I.

    strong argument for success of a future Martian mission is absence of pathologies developed in cosmonauts following one-year or longer space flights that might forbid further gradual extension of piloted missions. However, functional shifts in the neurohormonal regulation revealed during the long-term Mir missions suggest that homeostasis of the vital important body systems is maintained owing to active functioning of the regulatory mechanisms (Grigoriev A.I. et al., 1998). Since overstrain of these mechanisms constitutes one of the main factors of risk of diseases, it is important to provide unfailing and systematic monitoring of the body regulation functional reserves. night ballistocardiography, made it possible to obtain data on super-slow heart rhythm fluctuations reflective of activation of the neurohormonal regulation (Baevsky R.M. et al., 1999). Analysis of the data showed that on a background of extended exposure of the human organism to various stressful factors the cardiovascular homeostasis is maintained through consecutive recruitment in adaptation of higher levels of regulation of the physiological systems (Grigoriev A.I., Baevsky R.M., 2001). This validates the hypothesis concerning the role of the higher autonomous centers in long-term adaptation to the spaceflight factors and opens up the new way to diagnosis and prediction of the human body functional reserves. It was first demonstrated in space during the Mir primary mission 9 in 1991. Sensor-accelerometer secured to cosmonaut's sleeping bag registered micromovements conditioned by the heart, respiratory and motor activities of a sleeping cosmonaut. The joint Russian-Austrian space investigations in 1992-1995 resulted in technology refinement and enhancement. Advantages of medical monitoring during sleep are obvious not only because of the time saving and opportunity to receive systematically information pertaining to the crew health. Records allow, to begin with, evaluate the functional state in

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

    NASA Astrophysics Data System (ADS)

    Cheong, Sang-Wook; Rutgers Center For Emergent Materials Team

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

  19. Optical probe, local fields, and Lorentz factor in ferroelectrics

    NASA Astrophysics Data System (ADS)

    Blinov, L. M.; Lazarev, V. V.; Palto, S. P.; Yudin, S. G.

    2014-06-01

    An optical probe is suggested that allows measurements of the local field and Lorentz factor ( L) in ferroelectric medium. The copolymer poly (vinylidene fluoride/trifluoroethylene) is mixed with Pd-tetraphenylporphyrin (TPP-Pd) that has a very narrow absorption band. Thus, TPP-Pd serves as a molecular optical probe of the local field. During the switching of the electric field lower than the coercive one the factor L of an unpolarized ferroelectric mixture is found to be of about 1/3 that corresponds to the random distribution of molecular dipoles in the ferroelectric. With increasing field, the dipole orientation acquires a lower symmetry and L tends to zero as predicted by lattice sum calculations for vinylidene fluoride. The knowledge of the field dependence of L and the usage of the optical probe makes it possible to measure directly the local and macroscopic fields in the individual elements of various ferroelectric-dielectric heterostructures.

  20. Emergence of room-temperature ferroelectricity at reduced dimensions.

    PubMed

    Lee, D; Lu, H; Gu, Y; Choi, S-Y; Li, S-D; Ryu, S; Paudel, T R; Song, K; Mikheev, E; Lee, S; Stemmer, S; Tenne, D A; Oh, S H; Tsymbal, E Y; Wu, X; Chen, L-Q; Gruverman, A; Eom, C B

    2015-09-18

    The enhancement of the functional properties of materials at reduced dimensions is crucial for continuous advancements in nanoelectronic applications. Here, we report that the scale reduction leads to the emergence of an important functional property, ferroelectricity, challenging the long-standing notion that ferroelectricity is inevitably suppressed at the scale of a few nanometers. A combination of theoretical calculations, electrical measurements, and structural analyses provides evidence of room-temperature ferroelectricity in strain-free epitaxial nanometer-thick films of otherwise nonferroelectric strontium titanate (SrTiO3). We show that electrically induced alignment of naturally existing polar nanoregions is responsible for the appearance of a stable net ferroelectric polarization in these films. This finding can be useful for the development of low-dimensional material systems with enhanced functional properties relevant to emerging nanoelectronic devices. PMID:26383947

  1. Ferroelectric and ferromagnetic properties of Gd substituted nickel ferrite

    NASA Astrophysics Data System (ADS)

    Kamala Bharathi, K.; Markandeyulu, G.

    2008-04-01

    Ferromagnetic and ferroelectric characteristics of Gd substituted nickel ferrite (NiOṡFe1.925Gd0.075O3) were investigated. The material formed in the cubic inverse spinel phase and in addition, a small amount of GdFeO3 phase was identified. A small distortion of the cubic lattice was observed upon the substitution of Fe by Gd in the B site. Substitution of Gd for Fe lowered the saturation magnetization. However, the saturation magnetostriction is seen not to change significantly by the substitution of Gd. From the temperature variation of dielectric constant measurement, the ferroelectric transition temperature was found to be 512K. The existence of the ferroelectricity was confirmed from the ferroelectric loop. The (high) dielectric constant with frequency is seen to reveal a dispersion of relaxation times.

  2. Fast Ferroelectric L-Band Tuner for ILC Cavities

    SciTech Connect

    Hirshfield, Jay L

    2010-03-15

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

  3. Enhanced piezoelectric response in the artificial ferroelectric polymer multilayers

    SciTech Connect

    Zhao, X. L.; Wang, J. L. E-mail: lin-tie@mail.sitp.ac.cn; Tian, B. B.; Liu, B. L.; Wang, X. D.; Sun, S.; Zou, Y. H.; Lin, T. E-mail: lin-tie@mail.sitp.ac.cn; Sun, J. L.; Meng, X. J.; Chu, J. H.

    2014-12-01

    An actuator with a high piezoelectric response, the ferroelectric polymer multilayer actuator, is described. The ferroelectric polymer multilayers consisting of alternative ferroelectric poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) copolymer and relaxor poly(vinylidene fluoride-trifluoroethylene-chlorofloroethylene) (P(VDF-TrFE-CFE)) terpolymer with different periodicities and fixed total thickness are prepared by the Langmuir-Blodgett technique. Both X-ray diffraction and Raman spectroscopic measurements indicate that the structure of the multilayer with thin alternating layer is similar to that of the ferroelectric copolymer. Compared with that of the copolymer, it is found that the piezoelectric coefficient of the multilayer could be improved by 57%. We attributed the enhanced piezoelectric response of the multilayers to the internal electric fields that arises from the electrostatic couplings between different layers.

  4. Ferroelectricity in high-density H2O ice.

    PubMed

    Caracas, Razvan; Hemley, Russell J

    2015-04-01

    The origin of longstanding anomalies in experimental studies of the dense solid phases of H2O 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. The presence of local electric fields triggers the preferential parallel orientation of the water molecules in the structure, which could be stabilized in bulk using new high-pressure techniques. PMID:25854247

  5. Local structure and shaping of ferroelectric domain walls for photonic applications

    NASA Astrophysics Data System (ADS)

    Scrymgeour, David

    Ferroelectric lithium niobate (LiNbO3) and lithium tantalate (LiTaO3) have emerged as key technological materials for use in photonic applications, due to the high quality of crystal growth, optical transparency over a wide frequency range (240nm--4.5 mum), and their large electro-optic and nonlinear optical coefficients. Emerging fields of optical communications, optical data storage, displays, biomedical devices, sensing, and defense applications will all rely heavily on such ferroelectrics as a versatile solid-state photonic platform. Diverse functionalities can be created in these materials simply through the patterning of the ferroelectric domains. By creating specific domain features in these materials, it is possible to create new laser wavelengths from existing sources as well as active electro-optic structures that can dynamically focus, shape and steer light. However, the process of domain shaping today is mostly empirical, based on trial-and-error rather than sound, predictive science. The central focus of this thesis work is to develop a fundamental understanding of how to shape and control domain walls in ferroelectrics, specifically in lithium niobate and lithium tantalate, for photonic applications. An understanding of the domain wall phenomena is being approached at two levels: the macroscale and the nanoscale. On the macroscale, different electric field poling techniques are developed and used to create domain shapes of arbitrary orientation. A theoretical framework based on Ginzburg-Landau-Devonshire theory is developed to determine the preferred domain wall shapes. Differences in the poling characteristics and domain wall shapes between the two materials as well as differences in material composition relates to nonstoichiometric defects in the crystal. At the nanoscale, these defects influence the local electromechanical properties of the domain wall. Understanding from both of these approaches has been used to design and create photonic devices

  6. Few-Volt Operation of Printed Organic Ferroelectric Capacitor.

    PubMed

    Noda, Yuki; Yamada, Toshikazu; Kobayashi, Kensuke; Kumai, Reiji; Horiuchi, Sachio; Kagawa, Fumitaka; Hasegawa, Tatsuo

    2015-11-01

    The fabrication of single-crystalline thin-film arrays for an organic ferroelectric small molecule is achieved by a simple solution process without additional thermal annealing. Based on a cooperative proton tautomerism through a hydrogen-bonding network, films show the polarity switching with an operating voltage of less than 5 V at room temperature. This approach provides a low-cost and eco-friendly fabrication of ferroelectric devices. PMID:26419689

  7. Electric Control of Spin Helicity in a Magnetic Ferroelectric

    SciTech Connect

    Yamasaki, Y.; Goto, T.; Sagayama, H.; Matsuura, M.; Hirota, K.; Arima, T.; Tokura, Y.

    2007-04-06

    Magnetic ferroelectrics or multiferroics, which are currently extensively explored, may provide a good arena to realize a novel magnetoelectric function. Here we demonstrate the genuine electric control of the spiral magnetic structure in one such magnetic ferroelectric, TbMnO{sub 3}. A spin-polarized neutron scattering experiment clearly shows that the spin helicity, clockwise or counterclockwise, is controlled by the direction of spontaneous polarization and hence by the polarity of the small electric field applied on cooling.

  8. Studies of ferroelectric and dielectric properties of pure and doped barium titanate prepared by sol-gel method

    NASA Astrophysics Data System (ADS)

    Bisen, Supriya; Mishra, Ashutosh; Jarabana, Kanaka M.

    2016-05-01

    In this work, Barium Titanate (BaTiO3) powders were synthesized via Sol-Gel auto combustion method using citric acid as a chelating agent. We study the behavior of ferroelectric and dielectric properties of pure and doped BaTiO3 on different concentration. To understand the phase and structure of the powder calcined at 900°C were characterized by X-ray Diffraction shows that tetragonal phase is dominant for pure and doped BTO and data fitted by Rietveld Refinement. Electric and Dielectric properties were characterized by P-E Hysteresis and Dielectric measurement. In P-E measurement ferroelectric loop tracer applied for different voltage. The temperature dependant dielectric constant behavior was observed as a function of frequency recorded on hp-Hewlett Packard 4192A, LF impedance, 5Hz-13Hz analyzer.

  9. Exotic exchange bias at epitaxial ferroelectric-ferromagnetic interfaces

    SciTech Connect

    Paul, Amitesh Reitinger, Christoph; Kreuzpaintner, Wolfgang; Böni, Peter; Autieri, Carmine; Sanyal, Biplab; Jutimoosik, Jaru; Yimnirun, Rattikorn; Bern, Francis; Esquinazi, Pablo; Korelis, Panagiotis

    2014-07-14

    Multiferroics in spintronics have opened up opportunities for future technological developments, particularly in the field of ferroelectric (FE)-ferromagnetic (FM) oxide interfaces with functionalities. We find strong exchange bias shifts (up to 84 Oe) upon field cooling in metal-oxide (Fe/BaTiO{sub 3}) films combining FM and FE layers. The saturation magnetic moment of the FM layer is also significantly higher than in bulk (3.0 ± 0.2 μ{sub B}/atom) and the reversal mechanism occurs via a domain nucleation process. X-ray absorption spectroscopy at the Fe K-edge and Ba L3-edge indicate presence of few monolayers of antiferromagnetic FeO at the interface without the formation of any BaFeO{sub 3} layer. Polarized neutron reflectometry corroborates with our magnetization data as we perform depth profiling of the magnetic and structural densities in these bilayers. Our first principles density functional calculations support the formation of antiferromagnetic FeO layers at the interface along with an enhancement of Fe magnetic moments in the inner ferromagnetic layers.

  10. Diffuse Scattering from Lead-Containing Ferroelectric Perovskite Oxides

    DOE PAGESBeta

    Goossens, D. J.

    2013-01-01

    Ferroelectric materials rely on some type of non-centrosymmetric displacement correlations to give rise to a macroscopic polarisation. These displacements can show short-range order (SRO) that is reflective of the local chemistry, and so studying it reveals important information about how the structure gives rise to the technologically useful properties. A key means of exploring this SRO is diffuse scattering. Conventional structural studies use Bragg peak intensitiesto determine the average structure. In a single crystal diffuse scattering (SCDS) experiment, the coherent scattered intensity is measured at non-integer Miller indices, and can be used to examine the population of local configurations. Thismore » is because the diffuse scattering is sensitive to two-body averages, whereas the Bragg intensity gives single-body averages. This review outlines key results of SCDS studies on several materials and explores the similarities and differences in their diffuse scattering. Random strains are considered, as are models based on a phonon-like picture or a more local-chemistry oriented picture. Limitations of the technique are discussed.« less

  11. Ultralow-power ferroelectric memory for SoC

    NASA Astrophysics Data System (ADS)

    Natarajan, Sreedhar; Alvandpour, Atila

    2004-03-01

    The endurance of a FRAM is 1014 cycles with better retention times (>10 years). FRAM's have fast read/write access, low standby current, scalable and capable of ultra-low voltage operation. FRAM's share architectural features such as addressing schemes and I/O circuitry with other types of random access memories (DRAMs), but they have distinct features with respect to accessing the stored data, sensing, and overall circuit topology. The FRAM is a great advantage for SoC and wireless and mobile products, since it supports non-volatility but also delivers a fast memory access. Today's 1T/1C FRAM have an access time of 30 nS, a cycle time of 35 nS at 1.2 V power supply in a standard CMOS process with 2 mask adders. The cell size of a FRAM is comparable to that of a planar DRAM and is 3 - 4x denser than SRAM. This paper outlines the circuit innovations in embedded ferroelectric memories, and will cover the architecture, reference circuits, sense amplifiers, reliability issues and references to other memory technologies.

  12. Domain wall conduction in multiaxial ferroelectrics

    SciTech Connect

    Eliseev, E. A.; Morozovska, A. N.; Svechnikov, S. V.; Maksymovych, Petro; Kalinin, Sergei V

    2012-01-01

    The conductance of domain wall structures consisting of either stripes or cylindrical domains in multiaxial ferroelectric-semiconductors is analyzed. The effects of the flexoelectric coupling, domain size, wall tilt, and curvature on charge accumulation are analyzed using the Landau-Ginsburg Devonshire theory for polarization vector combined with the Poisson equation for charge distributions. The proximity and size effect of the electron and donor accumulation/depletion by thin stripe domains and cylindrical nanodomains are revealed. In contrast to thick domain stripes and wider cylindrical domains, in which the carrier accumulation (and so the static conductivity) sharply increases at the domain walls only, small nanodomains of radii less than 5-10 correlation lengths appeared conducting across the entire cross-section. Implications of such conductive nanosized channels may be promising for nanoelectronics.

  13. Spatial Rogue Waves in Photorefractive Ferroelectrics

    NASA Astrophysics Data System (ADS)

    Pierangeli, D.; Di Mei, F.; Conti, C.; Agranat, A. J.; DelRe, E.

    2015-08-01

    Rogue waves are observed as light propagates in the extreme nonlinear regime that occurs when a photorefractive ferroelectric crystal is undergoing a structural phase transition. The transmitted spatial light distribution contains bright localized spots of anomalously large intensity that follow a signature long-tail statistics that disappears as the nonlinearity is weakened. The isolated wave events form as out-of-equilibrium response and disorder enhance the Kerr-saturated nonlinearity at the critical point. Self-similarity associable to the individual observed filaments and numerical simulations of the generalized nonlinear Schrödinger equation suggests that dynamics of soliton fusions and scale invariance can microscopically play an important role in the observed rogue intensities and statistics.

  14. Nanoporous piezo- and ferroelectric thin films.

    PubMed

    Ferreira, Paula; Hou, Ru Z; Wu, Aiying; Willinger, Marc-Georg; Vilarinho, Paula M; Mosa, Jadra; Laberty-Robert, Christel; Boissière, Cédric; Grosso, David; Sanchez, Clément

    2012-02-01

    Nanoporous barium titanate and lead titanate thin films (∼100 nm calculated from ellipsometric data) are prepared starting from sol-gel solutions modified with a commercially available block-copolymer and evaporation-induced self-assembly methodology. The tuning of the thermal treatment followed by in situ ellipsometry allows the decomposition of the organic components and of the structuring agent leading to the formation of porous tetragonal crystalline perovskite structures as observed by XRD, HRTEM, SEM, and ellipsoporosimetry. Both nanoporous barium titanate and lead titanate thin films present local piezoelectric and ferroelectric behavior measured by piezoresponse force microscopy (PFM), being promising platforms for the preparation of the generation of new multifunctional systems. PMID:22206407

  15. Topological Point Defects in Relaxor Ferroelectrics

    NASA Astrophysics Data System (ADS)

    Nahas, Y.; Prokhorenko, S.; Kornev, I.; Bellaiche, L.

    2016-03-01

    First-principles-based effective Hamiltonian simulations are used to reveal the hidden connection between topological defects (hedgehogs and antihedgehogs) and relaxor behavior. Such defects are discovered to predominantly lie at the border of polar nanoregions in both Ba (Zr0.5 Ti0.5 )O3 (BZT) and Pb (Sc0.5 Nb0.5 )O3 (PSN) systems, and the temperature dependency of their density allows us to distinguish between noncanonical (PSN) and canonical (BZT) relaxor behaviors (via the presence or absence of a crossing of a percolation threshold). This density also possesses an inflection point at precisely the temperature for which the dielectric response peaks. Moreover, hedgehogs and antihedgehogs are found to be mobile excitations, and the dynamical nature of their annihilation is demonstrated (using simple hydrodynamical arguments) to follows laws, such as those of Vogel-Fulcher and Arrhenius, that are characteristic of dipolar relaxation kinetics of relaxor ferroelectrics.

  16. Topological Point Defects in Relaxor Ferroelectrics.

    PubMed

    Nahas, Y; Prokhorenko, S; Kornev, I; Bellaiche, L

    2016-03-25

    First-principles-based effective Hamiltonian simulations are used to reveal the hidden connection between topological defects (hedgehogs and antihedgehogs) and relaxor behavior. Such defects are discovered to predominantly lie at the border of polar nanoregions in both Ba(Zr_{0.5}Ti_{0.5})O_{3} (BZT) and Pb(Sc_{0.5}Nb_{0.5})O_{3} (PSN) systems, and the temperature dependency of their density allows us to distinguish between noncanonical (PSN) and canonical (BZT) relaxor behaviors (via the presence or absence of a crossing of a percolation threshold). This density also possesses an inflection point at precisely the temperature for which the dielectric response peaks. Moreover, hedgehogs and antihedgehogs are found to be mobile excitations, and the dynamical nature of their annihilation is demonstrated (using simple hydrodynamical arguments) to follows laws, such as those of Vogel-Fulcher and Arrhenius, that are characteristic of dipolar relaxation kinetics of relaxor ferroelectrics. PMID:27058101

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

    SciTech Connect

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

    2015-07-13

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

  18. Nanostructured ferroelectrics: fabrication and structure-property relations.

    PubMed

    Han, Hee; Kim, Yunseok; Alexe, Marin; Hesse, Dietrich; Lee, Woo

    2011-10-25

    With the continued demand for ultrahigh density ferroelectric data storage applications, it is becoming increasingly important to scale the dimension of ferroelectrics down to the nanometer-scale region and to thoroughly understand the effects of miniaturization on the materials properties. Upon reduction of the physical dimension of the material, the change in physical properties associated with size reduction becomes extremely difficult to characterize and to understand because of a complicated interplay between structures, surface properties, strain effects from substrates, domain nucleation, and wall motions. In this Review, the recent progress in fabrication and structure-property relations of nanostructured ferroelectric oxides is summarized. Various fabrication approaches are reviewed, with special emphasis on a newly developed stencil-based method for fabricating ferroelectric nanocapacitors, and advantages and limitations of the processes are discussed. Stress-induced evolutions of domain structures upon reduction of the dimension of the material and their implications on the electrical properties are discussed in detail. Distinct domain nucleation, growth, and propagation behaviors in nanometer-scale ferroelectric capacitors are discussed and compared to those of micrometer-scale counterparts. The structural effect of ferroelectric nanocapacitors on the domain switching behavior and cross-talk between neighboring capacitors under external electric field is reviewed. PMID:21919083

  19. New modalities of strain-control of ferroelectric thin films

    NASA Astrophysics Data System (ADS)

    Damodaran, Anoop R.; Agar, Joshua C.; Pandya, Shishir; Chen, Zuhuang; Dedon, Liv; Xu, Ruijuan; Apgar, Brent; Saremi, Sahar; Martin, Lane W.

    2016-07-01

    Ferroelectrics, with their spontaneous switchable electric polarization and strong coupling between their electrical, mechanical, thermal, and optical responses, provide functionalities crucial for a diverse range of applications. Over the past decade, there has been significant progress in epitaxial strain engineering of oxide ferroelectric thin films to control and enhance the nature of ferroelectric order, alter ferroelectric susceptibilities, and to create new modes of response which can be harnessed for various applications. This review aims to cover some of the most important discoveries in strain engineering over the past decade and highlight some of the new and emerging approaches for strain control of ferroelectrics. We discuss how these new approaches to strain engineering provide promising routes to control and decouple ferroelectric susceptibilities and create new modes of response not possible in the confines of conventional strain engineering. To conclude, we will provide an overview and prospectus of these new and interesting modalities of strain engineering helping to accelerate their widespread development and implementation in future functional devices.

  20. New modalities of strain-control of ferroelectric thin films.

    PubMed

    Damodaran, Anoop R; Agar, Joshua C; Pandya, Shishir; Chen, Zuhuang; Dedon, Liv; Xu, Ruijuan; Apgar, Brent; Saremi, Sahar; Martin, Lane W

    2016-07-01

    Ferroelectrics, with their spontaneous switchable electric polarization and strong coupling between their electrical, mechanical, thermal, and optical responses, provide functionalities crucial for a diverse range of applications. Over the past decade, there has been significant progress in epitaxial strain engineering of oxide ferroelectric thin films to control and enhance the nature of ferroelectric order, alter ferroelectric susceptibilities, and to create new modes of response which can be harnessed for various applications. This review aims to cover some of the most important discoveries in strain engineering over the past decade and highlight some of the new and emerging approaches for strain control of ferroelectrics. We discuss how these new approaches to strain engineering provide promising routes to control and decouple ferroelectric susceptibilities and create new modes of response not possible in the confines of conventional strain engineering. To conclude, we will provide an overview and prospectus of these new and interesting modalities of strain engineering helping to accelerate their widespread development and implementation in future functional devices. PMID:27187744

  1. 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

  2. Incorporating 3D-printing technology in the design of head-caps and electrode drives for recording neurons in multiple brain regions

    PubMed Central

    DeLucca, Michael V.; Haufler, Darrell; Paré, Denis

    2015-01-01

    Recent advances in recording and computing hardware have enabled laboratories to record the electrical activity of multiple brain regions simultaneously. Lagging behind these technical advances, however, are the methods needed to rapidly produce microdrives and head-caps that can flexibly accommodate different recording configurations. Indeed, most available designs target single or adjacent brain regions, and, if multiple sites are targeted, specially constructed head-caps are used. Here, we present a novel design style, for both microdrives and head-caps, which takes advantage of three-dimensional printing technology. This design facilitates targeting of multiple brain regions in various configurations. Moreover, the parts are easily fabricated in large quantities, with only minor hand-tooling and finishing required. PMID:25652930

  3. Incorporating 3D-printing technology in the design of head-caps and electrode drives for recording neurons in multiple brain regions.

    PubMed

    Headley, Drew B; DeLucca, Michael V; Haufler, Darrell; Paré, Denis

    2015-04-01

    Recent advances in recording and computing hardware have enabled laboratories to record the electrical activity of multiple brain regions simultaneously. Lagging behind these technical advances, however, are the methods needed to rapidly produce microdrives and head-caps that can flexibly accommodate different recording configurations. Indeed, most available designs target single or adjacent brain regions, and, if multiple sites are targeted, specially constructed head-caps are used. Here, we present a novel design style, for both microdrives and head-caps, which takes advantage of three-dimensional printing technology. This design facilitates targeting of multiple brain regions in various configurations. Moreover, the parts are easily fabricated in large quantities, with only minor hand-tooling and finishing required. PMID:25652930

  4. Patient-Perceived Usefulness of Online Electronic Medical Records: Employing Grounded Theory in the Development of Information and Communication Technologies for Use by Patients Living with Chronic Illness

    PubMed Central

    Winkelman, Warren J.; Leonard, Kevin J.; Rossos, Peter G.

    2005-01-01

    Objective: Patient use of online electronic medical records (EMR) holds the potential to improve health outcomes. The purpose of this study is to discover how patients living with chronic inflammatory bowel disease (IBD) value Internet-based patient access to electronic patient records. Design: This was a qualitative, exploratory, descriptive study using in-depth interviews and focus groups of a total of 12 patients with IBD of at least one-year duration at University Health Network, a tertiary care center in Toronto, Ontario. Results: Four themes have been elucidated that comprise a theoretical framework of patient-perceived information and communication technology usefulness: promotion of a sense of illness ownership, of patient-driven communication, of personalized support, and of mutual trust. Conclusions: For patients with chronic IBD, simply providing access to electronic medical records has little usefulness on its own. Useful technology for patients with IBD is multifaceted, self-care promoting, and integrated into the patient's already existing health and psychosocial support infrastructure. The four identified themes can serve as focal points for the evaluation of information technology designed for patient use, thus providing a patient-centered framework for developers seeking to adapt existing EMR systems to patient access and use for the purposes of improving health care quality and health outcomes. Further studies in other populations are needed to enhance generalizability of the emergent theory. PMID:15684128

  5. Application of the ferroelectric materials to ULSI memories

    NASA Astrophysics Data System (ADS)

    Tarui, Yasuo; Hirai, Tadahiko; Teramoto, Kazuhiro; Koike, Hiroshi; Nagashima, Kazuhito

    1997-04-01

    Memory is essential to electronic data processing and continuous efforts are being made to develop improved memory devices. In the era of VLSI, difficulties have arisen with respect to storage capacitance, which must be kept to a certain value while the device dimensions are reduced. This has prompted the adoption of complicated structures like the trench or stack, causing the number of process steps to be increased. The use of high dielectric constant materials has been researched for the extension of DRAM development. Recently, the development of the memories which use the polarization reversal current of the ferroelectric material is rapidly progressing because it enables high speed nonvolatile memory action which generally needed in recent electronic systems. These memories will replace a large portion of the existing memory systems in the near future. However, this is not a perfect solution to the problem, because they are not in accordance with the scaling rule. In this paper, it is shown that ferroelectric memories using the field effect current of a semiconductor by the remanent polarization of the ferroelectric material are in accordance with the scaling rule. The first experimental verification of the non-volatile memory action was reported by Moll and Tarui in 1963 [1]. This basic memory action has been successively used in MFS (metal-ferroelectric-semiconductor) transistors. The ferroelectric memories are nonvolatile and are expected to be high-speed devices, making them suitable for universal applications. However, it is necessary to optimize the interface between the semiconductor and ferroelectric material. Experiments for the prospective devices using CeO 2 or Ce xZr (1- x) O 2 as the buffer insulator layers of the MFIS (metal-ferroelectric-insulator-semiconductor) transistors are described.

  6. Origin of ferroelectricity in high-T(c) magnetic ferroelectric CuO.

    PubMed

    Jin, Guangxi; Cao, Kun; Guo, Guang-Can; He, Lixin

    2012-05-01

    Cupric oxide is a unique magnetic ferroelectric material with a transition temperature significantly higher than the boiling point of liquid nitrogen. However, the mechanism of high-T(c) multiferroicity in CuO remains puzzling. In this Letter, we clarify the mechanism of high-T(c) multiferroicity in CuO by using combined first-principles calculations and an effective hamiltonian model. We find that CuO contains two magnetic sublattices, with strong intrasublattice interactions and weakly frustrated intersublattice interactions. The weak spin frustration leads to incommensurate spin excitations that dramatically enhance the entropy of the multiferroic phase and eventually stabilize that phase in CuO. PMID:22681113

  7. Polarization charge as a reconfigurable quasi-dopant in ferroelectric thin films.

    PubMed

    Crassous, Arnaud; Sluka, Tomas; Tagantsev, Alexander K; Setter, Nava

    2015-07-01

    Impurity elements used as dopants are essential to semiconductor technology for controlling the concentration of charge carriers. Their location in the semiconductor crystal is determined during the fabrication process and remains fixed. However, another possibility exists whereby the concentration of charge carriers is modified using polarization charge as a quasi-dopant, which implies the possibility to write, displace, erase and re-create channels having a metallic-type conductivity inside a wide-bandgap semiconductor matrix. Polarization-charge doping is achieved in ferroelectrics by the creation of charged domain walls. The intentional creation of stable charged domain walls has so far only been reported in BaTiO3 single crystals, with a process that involves cooling the material through its phase transition under a strong electric bias, but this is not a viable technology when real-time reconfigurability is sought in working devices. Here, we demonstrate a technique allowing the creation and nanoscale manipulation of charged domain walls and their action as a real-time doping activator in ferroelectric thin films. Stable individual and multiple conductive channels with various lengths from 3 μm to 100 nm were created, erased and recreated in another location, and their high metallic-type conductivity was verified. This takes the idea of hardware reconfigurable electronics one step forward. PMID:26076468

  8. Polarization charge as a reconfigurable quasi-dopant in ferroelectric thin films

    NASA Astrophysics Data System (ADS)

    Crassous, Arnaud; Sluka, Tomas; Tagantsev, Alexander K.; Setter, Nava

    2015-07-01

    Impurity elements used as dopants are essential to semiconductor technology for controlling the concentration of charge carriers. Their location in the semiconductor crystal is determined during the fabrication process and remains fixed. However, another possibility exists whereby the concentration of charge carriers is modified using polarization charge as a quasi-dopant, which implies the possibility to write, displace, erase and re-create channels having a metallic-type conductivity inside a wide-bandgap semiconductor matrix. Polarization-charge doping is achieved in ferroelectrics by the creation of charged domain walls. The intentional creation of stable charged domain walls has so far only been reported in BaTiO3 single crystals, with a process that involves cooling the material through its phase transition under a strong electric bias, but this is not a viable technology when real-time reconfigurability is sought in working devices. Here, we demonstrate a technique allowing the creation and nanoscale manipulation of charged domain walls and their action as a real-time doping activator in ferroelectric thin films. Stable individual and multiple conductive channels with various lengths from 3 μm to 100 nm were created, erased and recreated in another location, and their high metallic-type conductivity was verified. This takes the idea of hardware reconfigurable electronics one step forward.

  9. Dynamic fragmentation of ferroelectric ceramics using the torsional Kolsky bar

    SciTech Connect

    Costin, L S; Grady, D E

    1983-10-01

    This paper studied the dynamic loading and subsequent fragmentation of four different load zirconate titanate (95/5 PZT) ferroelectric ceramics using a torsional Kolsky bar apparatus. Solid cylinders of the four materials were loaded in torsion at shear strain rates in the range 10/sup 2/ to 10/sup 3/s/sup -1/. Using the strain gage recordings of the incident, reflected and transmitted pulses, the energy required to fragment the specimen was determined for each test. In addition, the fragments resulting from each test were collected and analyzed by various technciques to determine their mass and size distributions. Results show some differences in particle distributions between the different batches of material. However, there is a more significant and consistent difference between the dynamic strength (as measured by the maximum shear stress) and the fragment mass distributions of the virgin material and the pressure depoled material, despite the fact that no differences were detected in the energy of fragmentation. Using earlier analytical results which relate the local kinetic energy of a potential fragment to the surface energy required to create that fragment, a relationship between the distribution of fragments from a test and material properties was derived. Results of tests on PZT as well as other materials such as oil shale, graphite, uranium dioxide and glass indicate a good correlation between the fragment distribution parameter, n, and material properties as predicted by the theory. Finally, the results are analyzed to determine the potential effects of internal stresses on the dynamic strength of the material and its fragmentation characteristics.

  10. Structural studies on ferroelectric and ferrodistortive materials

    NASA Astrophysics Data System (ADS)

    Zou, Mingqin

    The structure of the piezoelectric material 0.68PbMg1/3Nb 2/3O3-0.32PbTiO3 have been studied by single crystal, powder x-ray diffraction techniques over the temperature range from 25°C to 200°C. The existence of twinned structures or coexistence of rhombohedral and tetragonal phases has been shown by the peak distortion of Bragg reflections. Superlattice structure was observed for all experimental PMN-PT crystals. Refinement results showed that the 2 x 2 x 2 superlattice resulted from anti-parallel displacement of oxygen in the adjacent conventional perovskite unit cells. No cation displacement in the paraelectric phase and little in the ferroelectric phase were shown by the refinement results. This unique feature associated with the ferroelectric mechanism of the material was explained by comparison with PbMg1/3Nb2/3O3. The crystals were extensively characterized by using powder x-ray diffraction, Laue back-reflection and electron backscatter diffraction (EBSD) techniques. The detailed orientation information such as misorientation of grains, location of grain boundaries and the orientation distribution was obtained from the automatic orientation mapping with the EBSD technique. The uniform orientation was confirmed for crystals with a "cellular-like" structure. A crystal growth model, the two-dimensional layer mechanism, was proposed by orientation analysis. Based on the model, some important comments were made on orientation problems under general growth conditions. The ferrodistortive phase transitions of tertramethylphosphonium tetrabromozincate [P(CH3)4]2ZnBr4 and tertramethylphosphonium tetraiodonzincate [P(CH3)4]2ZnI4 were thoroughly studied by a single crystal x-ray diffraction technique. An order parameter analysis by application of Landau theory showed that the two compounds undergo first-order phase transitions near a tricritical Lifshitz point. Transitions for both compounds appear to be first order, but with the iodo salt the transition is nearly

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

    SciTech Connect

    Goyal, Amit; Shin, Junsoo

    2015-03-31

    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.

  12. Ferroelectric transistors with improved characteristics at high temperature

    NASA Astrophysics Data System (ADS)

    Salvatore, Giovanni A.; Lattanzio, Livio; Bouvet, Didier; Stolichnov, Igor; Setter, Nava; Ionescu, Adrian M.

    2010-08-01

    We report on the temperature dependence of ferroelectric metal-oxide-semiconductor (MOS) transistors and explain the observed improved characteristics based on the dielectric response of ferroelectric materials close to the Curie temperature. The hysteretic current-voltage static characteristics of a fully depleted silicon-on-insulator transistor, with 40 nm vinylidene fluoride trifluorethylene, and 10 nm SiO2 gate stack, are measured from 300 to 400 K. In contrast with conventional MOS field effect transistors (MOSFETs), the subthreshold swing and the transconductance show, respectively, a minimum and a maximum near the Curie temperature (355 K) of the ferroelectric material. A phenomenological model is proposed based on the Landau-Ginzburg theory. This work demonstrates that a MOSFET with a ferroelectric layer integrated in the gate stack could have nondegraded or even improved subthreshold swing and transconductance at high temperature even though the hysteresis window is reduced. As a consequence, we suggest that for ferroelectric transistors with appropriately designed Curie temperatures, the performance degradation of logic or analog circuits, nowadays operating near 100 °C, could be avoided.

  13. Deterministic Arbitrary Switching of Polarization in a Ferroelectric Thin Film

    SciTech Connect

    Vasudevan, Rama K; Matsumoto, Yuji; Cheng, Xuan; Imai, Akira; Maruyama, Shingo; Xin, Huolin L.; Okatan, Mahmut B; Jesse, Stephen; Kalinin, Sergei V; Nagarajan, Valanoor

    2014-01-01

    Ferroelectrics have been used as memory storage devices, with an upper bound on the total possible memory levels generally dictated by the number of degenerate states allowed by the symmetry of the ferroelectric phase. Here, we introduce a new concept for storage wherein the polarization can be rotated arbitrarily, effectively decoupling it from the crystallographic symmetry of the ferroelectric phase on the mesoscale. By using a Bi5Ti3FeO15-CoFe2O4 film and via Band-Excitation Piezoresponse Force Microscopy, we show the ability to arbitrarily rotate polarization, create a spectrum of switched states, and suggest the reason for the polarization rotation is an abundance of sub-50nm nanodomains. Transmission electron microscopy-based strain mapping confirms significant local strain undulations imparted on the matrix by the CoFe2O4 inclusions, which causes significant local disorder. These experiments point to controlled tuning of polarization rotation in a standard ferroelectric, and hence the potential to greatly extend the attainable densities for ferroelectric memories.

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

    NASA Astrophysics Data System (ADS)

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

    2015-10-01

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

  15. Ferroelectric surface induced electron doping in a zigzag graphene nanoribbon.

    PubMed

    Belletti, G D; Dalosto, S D; Tinte, S

    2016-11-01

    The interface between a zigzag graphene nanoribbon (zGNR) and the ferroelectric PbTiO3 (0 0 1) surface is studied through first-principles calculations. We investigate how the electric polarization normal to the surface tunes the zGNR electronic and magnetic properties. A ferroelectric single-domain configuration with polarization up and down is considered including explicitly a bottom metallic electrode. Our results show how not only the ferroelectric polarization direction determines the doping in zGNR-the downward polarization induces a p-type doping in a planar zGNR whereas the upward polarization keeps it intrinsic-but also the features of the clean ferroelectric surface, such as the atomic relaxation and the electronic distribution. Interestingly, the surface ferroelectric polarization, besides tuning the carrier type as it does in graphene, also closes the zGNR band gap which can be understood in terms of the weakening of the local magnetic moment of the edge carbon atoms as the polarization increases. The zGNR antiferromagnetic ground state is preserved without breaking the α-β degeneracy. PMID:27603305

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

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

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

  17. Study of physical properties of integrated ferroelectric/ferromagnetic heterostructures

    SciTech Connect

    Martinez, R.; Kumar, A.; Palai, R.; Katiyar, R. S.; Scott, J. F.

    2010-06-15

    Superlattices (SLs) with different periodicity of ferromagnetic La{sub 0.7}Sr{sub 0.3}MnO{sub 3} (LSMO) and ferroelectric Ba{sub 0.7}Sr{sub 0.3}TiO{sub 3} as constitutive layers were fabricated on conducting LaNiO{sub 3} coated (001) oriented MgO substrates using pulsed laser deposition. The crystallinity, ferroelectric, and magnetic properties of the SLs were studied over a wide range of temperatures and frequencies. The structure exhibited ferromagnetic behavior at 300 K and ferroelectric behavior over a range of temperatures between 100 and 300 K. A frequency-dependent change in dielectric constant and tangent loss were observed above the ferromagnetic-paramagnetic temperature. The frequency-dependent dielectric anomalies are attributed to the change in metallic and magnetic nature of LSMO and also the interfacial effect of two different phases that are connected alternatively in series. The effect of ferromagnetic LSMO layers on ferroelectric properties of the SLs indicated strong influence of the interfaces. The asymmetric behavior of ferroelectric loop and the capacitance-voltage relationship suggest development of a built field in the SLs due to high strain across the interfaces.

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

    PubMed

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

    2015-01-01

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

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

    PubMed Central

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

    2015-01-01

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

  20. 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

    2014-01-01

    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. PMID:25399545

  1. Performing spectroscopic and specific heat studies of improper ferroelectrics

    NASA Technical Reports Server (NTRS)

    Coleman, L. B.

    1982-01-01

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

  2. Phononic Crystal Tunable via Ferroelectric Phase Transition

    NASA Astrophysics Data System (ADS)

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

    2015-09-01

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

  3. Shear mode properties of single crystal ferroelectrics

    NASA Astrophysics Data System (ADS)

    McLaughlin, E. A.; Robinson, H. C.

    2003-10-01

    Single crystal ferroelectrics or piezocrystals were recently introduced into the electroactive materials community. The 33-mode electromechanical coupling factor of piezocrystals is typically greater than 0.90, which is significantly larger than typical values for piezoelectric ceramics (0.62-0.74). For sonar projector applications this large k33 has been responsible for more than doubling the bandwidth of active sonar arrays over what is currently achievable with ceramics. Last year a crystal grower produced a cut of lead magnesium niobate-lead titanate (PMN-PT) single crystal with piezoelectric shear coefficient values of 7000 pm/V and shear coupling factors of 0.97. (For PZT5H, d15 is 730 pm/V.) This piezocrystal d15 coefficient implies significantly improved sensitivity and signal-to-noise ratio for accelerometers and hydrophones, while the high coupling promises bandwidth increases greater than those realized in 33-mode projectors using piezocrystals. This research studies the shear-mode behavior of PMN-PT piezocrystals for use in sensors and projectors. By measuring the response of the materials to high and low level electrical bias and excitation fields, frequency, and temperature, the materials' effective material properties as a function of these operational variables were determined. [Work sponsored by ONR and NUWC ILIR.

  4. Charge ordering and ferroelectricity in magnetite

    NASA Astrophysics Data System (ADS)

    Khomskii, Daniel

    2007-03-01

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

  5. Photostriction in Ferroelectrics from Density Functional Theory

    NASA Astrophysics Data System (ADS)

    Paillard, Charles; Xu, Bin; Dkhil, Brahim; Geneste, Grégory; Bellaiche, L.

    2016-06-01

    An ab initio procedure allowing the computation of the deformation of ferroelectric-based materials under light is presented. This numerical scheme consists in structurally relaxing the system under the constraint of a fixed ne concentration of electrons photoexcited into a specific conduction band edge state from a chosen valence band state, via the use of a constrained density functional theory method. The resulting change in lattice constant along a selected crystallographic direction is then calculated for a reasonable estimate of ne. This method is applied to bulk multiferroic BiFeO3 and predicts a photostriction effect of the same order of magnitude than the ones recently observed. A strong dependence of photostrictive response on both the reached conduction state and the crystallographic direction (along which this effect is determined) is also revealed. Furthermore, analysis of the results demonstrates that the photostriction mechanism mostly originates from the screening of the spontaneous polarization by the photoexcited electrons in combination with the inverse piezoelectric effect.

  6. Photostriction in Ferroelectrics from Density Functional Theory.

    PubMed

    Paillard, Charles; Xu, Bin; Dkhil, Brahim; Geneste, Grégory; Bellaiche, L

    2016-06-17

    An ab initio procedure allowing the computation of the deformation of ferroelectric-based materials under light is presented. This numerical scheme consists in structurally relaxing the system under the constraint of a fixed n_{e} concentration of electrons photoexcited into a specific conduction band edge state from a chosen valence band state, via the use of a constrained density functional theory method. The resulting change in lattice constant along a selected crystallographic direction is then calculated for a reasonable estimate of n_{e}. This method is applied to bulk multiferroic BiFeO_{3} and predicts a photostriction effect of the same order of magnitude than the ones recently observed. A strong dependence of photostrictive response on both the reached conduction state and the crystallographic direction (along which this effect is determined) is also revealed. Furthermore, analysis of the results demonstrates that the photostriction mechanism mostly originates from the screening of the spontaneous polarization by the photoexcited electrons in combination with the inverse piezoelectric effect. PMID:27367406

  7. New Low-Loss Ferroelectric Materials for Accelerator Applications

    NASA Astrophysics Data System (ADS)

    Kanareykin, A.; Nenasheva, E.; Karmanenko, S.; Yakovlev, V.

    2004-12-01

    We present results on a new ferroelectric material based on bulk low-loss BST (Barium-Strontium Titanium oxides) compounds especially developed for accelerator applications. We have demonstrated suitable nonlinear dielectric properties of this material that make it useful for switching and tuning RF accelerator components. The material exhibits a dielectric constant of 400-500 and tunability factor of 1.2. The best sample of those studied demonstrated a loss factor <4×10-3 at 35 GHz. Ferroelectric rings and substrates are key components required for electrically controlled switches and phase shifters for active pulse compressors for future linear colliders. A thin ferroelectric layer incorporated into a dielectric loaded accelerating structure allows compensation of any frequency shift caused by ceramic waveguide machining tolerances and dielectric constant heterogeneity. A tuning range of 1.1% has been demonstrated for an X-Band (11-13 GHz) dielectric accelerating structure.

  8. Polarization control at spin-driven ferroelectric domain walls

    NASA Astrophysics Data System (ADS)

    Leo, Naëmi; Bergman, Anders; Cano, Andres; Poudel, Narayan; Lorenz, Bernd; Fiebig, Manfred; Meier, Dennis

    2015-04-01

    Unusual electronic states arise at ferroelectric domain walls due to the local symmetry reduction, strain gradients and electrostatics. This particularly applies to improper ferroelectrics, where the polarization is induced by a structural or magnetic order parameter. Because of the subordinate nature of the polarization, the rigid mechanical and electrostatic boundary conditions that constrain domain walls in proper ferroics are lifted. Here we show that spin-driven ferroelectricity promotes the emergence of charged domain walls. This provides new degrees of flexibility for controlling domain-wall charges in a deterministic and reversible process. We create and position a domain wall by an electric field in Mn0.95Co0.05WO4. With a magnetic field we then rotate the polarization and convert neutral into charged domain walls, while its magnetic properties peg the wall to its location. Using atomistic Landau-Lifshitz-Gilbert simulations we quantify the polarization changes across the two wall types and highlight their general occurrence.

  9. Structural, magnetic and electrical properties of ferromagnetic/ferroelectric multilayers

    SciTech Connect

    Sirena, M.; Kaul, E.; Guimpel, J.; Steren, L. B.; Pedreros, M. B.; Rodriguez, C. A.

    2011-06-15

    The La{sub 0.75}Sr{sub 0.25}MnO{sub 3} (LSMO)/Ba{sub 0.7}Sr{sub 0.3}TiO{sub 3} (BSTO) superlattices and bilayers, where LSMO is ferromagnetic and BSTO is ferroelectric, were grown by dc sputtering. X-ray diffraction indicates that the samples present a textured growth with the c axis perpendicular to the substrate. Magnetization measurements show a decrease of the sample's magnetization for decreasing ferromagnetic thickness. This effect could be related to the presence of biaxial strain and a magnetic dead layer in the samples. Conductive atomic force microscopy indicates that the samples present a total covering of the ferromagnetic layer for a ferroelectric thickness higher than four unit cells. Transport tunneling of the carriers seems to be the preferred conduction mechanism through the ferroelectric layer. These are promising results for the development of multiferroic tunnel junctions.

  10. Is hexagonal InMnO3 ferroelectric?

    NASA Astrophysics Data System (ADS)

    Huang, Fei-Ting; Horibe, Yoichi; Wang, Xueyun; Cheong, Sang-Wook; Mori, Shigeo

    2013-03-01

    Hexagonal manganite (h-REMnO3; RE=rare earths) shows a unique improper ferroelectricity, accompanying a structural trimerization. RE can be replaced by In, which is much smaller than any RE ions. Recently, Oak et al. suggested InMnO3 is ferroelectric from the results of first-principles calculations, while Kumagai et al. proposed a non-ferroelectric ground state. In this talk, we will report the results of our investigation on the structural domains and local structural distortions of InMnO3 using dark-field transmission electron microscopy. We demonstrate that InMnO3 shows a distinct √{ 3} ×√{ 3} -type superstructure from the high-temperature paraelectric phase (P63/mmc), and the domain structure can be delicately controlled by varying the synthesis and annealing conditions. The correlation between physical properties and local structural distortions in the InMnO3 will be discussed in detail.

  11. A transverse electric current in triglycine sulphate ferroelectric crystal

    NASA Astrophysics Data System (ADS)

    Fugiel, Bogusław; Kikuta, Toshio

    2016-05-01

    The application of a prolonged transverse electric field at a temperature TA < TC leads to unexpected qualitative changes in dielectric and thermal properties of the uniaxial ferroelectric triglycine sulphate (TGS) crystal, where TC is the critical temperature of the paraelectric-ferroelectric phase transition. The new properties can be still observed even after the transverse field has ceased to be applied as long as the temperature of the sample does not exceed TA. However, annealing the sample above TC leads to the restoration of the original state of the crystal. An electric current flowing along the direction perpendicular to the polar axis of the uniaxial TGS ferroelectric crystal was measured below the temperature TA at which the prolonged transverse electric field had been formerly applied to the crystal for a few hours. The experimental data resemble the classic pyroelectric current flowing along the polar axis.

  12. Piezoelectric properties of rhombohedral ferroelectric materials with phase transition

    NASA Astrophysics Data System (ADS)

    Zhao, Xiaofang; Soh, A. K.

    2015-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

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

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

    PubMed Central

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

    2015-01-01

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

  15. Controlling the spin-torque efficiency with ferroelectric barriers

    NASA Astrophysics Data System (ADS)

    Useinov, A.; Chshiev, M.; Manchon, A.

    2015-02-01

    Nonequilibrium spin-dependent transport in magnetic tunnel junctions comprising a ferroelectric barrier is theoretically investigated. The exact solutions of the free electron Schrödinger equation for electron tunneling in the presence of interfacial screening are obtained by combining Bessel and Airy functions. We demonstrate that the spin transfer torque efficiency, and more generally the bias dependence of tunneling magneto- and electroresistance, can be controlled by switching the ferroelectric polarization of the barrier. In particular, the critical voltage at which the in-plane torque changes sign can be strongly enhanced or reduced depending on the direction of the ferroelectric polarization of the barrier. This effect provides a supplementary way to electrically control the current-driven dynamic states of the magnetization and related magnetic noise in spin transfer devices.

  16. Polarization-Strain Coupling in Mesoscopic Mixed Ferroelectrics

    NASA Astrophysics Data System (ADS)

    Pattnaik, Radha; Toulouse, Jean

    1998-03-01

    A new type of dielectric resonance has been observed in several mixed ferroelectrics, KTa(_1-x)Nb(_x)O(_3) (KTN), K(_1-x)Li(_x)TaO(_3) (KLT) and PbMg(_1/3)Nb(_2/3)O(_3) (PMN), also known as Relaxor Ferroelectrics. This resonance and its metastability (persistance over long periods of time) in the paraelectric phase of KTN provides clear evidence for the presence, in relaxors, of permenent polar nanoregions and of a strong polarization-strain coupling. The frequencies calculated from the elastic constant or modulus reveal the unexpected nature of the resonance. A comparative study of the polarization-strain coupling and dielectric relaxation in KTN and KLT is presented. These results provide the necessary elements for a microscopic description of the Relaxor behavior in disordered ferroelectrics.

  17. Ferroelectric polarization in nanocrystalline hydroxyapatite thin films on silicon.

    PubMed

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

    2013-01-01

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

  18. Fast Ferroelectric L-Band Tuner for Superconducting Cavities

    SciTech Connect

    Jay L. Hirshfield

    2011-03-01

    Analysis and modeling is presented for a fast microwave tuner to operate at 700 MHz which incorporates ferroelectric elements whose dielectric permittivity can be rapidly altered by application of an external voltage. This tuner could be used to correct unavoidable fluctuations in the resonant frequency of superconducting cavities in accelerator structures, thereby greatly reducing the RF power needed to drive the cavities. A planar test version of the tuner has been tested at low levels of RF power, but at 1300 MHz to minimize the physical size of the test structure. This test version comprises one-third of the final version. The tests show performance in good agreement with simulations, but with losses in the ferroelectric elements that are too large for practical use, and with issues in bonding of ferroelectric elements to the metal walls of the tuner structure.

  19. Development of a Ferroelectric Based Tunable DLA Structure

    SciTech Connect

    Kanareykin, A.; Schoessow, P.; Jing, C.; Nenasheva, E.; Power, J. G.; Gai, W.

    2009-01-22

    An experimental demonstration of a tunable Dielectric Loaded Accelerating (DLA)[1] structure is planned using a nonlinear ferroelectric with temperature- or voltage-controllable permittivity. We designed and tested two prototype Ka-band double layer ferroelectric-ceramic structures (cylindrical and planar) consisting of linear ceramic layers (dielectric constant of 6.8) and BST(M) composite ferroelectric layers of 400-800 {mu}m thickness and dielectric constant of 450-550. The frequency shift by temperature variation of the cylindrical Ka-band tunable DLA of 14 MHz/ deg. K has been demonstrated leading to an overall DLA structure frequency tuning range of 140-280 MHz with 10-20 deg. K temperature variation. The Ka band prototype DLA structure demonstrated a 6 MHz frequency tuning range for a dc bias field design at 25 kV/cm field strength.

  20. Enhancing piezoelectricity through polarization-strain coupling in ferroelectric superlattices

    SciTech Connect

    Cooper, Valentino R; Rabe, Karin M.

    2009-01-01

    Short period ferroelectric/ferroelectric BaTiO3 (BTO)/PbTiO3 (PTO) superlattices are studied using density functional theory. Contrary to the trends in paraelectric/ferroelectric superlattices the polarization remains nearly constant for PTO concentrations below 50%. In addition, a significant decrease in the c/a ratio below the PTO values were observed. Using a superlattice effective Hamiltonian we predict an enhancement in the d33 piezoelectric coefficient peaking at ~75% PTO concentration due to the different polarization-strain coupling in PTO and BTO layers. Further analysis reveals that these trends are bulk properties which are a consequence of the reduced P brought about by the polarization saturation in the BTO layers.

  1. Ferroelectric Polarization in Nanocrystalline Hydroxyapatite Thin Films on Silicon

    NASA Astrophysics Data System (ADS)

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

    2013-07-01

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

  2. Auxetic behavior under electrical loads in an induced ferroelectric phase

    NASA Astrophysics Data System (ADS)

    Tan, X.; Jo, W.; Granzow, T.; Frederick, J.; Aulbach, E.; Rödel, J.

    2009-01-01

    The longitudinal and transverse strains were measured as a function of applied electric fields in a bulk ceramic sample of Pb0.99Nb0.02[(Zr0.57Sn0.43)0.94Ti0.06]0.98O3 at room temperature. Instead of a transverse contraction, a transverse expansion was observed in the electric-field-induced ferroelectric phase after the antiferroelectric-to-ferroelectric phase transition. Therefore, an auxetic behavior was established in monolithic ferroelectric polycrystalline ceramics under electrical loads. The behavior is characterized by a negative strain ratio that is analogous to the Poisson's ratio. The transverse expansion leads to a large hydrostatic piezoelectric coefficient dh, which suggests new applications of antiferroelectric ceramics in piezoelectric devices.

  3. Ferroelectric Polarization in Nanocrystalline Hydroxyapatite Thin Films on Silicon

    PubMed Central

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

    2013-01-01

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

  4. Photonic Heterostructures with Properties of Ferroelectrics and Light Polarizers

    SciTech Connect

    Palto, S. P. Draginda, Yu. A.

    2010-11-15

    The optical and electro-optical properties of a new type of photonic heterostructure composed of alternating ferroelectric molecular layers and optically anisotropic layers of another material are considered. A numerical simulation of the real prototype of this heterostructure, which can be prepared by the Langmuir-Blodgett method from layers of a ferroelectric copolymer (polyvinylidene fluoride trifluoroethylene) and an azo dye with photoinduced optical anisotropy, has been performed. It is shown that this heterostructure has pronounced polarization optical properties and yields a significant change in the polarization state of light at the photonic band edges in the ranges of the maximum density of photon states. The latter property can be used to obtain an enhanced electro-optic effect at small spectral shifts of the photonic band (the latter can be provided by the piezoelectric effect in ferroelectric layers).

  5. Ferroelectric capped magnetization in multiferroic PZT/LSMO tunnel junctions

    SciTech Connect

    Kumar, Ashok Shukla, A. K.; Barrionuevo, D.; Ortega, N.; Katiyar, Ram S.; Shannigrahi, Santiranjan; Scott, J. F.

    2015-03-30

    Self-poled ultra-thin ferroelectric PbZr{sub 0.52}Ti{sub 0.48}O{sub 3} (PZT) (5 and 7 nm) films have been grown by pulsed laser deposition technique on ferromagnetic La{sub 0.67}Sr{sub 0.33}MnO{sub 3} (LSMO) (30 nm) to check the effect of polar capping on magnetization for ferroelectric tunnel junction devices. PZT/LSMO heterostructures with thick polar PZT (7 nm) capping show nearly 100% enhancement in magnetization compared with thin polar PZT (5 nm) films, probably due to excess hole transfer from the ferroelectric to the ferromagnetic layers. Core-level x-ray photoelectron spectroscopy studies revealed the presence of larger Mn 3s exchange splitting and higher Mn{sup 3+}/Mn{sup 4+} ion ratio in the LSMO with 7 nm polar capping.

  6. Proposal for ultrafast switching of ferroelectrics using midinfrared pulses

    NASA Astrophysics Data System (ADS)

    Subedi, Alaska

    2015-12-01

    I propose a method for ultrafast switching of ferroelectric polarization using midinfrared pulses. This involves selectively exciting the highest frequency A1 phonon mode of a ferroelectric material with an intense midinfrared pulse. Large amplitude oscillations of this mode provides a unidirectional force to the lattice such that it displaces along the lowest frequency A1 phonon mode coordinate because of a nonlinear coupling of the type g QPQIR2 between the two modes. First-principles calculations show that this coupling is large in perovskite transition-metal oxide ferroelectrics, and the sign of the coupling is such that the lattice displaces in the switching direction. Furthermore, I find that the lowest frequency A1 mode has a large QP3 order anharmonicity, which causes a discontinuous switch of electric polarization as the pump amplitude is continuously increased.

  7. Design of a polarimeter with two ferroelectric liquid crystal panels

    NASA Astrophysics Data System (ADS)

    Peinado, Alba; Lizana, Angel; Campos, Juan

    2013-09-01

    We present a Stokes polarimeter based on two ferroelectric liquid crystal monopixel panels. This architecture presents advantages associated to dynamic polarimeters and also, allows very fast polarization measurements. A ferroelectric liquid crystal panel can be modeled as a waveplate with a constant retardance and, with two possible orientations for its fast axis when a bipolar electrical sign is addressed. We have calibrated the optical features of our ferroelectric liquid crystal panels: retardance and rotation of the optical axis. In addition, we have carried out an optimization of the orientation of these panels in the setup in order to obtain a minimum condition number of our polarimeter and so, minimize the propagation of noise. Afterwards, we have conducted a tolerance analysis of the elements involved in the setup, focusing for a 2% of accuracy in the Stokes vectors measurements. Then, an experimental calibration is carried out and several measurements are taken in order to analyze its performance.

  8. Integration of Ferroelectrics, Ferromagnets, and Multiferroics with Silicon

    NASA Astrophysics Data System (ADS)

    Schlom, Darrell

    2009-03-01

    In this talk I will describe the epitaxial integration of ferroelectrics, ferromagnets, and materials that are both at the same time, with silicon. Until recently, ``oxide'' could only mean one thing to anyone working in the semiconductor industry---SiO2. But oxides are an exciting class of electronic materials in their own right. Oxides exhibit the full spectrum of electronic, optical, and magnetic behavior including many functionalities not found in conventional semiconductors. Further, such oxides can be combined epitaxially not only with each other, but epitaxially with the workhorse of semiconductor technology, silicon, enabling the unparalleled variety of physical properties of oxides to be exploited in new ways for electronic applications. The specific oxides that my collaborators* and I have integrated epitaxially with silicon include EuO, ZnO, CaTiO3, SrTiO3, BaTiO3, BiFeO3, Pb(Zr,Ti)O3, and PbMg1/3Nb2/3O3-PbTiO3. Highlights from these systems will be presented. * The work reported was performed in collaboration with the groups of Jochen Mannhart (U. Augsburg), Chang-Beom Eom (U. Wisconsin-Madison), Ramamoorthy Ramesh (Berkeley), Jeremy Levy (U. Pittsburgh), David Muller (Cornell), Xiaoqing Pan (U. Michigan), J"urgen Schubert (J"ulich), Long-Qing Chen (Penn State), Susan Trolier-McKinstry (Penn State), Yves Idzerda (Montana State), Peter B"oni (TU M"unchen), Joseph Woicik (NIST), Philip Ryan (Ames), Michael Bedzyk (Northwestern), Yuri Barash (Russian Acad. Sci.), Qing Ma (Intel), and Hao Li (Motorola).

  9. Dynamic Properties of Dielectric Susceptibility in Ferroelectric Thin Films

    NASA Astrophysics Data System (ADS)

    Cui, Lian; Cui, Haiying; Wu, Chunmei; Yang, Guihua; He, Zelong; Wang, Yuling; Che, Jixin

    2016-02-01

    In this paper, frequency, temperature, film thickness, surface effects, and various parameters dependence of dielectric susceptibility is investigated theoretically for ferroelectric thin films by the modified Landau theory under an AC applied field. The dielectric susceptibility versus AC applied field shows butterfly-shaped behavior, and depends strongly on the frequency and amplitude of the field and temperature. Our study shows that the existence of the surface transition layer can depress the dielectric susceptibility of a ferroelectric thin film. These results are well consistent with the phenomena reported in experiments.

  10. Response of TGS ferroelectric samples to rapid temperature impulses

    NASA Astrophysics Data System (ADS)

    Trybus, M.; Proszak, W.; Woś, B.

    2013-11-01

    Tryglicine sulphate (TGS) is one of the most extensively studied ferroelectric materials, which undergoes second order phase transition and shows the pyroelectric effect. In our present experiments we study the electric properties of TGS, in relation to domain switching, observing the samples' response to controlled temperature pulses. The charge released in the processes of domain switching was previously studied under constant temperature growth. Our method allows us to observe the released pyroelectric charge in both the ferroelectric and paraelectric phases. To perform our experiment we designed new measurement software and constructed a novel thermostatic sample holder containing Peltier's cells as heating/cooling elements.

  11. Temperature dependence of electronic transport property in ferroelectric polymer films

    NASA Astrophysics Data System (ADS)

    Zhao, X. L.; Wang, J. L.; Tian, B. B.; Liu, B. L.; Zou, Y. H.; Wang, X. D.; Sun, S.; Sun, J. L.; Meng, X. J.; Chu, J. H.

    2014-10-01

    The leakage current mechanism of ferroelectric copolymer of polyvinylidene fluoride with trifluoroethylene prepared by Langmuir-Blodgett was investigated in the temperature range from 100 K to 350 K. The electron as the dominant injected carrier was observed in the ferroelectric copolymer films. The transport mechanisms in copolymer strongly depend on the temperature and applied voltage. From 100 K to 200 K, Schottky emission dominates the conduction. With temperature increasing, the Frenkel-Poole emission instead of the Schottky emission to conduct the carrier transport. When the temperature gets to 260 K, the leakage current becomes independent of temperature, and the space charge limited current conduction was observed.

  12. Characterization of a Common-Source Amplifier Using Ferroelectric Transistors

    NASA Technical Reports Server (NTRS)

    Hunt, Mitchell; Sayyah, Rana; MacLeond, Todd C.; Ho, Pat D.

    2010-01-01

    This paper presents empirical data that was collected through experiments using a FeFET in the established common-source amplifier circuit. The unique behavior of the FeFET lends itself to interesting and useful operation in this widely used common-source amplifier. The paper examines the effect of using a ferroelectric transistor for the amplifier. It also examines the effects of varying load resistance, biasing, and input voltages on the output signal and gives several examples of the output of the amplifier for a given input. The difference between a commonsource amplifier using a ferroelectric transistor and that using a MOSFET is addressed.

  13. Ferroelectric-semiconductor photovoltaics: Non-PN junction solar cells

    NASA Astrophysics Data System (ADS)

    Liu, Fude; Wang, Wentao; Wang, Lei; Yang, Guandong

    2014-03-01

    Traditional positive-negative (PN) junction based solar cells have many limitations. Herein, we introduce ferroelectric-semiconductor solar cells that use the bound surface charges of the ferroelectric for achieving charge separation in the semiconductor. The feasibility of the new concept cells was verified both experimentally and theoretically in detail. The new cells are unique in that free charge carriers and fixed charge carriers are physically separated from each other. The feature allows us to go beyond traditional junction-based structures and have more freedom in material selection, device design, and fabrication.

  14. Engineering ferroelectric tunnel junctions through potential profile shaping

    SciTech Connect

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

    2015-06-01

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

  15. Voltage tunability of thermal conductivity in ferroelectric materials

    DOEpatents

    Ihlefeld, Jon; Hopkins, Patrick Edward

    2016-02-09

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

  16. Ferroelectric Smectic Phase Formed by Achiral Straight Core Mesogens

    NASA Astrophysics Data System (ADS)

    Stannarius, Ralf; Li, Jianjun; Weissflog, Wolfgang

    2003-01-01

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

  17. Enhanced flexoelectricity through residual ferroelectricity in barium strontium titanate

    SciTech Connect

    Garten, Lauren M. Trolier-McKinstry, Susan

    2015-03-07

    Residual ferroelectricity is observed in barium strontium titanate ceramics over 30 °C above the global phase transition temperature, in the same temperature range in which anomalously large flexoelectric coefficients are reported. The application of a strain gradient leads to strain gradient-induced poling or flexoelectric poling. This was observed by the development of a remanent polarization in flexoelectric measurements, an induced d{sub 33} piezoelectric response even after the strain gradient was removed, and the production of an internal bias of 9 kV m{sup −1}. It is concluded that residual ferroelectric response considerably enhances the observed flexoelectric response.

  18. Ferroelectric control of anisotropic damping in multiferroic tunnel junctions

    NASA Astrophysics Data System (ADS)

    Wang, Yan; Zhang, Ning; Berakdar, Jamal; Jia, Chenglong

    2015-10-01

    The magnetoelectric effect on nonlocal magnetization dynamics is theoretically investigated in normal-metal/ferroelectric-insulator/ferromagnetic tunnel junctions. In addition to the Rashba spin-orbit interaction (SOI) originating from loss of parity symmetry at the interfaces, the topology of interfacial spiral spins triggered by ferroelectric polarization acts with an effective SOI that is electrically controllable. These spin-dependent interactions result in an anisotropic Gilbert damping with C2 v symmetry. The findings are of a direct relevance for the utilization of composite multiferroics for devices that rely on electrically controlled magnetic switching.

  19. Some strategies for improving caloric responses with ferroelectrics

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

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

  20. 2015 Edition Health Information Technology (Health IT) Certification Criteria, 2015 Edition Base Electronic Health Record (EHR) Definition, and ONC Health IT Certification Program Modifications. Final rule.

    PubMed

    2015-10-16

    This final rule finalizes a new edition of certification criteria (the 2015 Edition health IT certification criteria or "2015 Edition'') and a new 2015 Edition Base Electronic Health Record (EHR) definition, while also modifying the ONC Health IT Certification Program to make it open and accessible to more types of health IT and health IT that supports various care and practice settings. The 2015 Edition establishes the capabilities and specifies the related standards and implementation specifications that Certified Electronic Health Record Technology (CEHRT) would need to include to, at a minimum, support the achievement of meaningful use by eligible professionals (EPs), eligible hospitals, and critical access hospitals (CAHs) under the Medicare and Medicaid EHR Incentive Programs (EHR Incentive Programs) when such edition is required for use under these programs. PMID:26477063

  1. The Existence of Ferroelectric Ice on Icy Bodies in Space: a Neutron Diffraction Study

    NASA Astrophysics Data System (ADS)

    Fukazawa, Hiroshi

    The complex behavior of water and the unusual properties of ferroelectric ice XI continue to attract much interest. Whether ice in the space exists as ice XI, is an important question, because long range electrostatic forces caused by the ferroelectricity might be an important factor for planet formation. From neutron diffraction experiments, we found the temperature and pressure conditions for the transformation of the largest fraction of ice into ferroelectric ice. It suggests that myriad big icy-bodies, which exist as dwarf planets and Kuiper Belt Object, consist of thick ferroelectric-ice surface. Furthermore, we report spectral and vibrational properties of ferroelectric ice investigated by inelastic neutron scattering and infrared absorption measurements. Because the spectral properties of ferroelectric ice are clearly different from those of ordinary ice, the distinct ferroelectric ice in the universe is detectable using infrared telescopes and planetary exploration.

  2. Strains and polarization developed during electric field-induced antiferroelectric to ferroelectric phase transformations in lead zirconate-based ceramics

    NASA Astrophysics Data System (ADS)

    Frederick, Joshua

    Widespread adoption of renewable energy sources, such as wind and solar power, will necessitate an efficient way to interface with energy storage devices in order to ensure around-the-clock energy delivery during off-peak hours. Energy storage devices implementing linear dielectric capacitors offer exceptional power density (i.e. rate of charge/discharge), but cannot match the energy density (i.e. storage capacity) of batteries. However, replacing the linear dielectric in capacitors with an antiferroelectric material has the potential to increase the energy density by approximately one order of magnitude. Since the energy is stored via a reversible and diffusionless antiferroelectric-to-ferroelectric phase transformation, the high power density is maintained. In this study, the response of antiferroelectric Pb0.99Nb 0.02[(Zr0.57Sn0.43)1-yTi y]0.98O3 ceramics with compositions near an antiferroelectric/ferroelectric phase boundary were systemically characterized in the presence of electric fields. By altering the titanium content ( y in the chemical formula) the phase boundary was incrementally approached, allowing for detailed study of the electric field-induced phase transformation in this region of structural instability. The key parameters of polarization, longitudinal strain, and transverse strain were simultaneously recorded as a function of externally applied electric fields on all compositions. It was found that the volume expansion and polarization developed during the antiferroelectric-to-ferroelectric phase transformation remained ~0.4% and ~30 muC/cm2, respectively, regardless of the composition in the range of 0.060 ≤ y ≤ 0.075. However, the critical field strengths associated with the phase transformation varied in a linear fashion with y, supporting the suggestion that increasing the titanium content strengthens the ferroelectric ordering of the system. Application of axial and radial compressive pre-stresses to samples with composition y = 0

  3. Ab initio study on ferroelectric instability induced by relativistic effects in PbTe

    NASA Astrophysics Data System (ADS)

    Kim, Jinwoong; Jhi, Seung-Hoon

    2014-03-01

    A recent study [E. S. Bozin et al., Science 330, 1660 (2010)] reported unusual ferroelectric instability in lead chalcogenides at heating, which is contrast to typical ferroelectric transitions that occur at cooling. This study explains the emergence of local dipole formation due to the softening of transverse optical (TO) phonon modes. However, standard first-principles calculations do not support the phonon softening (imaginary frequency). Here, we present that the spin-orbit interaction should be included in the calculations to correctly produce the instability and that, as such, thermal expansion leads to the softening in TO phonon modes. Another controversial finding in experiment that the frequency of TO mode is finite and increases with temperatures can be explained if anharmonic effects are considered together with the spin-orbit interaction. Our study shows that the spin-orbit interaction can be critical for the structural stability and thus affect the thermoelectric or structural phase transition. This work was supported by the Supercomputing Center/Korea Institute of Science and Technology Information with supercomputing resources including technical support (KSC-2012-C2-68).

  4. Effect of ferroelectric layer on the magnetic properties of ferromagnetic layer

    NASA Astrophysics Data System (ADS)

    Singamaneni, Srinivasa Rao; Prater, John T.; Narayan, Jay

    2015-03-01

    In this presentation, we show the integration of classical two-phase multiferroic heterostructures composed of room-temperature ferroelectric BaTiO3 (BTO) and ferromagnetic La0.7Sr0.3MnO3 (LSMO) epitaxial thin films grown on technologically important substrate Si (100). Bilayers of BTO/LSMO thin films display ferromagnetic Curie transition temperatures of ~350 K, close to the bulk value, that are independent of BTO films thickness in the range of 25-100 nm. Discontinuous magnetization jumps associated with BTO structural transitions were suppressed in M(T) curves, probably due to substrate clamping effect. Interestingly, at cryogenic temperatures, the BTO/LSMO structure with BTO layer thickness of 100nm shows almost 2-times higher magnetic coercive field, 3-times reduction in saturation magnetization and improved squareness compared to the sample without BTO. We attribute that to the strong in-plane spin pinning of the ferromagnetic layer induced by BTO layer at BTO/LSMO interface. This work demonstrates that it is possible to manipulate the magnetic properties of ferromagnetic layer by varying the thickness of ferroelectric layer, without applying external electric field.

  5. Evaluation of Data Retention Characteristics for Ferroelectric Random Access Memories (FRAMs)

    NASA Technical Reports Server (NTRS)

    Sharma, Ashok K.; Teverovsky, Alexander

    2001-01-01

    Data retention and fatigue characteristics of 64 Kb lead zirconate titanate (PZT)-based Ferroelectric Random Access Memories (FRAMs) microcircuits manufactured by Ramtron were examined over temperature range from -85 C to +310 C for ceramic packaged parts and from -85 C to +175 C for plastic parts, during retention periods up to several thousand hours. Intrinsic failures, which were caused by a thermal degradation of the ferroelectric cells, occurred in ceramic parts after tens or hundreds hours of aging at temperatures above 200 C. The activation energy of the retention test failures was 1.05 eV and the extrapolated mean-time-to-failure (MTTF) at room temperature was estimated to be more than 280 years. Multiple write-read cycling (up to 3x10(exp 7)) during the fatigue testing of plastic and ceramic parts did not result in any parametric or functional failures. However, operational currents linearly decreased with the logarithm of number of cycles thus indicating fatigue process in PZT films. Plastic parts, that had more recent date code as compared to ceramic parts, appeared to be using die with improved process technology and showed significantly smaller changes in operational currents and data access times.

  6. Negative Capacitance in Organic/Ferroelectric Capacitor to Implement Steep Switching MOS Devices.

    PubMed

    Jo, Jaesung; Choi, Woo Young; Park, Jung-Dong; Shim, Jae Won; Yu, Hyun-Yong; Shin, Changhwan

    2015-07-01

    Because of the "Boltzmann tyranny" (i.e., the nonscalability of thermal voltage), a certain minimum gate voltage in metal-oxide-semiconductor (MOS) devices is required for a 10-fold increase in drain-to-source current. The subthreshold slope (SS) in MOS devices is, at best, 60 mV/decade at 300 K. Negative capacitance in organic/ferroelectric materials is proposed in order to address this physical limitation in MOS technology. Here, we experimentally demonstrate the steep switching behavior of a MOS device-that is, SS ∼ 18 mV/decade (much less than 60 mV/decade) at 300 K-by taking advantage of negative capacitance in a MOS gate stack. This negative capacitance, originating from the dynamics of the stored energy in a phase transition of a ferroelectric material, can achieve the step-up conversion of internal voltage (i.e., internal voltage amplification in a MOS device). With the aid of a series-connected negative capacitor as an assistive device, the surface potential in the MOS device becomes higher than the applied gate voltage, so that a SS of 18 mV/decade at 300 K is reliably observed. PMID:26103511

  7. 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.

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

    SciTech Connect

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

    2015-03-02

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

  9. [Local communalization of clinical records between the municipal community hospital and local medical institutes by using information technology].

    PubMed

    Iijima, Shohei; Shinoki, Keiji; Ibata, Takeshi; Nakashita, Chisako; Doi, Seiko; Hidaka, Kumi; Hata, Akiko; Matsuoka, Mio; Waguchi, Hideko; Mito, Saori; Komuro, Ryutaro

    2012-12-01

    We introduced the electronic health record system in 2002. We produced a community medical network system to consolidate all medical treatment information from the local institute in 2010. Here, we report on the present status of this system that has been in use for the previous 2 years. We obtained a private server, set up a virtual private network(VPN)in our hospital, and installed dedicated terminals to issue an electronic certificate in 50 local institutions. The local institute applies for patient agreement in the community hospital(hospital designation style). They are then entitled to access the information of the designated patient via this local network server for one year. They can access each original medical record, sorted on the basis of the medical attendant and the chief physician; a summary of hospital stay; records of medication prescription; and the results of clinical examinations. Currently, there are approximately 80 new registrations and accesses per month. Information is provided in real time allowing up to date information, helping prescribe the medical treatment at the local institute. However, this information sharing system is read-only, and there is no cooperative clinical pass system. Therefore, this system has a limit to meet the demand for cooperation with the local clinics. PMID:23268886

  10. Technology versus humanism: how patients perceive the use of electronic health records in physicians' offices--a qualitative study.

    PubMed

    Mwachofi, Ari K; Khaliq, Amir A; Carrillo, Estevan R; Winfree, William

    2016-01-01

    Electronic Health Records (EHRs) have the potential to improve the quality of care. In view of the accelerated adoption of EHRs, there is a need to understand conditions necessary for their effective use. Patients are the focus of healthcare and their perceptions and expectations need to be included in developing and implementing EHRs. The purpose of this study was to gather exploratory qualitative information from patients about their experiences and perceptions regarding the effects of EHRs on healthcare quality in physicians' offices. We conducted five focus groups with patients representing a random mix of diverse socio-demographic backgrounds in Oklahoma. Related to EHRs, patients reported improvements on the technical side of care but no change on the human side. They expressed concerns about the potential for breach of confidentiality and security of medical records. They were also concerned about the possibility of governmental agencies or insurance companies having unauthorized access to patient records. Patients differentiated between the human and technical sides of care and reported no change or improvement in the doctor-patient interaction. Patients have an important perspective on the use of EHRs and their perceptions and experiences should be considered in the development, adoption and implementation of EHRs. Otherwise, the use of EHRs may not be fully effective. There is also a need to educate patients about the potential benefits and risks of EHRs and the steps being taken to mitigate such risks. PMID:26305852

  11. New Techniques in Characterization of Ferroelectric Materials

    NASA Technical Reports Server (NTRS)

    Sehirlioglu, Alp

    2008-01-01

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

  12. Ferroelectricity in d0 double perovskite fluoroscandates

    NASA Astrophysics Data System (ADS)

    Charles, Nenian; Rondinelli, James M.

    2015-08-01

    Ferroelectricity in strain-free and strained double perovskite fluorides, Na3ScF6 and K2NaScF6 , is investigated using first-principles density functional theory. Although the experimental room temperature crystal structures of these fluoroscandates are centrosymmetric, i.e., Na3ScF6 (P 21/n ) and K2NaScF6 (F m 3 ¯m ), lattice dynamical calculations reveal that soft polar instabilities exist in each prototypical cubic phase and that the modes harden as the tolerance factor approaches unity. Thus the double fluoroperovskites bear some similarities to A B O3 perovskite oxides; however, in contrast, these fluorides exhibit large acentric displacements of alkali metal cations (Na, K) rather than polar displacements of the transition metal cations. Biaxial strain investigations of the centrosymmetric and polar Na3ScF6 and K2NaScF6 phases reveal that the paraelectric structures are favored under compressive strain, whereas polar structures with in-plane electric polarizations (˜5 -18 μ C cm-2 ) are realized at sufficiently large tensile strains. The electric polarization and stability of the polar structures for both chemistries are found to be further enhanced and stabilized by a coexisting single octahedral tilt system. Our results suggest that polar double perovskite fluorides may be realized by suppression of octahedral rotations about more than one Cartesian axis; structures exhibiting in- or out-of-phase octahedral rotations about the c axis are more susceptible to polar symmetries.

  13. Multifunctional BiFeO3/TiO2 nano-heterostructure: Photo-ferroelectricity, rectifying transport, and nonvolatile resistive switching property

    NASA Astrophysics Data System (ADS)

    Sarkar, Ayan; Khan, Gobinda Gopal; Chaudhuri, Arka; Das, Avishek; Mandal, Kalyan

    2016-01-01

    Multifunctional BiFeO3 nanostructure anchored TiO2 nanotubes are fabricated by coupling wet chemical and electrochemical routes. BiFeO3/TiO2 nano-heterostructure exhibits white-light-induced ferroelectricity at room temperature. Studies reveal that the photogenerated electrons trapped at the domain/grain boundaries tune the ferroelectric polarization in BiFeO3 nanostructures. The photon controlled saturation and remnant polarization opens up the possibility to design ferroelectric devices based on BiFeO3. The nano-heterostructure also exhibits substantial photovoltaic effect and rectifying characteristics. Photovoltaic property is found to be correlated with the ferroelectric polarization. Furthermore, the nonvolatile resistive switching in BiFeO3/TiO2 nano-heterostructure has been studied, which demonstrates that the observed resistive switching is most likely caused by the electric-field-induced carrier injection/migration and trapping/detrapping process at the hetero-interfaces. Therefore, BiFeO3/TiO2 nano-heterostructure coupled with logic, photovoltaics and memory characteristics holds promises for long-term technological applications in nanoelectronics devices.

  14. Giant Spin-Driven Ferroelectric Polarization in BiFeO3 at Room Temperature

    DOE PAGESBeta

    Lee, Jun Hee; Fishman, Randy S.

    2015-11-11

    Although BiFeO3 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 BiFeO3 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 BiFeO3 has a hidden record-high spin-driven polarization ( 3 C/cm2) at room-temperature. The huge ES polarizations can be tuned by coupling to the antiferrodistortive rotations.

  15. Transition probabilities of PrII-lines emitted from a ferroelectric plasma source

    NASA Astrophysics Data System (ADS)

    Goly, A.; Kusz, J.; Quang, B. Nguyen; Weniger, S.

    1991-03-01

    An argon-praseodymium plasma was generated under atmospheric pressure between a ceramic ferroelectric plate and a praseodymium plate. The system of plates was connected to an acoustic frequency supply. The plasma radiation was analyzed in the spectral range from 2000 to 7000 A by using a grating spectrograph with a linear dispersion near 1 mm/A, adopted to photoelectric measurements. The emission spectrum of praseodymium was recorded, and the intensities of a few hundred lines were measured. Transition probabilities were determined for 62 PrII-lines, using available lifetime data for excited levels and measured branching ratios of the corresponding lines. Reasonable agreement has been found between the experimental data of Lage and Whaling (1976) and some of the present results.

  16. Technology and Educational Buildings and Records for Management of Buildings. School Buildings Planning, Design, and Construction Series No. 7.

    ERIC Educational Resources Information Center

    Odell, John H.

    A school construction guide offers key personnel in school development projects information on the complex task of master planning and construction of schools in Australia. This chapter of the guide provides advice on how educational buildings should be designed to permit technological change with efficiency and minimum expense. Issues examined…

  17. Health Care Information Technology in Rural America: Electronic Medical Record Adoption Status in Meeting the National Agenda

    ERIC Educational Resources Information Center

    Bahensky, James A.; Jaana, Mirou; Ward, Marcia M.

    2008-01-01

    Continuing is a national political drive for investments in health care information technology (HIT) that will allow the transformation of health care for quality improvement and cost reduction. Despite several initiatives by the federal government to spur this development, HIT implementation has been limited, particularly in the rural market. The…

  18. Mississippi Curriculum Framework for Postsecondary Health Information Technology (CIP: 51.0707--Medical Records Technol./Tech.). Postsecondary Programs.

    ERIC Educational Resources Information Center

    Mississippi Research and Curriculum Unit for Vocational and Technical Education, State College.

    This document, which is intended for use by community and junior colleges throughout Mississippi, contains curriculum frameworks for the course sequences in the health information technology program. Presented in the introductory section are a description of the program and suggested course sequence. Section I lists baseline competencies, and…

  19. Formation of charged ferroelectric domain walls with controlled periodicity.

    PubMed

    Bednyakov, Petr S; Sluka, Tomas; Tagantsev, Alexander K; Damjanovic, Dragan; Setter, Nava

    2015-01-01

    Charged domain walls in proper ferroelectrics were shown recently to possess metallic-like conductivity. Unlike conventional heterointerfaces, these walls can be displaced inside a dielectric by an electric field, which is of interest for future electronic circuitry. In addition, theory predicts that charged domain walls may influence the electromechanical response of ferroelectrics, with strong enhancement upon increased charged domain wall density. The existence of charged domain walls in proper ferroelectrics is disfavoured by their high formation energy and methods of their preparation in predefined patterns are unknown. Here we develop the theoretical background for the formation of charged domain walls in proper ferroelectrics using energy considerations and outline favourable conditions for their engineering. We experimentally demonstrate, in BaTiO3 single crystals the controlled build-up of high density charged domain wall patterns, down to a spacing of 7 μm with a predominant mixed electronic and ionic screening scenario, hinting to a possible exploitation of charged domain walls in agile electronics and sensing devices. PMID:26516026

  20. Formation of charged ferroelectric domain walls with controlled periodicity

    PubMed Central

    Bednyakov, Petr S.; Sluka, Tomas; Tagantsev, Alexander K.; Damjanovic, Dragan; Setter, Nava

    2015-01-01

    Charged domain walls in proper ferroelectrics were shown recently to possess metallic-like conductivity. Unlike conventional heterointerfaces, these walls can be displaced inside a dielectric by an electric field, which is of interest for future electronic circuitry. In addition, theory predicts that charged domain walls may influence the electromechanical response of ferroelectrics, with strong enhancement upon increased charged domain wall density. The existence of charged domain walls in proper ferroelectrics is disfavoured by their high formation energy and methods of their preparation in predefined patterns are unknown. Here we develop the theoretical background for the formation of charged domain walls in proper ferroelectrics using energy considerations and outline favourable conditions for their engineering. We experimentally demonstrate, in BaTiO3 single crystals the controlled build-up of high density charged domain wall patterns, down to a spacing of 7 μm with a predominant mixed electronic and ionic screening scenario, hinting to a possible exploitation of charged domain walls in agile electronics and sensing devices. PMID:26516026

  1. Ferroelectric gated electrical transport in CdS nanotetrapods.

    PubMed

    Fu, Wangyang; Qin, Shengyong; Liu, Lei; Kim, Tae-Hwan; Hellstrom, Sondra; Wang, Wenlong; Liang, Wenjie; Bai, Xuedong; Li, An-Ping; Wang, Enge

    2011-05-11

    Complex nanostructures such as branched semiconductor nanotetrapods are promising building blocks for next-generation nanoelectronics. Here we report on the electrical transport properties of individual CdS tetrapods in a field effect transistor (FET) configuration with a ferroelectric Ba(0.7)Sr(0.3)TiO(3) film as high-k, switchable gate dielectric. A cryogenic four-probe scanning tunneling microscopy (STM) is used to probe the electrical transport through individual nanotetrapods at different temperatures. A p-type field effect is observed at room temperature, owing to the enhanced gate capacitance coupling. And the reversible remnant polarization of the ferroelectric gate dielectric leads to a well-defined nonvolatile memory effect. The field effect is shown to originate from the channel tuning in the arm/core/arm junctions of nanotetrapods. At low temperature (8.5 K), the nanotetrapod devices exhibit a ferroelectric-modulated single-electron transistor (SET) behavior. The results illustrate how the characteristics of a ferroelectric such as switchable polarization and high dielectric constant can be exploited to control the functionality of individual three-dimensional nanoarchitectures. PMID:21513340

  2. Single crystal ternary oxide ferroelectric integration with Silicon

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

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

  3. Nanocomposite Materials - Ferroelectric Nanoparticles Incorporated into Porous Matrix

    NASA Astrophysics Data System (ADS)

    Rysiakiewicz-Pasek, E.; Poprawski, R.; Ciżman, A.; Sieradzki, A.

    The aim of this work is to develop a technique of introducing selected ferroelectric materials (TGS, NaNO2, NaNO3, KNO3, ADP and KDP) into porous glasses with various average pore dimensions. The major efforts have been focused on the investigations of the influence of the pore size on physical properties and phase transition of nanocrystals embedded into porous matrix with different methods. The ferroelectrics have been introduced into porous glasses from the melt and a water solution. The results of electrical (dielectric, pyroelectric) and thermal (dilatometric and calorimetric) measurements have shown that the observed sequences of phase transitions in ferroelectric materials embedded into the porous glasses are similar to that in bulk crystals. The relationship between phase transition and melt temperatures versus average values of pore dimensions has been determined. The experimentally observed shift of phase transition temperatures is the superposition of the size effect and pressure effect created by the difference of thermal expansion coefficients of ferroelectrics nanoparticles and glass matrix.

  4. Quantum ferroelectricity in charge-transfer complex crystals

    PubMed Central

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

    2015-01-01

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

  5. Rational Design of Molecular Ferroelectric Materials and Nanostructures

    SciTech Connect

    Ducharme, Stephen

    2012-09-25

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

    The capacitive ferroelectric thermoelectric converter harvesting electrical energy through non-linear capacitance variation caused by changes in temperature is analyzed. The ferroelectric material used was the thin (0.5 μm) Ba0.3Sr0.7TiO3 film. On the basis of experimental dependencies of the ferroelectric film permittivity on temperature ranging from 100 K to 350 K under different electric fields up to 80 V/μm, the optimum values of operating temperatures and electric field for the energy harvesting optimization were determined. For the temperature oscillations of ±15 K around room temperature and electric field about 40 V/μm, the harvested energy was estimated as 30 mJ/cm3. It is shown that the use of thin ferroelectric films for rapid capacitance variation versus temperature and microelectromechanical systems for fast temperature modulations may be a relevant solution for creation of small power scale generators for portable electronics.

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

    PubMed

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

    2010-04-20

    Nanoscale and mesoscopic disorder and associated local hysteretic responses underpin the unique properties of spin and cluster glasses, phase-separated oxides, polycrystalline ferroelectrics, and ferromagnets alike. Despite the rich history of the field, the relationship between the statistical descriptors of hysteresis behavior such as Preisach density, and micro and nanostructure has remained elusive. By using polycrystalline ferroelectric capacitors as a model system, we now report quantitative nonlinearity measurements in 0.025-1 microm(3) volumes, approximately 10(6) times smaller than previously possible. We discover that the onset of nonlinear behavior with thickness proceeds through formation and increase of areal density of micron-scale regions with large nonlinear response embedded in a more weakly nonlinear matrix. This observation indicates that large-scale collective domain wall dynamics, as opposed to motion of noninteracting walls, underpins Rayleigh behavior in disordered ferroelectrics. The measurements provide evidence for the existence and extent of the domain avalanches in ferroelectric materials, forcing us to rethink 100-year old paradigms. PMID:20368462

  8. Phonon localization drives polar nanoregions in a relaxor ferroelectric

    SciTech Connect

    Manley, Michael E; Lynn, Jeffrey; Specht, Eliot D; Delaire, Olivier A; Bishop, Alan; Sahul, Raffi; Budai, John D

    2014-01-01

    Relaxor ferroelectrics1, which are utilized as actuators and sensors2-4, exemplify a class of poorly understood materials where interplay between disorder and phase instability results in inhomogeneous nanoregions. There is no definitive explanation for the onset of relaxor behavior (Burns temperature5, Td) or the origin of polar nanoregions (PNRs). Here we show a vibrational mode that localizes on cooling to Td, remains localized as PNRs form, and then delocalizes as PNRs grow using neutron scattering on relaxor (Pb(Mg1/3Nb2/3)O3)0.69-(PbTiO3)0.31 (PMN-31%PT). Although initially appearing like intrinsic local modes (ILMs)6-10, these modes differ below Td as they form a resonance with the ferroelectric phonon. At the resonance, nanoregions of standing ferroelectric phonons develop with a coherence length matching the PNRs. The size, shape, distribution, and temporal fluctuations of PNRs, and our observations, are explained by ferroelectric phonons trapped by disordered resonance modes via Anderson localization11-13. Our results show the size and shape of PNRs are not dictated by complex structural details, as always assumed, but by a phonon resonance wavevector. This simplification could guide the design of next generation relaxors.

  9. Operation of Ferroelectric Plasma Sources in a Gas Discharge Mode

    SciTech Connect

    A. Dunaevsky; N.J. Fisch

    2004-03-08

    Ferroelectric plasma sources in vacuum are known as sources of ablative plasma, formed due to surface discharge. In this paper, observations of a gas discharge mode of operation of the ferroelectric plasma sources (FPS) are reported. The gas discharge appears at pressures between approximately 20 and approximately 80 Torr. At pressures of 1-20 Torr, there is a transition from vacuum surface discharge to the gas discharge, when both modes coexist and the surface discharges sustain the gas discharge. At pressures between 20 and 80 Torr, the surface discharges are suppressed, and FPS operate in pure gas discharge mode, with the formation of almost uniform plasma along the entire surface of the ceramics between strips. The density of the expanding plasma is estimated to be about 1013 cm-3 at a distance of 5.5 mm from the surface. The power consumption of the discharge is comparatively low, making it useful for various applications. This paper also presents direct measurements of the yield of secondary electron emission from ferroelectric ceramics, which, at low energies of primary electrons, is high and dependent on the polarization of the ferroelectric material

  10. Properties of Ferroelectric Nanostructures: A Combined Theoretical and Experimental Approach

    SciTech Connect

    Bellaiche, Laurent; Fu, Huaxiang

    2008-01-24

    Our main goal was to develop and/or use numerical schemes, from first-principles, to understand (at a microscopic level and via a comparison with experimental data, when available) ferroelectric nanostructures, as well as to reveal their unusual properties.

  11. Quantum ferroelectricity in charge-transfer complex crystals.

    PubMed

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

    2015-01-01

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

  12. Magnetic domain wall induced ferroelectricity in double perovskites

    SciTech Connect

    Zhou, Hai Yang; Zhao, Hong Jian E-mail: xmchen59@zju.edu.cn; Chen, Xiang Ming E-mail: xmchen59@zju.edu.cn; Zhang, Wen Qing

    2015-04-13

    Recently, a magnetically induced ferroelectricity occurring at magnetic domain wall of double perovskite Lu{sub 2}CoMnO{sub 6} has been reported experimentally. However, there exists a conflict whether the electric polarization is along b or c direction. Here, by first-principles calculations, we show that the magnetic domain wall (with ↑↑↓↓ spin configuration) can lead to the ferroelectric displacements of R{sup 3+}, Ni{sup 2+}, Mn{sup 4+}, and O{sup 2−} ions in double perovskites R{sub 2}NiMnO{sub 6} (R = rare earth ion) via exchange striction. The resulted electric polarization is along b direction with the P2{sub 1} symmetry. We further reveal the origin of the ferroelectric displacements as that: (1) on a structural point of view, such displacements make the two out-of-plane Ni-O-Mn bond angles as well as Ni-Mn distance unequal, and (2) on an energy point of view, such displacements weaken the out-of-plane Ni-Mn super-exchange interaction obviously. Finally, our calculations show that such a kind of ferroelectric order is general in ferromagnetic double perovskites.

  13. First-principles prediction of a native ferroelectric metal

    NASA Astrophysics Data System (ADS)

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

    The possibility that metals may support ferroelectricity is an intriguing open issue. Over the years, various compounds have been referred to as ferroelectric metals, including non-centrosymmetric metals as well as ferroelectrics whose polar distortion survives moderate metallicity induced by doping or proximity. Yet, we think none of these systems embodies a truly ferroelectric metal with native switchable polarization and native metallicity coexisting in a single phase. Here we report a first-principles prediction of such a material. We show that the layered perovskite Bi5Ti5O17 has a non-zero density of states at the Fermi level and metal-like conductivity, as well as a spontaneous polarization in zero field. Further, we predict that the polarization of Bi5Ti5O17 is switchable both in principle (the material complies with the sufficient symmetry requirements) and in practice (in spite of being a metal, Bi5Ti5O17 can sustain a sizable potential drop along the polar direction, as needed to revert its polarization by application of an electric bias). Our results also reveal striking behaviors - such as the self screening mechanism at work in thin Bi5Ti5O17 layers - emerging from the intimate interplay between polar distortions and free carriers in such an exotic material. Supported by MIUR-PRIN, Fondazione Banco di Sardegna, FNR Luxembourg, MINECO-Spain, CINECA-ISCRA and CESGA.

  14. Pressure as a probe of the physics of relaxor ferroelectrics

    SciTech Connect

    SAMARA,GEORGE A.

    2000-01-25

    Pressure studies have provided new insights into the physics of compositionally-disordered ABO{sub 3} oxide relaxors. Specifically, results will be presented and discussed on a pressure-induced ferroelectric-to-relaxer crossover phenomenon, the continuous evolution of the energetic and dynamics of the relaxation process, and the interplay between pressure and electric field in determining the dielectric response.

  15. Residual ferroelectricity in barium strontium titanate thin film tunable dielectrics

    SciTech Connect

    Garten, L. M. Trolier-McKinstry, S.; Lam, P.; Harris, D.; Maria, J.-P.

    2014-07-28

    Loss reduction is critical to develop Ba{sub 1−x}Sr{sub x}TiO{sub 3} thin film tunable microwave dielectric components and dielectric energy storage devices. The presence of ferroelectricity, and hence the domain wall contributions to dielectric loss, will degrade the tunable performance in the microwave region. In this work, residual ferroelectricity—a persistent ferroelectric response above the global phase transition temperature—was characterized in tunable dielectrics using Rayleigh analysis. Chemical solution deposited Ba{sub 0.7}Sr{sub 0.3}TiO{sub 3} films, with relative tunabilities of 86% over 250 kV/cm at 100 kHz, demonstrated residual ferroelectricity 65 °C above the ostensible paraelectric transition temperature. Frequency dispersion observed in the dielectric temperature response was consistent with the presence of nanopolar regions as one source of residual ferroelectricity. The application of AC electric field for the Rayleigh analysis of these samples led to a doubling of the dielectric loss for fields over 10 kV/cm at room temperature.

  16. Generalized Ferroelectricity in the Mesomorphic Phase of Nylon Polymers

    NASA Astrophysics Data System (ADS)

    Zhang, Zhongbo; Zhu, Lei; Litt, Morton

    Novel ferroelectric polymers, featured by narrow electric displacement-electric (D-E) hysteresis loop, are attractive for electric energy storage applications due to their high dielectric constant and low loss property. Currently, only poly(vinylidene fluoride) (PVDF)-based copolymers (e-beamed) and terpolymers show novel ferroelectric behavior. It is desired to achieve novel ferroelectricity in other polymers such as nylons by carefully modifying the chemical and crystal structures. In this presentation, isomorphic crystals are successfully achieved by copolymerization of nylon 11 and nylon 12 with different compositions. In this way, both chemical and structural defects (i.e., dangling amide groups and kinked bonds) are introduced into the mesomorphic phase. As a consequence, hydrogen bonding interaction is successfully weakened and thus enhanced ferroelectricity with higher maximum polarization and better polarizability is obtained. In addition, for the purpose of further disturbing the mesomorphic phase and pinning effect, partially methylated nylon copolymers are synthesized. With the help of N-methylation of amide groups, the methylated nylon copolymers show relatively narrow hysteresis loops, suggesting the pinning effect from the N-methylated amide moieties.

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

    SciTech Connect

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

    2014-10-28

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

  18. Collective dynamics underpins Rayleigh behavior in disordered polycrystalline ferroelectrics

    PubMed Central

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

    2010-01-01

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

  19. Stabilizing the ferroelectric phase in doped hafnium oxide

    SciTech Connect

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

    2015-08-21

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

  20. The Effects of Architecture and Process on the Hardness of Programmable Technologies

    NASA Technical Reports Server (NTRS)

    Katz, Richard; Wang, J. J.; Reed, R.; Kleyner, I.; DOrdine, M.; McCollum, J,; Cronquist, B.; Howard, J.

    1999-01-01

    Architecture and process, combined, significantly affect the hardness of programmable technologies. The effects of high energy ions, ferroelectric memory architectures, and shallow trench isolation are investigated. A detailed single event latchup (SEL) study has been performed.