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Sample records for epitaxial perovskite ferroelectric

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

    Science.gov (United States)

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

    2018-05-01

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

  2. Ferroelectric ultrathin perovskite films

    Science.gov (United States)

    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.

  3. Atomic layer deposition of perovskite oxides and their epitaxial integration with Si, Ge, and other semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    McDaniel, Martin D.; Ngo, Thong Q.; Hu, Shen; Ekerdt, John G., E-mail: ekerdt@utexas.edu [Department of Chemical Engineering, The University of Texas at Austin, Austin, Texas 78712 (United States); Posadas, Agham; Demkov, Alexander A. [Department of Physics, The University of Texas at Austin, Austin, Texas 78712 (United States)

    2015-12-15

    Atomic layer deposition (ALD) is a proven technique for the conformal deposition of oxide thin films with nanoscale thickness control. Most successful industrial applications have been with binary oxides, such as Al{sub 2}O{sub 3} and HfO{sub 2}. However, there has been much effort to deposit ternary oxides, such as perovskites (ABO{sub 3}), with desirable properties for advanced thin film applications. Distinct challenges are presented by the deposition of multi-component oxides using ALD. This review is intended to highlight the research of the many groups that have deposited perovskite oxides by ALD methods. Several commonalities between the studies are discussed. Special emphasis is put on precursor selection, deposition temperatures, and specific property performance (high-k, ferroelectric, ferromagnetic, etc.). Finally, the monolithic integration of perovskite oxides with semiconductors by ALD is reviewed. High-quality epitaxial growth of oxide thin films has traditionally been limited to physical vapor deposition techniques (e.g., molecular beam epitaxy). However, recent studies have demonstrated that epitaxial oxide thin films may be deposited on semiconductor substrates using ALD. This presents an exciting opportunity to integrate functional perovskite oxides for advanced semiconductor applications in a process that is economical and scalable.

  4. Atomic layer deposition of perovskite oxides and their epitaxial integration with Si, Ge, and other semiconductors

    International Nuclear Information System (INIS)

    McDaniel, Martin D.; Ngo, Thong Q.; Hu, Shen; Ekerdt, John G.; Posadas, Agham; Demkov, Alexander A.

    2015-01-01

    Atomic layer deposition (ALD) is a proven technique for the conformal deposition of oxide thin films with nanoscale thickness control. Most successful industrial applications have been with binary oxides, such as Al 2 O 3 and HfO 2 . However, there has been much effort to deposit ternary oxides, such as perovskites (ABO 3 ), with desirable properties for advanced thin film applications. Distinct challenges are presented by the deposition of multi-component oxides using ALD. This review is intended to highlight the research of the many groups that have deposited perovskite oxides by ALD methods. Several commonalities between the studies are discussed. Special emphasis is put on precursor selection, deposition temperatures, and specific property performance (high-k, ferroelectric, ferromagnetic, etc.). Finally, the monolithic integration of perovskite oxides with semiconductors by ALD is reviewed. High-quality epitaxial growth of oxide thin films has traditionally been limited to physical vapor deposition techniques (e.g., molecular beam epitaxy). However, recent studies have demonstrated that epitaxial oxide thin films may be deposited on semiconductor substrates using ALD. This presents an exciting opportunity to integrate functional perovskite oxides for advanced semiconductor applications in a process that is economical and scalable

  5. Removable polytetrafluoroethylene template based epitaxy of ferroelectric copolymer thin films

    Science.gov (United States)

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

    2018-04-01

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

  6. Band gap engineering strategy via polarization rotation in perovskite ferroelectrics

    International Nuclear Information System (INIS)

    Wang, Fenggong; Grinberg, Ilya; Rappe, Andrew M.

    2014-01-01

    We propose a strategy to engineer the band gaps of perovskite oxide ferroelectrics, supported by first principles calculations. We find that the band gaps of perovskites can be substantially reduced by as much as 1.2 eV through local rhombohedral-to-tetragonal structural transition. Furthermore, the strong polarization of the rhombohedral perovskite is largely preserved by its tetragonal counterpart. The B-cation off-center displacements and the resulting enhancement of the antibonding character in the conduction band give rise to the wider band gaps of the rhombohedral perovskites. The correlation between the structure, polarization orientation, and electronic structure lays a good foundation for understanding the physics of more complex perovskite solid solutions and provides a route for the design of photovoltaic perovskite ferroelectrics

  7. Strain Engineering of Ferroelectric Domains in KxNa1−xNbO3 Epitaxial Layers

    Directory of Open Access Journals (Sweden)

    Jutta Schwarzkopf

    2017-08-01

    Full Text Available The application of lattice strain through epitaxial growth of oxide films on lattice mismatched perovskite-like substrates strongly influences the structural properties of ferroelectric domains and their corresponding piezoelectric behavior. The formation of different ferroelectric phases can be understood by a strain-phase diagram, which is calculated within the framework of the Landau–Ginzburg–Devonshire theory. In this paper, we illustrate the opportunity of ferroelectric domain engineering in the KxNa1−xNbO3 lead-free material system. In particular, the following examples are discussed in detail: (i Different substrates (NdGaO3, SrTiO3, DyScO3, TbScO3, and GdScO3 are used to systematically tune the incorporated epitaxial strain from compressive to tensile. This can be exploited to adjust the NaNbO3 thin film surface orientation and, concomitantly, the vector of electrical polarization, which rotates from mainly vertical to exclusive in-plane orientation. (ii In ferroelectric NaNbO3, thin films grown on rare-earth scandate substrates, highly regular stripe domain patterns are observed. By using different film thicknesses, these can be tailored with regard to domain periodicity and vertical polarization component. (iii A featured potassium concentration of x = 0.9 of KxNa1−xNbO3 thin films grown on (110 NdScO3 substrates favors the coexistence of two equivalent, monoclinic, but differently oriented ferroelectric phases. A complicated herringbone domain pattern is experimentally observed which consists of alternating MC and a1a2 domains. The coexistence of different types of ferroelectric domains leads to polarization discontinuities at the domain walls, potentially enabling high piezoelectric responses. In each of these examples, the experimental results are in excellent agreement with predictions based on the linear elasticity theory.

  8. Tensile strain effect in ferroelectric perovskite oxide thin films on spinel magnesium aluminum oxide substrate

    Science.gov (United States)

    Zhou, Xiaolan

    Ferroelectrics are used in FeRAM (Ferroelectric random-access memory). Currently (Pb,Zr)TiO3 is the most common ferroelectric material. To get lead-free and high performance ferroelectric material, we investigated perovskite ferroelectric oxides (Ba,Sr)TiO3 and BiFeO3 films with strain. Compressive strain has been investigated intensively, but the effects of tensile strain on the perovskite films have yet to be explored. We have deposited (Ba,Sr)TiO3, BiFeO3 and related films by pulsed laser deposition (PLD) and analyzed the films by X-ray diffractometry (XRD), atomic force microscopy (AFM), etc. To obtain inherently fully strained films, the selection of the appropriate substrates is crucial. MgAl2O4 matches best with good quality and size, yet the spinel structure has an intrinsic incompatibility to that of perovskite. We introduced a rock-salt structure material (Ni 1-xAlxO1+delta) as a buffer layer to mediate the structural mismatch for (Ba,Sr)TiO3 films. With buffer layer Ni1-xAlxO1+delta, we show that the BST films have high quality crystallization and are coherently epitaxial. AFM images show that the films have smoother surfaces when including the buffer layer, indicating an inherent compatibility between BST-NAO and NAO-MAO. In-plane Ferroelectricity measurement shows double hysteresis loops, indicating an antiferroelectric-like behavior: pinned ferroelectric domains with antiparallel alignments of polarization. The Curie temperatures of the coherent fully strained BST films are also measured. It is higher than 900°C, at least 800°C higher than that of bulk. The improved Curie temperature makes the use of BST as FeRAM feasible. We found that the special behaviors of ferroelectricity including hysteresis loop and Curie temperature are due to inherent fully tensile strain. This might be a clue of physics inside ferroelectric stain engineering. An out-of-plane ferroelectricity measurement would provide a full whole story of the tensile strain. However, a

  9. Effect of extrapolation length on the phase transformation of epitaxial ferroelectric thin films

    International Nuclear Information System (INIS)

    Hu, Z.S.; Tang, M.H.; Wang, J.B.; Zheng, X.J.; Zhou, Y.C.

    2008-01-01

    Effects of extrapolation length on the phase transformation of epitaxial ferroelectric thin films on dissimilar cubic substrates have been studied on the basis of the mean-field Landau-Ginzburg-Devonshire (LGD) thermodynamic theory by taking an uneven distribution of the interior stress with thickness into account. It was found that the polarization of epitaxial ferroelectric thin films is strongly dependent on the extrapolation length of films. The physical origin of the extrapolation length during the phase transformation from paraelectric to ferroelectric was revealed in the case of ferroelectric thin films

  10. Quantum mechanical studies of complex ferroelectric perovskites

    Science.gov (United States)

    Ramer, Nicholas John

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

  11. Interplay of Cation Ordering and Ferroelectricity in Perovskite Tin Iodides: Designing a Polar Halide Perovskite for Photovoltaic Applications

    Energy Technology Data Exchange (ETDEWEB)

    Gou, Gaoyang; Young, Joshua; Liu, Xian; Rondinelli, James M.

    2016-09-28

    Owing to its ideal semiconducting band gap and good carrier transport properties, the fully inorganic perovskite CsSnI3 has been proposed as a visible-light absorber for photovoltaic (PV) applications. However, compared to the organic inorganic lead halide perovskite CH3NH3PbI3, CsSnI3 solar cells display very low energy conversion efficiency. In this work, we propose a potential route to improve the PV properties of CsSnI3. Using first-principles calculations, we examine the crystal structures and electronic properties of CsSnI3, including its structural polymorphs. Next, we purposefully order Cs and Rb cations on the A site to create the double perovskite (CsRb)Sn2I6. We find that a stable ferroelectric polarization arises from the nontrivial coupling between polar displacements and octahedral rotations of the SnI6 network. These ferroelectric double perovskites are predicted to have energy band gaps and carrier effective masses similar to those of CsSnI3. More importantly, unlike nonpolar CsSnI3, the electric polarization present in ferroelectric (CsRb)Sn2I6 can effectively separate the photoexcited carriers, leading to novel ferroelectric PV materials with,potentially enhanced energy conversion efficiency.

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

    Science.gov (United States)

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

    2014-12-01

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

  13. Orientation control and domain structure analysis of {100}-oriented epitaxial ferroelectric orthorhombic HfO{sub 2}-based thin films

    Energy Technology Data Exchange (ETDEWEB)

    Katayama, Kiliha [Department of Innovative and Engineered Materials, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8502 (Japan); Shimizu, Takao [Materials Research Center for Element Strategy, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503 (Japan); Sakata, Osami [Synchrotron X-ray Station at SPring-8, National Institute for Materials Science (NIMS), 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148 (Japan); Shiraishi, Takahisa; Nakamura, Shogo; Kiguchi, Takanori; Akama, Akihiro; Konno, Toyohiko J. [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan); Uchida, Hiroshi [Department of Materials and Life Sciences, Sophia University, Chiyoda, Tokyo 102-8554 (Japan); Funakubo, Hiroshi, E-mail: funakubo.h.aa@m.titech.ac.jp [Department of Innovative and Engineered Materials, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8502 (Japan); Materials Research Center for Element Strategy, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503 (Japan)

    2016-04-07

    Orientation control of {100}-oriented epitaxial orthorhombic 0.07YO{sub 1.5}-0.93HfO{sub 2} films grown by pulsed laser deposition was investigated. To achieve in-plane lattice matching, indium tin oxide (ITO) and yttria-stabilized zirconia (YSZ) were selected as underlying layers. We obtained (100)- and (001)/(010)-oriented films on ITO and YSZ, respectively. Ferroelastic domain formation was confirmed for both films by X-ray diffraction using the superlattice diffraction that appeared only for the orthorhombic symmetry. The formation of ferroelastic domains is believed to be induced by the tetragonal–orthorhombic phase transition upon cooling the films after deposition. The present results demonstrate that the orientation of HfO{sub 2}-based ferroelectric films can be controlled in the same manner as that of ferroelectric films composed of conventional perovskite-type material such as Pb(Zr, Ti)O{sub 3} and BiFeO{sub 3}.

  14. Tunable band gap in epitaxial ferroelectric Ho(Mn,Ga)O{sub 3} films

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Daesu; Noh, Tae Won, E-mail: twnoh@snu.ac.kr [Center for Correlated Electron Systems, Institute for Basic Science, Seoul 151-742 (Korea, Republic of); Department of Physics and Astronomy, Seoul National University, Seoul 151-742 (Korea, Republic of); Choi, Woo Seok [Department of Physics, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of)

    2016-05-09

    Ferroelectrics have recently attracted attention as a new class of materials for use in optical and photovoltaic devices. We studied the electronic properties in epitaxially stabilized ferroelectric hexagonal Ho(Mn{sub 1−x}Ga{sub x})O{sub 3} (x = 0, 0.33, 0.67, and 1) thin films. Our films exhibited systematic changes in electronic structures, such as bandgap and optical transitions, according to the Ga concentration. In particular, the bandgap increased systematically from 1.4 to 3.2 eV, including the visible light region, with increasing Ga concentration from x = 0 to 1. These systematic changes, attributed to lattice parameter variations in epitaxial Ho(Mn{sub 1−x}Ga{sub x})O{sub 3} films, should prove useful for the design of optoelectronic devices based on ferroelectrics.

  15. Can Ferroelectric Polarization Explain the High Performance of Hybrid Halide Perovskite Solar Cells?

    NARCIS (Netherlands)

    Sherkar, Tejas; Koster, L. Jan Anton

    The power conversion efficiency of photovoltaic cells based on the use of hybrid halide perovskites, CH3NH3PbX3 (X = Cl, Br, I), now exceeds 20%. Recently, it was suggested that this high performance originates from the presence of ferroelectricity in the perovskite, which is hypothesized to lower

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

    Czech Academy of Sciences Publication Activity Database

    Tyunina, Marina; Yao, L.; Chvostová, Dagmar; Dejneka, Alexandr; Kocourek, Tomáš; Jelínek, Miroslav; Trepakov, Vladimír; van Dijken, S.

    2015-01-01

    Roč. 16, č. 2 (2015), 026002 ISSN 1468-6996 R&D Projects: GA ČR GAP108/12/1941 Institutional support: RVO:68378271 Keywords : epitaxial growth * ferroelectric nanofilms Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.433, year: 2015

  17. Flexoelectricity: strain gradient effects in ferroelectrics

    Energy Technology Data Exchange (ETDEWEB)

    Ma Wenhui [Department of Physics, Shantou Unversity, Shantou, Guangdong 515063 (China)

    2007-12-15

    Mechanical strain gradient induced polarization effect or flexoelectricity in perovskite-type ferroelectric and relaxor ferroelectric ceramics was investigated. The flexoelectric coefficients measured at room temperature ranged from about 1 {mu} C m{sup -1} for lead zirconate titanate to 100 {mu} C m{sup -1} for barium strontium titanate. Flexoelectric effects were discovered to be sensitive to chemical makeup, phase symmetry, and domain structures. Based on phenomenological discussion and experimental data on flexoelectricity, the present study proposed that mechanical strain gradient field could influence polarization responses in a way analogous to electric field. Flexoelectric coefficients were found to be nonlinearly enhanced by dielectric permittivity and strain gradient. Interfacial mismatch in epitaxial thin films can give rise to high strain gradients, enabling flexoelectric effects to make a significant impact in properly engineered ferroelectric heterostructure systems.

  18. Stress effects in ferroelectric perovskite thin-films

    Science.gov (United States)

    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

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

    Science.gov (United States)

    Kang, Sung Gu

    2018-06-01

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

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

    Science.gov (United States)

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

    2012-03-01

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

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

    Science.gov (United States)

    Hettiarachchi, Chaminda Lakmal

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

  2. Synchrotron X-ray studies of epitaxial ferroelectric thin films and nanostructures

    Science.gov (United States)

    Klug, Jeffrey A.

    The study of ferroelectric thin films is a field of considerable scientific and technological interest. In this dissertation synchrotron x-ray techniques were applied to examine the effects of lateral confinement and epitaxial strain in ferroelectric thin films and nanostructures. Three materials systems were investigated: laterally confined epitaxial BiFeO3 nanostructures on SrTiO3 (001), ultra-thin commensurate SrTiO 3 films on Si (001), and coherently strained films of BaTiO3 on DyScO3 (110). Epitaxial films of BiFeO3 were deposited by radio frequency magnetron sputtering on SrRuO3 coated SrTiO 3 (001) substrates. Laterally confined nanostructures were fabricated using focused ion-beam processing and subsequently characterized with focused beam x-ray nanodiffraction measurements with unprecedented spatial resolution. Results from a series of rectangular nanostructures with lateral dimensions between 500 nm and 1 mum and a comparably-sized region of the unpatterned BiFeO3 film revealed qualitatively similar distributions of local strain and lattice rotation with a 2-3 times larger magnitude of variation observed in those of the nanostructures compared to the unpatterned film. This indicates that lateral confinement leads to enhanced variation in the local strain and lattice rotation fields in epitaxial BiFeO3 nanostructures. A commensurate 2 nm thick film of SrTiO3 on Si was characterized by the x-ray standing wave (XSW) technique to determine the Sr and Ti cation positions in the strained unit cell in order to verify strain-induced ferroelectricity in SrTiO3/Si. A Si (004) XSW measurement at 10°C indicated that the average Ti displacement from the midpoint between Sr planes was consistent in magnitude to that predicted by a density functional theory (DFT) calculated ferroelectric structure. The Ti displacement determined from a 35°C measurement better matched a DFT-predicted nonpolar structure. The thin film extension of the XSW technique was employed to

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

    Science.gov (United States)

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

    2012-02-01

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

  4. Ab initio study on mechanical-bending-induced ferroelectric phase transition in ultrathin perovskite nanobelts

    International Nuclear Information System (INIS)

    Li, H.F.; Zhang, G.H.; Zheng, Yue; Wang, Biao; Chen, W.J.

    2014-01-01

    Based on first-principles calculations, we systematically investigated the structural, ferroelectric (FE), energetic and electronic properties of bended ultrathin PbTiO 3 and BaTiO 3 nanobelts in between flat sheet and nanotube configurations. It is found that both PbTiO 3 and BaTiO 3 ultrathin nanobelts can possess axial antiferrodistortive structural distortion (AFD distortion), and the magnitude of the AFD rotation angle is obviously determined by the bending curvature of the nanobelts. Meanwhile, spontaneous polarization can be retained in these single-unit-cell-thick nanobelts with contributions from the axial improper ferroelectricity and the radial flexoelectricity, which indicates that ultrathin perovskite nanobelts do not have a critical thickness. On the other hand, we found that the AFD distortion is stable and significant in PbTiO 3 nanobelts while it is metastable in BaTiO 3 nanobelts in comparison with the stable non-AFD structure without AFD distortion. This is due to the competition between AFD distortion and circumferential lattice extension in releasing the elastic energy in BaTiO 3 material. Moreover, we found that the electronic structure and bandgap of the nanobelts can be tuned by the bending curvature, indicating potential control of transport properties by mechanical bending. Our results gave more insight into the inherence of improper ferroelectricity in low-dimensional perovskite ferroelectrics

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

    Science.gov (United States)

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

    2018-04-01

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

  6. Effect of epitaxy on interband transitions in ferroelectric KNbO.sub.3./sub..

    Czech Academy of Sciences Publication Activity Database

    Tyunina, Marina; Yao, L.D.; Chvostová, Dagmar; Kocourek, Tomáš; Jelínek, Miroslav; Dejneka, Alexandr; van Dijken, S.

    2015-01-01

    Roč. 17, Apr (2015), 043048 ISSN 1367-2630 R&D Projects: GA ČR(CZ) GA15-13853S; GA ČR GA15-15123S Institutional support: RVO:68378271 Keywords : ferroelectric * epitaxy * optica Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.570, year: 2015

  7. Epitaxial stabilization of ordered Pd–Fe structures on perovskite substrates

    Energy Technology Data Exchange (ETDEWEB)

    Harton, Renee M., E-mail: reneehar@umich.edu [Department of Physics, University of Michigan, 450 Church St., Ann Arbor, MI 48109 (United States); Stoica, Vladimir A. [Department of Materials Science and Engineering, Pennsylvania State University, 201 Old Main, University Park, PA 16802 (United States); Clarke, Roy [Department of Physics, University of Michigan, 450 Church St., Ann Arbor, MI 48109 (United States)

    2017-05-01

    We report the fabrication of epitaxial ferromagnetic Pd{sub 3}Fe thin films on SrTiO{sub 3}(001) substrates by promoting the interdiffusion of an Fe/Pd multilayer heterostructure using thermal annealing. Prior to annealing, the results of in-situ Reflection High-Energy Electron Diffraction characterization suggest that each Fe and Pd layer exhibited an in-plane epitaxial relationship with the SrTiO{sub 3}(001) substrate. X-Ray diffraction and magneto-optic Kerr effect characterization, conducted post-annealing, demonstrate that the film composition is majority Pd{sub 3}Fe and exhibits in-plane magnetization reversal with a moderate coercive field of ≈760 Oe. This demonstration of an ordered atomic layer heterostructure grown on a perovskite substrate suggests a route to epitaxial interfacial structures which can achieve strain-assisted magnetic switching.

  8. Ferroelectricity of Sn-doped SrTiO3 perovskites with tin at both A and B sites

    Science.gov (United States)

    Suzuki, Shoichiro; Honda, Atsushi; Iwaji, Naoki; Higai, Shin'ichi; Ando, Akira; Takagi, Hiroshi; Kasatani, Hirofumi; Deguchi, Kiyoshi

    2012-08-01

    We successfully obtained Sn-doped SrTiO3 (SSTO) perovskites, and clarified their ferroelectricity and structural properties by using first-principles theoretical calculations. The ferroelectricity of SSTO was confirmed by the appearance of a dielectric permittivity maximum and a clear hysteresis loop of the relationship between the external electric field and the electric flux density below 180 K. X-ray diffraction and Raman spectra revealed the structural phase transition of SSTO at approximately 200 K. We directly observed by spherical aberration corrected scanning transmission electron microscopy with energy-dispersive x-ray spectroscopy that Sn ions are doped into both Sr and Ti sites (SnA and SnB), and that SnA is located at an off-centered position. We also performed theoretical analyses of SSTO and related perovskites, and found that SnA is preferentially located in an off-centered position and that SnA and the O6 octahedron, which includes SnB in its center, oscillate along the antiphase direction in the soft mode. Thus, we propose that the ferroelectricity of SSTO originates from the antiphase off-centering, which induces ferroelectric nanoregions in paraelectric SrTiO3.

  9. Process for forming epitaxial perovskite thin film layers using halide precursors

    Science.gov (United States)

    Clem, Paul G.; Rodriguez, Mark A.; Voigt, James A.; Ashley, Carol S.

    2001-01-01

    A process for forming an epitaxial perovskite-phase thin film on a substrate. This thin film can act as a buffer layer between a Ni substrate and a YBa.sub.2 Cu.sub.3 O.sub.7-x superconductor layer. The process utilizes alkali or alkaline metal acetates dissolved in halogenated organic acid along with titanium isopropoxide to dip or spin-coat the substrate which is then heated to about 700.degree. C. in an inert gas atmosphere to form the epitaxial film on the substrate. The YBCO superconductor can then be deposited on the layer formed by this invention.

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

    International Nuclear Information System (INIS)

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

    2005-01-01

    Integration of III-nitride electrical devices on the ferroelectric material lithium niobate (LiNbO 3 ) has been demonstrated. As a ferroelectric material, lithium niobate has a polarization which may provide excellent control of the polarity of III-nitrides. However, while high temperature, 1000 deg. C, thermal treatments produce atomically smooth surfaces, improving adhesion of GaN epitaxial layers on lithium niobate, repolarization of the substrate in local domains occurs. These effects result in multi domains of mixed polarization in LiNbO 3 , producing inversion domains in subsequent GaN epilayers. However, it is found that AlN buffer layers suppress inversion domains of III-nitrides. Therefore, two-dimensional electron gases in AlGaN/GaN heterojunction structures are obtained. Herein, the demonstration of the monolithic integration of high power devices with ferroelectric materials presents possibilities to control LiNbO 3 modulators on compact optoelectronic/electronic chips

  11. Reversible Polarization Rotation in Epitaxial Ferroelectric Bilayers

    DEFF Research Database (Denmark)

    Liu, Guangqing; Zhang, Qi; Huang, Hsin-Hui

    2016-01-01

    Polarization rotation engineering is a promising path to giant dielectric and electromechanical responses in ferroelectric materials and devices. This work demonstrates robust and reversible in- to out-of-plane polarization rotation in ultrathin (nanoscale) epitaxial (001) tetragonal PbZr0.3Ti0.7O3...... large-scale polarization rotation switching (≈60 μC cm−2) and an effective d 33 response 500% (≈250 pm V−1) larger than the PZT-R layer alone. Furthermore, this enhancement is stable for more than 107 electrical switching cycles. These bilayers present a simple and highly controllable means to design...... and optimize rotational polar systems as an alternate to traditional composition-based approaches. The precise control of the subtle interface-driven interactions between the lattice and the external factors that control polarization opens a new door to enhanced—or completely new—functional properties....

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

    Science.gov (United States)

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

    2016-07-01

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

  13. Structural, dielectric and ferroelectric properties of (Bi,Na)TiO3–BaTiO3 system studied by high throughput screening

    International Nuclear Information System (INIS)

    Hayden, Brian E.; Yakovlev, Sergey

    2016-01-01

    Thin-film materials libraries of the Bi 2 O 3 –Na 2 O–TiO 2 –BaO system in a broad composition range have been deposited in ultra-high vacuum from elemental evaporation sources and an oxygen plasma source. A high throughput approach was used for systematic compositional and structural characterization and the screening of the dielectric and ferroelectric properties. The perovskite (Bi,Na)TiO 3 –BaTiO 3 phase with a Ba concentration near the morphotropic phase boundary (ca. 6 at.%) exhibited a relative dielectric permittivity of 180, a loss tangent of 0.04 and remnant polarization of 19 μC/cm 2 . Compared to published data, observed remnant polarization is close to that known for epitaxially grown films but higher than the values reported for polycrystalline films. The high throughput methodology and systematic nature of the study allowed us to establish the composition boundaries of the phase with optimal dielectric and ferroelectric characteristics. - Highlights: • Bi 2 O 3 –Na 2 O–TiO 2 –BaO high throughput materials library was deposited using PVD method. • Materials were processed from individual molecular beam epitaxy sources of elements. • High throughput approach was used for structural, dielectric and ferroelectric study. • Composition boundaries of perovskite compounds with optimum properties are reported.

  14. Enhanced Piezoelectric Response in HybridPerovskite via Interfacing with Ferroelectric Pb(Zr,Ti)O3

    Science.gov (United States)

    Song, Jingfeng; Xiao, Zhiyong; Chen, Bo; Prockish, Spencer; Chen, Xuegang; Wang, Dong; Huang, Jinsong; Hong, Xia

    In this work, we have carried out a comprehensive study of the piezoelectric properties of polycrystalline hybrid perovskite CH3NH3PbI3 (MAPbI3) thin films on two types of substrates. We spin coated 20-100 nm MAPbI3 thin films on gold and ferroelectric Pb(Zr,Ti)O3 (PZT), and characterized their piezoelectric coefficient d33 using piezoresponse force microscopy (PFM). The MAPbI3 thin films on gold showed a d33 of 0.4 pm/V. The epitaxial PZT films ( 50 nm) were deposited on (La,Sr)MnO3/SrTiO3 substrates, with polarization uniformly oriented in the up direction. For MAPbI3 films on PZT, there are regions showing clear PFM phase response, suggesting that MAPbI3 is polar with out-of-plane polarization. The PFM amplitude image of MAPbI3 indicated the existence of both constructive and destructive piezoresponse with that of PZT. The extracted d33is4 pm/V, 10-fold higher than that on gold. The enhanced piezoresponse is attributed to the dipole-dipole interaction between MAPbI3 and PZT. Our study points to an effective route to engineer the piezoelectric properties MAPbI3 for applications such as mechanical actuators and energy harvesting.

  15. Cs/CsPbX3 (X = Br, Cl) epitaxial heteronanocrystals with magic-angle stable/metastable grain boundary

    Science.gov (United States)

    Zhang, Yumeng; Fan, Baolu; Wu, Wenhui; Fan, Jiyang

    2017-05-01

    Metal-semiconductor heteronanostructures are crucial building blocks of nanoscale electronic and optoelectronic devices. However, the lattice misfit remains a challenge in constructing heteronanostructures. Perovskite nanocrystals are superior candidates for constructing nanodevices owing to excellent optical, ferroelectric, and superconducting properties. We report the epitaxial growth of lattice-matched Cs/CsPbBr3 metal-semiconductor heteronanocrystals in a liquid medium. The well-crystallized ultrathin Cs layers grow epitaxially on the surfaces of colloidal CsPbBr3 nanocrystals, forming heteronanocrystals with interface diameters of several nanometers. Most of them are pseudomorphic with coherent interfaces free from dislocations, and the others exhibit discrete high-angle grain boundaries. The model based on the calculation of the elastic potential energy of the epilayer and analysis of the near-coincidence sites explains well the experimental result. The analysis shows that the excellent lattice match between the metal and the semiconductor ensures the ideal epitaxial-growth of both Cs/CsPbBr3 and Cs/CsPbCl3 heteronanocrystals. Such metal/semiconductor heteronanocrystals pave the way for developing perovskite-based nanodevices.

  16. Structural, dielectric and ferroelectric properties of (Bi,Na)TiO{sub 3}–BaTiO{sub 3} system studied by high throughput screening

    Energy Technology Data Exchange (ETDEWEB)

    Hayden, Brian E. [Ilika Technologies Plc., Kenneth Dibben House, Enterprise Road, University of Southampton Science Park, Chilworth, Southampton SO16 7NS (United Kingdom); Department of Chemistry, University of Southampton, Highfield, Southampton SO17 1BJ (United Kingdom); Yakovlev, Sergey, E-mail: sergey.yakovlev@ilika.com [Ilika Technologies Plc., Kenneth Dibben House, Enterprise Road, University of Southampton Science Park, Chilworth, Southampton SO16 7NS (United Kingdom)

    2016-03-31

    Thin-film materials libraries of the Bi{sub 2}O{sub 3}–Na{sub 2}O–TiO{sub 2}–BaO system in a broad composition range have been deposited in ultra-high vacuum from elemental evaporation sources and an oxygen plasma source. A high throughput approach was used for systematic compositional and structural characterization and the screening of the dielectric and ferroelectric properties. The perovskite (Bi,Na)TiO{sub 3}–BaTiO{sub 3} phase with a Ba concentration near the morphotropic phase boundary (ca. 6 at.%) exhibited a relative dielectric permittivity of 180, a loss tangent of 0.04 and remnant polarization of 19 μC/cm{sup 2}. Compared to published data, observed remnant polarization is close to that known for epitaxially grown films but higher than the values reported for polycrystalline films. The high throughput methodology and systematic nature of the study allowed us to establish the composition boundaries of the phase with optimal dielectric and ferroelectric characteristics. - Highlights: • Bi{sub 2}O{sub 3}–Na{sub 2}O–TiO{sub 2}–BaO high throughput materials library was deposited using PVD method. • Materials were processed from individual molecular beam epitaxy sources of elements. • High throughput approach was used for structural, dielectric and ferroelectric study. • Composition boundaries of perovskite compounds with optimum properties are reported.

  17. Flexoelectricity induced increase of critical thickness in epitaxial ferroelectric thin films

    International Nuclear Information System (INIS)

    Zhou Hao; Hong Jiawang; Zhang Yihui; Li Faxin; Pei Yongmao; Fang Daining

    2012-01-01

    Flexoelectricity describes the coupling between polarization and strain/stress gradients in insulating crystals. In this paper, using the Landau-Ginsburg-Devonshire phenomenological approach, we found that flexoelectricity could increase the theoretical critical thickness in epitaxial BaTiO 3 thin films, below which the switchable spontaneous polarization vanishes. This increase is remarkable in tensile films while trivial in compressive films due to the electrostriction caused decrease of potential barrier, which can be easily destroyed by the flexoelectricity, between the ferroelectric state and the paraelectric state in tensile films. In addition, the films are still in a uni-polar state even below the critical thickness due to the flexoelectric effect.

  18. Flexoelectricity induced increase of critical thickness in epitaxial ferroelectric thin films

    Energy Technology Data Exchange (ETDEWEB)

    Zhou Hao [State Key Laboratory for Turbulence and Complex Systems, College of Engineering, Peking University, Beijing 100871 (China); Hong Jiawang; Zhang Yihui [Department of Engineering Mechanics, Tsinghua University, Beijing 100084 (China); Li Faxin [State Key Laboratory for Turbulence and Complex Systems, College of Engineering, Peking University, Beijing 100871 (China); Pei Yongmao, E-mail: peiym@pku.edu.cn [State Key Laboratory for Turbulence and Complex Systems, College of Engineering, Peking University, Beijing 100871 (China); Fang Daining, E-mail: fangdn@pku.edu.cn [State Key Laboratory for Turbulence and Complex Systems, College of Engineering, Peking University, Beijing 100871 (China); Department of Engineering Mechanics, Tsinghua University, Beijing 100084 (China)

    2012-09-01

    Flexoelectricity describes the coupling between polarization and strain/stress gradients in insulating crystals. In this paper, using the Landau-Ginsburg-Devonshire phenomenological approach, we found that flexoelectricity could increase the theoretical critical thickness in epitaxial BaTiO{sub 3} thin films, below which the switchable spontaneous polarization vanishes. This increase is remarkable in tensile films while trivial in compressive films due to the electrostriction caused decrease of potential barrier, which can be easily destroyed by the flexoelectricity, between the ferroelectric state and the paraelectric state in tensile films. In addition, the films are still in a uni-polar state even below the critical thickness due to the flexoelectric effect.

  19. Upconversion photoluminescence of epitaxial Yb{sup 3+}/Er{sup 3+} codoped ferroelectric Pb(Zr,Ti)O{sub 3} films on silicon substrates

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Yang, E-mail: zhangy_acd@hotmail.com [IFW Dresden, P.O. Box 270116, D-01171 Dresden (Germany); Kämpfe, Thomas [Institut für Angewandte Physik, TU Dresden, 01062 Dresden (Germany); Bai, Gongxun [Department of Applied Physics, The Hong Kong Polytechnic University, Hong Kong (China); Mietschke, Michael; Yuan, Feifei; Zopf, Michael [IFW Dresden, P.O. Box 270116, D-01171 Dresden (Germany); Abel, Stefan [IBM Research GmbH, Saümerstrasse 4, 8803 Rüschlikon (Switzerland); Eng, Lukas M. [Institut für Angewandte Physik, TU Dresden, 01062 Dresden (Germany); Hühne, Ruben [IFW Dresden, P.O. Box 270116, D-01171 Dresden (Germany); Fompeyrine, Jean [IBM Research GmbH, Saümerstrasse 4, 8803 Rüschlikon (Switzerland); Ding, Fei, E-mail: f.ding@ifw-dresden.de [IFW Dresden, P.O. Box 270116, D-01171 Dresden (Germany); Schmidt, Oliver G. [IFW Dresden, P.O. Box 270116, D-01171 Dresden (Germany); Material Systems for Nanoelectronics, Chemnitz University of Technology, Reichenhainer strasse 70, 09107 Chemnitz (Germany)

    2016-05-31

    Thin films of Yb{sup 3+}/Er{sup 3+} codoped Pb(Zr,Ti)O{sub 3} (PZT:Yb/Er) have been epitaxially grown on the SrTiO{sub 3} buffered Si wafer by pulsed laser deposition. Strong upconversion photoluminescence was observed in the PZT:Yb/Er thin film. Using piezoresponse force microscopy, polar domains in the PZT:Yb/Er film can be reversibly switched with a phase change of 180°. Ferroelectric hysteresis loop shape with a well-saturated response was observed. The epitaxially grown lanthanide-doped PZT on silicon opens up a promising route to the integration of luminescent functional oxides on the silicon platform. - Highlights: • Epitaxial growth of Yb{sup 3+}/Er{sup 3+} codoped Pb(Zr,Ti)O{sub 3} films on SrTiO{sub 3} buffered silicon • Upconversion emissions were obtained from the lanthanide ion doped thin films. • Saturated ferroelectric hysteresis loops were observed. • Polar domains were switched by PFM with a phase change of 180°.

  20. Ferroelectric and piezoelectric responses of (110) and (001)-oriented epitaxial Pb(Zr{sub 0.52}Ti{sub 0.48})O{sub 3} thin films on all-oxide layers buffered silicon

    Energy Technology Data Exchange (ETDEWEB)

    Vu, Hien Thu [International Training Institute for Materials Science (ITIMS), Hanoi University of Science and Technology, No.1 Dai Co Viet Road, Hanoi 10000 (Viet Nam); Nguyen, Minh Duc, E-mail: minh.nguyen@itims.edu.vn [International Training Institute for Materials Science (ITIMS), Hanoi University of Science and Technology, No.1 Dai Co Viet Road, Hanoi 10000 (Viet Nam); Inorganic Materials Science (IMS), MESA + Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede (Netherlands); SolMateS B.V., Drienerlolaan 5, Building 6, 7522 NB Enschede (Netherlands); Houwman, Evert; Boota, Muhammad [Inorganic Materials Science (IMS), MESA + Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede (Netherlands); Dekkers, Matthijn [SolMateS B.V., Drienerlolaan 5, Building 6, 7522 NB Enschede (Netherlands); Vu, Hung Ngoc [International Training Institute for Materials Science (ITIMS), Hanoi University of Science and Technology, No.1 Dai Co Viet Road, Hanoi 10000 (Viet Nam); Rijnders, Guus [Inorganic Materials Science (IMS), MESA + Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede (Netherlands)

    2015-12-15

    Graphical abstract: The cross sections show a very dense structure in the (001)-oriented films (c,d), while an open columnar growth structure is observed in the case of the (110)-oriented films (a,b). The (110)-oriented PZT films show a significantly larger longitudinal piezoelectric coefficient (d33{sub ,f}), but smaller transverse piezoelectric coefficient (d31{sub ,f}) than the (001) oriented films. - Highlights: • We fabricate all-oxide, epitaxial piezoelectric PZT thin films on Si. • The orientation of the films can be controlled by changing the buffer layer stack. • The coherence of the in-plane orientation of the grains and grain boundaries affects the ferroelectric properties. • Good cycling stability of the ferroelectric properties of (001)-oriented PZT thin films. The (110)-oriented PZT thin films show a larger d33{sub ,f} but smaller d31{sub ,f} than the (001)-oriented films. - Abstract: Epitaxial ferroelectric Pb(Zr{sub 0.52}Ti{sub 0.48})O{sub 3} (PZT) thin films were fabricated on silicon substrates using pulsed laser deposition. Depending on the buffer layers and perovskite oxide electrodes, epitaxial films with different orientations were grown. (110)-oriented PZT/SrRuO{sub 3} (and PZT/LaNiO{sub 3}) films were obtained on YSZ-buffered Si substrates, while (001)-oriented PZT/SrRuO{sub 3} (and PZT/LaNiO{sub 3}) were fabricated with an extra CeO{sub 2} buffer layer (CeO{sub 2}/YSZ/Si). There is no effect of the electrode material on the properties of the films. The initial remnant polarizations in the (001)-oriented films are higher than those of (110)-oriented films, but it increases to the value of the (001) films upon cycling. The longitudinal piezoelectric d33{sub ,f} coefficients of the (110) films are larger than those of the (001) films, whereas the transverse piezoelectric d31{sub ,f} coefficients in the (110)-films are less than those in the (001)-oriented films. The difference is ascribed to the lower density (connectivity between

  1. In situ transmission electron microscopy study of the microstructural origins for the electric field-induced phenomena in ferroelectric perovskites

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Hanzheng [Iowa State Univ., Ames, IA (United States)

    2014-12-15

    Ferroelectrics are important materials due to their extensive technological applications, such as non-volatile memories, field-effect transistors, ferroelectric tunneling junctions, dielectric capacitors, piezoelectric transducers, sensors and actuators. As is well known, the outstanding dielectric, piezoelectric, and ferroelectric properties of these functional oxides originate from their ferroelectric domain arrangements and the corresponding evolution under external stimuli (e.g. electric field, stress, and temperature). Electric field has been known as the most efficient stimulus to manipulate the ferroelectric domains through polarization switching and alignment. Therefore, direct observation of the dynamic process of electric field-induced domain evolution and crystal structure transformation is of significant importance to understand the microstructural mechanisms for the functional properties of ferroelectrics. In this dissertation, electric field in situ transmission electron microscopy (TEM) technique was employed to monitor the real-time evolution of the domain morphology and crystal structure during various electrical processes: (1) the initial poling process, (2) the electric field reversal process, and (3) the electrical cycling process. Two types of perovskite-structured ceramics, normal ferroelectrics and relaxor ferroelectrics, were used for this investigation. In addition to providing the microscopic insight for some wellaccepted phase transformation rules, discoveries of some new or even unexpected physical phenomena were also demonstrated.

  2. Properties of epitaxial ferroelectric PbZr0.56Ti0.44O3 heterostructures with La0.5Sr0.5CoO3 metallic oxide electrodes

    International Nuclear Information System (INIS)

    Wang, F.; Leppaevuori, S.

    1997-01-01

    PbZr 0.56 Ti 0.44 O 3 (PZT) epitaxial ferroelectric thin films on a LaAlO 3 (100) substrate, covered by a metallic oxide electrode La 0.5 Sr 0.5 CoO 3 (LSCO) are demonstrated in this work. The films are fabricated by the sol endash gel method and effort was focused on thermal processing to obtain the desired epitaxial heterostructure. The dielectric and ferroelectric properties of PZT thin films were measured and it was found that they are as good as in the films deposited by other thin-film methods. The dielectric constant and the dissipation factor of the PZT films are, respectively, about 500 and 0.06 below 20 kHz. The remanent polarization P r is about 27 μC/cm 2 and the coercive field E c is about 50 kV/cm. It was found that the ferroelectric properties were significantly influenced by the microstructure of the PZT layers. The present study also showed that the fatigue characteristics of the epitaxial heterostructure with LSCO electrodes under a reversed electrical field are far superior to those obtained with a polycrystalline ferroelectric layer on Pt bottom electrodes. A low leakage current, about 3 μA/cm 2 at 0.5 MV/cm, was obtained for these epitaxial films. In addition, the optical transmittance spectrum of PZT thin films was also measured and the conduction mechanism is discussed.copyright 1997 American Institute of Physics

  3. Ferroelectric switching in epitaxial PbZr0.2Ti0.8O3/ZnO/GaN heterostructures

    Science.gov (United States)

    Wang, Juan; Salev, Pavel; Grigoriev, Alexei

    As a wide-bandgap semiconductor, ZnO has gained substantial interest due to its favorable properties including high electron mobility, strong room-temperature luminescence, etc. The main obstacle of its application is the lack of reproducible and low-resistivity p-type ZnO. P-type doping of ZnO through the interface charge injection, which can be achieved by the polarization switching of ferroelectric films, is a tempting solution. We explored ferroelectric switching behavior of PbZr0.2Ti0.8O3/ZnO/GaN heterostructures epitaxially grown on Sapphire substrates by RF sputtering. The electrical measurements of Pt/PbZr0.2Ti0.8O3/ZnO/GaN ferroelectric-semiconductor capacitors revealed unusual behavior that is a combination of polarization switching and a diode I-V characteristics.

  4. Non-collinear magnetism in multiferroic perovskites.

    Science.gov (United States)

    Bousquet, Eric; Cano, Andrés

    2016-03-31

    We present an overview of the current interest in non-collinear magnetism in multiferroic perovskite crystals. We first describe the different microscopic mechanisms giving rise to the non-collinearity of spins in this class of materials. We discuss, in particular, the interplay between non-collinear magnetism and ferroelectric and antiferrodistortive distortions of the perovskite structure, and how this can promote magnetoelectric responses. We then provide a literature survey on non-collinear multiferroic perovskites. We discuss numerous examples of spin cantings driving weak ferromagnetism in transition metal perovskites, and of spin-induced ferroelectricity as observed in the rare-earth based perovskites. These examples are chosen to best illustrate the fundamental role of non-collinear magnetism in the design of multiferroicity.

  5. Molecular ferroelectric contributions to anomalous hysteresis in hybrid perovskite solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Frost, Jarvist M.; Butler, Keith T.; Walsh, Aron, E-mail: a.walsh@bath.ac.uk [Centre for Sustainable Chemical Technologies and Department of Chemistry, University of Bath, Claverton Down, Bath BA2 7AY (United Kingdom)

    2014-08-01

    We report a model describing the molecular orientation disorder in CH{sub 3}NH{sub 3}PbI{sub 3}, solving a classical Hamiltonian parametrised with electronic structure calculations, with the nature of the motions informed by ab initio molecular dynamics. We investigate the temperature and static electric field dependence of the equilibrium ferroelectric (molecular) domain structure and resulting polarisability. A rich domain structure of twinned molecular dipoles is observed, strongly varying as a function of temperature and applied electric field. We propose that the internal electrical fields associated with microscopic polarisation domains contribute to hysteretic anomalies in the current-voltage response of hybrid organic-inorganic perovskite solar cells due to variations in electron-hole recombination in the bulk.

  6. Controlling the properties of ferroelectric-nickelate interfaces

    Science.gov (United States)

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

    2015-03-01

    Ferroelectrics are a class of materials that exhibit a stable, reversible polarization making them useful for non-volatile electronic devices. In devices consisting of thin film ferroelectric PZT acting as a gate and a thin film of the conductive oxide LaNiO3 grown on LaAlO3(001) acting as a channel, we have realized a large change in room temperature channel resistance by switching the ferroelectric polarization. The effect of switching the polarization of the ferroelectric is to modify the electronic structure of the interface between the gate and channel, resulting in conduction in the otherwise insulating ferroelectric. Here, we discuss how changing the epitaxial strain and interface termination of LaNiO3 can result in larger changes in resistivity. The epitaxial strain is varied by growing the devices on LaAlO3 for tensile strain and SrTiO3 for compressive strain. An interface termination of either an atomic layer of NiO2 or LaO is achieved via atomic layering using oxygen plasma assisted molecular beam epitaxy (MBE).

  7. O3 perovskite ceramic

    Indian Academy of Sciences (India)

    The prepared sample remains as double phases with the perovskite struc- ture. The structure ... Ferroelectric oxides with perovskite structure are the subject of many investigations. ... in optical devices and heterojunction solar cells. 1765 ...

  8. Impact of symmetry on the ferroelectric properties of CaTiO{sub 3} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Biegalski, Michael D.; Qiao, Liang [Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States); Gu, Yijia; Chen, Long-Qing [Department of Materials Science and Engineering, Pennsylvania State University, University Park, Pennsylvania 16801 (United States); Mehta, Apurva [Stanford Synchrotron Lightsource SLAC National Accelerator Laboratory, Menlo Park, California 94025 (United States); He, Qian; Borisevich, Albina [Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States); Takamura, Yayoi, E-mail: ytakamura@ucdavis.edu [Department of Chemical Engineering and Materials Science, University of California Davis, Davis, California 95616 (United States)

    2015-04-20

    Epitaxial strain is a powerful tool to induce functional properties such as ferroelectricity in thin films of materials that do not possess ferroelectricity in bulk form. In this work, a ferroelectric state was stabilized in thin films of the incipient ferroelectric, CaTiO{sub 3}, through the careful control of the biaxial strain state and TiO{sub 6} octahedral rotations. Detailed structural characterization was carried out by synchrotron x-ray diffraction and scanning transmission electron microscopy. CaTiO{sub 3} films grown on La{sub 0.18}Sr{sub 0.82}Al{sub 0.59}Ta{sub 0.41}O{sub 3} (LSAT) and NdGaO{sub 3} (NGO) substrates experienced a 1.1% biaxial strain state but differed in their octahedral tilt structures. A suppression of the out-of-plane rotations of the TiO{sub 6} octahedral in films grown on LSAT substrates resulted in a robust ferroelectric I4 mm phase with remnant polarization ∼5 μC/cm{sup 2} at 10 K and T{sub c} near 140 K. In contrast, films grown on NGO substrates with significant octahedral tilting showed reduced polarization and T{sub c}. These results highlight the key role played by symmetry in controlling the ferroelectric properties of perovskite oxide thin films.

  9. Combinatorial screening of halide perovskite thin films and solar cells by mask-defined IR laser molecular beam epitaxy

    OpenAIRE

    Kawashima, Kazuhiro; Okamoto, Yuji; Annayev, Orazmuhammet; Toyokura, Nobuo; Takahashi, Ryota; Lippmaa, Mikk; Itaka, Kenji; Suzuki, Yoshikazu; Matsuki, Nobuyuki; Koinuma, Hideomi

    2017-01-01

    Abstract As an extension of combinatorial molecular layer epitaxy via ablation of perovskite oxides by a pulsed excimer laser, we have developed a laser molecular beam epitaxy (MBE) system for parallel integration of nano-scaled thin films of organic?inorganic hybrid materials. A pulsed infrared (IR) semiconductor laser was adopted for thermal evaporation of organic halide (A-site: CH3NH3I) and inorganic halide (B-site: PbI2) powder targets to deposit repeated A/B bilayer films where the thic...

  10. Dimensional scaling of perovskite ferroelectric thin films

    Science.gov (United States)

    Keech, Ryan R.

    Dimensional size reduction has been the cornerstone of the exponential improvement in silicon based logic devices for decades. However, fundamental limits in the device physics were reached ˜2003, halting further reductions in clock speed without significant penalties in power consumption. This has motivated the research into next generation transistors and switching devices to reinstate the scaling laws for clock speed. This dissertation aims to support the scaling of devices that are based on ferroelectricity and piezoelectricity and to provide a roadmap for the corresponding materials performance. First, a scalable growth process to obtain highly {001}-oriented lead magnesium niobate - lead titanate (PMN-PT) thin films was developed, motivated by the high piezoelectric responses observed in bulk single crystals. It was found that deposition of a 2-3 nm thick PbO buffer layer on {111} Pt thin film bottom electrodes, prior to chemical solution deposition of PMN-PT reduces the driving force for Pb diffusion from the PMN-PT to the bottom electrode, and facilitates nucleation of {001}-oriented perovskite grains. Energy dispersive spectroscopy demonstrated that up to 10% of the Pb from a PMN-PT precursor solution may diffuse into the bottom electrode. PMN-PT grains with a mixed {101}/{111} orientation in a matrix of Pb-deficient pyrochlore phase were then promoted near the interface. When this is prevented, phase pure films with {001} orientation with Lotgering factors of 0.98-1.0, can be achieved. The resulting films of only 300 nm in thickness exhibit longitudinal effective d33,f coefficients of ˜90 pm/V and strain values of ˜1% prior to breakdown. 300 nm thick epitaxial and polycrystalline lead magnesium niobate - lead titanate (70PMN-30PT) blanket thin films were studied for the relative contributions to property thickness dependence from interfacial and grain boundary low permittivity layers. Epitaxial PMN-PT films were grown on SrRuO 3 /(001)SrTiO3, while

  11. Ferroelectric materials and their applications

    CERN Document Server

    Xu, Y

    2013-01-01

    This book presents the basic physical properties, structure, fabrication methods and applications of ferroelectric materials. These are widely used in various devices, such as piezoelectric/electrostrictive transducers and actuators, pyroelectric infrared detectors, optical integrated circuits, optical data storage, display devices, etc. The ferroelectric materials described in this book include a relatively complete list of practical and promising ferroelectric single crystals, bulk ceramics and thin films. Included are perovskite-type, lithium niobate, tungsten-bronze-type, water-soluable

  12. Ferroelectric Negative Capacitance Domain Dynamics

    OpenAIRE

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

    2017-01-01

    Transient negative capacitance effects in epitaxial ferroelectric Pb(Zr$_{0.2}$Ti$_{0.8}$)O$_3$ capacitors are investigated with a focus on the dynamical switching behavior governed by domain nucleation and growth. Voltage pulses are applied to a series connection of the ferroelectric capacitor and a resistor to directly measure the ferroelectric negative capacitance during switching. A time-dependent Ginzburg-Landau approach is used to investigate the underlying domain dynamics. The transien...

  13. Misfit strain dependence of ferroelectric and piezoelectric properties of clamped (001) epitaxial Pb(Zr0.52,Ti0.48)O3 thin films

    Science.gov (United States)

    Nguyen, Minh D.; Dekkers, Matthijn; Houwman, Evert; Steenwelle, Ruud; Wan, Xin; Roelofs, Andreas; Schmitz-Kempen, Thorsten; Rijnders, Guus

    2011-12-01

    A study on the effects of the residual strain in Pb(Zr0.52Ti0.48)O3 (PZT) thin films on the ferroelectric and piezoelectric properties is presented. Epitaxial (001)-oriented PZT thin film capacitors are sandwiched between SrRuO3 electrodes. The thin film stacks are grown on different substrate-buffer-layer combinations by pulsed laser deposition. Compressive or tensile strain caused by the difference in thermal expansion of the PZT film and substrate influences the ferroelectric and piezoelectric properties. All the PZT stacks show ferroelectric and piezoelectric behavior that is consistent with the theoretical model for strained thin films in the ferroelectric r-phase. We conclude that clamped (001) oriented Pb(Zr0.52Ti0.48)O3 thin films strained by the substrate always show rotation of the polarization vector.

  14. Growth of epitaxial Pb(Zr,Ti)O3 films by pulsed laser deposition

    Science.gov (United States)

    Lee, J.; Safari, A.; Pfeffer, R. L.

    1992-10-01

    Lead zirconate titanate (PZT) thin films with a composition near the morphotropic phase boundary have been grown on MgO (100) and Y1Ba2Cu3Ox (YBCO) coated MgO substrates. Substrate temperature and oxygen pressure were varied to achieve ferroelectric films with a perovskite structure. Films grown on MgO had the perovskite structure with an epitaxial relationship with the MgO substrate. On the other hand, films grown on the YBCO/MgO substrate had an oriented structure to the surface normal with a misorientation in the plane parallel to the surface. The measured dielectric constant and loss tangent at 1 kHz were 670 and 0.05, respectively. The remnant polarization and coercive field were 42 μC/cm2 and 53 kV/cm. A large internal bias field (12 kV/cm) was observed in the as-deposited state of the undoped PZT films.

  15. All-perovskite transparent high mobility field effect using epitaxial BaSnO3 and LaInO3

    Directory of Open Access Journals (Sweden)

    Useong Kim

    2015-03-01

    Full Text Available We demonstrate an all-perovskite transparent heterojunction field effect transistor made of two lattice-matched perovskite oxides: BaSnO3 and LaInO3. We have developed epitaxial LaInO3 as the gate oxide on top of BaSnO3, which were recently reported to possess high thermal stability and electron mobility when doped with La. We measured the dielectric properties of the epitaxial LaInO3 films, such as the band gap, dielectric constant, and the dielectric breakdown field. Using the LaInO3 as a gate dielectric and the La-doped BaSnO3 as a channel layer, we fabricated field effect device structure. The field effect mobility of such device was higher than 90 cm2 V−1 s−1, the on/off ratio was larger than 107, and the subthreshold swing was 0.65 V dec−1. We discuss the possible origins for such device performance and the future directions for further improvement.

  16. Ferroelectric switching of elastin

    Science.gov (United States)

    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

  17. Ceramic materials on perovskite-type structure for electronic applications

    International Nuclear Information System (INIS)

    Surowiak, Z.

    2003-01-01

    Ceramic materials exhibiting the perovskite-type structure constitute among others, resource base for many fields of widely understood electronics (i.e., piezoelectronics, accustoelectronics, optoelectronics, computer science, tele- and radioelectronics etc.). Most often they are used for fabrication of different type sensors (detectors), transducers, ferroelectric memories, limiters of the electronic current intensity, etc., and hence they are numbered among so-called intelligent materials. Prototype structure of this group of materials is the structure of the mineral called perovskite (CaTiO 3 ). By means of right choice of the chemical composition of ABO 3 and deforming the regular perovskite structure (m3m) more than 5000 different chemical compounds and solid solutions exhibiting the perovskite-type structure have been fabricated. The concept of perovskite functional ceramics among often things ferroelectric ceramics, pyroelectric ceramics, piezoelectric ceramics, electrostrictive ceramics, posistor ceramics, superconductive ceramics and ferromagnetic ceramics. New possibilities of application of the perovskite-type ceramics are opened by nanotechnology. (author)

  18. Heterogeneous Ferroelectric Solid Solutions Phases and Domain States

    CERN Document Server

    Topolov, Vitaly

    2012-01-01

    The book deals with perovskite-type ferroelectric solid solutions for modern materials science and applications, solving problems of complicated heterophase/domain structures near the morphotropic phase boundary and applications to various systems with morphotropic phases. In this book domain state–interface diagrams are presented for the interpretation of heterophase states in perovskite-type ferroelectric solid solutions. It allows to describe the stress relief in the presence of polydomain phases, the behavior of unit-cell parameters of coexisting phases and the effect of external electric fields. The novelty of the book consists in (i) the first systematization of data about heterophase states and their evolution in ferroelectric solid solutions (ii) the general interpretation of heterophase and domain structures at changing temperature, composition or electric field (iii) the complete analysis of interconnection domain structures, unit-cell parameters changes, heterophase structures and stress relief.

  19. The effects of strain relaxation on the dielectric properties of epitaxial ferroelectric Pb(Zr0.2Ti0.8)TiO3 thin films

    Science.gov (United States)

    Khan, Asif Islam; Yu, Pu; Trassin, Morgan; Lee, Michelle J.; You, Long; Salahuddin, Sayeef

    2014-07-01

    We study the effects of strain relaxation on the dielectric properties of epitaxial 40 nm Pb(Zr0.2Ti0.8)TiO3 (PZT) films. A significant increase in the defect and dislocation density due to strain relaxation is observed in PZT films with tetragonality c/a fatigue in ferroelectric materials.

  20. All-perovskite transparent high mobility field effect using epitaxial BaSnO{sub 3} and LaInO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Useong; Park, Chulkwon; Kim, Young Mo; Ju, Chanjong; Park, Jisung; Char, Kookrin, E-mail: kchar@phya.snu.ac.kr [Institute of Applied Physics, Department of Physics and Astronomy, Seoul National University, Seoul 151-747 (Korea, Republic of); Ha, Taewoo; Kim, Jae Hoon [Department of Physics, Yonsei University, Seoul 120-749 (Korea, Republic of); Kim, Namwook; Yu, Jaejun [Center for Theoretical Physics, Department of Physics and Astronomy, Seoul National University, Seoul 151-747 (Korea, Republic of)

    2015-03-01

    We demonstrate an all-perovskite transparent heterojunction field effect transistor made of two lattice-matched perovskite oxides: BaSnO{sub 3} and LaInO{sub 3}. We have developed epitaxial LaInO{sub 3} as the gate oxide on top of BaSnO{sub 3}, which were recently reported to possess high thermal stability and electron mobility when doped with La. We measured the dielectric properties of the epitaxial LaInO{sub 3} films, such as the band gap, dielectric constant, and the dielectric breakdown field. Using the LaInO{sub 3} as a gate dielectric and the La-doped BaSnO{sub 3} as a channel layer, we fabricated field effect device structure. The field effect mobility of such device was higher than 90 cm{sup 2} V{sup −1} s{sup −1}, the on/off ratio was larger than 10{sup 7}, and the subthreshold swing was 0.65 V dec{sup −1}. We discuss the possible origins for such device performance and the future directions for further improvement.

  1. Investigation of the epitaxial growth of Pb(Zr{sub 0,52}Ti{sub 0,48})O{sub 3} thin films and their application in ferroelectric superconducting field effect transistors; Untersuchung des epitaktischen Wachstums duenner Pb(Zr{sub 0,52}Ti{sub 0,48})O{sub 3}-Schichten und ihre Anwendung in ferroelektrischen supraleitenden Feldeffektransistoren

    Energy Technology Data Exchange (ETDEWEB)

    Aidam, R

    1999-02-01

    The influences of the polarization of ferroelectric Pb(Zr{sub 0.52}Ti{sub 0.48})O{sub 3} (PZT) films on the properties of YBa{sub 2}Cu{sub 3}O{sub x} (YBCO) films were investigated in ferroelectric superconducting field effect transistors (FSuFETs). First the epitaxial growth of PZT films deposited by reactive sputtering in an argon/oxygen atmosphere was investigated. SrTiO{sub 3} single crystals and YBCO thin films proved as suitable substrates. The lead content of the PZT films depended sensitively on the deposition temperature T{sub s} and the gas pressure. By using a high pressure of 0.26 mbar the correct stoichiometry could be achieved up to an maximum T{sub s} of 580 C. Above a minimum T{sub s} of 540 C the ferroelectric perovskite structure grew. In the optimum temperature range between 560 C and 580 C the films grew with a minimum mosaic spread of {delta}{omega} < 0.3 and a small amount of less than 1% of paraelectric phase. The best ferroelectric properties could be obtained for films with the highest degree of epitaxy and the correct stoichiometry. The maximum remanent polarization amounted P{sub r} = 61 {mu}C/cm{sup 2} and the coercive field E{sub C} was 150 kV/cm at 77 K. The breakdown field was four to five times larger than E{sub C}. Fatigue studies revealed a loss of switchable polarization of 30% after 10{sup 8} cycles at 77 K, whereas loss of retention and the effect of ageing were negligible. During the process of oxidation of the heterostructure at 400 C and an oxygen pressure of 800 mbar a reaction at the PZT/YBCO interface was observed, which lead to a degradation of the transport properties of the superconductor. This reaction could be avoided by a thin SrTiO{sub 3} buffer layer without disturbing the ferroelectric hysteresis essentially.

  2. Strain and Defect Engineering for Tailored Electrical Properties in Perovskite Oxide Thin Films and Superlattices

    Science.gov (United States)

    Hsing, Greg Hsiang-Chun

    Functional complex-oxides display a wide spectrum of physical properties, including ferromagnetism, piezoelectricity, ferroelectricity, photocatalytic and metal-insulating transition (MIT) behavior. Within this family, oxides with a perovskite structure have been widely studied, especially in the form of thin films and superlattices (heterostructures), which are strategically and industrially important because they offer a wide range of opportunities for electronic, piezoelectric and sensor applications. The first part of my thesis focuses on understanding and tuning of the built-in electric field found in PbTiO3/SrTiO3 (PTO/STO) ferroelectric superlattices and other ferroelectric films. The artificial layering in ferroelectric superlattices is a potential source of polarization asymmetry, where one polarization state is preferred over another. One manifestation of this asymmetry is a built-in electric field associated with shifted polarization hysteresis. Using off-axis RF-magnetron sputtering, we prepared several compositions of PTO/STO superlattice thin films; and for comparison PbTiO3/SrRuO 3 (PTO/SRO) superlattices, which have an additional intrinsic compositional asymmetry at the interface. Both theoretical modeling and experiments indicate that the layer-by-layer superlattice structure aligns the Pb-O vacancy defect dipoles in the c direction which contributes significantly to the built-in electric field; however the preferred polarization direction is different between the PTO/STO and PTO/SRO interface. By designing a hybrid superlattice that combines PTO/STO and PTO/SRO superlattices, we show the built-in electric field can be tuned to zero by changing the composition of the combo-superlattice. The second part of my thesis focuses on the epitaxial growth of SrCrO 3 (SCO) films. The inconsistent reports regarding its electrical and magnetic properties through the years stem from the compositionally and structurally ill-defined polycrystalline samples, but

  3. Structural Properties of Ferroelectric Perovskites

    National Research Council Canada - National Science Library

    Vanderbilt, David

    1998-01-01

    Under this research grant, we carried out realistic first-principles computer calculations of the ground-state and finite-temperature structural and dielectric properties of cubic perovskite materials...

  4. An Ultrathin Single Crystalline Relaxor Ferroelectric Integrated on a High Mobility Semiconductor

    Energy Technology Data Exchange (ETDEWEB)

    Moghadam, Reza M. [Department; Xiao, Zhiyong [Department; Ahmadi-Majlan, Kamyar [Department; Grimley, Everett D. [Department; Bowden, Mark [Environmental; amp, Biological Sciences Directorate, Pacific Northwest National Laboratory, Richland, Washington 99352, United States; Ong, Phuong-Vu [Physical; amp, Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, Washington 99352, United States; Chambers, Scott A. [Physical; amp, Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, Washington 99352, United States; Lebeau, James M. [Department; Hong, Xia [Department; Sushko, Peter V. [Physical; amp, Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, Washington 99352, United States; Ngai, Joseph H. [Department

    2017-09-13

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

  5. Integration and electrical properties of epitaxial LiNbO{sub 3} ferroelectric film on n-type GaN semiconductor

    Energy Technology Data Exchange (ETDEWEB)

    Hao Lanzhong, E-mail: hao_lanzhong@live.cn [State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054 (China); Faculty of Science, China University of Petroleum, Tsingtao, Shandong 266555 (China); Zhu Jun, E-mail: junzhu@uestc.edu.cn [State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054 (China); Liu Yunjie [Faculty of Science, China University of Petroleum, Tsingtao, Shandong 266555 (China); Wang Shuili; Zeng Huizhong; Liao Xiuwei; Liu Yingying; Lei Huawei; Zhang Ying; Zhang Wanli; Li Yanrong [State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054 (China)

    2012-01-31

    LiNbO{sub 3} (LNO) films were epitaxially grown on n-type GaN templates using pulsed laser deposition technique. The microstructures and electrical properties of the LNO/GaN heterostructure were characterized by x-ray diffraction, transmission electron microscope, and capacitance-voltage (C-V) measurements. The LNO films had two variants of grains rotated 60 Degree-Sign in-plane to each other. The epitaxial relationship of the respective variants could be built as [10-10]LNO//[1-210]GaN and [1-100]LNO//[11-20]GaN via 30 Degree-Sign in-plane rotation of the LNO film relative to the GaN layer. Interface analysis of the heterostructure demonstrated that two different epitaxial growth mechanisms vertical heteroepitaxy and lateral homoepitaxy, should happen at the interface of LNO/GaN. Counterclockwise C-V windows induced by the ferroelectric polarizations of LNO film could be observed clearly. The size of the window increased with increasing the sweep bias and a large window of 5.8 V was achieved at {+-} 15 V. By solving Poisson and drift-diffusion equations, the physical mechanisms of the C-V characteristics were demonstrated.

  6. Optical properties of ferroelectric epitaxial K.sub.0.5./sub.Na.sub.0.5./sub.NbO.sub.3./sub. films in visible to ultraviolet range

    Czech Academy of Sciences Publication Activity Database

    Chernova, Ekaterina; Pacherová, Oliva; Kocourek, Tomáš; Jelínek, Miroslav; Dejneka, Alexandr; Tyunina, Marina

    2016-01-01

    Roč. 11, č. 4 (2016), 1-9, č. článku e0153261. E-ISSN 1932-6203 R&D Projects: GA ČR GA15-13778S Institutional support: RVO:68378271 Keywords : optical properties * ferroelectric * epitaxial films Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.806, year: 2016

  7. Self-assembled single-phase perovskite nanocomposite thin films.

    Science.gov (United States)

    Kim, Hyun-Suk; Bi, Lei; Paik, Hanjong; Yang, Dae-Jin; Park, Yun Chang; Dionne, Gerald F; Ross, Caroline A

    2010-02-10

    Thin films of perovskite-structured oxides with general formula ABO(3) have great potential in electronic devices because of their unique properties, which include the high dielectric constant of titanates, (1) high-T(C) superconductivity in cuprates, (2) and colossal magnetoresistance in manganites. (3) These properties are intimately dependent on, and can therefore be tailored by, the microstructure, orientation, and strain state of the film. Here, we demonstrate the growth of cubic Sr(Ti,Fe)O(3) (STF) films with an unusual self-assembled nanocomposite microstructure consisting of (100) and (110)-oriented crystals, both of which grow epitaxially with respect to the Si substrate and which are therefore homoepitaxial with each other. These structures differ from previously reported self-assembled oxide nanocomposites, which consist either of two different materials (4-7) or of single-phase distorted-cubic materials that exhibit two or more variants. (8-12) Moreover, an epitaxial nanocomposite SrTiO(3) overlayer can be grown on the STF, extending the range of compositions over which this microstructure can be formed. This offers the potential for the implementation of self-organized optical/ferromagnetic or ferromagnetic/ferroelectric hybrid nanostructures integrated on technologically important Si substrates with applications in magnetooptical or spintronic devices.

  8. Field-induced resistance switching at metal/perovskite manganese oxide interface

    International Nuclear Information System (INIS)

    Ohkubo, I.; Tsubouchi, K.; Harada, T.; Kumigashira, H.; Itaka, K.; Matsumoto, Y.; Ohnishi, T.; Lippmaa, M.; Koinuma, H.; Oshima, M.

    2008-01-01

    Planar type metal/insulator/metal structures composed of an epitaxial perovskite manganese oxide layer and various metal electrodes were prepared for electric-field-induced resistance switching. Only the electrode pairs including Al show good resistance switching and the switching ratio reaches its maximum of 1000. This resistance switching occurs around the interface between Al electrodes and epitaxial perovskite manganese oxide thin films

  9. Composition driven structural instability in perovskite ferroelectrics

    Directory of Open Access Journals (Sweden)

    Chao Xu

    2017-04-01

    Full Text Available Ferroelectric solid solutions usually exhibit enhanced functional properties at the morphotropic phase boundary separating two ferroelectric phases with different orientations of polarization. The underlying mechanism is generally associated with polarization rotational instability and the flattened free energy profile. In this work we show that the polarization extensional instability can also be induced at the morphotropic phase boundary beyond the reported polar-nonpolar phase boundary. The piezoelectricity enhanced by this mechanism exhibits excellent thermal stability, which helps to develop high performance piezoelectric materials with good temperature stability.

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

    Science.gov (United States)

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

    2013-11-28

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

  11. Tuning structure in epitaxial Pb(Mg{sub 1/3}Nb{sub 2/3})O{sub 3}–PbTiO{sub 3} thin films by using miscut substrates

    Energy Technology Data Exchange (ETDEWEB)

    Mietschke, M., E-mail: m.mietschke@ifw-dresden.de [IFW Dresden, P.O. Box 270116, D-01171 Dresden (Germany); Dresden University of Technology, Faculty of Mechanical Science and Engineering, D-01062 Dresden (Germany); Oswald, S.; Fähler, S. [IFW Dresden, P.O. Box 270116, D-01171 Dresden (Germany); Schultz, L. [IFW Dresden, P.O. Box 270116, D-01171 Dresden (Germany); Dresden University of Technology, Faculty of Mechanical Science and Engineering, D-01062 Dresden (Germany); Hühne, R. [IFW Dresden, P.O. Box 270116, D-01171 Dresden (Germany)

    2015-08-31

    Pb(Mg{sub 1/3}Nb{sub 2/3})O{sub 3}–PbTiO{sub 3} (PMN–PT) is one of the most promising ferroelectric material for actuator, dielectric and electrocaloric applications. However, oriented and phase pure thin films are essential to use the outstanding properties of these compounds. In this work it is demonstrated that the use of miscut substrates influences the growth mechanism leading to a significantly broader deposition window to achieve the required film quality. Therefore, epitaxial 0.68Pb(Mg{sub 1/3}Nb{sub 2/3})O{sub 3}–0.32PbTiO{sub 3} films were grown by pulsed laser deposition on (001)-oriented single crystalline SrTiO{sub 3} (STO) substrates with a miscut angle between 0 and 15° towards the [100] direction using a conducting La{sub 0.7}Sr{sub 0.3}CoO{sub 3} buffer layer. The influence of the vicinal angle on the PMN–PT structure was studied by high resolution X-ray diffraction, X-ray photoelectron spectroscopy and transmission electron microscopy. A nearly pure perovskite phase growth with a cube-on-cube epitaxial relationship was obtained on all miscut STO substrates, whereas a significant volume fraction of the pyrochlore phase was present on the standard substrate. Reciprocal space measurements revealed a peak split of the perovskite reflections indicating structural variants of PMN–PT with different c/a ratios. An additional tilting of the PMN–PT planes with respect to the buffer layer was observed on some samples, which might be explained with the incorporation of dislocations according to the Nagai model. Polarization loops were measured in a temperature range between room temperature and 150 °C showing a sharp drop of the remanent polarization above 65 °C on vicinal substrates. - Highlights: • Epitaxial growth of pure perovskite Pb (Mg{sub 1}/{sub 3}Nb{sub 2}/{sub 3})O{sub 3}–PbTiO{sub 3} on miscut SrTiO{sub 3}. • Significant broadening of the deposition window for pyrochlore-free films. • Dependence of the structural parameters

  12. Negative capacitance in a ferroelectric capacitor.

    Science.gov (United States)

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

    2015-02-01

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

  13. Ferroelectric capacitor with reduced imprint

    Science.gov (United States)

    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.

  14. NOx Binding and Dissociation: Enhanced Ferroelectric Surface Chemistry by Catalytic Monolayers

    Science.gov (United States)

    Kakekhani, Arvin; Ismail-Beigi, Sohrab

    2013-03-01

    NOx molecules are regulated air pollutants produced during automotive combustion. As part of an effort to design viable catalysts for NOx decomposition operating at higher temperatures that would allow for improved fuel efficiency, we examine NOx chemistry on ferroelectric perovskite surfaces. Changing the direction of ferroelectric polarization can modify surface electronic properties and may lead to switchable surface chemistry. Here, we describe our recent work on potentially enhanced surface chemistry using catalytic RuO2 monolayers on perovskite ferroelectric substrates. In addition to thermodynamic stabilization of the RuO2 layer, we present results on the polarization-dependent binding of NO, O2, N2, and atomic O and N. We present results showing that one key problem with current catalysts, involving the difficulty of releasing dissociation products (especially oxygen), can be ameliorated by this method. Primary support from Toyota Motor Engineering and Manufacturing, North America, Inc.

  15. Phase transition in metastable perovskite Pb(AlNb)0,5O3

    International Nuclear Information System (INIS)

    Zhabko, T.E.; Olekhnovich, N.M.; Shilin, A.D.

    1987-01-01

    Dielectric properties of metastable perovskite Pb(AlNb) 0.5 O 3 and X-ray temperature investigations of both perovskite and pyrochlore modifications of the given compound are studied. Samples with the perovskite structure are prepared from the pyrochlorephase at 4-5 GPa pressure and 1170-1270 K. Ferroelectric phase transition is shown to occur in the metastable perovskite phase Pb(AlNb) 0.5 O 3 at 170 K

  16. Manipulating the ferroelectric polarization state of BaTiO{sub 3} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Datta, S.; Rioult, M.; Stanescu, D.; Magnan, H.; Barbier, A., E-mail: antoine.barbier@cea.fr

    2016-05-31

    Controlling the ferroelectric polarization at macroscopic or microscopic levels is crucial in the framework of the development of ferroelectric materials used in yet challenging photo-electrochemical (PEC) cells and spintronic applications. We report here on polarization methods allowing to electrically polarize prototypical samples of BaTiO{sub 3} (001) films. Epitaxial single crystalline layers were grown up to a thickness of 25 nm by atomic oxygen assisted molecular beam epitaxy on 1 at.% Nb doped SrTiO{sub 3} (001) single crystals. The samples were both microscopically and macroscopically polarized using Piezoresponse Force Microscopy and electrochemical poling in an electrolyte respectively. In addition we demonstrate the possibility to retrieve a quasi-native mixed ferroelectric polarization state after annealing. These polarization methods may be applied to many other ferroelectric thin films. - Highlights: • Ferroelectricity of BaTiO{sub 3} layers can be micro- and macroscopically controlled. • Microscopic ferroelectric domains are defined with piezoresponse force microscopy. • Poling in a LiClO{sub 4} electrolyte is a macroscopic poling method. • Air annealing above the Curie temperature “resets” the polarization state.

  17. High-Performance Single-Crystalline Perovskite Thin-Film Photodetector

    KAUST Repository

    Yang, Zhenqian

    2018-01-10

    The best performing modern optoelectronic devices rely on single-crystalline thin-film (SC-TF) semiconductors grown epitaxially. The emerging halide perovskites, which can be synthesized via low-cost solution-based methods, have achieved substantial success in various optoelectronic devices including solar cells, lasers, light-emitting diodes, and photodetectors. However, to date, the performance of these perovskite devices based on polycrystalline thin-film active layers lags behind the epitaxially grown semiconductor devices. Here, a photodetector based on SC-TF perovskite active layer is reported with a record performance of a 50 million gain, 70 GHz gain-bandwidth product, and a 100-photon level detection limit at 180 Hz modulation bandwidth, which as far as we know are the highest values among all the reported perovskite photodetectors. The superior performance of the device originates from replacing polycrystalline thin film by a thickness-optimized SC-TF with much higher mobility and longer recombination time. The results indicate that high-performance perovskite devices based on SC-TF may become competitive in modern optoelectronics.

  18. Electrical characterisation of ferroelectric field effect transistors based on ferroelectric HfO2 thin films

    International Nuclear Information System (INIS)

    Yurchuk, Ekaterina

    2015-01-01

    Ferroelectric field effect transistor (FeFET) memories based on a new type of ferroelectric material (silicon doped hafnium oxide) were studied within the scope of the present work. Utilisation of silicon doped hafnium oxide (Si:HfO 2 ) thin films instead of conventional perovskite ferroelectrics as a functional layer in FeFETs provides compatibility to the CMOS process as well as improved device scalability. The influence of different process parameters on the properties of Si:HfO 2 thin films was analysed in order to gain better insight into the occurrence of ferroelectricity in this system. A subsequent examination of the potential of this material as well as its possible limitations with the respect to the application in non-volatile memories followed. The Si:HfO 2 -based ferroelectric transistors that were fully integrated into the state-of-the-art high-k metal gate CMOS technology were studied in this work for the first time. The memory performance of these devices scaled down to 28 nm gate length was investigated. Special attention was paid to the charge trapping phenomenon shown to significantly affect the device behaviour.

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

    Energy Technology Data Exchange (ETDEWEB)

    Gou, Gaoyang [Frontier Institute; Charles, Nenian [Department of Materials Science and Engineering, Drexel University, Philadelphia, Pennsylvania 19104, United States; Shi, Jing [MOE Key Laboratory; Rondinelli, James M. [Department; Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, United States

    2017-09-11

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

  20. Resistance switching memory in perovskite oxides

    International Nuclear Information System (INIS)

    Yan, Z.B.; Liu, J.-M.

    2015-01-01

    The resistance switching behavior has recently attracted great attentions for its application as resistive random access memories (RRAMs) due to a variety of advantages such as simple structure, high-density, high-speed and low-power. As a leading storage media, the transition metal perovskite oxide owns the strong correlation of electrons and the stable crystal structure, which brings out multifunctionality such as ferroelectric, multiferroic, superconductor, and colossal magnetoresistance/electroresistance effect, etc. The existence of rich electronic phases, metal–insulator transition and the nonstoichiometric oxygen in perovskite oxide provides good platforms to insight into the resistive switching mechanisms. In this review, we first introduce the general characteristics of the resistance switching effects, the operation methods and the storage media. Then, the experimental evidences of conductive filaments, the transport and switching mechanisms, and the memory performances and enhancing methods of perovskite oxide based filamentary RRAM cells have been summarized and discussed. Subsequently, the switching mechanisms and the performances of the uniform RRAM cells associating with the carrier trapping/detrapping and the ferroelectric polarization switching have been discussed. Finally, the advices and outlook for further investigating the resistance switching and enhancing the memory performances are given

  1. Optical and electro-optic anisotropy of epitaxial PZT thin films

    Science.gov (United States)

    Zhu, Minmin; Du, Zehui; Jing, Lin; Yoong Tok, Alfred Iing; Tong Teo, Edwin Hang

    2015-07-01

    Strong optical and electro-optic (EO) anisotropy has been investigated in ferroelectric Pb(Zr0.48Ti0.52)O3 thin films epitaxially grown on Nb-SrTiO3 (001), (011), and (111) substrates using magnetron sputtering. The refractive index, electro-optic, and ferroelectric properties of the samples demonstrate the significant dependence on the growth orientation. The linear electro-optic coefficients of the (001), (011), and (111)-oriented PZT thin films were 270.8, 198.8, and 125.7 pm/V, respectively. Such remarkable anisotropic EO behaviors have been explained according to the structure correlation between the orientation dependent distribution, spontaneous polarization, epitaxial strain, and domain pattern.

  2. Ferroelectric negative capacitance domain dynamics

    Science.gov (United States)

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

    2018-05-01

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

  3. Electrical characterisation of ferroelectric field effect transistors based on ferroelectric HfO{sub 2} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Yurchuk, Ekaterina

    2015-02-06

    Ferroelectric field effect transistor (FeFET) memories based on a new type of ferroelectric material (silicon doped hafnium oxide) were studied within the scope of the present work. Utilisation of silicon doped hafnium oxide (Si:HfO{sub 2}) thin films instead of conventional perovskite ferroelectrics as a functional layer in FeFETs provides compatibility to the CMOS process as well as improved device scalability. The influence of different process parameters on the properties of Si:HfO{sub 2} thin films was analysed in order to gain better insight into the occurrence of ferroelectricity in this system. A subsequent examination of the potential of this material as well as its possible limitations with the respect to the application in non-volatile memories followed. The Si:HfO{sub 2}-based ferroelectric transistors that were fully integrated into the state-of-the-art high-k metal gate CMOS technology were studied in this work for the first time. The memory performance of these devices scaled down to 28 nm gate length was investigated. Special attention was paid to the charge trapping phenomenon shown to significantly affect the device behaviour.

  4. Growth and magnetotransport properties of epitaxial films of the layered perovskite La2-2xSr1+2xMn2O7

    International Nuclear Information System (INIS)

    Philipp, J.B.; Alff, L.; Gross, R.; Klein, J.; Recher, C.

    2002-01-01

    Epitaxial thin films of the bilayered perovskite La 2-2x Sr 1+2x Mn 2 O 7 (x=0.3, 0.4) have been grown by laser molecular beam epitaxy on NdGaO 3 substrates. Magnetotransport measurements with the current in the ab-plane and along the c-axis direction showed an intrinsic c-axis tunneling magnetoresistance effect associated with nonlinear current-voltage-characteristics for the x=0.3 compound. Besides the colossal magnetoresistance effect around the Curie temperature T C , at temperatures below about 40 K an additional high-field magnetoresistance was found most likely due to a strain and disorder induced re-entrant spin glass state in both the x=0.3 and 0.4 compounds. Our experiments show that the substrate induced coherency strain in the high quality epitaxial films results in magnetotransport properties that show markedly different behavior from those of single crystals. (orig.)

  5. Ferroelectric properties of tungsten bronze morphotropic phase boundary systems

    International Nuclear Information System (INIS)

    Oliver, J.R.; Neurgaonkar, R.R.; Cross, L.E.; Pennsylvania State Univ., University Park, PA

    1989-01-01

    Tungsten bronze ferroelectrics which have a morphotropic phase boundary (MPB) can have a number or enhanced dielectric, piezoelectric, and electrooptic properties compared to more conventional ferroelectric materials. The structural and ferroelectric properties of several MPB bronze systems are presented, including data from sintered and hot-pressed ceramics, epitaxial thin films, and bulk single crystals. Included among these are three systems which had not been previously identified as morphotropic. The potential advantages and limitations of these MPB systems are discussed, along with considerations of the appropriate growth methods for their possible utilization in optical, piezoelectric, or pyroelectric device applications

  6. Pseudo Jahn–Teller origin of ferroelectric instability in BaTiO{sub 3} type perovskites: The Green's function approach and beyond

    Energy Technology Data Exchange (ETDEWEB)

    Polinger, V., E-mail: polinv@uw.edu [Department of Physics, University of Washington, Seattle, WA 98195-1560 (United States); Garcia-Fernandez, P. [Ciencias de la Tierra y Física de la Materia Condensada, Universidad de Cantabria, Avenida de los Castros s/n, E-39005 Santander (Spain); Bersuker, I.B. [Department of Chemistry and Biochemistry, The University of Texas at Austin, Austin, TX 78712-0165 (United States)

    2015-01-15

    The local origin of dipolar distortions in ABO{sub 3} perovskite crystals is reexamined by means of a novel approach, the Green's function method augmented by DFT computations. The ferroelectric distortions are shown to be induced by the pseudo Jahn–Teller effect (PJTE). The latter involves vibronic hybridization (admixture) of the ground state to same-spin opposite-parity excited electronic bands. Similar to numerous molecular calculations, the PJT approach provides a deeper insight into the nature of chemical bonding in the octahedral cluster [BO{sub 6}] and, in particular, reveals the local origin of its polar instability. This allows predicting directly which transition ions can create ferroelectricity. In particular, the necessary conditions are established when an ABO{sub 3} perovskite crystal with an electronic d{sup n} configuration of the complex ion [BO{sub 6}] can possess both proper ferroelectric and magnetic properties. Distinguished from the variety of cluster approaches to local properties, the Green's function method includes the influence of the local vibronic-coupling perturbation on the whole crystal via the inter-cell interaction responsible for creation of electronic and vibrational bands. Calculated Green's functions combined with the corresponding numeric estimates for the nine electronic bands, their density of states, and the local adiabatic potential energy surface (APES) confirm the eight-minimum form of this surface and feasibility of the PJT origin of the polar instability in BaTiO{sub 3}. We show also that multicenter long-range dipole–dipole interactions critically depend on the PJTE largely determining the magnitude of the local dipoles. DFT calculations for the bulk crystal and its clusters confirm that the dipolar distortions are of local origin, but become possible only when their influence on (relaxation of) the whole lattice is taken into account. The results are shown to be in full qualitative and

  7. Nonlinear piezoelectricity in epitaxial ferroelectrics at high electric fields.

    Science.gov (United States)

    Grigoriev, Alexei; Sichel, Rebecca; Lee, Ho Nyung; Landahl, Eric C; Adams, Bernhard; Dufresne, Eric M; Evans, Paul G

    2008-01-18

    Nonlinear effects in the coupling of polarization with elastic strain have been predicted to occur in ferroelectric materials subjected to high electric fields. Such predictions are tested here for a PbZr0.2Ti0.8O3 ferroelectric thin film at electric fields in the range of several hundred MV/m and strains reaching up to 2.7%. The piezoelectric strain exceeds predictions based on constant piezoelectric coefficients at electric fields from approximately 200 to 400 MV/m, which is consistent with a nonlinear effect predicted to occur at corresponding piezoelectric distortions.

  8. Observation of domain patterns on a ferroelectric ceramic

    International Nuclear Information System (INIS)

    Ibrahim, R.C.; Zavaglia, C.A.C.

    1992-01-01

    In this work ferroelectric domain patterns are observed on a PZT-like ceramic material produced in Brazil. This material has tetragonal unit cell composing a perovskite type structure. The samples, after grinding and polishing, were chemically etched and observed on optical microscope and scanning electron microscope. (author)

  9. Epitaxial heterojunctions of oxide semiconductors and metals on high temperature superconductors

    Science.gov (United States)

    Vasquez, Richard P. (Inventor); Hunt, Brian D. (Inventor); Foote, Marc C. (Inventor)

    1994-01-01

    Epitaxial heterojunctions formed between high temperature superconductors and metallic or semiconducting oxide barrier layers are provided. Metallic perovskites such as LaTiO3, CaVO3, and SrVO3 are grown on electron-type high temperature superconductors such as Nd(1.85)Ce(0.15)CuO(4-x). Alternatively, transition metal bronzes of the form A(x)MO(3) are epitaxially grown on electron-type high temperature superconductors. Also, semiconducting oxides of perovskite-related crystal structures such as WO3 are grown on either hole-type or electron-type high temperature superconductors.

  10. Process for depositing an oxide epitaxially onto a silicon substrate and structures prepared with the process

    Science.gov (United States)

    McKee, Rodney A.; Walker, Frederick J.

    1993-01-01

    A process and structure involving a silicon substrate utilizes an ultra high vacuum and molecular beam epitaxy (MBE) methods to grow an epitaxial oxide film upon a surface of the substrate. As the film is grown, the lattice of the compound formed at the silicon interface becomes stabilized, and a base layer comprised of an oxide having a sodium chloride-type lattice structure grows epitaxially upon the compound so as to cover the substrate surface. A perovskite may then be grown epitaxially upon the base layer to render a product which incorporates silicon, with its electronic capabilities, with a perovskite having technologically-significant properties of its own.

  11. Structure of epitaxial SrIrO.sub.3./sub. perovskite studied by interference between X-ray waves diffracted by the substrate and the thin film

    Czech Academy of Sciences Publication Activity Database

    Horák, L.; Kriegner, D.; Liu, J.; Frontera, C.; Martí, Xavier; Holý, V.

    2017-01-01

    Roč. 50, Apr (2017), s. 385-398 ISSN 1600-5767 R&D Projects: GA ČR GB14-37427G; GA MŠk(CZ) LG13058 Institutional support: RVO:68378271 Keywords : perovskites * epitaxial layers * X-ray diffraction * interference Subject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.) Impact factor: 2.495, year: 2016

  12. Epitaxial solution deposition of YBa2Cu3O7-6 coated conductors.

    Energy Technology Data Exchange (ETDEWEB)

    Overmyer, Donald L.; Clem, Paul Gilbert; Siegal, Michael P.; Holesinger, Terry A. (Los Alamos National Laboratory, Los Alamos, NM); Voigt, James A.; Richardson, Jacob J.; Dawley, Jeffrey Todd

    2004-11-01

    A variety of solution deposition routes have been reported for processing complex perovskite-based materials such as ferroelectric oxides and conductive electrode oxides, due to ease of incorporating multiple elements, control of chemical stoichiometry, and feasibility for large area deposition. Here, we report an extension of these methods toward long length, epitaxial film solution deposition routes to enable biaxially oriented YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} (YBCO)-coated conductors for superconducting transmission wires. Recent results are presented detailing an all-solution deposition approach to YBCO-coated conductors with critical current densities J{sub c} (77 K) > 1 MA/cm{sup 2} on rolling-assisted, biaxially textured, (200)-oriented Ni-W alloy tapes. Solution-deposition methods such as this approach and those of other research groups appear to have promise to compete with vapor phase methods for superconductor electrical properties, with potential advantages for large area deposition and low cost/kA {center_dot} m of wire.

  13. Characterization Of Graphene-Ferroelectric Superlattice Hybrid Devices

    Science.gov (United States)

    Yusuf, Mohammed; Du, Xu; Dawber, Matthew

    2013-03-01

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

  14. Band gap and mobility of epitaxial perovskite BaSn1 -xHfxO3 thin films

    Science.gov (United States)

    Shin, Juyeon; Lim, Jinyoung; Ha, Taewoo; Kim, Young Mo; Park, Chulkwon; Yu, Jaejun; Kim, Jae Hoon; Char, Kookrin

    2018-02-01

    A wide band-gap perovskite oxide BaSn O3 is attracting much attention due to its high electron mobility and oxygen stability. On the other hand, BaHf O3 was recently reported to be an effective high-k gate oxide. Here, we investigate the band gap and mobility of solid solutions of BaS n1 -xH fxO3 (x =0 -1 ) (BSHO) as a basis to build advanced perovskite oxide heterostructures. All the films were epitaxially grown on MgO substrates using pulsed laser deposition. Density functional theory calculations confirmed that Hf substitution does not create midgap states while increasing the band gap. From x-ray diffraction and optical transmittance measurements, the lattice constants and the band-gap values are significantly modified by Hf substitution. We also measured the transport properties of n -type La-doped BSHO films [(Ba ,La ) (Sn ,Hf ) O3 ] , investigating the feasibility of modulation doping in the BaSn O3/BSHO heterostructures. The Hall measurement data revealed that, as the Hf content increases, the activation rate of the La dopant decreases and the scattering rate of the electrons sharply increases. These properties of BSHO films may be useful for applications in various heterostructures based on the BaSn O3 system.

  15. A hybrid ferroelectric-flash memory cells

    Science.gov (United States)

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

    2014-09-01

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

  16. Research Update: Enhanced energy storage density and energy efficiency of epitaxial Pb0.9La0.1(Zr0.52Ti0.48O3 relaxor-ferroelectric thin-films deposited on silicon by pulsed laser deposition

    Directory of Open Access Journals (Sweden)

    Minh D. Nguyen

    2016-08-01

    Full Text Available Pb0.9La0.1(Zr0.52Ti0.48O3 (PLZT relaxor-ferroelectric thin films were grown on SrRuO3/SrTiO3/Si substrates by pulsed laser deposition. A large recoverable storage density (Ureco of 13.7 J/cm3 together with a high energy efficiency (η of 88.2% under an applied electric field of 1000 kV/cm and at 1 kHz frequency was obtained in 300-nm-thick epitaxial PLZT thin films. These high values are due to the slim and asymmetric hysteresis loop when compared to the values in the reference undoped epitaxial lead zirconate titanate Pb(Zr0.52Ti0.48O3 ferroelectric thin films (Ureco = 9.2 J/cm3 and η = 56.4% which have a high remanent polarization and a small shift in the hysteresis loop, under the same electric field.

  17. Persistent semi-metal-like nature of epitaxial perovskite CaIrO3 thin films

    International Nuclear Information System (INIS)

    Biswas, Abhijit; Jeong, Yoon Hee

    2015-01-01

    Strong spin-orbit coupled 5d transition metal based ABO 3 oxides, especially iridates, allow tuning parameters in the phase diagram and may demonstrate important functionalities, for example, by means of strain effects and symmetry-breaking, because of the interplay between the Coulomb interactions and strong spin-orbit coupling. Here, we have epitaxially stabilized high quality thin films of perovskite (Pv) CaIrO 3 . Film on the best lattice-matched substrate shows semi-metal-like characteristics. Intriguingly, imposing tensile or compressive strain on the film by altering the underlying lattice-mismatched substrates still maintains semi-metallicity with minute modification of the effective correlation as tensile (compressive) strain results in tiny increases (decreases) of the electronic bandwidth. In addition, magnetoresistance remains positive with a quadratic field dependence. This persistent semi-metal-like nature of Pv-CaIrO 3 thin films with minute changes in the effective correlation by strain may provide new wisdom into strong spin-orbit coupled 5d based oxide physics

  18. Ultrahigh piezoelectricity in ferroelectric ceramics by design

    Science.gov (United States)

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

    2018-03-01

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

  19. Perovskite Superlattices as Tunable Microwave Devices

    Science.gov (United States)

    Christen, H. M.; Harshavardhan, K. S.

    2003-01-01

    Experiments have shown that superlattices that comprise alternating epitaxial layers of dissimilar paraelectric perovskites can exhibit large changes in permittivity with the application of electric fields. The superlattices are potentially useful as electrically tunable dielectric components of such microwave devices as filters and phase shifters. The present superlattice approach differs fundamentally from the prior use of homogeneous, isotropic mixtures of base materials and dopants. A superlattice can comprise layers of two or more perovskites in any suitable sequence (e.g., ABAB..., ABCDABCD..., ABACABACA...). Even though a single layer of one of the perovskites by itself is not tunable, the compositions and sequence of the layers can be chosen so that (1) the superlattice exhibits low microwave loss and (2) the interfacial interaction between at least two of the perovskites in the superlattice renders either the entire superlattice or else at least one of the perovskites tunable.

  20. Orientation-dependent physical properties of layered perovskite La{sub 1.3}Sr{sub 1.7}Mn{sub 2}O{sub 7} epitaxial thin films

    Energy Technology Data Exchange (ETDEWEB)

    Niu, Li-Wei; Guo, Bing; Chen, Chang-Le, E-mail: chenchl@nwpu.edu.cn; Luo, Bing-Cheng; Dong, Xiang-Lei; Jin, Ke-Xin

    2017-04-01

    In this paper, the resistivity and magnetization of orientation-engineered layered perovskite La{sub 1.3}Sr{sub 1.7}Mn{sub 2}O{sub 7} epitaxial thin films have been investigated. Epitaxial thin films were deposited on single-crystalline LaAlO{sub 3} (LAO) (001), (110) and (111) substrates by pulse laser deposition (PLD) technique. It is found that only the (100)-oriented thin film performs insulator behavior, whereas the (110) and (111)-oriented thin films exhibit obvious metal-insulator transition at 70 K and between 85 and 120 K, respectively. Moreover, the same spin freezing temperature and different spin-glass-like transition temperatures have been observed in various oriented films. The observed experimental results were discussed according to the electron-transport mechanism and spin dynamics.

  1. Giant electrode effect on tunnelling electroresistance in ferroelectric tunnel junctions.

    Science.gov (United States)

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

    2014-11-17

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

  2. Polarization-coupled tunable resistive behavior in oxide ferroelectric heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Gruverman, Alexei [Univ. of Nebraska, Lincoln, NE (United States); Tsymbal, Evgeny Y. [Univ. of Nebraska, Lincoln, NE (United States); Eom, Chang-Beom [Univ. of Wisconsin, Madison, WI (United States)

    2017-05-03

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

  3. Topotactic reductive synthesis of A-site cation-ordered perovskite YBaCo2O x (x = 4.5-5.5) epitaxial thin films

    Science.gov (United States)

    Katayama, Tsukasa; Chikamatsu, Akira; Fukumura, Tomoteru; Hasegawa, Tetsuya

    2016-04-01

    A-site cation-ordered perovskite YBaCo2O x epitaxial films were synthesized by combining pulsed-laser deposition and topotactic reduction using CaH2. The oxygen contents (x) of the films could be controlled in a range of 4.5-5.5 by adjusting the reaction temperature. The c-axis length of the YBaCo2O x films decreased with decreasing x when x ≥ 5.3 but drastically increased when x ˜ 4.5. In contrast, the in-plane lattice constants remained locked-in by the substrate after the reaction. The metal insulator transition observed in bulk YBaCo2O5.5 was substantially suppressed in the present film, likely because of the epitaxial strain effect. The resistivity of the films was significantly enhanced by changing the x value from ˜5.5 to ˜4.5, reflecting the distortion of the CoO x layers.

  4. Losses in Ferroelectric Materials

    Science.gov (United States)

    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

  5. Losses in Ferroelectric Materials.

    Science.gov (United States)

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

    2015-03-01

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

  6. Nanoscale Ferroelectric Switchable Polarization and Leakage Current Behavior in (Ba0.50Sr0.50(Ti0.80Sn0.20O3 Thin Films Prepared Using Chemical Solution Deposition

    Directory of Open Access Journals (Sweden)

    Venkata Sreenivas Puli

    2015-01-01

    Full Text Available Nanoscale switchable ferroelectric (Ba0.50Sr0.50(Ti0.80Sn0.20O3-BSTS polycrystalline thin films with a perovskite structure were prepared on Pt/TiOx/SiO2/Si substrate by chemical solution deposition. X-ray diffraction (XRD spectra indicate that a cubic perovskite crystalline structure and Raman spectra revealed that a tetragonal perovskite crystalline structure is present in the thin films. Sr2+ and Sn4+ cosubstituted film exhibited the lowest leakage current density. Piezoresponse Force Microscopy (PFM technique has been employed to acquire out-of-plane (OPP piezoresponse images and local piezoelectric hysteresis loop in polycrystalline BSTS films. PFM phase and amplitude images reveal nanoscale ferroelectric switching behavior at room temperature. Square patterns with dark and bright contrasts were written by local poling and reversible nature of the piezoresponse behavior was established. Local piezoelectric butterfly amplitude and phase hysteresis loops display ferroelectric nature at nanoscale level. The significance of this paper is to present ferroelectric/piezoelectric nature in present BSTS films at nanoscale level and corroborating ferroelectric behavior by utilizing Raman spectroscopy. Thus, further optimizing physical and electrical properties, BSTS films might be useful for practical applications which include nonvolatile ferroelectric memories, data-storage media, piezoelectric actuators, and electric energy storage capacitors.

  7. High-Performance Single-Crystalline Perovskite Thin-Film Photodetector

    KAUST Repository

    Yang, Zhenqian; Deng, Yuhao; Zhang, Xiaowei; Wang, Suo; Chen, Huazhou; Yang, Sui; Khurgin, Jacob; Fang, Nicholas X.; Zhang, Xiang; Ma, Renmin

    2018-01-01

    The best performing modern optoelectronic devices rely on single-crystalline thin-film (SC-TF) semiconductors grown epitaxially. The emerging halide perovskites, which can be synthesized via low-cost solution-based methods, have achieved substantial

  8. Visible light carrier generation in co-doped epitaxial titanate films

    Energy Technology Data Exchange (ETDEWEB)

    Comes, Ryan B., E-mail: ryan.comes@pnnl.gov; Kaspar, Tiffany C.; Chambers, Scott A. [Fundamental and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, Washington 99354 (United States); Smolin, Sergey Y.; Baxter, Jason B. [Department of Chemical and Biological Engineering, Drexel University, Philadelphia, Pennsylvania 19104 (United States); Gao, Ran [Department of Materials Science and Engineering, University of California-Berkeley, Berkeley, California 94720 (United States); Apgar, Brent A. [Department of Materials Science and Engineering, University of California-Berkeley, Berkeley, California 94720 (United States); Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Champaign, Illinois 61801 (United States); Martin, Lane W. [Department of Materials Science and Engineering, University of California-Berkeley, Berkeley, California 94720 (United States); Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Bowden, Mark E. [Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, Washington 99354 (United States)

    2015-03-02

    Perovskite titanates such as SrTiO{sub 3} (STO) exhibit a wide range of important functional properties, including ferroelectricity and excellent photocatalytic performance. The wide optical band gap of titanates limits their use in these applications; however, making them ill-suited for integration into solar energy harvesting technologies. Our recent work has shown that by doping STO with equal concentrations of La and Cr, we can enhance visible light absorption in epitaxial thin films while avoiding any compensating defects. In this work, we explore the optical properties of photoexcited carriers in these films. Using spectroscopic ellipsometry, we show that the Cr{sup 3+} dopants, which produce electronic states immediately above the top of the O 2p valence band in STO reduce the direct band gap of the material from 3.75 eV to 2.4–2.7 eV depending on doping levels. Transient reflectance spectroscopy measurements are in agreement with the observations from ellipsometry and confirm that optically generated carriers are present for longer than 2 ns. Finally, through photoelectrochemical methylene blue degradation measurements, we show that these co-doped films exhibit enhanced visible light photocatalysis when compared to pure STO.

  9. Epitaxial phase diagrams of SrTiO3, CaTiO3, and SrHfO3: Computational investigation including the role of antiferrodistortive and A -site displacement modes

    Science.gov (United States)

    Angsten, Thomas; Asta, Mark

    2018-04-01

    Ground-state epitaxial phase diagrams are calculated by density functional theory (DFT) for SrTiO3, CaTiO3, and SrHfO3 perovskite-based compounds, accounting for the effects of antiferrodistortive and A -site displacement modes. Biaxial strain states corresponding to epitaxial growth of (001)-oriented films are considered, with misfit strains ranging between -4 % and 4%. Ground-state structures are determined using a computational procedure in which input structures for DFT optimizations are identified as local minima in expansions of the total energy with respect to strain and soft-mode degrees of freedom. Comparison to results of previous DFT studies demonstrates the effectiveness of the computational approach in predicting ground-state phases. The calculated results show that antiferrodistortive octahedral rotations and associated A -site displacement modes act to suppress polarization and reduce the epitaxial strain energy. A projection of calculated atomic displacements in the ground-state epitaxial structures onto soft-mode eigenvectors shows that three ferroelectric and six antiferrodistortive displacement modes are dominant at all misfit strains considered, with the relative contributions from each varying systematically with the strain. Additional A -site displacement modes contribute to the atomic displacements in CaTiO3 and SrHfO3, which serve to optimize the coordination of the undersized A -site cation.

  10. Persistent semi-metal-like nature of epitaxial perovskite CaIrO{sub 3} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Biswas, Abhijit; Jeong, Yoon Hee, E-mail: yhj@postech.ac.kr [Department of Physics, POSTECH, Pohang 790-784 (Korea, Republic of)

    2015-05-21

    Strong spin-orbit coupled 5d transition metal based ABO{sub 3} oxides, especially iridates, allow tuning parameters in the phase diagram and may demonstrate important functionalities, for example, by means of strain effects and symmetry-breaking, because of the interplay between the Coulomb interactions and strong spin-orbit coupling. Here, we have epitaxially stabilized high quality thin films of perovskite (Pv) CaIrO{sub 3}. Film on the best lattice-matched substrate shows semi-metal-like characteristics. Intriguingly, imposing tensile or compressive strain on the film by altering the underlying lattice-mismatched substrates still maintains semi-metallicity with minute modification of the effective correlation as tensile (compressive) strain results in tiny increases (decreases) of the electronic bandwidth. In addition, magnetoresistance remains positive with a quadratic field dependence. This persistent semi-metal-like nature of Pv-CaIrO{sub 3} thin films with minute changes in the effective correlation by strain may provide new wisdom into strong spin-orbit coupled 5d based oxide physics.

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

    Science.gov (United States)

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

    2015-08-26

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

  12. Raman analysis of ferroelectric switching in niobium-doped lead zirconate titanate thin films

    International Nuclear Information System (INIS)

    Ferrari, P.; Ramos-Moore, E.; Guitar, M.A.; Cabrera, A.L.

    2014-01-01

    Characteristic Raman vibration modes of niobium-doped lead zirconate titanate (PNZT) are studied as a function of ferroelectric domain switching. The microstructure of PNZT is characterized by scanning electron microscopy and X-ray diffraction. Ferroelectric switching is achieved by applying voltages between the top (Au) and bottom (Pt) electrodes, while acquiring the Raman spectra in situ. Vibrational active modes associated with paraelectric and ferroelectric phases are identified after measuring above and below the ferroelectric Curie temperature, respectively. Changes in the relative intensities of the Raman peaks are observed as a function of the switching voltage. The peak area associated with the ferroelectric modes is analyzed as a function of the applied voltage within one ferroelectric polarization loop, showing local maxima around the coercive voltage. This behavior can be understood in terms of the correlation between vibrational and structural properties, since ferroelectric switching modifies the interaction between the body-centered atom (Zr, Ti or Nb) and the Pb–O lattice. - Highlights: • Electric fields induce structural distortions on ferroelectric perovskites. • Ferroelectric capacitor was fabricated to perform hysteresis loops. • Raman analysis was performed in situ during ferroelectric switching. • Raman modes show hysteresis and inflections around the coercive voltages. • Data can be understood in terms of vibrational–structural correlations

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

    Science.gov (United States)

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

    2018-04-01

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

  14. Designing pseudocubic perovskites with enhanced nanoscale polarization

    Energy Technology Data Exchange (ETDEWEB)

    Levin, I. [Materials Measurement Science Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA; Laws, W. J. [Materials Measurement Science Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA; Wang, D. [Department of Materials Engineering, University of Sheffield, Sheffield S1 3JD, United Kingdom; Reaney, I. M. [Department of Materials Engineering, University of Sheffield, Sheffield S1 3JD, United Kingdom

    2017-11-20

    A crystal-chemical framework has been proposed for the design of pseudocubic perovskites with nanoscale ferroelectric order, and its applicability has been demonstrated using a series of representative solid solutions that combined ferroelectric (K0.5Bi0.5TiO3, BaTiO3, and PbTiO3) and antiferroelectric (Nd-substituted BiFeO3) end members. The pseudocubic structures obtained in these systems exhibited distortions that were coherent on a scale ranging from sub-nanometer to tens of nanometers, but, in all cases, the macroscopic distortion remained unresolvable even if using high-resolution X-ray powder diffraction. Different coherence lengths for the local atomic displacements account for the distinctly different dielectric, ferroelectric, and electromechanical properties exhibited by the samples. The guidelines identified provide a rationale for chemically tuning the coherence length to obtain the desired functional response.

  15. High-mobility BaSnO{sub 3} grown by oxide molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Raghavan, Santosh; Schumann, Timo; Kim, Honggyu; Zhang, Jack Y.; Cain, Tyler A.; Stemmer, Susanne, E-mail: stemmer@mrl.ucsb.edu [Materials Department, University of California, Santa Barbara, California 93106-5050 (United States)

    2016-01-01

    High-mobility perovskite BaSnO{sub 3} films are of significant interest as new wide bandgap semiconductors for power electronics, transparent conductors, and as high mobility channels for epitaxial integration with functional perovskites. Despite promising results for single crystals, high-mobility BaSnO{sub 3} films have been challenging to grow. Here, we demonstrate a modified oxide molecular beam epitaxy (MBE) approach, which supplies pre-oxidized SnO{sub x}. This technique addresses issues in the MBE of ternary stannates related to volatile SnO formation and enables growth of epitaxial, stoichiometric BaSnO{sub 3}. We demonstrate room temperature electron mobilities of 150 cm{sup 2} V{sup −1} s{sup −1} in films grown on PrScO{sub 3}. The results open up a wide range of opportunities for future electronic devices.

  16. Deposition and characterisation of epitaxial oxide thin films for SOFCs

    KAUST Repository

    Santiso, José

    2010-10-24

    This paper reviews the recent advances in the use of thin films, mostly epitaxial, for fundamental studies of materials for solid oxide fuel cell (SOFC) applications. These studies include the influence of film microstructure, crystal orientation and strain in oxide ionic conducting materials used as electrolytes, such as fluorites, and in mixed ionic and electronic conducting materials used as electrodes, typically oxides with perovskite or perovskite-related layered structures. The recent effort towards the enhancement of the electrochemical performance of SOFC materials through the deposition of artificial film heterostructures is also presented. These thin films have been engineered at a nanoscale level, such as the case of epitaxial multilayers or nanocomposite cermet materials. The recent progress in the implementation of thin films in SOFC devices is also reported. © 2010 Springer-Verlag.

  17. Two-Photon Absorption in Organometallic Bromide Perovskites

    KAUST Repository

    Walters, Grant

    2015-07-21

    Organometallic trihalide perovskites are solution processed semiconductors that have made great strides in third generation thin film light harvesting and light emitting optoelectronic devices. Recently it has been demonstrated that large, high purity single crystals of these perovskites can be synthesized from the solution phase. These crystals’ large dimensions, clean bandgap, and solid-state order, have provided us with a suitable medium to observe and quantify two-photon absorption in perovskites. When CH3NH3PbBr3 single crystals are pumped with intense 800 nm light, we observe band-to-band photoluminescence at 572 nm, indicative of two-photon absorption. We report the nonlinear absorption coefficient of CH3NH3PbBr3 perovskites to be 8.6 cm GW-1 at 800 nm, comparable to epitaxial single crystal semiconductors of similar bandgap. We have leveraged this nonlinear process to electrically autocorrelate a 100 fs pulsed laser using a two-photon perovskite photodetector. This work demonstrates the viability of organometallic trihalide perovskites as a convenient and low-cost nonlinear absorber for applications in ultrafast photonics.

  18. Two-Photon Absorption in Organometallic Bromide Perovskites

    KAUST Repository

    Walters, Grant; Sutherland, Brandon R; Hoogland, Sjoerd; Shi, Dong; Comin, Riccardo; Sellan, Daniel P.; Bakr, Osman; Sargent, Edward H.

    2015-01-01

    Organometallic trihalide perovskites are solution processed semiconductors that have made great strides in third generation thin film light harvesting and light emitting optoelectronic devices. Recently it has been demonstrated that large, high purity single crystals of these perovskites can be synthesized from the solution phase. These crystals’ large dimensions, clean bandgap, and solid-state order, have provided us with a suitable medium to observe and quantify two-photon absorption in perovskites. When CH3NH3PbBr3 single crystals are pumped with intense 800 nm light, we observe band-to-band photoluminescence at 572 nm, indicative of two-photon absorption. We report the nonlinear absorption coefficient of CH3NH3PbBr3 perovskites to be 8.6 cm GW-1 at 800 nm, comparable to epitaxial single crystal semiconductors of similar bandgap. We have leveraged this nonlinear process to electrically autocorrelate a 100 fs pulsed laser using a two-photon perovskite photodetector. This work demonstrates the viability of organometallic trihalide perovskites as a convenient and low-cost nonlinear absorber for applications in ultrafast photonics.

  19. Density functional theory computational study of ferroelectricity and piezoelectricity in BaTiO3/PbTiO3 (0 1 1) superlattices

    Science.gov (United States)

    Lou, Yaoding; Deng, Junkai; Zhe Liu, Jefferson

    2018-04-01

    The structure, ferroelectricity (FE), and piezoelectricity of epitaxial BaTiO3/PbTiO3 (BTO/PTO) (0 1 1) superlattices are studied using density functional theory calculations. Our results show that compressive strain arising from the SrTiO3 (0 1 1) substrate stabilizes the (BTO) m /(PTO) n (0 1 1) superlattices in orthorhombic phase with the FE polarization along [0 1 1] direction. Tuning the BTO contents significantly changes the structural, ferroelectric and piezoelectric properties. The FE polarization of superlattices significantly drops with increasing BTO contents, which can be attributed to depolarization of the PTO layers. The averaged c/a ratio of the whole superlattices exhibits anomalous non-monotonic relation with respect to BTO contents. Interestingly, our results predict the (0 1 1) superlattices can enhance the piezoelectric coefficient e 33 with a maximum value at ~67% BTO concentration. This result suggests a potential avenue to design high performance piezoelectric materials with less Pb contents. In-depth analysis reveals the B-site Ti cation as the origin for the enhanced e 33 value, which implies the potential of B-site cation engineering in perovskite heterostructure designs.

  20. Research Update: Physical and electrical characteristics of lead halide perovskites for solar cell applications

    Directory of Open Access Journals (Sweden)

    Simon A. Bretschneider

    2014-04-01

    Full Text Available The field of thin-film photovoltaics has been recently enriched by the introduction of lead halide perovskites as absorber materials, which allow low-cost synthesis of solar cells with efficiencies exceeding 16%. The exact impact of the perovskite crystal structure and composition on the optoelectronic properties of the material are not fully understood. Our progress report highlights the knowledge gained about lead halide perovskites with a focus on physical and optoelectronic properties. We discuss the crystal and band structure of perovskite materials currently implemented in solar cells and the impact of the crystal properties on ferroelectricity, ambipolarity, and the properties of excitons.

  1. Ferroelectrics under the Synchrotron Light: A Review

    Directory of Open Access Journals (Sweden)

    Luis E. Fuentes-Cobas

    2015-12-01

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

  2. Ferroelectrics under the Synchrotron Light: A Review

    Science.gov (United States)

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

    2015-01-01

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

  3. Absence of strain-mediated magnetoelectric coupling at fully epitaxial Fe/BaTiO3 interface (invited)

    International Nuclear Information System (INIS)

    Radaelli, G.; Petti, D.; Cantoni, M.; Rinaldi, C.; Bertacco, R.

    2014-01-01

    Interfacial MagnetoElectric coupling (MEC) at ferroelectric/ferromagnetic interfaces has recently emerged as a promising route to achieve electrical writing of magnetic information in spintronic devices. For the prototypical Fe/BaTiO 3 (BTO) system, various MEC mechanisms have been theoretically predicted. Experimentally, it is well established that using BTO single crystal substrates MEC is dominated by strain-mediated mechanisms. In case of ferromagnetic layers epitaxially grown onto BTO films, instead, no direct evidence for MEC has been provided, apart from the results obtained on tunneling junction sandwiching a BTO tunneling barrier. In this paper, MEC at fully epitaxial Fe/BTO interface is investigated by Magneto-Optical Kerr Effect and magnetoresistance measurements on magnetic tunnel junctions fabricated on BTO. We find no evidence for strain-mediated MEC mechanisms in epitaxial systems, likely due to clamping of BTO to the substrate. Our results indicate that pure electronic MEC is the route of choice to be explored for achieving the electrical writing of information in epitaxial ferromagnet-ferroelectric heterostructures

  4. Complex Electric-Field Induced Phenomena in Ferroelectric/Antiferroelectric Nanowires

    Science.gov (United States)

    Herchig, Ryan Christopher

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

  5. Process for growing a film epitaxially upon an oxide surface and structures formed with the process

    Science.gov (United States)

    McKee, Rodney A.; Walker, Frederick J.

    1995-01-01

    A process and structure wherein a film comprised of a perovskite or a spinel is built epitaxially upon a surface, such as an alkaline earth oxide surface, involves the epitaxial build up of alternating constituent metal oxide planes of the perovskite or spinel. The first layer of metal oxide built upon the surface includes a metal element which provides a small cation in the crystalline structure of the perovskite or spinel, and the second layer of metal oxide built upon the surface includes a metal element which provides a large cation in the crystalline structure of the perovskite or spinel. The layering sequence involved in the film build up reduces problems which would otherwise result from the interfacial electrostatics at the first atomic layers, and these oxides can be stabilized as commensurate thin films at a unit cell thickness or grown with high crystal quality to thicknesses of 0.5-0.7 .mu.m for optical device applications.

  6. Strain tunable ferroelectric and dielectric properties of BaZrO3

    International Nuclear Information System (INIS)

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

    2014-01-01

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

  7. X-ray diffraction stress analysis of ferroelectric thin films with ideal (h k l) textures considering the piezoelectric coupling effect

    International Nuclear Information System (INIS)

    Wu Huaping; Wu Linzhi; Li Jiquan; Chai Guozhong; Du Shanyi

    2010-01-01

    Ferroelectric thin films present large residual stress and strong texture during preparation, which affect the mechanical, dielectric and piezoelectric properties of the thin films. The determination of residual stresses in ferroelectric thin films with different textures is therefore very important. In this paper, an extended crystallite group model to evaluate the residual stresses of ferroelectric thin films using X-ray diffraction is proposed by considering the constitutive equation of orthogonally anisotropic ferroelectric medium. The effects of anisotropy and piezoelectric coupling on residual stresses of ferroelectric thin films are analyzed. X-ray stress factors for ideal (h k l)-textured ferroelectric thin films are obtained. An example of calculating the residual stresses of tetragonal perovskite ferroelectric thin films with (1 1 1) and (1 0 0) textures using the extended model is provided to validate the model.

  8. Absence of strain-mediated magnetoelectric coupling at fully epitaxial Fe/BaTiO{sub 3} interface (invited)

    Energy Technology Data Exchange (ETDEWEB)

    Radaelli, G., E-mail: greta.radaelli@gmail.com; Petti, D.; Cantoni, M.; Rinaldi, C.; Bertacco, R. [LNESS Center - Dipartimento di Fisica del Politecnico di Milano, Como 22100 (Italy)

    2014-05-07

    Interfacial MagnetoElectric coupling (MEC) at ferroelectric/ferromagnetic interfaces has recently emerged as a promising route to achieve electrical writing of magnetic information in spintronic devices. For the prototypical Fe/BaTiO{sub 3} (BTO) system, various MEC mechanisms have been theoretically predicted. Experimentally, it is well established that using BTO single crystal substrates MEC is dominated by strain-mediated mechanisms. In case of ferromagnetic layers epitaxially grown onto BTO films, instead, no direct evidence for MEC has been provided, apart from the results obtained on tunneling junction sandwiching a BTO tunneling barrier. In this paper, MEC at fully epitaxial Fe/BTO interface is investigated by Magneto-Optical Kerr Effect and magnetoresistance measurements on magnetic tunnel junctions fabricated on BTO. We find no evidence for strain-mediated MEC mechanisms in epitaxial systems, likely due to clamping of BTO to the substrate. Our results indicate that pure electronic MEC is the route of choice to be explored for achieving the electrical writing of information in epitaxial ferromagnet-ferroelectric heterostructures.

  9. Critical Intermediate Structure That Directs the Crystalline Texture and Surface Morphology of Organo-Lead Trihalide Perovskite.

    Science.gov (United States)

    Chia, Hao-Chung; Sheu, Hwo-Shuenn; Hsiao, Yu-Yun; Li, Shao-Sian; Lan, Yi-Kang; Lin, Chung-Yao; Chang, Je-Wei; Kuo, Yen-Chien; Chen, Chia-Hao; Weng, Shih-Chang; Su, Chun-Jen; Su, An-Chung; Chen, Chun-Wei; Jeng, U-Ser

    2017-10-25

    We have identified an often observed yet unresolved intermediate structure in a popular processing with dimethylformamide solutions of lead chloride and methylammonium iodide for perovskite solar cells. With subsecond time-resolved grazing-incidence X-ray scattering and X-ray photoemission spectroscopy, supplemental with ab initio calculation, the resolved intermediate structure (CH 3 NH 3 ) 2 PbI 2 Cl 2 ·CH 3 NH 3 I features two-dimensional (2D) perovskite bilayers of zigzagged lead-halide octahedra and sandwiched CH 3 NH 3 I layers. Such intermediate structure reveals a hidden correlation between the intermediate phase and the composition of the processing solution. Most importantly, the 2D perovskite lattice of the intermediate phase is largely crystallographically aligned with the [110] planes of the three-dimensional perovskite cubic phase; consequently, with sublimation of Cl ions from the organo-lead octahedral terminal corners in prolonged annealing, the zigzagged octahedral layers of the intermediate phase can merge with the intercalated methylammonium iodide layers for templated growth of perovskite crystals. Regulated by annealing temperature and the activation energies of the intermediate and perovskite, deduced from analysis of temperature-dependent structural kinetics, the intermediate phase is found to selectively mature first and then melt along the layering direction for epitaxial conversion into perovskite crystals. The unveiled epitaxial conversion under growth kinetics controls might be general for solution-processed and intermediate-templated perovskite formation.

  10. In situ transmission electron microscopy study of the microstructural origins for the electric field-induced phenomena in ferroelectric perovskites

    Science.gov (United States)

    Guo, Hanzheng

    Ferroelectrics are important materials due to their extensive technological applications, such as non-volatile memories, field-effect transistors, ferroelectric tunneling junctions, dielectric capacitors, piezoelectric transducers, sensors and actuators. As is well known, the outstanding dielectric, piezoelectric, and ferroelectric properties of these functional oxides originate from their ferroelectric domain arrangements and the corresponding evolution under external stimuli (e.g. electric field, stress, and temperature). Electric field has been known as the most efficient stimulus to manipulate the ferroelectric domains through polarization switching and alignment. Therefore, direct observation of the dynamic process of electric field-induced domain evolution and crystal structure transformation is of significant importance to understand the microstructural mechanisms for the functional properties of ferroelectrics. In this dissertation, electric field in situ transmission electron microscopy (TEM) technique was employed to monitor the real-time evolution of the domain morphology and crystal structure during various electrical processes: (1) the initial poling process, (2) the electric field reversal process, and (3) the electrical cycling process. Two types of perovskite-structured ceramics, normal ferroelectrics and relaxor ferroelectrics, were used for this investigation. In addition to providing the microscopic insight for some well-accepted phase transformation rules, discoveries of some new or even unexpected physical phenomena were also demonstrated. For the initial poling process, microstructural origins for the piezoelectricity development in the three most promising lead-free piezoceramic systems were investigated. For the non-ergodic relaxor ferroelectric compositions ( x = 6% - 9%) in the (1-x)(Bi1/2Na 1/2)TiO3-xBaTiO3 system, well-developed piezoelectricity was realized at poling fields far below the coercive field and phase transition field. Such

  11. Ferroelectric and electrical characterization of multiferroic BiFeO3 at the single nanoparticle level

    Energy Technology Data Exchange (ETDEWEB)

    Vasudevan, Rama K [ORNL; Bogle, K A [University of New South Wales, Sydney, Australia; Kumar, Amit [ORNL; Jesse, Stephen [ORNL; Magaraggia, R [University of Glasgow; Stamps, R [University of Glasgow; Ogale, S [National Chemical Laboratory, India; Potdar, H S [National Chemical Laboratory, India

    2011-01-01

    Ferroelectric BiFeO3 (BFO) nanoparticles deposited on epitaxial substrates of SrRuO3 (SRO) and La1xSrxMnO3 (LSMO) were studied using band excitation piezoresponse spectroscopy (BEPS), piezoresponse force microscopy (PFM), and ferromagnetic resonance (FMR). BEPS confirms that the nanoparticles are ferroelectric in nature. Switching behavior of nanoparticle clusters were studied and showed evidence for inhomogeneous switching. The dimensionality of domains within nanoparticles was found to be fractal in nature, with a dimensionality constant of 1.4, on par with ferroelectric BFO thin-films under 100 nm in thickness. Ferromagnetic resonance studies indicate BFO nanoparticles only weakly affect the magnetic response of LSMO.

  12. Ferroelectric and electrical characterization of multiferroic BiFeO3 at the single nanoparticle level

    Science.gov (United States)

    Vasudevan, R. K.; Bogle, K. A.; Kumar, A.; Jesse, S.; Magaraggia, R.; Stamps, R.; Ogale, S. B.; Potdar, H. S.; Nagarajan, V.

    2011-12-01

    Ferroelectric BiFeO3 (BFO) nanoparticles deposited on epitaxial substrates of SrRuO3 (SRO) and La1-xSrxMnO3 (LSMO) were studied using band excitation piezoresponse spectroscopy (BEPS), piezoresponse force microscopy (PFM), and ferromagnetic resonance (FMR). BEPS confirms that the nanoparticles are ferroelectric in nature. Switching behavior of nanoparticle clusters were studied and showed evidence for inhomogeneous switching. The dimensionality of domains within nanoparticles was found to be fractal in nature, with a dimensionality constant of ˜1.4, on par with ferroelectric BFO thin-films under 100 nm in thickness. Ferromagnetic resonance studies indicate BFO nanoparticles only weakly affect the magnetic response of LSMO.

  13. A-site driven ferroelectricity in K0.5Li0.5NbO3

    Science.gov (United States)

    Bilc, Daniel I.; Singh, D. J.

    2006-03-01

    Mixed A-site ferroelectric materials have gained recent attention. Here we report density functional calculations of KxLi1-xNbO3 perovskite supercells in order to understand the interplay between various lattice instabilities with size mismatch on the A-site and the role of the A and B site ions in this case. The calculations were done using the general potential LAPW method. For x=0.5, we find a ferroelectric ground state, even though the average tolerance factor is significantly smaller than unity and there is no stereochemically active A site ion. This is due to frustration due to the very different ionic radii of K and Li. We find very large off-centering of the Li ions, which distinguishes this compound. Relative to this the Nb off-centering is quite small. This is in contrast to most perovskite ferroelectrics where there is significant off-centering of all ions, and resulting cooperativity. Also because of the large Li off-centering it contributes strongly to the anisotropy between tetragonal and rhombohedral ground states, yielding a tetragonal ground state. Normally the anisotropy is determined by the interplay of B site off-centering and strain coupling. This work was supported by the Office of Naval Research and the Department of Energy.

  14. Topotactic synthesis of strontium cobalt oxyhydride thin film with perovskite structure

    Science.gov (United States)

    Katayama, Tsukasa; Chikamatsu, Akira; Kamisaka, Hideyuki; Yokoyama, Yuichi; Hirata, Yasuyuki; Wadati, Hiroki; Fukumura, Tomoteru; Hasegawa, Tetsuya

    2015-10-01

    The substitution of hydride anions (H-) into transition metal oxides has recently become possible through topotactic reactions or high-pressure synthesis methods. However, the fabrication of oxyhydrides is still difficult because of their inherently less-stable frameworks. In this study, we successfully fabricated perovskite SrCoOxHy thin films via the topotactic hydride doping of brownmillerite SrCoO2.5 epitaxial thin films with CaH2. The perovskite-type cation framework was maintained during the topotactic treatment owing to epitaxial stabilization. Structural and chemical analyses accompanied by X-ray absorption spectroscopy measurements revealed that the doped hydride ions form a two-dimensional network of Co-H--Co bonds, in contrast to other reported perovskite oxyhydrides, SrMO3-xHx (M = Cr, Ti, V). The SrCoOxHy thin film exhibited insulating behavior and had a direct band gap of 2.1 eV. Thus, topotactic hydride doping of transition-metal-oxide thin films on suitable substrates is a promising method for the synthesis of new transition metal oxyhydrides.

  15. Topotactic synthesis of strontium cobalt oxyhydride thin film with perovskite structure

    Directory of Open Access Journals (Sweden)

    Tsukasa Katayama

    2015-10-01

    Full Text Available The substitution of hydride anions (H− into transition metal oxides has recently become possible through topotactic reactions or high-pressure synthesis methods. However, the fabrication of oxyhydrides is still difficult because of their inherently less-stable frameworks. In this study, we successfully fabricated perovskite SrCoOxHy thin films via the topotactic hydride doping of brownmillerite SrCoO2.5 epitaxial thin films with CaH2. The perovskite-type cation framework was maintained during the topotactic treatment owing to epitaxial stabilization. Structural and chemical analyses accompanied by X-ray absorption spectroscopy measurements revealed that the doped hydride ions form a two-dimensional network of Co-H−-Co bonds, in contrast to other reported perovskite oxyhydrides, SrMO3−xHx (M = Cr, Ti, V. The SrCoOxHy thin film exhibited insulating behavior and had a direct band gap of 2.1 eV. Thus, topotactic hydride doping of transition-metal-oxide thin films on suitable substrates is a promising method for the synthesis of new transition metal oxyhydrides.

  16. A review on all-perovskite multiferroic tunnel junctions

    Directory of Open Access Journals (Sweden)

    Yuewei Yin

    2017-12-01

    Full Text Available Although the basic concept was proposed only about 10 years ago, multiferroic tunnel junctions (MFTJs with a ferroelectric barrier sandwiched between two ferromagnetic electrodes have already drawn considerable interests, driven mainly by its potential applications in multi-level memories and electric field controlled spintronics. The purpose of this article is to review the recent progress of all-perovskite MFTJs. Starting from the key functional properties of the tunneling magnetoresistance, tunneling electroresistance, and tunneling electromagnetoresistance effects, we discuss the main origins of the tunneling electroresistance effect, recent progress in achieving multilevel resistance states in a single device, and the electrical control of spin polarization and transport through the ferroelectric polarization reversal of the tunneling barrier.

  17. Tilts, dopants, vacancies and non-stoichiometry: Understanding and designing the properties of complex solid oxide perovskites from first principles

    Science.gov (United States)

    Bennett, Joseph W.

    Perovskite oxides of formula ABO3 have a wide range of structural, electrical and mechanical properties, making them vital materials for many applications, such as catalysis, ultrasound machines and communication devices. Perovskite solid solutions with high piezoelectric response, such as ferroelectrics, are of particular interest as they can be employed as sensors in SONAR devices. Ferroelectric materials are unique in that their chemical and electrical properties can be non-invasively and reversibly changed, by switching the bulk polarization. This makes ferroelectrics useful for applications in non-volatile random access memory (NVRAM) devices. Perovskite solid solutions with a lower piezoelectric response than ferroelectrics are important for communication technology, as they function well as electroceramic capacitors. Also of interest is how these materials act as a component in a solid oxide fuel cell, as they can function as an efficient source of energy. Altering the chemical composition of these solid oxide materials offers an opportunity to change the desired properties of the final ceramic, adding a degree of flexibility that is advantageous for a variety of applications. These solid oxides are complex, sometimes disordered systems that are a challenge to study experimentally. However, as it is their complexity which produces favorable properties, highly accurate modeling which captures the essential features of the disordered structure is necessary to explain the behavior of current materials and predict favorable compositions for new materials. Methodological improvements and faster computer speeds have made first-principles and atomistic calculations a viable tool for understanding these complex systems. Offering a combination of accuracy and computational speed, the density functional theory (DFT) approach can reveal details about the microscopic structure and interactions of complex systems. Using DFT and a combination of principles from both

  18. Electron molecular beam epitaxy: Layer-by-layer growth of complex oxides via pulsed electron-beam deposition

    International Nuclear Information System (INIS)

    Comes, Ryan; Liu Hongxue; Lu Jiwei; Gu, Man; Khokhlov, Mikhail; Wolf, Stuart A.

    2013-01-01

    Complex oxide epitaxial film growth is a rich and exciting field, owing to the wide variety of physical properties present in oxides. These properties include ferroelectricity, ferromagnetism, spin-polarization, and a variety of other correlated phenomena. Traditionally, high quality epitaxial oxide films have been grown via oxide molecular beam epitaxy or pulsed laser deposition. Here, we present the growth of high quality epitaxial films using an alternative approach, the pulsed electron-beam deposition technique. We demonstrate all three epitaxial growth modes in different oxide systems: Frank-van der Merwe (layer-by-layer); Stranski-Krastanov (layer-then-island); and Volmer-Weber (island). Analysis of film quality and morphology is presented and techniques to optimize the morphology of films are discussed.

  19. Nanoscale ferroelectrics and multiferroics key processes and characterization issues, and nanoscale effects

    CERN Document Server

    Alguero, Miguel

    2016-01-01

    This book reviews the key issues in processing and characterization of nanoscale ferroelectrics and multiferroics, and provides a comprehensive description of their properties, with an emphasis in differentiating size effects of extrinsic ones like boundary or interface effects. Recently described nanoscale novel phenomena are also addressed. Organized into three parts it addresses key issues in processing (nanostructuring), characterization (of the nanostructured materials) and nanoscale effects. Taking full advantage of the synergies between nanoscale ferroelectrics and multiferroics, it covers materials nanostructured at all levels, from ceramic technologies like ferroelectric nanopowders, bulk nanostructured ceramics and thick films, and magnetoelectric nanocomposites, to thin films, either polycrystalline layer heterostructures or epitaxial systems, and to nanoscale free standing objects with specific geometries, such as nanowires and tubes at different levels of development. The book is developed from t...

  20. Polarized Raman scattering study of PSN single crystals and epitaxial thin films

    Czech Academy of Sciences Publication Activity Database

    Pokorný, Jan; Rafalovskyi, Iegor; Gregora, Ivan; Borodavka, Fedir; Savinov, Maxim; Drahokoupil, Jan; Tyunina, Marina; Kocourek, Tomáš; Jelínek, Miroslav; Bing, Y.; Ye, Z. -G.; Hlinka, Jiří

    2015-01-01

    Roč. 5, č. 2 (2015), "1550013-1"-"1550013-6" ISSN 2010-135X R&D Projects: GA ČR GA15-04121S; GA ČR GA15-15123S Institutional support: RVO:68378271 Keywords : PSN * relaxors * ferroelectrics * complex perovskites * Raman scattering Subject RIV: BM - Solid Matter Physics ; Magnetism

  1. Large isosymmetric reorientation of oxygen octahedra rotation axes in epitaxially strained perovskites.

    Science.gov (United States)

    Rondinelli, James M; Coh, Sinisa

    2011-06-10

    Using first-principles density functional theory calculations, we discover an anomalously large biaxial strain-induced octahedral rotation axis reorientation in orthorhombic perovskites with tendency towards rhombohedral symmetry. The transition between crystallographically equivalent (isosymmetric) structures with different octahedral rotation magnitudes originates from strong strain-octahedral rotation coupling available to perovskites and the energetic hierarchy among competing octahedral tilt patterns. By elucidating these criteria, we suggest many functional perovskites would exhibit the transition in thin film form, thus offering a new landscape in which to tailor highly anisotropic electronic responses.

  2. Ferroelectricity down to at least 2 nm in multiferroic BiFeO3 epitaxial thin films

    International Nuclear Information System (INIS)

    Bea, H.; Fusil, S.; Bouzehouane, K.; Sirena, M.; Herranz, G.; Jacquet, E.; Contour, J.-P.; Barthelemy, A.; Bibes, M.

    2006-01-01

    We report here on the preservation of ferroelectricity down to 2 nm in BiFeO 3 ultrathin films. The electric polarization can be switched reversibly and is stable over several days. Our findings insight on the fundamental problem of ferroelectricity at low thickness and confirm the potential of BiFeO 3 as a lead-free ferroelectric and multiferroic material for nanoscale devices. (author)

  3. High T(sub c) superconductor/ferroelectric heterostructures

    Science.gov (United States)

    Ryder, Daniel F., Jr.

    1994-12-01

    Thin films of the ferroelectric perovskite, Ba(x) Sr(1-x) TiO3 (BST), were deposited on superconducting (100)YBa2Cu3O(x)(YBCO)/ (100)Yttria-stabilized zirconia(YSZ) substrates and (100)Si by ion-beam sputtering. Microstructural and compositional features of the ceramic bilayer were assessed by a combination of x-ray diffraction (XRD) and scanning electron microscopy. The films were smooth and featureless, and energy dispersive x-ray spectroscopy (EDX) data indicated that film composition closely matched target composition. XRD analysis showed that films deposited on YBCO substrates were highly c-axis textured, while the films deposited on (100)Si did not exhibit any preferred growth morphology. The superconducting properties of the YBCO substrate layer were maintained throughout the processing stages and, as such, it was demonstrated that ion beam sputtering is a viable method for the deposition of Ferroelectric/YBCO heterostructures.

  4. Programmable ferroelectric tunnel memristor

    Directory of Open Access Journals (Sweden)

    Andy eQuindeau

    2014-02-01

    Full Text Available We report an analogously programmable memristor based on genuine electronic resistive switching combining ferroelectric switching and electron tunneling. The tunnel current through an 8 unit cell thick epitaxial Pb(Zr[0.2]Ti[0.8]O[3] film sandwiched between La[0.7]Sr[0.3]MnO[3] and cobalt electrodes obeys the Kolmogorov-Avrami-Ishibashi model for bidimensional growth with a characteristic switching time in the order of 10^-7 seconds. The analytical description of switching kinetics allows us to develop a characteristic transfer function that has only one parameter viz. the characteristic switching time and fully predicts the resistive states of this type of memristor.

  5. Multiferroic Double Perovskites ScFe1-xCrxO3 (1 /6 ≤x ≤5 /6 ) for Highly Efficient Photovoltaics and Spintronics

    Science.gov (United States)

    Cai, Tian-Yi; Liu, Shi-Chen; Ju, Sheng; Liu, Cheng-You; Guo, Guang-Yu

    2017-09-01

    Ferroelectric oxides are attractive materials for constructing efficient solar cells. Nevertheless, a wide band gap of nearly 3.0 eV in these ferroelectric oxides would result in poor overall sunlight absorption and, hence, low energy conversion efficiency. Here, by systematic first-principles density-functional calculations, we demonstrate that double-perovskite semiconductors ScFe1-xCrxO3 (1 /6 ≤x ≤5 /6 ) with a narrow band gap of approximately 1.8 eV would simultaneously exhibit large ferroelectric polarization (100 μ C /cm2 ) and ferrimagnetic magnetization (170 emu/cm3 ). Within a Schottky-based model for a typical sandwich solar-cell structure, a power-conversion efficiency of 9.0% can be reached by neglecting all other sources of photovoltaicity in ferroelectric materials. This value is larger than the largest value of 8.1% observed in ferroelectric oxides. Furthermore, these double perovskites are found to be single-spin semiconductors, and the obtained photocurrent is fully spin polarized over almost the entire Sun spectrum. These fascinating advantages would make ScFex Cr1 -xO3 (1 /6 ≤x ≤5 /6 ) semiconductors promising candidates for highly efficient solar cells and spin photovoltaic devices.

  6. Topotactic synthesis of strontium cobalt oxyhydride thin film with perovskite structure

    OpenAIRE

    Tsukasa Katayama; Akira Chikamatsu; Hideyuki Kamisaka; Yuichi Yokoyama; Yasuyuki Hirata; Hiroki Wadati; Tomoteru Fukumura; Tetsuya Hasegawa

    2015-01-01

    The substitution of hydride anions (H−) into transition metal oxides has recently become possible through topotactic reactions or high-pressure synthesis methods. However, the fabrication of oxyhydrides is still difficult because of their inherently less-stable frameworks. In this study, we successfully fabricated perovskite SrCoOxHy thin films via the topotactic hydride doping of brownmillerite SrCoO2.5 epitaxial thin films with CaH2. The perovskite-type cation framework was maintained durin...

  7. Ab-initio study of the relation between electric polarization and electric field gradients in ferroelectrics

    CERN Document Server

    Gonçalves, J N; Correia, J G; Butz, T; Picozzi, S; Fenta, A S; Amaral, V S

    2012-01-01

    The hyperfine interaction between the quadrupole moment of atomic nuclei and the electric field gradient (EFG) provides information on the electronic charge distribution close to a given atomic site. In ferroelectric materials, the loss of inversion symmetry of the electronic charge distribution is necessary for the appearance of the electric polarization. We present first-principles density functional theory calculations of ferroelectrics such as BaTiO$_{3}$, KNbO$_{3}$, PbTiO$_{3}$ and other oxides with perovskite structures, by focusing on both EFG tensors and polarization. We analyze the EFG tensor properties such as orientation and correlation between components and their relation with electric polarization. This work supports previous studies of ferroelectric materials where a relation between EFG tensors and polarization was observed, which may be exploited to study the ferroelectric order when standard techniques to measure polarization are not easily applied.

  8. Field-emission from quantum-dot-in-perovskite solids.

    Science.gov (United States)

    García de Arquer, F Pelayo; Gong, Xiwen; Sabatini, Randy P; Liu, Min; Kim, Gi-Hwan; Sutherland, Brandon R; Voznyy, Oleksandr; Xu, Jixian; Pang, Yuangjie; Hoogland, Sjoerd; Sinton, David; Sargent, Edward

    2017-03-24

    Quantum dot and well architectures are attractive for infrared optoelectronics, and have led to the realization of compelling light sensors. However, they require well-defined passivated interfaces and rapid charge transport, and this has restricted their efficient implementation to costly vacuum-epitaxially grown semiconductors. Here we report solution-processed, sensitive infrared field-emission photodetectors. Using quantum-dots-in-perovskite, we demonstrate the extraction of photocarriers via field emission, followed by the recirculation of photogenerated carriers. We use in operando ultrafast transient spectroscopy to sense bias-dependent photoemission and recapture in field-emission devices. The resultant photodiodes exploit the superior electronic transport properties of organometal halide perovskites, the quantum-size-tuned absorption of the colloidal quantum dots and their matched interface. These field-emission quantum-dot-in-perovskite photodiodes extend the perovskite response into the short-wavelength infrared and achieve measured specific detectivities that exceed 10 12 Jones. The results pave the way towards novel functional photonic devices with applications in photovoltaics and light emission.

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

    Science.gov (United States)

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

    2015-06-01

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

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

    Science.gov (United States)

    Watanabe, Yukio

    1999-05-01

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

  11. Growth of strained, ferroelectric NaNbO{sub 3} thin films by pulsed laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Sellmann, Jan; Schwarzkopf, Jutta; Duk, Andreas; Kwasniewski, Albert; Schmidbauer, Martin; Fornari, Roberto [IKZ, Berlin (Germany)

    2012-07-01

    Due to its promising ferro-/piezoelectric properties and high Curie temperature NaNbO{sub 3} has attracted much attention. In contrast to bulk crystals, thin epitaxial films may incorporate and maintain a certain compressive or tensile lattice strain, depending on the used substrate/film combination. This deformation of the crystal lattice is known to strongly influence the ferroelectric properties of perovskites. In the case of NaNbO{sub 3} compressive strain is achieved in films deposited on NdGaO{sub 3} and SrTiO{sub 3} substrates while deposition on DyScO{sub 3} and TbScO{sub 3} leads to tensile in-plane strain. In order to characterize and practically apply the ferroelectric films, it is necessary to embed them in a capacitor structure for which we use pseudomorphically grown SrRuO{sub 3} as bottom electrodes. We report on the deposition of SrRuO{sub 3} and NaNbO{sub 3} single layers on SrTiO{sub 3}, DyScO{sub 3}, TbScO{sub 3} and NbGaO{sub 3} substrates by means of pulsed laser deposition. By adjusting the substrate temperature, the oxygen partial pressure and the laser frequency we have successfully deposited smooth, strained, single phase NaNbO{sub 3} thin films. Investigations of the films by atomic force microscopy and high resolution X-ray diffraction reveal the dependence of the surface morphology and the incorporated lattice strain on the deposition parameters and the lattice mismatch, respectively. All films exhibit piezoelectric properties, as proven by piezoresponse force microscopy.

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

    International Nuclear Information System (INIS)

    Bennett, Joseph W.; Rabe, Karin M.

    2012-01-01

    In this concept paper, the development of strategies for the integration of first-principles methods with crystallographic database mining for the discovery and design of novel ferroelectric materials is discussed, drawing on the results and experience derived from exploratory investigations on three different systems: (1) the double perovskite Sr(Sb 1/2 Mn 1/2 )O 3 as a candidate semiconducting ferroelectric; (2) polar derivatives of schafarzikite MSb 2 O 4 ; and (3) ferroelectric semiconductors with formula M 2 P 2 (S,Se) 6 . A variety of avenues for further research and investigation are suggested, including automated structure type classification, low-symmetry improper ferroelectrics, and high-throughput first-principles searches for additional representatives of structural families with desirable functional properties. - Graphical abstract: Integration of first-principles methods with crystallographic database mining, for the discovery and design of novel ferroelectric materials, could potentially lead to new classes of multifunctional materials. Highlights: ► Integration of first-principles methods and database mining. ► Minor structural families with desirable functional properties. ► Survey of polar entries in the Inorganic Crystal Structural Database.

  13. Topotactic synthesis of strontium cobalt oxyhydride thin film with perovskite structure

    Energy Technology Data Exchange (ETDEWEB)

    Katayama, Tsukasa [Department of Chemistry, The University of Tokyo, Tokyo 113-0033 (Japan); Chikamatsu, Akira, E-mail: chikamatsu@chem.s.u-tokyo.ac.jp; Kamisaka, Hideyuki [Department of Chemistry, The University of Tokyo, Tokyo 113-0033 (Japan); CREST, Japan Science and Technology Agency (JST), Tokyo 113-0033 (Japan); Yokoyama, Yuichi; Hirata, Yasuyuki; Wadati, Hiroki [Institute for Solid State Physics, The University of Tokyo, Chiba 277-8581 (Japan); Fukumura, Tomoteru [CREST, Japan Science and Technology Agency (JST), Tokyo 113-0033 (Japan); Department of Chemistry, Tohoku University, Miyagi 980-8578 (Japan); Hasegawa, Tetsuya [Department of Chemistry, The University of Tokyo, Tokyo 113-0033 (Japan); CREST, Japan Science and Technology Agency (JST), Tokyo 113-0033 (Japan); Kanagawa Academy of Science and Technology (KAST), Kawasaki 213-0012 (Japan)

    2015-10-15

    The substitution of hydride anions (H{sup −}) into transition metal oxides has recently become possible through topotactic reactions or high-pressure synthesis methods. However, the fabrication of oxyhydrides is still difficult because of their inherently less-stable frameworks. In this study, we successfully fabricated perovskite SrCoO{sub x}H{sub y} thin films via the topotactic hydride doping of brownmillerite SrCoO{sub 2.5} epitaxial thin films with CaH{sub 2}. The perovskite-type cation framework was maintained during the topotactic treatment owing to epitaxial stabilization. Structural and chemical analyses accompanied by X-ray absorption spectroscopy measurements revealed that the doped hydride ions form a two-dimensional network of Co-H{sup −}-Co bonds, in contrast to other reported perovskite oxyhydrides, SrMO{sub 3−x}H{sub x} (M = Cr, Ti, V). The SrCoO{sub x}H{sub y} thin film exhibited insulating behavior and had a direct band gap of 2.1 eV. Thus, topotactic hydride doping of transition-metal-oxide thin films on suitable substrates is a promising method for the synthesis of new transition metal oxyhydrides.

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

    Science.gov (United States)

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

    2016-03-08

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

  15. Ferroelectric and optical properties of `Ba-doped' new double perovskites

    Science.gov (United States)

    Parida, B. N.; Panda, Niranjan; Padhee, R.; Parida, R. K.

    2018-06-01

    Solid solution of Pb1.5Ba0.5BiNbO6 ceramic is explored here to obtain its ferroelectric and optical properties. The polycrystalline sample was prepared by a standard solid state reaction route. Room temperature XRD and FTIR spectra of the compound exhibit an appreciable change in its crystal structure of Pb2BiNbO6 on addition of 'Ba' in A site. The surface morphology of the gold-plated sintered pellet sample recorded by SEM exhibits a uniform distribution of small grains with well-defined grain boundaries. Detailed studies on the nature of polarization and variation of dielectric constant, tangent loss with temperature as well as frequency indicate the existence of Ferro-electricity in the sample. Using UV-Vis spectroscopy, the optical band gap of the studied sample has been estimated as 2.1 eV, which is useful for photo catalytic devices. Photoluminescence analysis of the powder sample shows a strong red photoluminescence with blue excitation, which is basically useful for LED.

  16. A family of oxide ion conductors based on the ferroelectric perovskite Na0.5Bi0.5TiO3.

    Science.gov (United States)

    Li, Ming; Pietrowski, Martha J; De Souza, Roger A; Zhang, Huairuo; Reaney, Ian M; Cook, Stuart N; Kilner, John A; Sinclair, Derek C

    2014-01-01

    Oxide ion conductors find important technical applications in electrochemical devices such as solid-oxide fuel cells (SOFCs), oxygen separation membranes and sensors. Na0.5Bi0.5TiO3 (NBT) is a well-known lead-free piezoelectric material; however, it is often reported to possess high leakage conductivity that is problematic for its piezo- and ferroelectric applications. Here we report this high leakage to be oxide ion conduction due to Bi-deficiency and oxygen vacancies induced during materials processing. Mg-doping on the Ti-site increases the ionic conductivity to ~0.01 S cm(-1) at 600 °C, improves the electrolyte stability in reducing atmospheres and lowers the sintering temperature. This study not only demonstrates how to adjust the nominal NBT composition for dielectric-based applications, but also, more importantly, gives NBT-based materials an unexpected role as a completely new family of oxide ion conductors with potential applications in intermediate-temperature SOFCs and opens up a new direction to design oxide ion conductors in perovskite oxides.

  17. BiFeO3 epitaxial thin films and devices: past, present and future

    Science.gov (United States)

    Sando, D.; Barthélémy, A.; Bibes, M.

    2014-11-01

    The celebrated renaissance of the multiferroics family over the past ten years has also been that of its most paradigmatic member, bismuth ferrite (BiFeO3). Known since the 1960s to be a high temperature antiferromagnet and since the 1970s to be ferroelectric, BiFeO3 only had its bulk ferroic properties clarified in the mid-2000s. It is however the fabrication of BiFeO3 thin films and their integration into epitaxial oxide heterostructures that have fully revealed its extraordinarily broad palette of functionalities. Here we review the first decade of research on BiFeO3 films, restricting ourselves to epitaxial structures. We discuss how thickness and epitaxial strain influence not only the unit cell parameters, but also the crystal structure, illustrated for instance by the discovery of the so-called T-like phase of BiFeO3. We then present its ferroelectric and piezoelectric properties and their evolution near morphotropic phase boundaries. Magnetic properties and their modification by thickness and strain effects, as well as optical parameters, are covered. Finally, we highlight various types of devices based on BiFeO3 in electronics, spintronics, and optics, and provide perspectives for the development of further multifunctional devices for information technology and energy harvesting.

  18. Dynamics of ferroelectric nanodomains in BaTiO3 epitaxial thin films via piezoresponse force microscopy

    International Nuclear Information System (INIS)

    Pertsev, N A; Petraru, A; Kohlstedt, H; Waser, R; Bdikin, I K; Kiselev, D; Kholkin, A L

    2008-01-01

    Ferroelectric nanodomains were created in BaTiO 3 thin films by applying a voltage to a sharp conducting tip of a scanning force microscope (SFM). The films were epitaxially grown on SrRuO 3 -covered (001)-oriented SrTiO 3 substrates by a high-pressure sputtering. They appeared to be single-crystalline with the (001) crystallographic orientation relative to the substrate. Using the piezoresponse mode of the SFM to detect the out-of-plane film polarization, the domain sizes were measured as a function of the applied writing voltage and the pulse time. It was found that the time dependence of the domain diameter in a 60 nm thick BaTiO 3 film deviates significantly from the logarithmic law observed earlier in Pb(Zr 0.2 Ti 0.8 )O 3 (PZT) films. At a given writing time, the domain size increases nonlinearly with increasing applied voltage, in contrast to the linear behavior reported earlier for PZT films and LiNbO 3 single crystals. The dynamics of domain growth is analyzed theoretically taking into account the strong inhomogeneity of the external electric field in the film and the influence of the bottom electrode. It is shown that the observed writing time and voltage dependences of the domain size can be explained by the domain-wall creep in the presence of random-bond disorder

  19. Quantum-dot-in-perovskite solids

    KAUST Repository

    Ning, Zhijun; Gong, Xiwen; Comin, Riccardo; Walters, Grant; Fan, Fengjia; Voznyy, Oleksandr; Yassitepe, Emre; Buin, Andrei; Hoogland, Sjoerd; Sargent, Edward H.

    2015-01-01

    © 2015 Macmillan Publishers Limited. All rights reserved. Heteroepitaxy - atomically aligned growth of a crystalline film atop a different crystalline substrate - is the basis of electrically driven lasers, multijunction solar cells, and blue-light-emitting diodes. Crystalline coherence is preserved even when atomic identity is modulated, a fact that is the critical enabler of quantum wells, wires, and dots. The interfacial quality achieved as a result of heteroepitaxial growth allows new combinations of materials with complementary properties, which enables the design and realization of functionalities that are not available in the single-phase constituents. Here we show that organohalide perovskites and preformed colloidal quantum dots, combined in the solution phase, produce epitaxially aligned 'dots-in-a-matrix' crystals. Using transmission electron microscopy and electron diffraction, we reveal heterocrystals as large as about 60 nanometres and containing at least 20 mutually aligned dots that inherit the crystalline orientation of the perovskite matrix. The heterocrystals exhibit remarkable optoelectronic properties that are traceable to their atom-scale crystalline coherence: photoelectrons and holes generated in the larger-bandgap perovskites are transferred with 80% efficiency to become excitons in the quantum dot nanocrystals, which exploit the excellent photocarrier diffusion of perovskites to produce bright-light emission from infrared-bandgap quantum-tuned materials. By combining the electrical transport properties of the perovskite matrix with the high radiative efficiency of the quantum dots, we engineer a new platform to advance solution-processed infrared optoelectronics.

  20. Quantum-dot-in-perovskite solids

    KAUST Repository

    Ning, Zhijun

    2015-07-15

    © 2015 Macmillan Publishers Limited. All rights reserved. Heteroepitaxy - atomically aligned growth of a crystalline film atop a different crystalline substrate - is the basis of electrically driven lasers, multijunction solar cells, and blue-light-emitting diodes. Crystalline coherence is preserved even when atomic identity is modulated, a fact that is the critical enabler of quantum wells, wires, and dots. The interfacial quality achieved as a result of heteroepitaxial growth allows new combinations of materials with complementary properties, which enables the design and realization of functionalities that are not available in the single-phase constituents. Here we show that organohalide perovskites and preformed colloidal quantum dots, combined in the solution phase, produce epitaxially aligned \\'dots-in-a-matrix\\' crystals. Using transmission electron microscopy and electron diffraction, we reveal heterocrystals as large as about 60 nanometres and containing at least 20 mutually aligned dots that inherit the crystalline orientation of the perovskite matrix. The heterocrystals exhibit remarkable optoelectronic properties that are traceable to their atom-scale crystalline coherence: photoelectrons and holes generated in the larger-bandgap perovskites are transferred with 80% efficiency to become excitons in the quantum dot nanocrystals, which exploit the excellent photocarrier diffusion of perovskites to produce bright-light emission from infrared-bandgap quantum-tuned materials. By combining the electrical transport properties of the perovskite matrix with the high radiative efficiency of the quantum dots, we engineer a new platform to advance solution-processed infrared optoelectronics.

  1. The origin of local strain in highly epitaxial oxide thin films.

    Science.gov (United States)

    Ma, Chunrui; Liu, Ming; Chen, Chonglin; Lin, Yuan; Li, Yanrong; Horwitz, J S; Jiang, Jiechao; Meletis, E I; Zhang, Qingyu

    2013-10-31

    The ability to control the microstructures and physical properties of hetero-epitaxial functional oxide thin films and artificial structures is a long-sought goal in functional materials research. Normally, only the lattice misfit between the film and the substrate is considered to govern the physical properties of the epitaxial films. In fact, the mismatch of film unit cell arrangement and the Surface-Step-Terrace (SST) dimension of the substrate, named as "SST residual matching", is another key factor that significantly influence the properties of the epitaxial film. The nature of strong local strain induced from both lattice mismatch and the SST residual matching on ferroelectric (Ba,Sr)TiO3 and ferromagnetic (La,Ca)MnO3 thin films are systematically investigated and it is demonstrated that this combined effect has a dramatic impact on the physical properties of highly epitaxial oxide thin films. A giant anomalous magnetoresistance effect (~10(10)) was achieved from the as-designed vicinal surfaces.

  2. Multiferroic Properties of o-LuMnO3 Controlled by b-Axis Strain

    Science.gov (United States)

    Windsor, Y. W.; Huang, S. W.; Hu, Y.; Rettig, L.; Alberca, A.; Shimamoto, K.; Scagnoli, V.; Lippert, T.; Schneider, C. W.; Staub, U.

    2014-10-01

    Strain is a leading candidate for controlling magnetoelectric coupling in multiferroics. Here, we use x-ray diffraction to study the coupling between magnetic order and structural distortion in epitaxial films of the orthorhombic (o-) perovskite LuMnO3. An antiferromagnetic spin canting in the E-type magnetic structure is shown to be related to the ferroelectrically induced structural distortion and to a change in the magnetic propagation vector. By comparing films of different orientations and thicknesses, these quantities are found to be controlled by b-axis strain. It is shown that compressive strain destabilizes the commensurate E-type structure and reduces its accompanying ferroelectric distortion.

  3. PbBr3 Perovskite Crystals

    KAUST Repository

    Wei, Tzu-Chiao

    2018-01-31

    Researchers have recently revealed that hybrid lead halide perovskites exhibit ferroelectricity, which is often associated with other physical characteristics, such as a large nonlinear optical response. In this work, the nonlinear optical properties of single crystal inorganic–organic hybrid perovskite CH3NH3PbBr3 are studied. By exciting the material with a 1044 nm laser, strong two-photon absorption-induced photoluminescence in the green spectral region is observed. Using the transmission open-aperture Z-scan technique, the values of the two-photon absorption coefficient are observed to be 8.5 cm GW−1, which is much higher than that of standard two-photon absorbing materials that are industrially used in nonlinear optical applications, such as lithium niobate (LiNbO3), LiTaO3, KTiOPO4, and KH2PO4. Such a strong two-photon absorption effect in CH3NH3PbBr3 can be used to modulate the spectral and spatial profiles of laser pulses, as well as to reduce noise, and can be used to strongly control the intensity of incident light. In this study, the superior optical limiting, pulse reshaping, and stabilization properties of CH3NH3PbBr3 are demonstrated, opening new applications for perovskites in nonlinear optics.

  4. Polarization enhancement and ferroelectric switching enabled by interacting magnetic structures in DyMnO3 thin films

    KAUST Repository

    Lu, Chengliang

    2013-12-02

    The mutual controls of ferroelectricity and magnetism are stepping towards practical applications proposed for quite a few promising devices in which multiferroic thin films are involved. Although ferroelectricity stemming from specific spiral spin ordering has been reported in highly distorted bulk perovskite manganites, the existence of magnetically induced ferroelectricity in the corresponding thin films remains an unresolved issue, which unfortunately halts this step. In this work, we report magnetically induced electric polarization and its remarkable response to magnetic field (an enhancement of ?800% upon a field of 2 Tesla at 2 K) in DyMnO3 thin films grown on Nb-SrTiO3 substrates. Accompanying with the large polarization enhancement, the ferroelectric coercivity corresponding to the magnetic chirality switching field is significantly increased. A picture based on coupled multicomponent magnetic structures is proposed to understand these features. Moreover, different magnetic anisotropy related to strain-suppressed GdFeO 3-type distortion and Jahn-Teller effect is identified in the films.

  5. Ferroelectricity with Ferromagnetic Moment in Orthoferrites

    Science.gov (United States)

    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).

  6. Lanthanide gallate perovskite-type substrates for epitaxial, high-Tc superconducting Ba2YCu3O7-δ films

    International Nuclear Information System (INIS)

    Giess, E.A.; Sandstrom, R.L.; Gallagher, W.J.; Gupta, A.; Shinde, S.L.; Cook, R.F.; Cooper, E.L.; O'Sullivan, E.M.J.; Roldan, J.M.; Segmuller, A.D.; Angilello, J.

    1990-01-01

    This paper reports on the use of lanthanide gallate perovskite-type substrates for the deposition of epitaxial, high-T c superconducting Ba 2 YCu 3 O 7-δ (BYCO) films. They were also found to have moderate dielectric constants (∼25 compared to ∼ 277 for SrTiO 3 ). This study was undertaken to further explore the use of LaGaO 3 , NdGaO 3 , SrTiO 3 , MgO, and Y-stabilized ZrO 2 substrates, prepared from single-crystal joules grown by several suppliers using the Czochralski method. Films were prepared by cylindrical magnetron sputtering and laser ablation. Substrate evaluations included measurement of dielectric constant and loss, thermal expansion, and mechanical hardness and toughness. In addition to their moderate dielectric constants, they were found to have satisfactory mechanical properties, except for the twinning tendency of LaGaO 3 . Lattice mismatch strains were calculated for orthorhombic BYCO films on a number of substrates. NdGaO 3 was found to have the best lattice match with BYCO, and is now available twin-free

  7. Optical effects induced by epitaxial tension in lead titanate

    Czech Academy of Sciences Publication Activity Database

    Dejneka, Alexandr; Chvostová, Dagmar; Pacherová, Oliva; Kocourek, Tomáš; Jelínek, Miroslav; Tyunina, Marina

    2018-01-01

    Roč. 112, č. 3 (2018), s. 1-5, č. článku 031111. ISSN 0003-6951 R&D Projects: GA ČR GA15-13778S; GA ČR GA15-15123S Institutional support: RVO:68378271 Keywords : epitaxy * inorganic compounds * optical properties * ferroelectric materials * optical metrology Subject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Condensed matter physics (including formerly solid state physics , supercond.) Impact factor: 3.411, year: 2016

  8. Ba-DOPED ZnO MATERIALS: A DFT SIMULATION TO INVESTIGATE THE DOPING EFFECT ON FERROELECTRICITY

    Directory of Open Access Journals (Sweden)

    Luis H. da S. Lacerda

    2016-04-01

    Full Text Available ZnO is a semiconductor material largely employed in the development of several electronic and optical devices due to its unique electronic, optical, piezo-, ferroelectric and structural properties. This study evaluates the properties of Ba-doped wurtzite-ZnO using quantum mechanical simulations based on the Density Functional Theory (DFT allied to hybrid functional B3LYP. The Ba-doping caused increase in lattice parameters and slight distortions at the unit cell angle in a wurtzite structure. In addition, the doping process presented decrease in the band-gap (Eg at low percentages suggesting band-gap engineering. For low doping amounts, the wavelength characteristic was observed in the visible range; whereas, for middle and high doping amounts, the wavelength belongs to the Ultraviolet range. The Ba atoms also influence the ferroelectric property, which is improved linearly with the doping amount, except for doping at 100% or wurtzite-BaO. The ferroelectric results indicate the ZnO:Ba is an strong option to replace perovskite materials in ferroelectric and flash-type memory devices.

  9. History and the future perspective of the ferroelectric memory; Kyoyudentai memory no rekishiteki haikei to tenbo

    Energy Technology Data Exchange (ETDEWEB)

    Tarui, Y [Waseda University, Tokyo (Japan)

    1998-10-01

    Development work is in progress on ferroelectric memory. The memory is a most suitable non-volatile memory which can be incorporated into IC cards, with its higher speed, lower voltage operation, smaller power consumption, and greater number of rewriting times than EEPROM, DRAM and SRAM. Taking as an opportunity the announcement on an experiment as performed by the authors to control semiconductor charge by using electric depolarization of ferroelectric materials, reports have been made one after another on experiments on thin metal films on TGS or BaTiO3, and experiments on semiconductor films formed on ferroelectric crystals or ceramics substrates by using vacuum deposition. In order to solve problems in ferroelectric materials, thin films of PZT and PLZT have emerged, whose good hysteresis characteristics have also been reported. Thereafter, an announcement was made on a material with bismuth layer like perovskite structure. The material is characterized with having very little film fatigue degradation after rewriting of about 10 {sup 12} times. In scaling a ferroelectric memory, if voltage is decreased in proportion with the size, the operation can be reduced proportionately according to the voltage reduction. This paper introduces a method to constitute a ferroelectric memory. 22 refs., 11 figs., 2 tabs.

  10. Dielectric and magnetic properties, and electronic structure of multiferroic perovskite PbFe.sub.0.5./sub.Ta.sub.0.5./sub.O.sub.3./sub. and incipient ferroelectric pyrochlore Pb.sub.2./sub.Fe.sub.0.34./sub.Ta.sub.1.84./sub.O.sub.7.11./sub. single crystals and ceramics

    Czech Academy of Sciences Publication Activity Database

    Kania, A.; Miga, S.; Talik, E.; Gruszka, I.; Szubka, M.; Savinov, Maxim; Prokleška, J.; Kamba, Stanislav

    2016-01-01

    Roč. 36, č. 14 (2016), s. 3369-3381 ISSN 0955-2219 R&D Projects: GA ČR GA15-08389S Institutional support: RVO:68378271 Keywords : lead iron tantalate * perovskite multiferroic * pyrochlore * incipient ferroelectric * X-ray photoelectron spectroscopy Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.411, year: 2016

  11. Crystallization engineering as a route to epitaxial strain control

    Directory of Open Access Journals (Sweden)

    Andrew R. Akbashev

    2015-10-01

    Full Text Available The controlled synthesis of epitaxial thin films offers opportunities for tuning their functional properties via enabling or suppressing strain relaxation. Examining differences in the epitaxial crystallization of amorphous oxide films, we report on an alternate, low-temperature route for strain engineering. Thin films of amorphous Bi–Fe–O were grown on (001SrTiO3 and (001LaAlO3 substrates via atomic layer deposition. In situ X-ray diffraction and X-ray photoelectron spectroscopy studies of the crystallization of the amorphous films into the epitaxial (001BiFeO3 phase reveal distinct evolution profiles of crystallinity with temperature. While growth on (001SrTiO3 results in a coherently strained film, the same films obtained on (001LaAlO3 showed an unstrained, dislocation-rich interface, with an even lower temperature onset of the perovskite phase crystallization than in the case of (001SrTiO3. Our results demonstrate how the strain control in an epitaxial film can be accomplished via its crystallization from the amorphous state.

  12. Adsorption-controlled growth of BiMnO3 films by molecular-beam epitaxy

    International Nuclear Information System (INIS)

    Lee, J. H.; Ke, X.; Misra, R.; Schiffer, P.; Ihlefeld, J. F.; Mei, Z. G.; Liu, Z. K.; Xu, X. S.; Musfeldt, J. L.; Heeg, T.; Schlom, D. G.; Roeckerath, M.; Schubert, J.

    2010-01-01

    We have developed the means to grow BiMnO 3 thin films with unparalleled structural perfection by reactive molecular-beam epitaxy and determined its band gap. Film growth occurs in an adsorption-controlled growth regime. Within this growth window bounded by oxygen pressure and substrate temperature at a fixed bismuth overpressure, single-phase films of the metastable perovskite BiMnO 3 may be grown by epitaxial stabilization. X-ray diffraction reveals phase-pure and epitaxial films with ω rocking curve full width at half maximum values as narrow as 11 arc sec (0.003 deg. ). Optical absorption measurements reveal that BiMnO 3 has a direct band gap of 1.1±0.1 eV.

  13. Synthesis of ferroelectric nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Roervik, Per Martin

    2008-12-15

    The increasing miniaturization of electric and mechanical components makes the synthesis and assembly of nanoscale structures an important step in modern technology. Functional materials, such as the ferroelectric perovskites, are vital to the integration and utility value of nanotechnology in the future. In the present work, chemical methods to synthesize one-dimensional (1D) nanostructures of ferroelectric perovskites have been studied. To successfully and controllably make 1D nanostructures by chemical methods it is very important to understand the growth mechanism of these nanostructures, in order to design the structures for use in various applications. For the integration of 1D nanostructures into devices it is also very important to be able to make arrays and large-area designed structures from the building blocks that single nanostructures constitute. As functional materials, it is of course also vital to study the properties of the nanostructures. The characterization of properties of single nanostructures is challenging, but essential to the use of such structures. The aim of this work has been to synthesize high quality single-crystalline 1D nanostructures of ferroelectric perovskites with emphasis on PbTiO3 , to make arrays or hierarchical nanostructures of 1D nanostructures on substrates, to understand the growth mechanisms of the 1D nanostructures, and to investigate the ferroelectric and piezoelectric properties of the 1D nanostructures. In Paper I, a molten salt synthesis route, previously reported to yield BaTiO3 , PbTiO3 and Na2Ti6O13 nanorods, was re-examined in order to elucidate the role of volatile chlorides. A precursor mixture containing barium (or lead) and titanium was annealed in the presence of NaCl at 760 degrees Celsius or 820 degrees Celsius. The main products were respectively isometric nanocrystalline BaTiO3 and PbTiO3. Nanorods were also detected, but electron diffraction revealed that the composition of the nanorods was

  14. Structure and switching of in-plane ferroelectric nano-domains in strained PbxSr1-xTiO3 thin films

    Energy Technology Data Exchange (ETDEWEB)

    Matzen, Sylivia [University of Groningen, The Netherlands; Nesterov, Okeksiy [ORNL; Rispens, Gregory [University of Groningen, The Netherlands; Heuver, J. A. [University of Groningen, The Netherlands; Bark, C [University of Wisconsin, Madison; Biegalski, Michael D [ORNL; Christen, Hans M [ORNL; Noheda, Beatriz [University of Groningen, The Netherlands

    2014-01-01

    Nanoscale ferroelectrics, the active elements of a variety of nanoelectronic devices, develop denser and richer domain structures than the bulk counterparts. With shrinking device sizes understanding and controlling domain formation in nanoferroelectrics is being intensely studied. Here we show that a precise control of the epitaxy and the strain allows stabilizing a hierarchical domain architecture in PbxSr1-xTiO3 thin films, showing periodic, purely in-plane polarized, ferroelectric nano-domains that can be switched by a scanning probe.

  15. Growth and characterization of epitaxial thin films and multiferroic heterostructures of ferromagnetic and ferroelectric materials

    Science.gov (United States)

    Mukherjee, Devajyoti

    Multiferroic materials exhibit unique properties such as simultaneous existence of two or more of coupled ferroic order parameters (ferromagnetism, ferroelectricity, ferroelasticity or their anti-ferroic counterparts) in a single material. Recent years have seen a huge research interest in multiferroic materials for their potential application as high density non-volatile memory devices. However, the scarcity of these materials in single phase and the weak coupling of their ferroic components have directed the research towards multiferroic heterostructures. These systems operate by coupling the magnetic and electric properties of two materials, generally a ferromagnetic material and a ferroelectric material via strain. In this work, horizontal heterostructures of composite multiferroic materials were grown and characterized using pulsed laser ablation technique. Alternate magnetic and ferroelectric layers of cobalt ferrite and lead zirconium titanate, respectively, were fabricated and the coupling effect was studied by X-ray stress analysis. It was observed that the interfacial stress played an important role in the coupling effect between the phases. Doped zinc oxide (ZnO) heterostructures were also studied where the ferromagnetic phase was a layer of manganese doped ZnO and the ferroelectric phase was a layer of vanadium doped ZnO. For the first time, a clear evidence of possible room temperature magneto-elastic coupling was observed in these heterostructures. This work provides new insight into the stress mediated coupling mechanisms in composite multiferroics.

  16. Thickness dependent charge transport in ferroelectric BaTiO3 heterojunctions

    Science.gov (United States)

    Singh, Pooja; Rout, P. K.; Singh, Manju; Rakshit, R. K.; Dogra, Anjana

    2015-09-01

    We have investigated the effect of ferroelectric barium titanate (BaTiO3) film thickness on the charge transport mechanism in pulsed laser deposited epitaxial metal-ferroelectric semiconductor junctions. The current (I)-voltage (V) measurements across the junctions comprising of 20-500 nm thick BaTiO3 and conducting bottom electrode (Nb: SrTiO3 substrate or La2/3Ca1/3MnO3 buffer layer) demonstrate the space charge limited conduction. Further analysis indicates a reduction in the ratio of free to trapped carriers with increasing thickness in spite of decreasing trap density. Such behaviour arises the deepening of the shallow trap levels (I-V curves implies a bipolar resistive switching behaviour, which can be explained in terms of charge trapping and de-trapping process.

  17. Intrinsic stability of ferroelectric and piezoelectric properties of epitaxial PbZr0.45Ti0.55O3 thin films on silicon in relation to grain tilt

    Directory of Open Access Journals (Sweden)

    Evert P Houwman, Minh D Nguyen, Matthijn Dekkers and Guus Rijnders

    2013-01-01

    Full Text Available Piezoelectric thin films of PbZr0.45Ti0.55O3 were grown on Si substrates in four different ways, resulting in different crystalline structures, as determined by x-ray analysis. The crystalline structures were different in the spread in tilt angle and the in-plane alignment of the crystal planes between different grains. It is found that the deviations of the ferroelectric polarization loop from that of the ideal rectangular loop (reduction of the remanent polarization with respect to the saturation polarization, dielectric constant of the film, slanting of the loop, coercive field value all scale with the average tilt angle. A model is derived based on the assumption that the tilted grain boundaries between grains affect the film properties locally. This model describes the observed trends. The effective piezoelectric coefficient d33,eff shows also a weak dependence on the average tilt angle for films grown in a single layer, whereas it is strongly reduced for the films deposited in multiple layers. The least affected properties are obtained for the most epitaxial films, i.e. grown on a SrTiO3 epitaxial seed layer, by pulsed laser deposition. These films are intrinsically stable and do not require poling to acquire these stable properties.

  18. Preparation and characterization of single-crystal multiferroic nanofiber composites

    Energy Technology Data Exchange (ETDEWEB)

    Ren, Zhaohui; Xiao, Zhen; Yin, Simin; Mai, Jiangquan; Liu, Zhenya; Xu, Gang; Li, Xiang; Shen, Ge [State Key Lab of Silicon Materials, Department of Material Science and Engineering, Cyrus Tang Center for Sensor Materials and Applications, Zhejiang University, Hangzhou 310027 (China); Han, Gaorong, E-mail: hgr@zju.edu.cn [State Key Lab of Silicon Materials, Department of Material Science and Engineering, Cyrus Tang Center for Sensor Materials and Applications, Zhejiang University, Hangzhou 310027 (China)

    2013-03-05

    Graphical abstract: One-dimensional single-crystal multiferroic composites composed of PbTiO{sub 3} nanofiber-CoFe{sub 2}O{sub 4} nanodot have been prepared for the first time by a facile in situ solid state sintering method. The composites demonstrate ferroelectricity and ferromagnetism as well as strong coupling between them. Highlights: ► 1D single-crystal multiferroic PTO-CFO was prepared via in situ solid state sintering method. ► A simple epitaxial growth relation has been found between the PTO–CFO composites. ► The composites reveal ferroelectricity and ferromagnetism as well as coupling between them. -- Abstract: One-dimensional single-crystal multiferroic composites consisting of PbTiO{sub 3} (PTO) nanofiber-CoFe{sub 2}O{sub 4} (CFO) nanodot were prepared using an in situ solid state sintering method, where pre-perovskite PTO nanofibers and CFO nanodots were used as precursors. Structural analyses by using transmission electron microscopy, scanning electron microscopy and X-ray diffraction determined a epitaxial growth relation between the PTO nanofiber and the CFO nanodot. Ferromagnetism and ferroelectricity of the nanofiber composites were investigated by using vibarting sample magnetometer (VSM) and piezoresponse force microscopy (PFM)

  19. Thickness dependence of the switching voltage in all-oxide ferroelectric thin-film capacitors prepared by pulsed laser deposition

    NARCIS (Netherlands)

    Cillessen, J.F.M.; Prins, M.W.J.; Wolf, R.M.

    1997-01-01

    Thin-film ferroelectric capacitors consisting of PbZr0.53Ti0.47O3 sandwiched between La0.5Sr0.5CoO3 electrodes have been deposited using pulsed laser deposition. The combination of oxidic perovskite-type materials results in capacitors with a coercive field (Ec) which is comparable with values for

  20. Structural evolution of epitaxial SrCoOx films near topotactic phase transition

    Science.gov (United States)

    Jeen, Hyoungjeen; Lee, Ho Nyung

    2015-12-01

    Control of oxygen stoichiometry in complex oxides via topotactic phase transition is an interesting avenue to not only modifying the physical properties, but utilizing in many energy technologies, such as energy storage and catalysts. However, detailed structural evolution in the close proximity of the topotactic phase transition in multivalent oxides has not been much studied. In this work, we used strontium cobaltites (SrCoOx) epitaxially grown by pulsed laser epitaxy (PLE) as a model system to study the oxidation-driven evolution of the structure, electronic, and magnetic properties. We grew coherently strained SrCoO2.5 thin films and performed post-annealing at various temperatures for topotactic conversion into the perovskite phase (SrCoO3-δ). We clearly observed significant changes in electronic transport, magnetism, and microstructure near the critical temperature for the topotactic transformation from the brownmillerite to the perovskite phase. Nevertheless, the overall crystallinity was well maintained without much structural degradation, indicating that topotactic phase control can be a useful tool to control the physical properties repeatedly via redox reactions.

  1. Structural evolution of epitaxial SrCoOx films near topotactic phase transition

    Directory of Open Access Journals (Sweden)

    Hyoungjeen Jeen

    2015-12-01

    Full Text Available Control of oxygen stoichiometry in complex oxides via topotactic phase transition is an interesting avenue to not only modifying the physical properties, but utilizing in many energy technologies, such as energy storage and catalysts. However, detailed structural evolution in the close proximity of the topotactic phase transition in multivalent oxides has not been much studied. In this work, we used strontium cobaltites (SrCoOx epitaxially grown by pulsed laser epitaxy (PLE as a model system to study the oxidation-driven evolution of the structure, electronic, and magnetic properties. We grew coherently strained SrCoO2.5 thin films and performed post-annealing at various temperatures for topotactic conversion into the perovskite phase (SrCoO3-δ. We clearly observed significant changes in electronic transport, magnetism, and microstructure near the critical temperature for the topotactic transformation from the brownmillerite to the perovskite phase. Nevertheless, the overall crystallinity was well maintained without much structural degradation, indicating that topotactic phase control can be a useful tool to control the physical properties repeatedly via redox reactions.

  2. A Confined Fabrication of Perovskite Quantum Dots in Oriented MOF Thin Film.

    Science.gov (United States)

    Chen, Zheng; Gu, Zhi-Gang; Fu, Wen-Qiang; Wang, Fei; Zhang, Jian

    2016-10-26

    Organic-inorganic hybrid lead organohalide perovskites are inexpensive materials for high-efficiency photovoltaic solar cells, optical properties, and superior electrical conductivity. However, the fabrication of their quantum dots (QDs) with uniform ultrasmall particles is still a challenge. Here we use oriented microporous metal-organic framework (MOF) thin film prepared by liquid phase epitaxy approach as a template for CH 3 NH 3 PbI 2 X (X = Cl, Br, and I) perovskite QDs fabrication. By introducing the PbI 2 and CH 3 NH 3 X (MAX) precursors into MOF HKUST-1 (Cu 3 (BTC) 2 , BTC = 1,3,5-benzene tricarboxylate) thin film in a stepwise approach, the resulting perovskite MAPbI 2 X (X = Cl, Br, and I) QDs with uniform diameters of 1.5-2 nm match the pore size of HKUST-1. Furthermore, the photoluminescent properties and stability in the moist air of the perovskite QDs loaded HKUST-1 thin film were studied. This confined fabrication strategy demonstrates that the perovskite QDs loaded MOF thin film will be insensitive to air exposure and offers a novel means of confining the uniform size of the similar perovskite QDs according to the oriented porous MOF materials.

  3. Ferroelectric based catalysis: Switchable surface chemistry

    Science.gov (United States)

    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.

  4. What makes the difference in perovskite titanates?

    Science.gov (United States)

    Bussmann-Holder, Annette; Roleder, Krystian; Ko, Jae-Hyeon

    2018-06-01

    We have investigated in detail the lattice dynamics of five different perovskite titanates ATiO3 (A = Ca, Sr, Ba, Pb, Eu) where the A sites are occupied by +2 ions. In spite of the largely ionic character of these ions, the properties of these compounds differ substantially. They range from order/disorder like, to displacive ferroelectric, quantum paraelectric, and antiferromagnetic. All compounds crystallize in the cubic structure at high temperature and undergo structural phase transitions to tetragonal symmetry, partly followed by further transitions to lower symmetries. Since the TiO6 moiety is the essential electronic and structural unit, the question arises, what makes the significant difference between them. It is shown that the lattice dynamics of these compounds are very different, and that mode-mode coupling effects give rise to many distinct properties. In addition, the oxygen ion nonlinear polarizability plays a key role since it dominates the anharmonicity of these perovskites and determines the structural instability.

  5. Transmission electron microscope studies of phase transitions in single crystals and ceramics of ferroelectric Pb(Sc1/2Ta1/2)O3

    International Nuclear Information System (INIS)

    Baba-Kishi, K.Z.; Barber, D.J.

    1990-01-01

    An account is given of transmission electron microscope investigations of the phase transitions in single crystals and ceramics of the complex perovskite-structured ferroelectric 'relaxor' compound Pb(Sc 1/2 Ta 1/2 )O 3 . The crystal symmetries pertaining to both the non-polar paraelectric (PE) and polar ferroelectric (FE) states have been studied by the technique of convergent-beam electron diffraction. A new phase transition has been discovered in the temperature range for which the FE and PE states coexist. The new phase transition is interpreted as the creation of a modulated antiferroelectric state, and this is viewed as marking a departure from relaxor behaviour towards more 'normal' ferroelectric behaviour. (orig.)

  6. III-Nitrides growth and AlGaN/GaN heterostructures on ferroelectric materials

    International Nuclear Information System (INIS)

    Lee, Kyoung-Keun; Namkoong, Gon; Madison, Shannon M.; Ralph, Stephen E.; Doolittle, W. Alan; Losurdo, Maria; Bruno, Giovanni; Cho, Hyung Koun

    2007-01-01

    The growth of III-nitrides on the ferroelectric materials lithium niobate (LN) and lithium tantalate (LT) via molecular beam epitaxy (MBE) using rf plasma source has been investigated. We have found that gallium nitride (GaN) epitaxial layers have a crystalline relationship with lithium niobate (tantalate) as follows: (0 0 0 1) GaN || (0 0 0 1) LN (LT) with [10-10] GaN || [11-20] LN (LT). The surface stability of LN and LT substrates has been monitored by in situ spectroscopic ellipsometry in the vacuum chamber. Three different temperature zones have been discerned; surface degas and loss of OH group (100-350 deg. C); surface segregation/accumulation of Li and O-species (400-700 deg. C); surface evaporation of O-species and Li desorption (over 750 deg. C). However, LT shows only surface degassing in the range of 100-800 deg. C. Therefore, congruent LN substrates were chemically unstable at the growth temperature of 550-650 deg. C, and therefore developed an additional phase of Li-deficient lithium niobate (LiNb 3 O 8 ) along with lithium niobate (LiNbO 3 ), confirmed by X-ray diffraction. On the other hand, LT showed better chemical stability at these temperatures, with no additional phase development. The structural quality of GaN epitaxial layers has shown slight improvement on LT substrates over LN substrates, according to X-ray diffraction. Herein, we demonstrate AlGaN/GaN heterostructure devices on ferroelectric materials that will allow future development of multifunctional electrical and optical applications

  7. III-Nitrides growth and AlGaN/GaN heterostructures on ferroelectric materials

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Kyoung-Keun [Georgia Institute of Technology, School of Electrical and Computer Engineering, 777 Atlantic Dr., Atlanta, GA 30332 (United States); Namkoong, Gon [Old Dominion University, Department of Electrical and Computer Engineering, Norfolk, VA 23529 (United States); Madison, Shannon M. [Georgia Institute of Technology, School of Electrical and Computer Engineering, 777 Atlantic Dr., Atlanta, GA 30332 (United States); Ralph, Stephen E. [Georgia Institute of Technology, School of Electrical and Computer Engineering, 777 Atlantic Dr., Atlanta, GA 30332 (United States); Doolittle, W. Alan [Georgia Institute of Technology, School of Electrical and Computer Engineering, 777 Atlantic Dr., Atlanta, GA 30332 (United States)]. E-mail: alan.doolittle@ece.gatech.edu; Losurdo, Maria [Institute of Inorganic Methodologies and of Plasmas, IMIP-CNR, Department of Chemistry, University of Bari, via Orabona, 4 70126 Bari (Italy); Bruno, Giovanni [Institute of Inorganic Methodologies and of Plasmas, IMIP-CNR, Department of Chemistry, University of Bari, via Orabona, 4 70126 Bari (Italy); Cho, Hyung Koun [Department of Materials Science and Engineering, Sung Kyun Kwan University, Suwon 440-746 (Korea, Republic of)

    2007-06-15

    The growth of III-nitrides on the ferroelectric materials lithium niobate (LN) and lithium tantalate (LT) via molecular beam epitaxy (MBE) using rf plasma source has been investigated. We have found that gallium nitride (GaN) epitaxial layers have a crystalline relationship with lithium niobate (tantalate) as follows: (0 0 0 1) GaN || (0 0 0 1) LN (LT) with [10-10] GaN || [11-20] LN (LT). The surface stability of LN and LT substrates has been monitored by in situ spectroscopic ellipsometry in the vacuum chamber. Three different temperature zones have been discerned; surface degas and loss of OH group (100-350 deg. C); surface segregation/accumulation of Li and O-species (400-700 deg. C); surface evaporation of O-species and Li desorption (over 750 deg. C). However, LT shows only surface degassing in the range of 100-800 deg. C. Therefore, congruent LN substrates were chemically unstable at the growth temperature of 550-650 deg. C, and therefore developed an additional phase of Li-deficient lithium niobate (LiNb{sub 3}O{sub 8}) along with lithium niobate (LiNbO{sub 3}), confirmed by X-ray diffraction. On the other hand, LT showed better chemical stability at these temperatures, with no additional phase development. The structural quality of GaN epitaxial layers has shown slight improvement on LT substrates over LN substrates, according to X-ray diffraction. Herein, we demonstrate AlGaN/GaN heterostructure devices on ferroelectric materials that will allow future development of multifunctional electrical and optical applications.

  8. Polarization Switching and Light-Enhanced Piezoelectricity in Lead Halide Perovskites.

    Science.gov (United States)

    Coll, Mariona; Gomez, Andrés; Mas-Marza, Elena; Almora, Osbel; Garcia-Belmonte, Germà; Campoy-Quiles, Mariano; Bisquert, Juan

    2015-04-16

    We investigate the ferroelectric properties of photovoltaic methylammonium lead halide CH3NH3PbI3 perovskite using piezoelectric force microscopy (PFM) and macroscopic polarization methods. The electric polarization is clearly observed by amplitude and phase hysteresis loops. However, the polarization loop decreases as the frequency is lowered, persisting for a short time only, in the one second regime, indicating that CH3NH3PbI3 does not exhibit permanent polarization at room temperature. This result is confirmed by macroscopic polarization measurement based on a standard capacitive method. We have observed a strong increase of piezoelectric response under illumination, consistent with the previously reported giant photoinduced dielectric constant at low frequencies. We speculate that an intrinsic charge transfer photoinduced dipole in the perovskite cage may lie at the origin of this effect.

  9. Off-center displacements of Ti ions in oxide ferroelectrics and a gigantic photo-induced dielectric constant of quantum paraelectric perovskite oxides in the electron-lattice theory

    International Nuclear Information System (INIS)

    Konsin, P; Sorkin, B

    2005-01-01

    In this work we investigate the coupling of the F 1u vibrations with the actual electronic states of BO 6 n- cluster in ABO 3 ferrorelectric-oxides. This coupling leads to the dynamical covalency hybridization of B(Ti,Ta,Nb) and oxygen electronic states. It is shown that at fulfilment of definite criteria the free energy at T = 0, the adiabatic potential of BO 6 n- cluster have the following configurations: (1) one maximum at x 0 = y 0 = z 0 = 0 (ferroelectric instability); (2) eight minima in the points vertical bar x 0 vertical bar = vertical bar y 0 vertical bar = vertical bar z 0 vertical bar = y 0 ; (3) twelve saddle points at vertical bar p vertical bar = vertical bar q vertical bar ≠ 0, r = 0 (p, q, r = x, y, z) with a maximum in the r cross-section and minima along p and q. We show that the photo-induced changes of local ferroelectric distortions can take place. A gigantic enhancement of the dielectric constant by UV-light illumination is calculated in the electron-lattice theory in quantum paraelectrics of perovskite oxides, such as SrTiO 3 and KTaO 3 , under a weak DC electric field. The temperature dependence of the gigantic real part of the dielectric constant ε UVDC of SrTi 16 O 3 under both UV-light and DC electric fields is calculated in satisfactory agreement with the experiment

  10. Incipient ferroelectric to a possible ferroelectric transition in Te4+ doped calcium copper titanate (CaCu3Ti4O12 ceramics at low temperature as evidenced by Raman and dielectric spectroscopy

    Directory of Open Access Journals (Sweden)

    Nabadyuti Barman

    2017-03-01

    Full Text Available Partial replacement of Ti4+ by Te4+ ions in calcium copper titanate lattice improved its dielectric behaviour mostly due to cubic-to-tetragonal structural transformation and associated distortion in TiO6 octahedra. The relative permittivity values (23–30 x 103 of Te4+ doped ceramics is more than thrice that of un-doped ceramics (8 x 103 at 1 kHz. A decreasing trend in relative permittivity with increasing temperature (50–300 K is observed for all the samples. Barrett’s formula, as a signature of incipient ferroelectricity, is invoked to rationalize the relative permittivity variation as a function of temperature. A systematic investigation supported by temperature dependent Raman studies reveal a possible ferroelectric transition in Te4+ doped ceramic samples below 120 K. The possible ferroelectric transition is attributed to the interactions between quasi-local vibrations associated with the micro-clusters comprising TiO6 and TeO6 structural units and indirect dipole-dipole interactions of off-center B–cations (Ti4+ and Te4+ in double perovskite lattice.

  11. Effects of ferroelectric-poling-induced strain on the electronic transport and magnetic properties of (001)- and (111)-oriented La{sub 0.5}Ba{sub 0.5}MnO{sub 3} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Li, X.Y. [Department of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing 210094 (China); State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); Zheng, M.; Zhu, Q.X.; Yang, M.M.; Li, X.M.; Shi, X. [State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); Yuan, G.L., E-mail: yuanguoliang@mail.njust.edu.cn [Department of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing 210094 (China); Wang, Y.; Chan, H.L.W. [Department of Applied Physics, The Hong Kong Polytechnic University, Hong Kong (China); Li, X.G. [Hefei National Laboratory for Physical Sciences at Microscale and Department of Physics, University of Science and Technology of China, Hefei 230026 (China); Luo, H.S. [State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); Zheng, R.K., E-mail: zrk@ustc.edu [State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China)

    2014-04-01

    We epitaxially grew La{sub 0.5}Ba{sub 0.5}MnO{sub 3} (LBMO) films on (001)- and (111)-oriented ferroelectric single-crystal substrates and reduced the in-plane tensile strain of LBMO films by poling the ferroelectric substrates along the 〈001〉 or 〈111〉 direction. Upon poling, a large decrease in the resistance and a considerable increase in the magnetization, Curie temperature, and magnetoresistance were observed for the LBMO film, which are driven by interface strain coupling. Such strain effects can be significantly enhanced by the application of a magnetic field. An overall analysis of the findings reveals that the mutual interaction between the strain and the magnetic field is mediated by the electronic phase separation which is sensitive to both strain and magnetic field. Our findings highlight that the electronic phase separation is crucial in understanding the electric-field-manipulated strain effects in manganite film/ferroelectric crystal heterostructures. - Highlights: • La{sub 0.5}Ba{sub 0.5}MnO{sub 3} films were epitaxially grown on ternary ferroelectric single crystals. • Ferroelectric poling modifies the strain and physical properties of films. • Magnetic field enhances the strain effects of films. • Phase separation is crucial to understand the magnetic-field-tuned strain effect.

  12. Crystal Structure and Ferroelectric Properties of ε-Ga2O3 Films Grown on (0001)-Sapphire.

    Science.gov (United States)

    Mezzadri, Francesco; Calestani, Gianluca; Boschi, Francesco; Delmonte, Davide; Bosi, Matteo; Fornari, Roberto

    2016-11-21

    The crystal structure and ferroelectric properties of ε-Ga 2 O 3 deposited by low-temperature MOCVD on (0001)-sapphire were investigated by single-crystal X-ray diffraction and the dynamic hysteresis measurement technique. A thorough investigation of this relatively unknown polymorph of Ga 2 O 3 showed that it is composed of layers of both octahedrally and tetrahedrally coordinated Ga 3+ sites, which appear to be occupied with a 66% probability. The refinement of the crystal structure in the noncentrosymmetric space group P6 3 mc pointed out the presence of uncompensated electrical dipoles suggesting ferroelectric properties, which were finally demonstrated by independent measurements of the ferroelectric hysteresis. A clear epitaxial relation is observed with respect to the c-oriented sapphire substrate, with the Ga 2 O 3 [10-10] direction being parallel to the Al 2 O 3 direction [11-20], yielding a lattice mismatch of about 4.1%.

  13. Perovskite Oxide Thin Film Growth, Characterization, and Stability

    Science.gov (United States)

    Izumi, Andrew

    Studies into a class of materials known as complex oxides have evoked a great deal of interest due to their unique magnetic, ferroelectric, and superconducting properties. In particular, materials with the ABO3 perovskite structure have highly tunable properties because of the high stability of the structure, which allows for large scale doping and strain. This also allows for a large selection of A and B cations and valences, which can further modify the material's electronic structure. Additionally, deposition of these materials as thin films and superlattices through techniques such as pulsed laser deposition (PLD) results in novel properties due to the reduced dimensionality of the material. The novel properties of perovskite oxide heterostructures can be traced to a several sources, including chemical intermixing, strain and defect formation, and electronic reconstruction. The correlations between microstructure and physical properties must be investigated by examining the physical and electronic structure of perovskites in order to understand this class of materials. Some perovskites can undergo phase changes due to temperature, electrical fields, and magnetic fields. In this work we investigated Nd0.5Sr 0.5MnO3 (NSMO), which undergoes a first order magnetic and electronic transition at T=158K in bulk form. Above this temperature NSMO is a ferromagnetic metal, but transitions into an antiferromagnetic insulator as the temperature is decreased. This rapid transition has interesting potential in memory devices. However, when NSMO is deposited on (001)-oriented SrTiO 3 (STO) or (001)-oriented (LaAlO3)0.3-(Sr 2AlTaO6)0.7 (LSAT) substrates, this transition is lost. It has been reported in the literature that depositing NSMO on (110)-oriented STO allows for the transition to reemerge due to the partial epitaxial growth, where the NSMO film is strained along the [001] surface axis and partially relaxed along the [11¯0] surface axis. This allows the NSMO film enough

  14. Ferroic properties in bi-component perovskites: artificial superlattices and naturally forming compounds

    International Nuclear Information System (INIS)

    Saha-Dasgupta, T

    2014-01-01

    The use of four different metal cations in a bi-component perovskite ABO 3 structure with 50 : 50 substitution at A sublattice as well as B sublattice, opens up the door for materials designing, with the aim to improve ferroic properties. This can be achieved following two different routes; one using the concept of artificially grown superlattices with alternating layers of ABO 3 and A′B′O 3 perovskites in a periodic set-up and another, through synthesis of naturally grown bulk double perovskites with ordered arrangement of A and A′ cations, simultaneously with that of B and B′ cations. The tremendous progress in layered deposition techniques as well as advances in solid state chemistry methods, has made both routes equally plausible and an area of much activity. This review summarizes some of the recent progress in this field, with a special emphasis on two computational studies, (i) one on ultra-thin 1–1 superlattices built out of paraelectric and ferroelectric components, showing tunable piezoelectric properties, and (ii) another on CrOs-based double perovskites which show multiferroic behavior, achieved through layered ordering of A and A′ cations. (topical review)

  15. CaTiO.sub.3 Interfacial template structure on semiconductor-based material and the growth of electroceramic thin-films in the perovskite class

    Science.gov (United States)

    McKee, Rodney Allen; Walker, Frederick Joseph

    1998-01-01

    A structure including a film of a desired perovskite oxide which overlies and is fully commensurate with the material surface of a semiconductor-based substrate and an associated process for constructing the structure involves the build up of an interfacial template film of perovskite between the material surface and the desired perovskite film. The lattice parameters of the material surface and the perovskite of the template film are taken into account so that during the growth of the perovskite template film upon the material surface, the orientation of the perovskite of the template is rotated 45.degree. with respect to the orientation of the underlying material surface and thereby effects a transition in the lattice structure from fcc (of the semiconductor-based material) to the simple cubic lattice structure of perovskite while the fully commensurate periodicity between the perovskite template film and the underlying material surface is maintained. The film-growth techniques of the invention can be used to fabricate solid state electrical components wherein a perovskite film is built up upon a semiconductor-based material and the perovskite film is adapted to exhibit ferroelectric, piezoelectric, pyroelectric, electro-optic or large dielectric properties during use of the component.

  16. Structural evolution of epitaxial SrCoO{sub x} films near topotactic phase transition

    Energy Technology Data Exchange (ETDEWEB)

    Jeen, Hyoungjeen [Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States); Department of Physics, Pusan National University, Busan, 609735 (Korea, Republic of); Lee, Ho Nyung, E-mail: hnlee@ornl.gov [Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States)

    2015-12-15

    Control of oxygen stoichiometry in complex oxides via topotactic phase transition is an interesting avenue to not only modifying the physical properties, but utilizing in many energy technologies, such as energy storage and catalysts. However, detailed structural evolution in the close proximity of the topotactic phase transition in multivalent oxides has not been much studied. In this work, we used strontium cobaltites (SrCoO{sub x}) epitaxially grown by pulsed laser epitaxy (PLE) as a model system to study the oxidation-driven evolution of the structure, electronic, and magnetic properties. We grew coherently strained SrCoO{sub 2.5} thin films and performed post-annealing at various temperatures for topotactic conversion into the perovskite phase (SrCoO{sub 3-δ}). We clearly observed significant changes in electronic transport, magnetism, and microstructure near the critical temperature for the topotactic transformation from the brownmillerite to the perovskite phase. Nevertheless, the overall crystallinity was well maintained without much structural degradation, indicating that topotactic phase control can be a useful tool to control the physical properties repeatedly via redox reactions.

  17. Granular and layered ferroelectric–ferromagnetic thin-film nanocomposites as promising materials with high magnetotransmission effect

    Energy Technology Data Exchange (ETDEWEB)

    Akbashev, A.R. [Department of Materials Science, Moscow State University, 119992 Moscow (Russian Federation); Telegin, A.V., E-mail: telegin@imp.uran.ru [M.N. Miheev Institute of Metal Physics of Ural Branch of RAS, 620990 Ekaterinburg (Russian Federation); Kaul, A.R. [Department of Chemistry, Moscow State University, 119992 Moscow (Russian Federation); Sukhorukov, Yu.P. [M.N. Miheev Institute of Metal Physics of Ural Branch of RAS, 620990 Ekaterinburg (Russian Federation)

    2015-06-15

    Epitaxial thin films of granular and layered nanocomposites consisting of ferromagnetic perovskite Pr{sub 1–x}Sr{sub x}MnO{sub 3} and ferroelectric hexagonal LuMnO{sub 3} were grown on ZrO{sub 2}(Y{sub 2}O{sub 3}) substrates using metal-organic chemical vapor deposition (MOCVD). A self-organized growth of the granular composite took place in situ as a result of phase separation of the Pr–Sr–Lu–Mn–O system into the perovskite and hexagonal phases. Optical transmission measurements revealed a large negative magnetotransmission effect in the layered nanocomposite over a wide spectral and temperature range. The granular nanocomposite unexpectedly showed an even larger, but positive, magnetotransmission effect at room temperature. - Highlights: • Thin-film ferromagnetic–ferroelectric nanocomposites have been prepared by MOCVD. • Giant change of optical transparency of nanocomposites in magnetic field was detected. • Positive magnetotransmission in the granular nanocomposite was discovered in the IR. • Negative magnetotransmission in the layered nanocomposite was revealed in the IR. • Ferroelectric–ferromangetic nanocomposite is a promising material for optoelectronics.

  18. Granular and layered ferroelectric–ferromagnetic thin-film nanocomposites as promising materials with high magnetotransmission effect

    International Nuclear Information System (INIS)

    Akbashev, A.R.; Telegin, A.V.; Kaul, A.R.; Sukhorukov, Yu.P.

    2015-01-01

    Epitaxial thin films of granular and layered nanocomposites consisting of ferromagnetic perovskite Pr 1–x Sr x MnO 3 and ferroelectric hexagonal LuMnO 3 were grown on ZrO 2 (Y 2 O 3 ) substrates using metal-organic chemical vapor deposition (MOCVD). A self-organized growth of the granular composite took place in situ as a result of phase separation of the Pr–Sr–Lu–Mn–O system into the perovskite and hexagonal phases. Optical transmission measurements revealed a large negative magnetotransmission effect in the layered nanocomposite over a wide spectral and temperature range. The granular nanocomposite unexpectedly showed an even larger, but positive, magnetotransmission effect at room temperature. - Highlights: • Thin-film ferromagnetic–ferroelectric nanocomposites have been prepared by MOCVD. • Giant change of optical transparency of nanocomposites in magnetic field was detected. • Positive magnetotransmission in the granular nanocomposite was discovered in the IR. • Negative magnetotransmission in the layered nanocomposite was revealed in the IR. • Ferroelectric–ferromangetic nanocomposite is a promising material for optoelectronics

  19. Research Update: Behind the high efficiency of hybrid perovskite solar cells

    Directory of Open Access Journals (Sweden)

    Azhar Fakharuddin

    2016-09-01

    Full Text Available Perovskite solar cells (PSCs marked tremendous progress in a short period of time and offer bright hopes for cheap solar electricity. Despite high power conversion efficiency >20%, its poor operational stability as well as involvement of toxic, volatile, and less-abundant materials hinders its practical deployment. The fact that degradation and toxicity are typically observed in the most successful perovskite involving organic cation and toxic lead, i.e., CH3NH3PbX3, requires a deep understanding of their role in photovoltaic performance in order to envisage if a non-toxic, stable yet highly efficient device is feasible. Towards this, we first provide an overview of the basic chemistry and physics of halide perovskites and its correlation with its extraordinary properties such as crystal structure, bandgap, ferroelectricity, and electronic transport. We then discuss device related aspects such as the various device designs in PSCs and role of interfaces in origin of PV parameters particularly open circuit voltage, various film processing methods and their effect on morphology and characteristics of perovskite films, and the origin and elimination of hysteresis and operational stability in these devices. We then identify future perspectives for stable and efficient PSCs for practical deployment.

  20. Lanthanum titanium perovskite compound: Thin film deposition and high frequency dielectric characterization

    International Nuclear Information System (INIS)

    Le Paven, C.; Lu, Y.; Nguyen, H.V.; Benzerga, R.; Le Gendre, L.; Rioual, S.; Benzegoutta, D.; Tessier, F.; Cheviré, F.

    2014-01-01

    Perovskite lanthanum titanium oxide thin films were deposited on (001) MgO, (001) LaAlO 3 and Pt(111)/TiO 2 /SiO 2 /(001)Si substrates by RF magnetron sputtering, using a La 2 Ti 2 O 7 homemade target sputtered under oxygen reactive plasma. The films deposited at 800 °C display a crystalline growth different than those reported on monoclinic ferroelectric La 2 Ti 2 O 7 films. X-ray photoelectron spectroscopy analysis shows the presence of titanium as Ti 4+ ions, with no trace of Ti 3+ , and provides a La/Ti ratio of 1.02. The depositions being performed from a La 2 Ti 2 O 7 target under oxygen rich plasma, the same composition (La 2 Ti 2 O 7 ) is proposed for the deposited films, with an unusual orthorhombic cell and Cmc2 1 space group. The films have a textured growth on MgO and Pt/Si substrates, and are epitaxially grown on LaAlO 3 substrate. The dielectric characterization displays stable values of the dielectric constant and of the losses in the frequency range [0.1–20] GHz. No variation of the dielectric constant has been observed when a DC electric field up to 250 kV/cm was applied, which does not match a classical ferroelectric behavior at high frequencies and room temperature for the proposed La 2 Ti 2 O 7 orthorhombic phase. At 10 GHz and room temperature, the dielectric constant of the obtained La 2 Ti 2 O 7 films is ε ∼ 60 and the losses are low (tanδ < 0.02). - Highlights: • Lanthanum titanium oxide films were deposited by reactive magnetron sputtering. • A La 2 Ti 2 O 7 chemical composition is proposed, with an unusual orthorhombic cell. • At 10 GHz, the dielectric losses are lower than 0.02. • No variation of the dielectric constant is observed under DC electric biasing

  1. Structural Consequences of Ferroelectric Nanolithography

    Energy Technology Data Exchange (ETDEWEB)

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

    2011-12-31

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

  2. RF magnetron sputtered La3+-modified PZT thin films: Perovskite phase stabilization and properties

    International Nuclear Information System (INIS)

    Singh, Ravindra; Goel, T.C.; Chandra, Sudhir

    2008-01-01

    In this work, we report the preparation of lanthanum-modified lead zirconate titanate (PLZT) thin films in pure perovskite phase by RF magnetron sputtering. Various deposition parameters such as target-to-substrate spacing, sputtering gas composition, deposition temperature, post-deposition annealing temperature and time have been optimized to obtain PLZT films in pure perovskite phase. The films prepared in pure argon at 100 W RF power without external substrate heating exhibit pure perovskite phase after rapid thermal annealing (RTA) at 700 deg. C for 5 min. The film prepared at 225 deg. C substrate temperature also exhibits pure perovskite phase after RTA at 700 deg. C for 2 min. SIMS depth profile performed on one of the pure perovskite films (RTA at 700 deg. C for 5 min) shows very good stoichiometric uniformity of all elements of PLZT. The surface morphology of the films was examined using SEM and AFM. The dielectric, ferroelectric and electrical properties of the pure perovskite films were also investigated in detail. The remanent polarization for the films annealed at 700 deg. C for 5 and 2 min were found to be 15 and 13.5 μC cm -2 , respectively. Both the films have high DC resistivity of the order of 10 11 Ω cm at the electric field of ∼80 kV cm -1

  3. Crystallography and Growth of Epitaxial Oxide Films for Fundamental Studies of Cathode Materials Used in Advanced Li-Ion Batteries

    Directory of Open Access Journals (Sweden)

    Leonid A. Bendersky

    2017-05-01

    Full Text Available Li-ion battery systems, synthesized as epitaxial thin films, can provide powerful insights into their electrochemical processes. Crystallographic analysis shows that many important cathode oxides have an underlying similarity: their structures can be considered as different ordering schemes of Li and transition metal ions within a pseudo-cubic sublattice of oxygen anions arranged in a face-center cubic (FCC fashion. This oxygen sublattice is compatible with SrTiO3 and similar perovskite oxides, thus perovskites can be used as supporting substrates for growing epitaxial cathode films. The predicted epitaxial growth and crystallographic relations were experimentally verified for different oxide films deposited by pulsed laser deposition (PLD on SrTiO3 or SrRuO3/SrTiO3 of different orientations. The results based on cross-sectional high-resolution TEM of the following films are presented in the paper: (a trigonal LiCoO2; (b orthorhombic LiMnO2; (c monoclinic Li2MnO3; (d compositionally-complex monoclinic Li1.2Mn0.55Ni0.15Co0.1O2. All results demonstrated the feasibility of epitaxial growth for these materials, with the growth following the predicted cube-on-cube orientation relationship between the cubic and pseudo-cubic oxygen sublattices of a substrate and a film, respectively.

  4. Ferroelectric and piezoelectric properties of epitaxial PZT films and devices on silicon

    NARCIS (Netherlands)

    Nguyen, Duc Minh

    2010-01-01

    In this thesis, the integration of lead zirconate titanate Pb(Zr,Ti)O3 (PZT) thin films into piezoelectric microelectromechanical systems (MEMS) based on silicon is studied. In these structures, all epitaxial oxide layers (thin film/electrode/buffer-layer(s)) were deposited by pulsed laser

  5. Formation of (111) orientation-controlled ferroelectric orthorhombic HfO{sub 2} thin films from solid phase via annealing

    Energy Technology Data Exchange (ETDEWEB)

    Mimura, Takanori; Katayama, Kiliha [Department of Innovative and Engineered Materials, Tokyo Institute of Technology, Yokohama 226-8502 (Japan); Shimizu, Takao [Materials Research Center for Element Strategy, Tokyo Institute of Technology, Yokohama 226-8503 (Japan); Uchida, Hiroshi [Department of Materials and Life Sciences, Sophia University, Tokyo 102-8554 (Japan); Kiguchi, Takanori; Akama, Akihiro; Konno, Toyohiko J. [Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Sakata, Osami [Synchrotron X-ray Station at SPring-8 and Synchrotron X-ray Group, National Institute for Materials Science, Sayo, Hyogo 679-5148 (Japan); Funakubo, Hiroshi, E-mail: funakubo.h.aa@m.titech.ac.jp [Department of Innovative and Engineered Materials, Tokyo Institute of Technology, Yokohama 226-8502 (Japan); Materials Research Center for Element Strategy, Tokyo Institute of Technology, Yokohama 226-8503 (Japan); School of Materials and Chemical Technology, Tokyo Institute of Technology, Yokohama 226-8502 (Japan)

    2016-08-01

    0.07YO{sub 1.5}-0.93HfO{sub 2} (YHO7) films were prepared on various substrates by pulse laser deposition at room temperature and subsequent heat treatment to enable a solid phase reaction. (111)-oriented 10 wt. % Sn-doped In{sub 2}O{sub 3}(ITO)//(111) yttria-stabilized zirconia, (111)Pt/TiO{sub x}/SiO{sub 2}/(001)Si substrates, and (111)ITO/(111)Pt/TiO{sub x}/SiO{sub 2}/(001)Si substrates were employed for film growth. In this study, X-ray diffraction measurements including θ–2θ measurements, reciprocal space mappings, and pole figure measurements were used to study the films. The film on (111)ITO//(111)yttria-stabilized zirconia was an (111)-orientated epitaxial film with ferroelectric orthorhombic phase; the film on (111)ITO/(111)Pt/TiO{sub x}/SiO{sub 2}/(001)Si was an (111)-oriented uniaxial textured film with ferroelectric orthorhombic phase; and no preferred orientation was observed for the film on the (111)Pt/TiO{sub x}/SiO{sub 2}/(001)Si substrate, which does not contain ITO. Polarization–hysteresis measurements confirmed that the films on ITO covered substrates had saturated ferroelectric hysteresis loops. A remanent polarization (P{sub r}) of 9.6 and 10.8 μC/cm{sup 2} and coercive fields (E{sub c}) of 1.9 and 2.0 MV/cm were obtained for the (111)-oriented epitaxial and uniaxial textured YHO7 films, respectively. These results demonstrate that the (111)-oriented ITO bottom electrodes play a key role in controlling the orientation and ferroelectricity of the phase formation of the solid films deposited at room temperature.

  6. Study of the structure and ferroelectric behavior of BaBi{sub 4-x}La{sub x}Ti{sub 4}O{sub 15} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Khokhar, Anita, E-mail: mails4anita@gmail.com; Sreenivas, K. [Department of Physics & Astrophysics, University of Delhi, Delhi-110 007 (India); Goyal, Parveen K. [Department of Physics, ARSD College, University of Delhi, Dhaula Kuan, New Delhi-110 021 (India); Thakur, O. P. [Electroceramics Group, Solid State Physics Laboratory, Lucknow Road, Delhi 110 054 (India)

    2015-06-24

    The structure and ferroelectric properties of Lanthanum substituted barium bismuth titanate BaBi{sub 4-x}La{sub x}Ti{sub 4}O{sub 15} (0 ≤ x ≤ 0.5) ceramics prepared by solid-state reaction method have been investigated. X-ray diffraction (XRD) confirms the formation of a single phase material. The distribution of lanthanum into the perovskite layers and (Bi{sub 2}O{sub 2}){sup 2+} layers of BaBi{sub 4}Ti{sub 4}O{sub 15} ceramics have been revealed through Raman spectroscopy. At lower value of x, it is seen that La{sup 3+} ions prefer to substitute A-site Bi{sup 3+} ions in the perovskite layers while for higher x values, La{sup 3+} ions get incorporated into the (Bi{sub 2}O{sub 2}){sup 2+} layers. A critical La content of x ∼ 0.2 in BaBi{sub 4-x}La{sub x}Ti{sub 4}O{sub 15} is seen to exhibit a large remnant polarization (P{sub r}) with low coercive field (E{sub c}). The improvement in the ferroelectric properties of La substituted BaBi{sub 4}Ti{sub 4}O{sub 15} ceramics has been explained in terms of changing oxygen vacancy concentration and structural relaxation. Tunable ferroelectric materials can be obtained by manipulating the doping amount of lanthanum ion.

  7. Influence of Fe{sup 3+} substitution on the dielectric and ferroelectric characteristics of Lead Indium Niobate

    Energy Technology Data Exchange (ETDEWEB)

    Divya, A.S.; Kumar, V., E-mail: vkumar10@yahoo.com

    2015-07-15

    Highlights: • Prepared phase-pure Fe{sup 3+}-substituted Lead Indium Niobate, Pb[(In{sub 0.50−x}Fe{sub x})Nb{sub 0.50}]O{sub 3} by sol–gel method. • Spontaneous Relaxor (R) → Ferroelectric (FE) transition observed for the composition with x = 0.20. • Local structural rearrangement responsible for R → FE transition has been confirmed by Raman spectroscopy. - Abstract: Lead Indium Niobate, Pb(In{sub 0.50}Nb{sub 0.50})O{sub 3} (PIN) is a complex perovskite that exhibits Relaxor (R) characteristics. In this study, we report the synthesis of phase-pure compositions in the system Pb[(In{sub 0.50−x}Fe{sub x})Nb{sub 0.50}]O{sub 3} by sol–gel method and discuss the influence of isovalent substitution of Indium by Iron on the dielectric and ferroelectric characteristics. Spontaneous transition to the Ferroelectric (FE) phase has been observed for the composition having x = 0.20. Local structural rearrangements responsible for R → FE transition have also been studied by Raman spectroscopy and are discussed in detail.

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

    Science.gov (United States)

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

    2018-04-01

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

  9. Ferroelectric domain structures in -oriented K0.15Na0.85NbO3 lead-free single crystal

    Directory of Open Access Journals (Sweden)

    Yan Chen

    2015-03-01

    Full Text Available In this work, ferroelectric domain structures of -oriented K0.15Na0.85NbO3 single crystal are characterized. Transmission electron microscopy (TEM observation revealed high-density of laminate domain structures in the crystal and the lattices of the neighboring domains are found to be twisted in a small angle. Superlattice diffraction spots of 1 2 { eeo } and 1 2 { ooe } in electron diffraction patterns are observed in the crystal, revealing the a+a+c− tilting of oxygen octahedral in the perovskite structure. The piezoresponse of domains and in-situ poling responses of K0.15Na0.85NbO3 crystal are observed by piezoresponse force microscopy (PFM, and the results assure its good ferroelectric properties.

  10. Ferroelectric and octahedral tilt twin disorder and the lead-free piezoelectric, sodium potassium niobate system

    International Nuclear Information System (INIS)

    Schiemer, Jason; Withers, Ray L.; Liu, Yun; Yi, Zhiguo

    2012-01-01

    Using electron diffraction, trends in the local structural behaviour of the K x Na 1−x NbO 3 (KNN x) ‘solid solution’ system are investigated and interpreted using an order/disorder based theoretical framework. At room temperature, electron diffraction shows a single plane of transverse polarised, diffuse intensity perpendicular to [0 1 0] p ⁎ (p for parent sub-structure) across the entire phase diagram, indicative of ferroelectric disorder along the [0 1 0] p direction co-existing with long range ferroelectric order along the orthogonal [1 0 0] p and [0 0 1] p directions. An additional characteristic pattern of diffuse scattering is also observed, involving rods of diffuse intensity running along the [1 0 0] p * and [0 0 1] p * directions of the perovskite sub-structure and indicative of octahedral tilt disorder about the [1 0 0] p and [0 0 1] p axes co-existing with long range ordered octahedral tilting around the [0 1 0] p direction. A possible crystal chemical explanation for the existence of this latter octahedral tilt disorder is explored through bond valence sum calculations. The possible influence of both types of disorder on the previously refined, room temperature space group/s and average crystal structure/s is examined. - Graphical abstract: [−3,0.−1]p zone axis EDP of K 0.46 Na 0.54 NbO 3 indexed according to both the relevant Pcm21 space groups (no subscripts) and the parent perovskite subcell (denoted by a subscript p). Highlights: ► Characterises ferroelectric and octahedral tilt disorder in the KNN solid solution. ► Discusses the possible driving forces for this disorder. ► Discusses the implications of this disorder for physical properties. ► Discusses the effects of this disorder on powder diffraction data.

  11. Anomalous photovoltaic effect in organic-inorganic hybrid perovskite solar cells.

    Science.gov (United States)

    Yuan, Yongbo; Li, Tao; Wang, Qi; Xing, Jie; Gruverman, Alexei; Huang, Jinsong

    2017-03-01

    Organic-inorganic hybrid perovskites (OIHPs) have been demonstrated to be highly successful photovoltaic materials yielding very-high-efficiency solar cells. We report the room temperature observation of an anomalous photovoltaic (APV) effect in lateral structure OIHP devices manifested by the device's open-circuit voltage ( V OC ) that is much larger than the bandgap of OIHPs. The persistent V OC is proportional to the electrode spacing, resembling that of ferroelectric photovoltaic devices. However, the APV effect in OIHP devices is not caused by ferroelectricity. The APV effect can be explained by the formation of tunneling junctions randomly dispersed in the polycrystalline films, which allows the accumulation of photovoltage at a macroscopic level. The formation of internal tunneling junctions as a result of ion migration is visualized with Kelvin probe force microscopy scanning. This observation points out a new avenue for the formation of large and continuously tunable V OC without being limited by the materials' bandgap.

  12. Existence region of phases of laminated perovskite-like structre of A/sub 2/B/sub 2/O/sub 7/ composition

    Energy Technology Data Exchange (ETDEWEB)

    Sych, A M; Titov, Yu A [Kievskij Gosudarstvennyj Univ. (Ukrainian SSR)

    1982-06-01

    Generalizing the known data for ferroelectrics of A/sub 2/B/sub 2/O/sub 7/ type (LnTi/sub 2/O/sub 7/, in particular) geometrical conditions of existence of laminated perovskite-like structure are determined: 0.603 A < anti Rsub(Bsup(6)) <= 0.665 A, anti Rsub(Asup(12))/Rsub(Bsup(6)) > 2.045. The geometrical conditions presented are necessary but not sufficient. A supposition is made that phases GaLnTiNbO/sub 7/ (Ln = Pr - Eu) and CaLnTiTaO/sub 7/ (Ln = La - Eu) with laminated perovskite-like structure can be prepared under high pressures.

  13. Coexistence of room temperature ferroelectricity and ferrimagnetism in multiferroic BiFeO3-Bi0.5Na0.5TiO3 solid solution

    International Nuclear Information System (INIS)

    Tian, Z.M.; Wang, C.H.; Yuan, S.L.; Wu, M.S.; Ma, Z.Z.; Duan, H.N.; Chen, L.

    2011-01-01

    Highlights: → In this study, the coexistence of ferroelectrics and ferrimagnetism have been observed at room temperature for the (1 - x)BiFeO 3 -xBi 0.5 Na 0.5 TiO 3 (x = 0.37) solid solutions. → X-ray diffraction and Raman spectroscopy measurements show a single-phase perovskite structure with no impurities identified. → A magnetic transition from paramagnetic (PM) to ferrimagnetic (Ferri) ordering is observed for the solution with Curie temperature T C ∼ 330 K. - Abstract: The structure, ferroelectric and magnetic properties of (1 - x)BiFeO 3 -xBi 0.5 Na 0.5 TiO 3 (x = 0.37) solid solution fabricated by a sol-gel method have been investigated. X-ray diffraction and Raman spectroscopy measurements show a single-phase perovskite structure with no impurities identified. Compared with pure BiFeO 3 , the coexistence of ferroelectricity and ferrimagnetism have been observed at room temperature for the solution with remnant polarization P r = 1.41 μC/cm 2 and remnant magnetization M r = 0.054 emu/g. Importantly, a magnetic transition from ferrimagnetic (FM) ordering to paramagnetic (PM) state is observed, with Curie temperature T C ∼ 330 K, being explained in terms of the suppression of cycloid spin configuration by the structural distortion.

  14. Controllable Photovoltaic Effect of Microarray Derived from Epitaxial Tetragonal BiFeO3 Films.

    Science.gov (United States)

    Lu, Zengxing; Li, Peilian; Wan, Jian-Guo; Huang, Zhifeng; Tian, Guo; Pan, Danfeng; Fan, Zhen; Gao, Xingsen; Liu, Jun-Ming

    2017-08-16

    Recently, the ferroelectric photovoltaic (FePV) effect has attracted great interest due to its potential in developing optoelectronic devices such as solar cell and electric-optical sensors. It is important for actual applications to realize a controllable photovoltaic process in ferroelectric-based materials. In this work, we prepared well-ordered microarrays based on epitaxially tetragonal BiFeO 3 (T-BFO) films by the pulsed laser deposition technique. The polarization-dependent photocurrent image was directly observed by a conductive atomic force microscope under ultraviolet illumination. By choosing a suitable buffer electrode layer and controlling the ferroelectric polarization in the T-BFO layer, we realized the manipulation of the photovoltaic process. Moreover, based on the analysis of the band structure, we revealed the mechanism of manipulating the photovoltaic process and attributed it to the competition between two key factors, i.e., the internal electric field caused by energy band alignments at interfaces and the depolarization field induced by the ferroelectric polarization in T-BFO. This work is very meaningful for deeply understanding the photovoltaic process of BiFeO 3 -based devices at the microscale and provides us a feasible avenue for developing data storage or logic switching microdevices based on the FePV effect.

  15. Topotactic phase transformation of the brownmillerite SrCoO2.5 to the perovskite SrCoO3- δ.

    Science.gov (United States)

    Jeen, H; Choi, W S; Freeland, J W; Ohta, H; Jung, C U; Lee, H N

    2013-07-19

    Pulsed laser epitaxy of brownmillerite SrCoO2.5 thin films and their phase transformation to the perovskite SrCoO3-δ are investigated. While the direct growth of the fully oxidized perovskite films is found to be an arduous task, filling some of oxygen vacancies into SrCoO2.5 by topotactic oxidation accompanies systematic evolution of electronic, magnetic, and thermoelectric properties, useful for many information and energy technologies. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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

    Science.gov (United States)

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

    2017-12-13

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

  17. Luminescent properties and energy transfer processes in Ce-Tb doped single crystalline film screens of Lu-based silicate, perovskite and garnet compounds

    Czech Academy of Sciences Publication Activity Database

    Zorenko, Y.; Gorbenko, V.; Savchyn, V.; Zorenko, T.; Martin, T.; Douissard, P.-A.; Nikl, Martin; Mareš, Jiří A.

    2013-01-01

    Roč. 56, Sept (2013), s. 415-419 ISSN 1350-4487 Institutional support: RVO:68378271 Keywords : single crystalline films * liquid phase epitaxy * perovskites * luminescence * scintillators Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.140, year: 2013

  18. Effect of thermal strain on the ferroelectric phase transition in polycrystalline Ba0.5Sr0.5TiO3 thin films studied by Raman spectroscopy

    International Nuclear Information System (INIS)

    Tenne, D.A.; Soukiassian, A.; Xi, X.X.; Taylor, T.R.; Hansen, P.J.; Speck, J.S.; York, R.A.

    2004-01-01

    We have applied Raman spectroscopy to study the influence of thermal strain on the vibrational properties of polycrystalline Ba 0.5 Sr 0.5 TiO 3 films. The films were grown by rf magnetron sputtering on Pt/SiO 2 surface using different host substrates: strontium titanate, sapphire, silicon, and vycor glass. These substrates provide a systematic change in the thermal strain while maintaining the same film microstructure. From the temperature dependence of the ferroelectric A 1 soft phonon intensity, the ferroelectric phase transition temperature, T C , was determined. We found that T C decreases with increasing tensile stress in the films. This dependence is different from the theoretical predictions for epitaxial ferroelectric films. The reduction of the ferroelectric transition temperature with increasing biaxial tensile strain is attributed to the suppression of in-plane polarization due to the small lateral grain size in the films

  19. Growth and luminescence properties of Pr3+-doped single crystalline films of garnets and perovskites

    International Nuclear Information System (INIS)

    Gorbenko, V.; Zorenko, Yu.; Savchyn, V.; Zorenko, T.; Pedan, A.; Shkliarskyi, V.

    2010-01-01

    Peculiarities of growth of single crystalline films (SCF) of Pr 3+ doped Y 3 Al 5 O 12 and Lu 3 Al 5 O 12 garnets and YAlO 3 and LuAlO 3 perovskites by the liquid phase epitaxy method from melt-solutions based on PbO-B 2 O 3 flux as well as luminescent and scintillation properties of these SCFs were studied in this work. Dependence the intensity of the Pr 3+ d-f and f-f-luminescence on the activator concentration and influence of Pb 2+ flux dopant on the light yield of SCFs of the mentioned garnets and perovskites were analyzed.

  20. Perovskite-based heterostructures integrating ferromagnetic-insulating La0.1Bi0.9MnO3

    Science.gov (United States)

    Gajek, M.; Bibes, M.; Barthélémy, A.; Varela, M.; Fontcuberta, J.

    2005-05-01

    We report on the growth of thin films and heterostructures of the ferromagnetic-insulating perovskite La0.1Bi0.9MnO3. We show that the La0.1Bi0.9MnO3 perovskite grows single phased, epitaxially, and with a single out-of-plane orientation either on SrTiO3 substrates or onto strained La2/3Sr1/3MnO3 and SrRuO3 ferromagnetic-metallic buffer layers. We discuss the magnetic properties of the La0.1Bi0.9MnO3 films and heterostructures in view of their possible potential as magnetoelectric or spin-dependent tunneling devices.

  1. Two-dimensional ferroelectrics

    Energy Technology Data Exchange (ETDEWEB)

    Blinov, L M; Fridkin, Vladimir M; Palto, Sergei P [A.V. Shubnikov Institute of Crystallography, Russian Academy of Sciences, Moscow, Russian Federaion (Russian Federation); Bune, A V; Dowben, P A; Ducharme, Stephen [Department of Physics and Astronomy, Behlen Laboratory of Physics, Center for Materials Research and Analysis, University of Nebraska-Linkoln, Linkoln, NE (United States)

    2000-03-31

    The investigation of the finite-size effect in ferroelectric crystals and films has been limited by the experimental conditions. The smallest demonstrated ferroelectric crystals had a diameter of {approx}200 A and the thinnest ferroelectric films were {approx}200 A thick, macroscopic sizes on an atomic scale. Langmuir-Blodgett deposition of films one monolayer at a time has produced high quality ferroelectric films as thin as 10 A, made from polyvinylidene fluoride and its copolymers. These ultrathin films permitted the ultimate investigation of finite-size effects on the atomic thickness scale. Langmuir-Blodgett films also revealed the fundamental two-dimensional character of ferroelectricity in these materials by demonstrating that there is no so-called critical thickness; films as thin as two monolayers (1 nm) are ferroelectric, with a transition temperature near that of the bulk material. The films exhibit all the main properties of ferroelectricity with a first-order ferroelectric-paraelectric phase transition: polarization hysteresis (switching); the jump in spontaneous polarization at the phase transition temperature; thermal hysteresis in the polarization; the increase in the transition temperature with applied field; double hysteresis above the phase transition temperature; and the existence of the ferroelectric critical point. The films also exhibit a new phase transition associated with the two-dimensional layers. (reviews of topical problems)

  2. Structural analysis of LaVO3 thin films under epitaxial strain

    Directory of Open Access Journals (Sweden)

    H. Meley

    2018-04-01

    Full Text Available Rare earth vanadate perovskites exhibit a phase diagram in which two different types of structural distortions coexist: the strongest, the rotation of the oxygen octahedra, comes from the small tolerance factor of the perovskite cell (t = 0.88 for LaVO3 and the smaller one comes from inter-site d-orbital interactions manifesting as a cooperative Jahn-Teller effect. Epitaxial strain acts on octahedral rotations and crystal field symmetry to alter this complex lattice-orbit coupling. In this study, LaVO3 thin film structures have been investigated by X-ray diffraction and scanning transmission electron microscopy. The analysis shows two different orientations of octahedral tilt patterns, as well as two distinct temperature behaviors, for compressive and tensile film strain states. Ab initio calculations capture the strain effect on the tilt pattern orientation in agreement with experimental data.

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

    Science.gov (United States)

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

    2017-07-07

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

  4. Molecular beam epitaxy of three-dimensional Dirac material Sr3PbO

    Science.gov (United States)

    Samal, D.; Nakamura, H.; Takagi, H.

    2016-07-01

    A series of anti-perovskites including Sr3PbO are recently predicted to be a three-dimensional Dirac material with a small mass gap, which may be a topological crystalline insulator. Here, we report the epitaxial growth of Sr3PbO thin films on LaAlO3 using molecular beam epitaxy. X-ray diffraction indicates (001) growth of Sr3PbO, where [110] of Sr3PbO matches [100] of LaAlO3. Measurements of the Sr3PbO films with parylene/Al capping layers reveal a metallic conduction with p-type carrier density of ˜1020 cm-3. The successful growth of high quality Sr3PbO film is an important step for the exploration of its unique topological properties.

  5. Tunable strain effect and ferroelectric field effect on the electronic transport properties of La0.5Sr0.5CoO3 thin films

    Science.gov (United States)

    Zhu, Q. X.; Wang, W.; Zhao, X. Q.; Li, X. M.; Wang, Y.; Luo, H. S.; Chan, H. L. W.; Zheng, R. K.

    2012-05-01

    Tensiled La0.5Sr0.5CoO3 (LSCO) thin films were epitaxially grown on piezoelectric 0.67Pb (Mg1/3Nb2/3)O3-0.33PbTiO3 (PMN-PT) single-crystal substrates. Due to the epitaxial nature of the interface, the lattice strain induced by ferroelectric poling or the converse piezoelectric effect in the PMN-PT substrate is effectively transferred to the LSCO film and thus reduces the tensile strain of the film, giving rise to a decrease in the resistivity of the LSCO film. We discuss these strain effects within the framework of the spin state transition of Co3+ ions and modification of the electronic bandwidth that is relevant to the induced strain. By simultaneously measuring the strain and the resistivity, quantitative relationship between the resistivity and the strain was established for the LSCO film. Both theoretical calculation and experimental results demonstrate that the ferroelectric field effect at room temperature in the LSCO/PMN-PT field-effect transistor is minor and could be neglected. Nevertheless, with decreasing temperature, the ferroelectric field effect competes with the strain effect and plays a more and more important role in influencing the electronic transport properties of the LSCO film, which we interpreted as due to the localization of charge carriers at low temperature.

  6. Dielectric and ferroelectric properties of strain-relieved epitaxial lead-free KNN-LT-LS ferroelectric thin films on SrTiO3 substrates

    Science.gov (United States)

    Abazari, M.; Akdoǧan, E. K.; Safari, A.

    2008-05-01

    We report the growth of single-phase (K0.44,Na0.52,Li0.04)(Nb0.84,Ta0.10,Sb0.06)O3 thin films on SrRuO3 coated ⟨001⟩ oriented SrTiO3 substrates by using pulsed laser deposition. Films grown at 600°C under low laser fluence exhibit a ⟨001⟩ textured columnar grained nanostructure, which coalesce with increasing deposition temperature, leading to a uniform fully epitaxial highly stoichiometric film at 750°C. However, films deposited at lower temperatures exhibit compositional fluctuations as verified by Rutherford backscattering spectroscopy. The epitaxial films of 400-600nm thickness have a room temperature relative permittivity of ˜750 and a loss tangent of ˜6% at 1kHz. The room temperature remnant polarization of the films is 4μC /cm2, while the saturation polarization is 7.1μC/cm2 at 24kV/cm and the coercive field is ˜7.3kV/cm. The results indicate that approximately 50% of the bulk permittivity and 20% of bulk spontaneous polarization can be retained in submicron epitaxial KNN-LT-LS thin film, respectively. The conductivity of the films remains to be a challenge as evidenced by the high loss tangent, leakage currents, and broad hysteresis loops.

  7. Crossover from incoherent to coherent phonon scattering in epitaxial oxide superlattices.

    Science.gov (United States)

    Ravichandran, Jayakanth; Yadav, Ajay K; Cheaito, Ramez; Rossen, Pim B; Soukiassian, Arsen; Suresha, S J; Duda, John C; Foley, Brian M; Lee, Che-Hui; Zhu, Ye; Lichtenberger, Arthur W; Moore, Joel E; Muller, David A; Schlom, Darrell G; Hopkins, Patrick E; Majumdar, Arun; Ramesh, Ramamoorthy; Zurbuchen, Mark A

    2014-02-01

    Elementary particles such as electrons or photons are frequent subjects of wave-nature-driven investigations, unlike collective excitations such as phonons. The demonstration of wave-particle crossover, in terms of macroscopic properties, is crucial to the understanding and application of the wave behaviour of matter. We present an unambiguous demonstration of the theoretically predicted crossover from diffuse (particle-like) to specular (wave-like) phonon scattering in epitaxial oxide superlattices, manifested by a minimum in lattice thermal conductivity as a function of interface density. We do so by synthesizing superlattices of electrically insulating perovskite oxides and systematically varying the interface density, with unit-cell precision, using two different epitaxial-growth techniques. These observations open up opportunities for studies on the wave nature of phonons, particularly phonon interference effects, using oxide superlattices as model systems, with extensive applications in thermoelectrics and thermal management.

  8. High-throughput DFT calculations of formation energy, stability and oxygen vacancy formation energy of ABO3 perovskites

    Science.gov (United States)

    Emery, Antoine A.; Wolverton, Chris

    2017-10-01

    ABO3 perovskites are oxide materials that are used for a variety of applications such as solid oxide fuel cells, piezo-, ferro-electricity and water splitting. Due to their remarkable stability with respect to cation substitution, new compounds for such applications potentially await discovery. In this work, we present an exhaustive dataset of formation energies of 5,329 cubic and distorted perovskites that were calculated using first-principles density functional theory. In addition to formation energies, several additional properties such as oxidation states, band gap, oxygen vacancy formation energy, and thermodynamic stability with respect to all phases in the Open Quantum Materials Database are also made publicly available. This large dataset for this ubiquitous crystal structure type contains 395 perovskites that are predicted to be thermodynamically stable, of which many have not yet been experimentally reported, and therefore represent theoretical predictions. The dataset thus opens avenues for future use, including materials discovery in many research-active areas.

  9. Ferroelectric domain switching dynamics and memristive behaviors in BiFeO3-based magnetoelectric heterojunctions

    Science.gov (United States)

    Huang, Weichuan; Liu, Yukuai; Luo, Zhen; Hou, Chuangming; Zhao, Wenbo; Yin, Yuewei; Li, Xiaoguang

    2018-06-01

    The ferroelectric domain reversal dynamics and the corresponding resistance switching as well as the memristive behaviors in epitaxial BiFeO3 (BFO, ~150 nm) based multiferroic heterojunctions were systematically investigated. The ferroelectric domain reversal dynamics could be described by the nucleation-limited-switching model with the Lorentzian distribution of logarithmic domain-switching times. By engineering the domain states, multi and even continuously tunable resistances states, i.e. memristive states, could be non-volatilely achieved. The resistance switching speed can be as fast as 30 ns in the BFO-based multiferroic heterojunctions with a write voltage of ~20 V. By reducing the thickness of BFO, the La0.6Sr0.4MnO3/BFO (~5 nm)/La0.6Sr0.4MnO3 multiferroic tunnel junction (MFTJ) shows an even a quicker switching speed (20 ns) with a much lower operation voltage (~4 V). Importantly, the MFTJ exhibits a tunable interfacial magnetoelectric coupling related to the ferroelectric domain switching dynamics. These findings enrich the potential applications of multiferroic BFO based devices in high-speed, low-power, and high-density memories as well as future neuromorphic computational architectures.

  10. Local switching of two-dimensional superconductivity using the ferroelectric field effect

    Science.gov (United States)

    Takahashi, K. S.; Gabay, M.; Jaccard, D.; Shibuya, K.; Ohnishi, T.; Lippmaa, M.; Triscone, J.-M.

    2006-05-01

    Correlated oxides display a variety of extraordinary physical properties including high-temperature superconductivity and colossal magnetoresistance. In these materials, strong electronic correlations often lead to competing ground states that are sensitive to many parameters-in particular the doping level-so that complex phase diagrams are observed. A flexible way to explore the role of doping is to tune the electron or hole concentration with electric fields, as is done in standard semiconductor field effect transistors. Here we demonstrate a model oxide system based on high-quality heterostructures in which the ferroelectric field effect approach can be studied. We use a single-crystal film of the perovskite superconductor Nb-doped SrTiO3 as the superconducting channel and ferroelectric Pb(Zr,Ti)O3 as the gate oxide. Atomic force microscopy is used to locally reverse the ferroelectric polarization, thus inducing large resistivity and carrier modulations, resulting in a clear shift in the superconducting critical temperature. Field-induced switching from the normal state to the (zero resistance) superconducting state was achieved at a well-defined temperature. This unique system could lead to a field of research in which devices are realized by locally defining in the same material superconducting and normal regions with `perfect' interfaces, the interface being purely electronic. Using this approach, one could potentially design one-dimensional superconducting wires, superconducting rings and junctions, superconducting quantum interference devices (SQUIDs) or arrays of pinning centres.

  11. Nonvolatile ferroelectric memory based on PbTiO3 gated single-layer MoS2 field-effect transistor

    Science.gov (United States)

    Shin, Hyun Wook; Son, Jong Yeog

    2018-01-01

    We fabricated ferroelectric non-volatile random access memory (FeRAM) based on a field effect transistor (FET) consisting of a monolayer MoS2 channel and a ferroelectric PbTiO3 (PTO) thin film of gate insulator. An epitaxial PTO thin film was deposited on a Nb-doped SrTiO3 (Nb:STO) substrate via pulsed laser deposition. A monolayer MoS2 sheet was exfoliated from a bulk crystal and transferred to the surface of the PTO/Nb:STO. Structural and surface properties of the PTO thin film were characterized by X-ray diffraction and atomic force microscopy, respectively. Raman spectroscopy analysis was performed to identify the single-layer MoS2 sheet on the PTO/Nb:STO. We obtained mobility value (327 cm2/V·s) of the MoS2 channel at room temperature. The MoS2-PTO FeRAM FET showed a wide memory window with 17 kΩ of resistance variation which was attributed to high remnant polarization of the epitaxially grown PTO thin film. According to the fatigue resistance test for the FeRAM FET, however, the resistance states gradually varied during the switching cycles of 109. [Figure not available: see fulltext.

  12. Perovskite-Perovskite Homojunctions via Compositional Doping.

    Science.gov (United States)

    Dänekamp, Benedikt; Müller, Christian; Sendner, Michael; Boix, Pablo P; Sessolo, Michele; Lovrincic, Robert; Bolink, Henk J

    2018-05-11

    One of the most important properties of semiconductors is the possibility of controlling their electronic behavior via intentional doping. Despite the unprecedented progress in the understanding of hybrid metal halide perovskites, extrinsic doping of perovskite remains nearly unexplored and perovskite-perovskite homojunctions have not been reported. Here we present a perovskite-perovskite homojunction obtained by vacuum deposition of stoichiometrically tuned methylammonium lead iodide (MAPI) films. Doping is realized by adjusting the relative deposition rates of MAI and PbI 2 , obtaining p-type (MAI excess) and n-type (MAI defect) MAPI. The successful stoichiometry change in the thin films is confirmed by infrared spectroscopy, which allows us to determine the MA content in the films. We analyzed the resulting thin-film junction by cross-sectional scanning Kelvin probe microscopy (SKPM) and found a contact potential difference (CPD) of 250 mV between the two differently doped perovskite layers. Planar diodes built with the perovskite-perovskite homojunction show the feasibility of our approach for implementation in devices.

  13. Reactive molecular beam epitaxial growth and in situ photoemission spectroscopy study of iridate superlattices

    Directory of Open Access Journals (Sweden)

    C. C. Fan

    2017-08-01

    Full Text Available High-quality (001-oriented perovskite [(SrIrO3m/(SrTiO3] superlattices (m=1/2, 1, 2, 3 and ∞ films have been grown on SrTiO3(001 epitaxially using reactive molecular beam epitaxy. Compared to previously reported superlattices synthesized by pulsed laser deposition, our superlattices exhibit superior crystalline, interface and surface structure, which have been confirmed by high-resolution X-ray diffraction, scanning transmission electron microscopy and atomic force microscopy, respectively. The transport measurements confirm a novel insulator-metal transition with the change of dimensionality in these superlattices, and our first systematic in situ photoemission spectroscopy study indicates that the increasing strength of effective correlations induced by reducing dimensionality would be the dominating origin of this transition.

  14. Lanthanum titanium perovskite compound: Thin film deposition and high frequency dielectric characterization

    Energy Technology Data Exchange (ETDEWEB)

    Le Paven, C., E-mail: claire.lepaven@univ-rennes1.fr [Institut d' Electronique et de Télécommunications de Rennes (IETR, UMR-CNRS 6164), Equipe Matériaux Fonctionnels, IUT Saint Brieuc, Université de Rennes 1, 22000 Saint Brieuc (France); Lu, Y. [Institut d' Electronique et de Télécommunications de Rennes (IETR, UMR-CNRS 6164), Equipe Matériaux Fonctionnels, IUT Saint Brieuc, Université de Rennes 1, 22000 Saint Brieuc (France); Nguyen, H.V. [Institut d' Electronique et de Télécommunications de Rennes (IETR, UMR-CNRS 6164), Equipe Matériaux Fonctionnels, IUT Saint Brieuc, Université de Rennes 1, 22000 Saint Brieuc (France); CEA LETI, Minatec Campus, 38054 Grenoble (France); Benzerga, R.; Le Gendre, L. [Institut d' Electronique et de Télécommunications de Rennes (IETR, UMR-CNRS 6164), Equipe Matériaux Fonctionnels, IUT Saint Brieuc, Université de Rennes 1, 22000 Saint Brieuc (France); Rioual, S. [Laboratoire de Magnétisme de Brest (EA CNRS 4522), Université de Bretagne Occidentale, 29000 Brest (France); Benzegoutta, D. [Institut des Nanosciences de Paris (INSP, UMR CNRS 7588), Université Pierre et Marie Curie, 75005 Paris (France); Tessier, F.; Cheviré, F. [Institut des Sciences Chimiques de Rennes (ISCR, UMR-CNRS 6226), Equipe Verres et Céramiques, Université de Rennes 1, 35000 Rennes (France); and others

    2014-02-28

    Perovskite lanthanum titanium oxide thin films were deposited on (001) MgO, (001) LaAlO{sub 3} and Pt(111)/TiO{sub 2}/SiO{sub 2}/(001)Si substrates by RF magnetron sputtering, using a La{sub 2}Ti{sub 2}O{sub 7} homemade target sputtered under oxygen reactive plasma. The films deposited at 800 °C display a crystalline growth different than those reported on monoclinic ferroelectric La{sub 2}Ti{sub 2}O{sub 7} films. X-ray photoelectron spectroscopy analysis shows the presence of titanium as Ti{sup 4+} ions, with no trace of Ti{sup 3+}, and provides a La/Ti ratio of 1.02. The depositions being performed from a La{sub 2}Ti{sub 2}O{sub 7} target under oxygen rich plasma, the same composition (La{sub 2}Ti{sub 2}O{sub 7}) is proposed for the deposited films, with an unusual orthorhombic cell and Cmc2{sub 1} space group. The films have a textured growth on MgO and Pt/Si substrates, and are epitaxially grown on LaAlO{sub 3} substrate. The dielectric characterization displays stable values of the dielectric constant and of the losses in the frequency range [0.1–20] GHz. No variation of the dielectric constant has been observed when a DC electric field up to 250 kV/cm was applied, which does not match a classical ferroelectric behavior at high frequencies and room temperature for the proposed La{sub 2}Ti{sub 2}O{sub 7} orthorhombic phase. At 10 GHz and room temperature, the dielectric constant of the obtained La{sub 2}Ti{sub 2}O{sub 7} films is ε ∼ 60 and the losses are low (tanδ < 0.02). - Highlights: • Lanthanum titanium oxide films were deposited by reactive magnetron sputtering. • A La{sub 2}Ti{sub 2}O{sub 7} chemical composition is proposed, with an unusual orthorhombic cell. • At 10 GHz, the dielectric losses are lower than 0.02. • No variation of the dielectric constant is observed under DC electric biasing.

  15. Curtailing Perovskite Processing Limitations via Lamination at the Perovskite/Perovskite Interface

    Energy Technology Data Exchange (ETDEWEB)

    Van Hest, Marinus F [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Moore, David [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Klein, Talysa [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Christians, Jeffrey A [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Beard, Matthew C [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Berry, Joseph J [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Dunfield, Sean P. [University of Colorado; Fabian, David M. [University of California Irvine; Dixon, Alex G. [University of Colorado; Dou, Benjia [University of Colorado; Ardo, Shane [University of California Irvine; Shaheen, Sean E. [University of Colorado

    2018-04-24

    Standard layer-by-layer solution processing methods constrain lead-halide perovskite device architectures. The layer below the perovskite must be robust to the strong organic solvents used to form the perovskite while the layer above has a limited thermal budget and must be processed in nonpolar solvents to prevent perovskite degradation. To circumvent these limitations, we developed a procedure where two transparent conductive oxide/transport material/perovskite half stacks are independently fabricated and then laminated together at the perovskite/perovskite interface. Using ultraviolet-visible absorption spectroscopy, external quantum efficiency, X-ray diffraction, and time-resolved photoluminesence spectroscopy, we show that this procedure improves photovoltaic properties of the perovskite layer. Applying this procedure, semitransparent devices employing two high-temperature oxide transport layers were fabricated, which realized an average efficiency of 9.6% (maximum: 10.6%) despite series resistance limitations from the substrate design. Overall, the developed lamination procedure curtails processing constraints, enables new device designs, and affords new opportunities for optimization.

  16. Influence of sintering parameters in the ferroelectric properties os strontium bismuth tantalate samples obtained by oxide mixture

    International Nuclear Information System (INIS)

    Souza, R.R. de; Pereira, A.S.; Sousa, V.C.; Egea, J.R.J.

    2012-01-01

    The family of compounds layered-type perovskite, know as Aurivilius presents great alternative not only by the absence of lead in the composition, but because the polarization retention, replacing PZT in FeRAM devices. The strontium bismuth tantalate (SrBi 2 Ta 2 O 9 ) or SBT is ferroelectric material that has attracted considerable interest, since it has high fatigue resistance, supporting high hysteresis loops, with the change in polarization.Checking polarization and depolarization currents stimulated by temperature it is possible to obtain, for example, information about the nature of charges and about the activation energy for the process of dielectric relaxation. For analysis of ferroelectric properties of this compound, it is essential to obtain specimens with a relative density around 95%. Thus, it is important the optimization of the sintering process in order to obtain a ceramic body with a high densification. The influence of sintering parameters to obtain SrBi 2 Ta 2 O 9 in the polarization properties and in the microstructure of sintered samples was investigated by thermostimulated currents and electronic microscopy, respectively. Results show that variation of these parameters may cause changes in the ferroelectric properties of the material. (author)

  17. Layer-by-Layer Epitaxial Growth of Defect-Engineered Strontium Cobaltites

    Energy Technology Data Exchange (ETDEWEB)

    Andersen, Tassie K. [Materials Science; Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, United States; Cook, Seyoung [Materials Science; Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, United States; Wan, Gang [Materials Science; Hong, Hawoong [Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, United States; Marks, Laurence D. [Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, United States; Fong, Dillon D. [Materials Science

    2018-01-31

    Control over structure and composition of (ABO(3)) perovskite oxides offers exciting opportunities since these materials possess unique, tunable properties. Perovskite oxides with cobalt B-site cations are particularly promising, as the range of the cations stable oxidation states leads to many possible structural frameworks. Here, we report growth of strontium cobalt oxide thin films by molecular beam epitaxy, and conditions necessary to stabilize different defect concentration phases. In situ X-ray scattering is used to monitor structural evolution during growth, while in situ X-ray absorption near-edge spectroscopy is used to probe oxidation state and measure changes to oxygen vacancy concentration as a function of film thickness. Experimental results are compared to kinetically limited thermodynamic predictions, in particular, solute trapping, with semiquantitative agreement. Agreement between observations of dependence of cobaltite phase on oxidation activity and deposition rate, and predictions indicates that a combined experimental/theoretical approach is key to understanding phase behavior in the strontium cobalt oxide system.

  18. Enhanced electrical properties in bilayered ferroelectric thin films

    Science.gov (United States)

    Zhang, Hao; Long, WeiJie; Chen, YaQing; Guo, DongJie

    2013-03-01

    Sr2Bi4Ti5O18 (SBTi) single layered and Sr2Bi4Ti5O18/Pb(Zr0.53Ti0.47)O3 (SBTi/PZT) bilayered thin films have been prepared on Pt/TiO2/SiO2/Si substrates by pulsed-laser deposition (PLD). The related structural characterizations and electrical properties have been comparatively investigated. X-ray diffraction reveals that both films have crystallized into perovskite phases and scanning electron microscopy shows the sharp interfaces. Both films show well-saturated ferroelectric hysteresis loops, however, compared with the single layered SBTi films, the SBTi/PZT bilayered films have significantly increased remnant polarization ( P r) and decreased coercive field ( E c), with the applied field of 260 kV/cm. The measured P r and E c of SBTi and SBTi/PZT films were 7.9 μC/cm2, 88.1 kV/cm and 13.0 μC/cm2, 51.2 kV/cm, respectively. In addition, both films showed good fatigue-free characteristics, the switchable polarization decreased by 9% and 11% of the initial values after 2.2×109 switching cycles for the SBTi single layered films and the SBTi/PZT bilayered films, respectively. Our results may provide some guidelines for further optimization of multilayered ferroelectric thin films.

  19. Enhanced piezoelectric properties of (110)-oriented PbZr1−xTixO3 epitaxial thin films on silicon substrates at shifted morphotropic phase boundary

    NARCIS (Netherlands)

    Wan, X.; Houwman, Evert Pieter; Steenwelle, Ruud Johannes Antonius; van Schaijk, R.; Nguyen, Duc Minh; Dekkers, Jan M.; Rijnders, Augustinus J.H.M.

    2014-01-01

    Piezoelectrical, ferroelectrical, and structural properties of epitaxial pseudocubic (110)pc oriented 500 nm thick PbZr1−xTixO3 thin films, prepared by pulsed laser deposition on (001) silicon substrates, were measured as a function of composition. The dependence of the measurement data on the Ti

  20. Temporary formation of highly conducting domain walls for non-destructive read-out of ferroelectric domain-wall resistance switching memories

    Science.gov (United States)

    Jiang, Jun; Bai, Zi Long; Chen, Zhi Hui; He, Long; Zhang, David Wei; Zhang, Qing Hua; Shi, Jin An; Park, Min Hyuk; Scott, James F.; Hwang, Cheol Seong; Jiang, An Quan

    2018-01-01

    Erasable conductive domain walls in insulating ferroelectric thin films can be used for non-destructive electrical read-out of the polarization states in ferroelectric memories. Still, the domain-wall currents extracted by these devices have not yet reached the intensity and stability required to drive read-out circuits operating at high speeds. This study demonstrated non-destructive read-out of digital data stored using specific domain-wall configurations in epitaxial BiFeO3 thin films formed in mesa-geometry structures. Partially switched domains, which enable the formation of conductive walls during the read operation, spontaneously retract when the read voltage is removed, reducing the accumulation of mobile defects at the domain walls and potentially improving the device stability. Three-terminal memory devices produced 14 nA read currents at an operating voltage of 5 V, and operated up to T = 85 °C. The gap length can also be smaller than the film thickness, allowing the realization of ferroelectric memories with device dimensions far below 100 nm.

  1. An epitaxial transparent conducting perovskite oxide: double-doped SrTiO3

    NARCIS (Netherlands)

    Ravichandran, Jayakanth; Siemons, W.; Heijmerikx, Herman; Huijben, Mark; Majumdar, Arun; Ramesh, Ramamoorthy

    2010-01-01

    Epitaxial thin films of strontium titanate doped with different concentrations of lanthanum and oxygen vacancies were grown on LSAT substrates by pulsed laser deposition technique. Films grown with 5−15% La doping and a critical growth pressure of 1−10 mTorr showed high transparency (>70−95%) in the

  2. Anisotropic-strain-relaxation-induced crosshatch morphology in epitaxial SrTiO{sub 3}/NdGaO{sub 3} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Tan, X. L.; Chen, F.; Chen, P. F.; Xu, H. R.; Chen, B. B.; Jin, F.; Gao, G. Y.; Wu, W. B., E-mail: wuwb@ustc.edu.cn [Hefei National Laboratory for Physical Sciences at Microscale, University of Science and Technology of China, and High Magnetic Field Laboratory, Chinese Academy of Sciences, Hefei 230026 (China)

    2014-10-15

    We investigate the strain relaxation and surface morphology of epitaxial SrTiO{sub 3} (STO) films grown on (001){sub O} and (110){sub O} planes of orthorhombic NdGaO{sub 3} (NGO), and (001) plane of cubic (LaAlO{sub 3}){sub 0.3}(Sr{sub 2}AlTaO{sub 6}){sub 0.7} (LSAT) substrates. Although the average lattice mismatches are similar, strikingly regular crosshatched surface patterns can be found on STO/NGO(001){sub O}[(110){sub O}] films, contrary to the uniform surface of STO/LSAT(001). Based on the orientation and thickness dependent patterns and high-resolution x-ray diffractions, we ascribe the crosshatch morphology to the anisotropic strain relaxation with possibly the 60° misfit dislocation formation and lateral surface step flow in STO/NGO films, while an isotropic strain relaxation in STO/LSAT. Further, we show that the crosshatched STO/NGO(110){sub O} surface could be utilized as a template to modify the magnetotransport properties of epitaxial La{sub 0.6}Ca{sub 0.4}MnO{sub 3} films. This study highlights the crucial role of symmetry mismatch in determining the surface morphology of the perovskite oxide films, in addition to their epitaxial strain states, and offers a different route for designing and fabricating functional perovskite-oxide devices.

  3. Effect of the out-of-plane stress on the properties of epitaxial SrTiO3 films with nano-pillar array on Si-substrate

    Science.gov (United States)

    Bai, Gang; Xie, Qiyun; Liu, Zhiguo; Wu, Dongmei

    2015-08-01

    A nonlinear thermodynamic formalism has been proposed to calculate the physical properties of the epitaxial SrTiO3 films containing vertical nano-pillar array on Si-substrate. The out-of-plane stress induced by the mismatch between film and nano-pillars provides an effective way to tune the physical properties of ferroelectric SrTiO3 films. Tensile out-of-plane stress raises the phase transition temperature and increases the out-of-plane polarization, but decreases the out-of-plane dielectric constant below Curie temperature, pyroelectric coefficient, and piezoelectric coefficient. These results showed that by properly controlling the out-of-plane stress, the out-of-plane stress induced paraelectric-ferroelectric phase transformation will appear near room temperature. Excellent dielectric, pyroelectric, piezoelectric properties of these SrTiO3 films similar to PZT and other lead-based ferroelectrics can be expected.

  4. Defect formation and carrier doping in epitaxial films of the ''parent'' compound SrCuO2: Synthesis of two superconductors descendants

    International Nuclear Information System (INIS)

    Feenstra, R.; Norton, D.P.; Budai, J.D.; Jones, E.C.; Christen, D.K.; Kawai, T.

    1995-04-01

    The infinite layer or parent compounds ACuO 2 (A: Ca-Sr-Ba) constitute the simplest copper oxygen perovskites that contain the CuO 2 sheets essential for superconductivity. The stabilization of these basic ''building blocks'' as epitaxial films, therefore, provides alluring opportunities towards the search for new superconducting compounds and elucidation of the underlying mechanisms. In this work, general trends of the defect formation and carrier doping for epitaxial films of the intermediate endmember SrCuO 2 are reviewed. First results are presented from successful attempts to induce hole-doped superconductivity via the processing-controlled incorporation of charge reservoir layers

  5. Hybrid Perovskite/Perovskite Heterojunction Solar Cells.

    Science.gov (United States)

    Hu, Yinghong; Schlipf, Johannes; Wussler, Michael; Petrus, Michiel L; Jaegermann, Wolfram; Bein, Thomas; Müller-Buschbaum, Peter; Docampo, Pablo

    2016-06-28

    Recently developed organic-inorganic hybrid perovskite solar cells combine low-cost fabrication and high power conversion efficiency. Advances in perovskite film optimization have led to an outstanding power conversion efficiency of more than 20%. Looking forward, shifting the focus toward new device architectures holds great potential to induce the next leap in device performance. Here, we demonstrate a perovskite/perovskite heterojunction solar cell. We developed a facile solution-based cation infiltration process to deposit layered perovskite (LPK) structures onto methylammonium lead iodide (MAPI) films. Grazing-incidence wide-angle X-ray scattering experiments were performed to gain insights into the crystallite orientation and the formation process of the perovskite bilayer. Our results show that the self-assembly of the LPK layer on top of an intact MAPI layer is accompanied by a reorganization of the perovskite interface. This leads to an enhancement of the open-circuit voltage and power conversion efficiency due to reduced recombination losses, as well as improved moisture stability in the resulting photovoltaic devices.

  6. Misfit strain-film thickness phase diagrams and related electromechanical properties of epitaxial ultra-thin lead zirconate titanate films

    Energy Technology Data Exchange (ETDEWEB)

    Qiu, Q.Y.; Mahjoub, R. [School of Materials Science and Engineering, University of New South Wales, Sydney, NSW 2052 (Australia); Alpay, S.P. [Materials Science and Engineering Program and Institute of Materials Science, University of Connecticut, Storrs, CT 06269 (United States); Nagarajan, V., E-mail: nagarajan@unsw.edu.au [School of Materials Science and Engineering, University of New South Wales, Sydney, NSW 2052 (Australia)

    2010-02-15

    The phase stability of ultra-thin (0 0 1) oriented ferroelectric PbZr{sub 1-x}Ti{sub x}O{sub 3} (PZT) epitaxial thin films as a function of the film composition, film thickness, and the misfit strain is analyzed using a non-linear Landau-Ginzburg-Devonshire thermodynamic model taking into account the electrical and mechanical boundary conditions. The theoretical formalism incorporates the role of the depolarization field as well as the possibility of the relaxation of in-plane strains via the formation of microstructural features such as misfit dislocations at the growth temperature and ferroelastic polydomain patterns below the paraelectric-ferroelectric phase transformation temperature. Film thickness-misfit strain phase diagrams are developed for PZT films with four different compositions (x = 1, 0.9, 0.8 and 0.7) as a function of the film thickness. The results show that the so-called rotational r-phase appears in a very narrow range of misfit strain and thickness of the film. Furthermore, the in-plane and out-of-plane dielectric permittivities {epsilon}{sub 11} and {epsilon}{sub 33}, as well as the out-of-plane piezoelectric coefficients d{sub 33} for the PZT thin films, are computed as a function of misfit strain, taking into account substrate-induced clamping. The model reveals that previously predicted ultrahigh piezoelectric coefficients due to misfit-strain-induced phase transitions are practically achievable only in an extremely narrow range of film thickness, composition and misfit strain parameter space. We also show that the dielectric and piezoelectric properties of epitaxial ferroelectric films can be tailored through strain engineering and microstructural optimization.

  7. Catalytic Activity Enhancement for Oxygen Reduction on Epitaxial Perovskite Thin Films for Solid-Oxide Fuel Cells

    KAUST Repository

    la O', Gerardo Jose; Ahn, Sung-Jin; Crumlin, Ethan; Orikasa, Yuki; Biegalski, Michael D.; Christen, Hans M.; Shao-Horn, Yang

    2010-01-01

    Figure Presented The active ingredient: La0.8Sr 0.2CoO3-δ (LSC) epitaxial thin films are prepared on (001 )-oriented yttria-stabilized zirconia (YSZ) single crystals with a gadolinium-doped ceria (GDC) buffer layer (see picture). The LSC epitaxial films exhibit better oxygen reduction kinetics than bulk LSC. The enhanced activity is attributed in part to higher oxygen nonstoichiometry. © 2010 Wiley-VCH Verlag GmbH & Co. KCaA, Weinheim.

  8. Catalytic Activity Enhancement for Oxygen Reduction on Epitaxial Perovskite Thin Films for Solid-Oxide Fuel Cells

    KAUST Repository

    la O', Gerardo Jose

    2010-06-22

    Figure Presented The active ingredient: La0.8Sr 0.2CoO3-δ (LSC) epitaxial thin films are prepared on (001 )-oriented yttria-stabilized zirconia (YSZ) single crystals with a gadolinium-doped ceria (GDC) buffer layer (see picture). The LSC epitaxial films exhibit better oxygen reduction kinetics than bulk LSC. The enhanced activity is attributed in part to higher oxygen nonstoichiometry. © 2010 Wiley-VCH Verlag GmbH & Co. KCaA, Weinheim.

  9. Origin of the "Waterfall" Effect in Phonon Dispersion of Relaxor Perovskites

    OpenAIRE

    Hlinka, J.; Kamba, S.; Petzelt, J.; Kulda, J.; Randall, C. A.; Zhang, S. J.

    2003-01-01

    We have undertaken an inelastic neutron scattering study of the perovskite relaxor ferroelectric \\ud P\\ud b\\ud (\\ud Z\\ud n\\ud 1\\ud /\\ud 3\\ud N\\ud b\\ud 2\\ud /\\ud 3\\ud )\\ud O\\ud 3\\ud with 8% \\ud P\\ud b\\ud T\\ud i\\ud O\\ud 3\\ud (PZN-8%PT) in order to elucidate the origin of the previously reported unusual kink on the low frequency transverse phonon dispersion curve (known as the “waterfall effect”). We show that its position (\\ud q\\ud w\\ud f\\ud ) depends on the choice of the Brillouin zone and tha...

  10. Enhanced Exciton and Photon Confinement in Ruddlesden-Popper Perovskite Microplatelets for Highly Stable Low-Threshold Polarized Lasing.

    Science.gov (United States)

    Li, Mingjie; Wei, Qi; Muduli, Subas Kumar; Yantara, Natalia; Xu, Qiang; Mathews, Nripan; Mhaisalkar, Subodh G; Xing, Guichuan; Sum, Tze Chien

    2018-06-01

    At the heart of electrically driven semiconductors lasers lies their gain medium that typically comprises epitaxially grown double heterostuctures or multiple quantum wells. The simultaneous spatial confinement of charge carriers and photons afforded by the smaller bandgaps and higher refractive index of the active layers as compared to the cladding layers in these structures is essential for the optical-gain enhancement favorable for device operation. Emulating these inorganic gain media, superb properties of highly stable low-threshold (as low as ≈8 µJ cm -2 ) linearly polarized lasing from solution-processed Ruddlesden-Popper (RP) perovskite microplatelets are realized. Detailed investigations using microarea transient spectroscopies together with finite-difference time-domain simulations validate that the mixed lower-dimensional RP perovskites (functioning as cladding layers) within the microplatelets provide both enhanced exciton and photon confinement for the higher-dimensional RP perovskites (functioning as the active gain media). Furthermore, structure-lasing-threshold relationship (i.e., correlating the content of lower-dimensional RP perovskites in a single microplatelet) vital for design and performance optimization is established. Dual-wavelength lasing from these quasi-2D RP perovskite microplatelets can also be achieved. These unique properties distinguish RP perovskite microplatelets as a new family of self-assembled multilayer planar waveguide gain media favorable for developing efficient lasers. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Ferroelectric, magnetic and structural studies of the Bi4LaSmFe2Ti3O18 multiferroic material

    International Nuclear Information System (INIS)

    Alarcón-Suesca, C.E.; Cardona-Vásquez, J.A.; Salcedo-Fontecha, J.P.; Vargas-Jiménez, A.; Landínez-Téllez, D.A.; Roa-Rojas, J.

    2014-01-01

    We report the synthesis and characterization of the new Bi 4 LaSmFe 2 Ti 3 O 18 ferroelectric ceramic. X-ray characterization reveals reflections for layered perovskite Aurivillius system. Rietveld analyses of the powder pattern shows that Bi 4 LaSmFe 2 Ti 3 O 18 crystallizes in orthorhombic structure, which corresponds to the space group F2/mm (#42), with lattice parameters a=5.4240(16) Ǻ, b=5.4078(23) Ǻ and c=50.2440(12) Ǻ. Scanning electron microscopy (SEM) reveals the formation of dense material with plate-like morphology. Electric polarization curves were measured by means of a radiant ferroelectric tester, at room temperature in bulk samples and exhibit an intrinsic ferroelectric response, even at low applied fields. Measurements of the magnetization as a function of temperature after Zero field cooling and field cooling were carried out by using a MPMS Quantum Design SQUID magnetometer. We found an effective magnetic moment of 7.95 µB, which is 95.8% in agreement with the expected value calculated from Hund's rules. Magnetization curves as the function of applied fields reveal an incipient hysteretic behavior at room temperature

  12. Highly piezoelectric BaTiO3 nanorod bundle arrays using epitaxially grown TiO2 nanomaterials.

    Science.gov (United States)

    Jang, Seon-Min; Yang, Su Chul

    2018-06-08

    Low-dimensional piezoelectric nanostructures such as nanoparticles, nanotubes, nanowires, nanoribbons and nanosheets have been developed for potential applications as energy harvesters, tunable sensors, functional transducers and low-power actuators. In this study, lead-free BaTiO 3 nanorod bundle arrays (NBA) with highly piezoelectric properties were successfully synthesized on fluorine-doped tin oxide (FTO) substrate via a two-step process consisting of TiO 2 epitaxial growth and BaTiO 3 conversion. Through the TiO 2 epitaxial growth on FTO substrate, (001) oriented TiO 2 nanostructures formed vertically-aligned NBA with a bundle diameter of 80 nm and an aspect ratio of six. In particular, chemical etching of the TiO 2 NBA was conducted to enlarge the surface area for effective Ba 2+ ion diffusion during the perovskite conversion process from TiO 2 to BaTiO 3 . The final structure of perovskite BaTiO 3 NBA was found to exhibit a feasible piezoelectric response of 3.56 nm with a clear phase change of 180° from the single BaTiO 3 bundle, by point piezoelectric forced microscopy (PFM) analysis. Consequently, highly piezoelectric NBA could be a promising nanostructure for various nanoscale electronic devices.

  13. Highly piezoelectric BaTiO3 nanorod bundle arrays using epitaxially grown TiO2 nanomaterials

    Science.gov (United States)

    Jang, Seon-Min; Yang, Su Chul

    2018-06-01

    Low-dimensional piezoelectric nanostructures such as nanoparticles, nanotubes, nanowires, nanoribbons and nanosheets have been developed for potential applications as energy harvesters, tunable sensors, functional transducers and low-power actuators. In this study, lead-free BaTiO 3 nanorod bundle arrays (NBA) with highly piezoelectric properties were successfully synthesized on fluorine-doped tin oxide (FTO) substrate via a two-step process consisting of TiO2 epitaxial growth and BaTiO3 conversion. Through the TiO2 epitaxial growth on FTO substrate, (001) oriented TiO2 nanostructures formed vertically-aligned NBA with a bundle diameter of 80 nm and an aspect ratio of six. In particular, chemical etching of the TiO2 NBA was conducted to enlarge the surface area for effective Ba2+ ion diffusion during the perovskite conversion process from TiO2 to BaTiO3. The final structure of perovskite BaTiO3 NBA was found to exhibit a feasible piezoelectric response of 3.56 nm with a clear phase change of 180° from the single BaTiO3 bundle, by point piezoelectric forced microscopy (PFM) analysis. Consequently, highly piezoelectric NBA could be a promising nanostructure for various nanoscale electronic devices.

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

    Science.gov (United States)

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

    2018-02-01

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

  15. Origin of long lifetime of band-edge charge carriers in organic-inorganic lead iodide perovskites.

    Science.gov (United States)

    Chen, Tianran; Chen, Wei-Liang; Foley, Benjamin J; Lee, Jooseop; Ruff, Jacob P C; Ko, J Y Peter; Brown, Craig M; Harriger, Leland W; Zhang, Depei; Park, Changwon; Yoon, Mina; Chang, Yu-Ming; Choi, Joshua J; Lee, Seung-Hun

    2017-07-18

    Long carrier lifetime is what makes hybrid organic-inorganic perovskites high-performance photovoltaic materials. Several microscopic mechanisms behind the unusually long carrier lifetime have been proposed, such as formation of large polarons, Rashba effect, ferroelectric domains, and photon recycling. Here, we show that the screening of band-edge charge carriers by rotation of organic cation molecules can be a major contribution to the prolonged carrier lifetime. Our results reveal that the band-edge carrier lifetime increases when the system enters from a phase with lower rotational entropy to another phase with higher entropy. These results imply that the recombination of the photoexcited electrons and holes is suppressed by the screening, leading to the formation of polarons and thereby extending the lifetime. Thus, searching for organic-inorganic perovskites with high rotational entropy over a wide range of temperature may be a key to achieve superior solar cell performance.

  16. Direct large-scale synthesis of perovskite barium strontium titanate nano-particles from solutions

    International Nuclear Information System (INIS)

    Qi Jianquan; Wang Yu; Wan Pingchen; Long Tuli; Chan, Helen Lai Wah

    2005-01-01

    This paper reports a wet chemical synthesis technique for large-scale fabrication of perovskite barium strontium titanate nano-particles near room temperature and under ambient pressure. The process employs titanium alkoxide and alkali earth hydroxides as starting materials and involves very simple operation steps. Particle size and crystallinity of the particles are controllable by changing the processing parameters. Observations by X-ray diffraction, scanning electron microscopy and transmission electron microscopy TEM indicate that the particles are well-crystallized, chemically stoichiometric and ∼50nm in diameter. The nanoparticles can be sintered into ceramics at 1150 deg. C and show typical ferroelectric hysteresis loops

  17. Absence of a polar phase in perovskite chromite RCrO{sub 3} (R=La and Pr)

    Energy Technology Data Exchange (ETDEWEB)

    Yoshii, Kenji, E-mail: yoshiike@spring8.or.jp [Japan Atomic Energy Agency (JAEA), Sayo, Hyogo 679-5148 (Japan); Ikeda, Naoshi [Okayama University, Okayama 700-8530 (Japan); Shimojo, Yutaka; Ishii, Yoshinobu [Japan Atomic Energy Agency (JAEA), Tokai, Ibaraki 319-1195 (Japan)

    2017-04-01

    Magnetic and dielectric properties have been studied for LaCrO{sub 3}, PrCrO{sub 3}, and their solid solution La{sub 0.5}Pr{sub 0.5}CrO{sub 3}, which belong to a family of the ferroelectric orthochromite series RCrO{sub 3} (R: rare earths). The magnetic measurements confirm that the materials show canted antiferromagnetic ordering at 240–288 K. Neutron diffraction patterns could be fitted with the centrosymmetric Pnma, which is different from the non-centrosymmetric structure proposed for the ferroelectric phase of NdCrO{sub 3}. The large dielectric constants are likely due to the hopping of charge carriers as proposed previously for other chromites. - Highlights: • Magnetic and dielectric properties of the three perovskite chromites. • Neutron diffraction patterns fitted with centrosymmetric Pnma. • Large dielectric constants likely due to the hopping of charge carriers.

  18. Molecular ferroelectrics: where electronics meet biology.

    Science.gov (United States)

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

    2013-12-28

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

  19. Epitaxial growth and structural characterization of Pb(Fe1/2Nb1/2)O3 thin films

    International Nuclear Information System (INIS)

    Peng, W.; Lemee, N.; Holc, J.; Kosec, M.; Blinc, R.; Karkut, M.G.

    2009-01-01

    We have grown lead iron niobate thin films with composition Pb(Fe 1/2 Nb 1/2 )O 3 (PFN) on (0 0 1) SrTiO 3 substrates by pulsed laser deposition. The influence of the deposition conditions on the phase purity was studied. Due to similar thermodynamic stability spaces, a pyrochlore phase often coexists with the PFN perovskite phase. By optimizing the kinetic parameters, we succeeded in identifying a deposition window which resulted in epitaxial perovskite-phase PFN thin films with no identifiable trace of impurity phases appearing in the X-ray diffractograms. PFN films having thicknesses between 20 and 200 nm were smooth and epitaxially oriented with the substrate and as demonstrated by RHEED streaks which were aligned with the substrate axes. X-ray diffraction showed that the films were completely c-axis oriented and of excellent crystalline quality with low mosaicity (X-ray rocking curve FWHM≤0.09 deg.). The surface roughness of thin films was also investigated by atomic force microscopy. The root-mean-square roughness varies between 0.9 nm for 50-nm-thick films to 16 nm for 100-nm-thick films. We also observe a correlation between grain size, surface roughness and film thickness.

  20. Evaluation of covalency of ions in lead-free perovskite-type dielectric oxides

    Directory of Open Access Journals (Sweden)

    Naohisa Takesue

    2017-10-01

    Full Text Available Electronic states of ions in lead-free perovskite-type dielectric oxides have been investigated with a first-principle cluster calculation. For this calculation a double-perovskite cluster model based upon the simple cubic ABO3 was used; A and B are both the cations, and O is the oxygen anion. Systematic variations of ionic species for A and B, and lengths of the model cube edge were given to the model. Results of charge transfers of the ions show that their magnitudes depend on the edge length; the lager length leads to the higher transfer magnitude. This tendency implies spatial tolerance of the ions to the clusters, and are expected to correlate with electric polarizability and dipole reversibility of this kind of oxides. The density of states and the overlap population indicate that the higher cation valence causes the higher covalency of the anions. Considering all results together provides us an idea to obtain lead-free high-performance ferroelectrics, as high as the lead-based solid solutions.

  1. The crystal structure and twinning of neodymium gallium perovskite single crystals

    International Nuclear Information System (INIS)

    Ubizskii, S.B.; Vasylechko, L.O.; Savytskii, D.I.; Matkovskii, A.O.; Syvorotka, I.M.

    1994-01-01

    By means of X-ray structure analysis, the crystal structure of neodymium gallium perovskite (NGP) single crystals (NdGaO 3 ) being used as a substrate for HTSC film epitaxy has been refined and the position of atoms has been determined. The possibility of YBa 2 Cu 3 O 7-x film epitaxy on the plane (110) of NGP crystal as well as its advantages and pitfalls are analysed from structural data. The twinning types in the NGP crystal were established. The twinning structure of NGP substrates is found to be stable up to a temperature of 1173 K, as differentiated from the LaGaO 3 and LaAlO 3 substrates. It is intimated that the twinning in the NGP substrates oriented as (001) can result in creation of 90 degrees twin bonds in a film, and in the case of (110)-oriented plates it is possible to ignore the twinning presence in substrate completely. (author)

  2. Effect of the out-of-plane stress on the properties of epitaxial SrTiO{sub 3} films with nano-pillar array on Si-substrate

    Energy Technology Data Exchange (ETDEWEB)

    Bai, Gang, E-mail: baigang@njupt.edu.cn [Jiangsu Provincial Engineering Laboratory for RF Integration and Micropackaging and College of Electronic Science and Engineering, Nanjing University of Posts and Telecommunications, Nanjing 210023 (China); Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093 (China); Xie, Qiyun [Jiangsu Provincial Engineering Laboratory for RF Integration and Micropackaging and College of Electronic Science and Engineering, Nanjing University of Posts and Telecommunications, Nanjing 210023 (China); Liu, Zhiguo [Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093 (China); Wu, Dongmei [School of Automation, Nanjing University of Posts and Telecommunications, Nanjing 210023 (China)

    2015-08-21

    A nonlinear thermodynamic formalism has been proposed to calculate the physical properties of the epitaxial SrTiO{sub 3} films containing vertical nano-pillar array on Si-substrate. The out-of-plane stress induced by the mismatch between film and nano-pillars provides an effective way to tune the physical properties of ferroelectric SrTiO{sub 3} films. Tensile out-of-plane stress raises the phase transition temperature and increases the out-of-plane polarization, but decreases the out-of-plane dielectric constant below Curie temperature, pyroelectric coefficient, and piezoelectric coefficient. These results showed that by properly controlling the out-of-plane stress, the out-of-plane stress induced paraelectric-ferroelectric phase transformation will appear near room temperature. Excellent dielectric, pyroelectric, piezoelectric properties of these SrTiO{sub 3} films similar to PZT and other lead-based ferroelectrics can be expected.

  3. Remarkable Strontium B-Site Occupancy in FerroelectricPb(Zr1-xTix)O3 Solid Solutions Doped with Cryolite-Type StrontiumNiobate

    Energy Technology Data Exchange (ETDEWEB)

    Feltz, A.; Schmidt-Winkel, P.; Schossman, M.; Booth, C.H.; Albering, J.

    2007-04-26

    New high-performance ferroelectric materials based on Pb(Zr{sub 1-x}Ti{sub x})O{sub 3} (PZT) that are doped with cryolite-type strontium niobate (SNO, Sr{sub 4}(Sr{sub 2-2y/3}Nb{sub 2+2y/3})O{sub 11+y}V{sub 0,1-y} with 0 {le} y {le} 1), hence denoted PZT:SNO, and their microscopic structure are described. The combination of exceptional piezoelectric properties, i.e. a piezoelectric strain constant of d{sub 33} {approx} 760 pm/V, with excellent stability and degradation resistance makes ferroelectric PZT:SNO solid solutions very attractive for use in novel and innovative piezoelectric actuator and transducer applications. Extended X-ray absorption fine-structure (EXAFS) analyses of PZT:SNO samples revealed that {approx}10 % of the Sr cations occupy the nominal B-sites of the perovskite-type PZT host lattice. This result was supported by EXAFS analyses of both a canonical SrTiO{sub 3} perovskite and two SNO model and reference compounds. Fit models that do not account for Sr cations on B-sites were ruled out. A clear Sr-Pb peak in Fourier transformed EXAFS data visually confirmed this structural model. The generation of temporary oxygen vacancies and the intricate defect chemistry induced by SNO-doping of PZT are crucial for the exceptional materials properties exhibited by PZT:SNO materials.

  4. Two-photon spectroscopy study of edge absorption peculiarities in oxygen-octahedric ferroelectrics

    International Nuclear Information System (INIS)

    Shablaev, S.I.; Danishevskij, A.M.; Subashiev, V.K.

    1984-01-01

    Two-photon absorption (TPA) spectra of ferroelectric crystals with BaTiO 3 , KTaO 3 and SrTiO 3 perovskite strUcture Were obtained. The detailed investigation of temperature dependence of edge spectrum regions was conducted and on the basis of their analysis the indirect character of edge absorption was concluded for all mentioned crystals. TPA spectra of BaTiO 3 and KTaO 3 are characterized by the regions corresponding to one indirect edge TPA spectra of SrTiO 3 - to two indirect edges. The corresponding inter-zone gaps were determined for all investigated crystals, the energy of phonons, participating in indirect two photon transitions, inter-zone gaps, corresponding to direct transitions were determined as well

  5. Ferroelectrics principles, structure and applications

    CERN Document Server

    Merchant, Serena

    2014-01-01

    Ferroelectric physics is a theory on ferroelectric phase transition for explaining various related phenomena, which is different from dielectric physics. Ferroelectric materials are important functional materials for various applications such as NVRAMs, high energy density capacitors, actuators, MEMs, sonar sensors, microphones and scanning electron microscopes (SEM). This book investigates the dielectric, ferroelectric and energy storage properties of barium zirconate-titanate/barium calcium-titanate (BZT-BCT) based ceramic for high energy density capacitors. It also compares the energy storage capabilities of ceramic powders with polymer-ceramic nanocomposites; and discusses dielectric properties of ferroelectricity in composition distributions.

  6. Resistance switching in epitaxial SrCoOx thin films

    Science.gov (United States)

    Tambunan, Octolia T.; Parwanta, Kadek J.; Acharya, Susant K.; Lee, Bo Wha; Jung, Chang Uk; Kim, Yeon Soo; Park, Bae Ho; Jeong, Huiseong; Park, Ji-Yong; Cho, Myung Rae; Park, Yun Daniel; Choi, Woo Seok; Kim, Dong-Wook; Jin, Hyunwoo; Lee, Suyoun; Song, Seul Ji; Kang, Sung-Jin; Kim, Miyoung; Hwang, Cheol Seong

    2014-08-01

    We observed bipolar switching behavior from an epitaxial strontium cobaltite film grown on a SrTiO3 (001) substrate. The crystal structure of strontium cobaltite has been known to undergo topotactic phase transformation between two distinct phases: insulating brownmillerite (SrCoO2.5) and conducting perovskite (SrCoO3-δ) depending on the oxygen content. The current-voltage characteristics of the strontium cobaltite film showed that it could have a reversible insulator-to-metal transition triggered by electrical bias voltage. We propose that the resistance switching in the SrCoOx thin film could be related to the topotactic phase transformation and the peculiar structure of SrCoO2.5.

  7. Resistance switching in epitaxial SrCoOx thin films

    International Nuclear Information System (INIS)

    Tambunan, Octolia T.; Parwanta, Kadek J.; Acharya, Susant K.; Lee, Bo Wha; Jung, Chang Uk; Kim, Yeon Soo; Park, Bae Ho; Jeong, Huiseong; Park, Ji-Yong; Cho, Myung Rae; Park, Yun Daniel; Choi, Woo Seok; Kim, Dong-Wook; Jin, Hyunwoo; Lee, Suyoun; Song, Seul Ji; Kang, Sung-Jin; Kim, Miyoung; Hwang, Cheol Seong

    2014-01-01

    We observed bipolar switching behavior from an epitaxial strontium cobaltite film grown on a SrTiO 3 (001) substrate. The crystal structure of strontium cobaltite has been known to undergo topotactic phase transformation between two distinct phases: insulating brownmillerite (SrCoO 2.5 ) and conducting perovskite (SrCoO 3−δ ) depending on the oxygen content. The current–voltage characteristics of the strontium cobaltite film showed that it could have a reversible insulator-to-metal transition triggered by electrical bias voltage. We propose that the resistance switching in the SrCoO x thin film could be related to the topotactic phase transformation and the peculiar structure of SrCoO 2.5

  8. Low temperature dielectric relaxation and charged defects in ferroelectric thin films

    Directory of Open Access Journals (Sweden)

    A. Artemenko

    2013-04-01

    Full Text Available We report a dielectric relaxation in BaTiO3-based ferroelectric thin films of different composition and with several growth modes: sputtering (with and without magnetron and sol-gel. The relaxation was observed at cryogenic temperatures (T < 100 K for frequencies from 100 Hz up to 10 MHz. This relaxation activation energy is always lower than 200 meV and is very similar to the relaxation that we reported in the parent bulk perovskites. Based on our Electron Paramagnetic Resonance (EPR investigation, we ascribe this dielectric relaxation to the hopping of electrons among Ti3+-V(O charged defects. Being dependent on the growth process and on the amount of oxygen vacancies, this relaxation can be a useful probe of defects in actual integrated capacitors with no need for specific shaping.

  9. Electronic and Structural Properties of ABO3: Role of the B-O Coulomb Repulsions for Ferroelectricity.

    Science.gov (United States)

    Miura, Kaoru; Azuma, Masaki; Funakubo, Hiroshi

    2011-01-17

    We have investigated the role of the Ti-O Coulomb repulsions in the appearance of the ferroelectric state in BaTiO3 as well as the role of the Zn-O Coulomb repulsions in BiZn0.5Ti0.5O3, using a first-principles calculation with optimized structures. In tetragonal BaTiO3, it is found that the Coulomb repulsions between Ti 3s and 3p states and O 2s and 2p states have an important role for the appearance of Ti ion displacement. In BiZn0.5Ti0.5O3, on the other hand, the stronger Zn-O Coulomb repulsions, which are due to the 3s, 3p, and 3d (d10) states of the Zn ion, have more important role than the Ti-O Coulomb repulsions for the appearance of the tetragonal structure. Our suggestion is consistent with the other ferroelectric perovskite oxides ABO3 in the appearance of tetragonal structures as well as rhombohedral structures.

  10. Origin of the "waterfall" effect in phonon dispersion of relaxor perovskites.

    Science.gov (United States)

    Hlinka, J; Kamba, S; Petzelt, J; Kulda, J; Randall, C A; Zhang, S J

    2003-09-05

    We have undertaken an inelastic neutron scattering study of the perovskite relaxor ferroelectric Pb(Zn(1/3)Nb(2/3))O3 with 8% PbTiO3 (PZN-8%PT) in order to elucidate the origin of the previously reported unusual kink on the low frequency transverse phonon dispersion curve (known as the "waterfall effect"). We show that its position (q(wf)) depends on the choice of the Brillouin zone and that the relation of q(wf) to the size of the polar nanoregions is highly improbable. The waterfall phenomenon is explained in the framework of a simple model of coupled damped harmonic oscillators representing the acoustic and optic phonon branches.

  11. Reversible pyroelectric and photogalvanic current in epitaxial Pb(Zr0.52Ti0.48)O3 thin films

    Science.gov (United States)

    Lee, J.; Esayan, S.; Prohaska, J.; Safari, A.

    1994-01-01

    The pyroelectric and photogalvanic effects have been studied in epitaxial Pb(Zr0.52Ti0.48)O3 (PZT) thin films. Photoinduced currents, which were completely reversible by electrical voltage, were observed. The photoinduced currents exhibited transient and steady state components. The transient component, in turn, consisted of two components with fast (<1 s) and slow (˜hours) relaxation times. The mechanisms of the photoinduced currents in PZT films and their possible applications in nondestructive readout ferroelectric memory are discussed.

  12. Low-temperature structure and the ferroelectric phase transitions in the CdTi O3 perovskite

    Science.gov (United States)

    Kennedy, Brendan J.; Zhou, Qingdi; Zhao, Shipeng; Jia, Fanhao; Ren, Wei; Knight, Kevin S.

    2017-12-01

    The paraelectric-ferroelectric transition in CdTi O3 has been monitored using high-resolution neutron diffraction data. This necessitated preparing a sample enriched in 114Cd. A subtle, but significant, anisotropy in the thermal expansion of the lattice parameters for CdTi O3 associated with the transition to the polar structure was observed. First-principles calculations are presented to understand energies, phonon dispersion, and structures of possible phases with different symmetries.

  13. Synthesis of Freestanding Single-crystal Perovskite Films and Heterostructures by Etching of Sacrificial Water-soluble Layers

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Di; Baek, David J.; Hong, Seung Sae; Kourkoutis, Lena F.; Hikita, Yasuyuki; Hwang, Harold Y.

    2016-08-22

    The ability to create and manipulate materials in two-dimensional (2D) form has repeatedly had transformative impact on science and technology. In parallel with the exfoliation and stacking of intrinsically layered crystals, atomic-scale thin film growth of complex materials has enabled the creation of artificial 2D heterostructures with novel functionality and emergent phenomena, as seen in perovskite heterostructures. However, separation of these layers from the growth substrate has proven challenging, limiting the manipulation capabilities of these heterostructures with respect to exfoliated materials. Here we present a general method to create freestanding perovskite membranes. The key is the epitaxial growth of water-soluble Sr3Al2O6 on perovskite substrates, followed by in situ growth of films and heterostructures. Millimetre-size single-crystalline membranes are produced by etching the Sr3Al2O6 layer in water, providing the opportunity to transfer them to arbitrary substrates and integrate them with heterostructures of semiconductors and layered compounds.

  14. Cation vacancies in ferroelectric PbTiO3 and Pb(Zr,Ti)O3 : A positron annihilation lifetime spectroscopy study

    Science.gov (United States)

    Keeble, D. J.; Singh, S.; Mackie, R. A.; Morozov, M.; McGuire, S.; Damjanovic, D.

    2007-10-01

    Positron annihilation lifetime spectroscopy measurements identify A - and B -site cation vacancies in ferroelectric perovskite oxides (ABO3) . Crystal PbTiO3 and ceramic lead zirconium titanate (PZT) were studied and gave consistent values for the lifetime resulting from positron localization at lead vacancies VPb . Positron trapping to B -site vacancies was inferred in PZT. Temperature dependent studies showed that the defect specific trapping rate was higher for VB compared to VPb , consistent with the larger negative charge. Doping PZT with Fe increased the fraction positron trapping to VB compared to VPb -type defects.

  15. Ferroelectric properties of BaTiO3/PbZr0.2Ti.08O3 bilayer thin film

    Science.gov (United States)

    Salev, Pavel; Yang, Chun; Grigoriev, Alexei

    2014-03-01

    The thin film ferroelectric BaTiO3/PbZr0.2Ti0.8O3 bilayer was epitaxially grown on SrRuO3/SrTiO3 substrate by RF sputtering. Electrical measurements of polarization switching revealed two different switching regimes - a small ferroelectric hysteresis loop at low applied voltage and a larger loop at a high voltage. The measured dielectric permittivity corresponds to weak electrostatic coupling between two layers according to Landau-Ginsburg-Devonshire theory. This weak coupling may allow for independent polarization states to exist in individual layers. This can lead to stable head-to-head and tail-to-tail polarization domain configurations, which would explain the two switching regimes observed in electrical measurements. The compensation of polarization gradient across the interface can be explained by the enhancement of interface charge carrier density due to strong bending of electron energy bands. This work was supported by NSF award DMR-1057159.

  16. Piezoelectric properties of twinned ferroelectric perovskites with head-to-head and tail-to-tail domain walls

    Czech Academy of Sciences Publication Activity Database

    Ondrejkovič, Petr; Márton, Pavel; Guennou, Mael; Setter, N.; Hlinka, Jiří

    2013-01-01

    Roč. 88, č. 2 (2013), "024114-1"-"024114-9" ISSN 1098-0121 Grant - others:7th Framework Programme(XE) 268058 Institutional support: RVO:68378271 Keywords : piezoelectric properties * charged domain walls * domain structure * twinned ferroelectric Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.664, year: 2013 http://link. aps .org/doi/10.1103/PhysRevB.88.024114

  17. Band offsets and growth mode of molecular beam epitaxy grown MgO (111) on GaN (0002) by x-ray photoelectron spectroscopy

    Science.gov (United States)

    Craft, H. S.; Collazo, R.; Losego, M. D.; Mita, S.; Sitar, Z.; Maria, J.-P.

    2007-10-01

    MgO is a proposed dielectric for use as a tunneling barrier in devices integrating GaN and ferroelectric oxides. In this study, we present data regarding the growth mode and band offsets of MgO grown epitaxially on GaN (0002) surfaces using molecular beam epitaxy. Using in situ x-ray photoelectron spectroscopy (XPS) and molecular beam epitaxy, we determine, from sequential growth experiments, that the growth of MgO proceeds via the Volmer-Weber (three-dimensional) mode, and full coalescence of the film does not occur until approximately 12nm of MgO has been deposited. The observation of a three-dimensional growth mode is in agreement with previously published data. For the valence band offset, we find a value of 1.2±0.2eV, which corresponds to a 3.2eV conduction band offset. XPS measurements suggest a chemically abrupt interface and no effect on band lineup due to the slow coalescence behavior.

  18. Band offsets and growth mode of molecular beam epitaxy grown MgO (111) on GaN (0002) by x-ray photoelectron spectroscopy

    International Nuclear Information System (INIS)

    Craft, H. S.; Collazo, R.; Losego, M. D.; Mita, S.; Sitar, Z.; Maria, J.-P.

    2007-01-01

    MgO is a proposed dielectric for use as a tunneling barrier in devices integrating GaN and ferroelectric oxides. In this study, we present data regarding the growth mode and band offsets of MgO grown epitaxially on GaN (0002) surfaces using molecular beam epitaxy. Using in situ x-ray photoelectron spectroscopy (XPS) and molecular beam epitaxy, we determine, from sequential growth experiments, that the growth of MgO proceeds via the Volmer-Weber (three-dimensional) mode, and full coalescence of the film does not occur until approximately 12 nm of MgO has been deposited. The observation of a three-dimensional growth mode is in agreement with previously published data. For the valence band offset, we find a value of 1.2±0.2 eV, which corresponds to a 3.2 eV conduction band offset. XPS measurements suggest a chemically abrupt interface and no effect on band lineup due to the slow coalescence behavior

  19. Electrical properties of niobium doped Bi4Ti3O12-SrBi4Ti4O15 intergrowth ferroelectrics

    International Nuclear Information System (INIS)

    Parida, Geetanjali; Bera, J.

    2013-01-01

    Bismuth layer structured ferroelectrics (BLSFs) have attracted much attention because of their potential applications in non-volatile ferroelectric random access memories and high temperature piezoelectric. They are very attractive for these applications due to their fatigue free nature and environment friendly lead-free composition. BLSF crystal structure has layers of bismuth oxide and pseudo perovskite block stacked alternately along their c-direction, For commercial application, numerous efforts have been made to improve the electrical properties of BLSFs. Some effective approaches are: (i) doping at A-site, (ii) high valentcation doping at B-site and (iii) formation of intergrowth between different BLSFs. The intergrowth BLSFs are consist of regular stacking of one half the unit cell of m-member structure and one half the unit cell of (m+1) member BLSF structure along their c-axis. In this report, Nb-doped Bi 4 Ti 3 O 12 -SrBi 4 Ti 4 O 15 intergrowth ceramics have been prepared by modified oxalate route. XRD phase analysis confirmed the formation of single phase compound. Nb-doping does not affect the basic crystal structure of the intergrowth. SEM micrographs showed that the grain size of the ceramics decreases with Nb-doping. The temperature dependence of dielectric constant and losses was investigated in the temperature range 30 to 800℃ and frequency range 1 kHz to 1 MHz. With Nb-doping, the T c of the ferroelectrics reduces and peak permittivity increases. Doping also introduces small relaxor behaviour in the ferroelectrics. The dc conductivity of the ceramics decreases with doping. The remnant polarization (Pr) of the intergrowth ferroelectrics is increased with Nb doping. (author)

  20. Study of the B-site ion behaviour in the multiferroic perovskite bismuth iron chromium oxide

    Science.gov (United States)

    McBride, Bethany R.; Lieschke, Jonathon; Berlie, Adam; Cortie, David L.; Playford, Helen Y.; Lu, Teng; Narayanan, Narendirakumar; Withers, Ray L.; Yu, Dehong; Liu, Yun

    2018-04-01

    A simple, near-ambient pressure solid-state method was developed to nominally synthesize BiFe0.5Cr0.5O3. The procedure allowed the gram-scale production of multiferroic samples with appreciable purity and large amounts of Cr incorporation that were suitable for systematic structural investigation by neutron, X-ray, and electron diffraction in tandem with physical characterization of magnetic and ferroelectric properties. The rhombohedrally distorted perovskite phase was assigned to the space group R3c by way of X-ray and neutron powder diffraction analysis. Through a combination of magnetometry and muon spin relaxation, it is evident that there is magnetic ordering in the BFCO phase consistent with G-type antiferromagnetism and a TN ˜ 400 K. There is no clear evidence for chemical ordering of Fe and Cr in the B-site of the perovskite structure and this result is rationalized by density functional theory and bond valence simulations that show a lowered energy associated with a B-site disordered structure. We believe that our contribution of a new, low-complexity method for the synthesis of BFO type samples, and dialogue about realising certain types of ordering in oxide perovskite systems, will assist in the further development of multiferroics for next-generation devices.

  1. Polymer Ferroelectric Memory for Flexible Electronics

    KAUST Repository

    Khan, Mohd Adnan

    2013-01-01

    With the projected growth of the flexible and plastic electronics industry, there is renewed interest in the research community to develop high performance all-polymeric memory which will be an essential component of any electronic circuit. Some of the efforts in polymer memories are based on different mechanisms such as filamentary conduction, charge trapping effects, dipole alignment, and reduction-oxidation to name a few. Among these the leading candidate are those based on the mechanism of ferroelectricity. Polymer ferroelectric memory can be used in niche applications like smart cards, RFID tags, sensors etc. This dissertation will focus on novel material and device engineering to fabricate high performance low temperature polymeric ferroelectric memory for flexible electronics. We address and find solutions to some fundamental problems affecting all polymer ferroelectric memory like high coercive fields, fatigue and thermal stability issues, poor breakdown strength and poor p-type hole mobilities. Some of the strategies adopted in this dissertation are: Use of different flexible substrates, electrode engineering to improve charge injection and fatigue properties of ferroelectric polymers, large area ink jet printing of ferroelectric memory devices, use of polymer blends to improve insulating properties of ferroelectric polymers and use of oxide semiconductors to fabricate high mobility p-type ferroelectric memory. During the course of this dissertation we have fabricated: the first all-polymer ferroelectric capacitors with solvent modified highly conducting polymeric poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) [PEDOT:PSS] electrodes on plastic substrates with performance as good as devices with metallic Platinum-Gold electrodes on silicon substrates; the first all-polymer high performance ferroelectric memory on banknotes for security applications; novel ferroelectric capacitors based on blends of ferroelectric poly(vinylidene fluoride

  2. Polymer Ferroelectric Memory for Flexible Electronics

    KAUST Repository

    Khan, Mohd Adnan

    2013-11-01

    With the projected growth of the flexible and plastic electronics industry, there is renewed interest in the research community to develop high performance all-polymeric memory which will be an essential component of any electronic circuit. Some of the efforts in polymer memories are based on different mechanisms such as filamentary conduction, charge trapping effects, dipole alignment, and reduction-oxidation to name a few. Among these the leading candidate are those based on the mechanism of ferroelectricity. Polymer ferroelectric memory can be used in niche applications like smart cards, RFID tags, sensors etc. This dissertation will focus on novel material and device engineering to fabricate high performance low temperature polymeric ferroelectric memory for flexible electronics. We address and find solutions to some fundamental problems affecting all polymer ferroelectric memory like high coercive fields, fatigue and thermal stability issues, poor breakdown strength and poor p-type hole mobilities. Some of the strategies adopted in this dissertation are: Use of different flexible substrates, electrode engineering to improve charge injection and fatigue properties of ferroelectric polymers, large area ink jet printing of ferroelectric memory devices, use of polymer blends to improve insulating properties of ferroelectric polymers and use of oxide semiconductors to fabricate high mobility p-type ferroelectric memory. During the course of this dissertation we have fabricated: the first all-polymer ferroelectric capacitors with solvent modified highly conducting polymeric poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) [PEDOT:PSS] electrodes on plastic substrates with performance as good as devices with metallic Platinum-Gold electrodes on silicon substrates; the first all-polymer high performance ferroelectric memory on banknotes for security applications; novel ferroelectric capacitors based on blends of ferroelectric poly(vinylidene fluoride

  3. Electrode interface controlled electrical properties in epitaxial Pb(Zr{sub 0.52}Ti{sub 0.48})O{sub 3} films grown on Si substrates with SrTiO{sub 3} buffer layer

    Energy Technology Data Exchange (ETDEWEB)

    Boni, Andra Georgia, E-mail: andra.boni@infim.ro [National Institute of Materials Physics, Atomistilor 105bis, Magurele, Ilfov 77125 (Romania); University of Bucharest, Faculty of Physics, Magurele 077125 (Romania); Chirila, Cristina; Pasuk, Iuliana; Negrea, Raluca; Trupina, Lucian [National Institute of Materials Physics, Atomistilor 105bis, Magurele, Ilfov 77125 (Romania); Le Rhun, Gwenael [CEA, LETI, MINATEC Campus, 17 rue des Martyrs, 38054 Grenoble cedex 9 (France); Vilquin, Bertrand [Université de Lyon, Ecole Centrale de Lyon, INL, CNRS UMR5270, 36 avenue Guy de Collongue, F-69134 Ecully cedex (France); Pintilie, Ioana; Pintilie, Lucian [National Institute of Materials Physics, Atomistilor 105bis, Magurele, Ilfov 77125 (Romania)

    2015-10-30

    Electrical properties of ferroelectric capacitors based on PbZr{sub 0.52}Ti{sub 0.48}O{sub 3} thin films grown by pulsed laser deposition on silicon substrate with SrTiO{sub 3} buffer layer grown by molecular beam epitaxy were studied. A SrRuO{sub 3} layer was deposited as bottom electrode also by pulse laser deposition and Pt, Ir, Ru, SrRuO{sub 3} were used as top contacts. Electrical characterization comprised hysteresis and capacitance–voltage measurements in the temperature range from 150 K to 400 K. It was found that the macroscopic electrical properties are affected by the electrode interface, by the choice of the top electrode. However, even for metals with very different work functions (e.g. Pt and SrRuO{sub 3}) the properties of the top and bottom electrode interfaces remain fairly symmetric suggesting a strong influence from the bound polarization charges located near the interface. - Highlights: • Ferroelectric capacitors based on PbZr{sub 0.52}Ti{sub 0.48}O{sub 3} were deposited on Si substrate. • The structural characterization proved the epitaxial growth of the layers. • Macroscopic electrical properties are affected by the choice of the top electrode. • The difference on imprint field, dielectric constant are analyzed depending on the electrode-ferroelectric interface.

  4. Dielectric and thermodynamic measurements on the magnetoelectric perovskite EuTiO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Engelmayer, Johannes; Grams, Christoph; Hemberger, Joachim; Lorenz, Thomas [II. Physikalisches Institut, Universitaet zu Koeln (Germany)

    2016-07-01

    Various perovskite titanates ATiO{sub 3} are known to undergo ferroelectric phase transitions, e.g., for A=Ba,Pb,Cd. BaTiO{sub 3} is the only ferroelectric alkaline-earth titanate, since ferroelectric long-range order is suppressed in CaTiO{sub 3} and SrTiO{sub 3} by quantum fluctuations, which is referred to as quantum paraelectric behavior. The rare-earth titanate EuTiO{sub 3} is similar to SrTiO{sub 3}, since it has the same valencies (Eu{sup 2+},Ti{sup 4+}) and the same ionic radii. Both are cubic at room temperature and undergo a structural phase transition to tetragonal upon cooling. In contrast to the nonmagnetic Sr{sup 2+}, the half-filled 4f shell of Eu{sup 2+} with S=7/2 has a large magnetic moment of 7μ{sub B}. Below T{sub N}=5.5 K the localized 4f moments order antiferromagnetically, while rather small fields of 1.5 T are sufficient to saturate the magnetization. Here we present field- and temperature-dependent measurements of magnetization, specific heat, and thermal expansion, exhibiting characteristic anomalies at T{sub N}. Broadband measurements of the permittivity reveal the dynamics of polar domain walls at the onset of the structural phase transition, as well as the materials quantum paraelectric nature that is masked by high conductivity for low frequencies.

  5. A Ruddlesden-Popper-type layered perovskite, Na2Ca2Nb4O13

    International Nuclear Information System (INIS)

    Chiba, K.; Ishizawa, N.; Oishi, S.

    1999-01-01

    Single crystals of disodium dicalcium tetraniobium tridecaoxide, Na 2 Ca 2 Nb 4 O 13 , were grown by the flux method. The structure was determined in space group Bb2 1 m. Perovskite-type layers with the formula [(Ca 2 Na)Nb 4 O 13 ] - are concatenated by Na + cations near the interlayer, forming a Ruddlesden-Popper-type structure. The interlayer structure, composed of Na and O atoms, can be regarded as a rocksalt-type. NbO 6 octahedra are tilted about [010] and [001]. The off-centre displacement of Nb atoms suggests a ferroelectric nature along [010], with a calculated magnitude of polarization of 0.12 C m -2 . (orig.)

  6. Influence of KF substitution on the ferroelectric phase transition of lead titanate single crystals studied by Brillouin light scattering

    Directory of Open Access Journals (Sweden)

    Seonhyeop Shin

    2015-06-01

    Full Text Available The elastic properties of KF-substituted perovskite lead titanate (PbTiO3 were investigated by dielectric measurements and Brillouin light scattering. The ferroelectric phase transition occurred at substantially lower temperature due to KF substitution, which was attributed to the modification of the covalency in Pb–O and Ti–O bonds. The longitudinal acoustic (LA mode of KF-substituted PbTiO3 showed a frequency softening in the paraelectric phase, which was accompanied by increasing acoustic damping. This indicated that polarization fluctuations responsible for the acoustic anomalies were enhanced by KF substitution.

  7. Rules and mechanisms governing octahedral tilts in perovskites under pressure

    Science.gov (United States)

    Xiang, H. J.; Guennou, Mael; Íñiguez, Jorge; Kreisel, Jens; Bellaiche, L.

    2017-08-01

    The rotation of octahedra (octahedral tilting) is common in A B O3 perovskites and relevant to many physical phenomena, ranging from electronic and magnetic properties, metal-insulator transitions to improper ferroelectricity. Hydrostatic pressure is an efficient way to tune and control octahedral tiltings. However, the pressure behavior of such tiltings can dramatically differ from one material to another, with the origins of such differences remaining controversial. In this paper, we discover several new mechanisms and formulate a set of simple rules that allow us to understand how pressure affects oxygen octahedral tiltings via the use and analysis of first-principles results for a variety of compounds. Besides the known A -O interactions, we reveal that the interactions between specific B ions and oxygen ions contribute to the tilting instability. We explain the previously reported trend that the derivative of the oxygen octahedral tilting with respect to pressure (dR /dP ) usually decreases with both the tolerance factor and the ionization state of the A ion by illustrating the key role of A -O interactions and their change under pressure. Furthermore, three new mechanisms/rules are discovered, namely that (i) the octahedral rotations in A B O3 perovskites with empty low-lying d states on the B site are greatly enhanced by pressure, in order to lower the electronic kinetic energy; (ii) dR /dP is enhanced when the system possesses weak tilt instabilities, and (iii) for the most common phase exhibited by perovskites—the orthorhombic Pbnm state—the in-phase and antiphase octahedral rotations are not automatically both suppressed or both enhanced by the application of pressure because of a trilinear coupling between these two rotation types and an antipolar mode involving the A ions. We further predict that the polarization associated with the so-called hybrid improper ferroelectricity could be manipulated by hydrostatic pressure by indirectly controlling the

  8. Ferroelectricity at the nanoscale basics and applications

    CERN Document Server

    Fridkin, Vladimir

    2014-01-01

    This book examines a wide range of ferroelectric materials. It explains the theoretical background of ultrathin ferroelectric films,  presents applications of ferroelectric materials, and displays the mechanism of switching of nanosized ferroelectric films.

  9. Self-regulated growth of LaVO3 thin films by hybrid molecular beam epitaxy

    International Nuclear Information System (INIS)

    Zhang, Hai-Tian; Engel-Herbert, Roman; Dedon, Liv R.; Martin, Lane W.

    2015-01-01

    LaVO 3 thin films were grown on SrTiO 3 (001) by hybrid molecular beam epitaxy. A volatile metalorganic precursor, vanadium oxytriisopropoxide (VTIP), and elemental La were co-supplied in the presence of a molecular oxygen flux. By keeping the La flux fixed and varying the VTIP flux, stoichiometric LaVO 3 films were obtained for a range of cation flux ratios, indicating the presence of a self-regulated growth window. Films grown under stoichiometric conditions were found to have the largest lattice parameter, which decreased monotonically with increasing amounts of excess La or V. Energy dispersive X-ray spectroscopy and Rutherford backscattering measurements were carried out to confirm film compositions. Stoichiometric growth of complex vanadate thin films independent of cation flux ratios expands upon the previously reported self-regulated growth of perovskite titanates using hybrid molecular beam epitaxy, thus demonstrating the general applicability of this growth approach to other complex oxide materials, where a precise control over film stoichiometry is demanded by the application

  10. Hierarchy and scaling behavior of multi-rank domain patterns in ferroelectric K0.9Na0.1NbO3 strained films

    Science.gov (United States)

    Braun, Dorothee; Schmidbauer, Martin; Hanke, Michael; Schwarzkopf, Jutta

    2018-01-01

    The formation process of a ferroelectric multi-rank domain pattern in the thickness range of 7-52 nm is investigated for monoclinic K0.9Na0.1NbO3 strained epitaxial films on (110) NdScO3 substrates. Although the elastic strain energy density is degenerated for two pseudocubic orientations, a distinctive hierarchy of domain evolution is observed with exclusive in-plane a1a2 domains for very thin films and the retarded onset of a ferroelectric MC phase at larger film thickness. This is accompanied by a thickness dependent transformation from stripe domains to a herringbone pattern and, eventually, for the thickest film, to a checkerboard-like structure. These transformations in the domain arrangement and width are correlated to energetic aspects as depolarization field and anisotropic strain relaxation in the film. While for the MC domains plastic strain relaxation is throughout observed, the a1a2 domains show a two-step strain relaxation mechanism starting with an in-plane elastic shearing, which is followed by plastic lattice relaxation. Our results highlight a pathway for engineering and patterning of periodic ferroelectric domain structures.

  11. Novel ferroelectric capacitor for non-volatile memory storage and biomedical tactile sensor applications

    International Nuclear Information System (INIS)

    Liu, Shi Yang; Chua, Lynn; Tan, Kian Chuan; Valavan, S.E.

    2010-01-01

    We report on novel ferroelectric thin film compositions for use in non-volatile memory storage and biomedical tactile sensor applications. The lead zirconate titanate (PZT) composition was modified by lanthanum (La 3+ ) (PLZT) and vanadium (V 5+ ) (PZTV, PLZTV) doping. Hybrid films with PZTV and PLZTV as top layers are also made using seed layers of differing compositions using sol-gel and spin coating methods. La 3+ doping decreased the coercive field, polarization and leakage current, while increasing the relative permittivity. V 5+ doping, while having similar effects, results in an enhanced polarization, with comparable dielectric loss characteristics. Complex doping of both La 3+ and V 5+ in PLZTV, while reducing the polarization relative to PZTV, significantly decreases the coercive field. Hybrid films have a greater uniformity of grain formation than non-hybrid films, thus decreasing the coercive field, leakage current and polarization fatigue while increasing the relative permittivity. Analysis using X-ray diffraction (XRD) verified the retention of the PZT perovskite structure in the novel films. PLZT/PZTV has been identified as an optimal ferroelectric film composition due to its desirable ferroelectric, fatigue and dielectric properties, including the highest observed remnant polarization (P r ) of ∼ 25 μC/cm 2 , saturation polarization (P sat ) of ∼ 58 μC/cm 2 and low coercive field (E c ) of ∼ 60 kV/cm at an applied field of ∼ 1000 kV/cm, as well as a low leakage current density of ∼ 10 -5 A/cm 2 at 500 kV/cm and fatigue resistance of up to ∼ 10 10 switching cycles.

  12. Stress-Induced Cubic-to-Hexagonal Phase Transformation in Perovskite Nanothin Films.

    Science.gov (United States)

    Cao, Shi-Gu; Li, Yunsong; Wu, Hong-Hui; Wang, Jie; Huang, Baoling; Zhang, Tong-Yi

    2017-08-09

    The strong coupling between crystal structure and mechanical deformation can stabilize low-symmetry phases from high-symmetry phases or induce novel phase transformation in oxide thin films. Stress-induced structural phase transformation in oxide thin films has drawn more and more attention due to its significant influence on the functionalities of the materials. Here, we discovered experimentally a novel stress-induced cubic-to-hexagonal phase transformation in the perovskite nanothin films of barium titanate (BaTiO 3 ) with a special thermomechanical treatment (TMT), where BaTiO 3 nanothin films under various stresses are annealed at temperature of 575 °C. Both high-resolution transmission electron microscopy and Raman spectroscopy show a higher density of hexagonal phase in the perovskite thin film under higher tensile stress. Both X-ray photoelectron spectroscopy and electron energy loss spectroscopy does not detect any change in the valence state of Ti atoms, thereby excluding the mechanism of oxygen vacancy induced cubic-to-hexagonal (c-to-h) phase transformation. First-principles calculations show that the c-to-h phase transformation can be completed by lattice shear at elevated temperature, which is consistent with the experimental observation. The applied bending plus the residual tensile stress produces shear stress in the nanothin film. The thermal energy at the elevated temperature assists the shear stress to overcome the energy barriers during the c-to-h phase transformation. The stress-induced phase transformation in perovskite nanothin films with TMT provides materials scientists and engineers a novel approach to tailor nano/microstructures and properties of ferroelectric materials.

  13. Ferroelectric devices

    CERN Document Server

    Uchino, Kenji

    2009-01-01

    Updating its bestselling predecessor, Ferroelectric Devices, Second Edition assesses the last decade of developments-and setbacks-in the commercialization of ferroelectricity. Field pioneer and esteemed author Uchino provides insight into why this relatively nascent and interdisciplinary process has failed so far without a systematic accumulation of fundamental knowledge regarding materials and device development.Filling the informational void, this collection of information reviews state-of-the-art research and development trends reflecting nano and optical technologies, environmental regulat

  14. Reversal of lattice, electronic structure, and magnetism in epitaxial SrCoOx thin films

    Science.gov (United States)

    Jeen, H.; Choi, W. S.; Lee, J. H.; Cooper, V. R.; Lee, H. N.; Seo, S. S. A.; Rabe, K. M.

    2014-03-01

    SrCoOx (x = 2.5 - 3.0, SCO) is an ideal material to study the role of oxygen content for electronic structure and magnetism, since SCO has two distinct topotactic phases: the antiferromagnetic insulating brownmillerite SrCoO2.5 and the ferromagnetic metallic perovskite SrCoO3. In this presentation, we report direct observation of a reversible lattice and electronic structure evolution in SrCoOx epitaxial thin films as well as different magnetic and electronic ground states between the topotactic phases.[2] By magnetization measurements, optical absorption, and transport measurements drastically different electronic and magnetic ground states are found in the epitaxially grown SrCoO2.5 and SrCoO3 thin films by pulsed laser epitaxy. First-principles calculations confirm substantial, which originate from the modification in the Co valence states and crystallographic structures. By real-time spectroscopic ellipsometry, the two electronically and magnetically different phases can be reversibly changed by changing the ambient pressure at greatly reduced temperatures. Our finding provides an important pathway to understanding the novel oxygen-content-dependent phase transition uniquely found in multivalent transition metal oxides. The work was supported by the U.S. Department of Energy, Basic Energy Sciences, Materials Sciences and Engineering Division.

  15. Polar octahedral rotations: A path to new multifunctional materials

    International Nuclear Information System (INIS)

    Benedek, Nicole A.; Mulder, Andrew T.; Fennie, Craig J.

    2012-01-01

    Perovskite ABO 3 oxides display an amazing variety of phenomena that can be altered by subtle changes in the chemistry and internal structure, making them a favorite class of materials to explore the rational design of novel properties. Here we highlight a recent advance in which rotations of the BO 6 octahedra give rise to a novel form of ferroelectricity – hybrid improper ferroelectricity. Octahedral rotations also strongly influence other structural, magnetic, orbital, and electronic degrees of freedom in perovskites and related materials. Octahedral rotation-driven ferroelectricity consequently has the potential to robustly control emergent phenomena with an applied electric field. The concept of ‘functional’ octahedral rotations is introduced and the challenges for materials chemistry and the possibilities for new rotation-driven phenomena in multifunctional materials are explored. - Graphical abstract: A 3 B 2 O 7 and (A/A′)B 2 O 6 are two types of layered perovskites in which octahedral rotations induce ferroelectricity. Highlights: ► Recent progress on achieving ferroelectricity from rotations of the BO 6 octahedra in ABO 3 perovskite oxides is reviewed. ► The atomic scale layering of Pnma perovskites in two different ways leads to alternative structure realizations. ► The concept of ‘functional’ octahedral rotations is introduced as a path to electric-field control of emergent phenomena.

  16. Reversible and nonvolatile ferroelectric control of two-dimensional electronic transport properties of ZrCuSiAs-type copper oxyselenide thin films with a layered structure

    Science.gov (United States)

    Zhao, Xu-Wen; Gao, Guan-Yin; Yan, Jian-Min; Chen, Lei; Xu, Meng; Zhao, Wei-Yao; Xu, Zhi-Xue; Guo, Lei; Liu, Yu-Kuai; Li, Xiao-Guang; Wang, Yu; Zheng, Ren-Kui

    2018-05-01

    Copper-based ZrCuSiAs-type compounds of LnCuChO (Ln =Bi and lanthanides, Ch =S , Se, Te) with a layered crystal structure continuously attract worldwide attention in recent years. Although their high-temperature (T ≥ 300 K) electrical properties have been intensively studied, their low-temperature electronic transport properties are little known. In this paper, we report the integration of ZrCuSiAs-type copper oxyselenide thin films of B i0.94P b0.06CuSeO (BPCSO) with perovskite-type ferroelectric Pb (M g1 /3N b2 /3 ) O3-PbTi O3 (PMN-PT) single crystals in the form of ferroelectric field effect devices that allow us to control the electronic properties (e.g., carrier density, magnetoconductance, dephasing length, etc.) of BPCSO films in a reversible and nonvolatile manner by polarization switching at room temperature. Combining ferroelectric gating and magnetotransport measurements with the Hikami-Larkin-Nagaoka theory, we demonstrate two-dimensional (2D) electronic transport characteristics and weak antilocalization effect as well as strong carrier-density-mediated competition between weak antilocalization and weak localization in BPCSO films. Our results show that ferroelectric gating using PMN-PT provides an effective and convenient approach to probe the carrier-density-related 2D electronic transport properties of ZrCuSiAs-type copper oxyselenide thin films.

  17. A silicon doped hafnium oxide ferroelectric p–n–p–n SOI tunneling field–effect transistor with steep subthreshold slope and high switching state current ratio

    Directory of Open Access Journals (Sweden)

    Saeid Marjani

    2016-09-01

    Full Text Available In this paper, a silicon–on–insulator (SOI p–n–p–n tunneling field–effect transistor (TFET with a silicon doped hafnium oxide (Si:HfO2 ferroelectric gate stack is proposed and investigated via 2D device simulation with a calibrated nonlocal band–to–band tunneling model. Utilization of Si:HfO2 instead of conventional perovskite ferroelectrics such as lead zirconium titanate (PbZrTiO3 and strontium bismuth tantalate (SrBi2Ta2O9 provides compatibility to the CMOS process as well as improved device scalability. By using Si:HfO2 ferroelectric gate stack, the applied gate voltage is effectively amplified that causes increased electric field at the tunneling junction and reduced tunneling barrier width. Compared with the conventional p–n–p–n SOI TFET, the on–state current and switching state current ratio are appreciably increased; and the average subthreshold slope (SS is effectively reduced. The simulation results of Si:HfO2 ferroelectric p–n–p–n SOI TFET show significant improvement in transconductance (∼9.8X enhancement at high overdrive voltage and average subthreshold slope (∼35% enhancement over nine decades of drain current at room temperature, indicating that this device is a promising candidate to strengthen the performance of p–n–p–n and conventional TFET for a switching performance.

  18. A novel perovskite oxide chemically designed to show multiferroic phase boundary with room-temperature magnetoelectricity

    Science.gov (United States)

    Fernández-Posada, Carmen M.; Castro, Alicia; Kiat, Jean-Michel; Porcher, Florence; Peña, Octavio; Algueró, Miguel; Amorín, Harvey

    2016-09-01

    There is a growing activity in the search of novel single-phase multiferroics that could finally provide distinctive magnetoelectric responses at room temperature, for they would enable a range of potentially disruptive technologies, making use of the ability of controlling polarization with a magnetic field or magnetism with an electric one (for example, voltage-tunable spintronic devices, uncooled magnetic sensors and the long-searched magnetoelectric memory). A very promising novel material concept could be to make use of phase-change phenomena at structural instabilities of a multiferroic state. Indeed, large phase-change magnetoelectric response has been anticipated by a first-principles investigation of the perovskite BiFeO3-BiCoO3 solid solution, specifically at its morphotropic phase boundary between multiferroic polymorphs of rhombohedral and tetragonal symmetries. Here, we report a novel perovskite oxide that belongs to the BiFeO3-BiMnO3-PbTiO3 ternary system, chemically designed to present such multiferroic phase boundary with enhanced ferroelectricity and canted ferromagnetism, which shows distinctive room-temperature magnetoelectric responses.

  19. High-pressure structure of Pb-based relaxor ferroelectrics

    Energy Technology Data Exchange (ETDEWEB)

    Maier, Bernd J.; Mihailova, Boriana; Paulmann, Carsten; Welsch, Anna-Maria; Bismayer, Ulrich [Mineralogisch-Petrographisches Institut, Universitaet Hamburg (Germany); Angel, Ross J. [Crystallography Laboratory, Virgina Tech, Blacksburg (United States); Marshall, William G. [ISIS Neutron Facility, STFC Rutherford Appleton Laboratory, Chilton, Didcot, Oxon (United Kingdom); Engel, Jens M. [Institut fuer Werkstoffwissenschaft, Technische Universitaet Dresden (Germany); Gospodinov, Marin [Institute of Solid State Physics, Bulgarian Academy of Sciences, Sofia (Bulgaria); Petrova, Dimitrina [Institute of Solid State Physics, Bulgarian Academy of Sciences, Sofia (Bulgaria); South-West University Neofit Rilski, Blagoevgrad (Bulgaria)

    2010-07-01

    The pressure-induced phase transitions that occur in the perovskite-type relaxor ferroelectric PbSc{sub 0.5}Ta{sub 0.5}O{sub 3} (PST) and Pb{sub 0.78}Ba{sub 0.22}Sc{sub 0.5}Ta{sub 0.5}O{sub 3} (PST-Ba) were studied with combined neutron powder diffraction and single-crystal X-ray diffraction. An increase in the intensities of h,k,l=all odd reflections is observed while the intensity of h,h,h peaks, h=2n+1, does not change with pressure, indicating a glide-plane pseudo-symmetry of the structural distortion along the left angle 111 right angle cubic directions. Rietveld refinement to the neutron powder data shows that the high-pressure phase has either R anti 3c or R anti 3 symmetry, depending on whether the presence of 1:1 octahedral cation ordering is neglected or taken into account, and comprises anti-phase octahedral tilts of type a{sup -}a{sup -}a{sup -} that continuously evolve with pressure.

  20. Tuning piezoelectric properties through epitaxy of La2Ti2O7 and related thin films.

    Science.gov (United States)

    Kaspar, Tiffany C; Hong, Seungbum; Bowden, Mark E; Varga, Tamas; Yan, Pengfei; Wang, Chongmin; Spurgeon, Steven R; Comes, Ryan B; Ramuhalli, Pradeep; Henager, Charles H

    2018-02-14

    Current piezoelectric sensors and actuators are limited to operating temperatures less than ~200 °C due to the low Curie temperature of the piezoelectric material. Strengthening the piezoelectric coupling of high-temperature piezoelectric materials, such as La 2 Ti 2 O 7 (LTO), would allow sensors to operate across a broad temperature range. The crystalline orientation and piezoelectric coupling direction of LTO thin films can be controlled by epitaxial matching to SrTiO 3 (001), SrTiO 3 (110), and rutile TiO 2 (110) substrates via pulsed laser deposition. The structure and phase purity of the films are investigated by x-ray diffraction and scanning transmission electron microscopy. Piezoresponse force microscopy is used to measure the in-plane and out-of-plane piezoelectric coupling in the films. The strength of the out-of-plane piezoelectric coupling can be increased when the piezoelectric direction is rotated partially out-of-plane via epitaxy. The strongest out-of-plane coupling is observed for LTO/STO(001). Deposition on TiO 2 (110) results in epitaxial La 2/3 TiO 3 , an orthorhombic perovskite of interest as a microwave dielectric material and an ion conductor. La 2/3 TiO 3 can be difficult to stabilize in bulk form, and epitaxial stabilization on TiO 2 (110) is a promising route to realize La 2/3 TiO 3 for both fundamental studies and device applications. Overall, these results confirm that control of the crystalline orientation of epitaxial LTO-based materials can govern the resulting functional properties.

  1. Absence of low temperature phase transitions and enhancement of ferroelectric transition temperature in highly strained BaTiO{sub 3} epitaxial films grown on MgO Substrates

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Satish; Kumar, Dhirendra; Sathe, V. G., E-mail: vasant@csr.res.in [UGC-DAE Consortium for Scientific Research, University Campus, Khandwa Road, Indore 452001 (India); Kumar, Ravi; Sharma, T. K. [Semiconductor Physics and Devices Lab, Raja Ramanna Centre for Advanced Technology, Indore 452013 (India)

    2015-04-07

    Recently, a large enhancement in the ferroelectric transition temperature of several oxides is reported by growing the respective thin films on appropriate substrates. This phenomenon is correlated with high residual strain in thin films often leading to large increase in the tetragonality of their crystal structure. However, such an enhancement of transition temperature is usually limited to very thin films of ∼10 nm thickness. Here, we report growth of fully strained epitaxial thin films of BaTiO{sub 3} of 400 nm thickness, which are coherently grown on MgO substrates by pulsed laser deposition technique. Conventional high resolution x-ray diffraction and also the reciprocal space map measurements confirm that the film is fully strained with in-plane tensile strain of 5.5% that dramatically increases the tetragonality to 1.05. Raman measurements reveal that the tetragonal to cubic structural phase transition is observed at 583 K, which results in an enhancement of ∼200 K. Furthermore, temperature dependent Raman studies on these films corroborate absence of all the low temperature phase transitions. Numerical calculations based on thermodynamical model predict a value of the transition temperature that is greater than 1500 °C. Our experimental results are therefore in clear deviation from the existing strain dependent phase diagrams.

  2. Integration of epitaxial Pb(Zr{sub 0.52}Ti{sub 0.48})O{sub 3} films on GaN/AlGaN/GaN/Si(111) substrates using rutile TiO{sub 2} buffer layers

    Energy Technology Data Exchange (ETDEWEB)

    Elibol, K. [MESA + Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500AE Enschede (Netherlands); Nguyen, M.D. [MESA + Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500AE Enschede (Netherlands); SolMateS B.V., Drienerlolaan 5, Building 6, 7522NB Enschede (Netherlands); International Training Institute for Materials Science, Hanoi University of Science and Technology, No.1 Dai Co Viet road, Hanoi 10000 (Viet Nam); Hueting, R.J.E. [MESA + Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500AE Enschede (Netherlands); Gravesteijn, D.J. [MESA + Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500AE Enschede (Netherlands); NXP Semiconductors Research, High Tech Campus 46, 5656AE Eindhoven (Netherlands); Koster, G., E-mail: g.koster@utwente.nl [MESA + Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500AE Enschede (Netherlands); Rijnders, G. [MESA + Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500AE Enschede (Netherlands)

    2015-09-30

    The integration of ferroelectric layers on gallium nitride (GaN) offers a great potential for various applications. Lead zirconate titanate (PZT), in particular Pb(Zr{sub 0.52}Ti{sub 0.48})O{sub 3}, is an interesting candidate. For that a suitable buffer layer should be grown on GaN in order to prevent the reaction between PZT and GaN, and to obtain PZT with a preferred orientation and phase. Here, we study pulsed laser deposited (100) rutile titanium oxide (R-TiO{sub 2}) as a potential buffer layer candidate for ferroelectric PZT. For this purpose, the growth, morphology and the surface chemical composition of R-TiO{sub 2} films were analyzed by reflection high-energy electron diffraction, atomic force microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. We find optimally (100) oriented R-TiO{sub 2} growth on GaN (0002) using a 675 °C growth temperature and 2 Pa O{sub 2} deposition pressure as process conditions. More importantly, the R-TiO{sub 2} buffer layer grown on GaN/Si substrates prevents the unwanted formation of the PZT pyrochlore phase. Finally, the remnant polarization and coercive voltage of the PZT film on TiO{sub 2}/GaN/Si with an interdigitated-electrode structure were found to be 25.6 μC/cm{sup 2} and 8.1 V, respectively. - Highlights: • Epitaxial rutile TiO{sub 2} films were grown on GaN layer buffered Si substrate using pulsed laser deposition. • The rutile-TiO{sub 2} layer suppresses the formation of the pyrochlore phase in the epitaxial PZT film grown on GaN/Si. • An epitaxial PZT film on GaN/Si substrate with rutile TiO{sub 2} buffer layer exhibits good ferroelectric properties.

  3. Enhancement of the saturation mobility in a ferroelectric-gated field-effect transistor by the surface planarization of ferroelectric film

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Woo Young, E-mail: semigumi@kaist.ac.kr [Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology (KAIST), 373-1, Guseong-dong, Yuseong-gu, Daejeon 305-701 (Korea, Republic of); Jeon, Gwang-Jae; Kang, In-Ku; Shim, Hyun Bin; Lee, Hee Chul [Department of Electrical Engineering, Korea Advanced Institute of Science and Technology (KAIST), 373-1, Guseong-dong, Yuseong-gu, Daejeon 305-701 (Korea, Republic of)

    2015-09-30

    Ferroelectricity refers to the property of a dielectric material to undergo spontaneous polarization which originates from the crystalline phase. Hence, ferroelectric materials have a certain degree of surface roughness when they are formed as a thin film. A high degree of surface roughness may cause unintended phenomena when the ferroelectric material is used in electronic devices. Specifically, the quality of subsequently deposited film could be affected by the rough surface. The present study reports that the surface roughness of ferroelectric polymer film can be reduced by a double-spin-coating method of a solution, with control of the solubility of the solution. At an identical thickness of 350 nm, double-spin-coated ferroelectric film has a root-mean-square roughness of only 3 nm, while for single-spin-coated ferroelectric film this value is approximately 16 nm. A ferroelectric-gated field-effect transistor was fabricated using the proposed double-spin-coating method, showing a maximum saturation mobility as much as seven-fold than that of a transistor fabricated with single-spin-coated ferroelectric film. The enhanced saturation mobility could be explained by the Poole–Frenkel conduction mechanism. The proposed method to reduce the surface roughness of ferroelectric film would be useful for high performance organic electronic devices, including crystalline-phase dielectric film. - Highlights: • Single and double-layer solution-processed polymer ferroelectric films were obtained. • Adjusting the solvent solubility allows making double-layer ferroelectric (DF) films. • The DF film has a smoother surface than single-layer ferroelectric (SF) film. • DF-gated transistor has faster saturation mobility than SF-based transistor. • Solvent solubility adjustment led to higher performance organic devices.

  4. Influence of plasma pressure on the growth characteristics and ferroelectric properties of sputter-deposited PZT thin films

    International Nuclear Information System (INIS)

    Bose, A.; Maity, T.; Bysakh, S.; Seal, A.; Sen, Suchitra

    2010-01-01

    PZT thin films of thickness (320-1040) nm were synthesized on Si/SiO 2 /Ti/Pt multilayered substrates by radio frequency magnetron sputtering. The influence of plasma pressure in the range of (0.24-4.9) Pa, during deposition, on the structural, electrical and ferroelectric properties of the PZT films was systematically studied. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and cross-sectional transmission electron microscopy (XTEM) were employed for structural study. Nano-probe Energy Dispersive (EDX) line scanning was employed to investigate the elemental distribution across the film-bottom electrode interface. I-V characteristics and polarization-electric field (P-E) hysteresis loop of the films were measured. The study reveals that the plasma pressure has a strong influence on the evolution and texture of the ferroelectric perovskite phase and microstructure of the films. At an optimum plasma pressure of 4.1 Pa, PZT films are grown with 93% perovskite phase with (1 1 1) preferred orientation and uniform granular microstructure. These films show a saturation polarization of 67 μC/cm 2 , remnant polarization of 30 μC/cm 2 and coercive field of 28 kV/cm which, according to the literature, seem to be suitable for device applications. Transmission electron microscopy (TEM) study shows that at a plasma pressure of 4.1 Pa, the PZT/bottom Pt interface is sharp and no amorphous interlayer is formed at the interface. At a higher plasma pressure of 4.9 Pa, poor I-V and P-E hysteresis loop are observed which are interpreted as due to an amorphous interlayer at the film-bottom electrode interface which is possibly enriched in Pb, Zr, O and Pt.

  5. Polarized Raman scattering study of PSN single crystals and epitaxial thin films

    Directory of Open Access Journals (Sweden)

    J. Pokorný

    2015-06-01

    Full Text Available This paper describes a detailed analysis of the dependence of Raman scattering intensity on the polarization of the incident and inelastically scattered light in PbSc0.5Nb0.5O3 (PSN single crystals and epitaxially compressed thin films grown on (100-oriented MgO substrates. It is found that there are significant differences between the properties of the crystals and films, and that these differences can be attributed to the anticipated structural differences between these two forms of the same material. In particular, the scattering characteristics of the oxygen octahedra breathing mode near 810 cm-1 indicate a ferroelectric state for the crystals and a relaxor state for the films, which is consistent with the dielectric behaviors of these materials.

  6. Constructing Efficient and Stable Perovskite Solar Cells via Interconnecting Perovskite Grains.

    Science.gov (United States)

    Hou, Xian; Huang, Sumei; Ou-Yang, Wei; Pan, Likun; Sun, Zhuo; Chen, Xiaohong

    2017-10-11

    A high-quality perovskite film with interconnected perovskite grains was obtained by incorporating terephthalic acid (TPA) additive into the perovskite precursor solution. The presence of TPA changed the crystallization kinetics of the perovskite film and promoted lateral growth of grains in the vicinity of crystal boundaries. As a result, sheet-shaped perovskite was formed and covered onto the bottom grains, which made some adjacent grains partly merge together to form grains-interconnected perovskite film. Perovskite solar cells (PSCs) with TPA additive exhibited a power conversion efficiency (PCE) of 18.51% with less hysteresis, which is obviously higher than that of pristine cells (15.53%). PSCs without and with TPA additive retain 18 and 51% of the initial PCE value, respectively, aging for 35 days exposed to relative humidity 30% in air without encapsulation. Furthermore, MAPbI 3 film with TPA additive shows superior thermal stability to the pristine one under 100 °C baking. The results indicate that the presence of TPA in perovskite film can greatly improve the performance of PSCs as well as their moisture resistance and thermal stability.

  7. Coexistence of Weak Ferromagnetism and Polar Lattice Distortion in Epitaxial NiTiO3 thin films of the LiNbO3-Type Structure

    Energy Technology Data Exchange (ETDEWEB)

    Varga, Tamas [Environmental Molecular Sciences Lab., Richland, WA (United States); Droubay, Timothy C. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Bowden, Mark E. [Environmental Molecular Sciences Lab., Richland, WA (United States); Colby, Robert J. [Environmental Molecular Sciences Lab., Richland, WA (United States); Manandhar, Sandeep [Environmental Molecular Sciences Lab., Richland, WA (United States); Shutthanandan, Vaithiyalingam [Environmental Molecular Sciences Lab., Richland, WA (United States); Hu, Dehong [Environmental Molecular Sciences Lab., Richland, WA (United States); Kabius, Bernd C. [Environmental Molecular Sciences Lab., Richland, WA (United States); Apra, Edoardo [Environmental Molecular Sciences Lab., Richland, WA (United States); Shelton, William A. [Environmental Molecular Sciences Lab., Richland, WA (United States); Chambers, Scott A. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2013-04-15

    We report the magnetic and structural characteristics of epitaxial NiTiO3 films grown by pulsed laser deposition that are isostructural with acentric LiNbO3 (space group R3c). Optical second harmonic generation and magnetometry demonstrate lattice polarization at room temperature and weak ferromagnetism below 250 K, respectively. These results appear to be consistent with earlier predictions from first-principles calculations of the coexistence of ferroelectricity and weak ferromagnetism in a series of transition metal titanates crystallizing in the LiNbO3 structure. This acentric form of NiTiO3 is believed to be one of the rare examples of ferroelectrics exhibiting weak ferromagnetism generated by a Dzyaloshinskii-Moriya interaction.

  8. Ferroelectric, magnetic and structural studies of the Bi{sub 4}LaSmFe{sub 2}Ti{sub 3}O{sub 18} multiferroic material

    Energy Technology Data Exchange (ETDEWEB)

    Alarcón-Suesca, C.E. [Fachgebiet Synthese und Charakterisierung Innovatiert Materialien, Chemistry Department, Technische Universität München, Lichtenbergstrasse D-85748, Garching (Germany); Grupo de Física de Nuevos Materiales, Departamento de Física, Universidad Nacional de Colombia, AA 5997 Bogotá DC (Colombia); Cardona-Vásquez, J.A. [Grupo de Física de Nuevos Materiales, Departamento de Física, Universidad Nacional de Colombia, AA 5997 Bogotá DC (Colombia); Salcedo-Fontecha, J.P.; Vargas-Jiménez, A. [Maestría en Ciencias Física, Departamento de Física, Universidad Nacional de Colombia, AA 5997 Bogotá DC (Colombia); Landínez-Téllez, D.A.; Roa-Rojas, J. [Grupo de Física de Nuevos Materiales, Departamento de Física, Universidad Nacional de Colombia, AA 5997 Bogotá DC (Colombia)

    2014-12-15

    We report the synthesis and characterization of the new Bi{sub 4}LaSmFe{sub 2}Ti{sub 3}O{sub 18} ferroelectric ceramic. X-ray characterization reveals reflections for layered perovskite Aurivillius system. Rietveld analyses of the powder pattern shows that Bi{sub 4}LaSmFe{sub 2}Ti{sub 3}O{sub 18} crystallizes in orthorhombic structure, which corresponds to the space group F2/mm (#42), with lattice parameters a=5.4240(16) Ǻ, b=5.4078(23) Ǻ and c=50.2440(12) Ǻ. Scanning electron microscopy (SEM) reveals the formation of dense material with plate-like morphology. Electric polarization curves were measured by means of a radiant ferroelectric tester, at room temperature in bulk samples and exhibit an intrinsic ferroelectric response, even at low applied fields. Measurements of the magnetization as a function of temperature after Zero field cooling and field cooling were carried out by using a MPMS Quantum Design SQUID magnetometer. We found an effective magnetic moment of 7.95 µB, which is 95.8% in agreement with the expected value calculated from Hund's rules. Magnetization curves as the function of applied fields reveal an incipient hysteretic behavior at room temperature.

  9. The role of Pb in piezoelectrics and possible substitutions for it

    Science.gov (United States)

    Singh, D. J.; Ghita, M.; Halilov, S. V.; Fornari, M.

    2005-09-01

    The interplay between the various patterns of structural instability that are related to the electromechanical coupling in ferroelectric perovskites is discussed using results of density functional based first principles calculations. We focus on two main issues: (1) the competition between tetragonal and rhombohedral ferroelectric states in A-site driven (tolerance factor, ttolerance factor perovskites based on frustration is discussed.

  10. AB initio energetics of lanthanum substitution in ferroelectric bismuth titanate

    International Nuclear Information System (INIS)

    Shah, S.H.

    2012-01-01

    Density functional theory based electronic structure calculations play a vital role in understanding, controlling and optimizing physical properties of materials at microscopic level. In present study system of interest is bismuth titanate (Bi/sub 4/Ti/sub 3/O/sub 12/)/(BIT) which has wide range of applications such as a high temperature piezoelectric and one of the best material for memory devices. However, it also suffers from serious issues such as oxygen vacancies which degrade its performance as a memory element and piezoelectric material. In this context, the bulk and defect properties of orthorhombic bismuth titanate (Bi/sub 4/Ti/sub 3/O/sub 12/) and bismuth lanthanum titanate (Bi/sub 3.25/La/sub 0.75/Ti/sub 3/O/sub 12/)/(BLT, x=0.75) were investigated by using first principles calculations and atomistic thermodynamics. Heats of formation, valid chemical conditions for synthesis, lanthanum substitution energies and oxygen and bismuth vacancy formation energies were computed. The study improves understanding of how native point defects and substitutional impurities influence the ferroelectric properties of these layered perovskite materials. It was found that lanthanum incorporation could occur on either of the two distinct bismuth sites in the structure and that the effect of substitution is to increase the formation energy of nearby native oxygen vacancies. The results provide direct atomistic evidence over a range of chemical conditions for the suggestion that lanthanum incorporation reduces the oxygen vacancy concentration. Oxygen vacancies contribute to ferroelectric fatigue by interacting strongly with domain walls and therefore a decrease in their concentration is beneficial. (orig./A.B.)

  11. Ab-initio study of the dielectric response of high-permittivity perovskites for energy storage

    International Nuclear Information System (INIS)

    Do-Amaral-De-Andrade-Sophia, Gustavo

    2014-01-01

    Many of materials based on transition metals have a wide range of applications, such as the storage of energy, due to their peculiar properties (high-dielectric constants, ferro-electricity,...). The knowledge of their bulk properties is essential in designing targeted devices with high performance. For instance, ABO 3 perovskites are peculiarly interesting for their atomic structural flexibility, allowing high number of atoms substitution and giving them specific chemical and electrical properties compared to the pure compounds. In this context, first principles calculations can be useful to understand the structural and electronic properties of these materials. The pressure-induced giant dielectric anomaly of ABO 3 perovskites has been investigated at the ab initio level. Its mechanism has been analyzed in terms of thermodynamic phase stability, structural and phonon contributions and Born effective charges. It is shown that the IR-active soft phonon is responsible for the anomaly. This mode always involves a displacement and a deformation of the oxygen octahedra, while the roles of A and B ions vary among the materials and between high- and low-pressure phase transitions. A sharp increase in the phonon amplitude near the phase transition gives rise to the dielectric anomaly. The use of hybrid functionals is required for agreement with experimental data. The calculations show that the dielectric anomaly in the pressure-induced phase transitions of these perovskites is a property of the bulk material. (author)

  12. Factors Controlling the Redox Activity of Oxygen in Perovskites: From Theory to Application for Catalytic Reactions

    Directory of Open Access Journals (Sweden)

    Chunzhen Yang

    2017-05-01

    Full Text Available Triggering the redox reaction of oxygens has become essential for the development of (electro catalytic properties of transition metal oxides, especially for perovskite materials that have been envisaged for a variety of applications such as the oxygen evolution or reduction reactions (OER and ORR, respectively, CO or hydrocarbons oxidation, NO reduction and others. While the formation of ligand hole for perovskites is well-known for solid state physicists and/or chemists and has been widely studied for the understanding of important electronic properties such as superconductivity, insulator-metal transitions, magnetoresistance, ferroelectrics, redox properties etc., oxygen electrocatalysis in aqueous media at low temperature barely scratches the surface of the concept of oxygen ions oxidation. In this review, we briefly explain the electronic structure of perovskite materials and go through a few important parameters such as the ionization potential, Madelung potential, and charge transfer energy that govern the oxidation of oxygen ions. We then describe the surface reactivity that can be induced by the redox activity of the oxygen network and the formation of highly reactive surface oxygen species before describing their participation in catalytic reactions and providing mechanistic insights and strategies for designing new (electro catalysts. Finally, we give a brief overview of the different techniques that can be employed to detect the formation of such transient oxygen species.

  13. A quaternary lead based perovskite structured materials with diffuse phase transition behavior

    International Nuclear Information System (INIS)

    Puli, Venkata Sreenivas; Martínez, R.; Kumar, Ashok; Scott, J.F.; Katiyar, Ram S.

    2011-01-01

    Graphical abstract: (a) Curie–Weiss plot for the inverse of the relative dielectric permittivity and (b) log (1/ε − 1/ε m ) as function of log (T − T m ) for ceramics at 1 kHz. Highlights: ► Retaining phase pure structure with quaternary complex stoichiometric compositions. ► P–E loops with good saturation polarization (P s ∼ 30.7 μC/cm 2 ). ► Diffused relaxor phase transition behavior with γ estimated is ∼1.65. -- Abstract: A lead based quaternary compound composed of 0.25(PbZr 0.52 Ti 0.48 O 3 ) + 0.25(PbFe 0.5 Ta 0.5 O 3 ) + 0.25 (PbF 0.67 W 0.33 O 3 ) + 0.25(PbFe 0.5 Nb 0.5 O 3 ) – (PZT–PFT–PFW–PFN) was synthesized by conventional solid-state reaction techniques. It showed moderate high dielectric constant, low dielectric loss, and two diffuse phase transitions, one below the room temperature ∼261 K and other above ∼410 K. X-ray diffraction (XRD) patterns revealed a tetragonal crystal structure at room temperature where as scanning electron micrograph (SEM) indicates inhomogeneous surface with an average grain size of 500 nm–3 μm. Well saturated ferroelectric hysteresis loops with good saturation polarization (spontaneous polarization, P s ∼ 30.68 μC/cm 2 ) were observed. Temperature-dependent ac conductivity displayed low conductivity with kink in spectra near the phase transition. In continuing search for developing new ferroelectric materials, in the present study we report stoichiometric compositions of complex perovskite ceramic materials: (PZT–PFT–PFW–PFN) with diffuse phase transition behavior. The crystal structure, dielectric properties, and ferroelectric properties were characterized by XRD, SEM, dielectric spectroscopy, and polarization. 1/ε versus (T) plots revealed diffuse relaxor phase transition (DPT) behavior. The compositional variation on the phase transition temperature, dielectric constant, and ferroelectric to paraelectric phase transitions are discussed.

  14. A quaternary lead based perovskite structured materials with diffuse phase transition behavior

    Energy Technology Data Exchange (ETDEWEB)

    Puli, Venkata Sreenivas, E-mail: pvsri123@gmail.com [Department of Physics and Institute for Functional Nano Materials, University of Puerto Rico, San Juan, PR 00936 (United States); Martinez, R.; Kumar, Ashok [Department of Physics and Institute for Functional Nano Materials, University of Puerto Rico, San Juan, PR 00936 (United States); Scott, J.F. [Department of Physics and Institute for Functional Nano Materials, University of Puerto Rico, San Juan, PR 00936 (United States); Cavendish Laboratory, Dept. Physics, University of Cambridge, Cambridge CB0 3HE (United Kingdom); Katiyar, Ram S., E-mail: rkatiyar@uprrp.edu [Department of Physics and Institute for Functional Nano Materials, University of Puerto Rico, San Juan, PR 00936 (United States)

    2011-12-15

    Graphical abstract: (a) Curie-Weiss plot for the inverse of the relative dielectric permittivity and (b) log (1/{epsilon} - 1/{epsilon}{sub m}) as function of log (T - T{sub m}) for ceramics at 1 kHz. Highlights: Black-Right-Pointing-Pointer Retaining phase pure structure with quaternary complex stoichiometric compositions. Black-Right-Pointing-Pointer P-E loops with good saturation polarization (P{sub s} {approx} 30.7 {mu}C/cm{sup 2}). Black-Right-Pointing-Pointer Diffused relaxor phase transition behavior with {gamma} estimated is {approx}1.65. -- Abstract: A lead based quaternary compound composed of 0.25(PbZr{sub 0.52}Ti{sub 0.48}O{sub 3}) + 0.25(PbFe{sub 0.5}Ta{sub 0.5}O{sub 3}) + 0.25 (PbF{sub 0.67}W{sub 0.33}O{sub 3}) + 0.25(PbFe{sub 0.5}Nb{sub 0.5}O{sub 3}) - (PZT-PFT-PFW-PFN) was synthesized by conventional solid-state reaction techniques. It showed moderate high dielectric constant, low dielectric loss, and two diffuse phase transitions, one below the room temperature {approx}261 K and other above {approx}410 K. X-ray diffraction (XRD) patterns revealed a tetragonal crystal structure at room temperature where as scanning electron micrograph (SEM) indicates inhomogeneous surface with an average grain size of 500 nm-3 {mu}m. Well saturated ferroelectric hysteresis loops with good saturation polarization (spontaneous polarization, P{sub s} {approx} 30.68 {mu}C/cm{sup 2}) were observed. Temperature-dependent ac conductivity displayed low conductivity with kink in spectra near the phase transition. In continuing search for developing new ferroelectric materials, in the present study we report stoichiometric compositions of complex perovskite ceramic materials: (PZT-PFT-PFW-PFN) with diffuse phase transition behavior. The crystal structure, dielectric properties, and ferroelectric properties were characterized by XRD, SEM, dielectric spectroscopy, and polarization. 1/{epsilon} versus (T) plots revealed diffuse relaxor phase transition (DPT) behavior. The

  15. Ferroelectric mesocrystals of bismuth sodium titanate: formation mechanism, nanostructure, and application to piezoelectric materials.

    Science.gov (United States)

    Hu, Dengwei; Kong, Xingang; Mori, Kotaro; Tanaka, Yasuhiro; Shinagawa, Kazunari; Feng, Qi

    2013-09-16

    Ferroelectric mesocrystals of Bi0.5Na0.5TiO3 (BNT) with [100]-crystal-axis orientation were successfully prepared using a topotactic structural transformation process from a layered titanate H1.07Ti1.73O4·nH2O (HTO). The formation reactions of BNT mesocrystals in HTO-Bi2O3-Na2CO3 and HTO-TiO2-Bi2O3-Na2CO3 reaction systems and their nanostructures were studied by XRD, FE-SEM, TEM, SAED, and EDS, and the reaction mechanisms were given. The BNT mesocrystals are formed by a topotactic structural transformation mechanism in the HTO-Bi2O3-Na2CO3 reaction system and by a combination mechanism of the topotactic structural transformation and epitaxial crystal growth in the HTO-TiO2-Bi2O3-Na2CO3 reaction system, respectively. The BNT mesocrystals prepared by these methods are constructed from [100]-oriented BNT nanocrystals. Furthermore, these reaction systems were successfully applied to the fabrication of [100]-oriented BNT ferroelectric ceramic materials. A BNT ceramic material with a high degree of orientation, high relative density, and small grain size was achieved.

  16. Structural, magnetic, and ferroelectric properties of T-like cobalt-doped BiFeO3 thin films

    Science.gov (United States)

    Young, T.; Sharma, P.; Kim, D. H.; Ha, Thai Duy; Juang, Jenh-Yih; Chu, Y.-H.; Seidel, J.; Nagarajan, V.; Yasui, S.; Itoh, M.; Sando, D.

    2018-02-01

    We present a comprehensive study of the physical properties of epitaxial cobalt-doped BiFeO3 films ˜50 nm thick grown on (001) LaAlO3 substrates. X-ray diffraction and magnetic characterization demonstrate high quality purely tetragonal-like (T') phase films with no parasitic impurities. Remarkably, the step-and-terrace film surface morphology can be fully recovered following a local electric-field-induced rhombohedral-like to T' phase transformation. Local switching spectroscopy experiments confirm the ferroelectric switching to follow previously reported transition pathways. Critically, we show unequivocal evidence for conduction at domain walls between polarization variants in T'-like BFO, making this material system an attractive candidate for domain wall-based nanoelectronics.

  17. Aging and Barkhausen Noise in the Relaxor Ferroelectric SBN:La and PMN/PT

    Science.gov (United States)

    Chao, Lambert K.; Colla, Eugene V.; Weissman, M. B.

    2003-03-01

    Relaxor ferroelectrics form a diverse class of materials which exhibit frequency-dependent freezing into a disordered state. The relation to other cooperative glassy freezing, such as in spin glasses, remain uncertain. Previous aging investigations on several relaxors already indicate diverse behavior (E.V. Colla phet al., Phys. Rev. B 63, 134107 (2001)). We present results on aging behavior on PMN/PT (90/10) and SBN:La. SBN:La, believed to fit a random-field Ising model, exhibits complicated aging behavior with a low-temperature regime lacking the memory effects characteristic of spin-glass-like aging seen in the perovskites PMN and PMN/PT. Further information on the glassy freezing is provided via Barkhausen noise experiments using a balanced capacitance bridge technique capable of measuring random noise despite a large systematic background signal [E.V. Colla phet al., Phys. Rev. Lett. 88 017601 (2002).].

  18. Effect of fabrication conditions on phase formation and properties of epitaxial (PbMg{sub 1/3}Nb{sub 2/3}O{sub 3}){sub 0.67}-(PbTiO{sub 3}){sub 0.33} thin films on (001) SrTiO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Boota, Muhammad [MESA+ Institute for Nanotechnology, Faculty of Science and Technology, University of Twente, P.O. Box 217, 7500AE Enschede (Netherlands); Engineering Department, University of Rome “ROMA TRE”, Via della Vasca Navale 79, 00146 Rome (Italy); Houwman, Evert P., E-mail: e.p.houwman@utwente.nl; Nguyen, Minh D.; Rijnders, Guus [MESA+ Institute for Nanotechnology, Faculty of Science and Technology, University of Twente, P.O. Box 217, 7500AE Enschede (Netherlands); Lanzara, Giulia [Engineering Department, University of Rome “ROMA TRE”, Via della Vasca Navale 79, 00146 Rome (Italy)

    2016-05-15

    The pulsed laser deposition process of 300 nm thick films of Pb(Mg{sub 1/3}Nb{sub 2/3})O{sub 3}){sub 0.67}-(PbTiO{sub 3}){sub 0.33} on (001)-oriented SrTiO{sub 3} was studied by varying deposition pressure, substrate deposition temperature, laser fluence on the target and target-substrate distance. Perovskite phase pure, (001)-oriented, epitaxial smooth films were obtained in a narrow range of deposition parameters. The ferroelectric and dielectric properties of films fabricated within this parameter range still vary significantly. This shows the sensitivity of the system for growth conditions. The best film has a polarization value close to that expected for a (001) poled, stress free single crystal film. All films show deposition conditions dependent variations in the self-bias field. The self-bias is very stable during long cycling for films made at optimum deposition conditions. The piezoelectric coefficients of the films are strongly reduced with respect to bulk single crystal values due to the film clamping. The properties variations are ascribed to changes in the grain boundary properties in which film defects are expected to accumulate. Notably slight off-stoichiometry may cause localized screening charges, affecting specifically the polarization and dielectric constant.

  19. Process for growing a film epitaxially upon a MgO surface

    Science.gov (United States)

    McKee, Rodney Allen; Walker, Frederick Joseph

    1997-01-01

    A process and structure wherein optical quality perovskites, such as BaTiO.sub.3 or SrTiO.sub.3, are grown upon a single crystal MgO substrate involves the epitaxial build up of alternating planes of TiO.sub.2 and metal oxide wherein the first plane grown upon the MgO substrate is a plane of TiO.sub.2. The layering sequence involved in the film build up reduces problems which would otherwise result from the interfacial electrostatics at the first atomic layers, and these oxides can be stabilized as commensurate thin films at a unit cell thickness or grown with high crystal quality to thicknesses of 0.5-0.7 .mu.m for optical device applications.

  20. Resistance switching in epitaxial SrCoO{sub x} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Tambunan, Octolia T.; Parwanta, Kadek J.; Acharya, Susant K.; Lee, Bo Wha; Jung, Chang Uk, E-mail: cu-jung@hufs.ac.kr [Department of Physics, Hankuk University of Foreign Studies, Yongin 449-791 (Korea, Republic of); Kim, Yeon Soo; Park, Bae Ho [Division of Quantum Phases and Devices, Department of Physics, Konkuk University, Seoul 143-791 (Korea, Republic of); Jeong, Huiseong; Park, Ji-Yong [Department of Physics and Division of Energy System Research, Ajou University, Suwon 443-749 (Korea, Republic of); Cho, Myung Rae; Park, Yun Daniel [Department of Physics and Astronomy and Center for Subwavelength Optics, Seoul National University, Seoul 151-747 (Korea, Republic of); Choi, Woo Seok [Department of Physics, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of); Kim, Dong-Wook [Department of Physics, Ewha Womans University, Seoul 120-750 (Korea, Republic of); Jin, Hyunwoo; Lee, Suyoun [Electronic Materials Research Center, Korea Institute of Science and Technology, Seoul 136-791 (Korea, Republic of); Song, Seul Ji; Kang, Sung-Jin; Kim, Miyoung; Hwang, Cheol Seong [Department of Material Science and Engineering, Seoul National University, Seoul 151-747 (Korea, Republic of)

    2014-08-11

    We observed bipolar switching behavior from an epitaxial strontium cobaltite film grown on a SrTiO{sub 3} (001) substrate. The crystal structure of strontium cobaltite has been known to undergo topotactic phase transformation between two distinct phases: insulating brownmillerite (SrCoO{sub 2.5}) and conducting perovskite (SrCoO{sub 3−δ}) depending on the oxygen content. The current–voltage characteristics of the strontium cobaltite film showed that it could have a reversible insulator-to-metal transition triggered by electrical bias voltage. We propose that the resistance switching in the SrCoO{sub x} thin film could be related to the topotactic phase transformation and the peculiar structure of SrCoO{sub 2.5}.

  1. Tuning piezoelectric properties through epitaxy of La2Ti2O7 and related thin films

    Energy Technology Data Exchange (ETDEWEB)

    Kaspar, Tiffany C.; Hong, Seungbum; Bowden, Mark E.; Varga, Tamas; Yan, Pengfei; Wang, Chongmin; Spurgeon, Steven R.; Comes, Ryan B.; Ramuhalli, Pradeep; Henager, Charles H.

    2018-02-14

    Current piezoelectric sensors and actuators are limited to operating temperatures less than ~200°C due to the low Curie temperature of the piezoelectric material. High temperature piezoelectric materials such as La2Ti2O7 (LTO) would facilitate the development of high-temperature sensors if the piezoelectric coupling coefficient could be maximized. We have deposited epitaxial LTO films on SrTiO3(001), SrTiO3(110), and rutile TiO2(110) substrates by pulsed laser deposition, and show that the crystalline orientation of the LTO film, and thus its piezoelectric coupling direction, can be controlled by epitaxial matching to the substrate. The structure and phase purity of the films were investigated by x-ray diffraction and scanning transmission electron microscopy. To characterize the piezoelectric properties, piezoresponse force microscopy was used to measure the in-plane and out-of-plane piezoelectric coupling in the films. We find that the strength of the out-of-plane piezoelectric coupling can be increased when the piezoelectric crystalline direction is rotated partially out-of-plane via epitaxy. The strongest out-of-plane coupling is observed for LTO/STO(001). Deposition on TiO2(110) results in epitaxial La2/3TiO3, an orthorhombic perovskite of interest as a microwave dielectric material. La2/3TiO3 can be difficult to stabilize in bulk form, and epitaxial deposition has not been previously reported. These results confirm that control of the crystalline orientation of LTO-based materials can increase the out-of-plane strength of its piezoelectric coupling, which can be exploited in piezoelectric devices.

  2. Nanosheet controlled epitaxial growth of PbZr0.52Ti0.48O3 thin films on glass substrates

    Science.gov (United States)

    Bayraktar, M.; Chopra, A.; Bijkerk, F.; Rijnders, G.

    2014-09-01

    Integration of PbZr0.52Ti0.48O3 (PZT) films on glass substrates is of high importance for device applications. However, to make use of the superior ferro- and piezoelectric properties of PZT, well-oriented crystalline or epitaxial growth with control of the crystal orientation is a prerequisite. In this article, we report on epitaxial growth of PZT films with (100)- and (110)-orientation achieved by utilizing Ca2Nb3O10 (CNO) and Ti0.87O2 (TO) nanosheets as crystalline buffer layers. Fatigue measurements demonstrated stable ferroelectric properties of these films up to 5 × 109 cycles. (100)-oriented PZT films on CNO nanosheets show a large remnant polarization of 21 μC/cm2 that is the highest remnant polarization value compared to (110)-oriented and polycrystalline films reported in this work. A piezoelectric response of 98 pm/V is observed for (100)-oriented PZT film which is higher than the values reported in the literature on Si substrates.

  3. Influence of epitaxial strain on multiple-mode compounds: The case of SrBi.sub.2./sub.Nb.sub.2./sub.O.sub.9./sub.

    Czech Academy of Sciences Publication Activity Database

    Petralanda, U.; Hlinka, Jiří; Extebarria, I.

    2017-01-01

    Roč. 96, č. 14 (2017), s. 1-7, č. článku 144112. ISSN 2469-9950 R&D Projects: GA ČR GA15-04121S Grant - others:AV ČR(CZ) PAN-17-04 Program:Bilaterální spolupráce Institutional support: RVO:68378271 Keywords : ferroelectrics * thin films * epitaxy * ab-initio methods * phase transitions Subject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.) Impact factor: 3.836, year: 2016

  4. Reversal of the lattice structure in SrCoOx epitaxial thin films studied by real-time optical spectroscopy and first-principles calculations

    OpenAIRE

    Choi, Woo Seok; Jeen, Hyoungjeen; Lee, Jun Hee; Seo, S. S. Ambrose; Cooper, Valentino R.; Rabe, Karin M.; Lee, Ho Nyung

    2013-01-01

    Using real-time spectroscopic ellipsometry, we directly observed a reversible lattice and electronic structure evolution in SrCoOx (x = 2.5 - 3) epitaxial thin films. Drastically different electronic ground states, which are extremely susceptible to the oxygen content x, are found in the two topotactic phases, i.e. the brownmillerite SrCoO2.5 and the perovskite SrCoO3. First principles calculations confirmed substantial differences in the electronic structure, including a metal-insulator tran...

  5. Ferroelectric Electron Emission Principles and Technology

    CERN Document Server

    Riege, H

    1997-01-01

    The spontaneous electrical polarization of ferroelectric materials can be changed either by reversal or by phase transition from a ferroelectric into a non-ferroelectric state or vice versa. If spontaneous polarization changes are induced with fast heat, mechanical pressure, laser or electric field pulses on a submicrosecond time scale, strong uncompensated surface charge densities and related polarization fields are generated, which may lead to the intense self-emission of electrons from the negatively charged free surface areas of the ferroelectric sample. Hence, electron guns can be built with extraction-field-free ferroelectric cathodes, which may be easily separated from the high-field regions of post-accelerating gap structures. The intensity, the energy, the temporal and spatial distribution, and the repetitition rate of the emitted electron beams can be controlled within wide limits via the excitation pulses and external focusing and accelerating electromagnetic fields. The technological advantages an...

  6. Ferroelectricity in undoped hafnium oxide

    International Nuclear Information System (INIS)

    Polakowski, Patrick; Müller, Johannes

    2015-01-01

    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 P r of up to 10 μC cm −2 as well as a read/write endurance of 1.6 × 10 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. The Control of Anisotropic Transport in Manganites by Stripy Domains

    Science.gov (United States)

    Ju, Changcheng; Lu, Xiaomei; Chu, Yinghao

    2014-03-01

    Epitaxial thin film acts as a significant tool to investigate novel phenomena of complex oxide systems. Extrinsic constraint1 of uniform or certain designed buffer layer strain could be easily implanted to these materials. However, the strain distribution might be quite complicated by involving micro- or nano-lattice distortions which could partially relax the strain and determine the complex phase diagrams of thin film, meanwhile introducing structural and physical inhomogeneities. In this work , we report 71° striped ferroelectric domains created in BFO can also epitaxially lock the perovskite manganites leading to the emerge of ordered structural domain. LSMO/BFO hetero-epitaxial samples are deposited by PLD. The 71° periodic striped domains and coherent growth are demonstrated by PFM and X-ray analysis. Plan-view TEM and X-ray RSM have been used to confirm the epitaxial relationships of the functional layers and IP lattice constant. Both the simulation and structural analysis demonstrate we can create a periodic ordered stripe structural domain in LSMO. And this will leave an anisotropic distribution of structural domain walls which makes it possible to capture the anisotropic tunneling for strong electron-lattice coupling in manganites. Temperature-dependent resistivity measurements reveal a substantial anisotropic resistivities and a remarkable shift of the MI transition between the perpendicular and parallel to the stripe domain directions.

  8. Structure-Function Relationships of Ferroelectric Polymers.

    Science.gov (United States)

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

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

  9. Ferroelectric domain engineering by focused infrared femtosecond pulses

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Xin; Shvedov, Vladlen; Sheng, Yan, E-mail: yan.sheng@anu.edu.au [Laser Physics Centre, Research School of Physics and Engineering, Australian National University, Canberra, ACT 0200 (Australia); Karpinski, Pawel [Laser Physics Centre, Research School of Physics and Engineering, Australian National University, Canberra, ACT 0200 (Australia); Wroclaw University of Technology, Wybrzeze Wyspianskiego, Wroclaw (Poland); Koynov, Kaloian [Max-Planck Institute for Polymer Research, Ackermannweg 10, D-55128 Mainz (Germany); Wang, Bingxia; Trull, Jose; Cojocaru, Crina [Departament de Fisica i Enginyeria Nuclear, Universitat Politecnica de Catalunya, Rambla Sant Nebridi, 08222 Terrassa, Barcelona (Spain); Krolikowski, Wieslaw [Laser Physics Centre, Research School of Physics and Engineering, Australian National University, Canberra, ACT 0200 (Australia); Texas A& M University at Qatar, Doha (Qatar)

    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.

  10. Nanoscale organic ferroelectric resistive switches

    NARCIS (Netherlands)

    Khikhlovskyi, V.; Wang, R.; Breemen, A.J.J.M. van; Gelinck, G.H.; Janssen, R.A.J.; Kemerink, M.

    2014-01-01

    Organic ferroelectric resistive switches function by grace of nanoscale phase separation in a blend of a semiconducting and a ferroelectric polymer that is sandwiched between metallic electrodes. In this work, various scanning probe techniques are combined with numerical modeling to unravel their

  11. Enhanced performance of solution-processed broadband photodiodes by epitaxially blending MAPbBr3 quantum dots and ternary PbSxSe1-x quantum dots as the active layer

    Science.gov (United States)

    Sulaman, Muhammad; Yang, Shengyi; Jiang, Yurong; Tang, Yi; Zou, Bingsuo

    2017-12-01

    Organic-inorganic hybrid photodetectors attract more and more interest, since they can combine the advantages of both organic and inorganic materials into one device, and broadband photodetectors are widely used in many scientific and industrial fields. In this work, we demonstrate the enhanced-performance solution-processed broadband photodiodes by epitaxially blending organo-lead halide perovskite (MAPbBr3) colloidal quantum dots (CQDs) with ternary PbSxSe1-x CQDs as the active layer. As a result, the interfacial features of the hetero-epitaxial nanocomposite MAPbBr3:PbSxSe1-x enables the design and perception of functionalities that are not available for the single-phase constituents or layered devices. By combining the high electrical transport properties of MAPbBr3 QDs with the highly radiative efficiency of PbS0.4Se0.6 QDs, the photodiodes ITO/ZnO/PbS0.4Se0.6:MAPbBr3/Au exhibit a maximum photoresponsivity and specific detectivity of 21.48 A W-1 and 3.59 × 1013 Jones, 22.16 A W-1 and 3.70 × 1013 Jones at room temperature under 49.8 μW cm-2 532 nm laser and 62 μW cm-2 980 nm laser, respectively. This is higher than that of the layered photodiodes ITO/ZnO/PbS0.4Se0.6/MAPbBr3/Au, pure perovskite (MAPbBr3) (or PbS0.4Se0.6) QD-based photodiodes reported previously, and it is also better than the traditional inorganic semiconductor-based photodetectors. Our experimental results indicate that epitaxially-aligned nanocomposites (MAPbBr3:PbSxSe1-x) exhibit remarkable optoelectronic properties that are traceable to their atomic-scale crystalline coherence, and one can utilize the excellent photocarrier diffusion from PbSxSe1-x into the perovskite to enhance the device performance from the UV-visible to infrared region.

  12. Morphology modification of perovskite film by a simple post-treatment process in perovskite solar cell

    Energy Technology Data Exchange (ETDEWEB)

    Song, J.; Yang, Y.; Zhao, Y.L., E-mail: sdyulong@cumt.edu.cn; Che, M.; Zhu, L.; Gu, X.Q.; Qiang, Y.H., E-mail: yhqiang@cumt.edu.cn

    2017-03-15

    Highlights: • Perovskite films were post-treated by DMF/CBZ, DMSO/CBZ, or GBL/CBZ blend solvents. • This process could repair pinholes and enhance coverage in perovskite film. • This technique could modify charge transfer process at TiO{sub 2}/perovskite interface. - Abstract: A homogenous perovskite thin film with high coverage is a determining factor for high performance perovskite solar cells. Unlike previous pre-treatments aiming at perovskite precursor, we proposed a simple method to modify the morphology of perovskite films by post-treatment process using mixed solvents of N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), or 1,4-butyrolactone (GBL) with chlorobenzene (CBZ) in this paper. As good solvent of perovskite, DMF, DMSO, and GBL could dissolve the formed perovskite film. Meanwhile, CBZ, anti-solvent of perovskite film, could decrease the dissolving capacity of these good solvents. Therefore, the perovskite film coverage might be improved by the partial dissolution and recrystallization after solvent post-treatment process. Electrochemical impedance spectrometry (EIS) and time-resolved photoluminescence (TRPL) indicated that this post-treatment process could enhance charge transfer at TiO{sub 2}/perovskite interface. Finally, the conversion efficiency increased from 10.10% to 11.82%, 11.68%, and 10.66% using perovskite films post-treated by DMF/CBZ, DMSO/CBZ, and GBL/CBZ blend solvents, respectively.

  13. Hybrid Organic-Inorganic Perovskite Photodetectors.

    Science.gov (United States)

    Tian, Wei; Zhou, Huanping; Li, Liang

    2017-11-01

    Hybrid organic-inorganic perovskite materials garner enormous attention for a wide range of optoelectronic devices. Due to their attractive optical and electrical properties including high optical absorption coefficient, high carrier mobility, and long carrier diffusion length, perovskites have opened up a great opportunity for high performance photodetectors. This review aims to give a comprehensive summary of the significant results on perovskite-based photodetectors, focusing on the relationship among the perovskite structures, device configurations, and photodetecting performances. An introduction of recent progress in various perovskite structure-based photodetectors is provided. The emphasis is placed on the correlation between the perovskite structure and the device performance. Next, recent developments of bandgap-tunable perovskite and hybrid photodetectors built from perovskite heterostructures are highlighted. Then, effective approaches to enhance the stability of perovskite photodetector are presented, followed by the introduction of flexible and self-powered perovskite photodetectors. Finally, a summary of the previous results is given, and the major challenges that need to be addressed in the future are outlined. A comprehensive summary of the research status on perovskite photodetectors is hoped to push forward the development of this field. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Experimental evidence of enhanced ferroelectricity in Ca doped BiFeO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Costa, L.V.; Deus, R.C. [Universidade Estadual Paulista, UNESP, Faculdade de Engenharia de Guaratinguetá, Av. Dr. Ariberto Pereira da Cunha, 333, Bairro Portal das Colinas, CEP 12516-410 Guaratinguetá, SP (Brazil); Foschini, C.R.; Longo, E. [Universidade Estadual Paulista, UNESP, Faculdade de Engenharia de Bauru, Dept. de Eng. Mecânica, Av. Eng. Luiz Edmundo C. Coube 14-01, 17033-360 Bauru, SP (Brazil); Cilense, M. [Universidade Estadual Paulista, UNESP, Instituto de Química – Laboratório Interdisciplinar em Cerâmica (LIEC), Rua Professor Francisco Degni s/n, 14800-90 Araraquara, SP (Brazil); Simões, A.Z., E-mail: alezipo@yahoo.com [Universidade Estadual Paulista, UNESP, Faculdade de Engenharia de Guaratinguetá, Av. Dr. Ariberto Pereira da Cunha, 333, Bairro Portal das Colinas, CEP 12516-410 Guaratinguetá, SP (Brazil)

    2014-04-01

    Calcium (Ca)-doped bismuth ferrite (BiFeO{sub 3}) thin films prepared by using the polymeric precursor method (PPM) were characterized by X-ray diffraction (XRD), field emission gun scanning electron microscopy (FEG-SEM), transmission electron microscopy (TEM), polarization and piezoelectric measurements. Structural studies by XRD and TEM reveal the co-existence of distorted rhombohedral and tetragonal phases in the highest doped BiFeO{sub 3} where enhanced ferroelectric and piezoelectric properties are produced by internal strain. Resistive switching is observed in BFO and Ca-doped BFO which are affected by the barrier contact and work function of multiferroic materials and Pt electrodes. A high coercive field in the hysteresis loop is observed for the BiFeO{sub 3} film. Piezoelectric properties are improved in the highest Ca-doped sample due to changes in the crystal structure of BFO for a primitive cubic perovskite lattice with four-fold symmetry and a large tetragonal distortion within the crystal domain. This observation introduces magnetoelectronics at room temperature by combining electronic conduction with electric and magnetic degrees of freedom which are already present in the multiferroic BiFeO{sub 3}. - Highlights: • Ca doped BiFeO{sub 3} thin films were obtained by the polymeric precursor method. • Co-existence of distorted rhombohedral and tetragonal phases are evident. • Enhanced ferroelectric and piezoelectric properties are produced by the internal strain in the Ca doped BiFeO{sub 3} film.

  15. Crystal structure, dielectric, ferroelectric and energy storage properties of La-doped BaTiO3 semiconducting ceramics

    Directory of Open Access Journals (Sweden)

    Venkata Sreenivas Puli

    2015-09-01

    Full Text Available Polycrystalline La-doped BaTiO3 (Ba(1-xLax\tTiO3 [x=0,0.0005,0.001,0.003] ceramics (denoted as BTO,BLT1,BLT2,BLT3 were synthesized by conventional solid-state reaction method and characterized by X-ray diffraction (XRD, scanning electron microscopy (SEM, and Raman spectroscopy. XRD and Raman spectra revealed single-phase tetragonal perovskite crystalline structure. Well-saturated polarization–electric field (P–E hysteresis loops were observed with the measurement frequency of 50 Hz at room temperature and confirmed ferroelectric nature of these ceramics and a high recoverable electrical energy storage density of 0.350 J/cm3 with energy efficiency (n∼9%, which is useful in energy storage capacitor applications. Dielectric studies revealed anomalies around 415–420 K and near the Curie temperature. The latter is attributed to the ferroelectric to paraelectric phase transition. Better dielectric performances were obtained for La-doped samples sintered at 1350°C for 4 h. Grain growth is inhibited with lanthanum (La incorporation into the BTO lattice. Room temperature semiconducting behavior with positive temperature coefficient of resistivity (PTCR behavior at TC is attributed to electron compensation mechanism.

  16. Photoelectron spectroscopic and microspectroscopic probes of ferroelectrics

    Science.gov (United States)

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

    2017-12-01

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

  17. Flexible graphene–PZT ferroelectric nonvolatile memory

    International Nuclear Information System (INIS)

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

    2013-01-01

    We report the fabrication of a flexible graphene-based nonvolatile memory device using Pb(Zr 0.35 ,Ti 0.65 )O 3 (PZT) as the ferroelectric material. The graphene and PZT ferroelectric layers were deposited using chemical vapor deposition and sol–gel methods, respectively. Such PZT films show a high remnant polarization (P r ) of 30 μC cm −2 and a coercive voltage (V c ) of 3.5 V under a voltage loop over ±11 V. The graphene–PZT ferroelectric nonvolatile memory on a plastic substrate displayed an on/off current ratio of 6.7, a memory window of 6 V and reliable operation. In addition, the device showed one order of magnitude lower operation voltage range than organic-based ferroelectric nonvolatile memory after removing the anti-ferroelectric behavior incorporating an electrolyte solution. The devices showed robust operation in bent states of bending radii up to 9 mm and in cycling tests of 200 times. The devices exhibited remarkable mechanical properties and were readily integrated with plastic substrates for the production of flexible circuits. (paper)

  18. Flexible graphene-PZT ferroelectric nonvolatile memory.

    Science.gov (United States)

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

    2013-11-29

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

  19. Ferroelectric devices using lead zirconate titanate (PZT) nanoparticles.

    Science.gov (United States)

    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 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.

  20. Epitaxial Pb(Zr,Ti)O3 thin films for a MEMS application

    International Nuclear Information System (INIS)

    Nguyen, Minh D; Vu, Hung N; Blank, Dave H A; Rijnders, Guus

    2011-01-01

    This research presents the deposition and device fabrication of epitaxial Pb(Zr,Ti)O 3 (PZT) thin films for applications in microelectromechanical systems (MEMS). A piezoelectric micro-membrane is described as an example. Using the pulsed laser deposition (PLD) technique and the MEMS microfabrication process, the piezo-membranes with diameters ranging from 200 to 500 μm were obtained. The displacement of piezo-membranes increased from 5.1 to 17.5 nm V −1 with a piezoelectric-membrane diameter in the range of 200–500 μm. Furthermore, the effect of PZT film-thickness on the mechanical properties has been investigated. By using the conductive-oxide SrRuO 3 (SRO) layers as the electrodes, the degradation of both ferroelectric and piezoelectric properties is prevented up to 10 10 switching cycles

  1. The Origin of Uni-axial Negative Thermal Expansion in a Layered Perovskite

    Science.gov (United States)

    Ablitt, Chris; Craddock, Sarah; Senn, Mark; Mostofi, Arash; Bristowe, Nicholas

    Using first-principles calculations within the quasi-harmonic approximation (QHA), we explain the origin of experimentally observed uni-axial negative thermal expansion (NTE) in a layered perovskite: the Ruddlesden-Popper (RP) oxide Ca2MnO4, which has anti-ferromagnetic ordering at low temperatures and is closely related to Ca3Mn2O7, which exhibits hybrid improper ferroelectricity and uni-axial NTE in competing phases. Dynamic tilts of MnO6 octahedra, common in many complex oxides, drive the expansion of the a axis and contraction of the c axis of the tetragonal NTE phase. We find that ferroelastic RP phases with a frozen octahedral rotation are unusually compliant to particular combinations of strains along different axes. The atomic mechanism responsible is characteristic of the perovskite/rock-salt interfaces present in the RP structure. We show that the contribution from this anisotropic elasticity must be taken into account in order to accurately predict NTE over the temperature range observed in experiment. A similar compliance to cooperative strains is found in other systems with uni-axial NTE. The development of this mechanistic understanding of NTE in complex oxides may pave the way for designing tunable multifunctional materials. The authors would like to acknowledge support from the EPSRC and the Centre for Doctoral Training in Theory and Simulation of Materials.

  2. Compositional Design of Dielectric, Ferroelectric and Piezoelectric Properties of (K, Na)NbO₃ and (Ba, Na)(Ti, Nb)O₃ Based Ceramics Prepared by Different Sintering Routes.

    Science.gov (United States)

    Eiras, José A; Gerbasi, Rosimeire B Z; Rosso, Jaciele M; Silva, Daniel M; Cótica, Luiz F; Santos, Ivair A; Souza, Camila A; Lente, Manuel H

    2016-03-08

    Lead free piezoelectric materials are being intensively investigated in order to substitute lead based ones, commonly used in many different applications. Among the most promising lead-free materials are those with modified NaNbO₃, such as (K, Na)NbO₃ (KNN) and (Ba, Na)(Ti, Nb)O₃ (BTNN) families. From a ceramic processing point of view, high density single phase KNN and BTNN ceramics are very difficult to sinter due to the volatility of the alkaline elements, the narrow sintering temperature range and the anomalous grain growth. In this work, Spark Plasma Sintering (SPS) and high-energy ball milling (HEBM), following heat treatments (calcining and sintering), in oxidative (O₂) atmosphere have been used to prepare single phase highly densified KNN ("pure" and Cu 2+ or Li 1+ doped), with theoretical densities ρ th > 97% and BTNN ceramics (ρ th - 90%), respectively. Using BTTN ceramics with a P 4 mm perovskite-like structure, we showed that by increasing the NaNbO₃ content, the ferroelectric properties change from having a relaxor effect to an almost "normal" ferroelectric character, while the tetragonality and grain size increase and the shear piezoelectric coefficients ( k 15 , g 15 and d 15 ) improve. For KNN ceramics, the results reveal that the values for remanent polarization as well as for most of the coercive field are quite similar among all compositions. These facts evidenced that Cu 2+ may be incorporated into the A and/or B sites of the perovskite structure, having both hardening and softening effects.

  3. Enhanced dielectric nonlinearity in epitaxial Pb0.92La0.08Zr0.52Ti0.48O3 thin films

    International Nuclear Information System (INIS)

    Ma, Chunrui; Wu, Judy; Ma, Beihai; Mi, Shao-Bo; Liu, Ming

    2014-01-01

    High quality c-axis oriented epitaxial Pb 0.92 La 0.08 Zr 0.52 Ti 0.48 O 3 films were fabricated using pulsed laser deposition on (001) LaAlO 3 substrates with conductive LaNiO 3 buffers. Besides confirmation of the in-plane and out-of-plane orientations using X-ray diffraction, transmission electron microscopy study has revealed columnar structure across the film thickness with column width around 100 nm. Characterization of ferroelectric properties was carried out in comparison with polycrystalline Pb 0.92 La 0.08 Zr 0.52 Ti 0.48 O 3 films to extract the effect of epitaxial growth. It is found that the ratio between the irreversible Rayleigh parameter and reversible parameter increased up to 0.028 cm/kV at 1 kHz on epitaxial samples, which is more than twice of that on their polycrystalline counterparts. While this ratio decreased to 0.022 cm/kV with increasing frequency to100 kHz, a much less frequency dependence was observed as compared to the polycrystalline case. The epitaxial Pb 0.92 La 0.08 Zr 0.52 Ti 0.48 O 3 films exhibited a higher mobility of domain wall and the higher extrinsic contribution to the dielectric properties, as well as reduced density of defects, indicating that it is promising for tunable and low power consumption devices

  4. Pumping requirements and options for molecular beam epitaxy and gas source molecular beam epitaxy/chemical beam epitaxy

    International Nuclear Information System (INIS)

    McCollum, M.J.; Plano, M.A.; Haase, M.A.; Robbins, V.M.; Jackson, S.L.; Cheng, K.Y.; Stillman, G.E.

    1989-01-01

    This paper discusses the use of gas sources in growth by MBE as a result of current interest in growth of InP/InGaAsP/InGaAs lattice matched to InP. For gas flows greater than a few sccm, pumping speed requirements dictate the use of turbomolecular or diffusion pumps. GaAs samples with high p-type mobilities have been grown with diffusion pumped molecular beam epitaxial system. According to the authors, this demonstration of the inherent cleanliness of a properly designed diffusion pumping system indicates that a diffusion pump is an excellent inexpensive and reliable choice for growth by molecular beam epitaxy and gas source molecular beam epitaxy/chemical beam epitaxy

  5. Resonant halide perovskite nanoparticles

    Science.gov (United States)

    Tiguntseva, Ekaterina Y.; Ishteev, Arthur R.; Komissarenko, Filipp E.; Zuev, Dmitry A.; Ushakova, Elena V.; Milichko, Valentin A.; Nesterov-Mueller, Alexander; Makarov, Sergey V.; Zakhidov, Anvar A.

    2017-09-01

    The hybrid halide perovskites is a prospective material for fabrication of cost-effective optical devices. Unique perovskites properties are used for solar cells and different photonic applications. Recently, perovskite-based nanophotonics has emerged. Here, we consider perovskite like a high-refractive index dielectric material, which can be considered to be a basis for nanoparticles fabrication with Mie resonances. As a result, we fabricate and study resonant perovskite nanoparticles with different sizes. We reveal, that spherical nanoparticles show enhanced photoluminescence signal. The achieved results lay a cornerstone in the field of novel types of organic-inorganic nanophotonics devices with optical properties improved by Mie resonances.

  6. Single crystal magnetic, dielectric and thermal studies of the relaxor ferroelectric Pb(Fe2/3W1/3)O3

    International Nuclear Information System (INIS)

    Ye, Z.G.; Sato, M.; Kita, E.; Bursill, L.A.; Schmid, H.

    1998-01-01

    The magnetic, dielectric and thermal properties of the complex perovskite Pb(Fe 2/3 W 1/3 )O 3 [PFW] have been studied on single crystals by means of a SQUID magnetometer, dielectric measurements and thermal analysis. Anomalies in the temperature dependence of the magnetization have revealed magnetic phase transitions at T N1 =350 K and T N2 =20 K. These two steps of antiferromagnetic ordering are attributed to the microstructural feature of the complex perovskite, characterized by ordered and disordered arrangements on the B-site, giving rise to a strong superexchange interaction of - Fe 3 + - O - Fe 3+ - type with a higher ordering temperature, and to a weak superexchange interaction of the B-site ordered elpasolite type - Fe 3+ + - O - W - O - Fe 3+ - with a lower Neel temperature. The low temperature antiferromagnetic phase exhibits a weak ferromagnetism. The dielectric properties of PFW show a relaxor ferroelectric behaviour with a dispersive maximum of permittivity at Tm (170 -190 K). The magnetic phase transition at T N2 =20 K results in anomalies both of the real part of permittivity and the dissipation factor, suggesting a magneto-electric coupling via magneto-structural interactions

  7. Nonequilibrium ferroelectric-ferroelastic 10 nm nanodomains: wrinkles, period-doubling, and power-law relaxation.

    Science.gov (United States)

    Scott, James F; Evans, Donald M; Katiyar, Ram S; McQuaid, Raymond G P; Gregg, J Marty

    2017-08-02

    Since the 1935 work of Landau-Lifshitz and of Kittel in 1946 all ferromagnetic, ferroelectric, and ferroelastic domains have been thought to be straight-sided with domain widths proportional to the square root of the sample thickness. We show in the present work that this is not true. We also discover period doubling domains predicted by Metaxas et al (2008 Phys. Rev. Lett. 99 217208) and modeled by Wang and Zhao (2015 Sci. Rep. 5 8887). We examine non-equilibrium ferroic domain structures in perovskite oxides with respect to folding, wrinkling, and relaxation and suggest that structures are kinetically limited and in the viscous flow regime predicted by Metaxas et al in 2008 but never observed experimentally. Comparisons are made with liquid crystals and hydrodynamic instabilities, including chevrons, and fractional power-law relaxation. As Shin et al (2016 Soft Matter 12 3502) recently emphasized: 'An understanding of how these folds initiate, propagate, and interact with each other is still lacking'. Inside each ferroelastic domain are ferroelectric 90° nano-domains with 10 nm widths and periodicity in agreement with the 10 nm theoretical minima predicted by Feigl et al (2014 Nat. Commun. 5 4677). Evidence is presented for domain-width period doubling, which is common in polymer films but unknown in ferroic domains. A discussion of the folding-to-period doubling phase transition model of Wang and Zhao is included.

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

    Science.gov (United States)

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

    2014-01-01

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

  9. Improper ferroelectrics as high-efficiency energy conversion materials

    International Nuclear Information System (INIS)

    Wakamatsu, Toru; Tanabe, Kenji; Terasaki, Ichiro; Taniguchi, Hiroki

    2017-01-01

    An improper ferroelectric is a certain type of ferroelectrics whose primary order parameter is not polarization but another physical quantity such as magnetization. In contrast to a conventional proper ferroelectrics as represented by Pb(Zr,Ti)O_3 and BaTiO_3, the improper ferroelectrics has been inconceivable for practical applications thus far. Herein, we illustrate the great potential of improper ferroelectrics for efficient conversion of temperature fluctuation to electric energy, as demonstrated with (Ca_0_._8_4Sr_0_._1_6)_8[AlO_2]_1_2(MoO_4)_2 (CSAM-16). The present study has experimentally proven that CSAM-16 achieves an excellent electrothermal coupling factor and high electric field sensitivity for pyroelectric energy conversion that approach a practical level for application to self-powered autonomous electronic devices for rapidly spreading wireless sensor networks. The present results provide a novel approach to developing innovative pyroelectric energy harvesting devices using improper ferroelectrics. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  10. Bulk photovoltaic effect in epitaxial (K, Nb) substituted BiFeO3 thin films

    Science.gov (United States)

    Agarwal, Radhe; Zheng, Fan; Sharma, Yogesh; Hong, Seungbum; Rappe, Andrew; Katiyar, Ram

    We studied the bulk photovoltaic effect in epitaxial (K, Nb) modified BiFeO3 (BKFNO) thin films using theoretical and experimental methods. Epitaxial BKFNO thin films were grown by pulsed laser deposition (PLD). First, we have performed first principles density function theory (DFT) using DFT +U method to calculate electronic band structure, including Hubbard-Ueff (Ueff =U-J) correction into Hamiltonian. The electronic band structure calculations showed a direct band gap at 1.9 eV and a defect level at 1.7 eV (in a 40 atom BKFNO supercell), sufficiently lower in comparison to the experimentally observed values. Furthermore, the piezoforce microscopy (PFM) measurements indicated the presence of striped polydomains in BKFNO thin films. Angle-resolved PFM measurements were also performed to find domain orientation and net polarization directions in these films. The experimental studies of photovoltaic effect in BKNFO films showed a short circuit current of 59 micro amp/cm2 and open circuit voltage of 0.78 V. We compared our experimental results with first principles shift current theory calculations of bulk photovoltaic effect (BPVE).The synergy between theory and experimental results provided a realization of significant role of BPVE in order to understand the photovoltaic mechanism in ferroelectrics.

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

    Science.gov (United States)

    2016-10-14

    strength for non- doped LF4 and LiNbO3/LF4 nanocolloids at temperature 30C. 146 R. K . SHUKLA ET AL. 6 Distribution A. Approved for public release (PA...AFRL-RX-WP-JA-2017-0210 FERROELECTRIC BaTiO3 AND LiNbO3 NANOPARTICLES DISPERSED IN FERROELECTRIC LIQUID CRYSTAL MIXTURES: ELECTROOPTIC...COMMAND UNITED STATES AIR FORCE Ferroelectric BaTiO3 and LiNbO3 nanoparticles dispersed in ferroelectric liquid crystal mixtures: Electrooptic and

  12. Ultrafast Photovoltaic Response in Ferroelectric Nanolayers

    Energy Technology Data Exchange (ETDEWEB)

    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.

  13. Ultrafast Photovoltaic Response in Ferroelectric Nanolayers

    International Nuclear Information System (INIS)

    Daranciang, Dan

    2012-01-01

    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.

  14. Ferroelectric nanostructure having switchable multi-stable vortex states

    Science.gov (United States)

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

    2009-09-22

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

  15. Novel Solvent-free Perovskite Deposition in Fabrication of Normal and Inverted Architectures of Perovskite Solar Cells

    Science.gov (United States)

    Nejand, Bahram Abdollahi; Gharibzadeh, Saba; Ahmadi, Vahid; Shahverdi, H. Reza

    2016-01-01

    We introduced a new approach to deposit perovskite layer with no need for dissolving perovskite precursors. Deposition of Solution-free perovskite (SFP) layer is a key method for deposition of perovskite layer on the hole or electron transport layers that are strongly sensitive to perovskite precursors. Using deposition of SFP layer in the perovskite solar cells would extend possibility of using many electron and hole transport materials in both normal and invert architectures of perovskite solar cells. In the present work, we synthesized crystalline perovskite powder followed by successful deposition on TiO2 and cuprous iodide as the non-sensitve and sensitive charge transport layers to PbI2 and CH3NH3I solution in DMF. The post compressing step enhanced the efficiency of the devices by increasing the interface area between perovskite and charge transport layers. The 9.07% and 7.71% cell efficiencies of the device prepared by SFP layer was achieved in respective normal (using TiO2 as a deposition substrate) and inverted structure (using CuI as deposition substrate) of perovskite solar cell. This method can be efficient in large-scale and low cost fabrication of new generation perovskite solar cells. PMID:27640991

  16. Characterization of bicrystalline epitaxial LaNiO{sub 3} films fabricated on MgO (1 0 0) substrates by pulsed laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Zheng Liang [School of Microelectronics and Solid-State Electronics, University of Electronics Science and Technology of China, Chengdu 610054 (China); Zhu Jun [School of Microelectronics and Solid-State Electronics, University of Electronics Science and Technology of China, Chengdu 610054 (China)]. E-mail: junzhu@uestc.edu.cn; Zhang Ying [School of Microelectronics and Solid-State Electronics, University of Electronics Science and Technology of China, Chengdu 610054 (China); Jiang Shuwen [School of Microelectronics and Solid-State Electronics, University of Electronics Science and Technology of China, Chengdu 610054 (China); Li Yanrong [School of Microelectronics and Solid-State Electronics, University of Electronics Science and Technology of China, Chengdu 610054 (China); Huawei Xian [School of Microelectronics and Solid-State Electronics, University of Electronics Science and Technology of China, Chengdu 610054 (China); Li Jinlong [School of Microelectronics and Solid-State Electronics, University of Electronics Science and Technology of China, Chengdu 610054 (China)

    2006-03-15

    A series of metallic LaNiO{sub 3} (LNO) thin films were deposited on MgO (1 0 0) substrates by pulsed laser deposition (PLD) under the oxygen pressure of 20 Pa at different substrate temperatures from 450 to 750 deg. C. X-ray diffraction (XRD) was used to characterize the crystal structure of LNO films. {theta}-2{theta} scans of XRD indicate that LNO film deposited at a substrate temperature of 700 deg. C has a high orientation of (l l 0). At other substrate temperatures, the LNO films have mixed phases of (l l 0) and (l 0 0). Furthermore, pole figure measurements show that LNO thin films, with the bicrystalline structure, were epitaxially deposited on MgO (1 0 0) substrates in the mode of LNO (1 1 0)//MgO (1 0 0) at 700 deg. C. Reflection high-energy electric diffraction (RHEED) and atomic force microscopy (AFM) were also performed to investigate the microstructure of LNO films with the high (l l 0) orientation. RHEED patterns clearly confirm this epitaxial relationship. An atomically smooth surface of LNO films at 700 deg. C was obtained. In addition, bicrystalline epitaxial LNO films, fabricated at 700 deg. C, present a excellent conductivity with a lower electrical resistivity of 300 {mu} {omega} cm. Thus, the obtained results indicate that bicystalline epitaxial LNO films could serve as a promising candidate of electrode materials for the fabrication of ferroelectric or dielectric films.

  17. Ferroelectric devices, interconnects, and methods of manufacture thereof

    KAUST Repository

    Alshareef, Husam N.; Unnat, Bhansali; Khan, Mohd Adnan; Saleh, Moussa M.; Odeh, Ihab N.

    2013-01-01

    A doped electroconductive organic polymer is used for forming the electrode of a ferroelectric device or an interconnect. An exemplary ferroelectric device is a ferrelectric capacitor comprising: a substrate (101); a first electrode (106) disposed on the substrate; a ferroelectric layer (112) disposed on and in contact with the first electrode; and a second electrode (116) disposed on and in contact with the ferroelectric layer, wherein at least one of the first electrode and the second electrode is an organic electrode comprising a doped electroconductive organic polymer, for example DMSO-doped PEDOT-PSS.

  18. Ferroelectric devices, interconnects, and methods of manufacture thereof

    KAUST Repository

    Alshareef, Husam N.

    2013-12-12

    A doped electroconductive organic polymer is used for forming the electrode of a ferroelectric device or an interconnect. An exemplary ferroelectric device is a ferrelectric capacitor comprising: a substrate (101); a first electrode (106) disposed on the substrate; a ferroelectric layer (112) disposed on and in contact with the first electrode; and a second electrode (116) disposed on and in contact with the ferroelectric layer, wherein at least one of the first electrode and the second electrode is an organic electrode comprising a doped electroconductive organic polymer, for example DMSO-doped PEDOT-PSS.

  19. Hybrid dual gate ferroelectric memory for multilevel information storage

    KAUST Repository

    Khan, Yasser; Caraveo-Frescas, Jesus Alfonso; Alshareef, Husam N.

    2015-01-01

    Here, we report hybrid organic/inorganic ferroelectric memory with multilevel information storage using transparent p-type SnO semiconductor and ferroelectric P(VDF-TrFE) polymer. The dual gate devices include a top ferroelectric field

  20. Compositional Design of Dielectric, Ferroelectric and Piezoelectric Properties of (K, NaNbO3 and (Ba, Na(Ti, NbO3 Based Ceramics Prepared by Different Sintering Routes

    Directory of Open Access Journals (Sweden)

    José A. Eiras

    2016-03-01

    Full Text Available Lead free piezoelectric materials are being intensively investigated in order to substitute lead based ones, commonly used in many different applications. Among the most promising lead-free materials are those with modified NaNbO3, such as (K, NaNbO3 (KNN and (Ba, Na(Ti, NbO3 (BTNN families. From a ceramic processing point of view, high density single phase KNN and BTNN ceramics are very difficult to sinter due to the volatility of the alkaline elements, the narrow sintering temperature range and the anomalous grain growth. In this work, Spark Plasma Sintering (SPS and high-energy ball milling (HEBM, following heat treatments (calcining and sintering, in oxidative (O2 atmosphere have been used to prepare single phase highly densified KNN (“pure” and Cu2+ or Li1+ doped, with theoretical densities ρth > 97% and BTNN ceramics (ρth - 90%, respectively. Using BTTN ceramics with a P4mm perovskite-like structure, we showed that by increasing the NaNbO3 content, the ferroelectric properties change from having a relaxor effect to an almost “normal” ferroelectric character, while the tetragonality and grain size increase and the shear piezoelectric coefficients (k15, g15 and d15 improve. For KNN ceramics, the results reveal that the values for remanent polarization as well as for most of the coercive field are quite similar among all compositions. These facts evidenced that Cu2+ may be incorporated into the A and/or B sites of the perovskite structure, having both hardening and softening effects.

  1. Compositional Design of Dielectric, Ferroelectric and Piezoelectric Properties of (K, Na)NbO3 and (Ba, Na)(Ti, Nb)O3 Based Ceramics Prepared by Different Sintering Routes

    Science.gov (United States)

    Eiras, José A.; Gerbasi, Rosimeire B. Z.; Rosso, Jaciele M.; Silva, Daniel M.; Cótica, Luiz F.; Santos, Ivair A.; Souza, Camila A.; Lente, Manuel H.

    2016-01-01

    Lead free piezoelectric materials are being intensively investigated in order to substitute lead based ones, commonly used in many different applications. Among the most promising lead-free materials are those with modified NaNbO3, such as (K, Na)NbO3 (KNN) and (Ba, Na)(Ti, Nb)O3 (BTNN) families. From a ceramic processing point of view, high density single phase KNN and BTNN ceramics are very difficult to sinter due to the volatility of the alkaline elements, the narrow sintering temperature range and the anomalous grain growth. In this work, Spark Plasma Sintering (SPS) and high-energy ball milling (HEBM), following heat treatments (calcining and sintering), in oxidative (O2) atmosphere have been used to prepare single phase highly densified KNN (“pure” and Cu2+ or Li1+ doped), with theoretical densities ρth > 97% and BTNN ceramics (ρth ~ 90%), respectively. Using BTTN ceramics with a P4mm perovskite-like structure, we showed that by increasing the NaNbO3 content, the ferroelectric properties change from having a relaxor effect to an almost “normal” ferroelectric character, while the tetragonality and grain size increase and the shear piezoelectric coefficients (k15, g15 and d15) improve. For KNN ceramics, the results reveal that the values for remanent polarization as well as for most of the coercive field are quite similar among all compositions. These facts evidenced that Cu2+ may be incorporated into the A and/or B sites of the perovskite structure, having both hardening and softening effects. PMID:28773304

  2. Epitaxial graphene

    Science.gov (United States)

    de Heer, Walt A.; Berger, Claire; Wu, Xiaosong; First, Phillip N.; Conrad, Edward H.; Li, Xuebin; Li, Tianbo; Sprinkle, Michael; Hass, Joanna; Sadowski, Marcin L.; Potemski, Marek; Martinez, Gérard

    2007-07-01

    Graphene multilayers are grown epitaxially on single crystal silicon carbide. This system is composed of several graphene layers of which the first layer is electron doped due to the built-in electric field and the other layers are essentially undoped. Unlike graphite the charge carriers show Dirac particle properties (i.e. an anomalous Berry's phase, weak anti-localization and square root field dependence of the Landau level energies). Epitaxial graphene shows quasi-ballistic transport and long coherence lengths; properties that may persist above cryogenic temperatures. Paradoxically, in contrast to exfoliated graphene, the quantum Hall effect is not observed in high-mobility epitaxial graphene. It appears that the effect is suppressed due to the absence of localized states in the bulk of the material. Epitaxial graphene can be patterned using standard lithography methods and characterized using a wide array of techniques. These favorable features indicate that interconnected room temperature ballistic devices may be feasible for low-dissipation high-speed nanoelectronics.

  3. Optical, ferroelectric and magnetic properties of multiferroelectric BiFeO3-(K0.5Na0.5)0.4(Sr 0.6Ba0.4)0.8Nb2O6 thin films

    KAUST Repository

    Yao, Yingbang

    2014-02-01

    Multiferroic BiFeO3-(K0.5Na0.5) 0.4(Sr0.6Ba0.4)0.8Nb 2O6 (BFO-KNSBN) trilayer thin films, were epitaxially grown on MgO(0 0 1) and SrTiO3(0 0 1) by using pulsed laser deposition (PLD). Their ferroelectric, magnetic, dielectric and optical properties were investigated. It was found that both ferroelectric polarization and dielectric constant of the films were enhanced by introducing KNSBN as a barrier layer. Meanwhile, ferromagnetism of BFO was maintained. More interestingly, a double hysteresis magnetic loop was observed in the KNSBN-BFO-KNSBN trilayer films, where exchange bias and secondary phase in the BFO layer played crucial roles. Interactions between adjacent layers were revealed by temperature-dependent Raman spectroscopic measurements. © 2013 Elsevier B.V. All rights reserved.

  4. Improper ferroelectrics as high-efficiency energy conversion materials

    Energy Technology Data Exchange (ETDEWEB)

    Wakamatsu, Toru; Tanabe, Kenji; Terasaki, Ichiro; Taniguchi, Hiroki [Department of Physics, Nagoya University, Nagoya 464-8602 (Japan)

    2017-05-15

    An improper ferroelectric is a certain type of ferroelectrics whose primary order parameter is not polarization but another physical quantity such as magnetization. In contrast to a conventional proper ferroelectrics as represented by Pb(Zr,Ti)O{sub 3} and BaTiO{sub 3}, the improper ferroelectrics has been inconceivable for practical applications thus far. Herein, we illustrate the great potential of improper ferroelectrics for efficient conversion of temperature fluctuation to electric energy, as demonstrated with (Ca{sub 0.84}Sr{sub 0.16}){sub 8}[AlO{sub 2}]{sub 12}(MoO{sub 4}){sub 2} (CSAM-16). The present study has experimentally proven that CSAM-16 achieves an excellent electrothermal coupling factor and high electric field sensitivity for pyroelectric energy conversion that approach a practical level for application to self-powered autonomous electronic devices for rapidly spreading wireless sensor networks. The present results provide a novel approach to developing innovative pyroelectric energy harvesting devices using improper ferroelectrics. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  5. Down-conversion luminescence and its temperature-sensing properties from Er3+-doped sodium bismuth titanate ferroelectric thin films

    Science.gov (United States)

    Wang, Shanshan; Zheng, Shanshan; Zhou, Hong; Pan, Anlian; Wu, Guangheng; Liu, Jun-ming

    2015-11-01

    Here, we demonstrate outstanding temperature-sensing properties from Na0.5Bi0.49Er0.01TiO3 (NBT:Er) thin films. The perovskite phase for them is stable in the temperature range from 80 to 440 K. Interestingly, the Er doping enhances the ferroelectric polarization and introduces local dipolar, which are positive for temperature sensing. Pumped by a 488-nm laser, the NBT:Er thin films show strong green luminescence with two bands around 525 and 548 nm. The intensity ratio I 525/ I 548 can be used for temperature sensing, and the maximum sensitivity is about 2.3 × 10-3 K-1, higher than that from Er-doped silicon oxide. These suggest NBT:Er thin film is a promising candidate for temperature sensor.

  6. Organic non-volatile memories from ferroelectric phase-separated blends

    Science.gov (United States)

    Asadi, Kamal; de Leeuw, Dago M.; de Boer, Bert; Blom, Paul W. M.

    2008-07-01

    New non-volatile memories are being investigated to keep up with the organic-electronics road map. Ferroelectric polarization is an attractive physical property as the mechanism for non-volatile switching, because the two polarizations can be used as two binary levels. However, in ferroelectric capacitors the read-out of the polarization charge is destructive. The functionality of the targeted memory should be based on resistive switching. In inorganic ferroelectrics conductivity and ferroelectricity cannot be tuned independently. The challenge is to develop a storage medium in which the favourable properties of ferroelectrics such as bistability and non-volatility can be combined with the beneficial properties provided by semiconductors such as conductivity and rectification. Here we present an integrated solution by blending semiconducting and ferroelectric polymers into phase-separated networks. The polarization field of the ferroelectric modulates the injection barrier at the semiconductor-metal contact. The combination of ferroelectric bistability with (semi)conductivity and rectification allows for solution-processed non-volatile memory arrays with a simple cross-bar architecture that can be read out non-destructively. The concept of an electrically tunable injection barrier as presented here is general and can be applied to other electronic devices such as light-emitting diodes with an integrated on/off switch.

  7. Effect of crystal orientation on the phase diagrams, dielectric and piezoelectric properties of epitaxial BaTiO3 thin films

    Directory of Open Access Journals (Sweden)

    Huaping Wu

    2016-01-01

    Full Text Available The influence of crystal orientations on the phase diagrams, dielectric and piezoelectric properties of epitaxial BaTiO3 thin films has been investigated using an expanded nonlinear thermodynamic theory. The calculations reveal that crystal orientation has significant influence on the phase stability and phase transitions in the misfit strain-temperature phase diagrams. In particular, the (110 orientation leads to a lower symmetry and more complicated phase transition than the (111 orientation in BaTiO3 films. The increase of compressive strain will dramatically enhance the Curie temperature TC of (110-oriented BaTiO3 films, which matches well with previous experimental data. The polarization components experience a great change across the boundaries of different phases at room temperature in both (110- and (111-oriented films, which leads to the huge dielectric and piezoelectric responses. A good agreement is found between the present thermodynamics calculation and previous first-principles calculations. Our work provides an insight into how to use crystal orientation, epitaxial strain and temperature to tune the structure and properties of ferroelectrics.

  8. High-pressure stability relations, crystal structures, and physical properties of perovskite and post-perovskite of NaNiF3

    International Nuclear Information System (INIS)

    Shirako, Y.; Shi, Y.G.; Aimi, A.; Mori, D.; Kojitani, H.; Yamaura, K.; Inaguma, Y.; Akaogi, M.

    2012-01-01

    NaNiF 3 perovskite was found to transform to post-perovskite at 16–18 GPa and 1273–1473 K. The equilibrium transition boundary is expressed as P (GPa)=−2.0+0.014×T (K). Structure refinements indicated that NaNiF 3 perovskite and post-perovskite have almost regular NiF 6 octahedra consistent with absence of the first-order Jahn–Teller active ions. Both NaNiF 3 perovskite and post-perovskite are insulators. The perovskite underwent a canted antiferromagnetic transition at 156 K, and the post-perovskite antiferromagnetic transition at 22 K. Magnetic exchange interaction of NaNiF 3 post-perovskite is smaller than that of perovskite, reflecting larger distortion of Ni–F–Ni network and lower dimension of octahedral arrangement in post-perovskite than those in perovskite. - Graphical abstract: Perovskite–post-perovskite transition in NaNiF 3 at high pressure Highlights: ► NaNiF 3 perovskite (Pv) transforms to post-perovskite (pPv) at 16 GPa and 1300 K. ► The equilibrium transition boundary is expressed as P (GPa)=−2.0+0.014 T (K). ► Antiferromagnetic transition occurs at 156 K in Pv and 22 K in pPv.

  9. Highly Efficient Perovskite-Perovskite Tandem Solar Cells Reaching 80% of the Theoretical Limit in Photovoltage.

    Science.gov (United States)

    Rajagopal, Adharsh; Yang, Zhibin; Jo, Sae Byeok; Braly, Ian L; Liang, Po-Wei; Hillhouse, Hugh W; Jen, Alex K-Y

    2017-09-01

    Organic-inorganic hybrid perovskite multijunction solar cells have immense potential to realize power conversion efficiencies (PCEs) beyond the Shockley-Queisser limit of single-junction solar cells; however, they are limited by large nonideal photovoltage loss (V oc,loss ) in small- and large-bandgap subcells. Here, an integrated approach is utilized to improve the V oc of subcells with optimized bandgaps and fabricate perovskite-perovskite tandem solar cells with small V oc,loss . A fullerene variant, Indene-C 60 bis-adduct, is used to achieve optimized interfacial contact in a small-bandgap (≈1.2 eV) subcell, which facilitates higher quasi-Fermi level splitting, reduces nonradiative recombination, alleviates hysteresis instabilities, and improves V oc to 0.84 V. Compositional engineering of large-bandgap (≈1.8 eV) perovskite is employed to realize a subcell with a transparent top electrode and photostabilized V oc of 1.22 V. The resultant monolithic perovskite-perovskite tandem solar cell shows a high V oc of 1.98 V (approaching 80% of the theoretical limit) and a stabilized PCE of 18.5%. The significantly minimized nonideal V oc,loss is better than state-of-the-art silicon-perovskite tandem solar cells, which highlights the prospects of using perovskite-perovskite tandems for solar-energy generation. It also unlocks opportunities for solar water splitting using hybrid perovskites with solar-to-hydrogen efficiencies beyond 15%. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Enhanced thermoelectric figure-of-merit in environmentally benign BaxSr2-xTiCoO6 double perovskites

    Science.gov (United States)

    Saxena, Mandvi; Roy, Pinku; Acharya, Megha; Bose, Imon; Tanwar, Khagesh; Maiti, Tanmoy

    2016-12-01

    Environmental friendly, non-toxic double perovskite BaxSr2-xTiCoO6 compositions with 0 ≤ x ≤ 0.2 were synthesized using solid-state reaction route for high temperature thermoelectric (TE) applications. XRD and SEM studies confirmed the presence of single-phase solid solution with highly dense microstructure for all the oxide compositions. Temperature dependent electrical conductivity measurement showed semiconductor to metal (M-S) transition in these double perovskites. Incorporation of barium in Sr2TiCoO6 pushed M-S transition to higher temperature making it a potential candidate for high temperature TE applications. Conductivity behaviors of these oxides were explained by small polaron model. Furthermore, these oxides exhibit a glass like behavior resulting in low thermal conductivity. Low temperature dielectric measurement revealed relaxor ferroelectric behavior in these oxides below room temperature. Transition of these relaxors into a glassy state beyond Burns temperature (TD) was found responsible for having low thermal conductivity in these oxides. Maximum dimensionless TE figure-of-merit ZT = 0.29 at 1223 K was achieved for BaxSr2-xTiCoO6 composition with x = 0.2.

  11. Epitaxial growth and multiferroic properties of cation-engineered (Bi{sub 0.45}La{sub 0.05}Ba{sub 0.5})(Fe{sub 0.75}Nb{sub 0.25})O{sub 3} thin film on Ir-buffered (0 0 1) MgO substrate

    Energy Technology Data Exchange (ETDEWEB)

    Paik, Hanjong [Department of Materials Science and Engineering, Cornell University, Ithaca NY 14853 (United States); Kim, Hyun-Suk [Department of Materials Engineering, Chungnam University, Daejeon 305-764 (Korea, Republic of); Hong, Jongin, E-mail: hongj@cau.ac.kr [Department of Chemistry, Chung-Ang University, 84 Heukseok-ro, Dongjak-gu, Seoul 156-756 (Korea, Republic of)

    2015-04-15

    Highlights: • Epitaxial (Bi{sub 0.45}La{sub 0.05}Ba{sub 0.5})(Fe{sub 0.75}Nb{sub 0.25})O{sub 3} thin film was grown on the Ir-buffered (0 0 1) MgO substrate by pulsed laser deposition. • Its ferroelectric polarization switching was investigated by piezoresponse force microscopy. • Its ferromagnetic hysteresis at room temperature and ferrimagnetic–ferromagnetic transition at low temperature were evaluated. • Artificial A- and B-site cation engineering would result in stable multiferroic properties at room temperature. - Abstract: An epitaxial (Bi{sub 0.45}La{sub 0.05}Ba{sub 0.5})(Fe{sub 0.75}Nb{sub 0.25})O{sub 3} (BLB-FNO) thin film was successfully grown on an Ir-buffered (0 0 1) MgO substrate by pulsed laser deposition (PLD). The “cube-on-cube” epitaxial relation, (0 0 1)[1 0 0] BLB-FNO//(0 0 1)[1 0 0] Ir//(0 0 1)[1 0 0] MgO, was confirmed by X-ray diffraction (XRD) pole figures and cross-sectional high-resolution transmission electron microscopy (HRTEM). The ferroelectric polarization switching of the BLB-FNO thin film was investigated by piezoresponse force microscopy (PFM). Its magnetic properties, such as ferromagnetic hysteresis at room temperature and possible magnetic transition at low temperature, were also evaluated. Accordingly, we successfully demonstrated that artificial A- and B-site cation engineering would allow for stable multiferroic properties at room temperature.

  12. Epitaxy physical principles and technical implementation

    CERN Document Server

    Herman, Marian A; Sitter, Helmut

    2004-01-01

    Epitaxy provides readers with a comprehensive treatment of the modern models and modifications of epitaxy, together with the relevant experimental and technological framework. This advanced textbook describes all important aspects of the epitaxial growth processes of solid films on crystalline substrates, including a section on heteroepitaxy. It covers and discusses in details the most important epitaxial growth techniques, which are currently widely used in basic research as well as in manufacturing processes of devices, namely solid-phase epitaxy, liquid-phase epitaxy, vapor-phase epitaxy, including metal-organic vapor-phase epitaxy and molecular-beam epitaxy. Epitaxy’s coverage of science and texhnology thin-film is intended to fill the need for a comprehensive reference and text examining the variety of problems related to the physical foundations and technical implementation of epitaxial crystallization. It is intended for undergraduate students, PhD students, research scientists, lecturers and practic...

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

    NARCIS (Netherlands)

    Cai, R.; Kassa, H.G.; Haouari, R.; Marrani, A.; Geerts, Y.H.; Ruzié, C.; Breemen, A.J.J.M. van; Gelinck, G.H.; Nysten, B.; Hu, Z.; Jonas, A.M.

    2016-01-01

    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

  14. Shell model for BaTiO3-Bi(Zn1/2Ti1/2)O3 perovskite solid solutions

    Science.gov (United States)

    Vielma, J.; Jackson, D.; Roundy, D.; Schneider, G.

    2010-03-01

    Even though the composition of BaTiO3-Bi(Zn1/2Ti1/2)O3 perovskite solid solutions is similar to other ferroelectric compounds, the dielectric response is unusual. Results of permittivity measurements as a function of temperature show a diffuse phase transition indicative of a weakly coupled relaxor behavior.footnotetextC. C. Huang and D. P. Cann, J. Appl. Phys. 104, 024117 (2008) To investigate the weakly coupled relaxor behavior in these materials at intermediate length scales we are developing a newly calibrated shell model based on first-principles supercell calculations of both the solid solution and its compositional endpoints. Initial results for its phase diagram will presented.

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

    Energy Technology Data Exchange (ETDEWEB)

    Li, Fei; Zhang, Shujun; Yang, Tiannan; Xu, Zhuo; Zhang, Nan; Liu, Gang; Wang, Jianjun; Wang, Jianli; Cheng, Zhenxiang; Ye, Zuo-Guang; Luo, Jun; Shrout, Thomas R.; Chen, Long-Qing (Penn); (Xian Jiaotong); (CIW); (Simon); (TRS Techn); (Wollongong)

    2016-12-19

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

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

    Science.gov (United States)

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

    2016-12-19

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

  17. Chemical segregation and self polarisation in ferroelectrics

    Directory of Open Access Journals (Sweden)

    Bernard E. Watts

    2009-06-01

    Full Text Available Chemical partitioning or segregation is commonly encountered in solid-state syntheses. It is driven by compositional, thermal and electric field gradients. These phenomena can be quite extreme in thin films and lead to notable effects on the electrical properties of ferroelectrics. The segregation in ferroelectric thin films will be illustrated and the mechanisms explained in terms of diffusion processes driven by a potential gradient of the oxygen. The hypothesis can also explain self polarisation and imprint in ferroelectric hysteresis.

  18. A comparative study of the Aurivillius phase ferroelectrics CaBi 4Ti 4O 15 and BaBi 4Ti 4O 15

    Science.gov (United States)

    Tellier, J.; Boullay, Ph.; Manier, M.; Mercurio, D.

    2004-06-01

    The room temperature structures of the four-layer Aurivillius phase ferroelectrics CaBi 4Ti 4O 15 and BaBi 4Ti 4O 15 are determined by means of single crystal X-ray diffraction. Regarding the CaBi 4Ti 4O 15 phase, in agreement with the tolerance factor, a significant deformation of the perovskite blocks is observed. The rotation system of the octahedra is typical from even layer Aurivillius phases and leads to the use of the space group A2 1am. For the BaBi 4Ti 4O 15 phase, only a weak variation with respect to the F2 mm space group can be suggested from single crystal X-ray diffraction. A significant presence of Ba atoms in the [ M2O 2] slabs is confirmed in agreement with the previous works but specific Ba 2+ and Bi 3+ sites have to be considered due to the large difference in bounding requirement of these cations. Possible origins for the ferroelectric relaxor behavior of the Ba-based compound are discussed in view of the presented structural analyses.

  19. Influence of microstructure on electromechanical properties of nano-crystalline La-Pb(Ni{sub 1/3}Sb{sub 2/3})-PbZrTiO{sub 3} ferroelectric ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, H.H.; Lonkar, C.M. [Armament Research and Development Establishment, Pune (India); Balasubramanian, K. [Defence Institute of Advanced Technology (Deemed University), Pune (India)

    2017-10-15

    A ferroelectric ceramic composition, Pb{sub 0.98}La{sub 0.02}(Ni{sub 1/3}Sb{sub 2/3}){sub 0.05}[(Zr{sub 0.52}Ti{sub 0.48}){sub 0.995}] {sub 0.95}O{sub 3}, has been synthesized by columbite precursor method followed by mechanical activation for 10 h (MA-10) using high-energy ball mill. Formation of desired perovskite phase during activation was confirmed from analysis of X-ray diffraction patterns, while powder particle size, in nano-meter range, was revealed from high-resolution transmission electron microscopic (HRTEM) investigations. Samples were sintered between 1170 and 1320 C, and were investigated for microstructure and its influence on electromechanical properties. Increment in grain size with sintering temperature was noticed. 1220 C sintering temperature posed denser and uniform microstructure amongst all the temperatures and also showed composition close to morphotropic phase boundary (MPB) of PZT with optimum tetragonality which resulted in better electromechanical properties, suggesting the suitability of this composition for power harvesting applications. Phase transition studies revealed normal ferroelectric behaviour with transition temperature of 286 C. (orig.)

  20. Effect of crystal orientation on the phase diagrams, dielectric and piezoelectric properties of epitaxial BaTiO{sub 3} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Huaping, E-mail: wuhuaping@gmail.com, E-mail: hpwu@zjut.edu.cn [Key Laboratory of E& M (Zhejiang University of Technology), Ministry of Education & Zhejiang Province, Hangzhou 310014 (China); State Key Laboratory of Structural Analysis for Industrial Equipment, Dalian University of Technology, Dalian 116024 (China); Ma, Xuefu; Zhang, Zheng; Zeng, Jun; Chai, Guozhong [Key Laboratory of E& M (Zhejiang University of Technology), Ministry of Education & Zhejiang Province, Hangzhou 310014 (China); Wang, Jie [Department of Engineering Mechanics, School of Aeronautics and Astronautics, Zhejiang University, Hangzhou 310027 (China)

    2016-01-15

    The influence of crystal orientations on the phase diagrams, dielectric and piezoelectric properties of epitaxial BaTiO{sub 3} thin films has been investigated using an expanded nonlinear thermodynamic theory. The calculations reveal that crystal orientation has significant influence on the phase stability and phase transitions in the misfit strain-temperature phase diagrams. In particular, the (110) orientation leads to a lower symmetry and more complicated phase transition than the (111) orientation in BaTiO{sub 3} films. The increase of compressive strain will dramatically enhance the Curie temperature T{sub C} of (110)-oriented BaTiO{sub 3} films, which matches well with previous experimental data. The polarization components experience a great change across the boundaries of different phases at room temperature in both (110)- and (111)-oriented films, which leads to the huge dielectric and piezoelectric responses. A good agreement is found between the present thermodynamics calculation and previous first-principles calculations. Our work provides an insight into how to use crystal orientation, epitaxial strain and temperature to tune the structure and properties of ferroelectrics.

  1. Structural and dielectric properties of (001) and (111)-oriented BaZr0.2Ti0.8O3 epitaxial thin films

    International Nuclear Information System (INIS)

    Ventura, J.; Fina, I.; Ferrater, C.; Langenberg, E.; Coy, L.E.; Polo, M.C.; Garcia-Cuenca, M.V.; Fabrega, L.; Varela, M.

    2010-01-01

    We have grown and characterized BaZr 0.2 Ti 0.8 O 3 (BZT) epitaxial thin films deposited on (001) and (111)-oriented SrRuO 3 -buffered SrTiO 3 substrates by pulsed laser deposition. Structural and morphological characterizations were performed using X-ray diffractometry and atomic force microscopy, respectively. A cube-on-cube epitaxial relationship was ascertained from the θ-2θ and φ diffractograms in both (001) and (111)-oriented films. The (001)-oriented films showed a smooth granular morphology, whereas the faceted pyramid-like crystallites of the (111)-oriented films led to a rough surface. The dielectric response of BZT at room temperature was measured along the growth direction. The films were found to be ferroelectric, although a well-saturated hysteresis loop was obtained only for the (001)-oriented films. High leakage currents were observed for the (111) orientation, likely associated to charge transport along the boundaries of its crystallites. The remanent polarization, coercive field, dielectric constant, and relative change of dielectric permittivity (tunability) of (111)-oriented BZT were higher than those of (001)-oriented BZT.

  2. Planar structured perovskite solar cells by hybrid physical chemical vapor deposition with optimized perovskite film thickness

    Science.gov (United States)

    Wei, Xiangyang; Peng, Yanke; Jing, Gaoshan; Cui, Tianhong

    2018-05-01

    The thickness of perovskite absorber layer is a critical parameter to determine a planar structured perovskite solar cell’s performance. By modifying the spin coating speed and PbI2/N,N-dimethylformamide (DMF) solution concentration, the thickness of perovskite absorber layer was optimized to obtain high-performance solar cells. Using a PbI2/DMF solution of 1.3 mol/L, maximum power conversion efficiency (PCE) of a perovskite solar cell is 15.5% with a perovskite film of 413 nm at 5000 rpm, and PCE of 14.3% was also obtained for a solar cell with a perovskite film of 182 nm thick. It is derived that higher concentration of PbI2/DMF will result in better perovskite solar cells. Additionally, these perovskite solar cells are highly uniform. In 14 sets of solar cells, standard deviations of 11 sets of solar cells were less than 0.50% and the smallest standard deviation was 0.25%, which demonstrates the reliability and effectiveness of hybrid physical chemical vapor deposition (HPCVD) method.

  3. Impact induced depolarization of ferroelectric materials

    Science.gov (United States)

    Agrawal, Vinamra; Bhattacharya, Kaushik

    2018-06-01

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

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

    International Nuclear Information System (INIS)

    Qiu, Xunlin

    2010-01-01

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

  5. Goldstone-like phonon modes in a (111)-strained perovskite

    Science.gov (United States)

    Marthinsen, A.; Griffin, S. M.; Moreau, M.; Grande, T.; Tybell, T.; Selbach, S. M.

    2018-01-01

    Goldstone modes are massless particles resulting from spontaneous symmetry breaking. Although such modes are found in elementary particle physics as well as in condensed-matter systems like superfluid helium, superconductors, and magnons, structural Goldstone modes are rare. Epitaxial strain in thin films can induce structures and properties not accessible in bulk and has been intensively studied for (001)-oriented perovskite oxides. Here we predict Goldstone-like phonon modes in (111)-strained SrMn O3 by first-principles calculations. Under compressive strain the coupling between two in-plane rotational instabilities gives rise to a Mexican hat-shaped energy surface characteristic of a Goldstone mode. Conversely, large tensile strain induces in-plane polar instabilities with no directional preference, giving rise to a continuous polar ground state. Such phonon modes with U (1) symmetry could emulate structural condensed-matter Higgs modes. The mass of this Higgs boson, given by the shape of the Mexican hat energy surface, can be tuned by strain through proper choice of substrate.

  6. Enhanced planar perovskite solar cell efficiency and stability using a perovskite/PCBM heterojunction formed in one step.

    Science.gov (United States)

    Zhou, Long; Chang, Jingjing; Liu, Ziye; Sun, Xu; Lin, Zhenhua; Chen, Dazheng; Zhang, Chunfu; Zhang, Jincheng; Hao, Yue

    2018-02-08

    Perovskite/PCBM heterojunctions are efficient for fabricating perovskite solar cells with high performance and long-term stability. In this study, an efficient perovskite/PCBM heterojunction was formed via conventional sequential deposition and one-step formation processes. Compared with conventional deposition, the one-step process was more facile, and produced a perovskite thin film of substantially improved quality due to fullerene passivation. Moreover, the resulting perovskite/PCBM heterojunction exhibited more efficient carrier transfer and extraction, and reduced carrier recombination. The perovskite solar cell device based on one-step perovskite/PCBM heterojunction formation exhibited a higher maximum PCE of 17.8% compared with that from the conventional method (13.7%). The device also showed exceptional stability, retaining 83% of initial PCE after 60 days of storage under ambient conditions.

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

    Science.gov (United States)

    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.

  8. Doping site dependent thermoelectric properties of epitaxial strontium titanate thin films

    KAUST Repository

    Abutaha, Anas I.; Sarath Kumar, S. R.; Mehdizadeh Dehkordi, Arash; Tritt, Terry M.; Alshareef, Husam N.

    2014-01-01

    We demonstrate that the thermoelectric properties of epitaxial strontium titanate (STO) thin films can be improved by additional B-site doping of A-site doped ABO3 type perovskite STO. The additional B-site doping of A-site doped STO results in increased electrical conductivity, but at the expense of Seebeck coefficient. However, doping on both sites of the STO lattice significantly reduces the lattice thermal conductivity of STO by adding more densely and strategically distributed phononic scattering centers that attack wider phonon spectra. The additional B-site doping limits the trade-off relationship between the electrical conductivity and total thermal conductivity of A-site doped STO, leading to an improvement in the room-temperature thermoelectric figure of merit, ZT. The 5% Pr3+ and 20% Nb5+ double-doped STO film exhibits the best ZT of 0.016 at room temperature. This journal is

  9. Spin Filtering in Epitaxial Spinel Films with Nanoscale Phase Separation

    KAUST Repository

    Li, Peng

    2017-05-08

    The coexistence of ferromagnetic metallic phase and antiferromagnetic insulating phase in nanoscaled inhomogeneous perovskite oxides accounts for the colossal magnetoresistance. Although the model of spin-polarized electron transport across antiphase boundaries has been commonly employed to account for large magnetoresistance (MR) in ferrites, the magnetic anomalies, the two magnetic phases and enhanced molecular moment, are still unresolved. We observed a sizable MR in epitaxial spinel films (NiCo2O4-δ) that is much larger than that commonly observed in spinel ferrites. Detailed analysis reveals that this MR can be attributed to phase separation, in which the perfect ferrimagnetic metallic phase and ferrimagnetic insulating phase coexist. The magnetic insulating phase plays an important role in spin filtering in these phase separated spinel oxides, leading to a sizable MR effect. A spin filtering model based on Zeeman effect and direct tunneling is developed to account for MR of the phase separated films.

  10. Improved photovoltaic performance from inorganic perovskite oxide thin films with mixed crystal phases

    Science.gov (United States)

    Chakrabartty, Joyprokash; Harnagea, Catalin; Celikin, Mert; Rosei, Federico; Nechache, Riad

    2018-05-01

    Inorganic ferroelectric perovskites are attracting attention for the realization of highly stable photovoltaic cells with large open-circuit voltages. However, the power conversion efficiencies of devices have been limited so far. Here, we report a power conversion efficiency of 4.20% under 1 sun illumination from Bi-Mn-O composite thin films with mixed BiMnO3 and BiMn2O5 crystal phases. We show that the photocurrent density and photovoltage mainly develop across grain boundaries and interfaces rather than within the grains. We also experimentally demonstrate that the open-circuit voltage and short-circuit photocurrent measured in the films are tunable by varying the electrical resistance of the device, which in turn is controlled by externally applying voltage pulses. The exploitation of multifunctional properties of composite oxides provides an alternative route towards achieving highly stable, high-efficiency photovoltaic solar energy conversion.

  11. Subcritical switching dynamics and humidity effects in nanoscale studies of domain growth in ferroelectric thin films

    International Nuclear Information System (INIS)

    Blaser, Cédric; Paruch, Patrycja

    2015-01-01

    Ferroelectric domain switching in c-axis-oriented epitaxial Pb(Zr 0.2 Ti 0.8 )O 3 thin films was studied using biased scanning probe microscopy tips. While linear and logarithmic dependence of domain size on tip bias and writing time, respectively, are well known, we report an additional linear dependence on relative humidity in the 28–65% range. We map out the switched domain size as a function of both the tip bias and the applied pulse time and describe a growth-limited regime for very short pulses and a nucleation-limited regime for very low tip bias. Using ‘interrupted-switching’ measurements, we probe the nucleation regime with subcritical pulses and identify a surprisingly long relaxation time on the order of 100 ms, which we relate to ionic redistribution both on the surface and within the thin film itself. (paper)

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

    Science.gov (United States)

    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. Static Characteristics of the Ferroelectric Transistor Inverter

    Science.gov (United States)

    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.

  14. Electrostatic micromotor based on ferroelectric ceramics

    Science.gov (United States)

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

    2004-11-01

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

  15. Field-effect transistor memories based on ferroelectric polymers

    Science.gov (United States)

    Zhang, Yujia; Wang, Haiyang; Zhang, Lei; Chen, Xiaomeng; Guo, Yu; Sun, Huabin; Li, Yun

    2017-11-01

    Field-effect transistors based on ferroelectrics have attracted intensive interests, because of their non-volatile data retention, rewritability, and non-destructive read-out. In particular, polymeric materials that possess ferroelectric properties are promising for the fabrications of memory devices with high performance, low cost, and large-area manufacturing, by virtue of their good solubility, low-temperature processability, and good chemical stability. In this review, we discuss the material characteristics of ferroelectric polymers, providing an update on the current development of ferroelectric field-effect transistors (Fe-FETs) in non-volatile memory applications. Program supported partially by the NSFC (Nos. 61574074, 61774080), NSFJS (No. BK20170075), and the Open Partnership Joint Projects of NSFC-JSPS Bilateral Joint Research Projects (No. 61511140098).

  16. Stability Issues on Perovskite Solar Cells

    Directory of Open Access Journals (Sweden)

    Xing Zhao

    2015-11-01

    Full Text Available Organo lead halide perovskite materials like methylammonium lead iodide (CH3NH3PbI3 and formamidinium lead iodide (HC(NH22PbI3 show superb opto-electronic properties. Based on these perovskite light absorbers, power conversion efficiencies of the perovskite solar cells employing hole transporting layers have increased from 9.7% to 20.1% within just three years. Thus, it is apparent that perovskite solar cell is a promising next generation photovoltaic technology. However, the unstable nature of perovskite was observed when exposing it to continuous illumination, moisture and high temperature, impeding the commercial development in the long run and thus becoming the main issue that needs to be solved urgently. Here, we discuss the factors affecting instability of perovskite and give some perspectives about further enhancement of stability of perovskite solar cell.

  17. Structural, microstructural, dielectric and ferroelectric properties of lead free Ba0.85Ca0.15Zr0.1Ti0.9O3 ceramic

    Science.gov (United States)

    Sharma, Sarita; Sharma, Hakikat; Negi, N. S.

    2018-05-01

    Lead free Ba0.85Ca0.15Zr0.1Ti0.9O3(BCTZ) ceramic has been synthesized by sol-gel method. Properties of material are studied at different sintering temperatures for 5 hours. Structural and microstructural properties are analyzed by using X-ray diffractrometer (XRD) and scanning electron microscopy (SEM) at annealing temperature of 850°C and 1050°C XRD pattern confirm the perovskite structure of the material without any unwanted phases crystalinity increased with increase of sintering temperature so as roughness and porosity is decreased as shown by SEM micrographs. There is large improvement in density with rise of sintering temperature which also leads to drastic change in ferroelectric and dielectric properties.

  18. Structural, magnetic and electric behavior of the new Ba2TiMoO6 material

    International Nuclear Information System (INIS)

    Alarcon-Suesca, C.E.; Opel, M.; TellezLandínez Téllez, D.A.; Roa-Rojas, J.

    2012-01-01

    We report synthesis and characterization of the structural, morphologic and ferroelectric behavior of the complex perovskite Ba 2 TiMoO 6 . Samples of Ba 2 TiMoO 6 were synthesized through standard solid state reaction methods. Crystalline structure was studied by means of X-ray diffraction experiments and Rietveld-like analysis. Results reveal that material crystallizes in a tetragonal structure, space group P4/mnm (no. 123), with cell parameters a=3.8557 Å and c=11.8678 Å. The tolerance factor of perovskite was determined to be 1.04. Surface morphology was examined using Scanning Electron Microscopy, which shows the micrometric granular character of samples with 1.0-5.0 μm mean grain size. Ferroelectric response of material was established from curves of polarization as a function of applied electric field. Our results reveal that Ba 2 TiMoO 6 double perovskite evidences a ferroelectric hysteretic behavior at ambient temperature and paramagnetic ordering. © 2011 Elsevier Science. All rights reserved.

  19. Ligand-Stabilized Reduced-Dimensionality Perovskites

    KAUST Repository

    Quan, Li Na; Yuan, Mingjian; Comin, Riccardo; Voznyy, Oleksandr; Beauregard, Eric M.; Hoogland, Sjoerd; Buin, Andrei; Kirmani, Ahmad R.; Zhao, Kui; Amassian, Aram; Kim, Dong Ha; Sargent, Edward H.

    2016-01-01

    Metal halide perovskites have rapidly advanced thin film photovoltaic performance; as a result, the materials’ observed instabilities urgently require a solution. Using density functional theory (DFT), we show that a low energy of formation, exacerbated in the presence of humidity, explains the propensity of perovskites to decompose back into their precursors. We find, also using DFT, that intercalation of phenylethylammonium between perovskite layers introduces quantitatively appreciable van der Waals interactions; and these drive an increased formation energy and should therefore improve material stability. Here we report the reduced-dimensionality (quasi-2D) perovskite films that exhibit improved stability while retaining the high performance of conventional three-dimensional perovskites. Continuous tuning of the dimensionality, as assessed using photophysical studies, is achieved by the choice of stoichiometry in materials synthesis. We achieved the first certified hysteresis-free solar power conversion in a planar perovskite solar cell, obtaining a 15.3% certified PCE, and observe greatly improved performance longevity.

  20. Ligand-Stabilized Reduced-Dimensionality Perovskites

    KAUST Repository

    Quan, Li Na

    2016-02-03

    Metal halide perovskites have rapidly advanced thin film photovoltaic performance; as a result, the materials’ observed instabilities urgently require a solution. Using density functional theory (DFT), we show that a low energy of formation, exacerbated in the presence of humidity, explains the propensity of perovskites to decompose back into their precursors. We find, also using DFT, that intercalation of phenylethylammonium between perovskite layers introduces quantitatively appreciable van der Waals interactions; and these drive an increased formation energy and should therefore improve material stability. Here we report the reduced-dimensionality (quasi-2D) perovskite films that exhibit improved stability while retaining the high performance of conventional three-dimensional perovskites. Continuous tuning of the dimensionality, as assessed using photophysical studies, is achieved by the choice of stoichiometry in materials synthesis. We achieved the first certified hysteresis-free solar power conversion in a planar perovskite solar cell, obtaining a 15.3% certified PCE, and observe greatly improved performance longevity.

  1. Multifunctional epitaxial systems on silicon substrates

    Energy Technology Data Exchange (ETDEWEB)

    Singamaneni, Srinivasa Rao, E-mail: ssingam@ncsu.edu [Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695 (United States); Materials Science Division, Army Research Office, Research Triangle Park, North Carolina 27709 (United States); Department of Physics, The University of Texas at El Paso, El Paso, Texas 79968 (United States); Prater, John Thomas [Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695 (United States); Materials Science Division, Army Research Office, Research Triangle Park, North Carolina 27709 (United States); Narayan, Jagdish [Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695 (United States)

    2016-09-15

    Multifunctional heterostructures can exhibit a wide range of functional properties, including colossal magneto-resistance, magnetocaloric, and multiferroic behavior, and can display interesting physical phenomena including spin and charge ordering and strong spin-orbit coupling. However, putting this functionality to work remains a challenge. To date, most of the work reported in the literature has dealt with heterostructures deposited onto closely lattice matched insulating substrates such as DyScO{sub 3}, SrTiO{sub 3} (STO), or STO buffered Si(100) using concepts of lattice matching epitaxy (LME). However, strain in heterostructures grown by LME is typically not fully relaxed and the layers contain detrimental defects such as threading dislocations that can significantly degrade the physical properties of the films and adversely affect the device characteristics. In addition, most of the substrates are incompatible with existing CMOS-based technology, where Si (100) substrates dominate. This review discusses recent advances in the integration of multifunctional oxide and non-oxide materials onto silicon substrates. An alternative thin film growth approach, called “domain matching epitaxy,” is presented which identifies approaches for minimizing lattice strain and unwanted defects in large misfit systems (7%–25% and higher). This approach broadly allows for the integration of multifunctional materials onto silicon substrates, such that sensing, computation, and response functions can be combined to produce next generation “smart” devices. In general, pulsed laser deposition has been used to epitaxially grow these materials, although the concepts developed here can be extended to other deposition techniques, as well. It will be shown that TiN and yttria-stabilized zirconia template layers provide promising platforms for the integration of new functionality into silicon-based computer chips. This review paper reports on a number of thin

  2. Ferroelectric relaxor Ba(TiCe)O3

    International Nuclear Information System (INIS)

    Chen Ang; Zhi Jing; Yu Zhi

    2002-01-01

    The dielectric behaviour of Ba(Ti 1-y Ce y )O 3 solid solutions (y=0-0.3) has been studied. A small amount of Ce doping (y=0.02) has weak influence on the dielectric behaviour of Ba(Ti 1-y Ce y )O 3 . With increasing Ce concentration, three phase transitions of pure BaTiO 3 are pinched into one rounded dielectric peak with frequency dispersion, and the relaxation time follows the Vogel-Fulcher relation. The evolution from a normal ferroelectric to a ferroelectric relaxor is emphasized. High strains (S=∼0.1-0.19%) with a small hysteresis under ac fields are obtained in ferroelectric relaxors Ba(Ti 1-y Ce y )O 3 . The physical mechanism of the relaxation process, the pinching effect of the phase transitions and their influence on the ferroelectric and electrostrictive behaviour are discussed. (author)

  3. Improving the Morphology of the Perovskite Absorber Layer in Hybrid Organic/Inorganic Halide Perovskite MAPbI3 Solar Cells

    Directory of Open Access Journals (Sweden)

    I. J. Ogundana

    2017-01-01

    Full Text Available Recently, perovskite solar cells have attracted tremendous attention due to their excellent power conversion efficiency, low cost, simple fabrications, and high photovoltaic performance. Furthermore, the perovskite solar cells are lightweight and possess thin film and semitransparency. However, the nonuniformity in perovskite layer constitutes a major setback to the operation mechanism, performance, reproducibility, and degradation of perovskite solar cells. Therefore, one of the main challenges in planar perovskite devices is the fabrication of high quality films with controlled morphology and least amount of pin-holes for high performance thin film perovskite devices. The poor reproducibility in perovskite solar cells hinders the accurate fabrication of practical devices for use in real world applications, and this is primarily as a result of the inability to control the morphology of perovskites, leading to large variability in the characteristics of perovskite solar cells. Hence, the focus of research in perovskites has been mostly geared towards improving the morphology and crystallization of perovskite absorber by selecting the optimal annealing condition considering the effect of humidity. Here we report a controlled ambient condition that is necessary to grow uniform perovskite crystals. A best PCE of 7.5% was achieved along with a short-circuit current density of 15.2 mA/cm2, an open-circuit voltage of 0.81 V, and a fill factor of 0.612 from the perovskite solar cell prepared under 60% relative humidity.

  4. Electronic transport in organometallic perovskite CH{sub 3}NH{sub 3}PbI{sub 3}: The role of organic cation orientations

    Energy Technology Data Exchange (ETDEWEB)

    Berdiyorov, G. R., E-mail: gberdiyorov@qf.org.qa; El-Mellouhi, F.; Madjet, M. E.; Rashkeev, S. N. [Qatar Environment and Energy Research Institute, Hamad Bin Khalifa University, Qatar Foundation, Doha (Qatar); Alharbi, F. H. [Qatar Environment and Energy Research Institute, Hamad Bin Khalifa University, Qatar Foundation, Doha (Qatar); College of Science and Engineering, Hamad Bin Khalifa University, Doha (Qatar)

    2016-02-01

    Density functional theory in combination with the nonequilibrium Green's function formalism is used to study the electronic transport properties of methylammonium lead-iodide perovskite CH{sub 3}NH{sub 3}PbI{sub 3}. Electronic transport in homogeneous ferroelectric and antiferroelectric phases, both of which do not contain any charged domain walls, is quite similar. The presence of charged domain wall drastically (by about an order of magnitude) enhances the electronic transport in the lateral direction. The increase of the transmission originates from the smaller variation of the electrostatic potential profile along the charged domain walls. This fact may provide a tool for tuning transport properties of such hybrid materials by manipulating molecular cations having dipole moment.

  5. Fast Ferroelectric L-Band Tuner for ILC Cavities

    Energy Technology Data Exchange (ETDEWEB)

    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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Aggarwal, Leena; Sekhon, Jagmeet S.; Arora, Ashima; Sheet, Goutam, E-mail: goutam@iisermohali.ac.in [Department of Physical Sciences, Indian Institute of Science Education and Research Mohali (IISER M), Sector 81, S. A. S. Nagar, Manauli PO-140306 (India); Guin, Satya N.; Negi, Devendra S.; Datta, Ranjan; Biswas, Kanishka, E-mail: kanishka@jncasr.ac.in [New Chemistry Unit and International Centre for Materials Science, Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR), Jakkur, Bangalore 560064 (India)

    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}.

  7. Subtractive fabrication of ferroelectric thin films with precisely controlled thickness

    Science.gov (United States)

    Ievlev, Anton V.; Chyasnavichyus, Marius; Leonard, Donovan N.; Agar, Joshua C.; Velarde, Gabriel A.; Martin, Lane W.; Kalinin, Sergei V.; Maksymovych, Petro; Ovchinnikova, Olga S.

    2018-04-01

    The ability to control thin-film growth has led to advances in our understanding of fundamental physics as well as to the emergence of novel technologies. However, common thin-film growth techniques introduce a number of limitations related to the concentration of defects on film interfaces and surfaces that limit the scope of systems that can be produced and studied experimentally. Here, we developed an ion-beam based subtractive fabrication process that enables creation and modification of thin films with pre-defined thicknesses. To accomplish this we transformed a multimodal imaging platform that combines time-of-flight secondary ion mass spectrometry with atomic force microscopy to a unique fabrication tool that allows for precise sputtering of the nanometer-thin layers of material. To demonstrate fabrication of thin-films with in situ feedback and control on film thickness and functionality we systematically studied thickness dependence of ferroelectric switching of lead-zirconate-titanate, within a single epitaxial film. Our results demonstrate that through a subtractive film fabrication process we can control the piezoelectric response as a function of film thickness as well as improve on the overall piezoelectric response versus an untreated film.

  8. Perovskite Solar Cell

    Indian Academy of Sciences (India)

    Organic–inorganic halide perovskite, a newcomerin the solar cell industry has proved its potential forincreasing efficiency rapidly from 3.8% in 2009 to 22.1% in2016. High efficiency, flexibility, and cell architecture of theemerging hybrid halide perovskite have caught the attentionof researchers and technologists in the field.

  9. Ferroelectric domain continuity over grain boundaries

    DEFF Research Database (Denmark)

    Mantri, Sukriti; Oddershede, Jette; Damjanovic, Dragan

    2017-01-01

    Formation and mobility of domain walls in ferroelectric materials is responsible for many of their electrical and mechanical properties. Domain wall continuity across grain boundaries has been observed since the 1950's and is speculated to affect the grain boundary-domain interactions, thereby...... impacting macroscopic ferroelectric properties in polycrystalline systems. However detailed studies of such correlated domain structures across grain boundaries are limited. In this work, we have developed the mathematical requirements for domain wall plane matching at grain boundaries of any given...... orientation. We have also incorporated the effect of grain boundary ferroelectric polarization charge created when any two domains meet at the grain boundary plane. The probability of domain wall continuity for three specific grain misorientations is studied. Use of this knowledge to optimize processing...

  10. Ferroelectric-gate field effect transistor memories device physics and applications

    CERN Document Server

    Ishiwara, Hiroshi; Okuyama, Masanori; Sakai, Shigeki; Yoon, Sung-Min

    2016-01-01

    This book provides comprehensive coverage of the materials characteristics, process technologies, and device operations for memory field-effect transistors employing inorganic or organic ferroelectric thin films. This transistor-type ferroelectric memory has interesting fundamental device physics and potentially large industrial impact. Among the various applications of ferroelectric thin films, the development of nonvolatile ferroelectric random access memory (FeRAM) has progressed most actively since the late 1980s and has achieved modest mass production levels for specific applications since 1995. There are two types of memory cells in ferroelectric nonvolatile memories. One is the capacitor-type FeRAM and the other is the field-effect transistor (FET)-type FeRAM. Although the FET-type FeRAM claims ultimate scalability and nondestructive readout characteristics, the capacitor-type FeRAMs have been the main interest for the major semiconductor memory companies, because the ferroelectric FET has fatal handic...

  11. In situ growth and characterization of La{sub 0.8}Sr{sub 0.2}CoO{sub 3} perovskite mixed conductor films

    Energy Technology Data Exchange (ETDEWEB)

    Brosha, E.L.; Chung, B.W.; Garzon, F.H.; Raistrick, I.D.; Houlton, R.J.; Hawley, M.E. [Los Alamos National Lab., NM (United States)

    1995-05-01

    The authors have grown thin films of La{sub 0.8}Sr{sub 0.2}CoO{sub 3} on SrTiO{sub 3} [100], MgO [100], yttrium-stabilized zirconia YSZ [100], and CeO{sub 2} [100]/Al{sub 2}O{sub 3} substrates by using a 90{degree} off-axis RF magnetron sputtering deposition. X-ray diffraction analysis reveals that, depending on substrate, the deposited films grew either epitaxially or highly textured. Scanning tunneling microscopy reveals that the thin films grow with a smooth surface and with different growth mechanisms according to substrate. For La{sub 0.8}Sr{sub 0.2}CoO{sub 3} thin films grown on MgO [100], the low values of the channeling minimum yield from Rutherford backscattering spectroscopy indicated excellent epitaxy with the substrate. Thin films of perovskite materials are among the major focal research areas for optical, sensor, electronic, and superconducting applications.

  12. Sol-gel reaction stability studied: Influence in the formation temperature and properties of ferroelectric thin films

    International Nuclear Information System (INIS)

    Perez, J.; Vilarinho, P.M.; Kholkin, A.L.; Almeida, A.

    2009-01-01

    Lead zirconium titanate (PZT) sol-gel solutions were prepared based on distilled lead acetate precursor solutions. A detailed analysis of the distillation effect on the lead precursor and the final PZT solution were carried out by Infrared and Raman techniques. It was found that the increase in the number of distillation steps experienced by the lead precursor solutions removes the constitutional water and increases the lead acetate-2-methoxyethanol interconnectivity; thus improving stability and avoiding the aging effect of the resulting PZT solutions. The thermal decomposition process of the PZT solutions was analyzed based on the thermogravimetric (TG) and differential thermogravimetric analysis (DTA) measurements. It was found that as the number of distillation steps in the lead precursor solutions increases, the decomposition rate increases and the formation temperature of pure perovskite PZT films decreases. X-ray diffraction (XRD) technique was used to study the film phase formation. A pure perovskite phase at 500 deg. C was found by the XRD analysis after the second distillation step. Scanning electron microscope technique was used to carry out the microstructural analysis. Dense microstructure was found in all analyzed films and an incipient columnar grain growth was revealed in PZT films prepared based on lead precursor solution with more than three distillation steps. The dependence of the dielectric, ferroelectric and piezoelectric properties on the number of distillation steps was revealed and a correlation between the distillation process, film microstructure properties and electrical performance was established

  13. Process for growing a film epitaxially upon a MGO surface and structures formed with the process

    Science.gov (United States)

    McKee, Rodney Allen; Walker, Frederick Joseph

    1998-01-01

    A process and structure wherein optical quality perovskites, such as BaTiO.sub.3 or SrTiO.sub.3, are grown upon a single crystal MgO substrate involves the epitaxial build up of alternating planes of TiO.sub.2 and metal oxide wherein the first plane grown upon the MgO substrate is a plane of TiO.sub.2. The layering sequence involved in the film build up reduces problems which would otherwise result from the interfacial electrostatics at the first atomic layers, and these oxides can be stabilized as commensurate thin films at a unit cell thickness or grown with high crystal quality to thicknesses of 0.5-0.7 .mu.m for optical device applications.

  14. Pyroelectric and dielectric properties of lead-free ferroelectric Ba3Nb2O8 ceramic

    International Nuclear Information System (INIS)

    Pati, Biswajit; Choudhary, R.N.P.; Das, Piyush R.; Parida, B.N.; Padhee, R.

    2014-01-01

    Graphical abstract: - Highlights: • Barium orthoniobate (lead-free perovskite) crystallizes as palmierite with structural stability. • The material exhibits ferroelectric phase transition of diffuse-type suitable for devices. • The low values of ε r and tan δ at high frequencies makes it a potential candidate for microwave applications. • The material has very good pyroelectric properties for detector application. • The material exhibits smaller value of dc activation energy. - Abstract: The present study highlights ferroelectric phase transition, dielectric, pyroelectric properties and conduction mechanism of highly crystallized barium orthoniobate (Ba 3 Nb 2 O 8 ) ceramic, prepared by a solid-state reaction technique. X-ray diffraction studies show the formation of a single-phase compound in hexagonal crystal system. Detailed studies of dielectric parameters (ε r and tan δ) of the compound as a function of temperature and frequency reveal their independence over a wide range of temperature and frequency. An anomaly in ε r suggests the possible existence of a ferroelectric–paraelectric phase transition of diffuse-type in the material. The low dielectric loss and moderate relative permittivity make this material (with certain modification) a potential candidate for microwave applications. Studies of pyroelectric properties reveal that the materials have reasonably high figure of merit useful for fabrication of pyroelectric detectors. The low-leakage current and negative temperature coefficient of resistance (NTCR) behavior of the sample have been verified from J–E plots. The nature of variation of dc conductivity with temperature confirms the Arrhenius and NTCR behavior of the material

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

    Science.gov (United States)

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

    2017-07-01

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

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

    International Nuclear Information System (INIS)

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

    2017-01-01

    Relaxor ferroelectricity, ferromagnetism and Second Harmonic Generation properties were founded and studied as a function of a reduction heat treatment at 650 °C in a Ar-5%H 2 atmosphere in stoichiometric La 0.05 Li 0.85 NbO 3 nanoparticles of 40 nm. A diffuse dielectric anomaly related with relaxor behavior from 25 °C to 800 °C in a frequency range from 100 Hz to 1 MHz was founded. It also shows ferromagnetic anhysterestic type and ferroelectric hysteresis loops at room temperature with a magnetic spin remnant of 2.5 × 10 −3 emu/g and polarization saturation of 0.235 μC/cm 2 , remnant polarization of 0.141 μC/cm 2 , coercive field of 1.35 kV/cm, respectively. It shows very good second harmonic generation signal at 450 nm and 500 nm. High Resolution Transmission Electron Microscopy, X-ray Photoelectron Spectroscopy and Raman spectroscopy, indicate an ABO 3 perovskite structure, new electronic binding energy structure for La (5s, 4d), Li (1s), Nb (4s, 3d, 4p) and oxygen (1s, 2s) and new vibrations modes on octahedron NbO 6 related to multiferroic single phase nanoparticles, respectively.

  17. Second harmonic generation in generalized Thue-Morse ferroelectric superlattices

    International Nuclear Information System (INIS)

    Wang Longxiang; Yang Xiangbo; Chen Tongsheng

    2009-01-01

    In this paper the second harmonic generation (SHG) in generalized Thue-Morse (GTM(m, n)) ferroelectric superlattices is studied. Under the small-signal approximation, the SHG spectra in both real and reciprocal spaces are investigated. It is found that: (1) only when the structure parameters l, l A , and l B are all chosen to be proper, can SHG in GTM(m, n) ferroelectric superlattices be generated; (2) for Family A of generalized Thue-Morse, GTM(m, 1) ferroelectric systems, with the increase of parameter m, the intense peaks of SHG concentrate on the long wavelength 1.4-1.5μm (the fundamental beam (FB) wavelength is within 0.8-1.5μm), but for Family B of generalized Thue-Morse, GTM(1, n) ferroelectric superlattices, with the increase of parameter n, the intense peaks of SHG concentrate on the middle wavelength 1.1-1.2μm; and (3) for GTM(m, 1) ferroelectric superlattices, the bigger the m, the stronger the relative integral intensity (RII) of SHG would be, but for GTM(1, n) ferroelectric systems, the bigger the n, the weaker the RII of SHG would be.

  18. An Automated Ab Initio Framework for Identifying New Ferroelectrics

    Science.gov (United States)

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

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

  19. Epitaxial growth of hybrid nanostructures

    Science.gov (United States)

    Tan, Chaoliang; Chen, Junze; Wu, Xue-Jun; Zhang, Hua

    2018-02-01

    Hybrid nanostructures are a class of materials that are typically composed of two or more different components, in which each component has at least one dimension on the nanoscale. The rational design and controlled synthesis of hybrid nanostructures are of great importance in enabling the fine tuning of their properties and functions. Epitaxial growth is a promising approach to the controlled synthesis of hybrid nanostructures with desired structures, crystal phases, exposed facets and/or interfaces. This Review provides a critical summary of the state of the art in the field of epitaxial growth of hybrid nanostructures. We discuss the historical development, architectures and compositions, epitaxy methods, characterization techniques and advantages of epitaxial hybrid nanostructures. Finally, we provide insight into future research directions in this area, which include the epitaxial growth of hybrid nanostructures from a wider range of materials, the study of the underlying mechanism and determining the role of epitaxial growth in influencing the properties and application performance of hybrid nanostructures.

  20. Perovskite classification: An Excel spreadsheet to determine and depict end-member proportions for the perovskite- and vapnikite-subgroups of the perovskite supergroup

    Science.gov (United States)

    Locock, Andrew J.; Mitchell, Roger H.

    2018-04-01

    Perovskite mineral oxides commonly exhibit extensive solid-solution, and are therefore classified on the basis of the proportions of their ideal end-members. A uniform sequence of calculation of the end-members is required if comparisons are to be made between different sets of analytical data. A Microsoft Excel spreadsheet has been programmed to assist with the classification and depiction of the minerals of the perovskite- and vapnikite-subgroups following the 2017 nomenclature of the perovskite supergroup recommended by the International Mineralogical Association (IMA). Compositional data for up to 36 elements are input into the spreadsheet as oxides in weight percent. For each analysis, the output includes the formula, the normalized proportions of 15 end-members, and the percentage of cations which cannot be assigned to those end-members. The data are automatically plotted onto the ternary and quaternary diagrams recommended by the IMA for depiction of perovskite compositions. Up to 200 analyses can be entered into the spreadsheet, which is accompanied by data calculated for 140 perovskite compositions compiled from the literature.

  1. Probing nanoscale ferroelectricity by ultraviolet Raman spectroscopy.

    Science.gov (United States)

    Tenne, D A; Bruchhausen, A; Lanzillotti-Kimura, N D; Fainstein, A; Katiyar, R S; Cantarero, A; Soukiassian, A; Vaithyanathan, V; Haeni, J H; Tian, W; Schlom, D G; Choi, K J; Kim, D M; Eom, C B; Sun, H P; Pan, X Q; Li, Y L; Chen, L Q; Jia, Q X; Nakhmanson, S M; Rabe, K M; Xi, X X

    2006-09-15

    We demonstrated that ultraviolet Raman spectroscopy is an effective technique to measure the transition temperature (Tc) in ferroelectric ultrathin films and superlattices. We showed that one-unit-cell-thick BaTiO3 layers in BaTiO3/SrTiO3 superlattices are not only ferroelectric (with Tc as high as 250 kelvin) but also polarize the quantum paraelectric SrTiO3 layers adjacent to them. Tc was tuned by approximately 500 kelvin by varying the thicknesses of the BaTiO3 and SrTiO3 layers, revealing the essential roles of electrical and mechanical boundary conditions for nanoscale ferroelectricity.

  2. Organic non-volatile memories from ferroelectric phase separated blends

    Science.gov (United States)

    Asadi, Kamal; de Leeuw, Dago; de Boer, Bert; Blom, Paul

    2009-03-01

    Ferroelectric polarisation is an attractive physical property for non-volatile binary switching. The functionality of the targeted memory should be based on resistive switching. Conductivity and ferroelectricity however cannot be tuned independently. The challenge is to develop a storage medium in which the favourable properties of ferroelectrics such as bistability and non-volatility can be combined with the beneficial properties provided by semiconductors such as conductivity and rectification. In this contribution we present an integrated solution by blending semiconducting and ferroelectric polymers into phase separated networks. The polarisation field of the ferroelectric modulates the injection barrier at the semiconductor--metal contact. This combination allows for solution-processed non-volatile memory arrays with a simple cross-bar architecture that can be read-out non-destructively. Based on this general concept a non-volatile, reversible switchable Schottky diode with relatively fast programming time of shorter than 100 microseconds, long information retention time of longer than 10^ days, and high programming cycle endurance with non-destructive read-out is demonstrated.

  3. A concept of ferroelectric microparticle propulsion thruster

    International Nuclear Information System (INIS)

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

    2008-01-01

    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 ∼9x10 -4 N. The obtained trajectories of microparticles demonstrate that the majority of the microparticles are positively charged, which permits further improvement of the thruster

  4. Ferroelectric Phase Diagram of PVDF:PMMA

    OpenAIRE

    Li, Mengyuan; Stingelin, Natalie; Michels, Jasper J.; Spijkman, Mark-Jan; Asadi, Kamal; Feldman, Kirill; Blom, Paul W. M.; de Leeuw, Dago M.

    2012-01-01

    We have investigated the ferroelectric phase diagram of poly(vinylidene fluoride) (PVDF) and poly(methyl methacrylate) (PMMA). The binary nonequilibrium temperature composition diagram was determined and melting of alpha- and beta-phase PVDF was identified. Ferroelectric beta-PVDF:PMMA blend films were made by melting, ice quenching, and subsequent annealing above the glass transition temperature of PMMA, close to the melting temperature of PVDF. Addition of PMMA suppresses the crystallizatio...

  5. Emergence of non-Fermi liquid behaviors in 5d perovskite SrIrO3 thin films: Interplay between correlation, disorder, and spin-orbit coupling

    Science.gov (United States)

    Biswas, Abhijit; Kim, Ki-Seok; Jeong, Yoon H.

    2016-02-01

    We investigate the effects of compressive strain on the electrical resistivity of 5d iridium based perovskite SrIrO3 by depositing epitaxial films of thickness 35 nm on various substrates such as GdScO3 (110), DyScO3 (110), and SrTiO3 (001). Surprisingly, we find anomalous transport behaviors as expressed by ρ∝Tε in the temperature dependent resistivity, where the temperature exponent ε evolves continuously from 4/5 to 1 and to 3/2 with an increase of compressive strain. Furthermore, magnetoresistance always remains positive irrespective of resistivity upturns at low temperatures. These observations imply that the delicate interplay between correlation and disorder in the presence of strong spin-orbit coupling is responsible for the emergence of the non-Fermi liquid behaviors in 5d perovskite SrIrO3 thin films. We offer a theoretical framework for the interpretation of the experimental results.

  6. Reversible optical control of macroscopic polarization in ferroelectrics

    Science.gov (United States)

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

    2018-01-01

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

  7. Hybrid perovskites: Approaches towards light-emitting devices

    KAUST Repository

    Alias, Mohd Sharizal

    2016-10-06

    The high optical gain and absorption of organic-inorganic hybrid perovskites have attracted extensive research for photonic device applications. Using the bromide halide as an example, we present key approaches of our work towards realizing efficient perovskites based light-emitters. The approaches involved determination of optical constants for the hybrid perovskites thin films, fabrication of photonic nanostructures in the form of subwavelength grating reflector patterned directly on the hybrid perovskites as light manipulation layer, and enhancing the emission property of the hybrid perovskites by using microcavity structure. Our results provide a platform for realization of hybrid perovskites based light-emitting devices for solid-state lighting and display applications. © 2016 IEEE.

  8. Hybrid perovskites: Approaches towards light-emitting devices

    KAUST Repository

    Alias, Mohd Sharizal; Dursun, Ibrahim; Priante, Davide; Saidaminov, Makhsud I.; Ng, Tien Khee; Bakr, Osman; Ooi, Boon S.

    2016-01-01

    The high optical gain and absorption of organic-inorganic hybrid perovskites have attracted extensive research for photonic device applications. Using the bromide halide as an example, we present key approaches of our work towards realizing efficient perovskites based light-emitters. The approaches involved determination of optical constants for the hybrid perovskites thin films, fabrication of photonic nanostructures in the form of subwavelength grating reflector patterned directly on the hybrid perovskites as light manipulation layer, and enhancing the emission property of the hybrid perovskites by using microcavity structure. Our results provide a platform for realization of hybrid perovskites based light-emitting devices for solid-state lighting and display applications. © 2016 IEEE.

  9. Light-Independent Ionic Transport in Inorganic Perovskite and Ultrastable Cs-Based Perovskite Solar Cells.

    Science.gov (United States)

    Zhou, Wenke; Zhao, Yicheng; Zhou, Xu; Fu, Rui; Li, Qi; Zhao, Yao; Liu, Kaihui; Yu, Dapeng; Zhao, Qing

    2017-09-07

    Due to light-induced effects in CH 3 NH 3 -based perovskites, such as ion migration, defects formation, and halide segregation, the degradation of CH 3 NH 3 -based perovskite solar cells under maximum power point is generally implicated. Here we demonstrated that the effect of light-enhanced ion migration in CH 3 NH 3 PbI 3 can be eliminated by inorganic Cs substitution, leading to an ultrastable perovskite solar cell. Quantitatively, the ion migration barrier for CH 3 NH 3 PbI 3 is 0.62 eV under dark conditions, larger than that of CsPbI 2 Br (0.45 eV); however, it reduces to 0.07 eV for CH 3 NH 3 PbI 3 under illumination, smaller than that for CsPbI 2 Br (0.43 eV). Meanwhile, photoinduced halide segregation is also suppressed in Cs-based perovskites. Cs-based perovskite solar cells retained >99% of the initial efficiency (10.3%) after 1500 h of maximum power point tracking under AM1.5G illumination, while CH 3 NH 3 PbI 3 solar cells degraded severely after 50 h of operation. Our work reveals an uncovered mechanism for stability improvement by inorganic cation substitution in perovskite-based optoelectronic devices.

  10. Electrical resistivity anomaly, valence shift of Pr ion, and magnetic behavior in epitaxial (Pr.sub.1-y./sub.Y.sub.y./sub.).sub.1-x./sub.Ca.sub.x./sub.CoO.sub.3./sub. thin films under compressive strain

    Czech Academy of Sciences Publication Activity Database

    Fujishiro, H.; Noda, Y.; Akuzawa, K.; Naito, T.; Ito, A.; Goto, T.; Maryško, Miroslav; Jirák, Zdeněk; Hejtmánek, Jiří; Nitta, K.

    2017-01-01

    Roč. 121, č. 11 (2017), s. 1-8, č. článku 115104. ISSN 0021-8979 R&D Projects: GA ČR GA17-04412S Institutional support: RVO:68378271 Keywords : perovskite cobaltites * spin state transition * variable valence * epitaxial strain * XANES Subject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.) Impact factor: 2.068, year: 2016

  11. Ferroelectricity in high-density H{sub 2}O ice

    Energy Technology Data Exchange (ETDEWEB)

    Caracas, Razvan, E-mail: razvan.caracas@ens-lyon.fr, E-mail: rhemley@ciw.edu [CNRS, Laboratoire de Géologie de Lyon UMR5276, Ecole Normale Supérieure de Lyon, 46, alleé d’Italie, Université Claude-Bernard Lyon 1, Université de Lyon, 69364 Lyon cedex 07 (France); Hemley, Russell J., E-mail: razvan.caracas@ens-lyon.fr, E-mail: rhemley@ciw.edu [Geophysical Laboratory, 5251 Broad Branch Road NW, Carnegie Institution of Washington, Washington, DC 20015 (United States)

    2015-04-07

    The origin of longstanding anomalies in experimental studies of the dense solid phases of H{sub 2}O 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.

  12. Cerium luminescence in nd0 perovskites

    International Nuclear Information System (INIS)

    Setlur, A.A.; Happek, U.

    2010-01-01

    The luminescence of Ce 3+ in perovskite (ABO 3 ) hosts with nd 0 B-site cations, specifically Ca(Hf,Zr)O 3 and (La,Gd)ScO 3 , is investigated in this report. The energy position of the Ce 3+ excitation and emission bands in these perovskites is compared to those of typical Al 3+ perovskites; we find a Ce 3+ 5d 1 centroid shift and Stokes shift that are larger versus the corresponding values for the Al 3+ perovskites. It is also shown that Ce 3+ luminescence quenching is due to Ce 3+ photoionization. The comparison between these perovskites shows reasonable correlations between Ce 3+ luminescence quenching, the energy position of the Ce 3+ 5d 1 excited state with respect to the host conduction band, and the host composition. - Graphical abstract: Ce 3+ decay times versus temperature for perovskites with nd 0 B-site cations.

  13. Grain Oriented Perovskite Layer Structure Ceramics for High-Temperature Piezoelectric Applications

    Science.gov (United States)

    Fuierer, Paul Anton

    The perovskite layer structure (PLS) compounds have the general formula (A^{2+}) _2(B^{5+})_2 O_7, or (A^ {3+})_2(B^{4+ })_2O_7, and crystallize in a very anisotropic layered structure consisting of parallel slabs made up of perovskite units. Several of these compounds possess the highest Curie temperatures (T_{rm c} ) of any known ferroelectrics. Two examples are Sr_2Nb_2O _7 with T_{rm c} of 1342^circC, and La_2Ti_2O _7 with T_{rm c} of 1500^circC. This thesis is an investigation of PLS ceramics and their feasibility as a high temperature transducer material. Piezoelectricity in single crystals has been measured, but the containerless float zone apparatus necessary to grow high quality crystals of these refractory compounds is expensive and limited to a small number of research groups. Previous attempts to pole polycrystalline Sr_2Nb _2O_7 have failed, and to this point piezoelectricity has been absent. The initiative taken in this research was to investigate PLS ceramics by way of composition and processing schemes such that polycrystalline bodies could be electrically poled. The ultimate objective then was to demonstrate piezoelectricity in PLS ceramics, especially at high temperatures. Donor-doping of both La_2Ti _2O_7 and Sr_2Nb_2O _7 was found to increase volume resistivities at elevated temperatures, an important parameter to consider during the poling process. Sr_2Ta _2O_7 (T _{rm c} = -107 ^circC) was used to make solid solution compositions with moderately high Curie temperatures, of about 850^circC, and lower coercive fields. A hot-forging technique was employed to produce ceramics with high density (>99% of theoretical) and high degree of grain orientation (>90%). Texturing was characterized by x-ray diffraction and microscopy. Considerable anisotropy was observed in physical and electrical properties, including thermal expansion, resistivity, dielectric constant, and polarization. The direction perpendicular to the forging axis proved to be the

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

    Science.gov (United States)

    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

  15. A novel readout integrated circuit for ferroelectric FPA detector

    Science.gov (United States)

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

    2017-11-01

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

  16. Perovskite Solar Cells: Progress and Advancements

    Directory of Open Access Journals (Sweden)

    Naveen Kumar Elumalai

    2016-10-01

    Full Text Available Organic–inorganic hybrid perovskite solar cells (PSCs have emerged as a new class of optoelectronic semiconductors that revolutionized the photovoltaic research in the recent years. The perovskite solar cells present numerous advantages include unique electronic structure, bandgap tunability, superior charge transport properties, facile processing, and low cost. Perovskite solar cells have demonstrated unprecedented progress in efficiency and its architecture evolved over the period of the last 5–6 years, achieving a high power conversion efficiency of about 22% in 2016, serving as a promising candidate with the potential to replace the existing commercial PV technologies. This review discusses the progress of perovskite solar cells focusing on aspects such as superior electronic properties and unique features of halide perovskite materials compared to that of conventional light absorbing semiconductors. The review also presents a brief overview of device architectures, fabrication methods, and interface engineering of perovskite solar cells. The last part of the review elaborates on the major challenges such as hysteresis and stability issues in perovskite solar cells that serve as a bottleneck for successful commercialization of this promising PV technology.

  17. Ultrafast Photovoltaic Response in Ferroelectric Nanolayers

    Science.gov (United States)

    2016-04-19

    the free energy of the system [3,4,8]. Intensive research has been aimed at bypassing the intrinsic size limits imposed by the depolarization field...Page 1 of 21   Ultrafast photovoltaic response in ferroelectric nanolayers Dan Daranciang1,2, Matthew J. Highland3, Haidan Wen4, Steve M. Young5...ferroelectric PbTiO3 via direct coupling to its intrinsic photovoltaic response. Using time-resolved x-ray scattering to visualize atomic displacements on

  18. Epitaxial growth of CZT(S,Se) on silicon

    Science.gov (United States)

    Bojarczuk, Nestor A.; Gershon, Talia S.; Guha, Supratik; Shin, Byungha; Zhu, Yu

    2016-03-15

    Techniques for epitaxial growth of CZT(S,Se) materials on Si are provided. In one aspect, a method of forming an epitaxial kesterite material is provided which includes the steps of: selecting a Si substrate based on a crystallographic orientation of the Si substrate; forming an epitaxial oxide interlayer on the Si substrate to enhance wettability of the epitaxial kesterite material on the Si substrate, wherein the epitaxial oxide interlayer is formed from a material that is lattice-matched to Si; and forming the epitaxial kesterite material on a side of the epitaxial oxide interlayer opposite the Si substrate, wherein the epitaxial kesterite material includes Cu, Zn, Sn, and at least one of S and Se, and wherein a crystallographic orientation of the epitaxial kesterite material is based on the crystallographic orientation of the Si substrate. A method of forming an epitaxial kesterite-based photovoltaic device and an epitaxial kesterite-based device are also provided.

  19. Functional Properties of Polydomain Ferroelectric Oxide Thin Films

    NARCIS (Netherlands)

    Houwman, Evert Pieter; Vergeer, Kurt; Koster, Gertjan; Rijnders, Augustinus J.H.M.; Nishikawa, H.; Iwata, N.; Endo, T.; Takamura, Y.; Lee, G-H.; Mele, P.

    2017-01-01

    The properties of a ferroelectric, (001)-oriented, thin film clamped to a substrate are investigated analytically and numerically. The emphasis is on the tetragonal, polydomain, ferroelectric phase, using a three domain structure, as is observed experimentally, instead of the two-domain structure

  20. Depolarization corrections to the coercive field in thin-film ferroelectrics

    International Nuclear Information System (INIS)

    Dawber, M; Chandra, P; Littlewood, P B; Scott, J F

    2003-01-01

    Empirically, the coercive field needed to reverse the polarization in a ferroelectric increases with decreasing film thickness. For ferroelectric films of 100 μm to 100 nm in thickness the coercive field has been successfully described by a semi-empirical scaling law. Accounting for depolarization corrections, we show that this scaling behaviour is consistent with field measurements of ultrathin ferroelectric capacitors down to one nanometre in film thickness. Our results also indicate that the minimum film thickness, determined by a polarization instability, can be tuned by the choice of electrodes, and recommendations for next-generation ferroelectric devices are discussed. (letter to the editor)

  1. Depolarization corrections to the coercive field in thin-film ferroelectrics

    CERN Document Server

    Dawber, M; Littlewood, P B; Scott, J F

    2003-01-01

    Empirically, the coercive field needed to reverse the polarization in a ferroelectric increases with decreasing film thickness. For ferroelectric films of 100 mu m to 100 nm in thickness the coercive field has been successfully described by a semi-empirical scaling law. Accounting for depolarization corrections, we show that this scaling behaviour is consistent with field measurements of ultrathin ferroelectric capacitors down to one nanometre in film thickness. Our results also indicate that the minimum film thickness, determined by a polarization instability, can be tuned by the choice of electrodes, and recommendations for next-generation ferroelectric devices are discussed. (letter to the editor)

  2. Development of Perovskite-Type Materials for Thermoelectric Application

    Directory of Open Access Journals (Sweden)

    Tingjun Wu

    2018-06-01

    Full Text Available Oxide perovskite materials have a long history of being investigated for thermoelectric applications. Compared to the state-of-the-art tin and lead chalcogenides, these perovskite compounds have advantages of low toxicity, eco-friendliness, and high elemental abundance. However, because of low electrical conductivity and high thermal conductivity, the total thermoelectric performance of oxide perovskites is relatively poor. Variety of methods were used to enhance the TE properties of oxide perovskite materials, such as doping, inducing oxygen vacancy, embedding crystal imperfection, and so on. Recently, hybrid perovskite materials started to draw attention for thermoelectric application. Due to the low thermal conductivity and high Seebeck coefficient feature of hybrid perovskites materials, they can be promising thermoelectric materials and hold the potential for the application of wearable energy generators and cooling devices. This mini-review will build a bridge between oxide perovskites and burgeoning hybrid halide perovskites in the research of thermoelectric properties with an aim to further enhance the relevant performance of perovskite-type materials.

  3. Ambipolar solution-processed hybrid perovskite phototransistors

    KAUST Repository

    Li, Feng

    2015-09-08

    Organolead halide perovskites have attracted substantial attention because of their excellent physical properties, which enable them to serve as the active material in emerging hybrid solid-state solar cells. Here we investigate the phototransistors based on hybrid perovskite films and provide direct evidence for their superior carrier transport property with ambipolar characteristics. The field-effect mobilities for triiodide perovskites at room temperature are measured as 0.18 (0.17) cm2 V−1 s−1 for holes (electrons), which increase to 1.24 (1.01) cm2 V−1 s−1 for mixed-halide perovskites. The photoresponsivity of our hybrid perovskite devices reaches 320 A W−1, which is among the largest values reported for phototransistors. Importantly, the phototransistors exhibit an ultrafast photoresponse speed of less than 10 μs. The solution-based process and excellent device performance strongly underscore hybrid perovskites as promising material candidates for photoelectronic applications.

  4. EDITORIAL: Epitaxial graphene Epitaxial graphene

    Science.gov (United States)

    de Heer, Walt A.; Berger, Claire

    2012-04-01

    Graphene is widely regarded as an important new electronic material with interesting two-dimensional electron gas properties. Not only that, but graphene is widely considered to be an important new material for large-scale integrated electronic devices that may eventually even succeed silicon. In fact, there are countless publications that demonstrate the amazing applications potential of graphene. In order to realize graphene electronics, a platform is required that is compatible with large-scale electronics processing methods. It was clear from the outset that graphene grown epitaxially on silicon carbide substrates was exceptionally well suited as a platform for graphene-based electronics, not only because the graphene sheets are grown directly on electronics-grade silicon carbide (an important semiconductor in its own right), but also because these sheets are oriented with respect to the semiconductor. Moreover, the extremely high temperatures involved in production assure essentially defect-free and contamination-free materials with well-defined interfaces. Epitaxial graphene on silicon carbide is not a unique material, but actually a class of materials. It is a complex structure consisting of a reconstructed silicon carbide surface, which, for planar hexagonal silicon carbide, is either the silicon- or the carbon-terminated face, an interfacial carbon rich layer, followed by one or more graphene layers. Consequently, the structure of graphene films on silicon carbide turns out to be a rich surface-science puzzle that has been intensively studied and systematically unravelled with a wide variety of surface science probes. Moreover, the graphene films produced on the carbon-terminated face turn out to be rotationally stacked, resulting in unique and important structural and electronic properties. Finally, in contrast to essentially all other graphene production methods, epitaxial graphene can be grown on structured silicon carbide surfaces to produce graphene

  5. Heterogeneous Two-Phase Pillars in Epitaxial NiFe 2 O 4 -LaFeO 3 Nanocomposites

    Energy Technology Data Exchange (ETDEWEB)

    Comes, Ryan B. [Physical and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland WA 99352 USA; Department of Physics, Auburn University, Auburn AL 36849 USA; Perea, Daniel E. [Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland WA 99352 USA; Spurgeon, Steven R. [Physical and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland WA 99352 USA

    2017-07-10

    Self-assembled epitaxial oxide nanocomposites have been explored for a wide range of applications, including multiferroic and magnetoelectric properties, plasmonics, and catalysis. These so-called “vertically aligned nanocomposites” form spontaneously during the deposition process when segregation into two phases is energetically favorable as compared to a solid solution. However, there has been surprisingly little work understanding the driving forces that govern the synthesis of these materials, which can include point defect energetics, surface diffusion, and interfacial energies. To explore these factors, La-Ni-Fe-O films have been synthesized by molecular beam epitaxy and it is shown that these phase segregate into spinel-perovskite nanocomposites. Using complementary scanning transmission electron microscopy and atom-probe tomography, the elemental composition of each phase is examined and found that Ni ions are exclusively found in the spinel phase. From correlative analysis, a model for the relative favorability of the Ni2+ and Ni3+ valences under the growth conditions is developed. It is shown that multidimensional characterization techniques provide previously unobserved insight into the growth process and complex driving forces for phase segregation.

  6. Structural, magnetic and electric behavior of the new Ba{sub 2}TiMoO{sub 6} material

    Energy Technology Data Exchange (ETDEWEB)

    Alarcon-Suesca, C.E. [Grupo de Fisica de Nuevos Materiales, Departamento de Fisica, Universidad Nacional de Colombia, Carrera 30 calle 45, Bogota D.C., AA 5997 (Colombia); Chemistry Department, Technische Universitaet Muenchen, Lichtenbergstrasse, D-85748 Garching (Germany); Opel, M. [Walther-Meissner-Institut, Bayerische Akademie der Wissenschaften, D-85748 Garching (Germany); TellezLandinez Tellez, D.A. [Grupo de Fisica de Nuevos Materiales, Departamento de Fisica, Universidad Nacional de Colombia, Carrera 30 calle 45, Bogota D.C., AA 5997 (Colombia); Roa-Rojas, J., E-mail: jroar@unal.edu.co [Grupo de Fisica de Nuevos Materiales, Departamento de Fisica, Universidad Nacional de Colombia, Carrera 30 calle 45, Bogota D.C., AA 5997 (Colombia)

    2012-08-15

    We report synthesis and characterization of the structural, morphologic and ferroelectric behavior of the complex perovskite Ba{sub 2}TiMoO{sub 6}. Samples of Ba{sub 2}TiMoO{sub 6} were synthesized through standard solid state reaction methods. Crystalline structure was studied by means of X-ray diffraction experiments and Rietveld-like analysis. Results reveal that material crystallizes in a tetragonal structure, space group P4/mnm (no. 123), with cell parameters a=3.8557 A and c=11.8678 A. The tolerance factor of perovskite was determined to be 1.04. Surface morphology was examined using Scanning Electron Microscopy, which shows the micrometric granular character of samples with 1.0-5.0 {mu}m mean grain size. Ferroelectric response of material was established from curves of polarization as a function of applied electric field. Our results reveal that Ba{sub 2}TiMoO{sub 6} double perovskite evidences a ferroelectric hysteretic behavior at ambient temperature and paramagnetic ordering. Copyright-Sign 2011 Elsevier Science. All rights reserved.

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

    Science.gov (United States)

    Wibowo, Arief Cahyo

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

  8. Proceedings of the 8th International Symposium on Applications of Ferroelectrics

    Science.gov (United States)

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

    1993-02-01

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

  9. Emergence of non-Fermi liquid behaviors in 5d perovskite SrIrO{sub 3} thin films: Interplay between correlation, disorder, and spin-orbit coupling

    Energy Technology Data Exchange (ETDEWEB)

    Biswas, Abhijit [Department of Physics, POSTECH, Pohang 790-784 (Korea, Republic of); Kim, Ki-Seok [Department of Physics, POSTECH, Pohang 790-784 (Korea, Republic of); Institute of Edge of Theoretical Science (IES), POSTECH, Pohang 790-784 (Korea, Republic of); Jeong, Yoon H., E-mail: yhj@postech.ac.kr [Department of Physics, POSTECH, Pohang 790-784 (Korea, Republic of)

    2016-02-15

    We investigate the effects of compressive strain on the electrical resistivity of 5d iridium based perovskite SrIrO{sub 3} by depositing epitaxial films of thickness 35 nm on various substrates such as GdScO{sub 3} (110), DyScO{sub 3} (110), and SrTiO{sub 3} (001). Surprisingly, we find anomalous transport behaviors as expressed by ρ∝T{sup ε} in the temperature dependent resistivity, where the temperature exponent ε evolves continuously from 4/5 to 1 and to 3/2 with an increase of compressive strain. Furthermore, magnetoresistance always remains positive irrespective of resistivity upturns at low temperatures. These observations imply that the delicate interplay between correlation and disorder in the presence of strong spin-orbit coupling is responsible for the emergence of the non-Fermi liquid behaviors in 5d perovskite SrIrO{sub 3} thin films. We offer a theoretical framework for the interpretation of the experimental results. - Highlights: • We studied the effect of compressive strain on the perovskite SrIrO{sub 3} thin films. • We revealed non-Fermi liquid behaviors in the transport properties. • Irrespective of weak localization effects, magnetoresistance remains positive. • Mott-Anderson-Griffiths scenario is proposed to account for the NFL behaviors.

  10. Atomic oxygen effect on the in situ growth of stoichiometric YBa2Cu3O7 - delta epitaxial films by facing targets 90° off-axis radiofrequency magnetron sputtering

    Science.gov (United States)

    Oya, Gin-ichiro; Diao, Chien Chen; Imai, Syozo; Uzawa, Takaaki; Sawada, Yasuji; Sugai, Tokuko; Nakajima, Kensuke; Yamashita, Tsutomu

    1995-06-01

    (110)- and (103)-oriented almost stoichiometric YBa2Cu3O7-δ (YBCO) films have been grown epitaxially on hot SrTiO3 (110) substrates using a 90° off-axis rf magnetron sputtering technique, for fabrication of vertical sandwich-type YBCO/insulator/YBCO or YBCO/normal metal/YBCO Josephson junctions utilizing the high-quality YBCO films. The YBCO epitaxial films with high transition temperatures Tc of ˜90 K have been deposited in situ only under the conditions of substrate temperatures Ts of ˜650-˜700 °C and oxygen partial pressure PO2 of ˜5×10-3-˜10×10-3 Torr, which are in close proximity to the critical stability/decomposition line for YBa2Cu3O6 in the ordinary Y-Ba-Cu-O phase diagram. Using a quadrupole mass spectrometer, a high density of atomic oxygen has directly been observed to be efficiently produced in the sputter glow discharge under the above optimum conditions of PO2. This atomic oxygen has played a key role in promoting the formation of the perovskite structure and the epitaxial growth of the YBCO films. Furthermore, Shapiro steps have successfully been observed for a Nb-YBCO point-contact junction, which is made by pressing a Nb needle on a surface-etched YBCO epitaxial film, under 525.4 GHz submillimeter-wave irradiation.

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

    Science.gov (United States)

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

    2013-06-25

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

  12. Temperature dependence of electronic transport property in ferroelectric polymer films

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-10-15

    Highlights: • The ferroelectric polymer was fabricated by Langmuir–Blodgett method. • The electrons as the dominant injected carrier were conformed in the ferroelectric polymer films. • The leakage current conduction mechanisms in ferroelectric polymer were investigated. - Abstract: 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.

  13. Enhanced dielectric nonlinearity in epitaxial Pb{sub 0.92}La{sub 0.08}Zr{sub 0.52}Ti{sub 0.48}O{sub 3} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Chunrui, E-mail: chunrui.ma@gmail.com, E-mail: jwu@ku.edu; Wu, Judy, E-mail: chunrui.ma@gmail.com, E-mail: jwu@ku.edu [Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas, 66045 (United States); Ma, Beihai [Energy Systems Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Mi, Shao-Bo [Electronic Materials Research Laboratory, Key Laboratory of the Ministry of Education and International Center for Dielectric Research, Xi' an Jiaotong University, Xi' an 710049 (China); Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China); Liu, Ming [Electronic Materials Research Laboratory, Key Laboratory of the Ministry of Education and International Center for Dielectric Research, Xi' an Jiaotong University, Xi' an 710049 (China)

    2014-04-21

    High quality c-axis oriented epitaxial Pb{sub 0.92}La{sub 0.08}Zr{sub 0.52}Ti{sub 0.48}O{sub 3} films were fabricated using pulsed laser deposition on (001) LaAlO{sub 3} substrates with conductive LaNiO{sub 3} buffers. Besides confirmation of the in-plane and out-of-plane orientations using X-ray diffraction, transmission electron microscopy study has revealed columnar structure across the film thickness with column width around 100 nm. Characterization of ferroelectric properties was carried out in comparison with polycrystalline Pb{sub 0.92}La{sub 0.08}Zr{sub 0.52}Ti{sub 0.48}O{sub 3} films to extract the effect of epitaxial growth. It is found that the ratio between the irreversible Rayleigh parameter and reversible parameter increased up to 0.028 cm/kV at 1 kHz on epitaxial samples, which is more than twice of that on their polycrystalline counterparts. While this ratio decreased to 0.022 cm/kV with increasing frequency to100 kHz, a much less frequency dependence was observed as compared to the polycrystalline case. The epitaxial Pb{sub 0.92}La{sub 0.08}Zr{sub 0.52}Ti{sub 0.48}O{sub 3} films exhibited a higher mobility of domain wall and the higher extrinsic contribution to the dielectric properties, as well as reduced density of defects, indicating that it is promising for tunable and low power consumption devices.

  14. Photovoltaic Effect of 2D Homologous Perovskites

    International Nuclear Information System (INIS)

    Jung, Mi-Hee

    2017-01-01

    Highlights: • The mixed perovskite was prepared by exposure of MAI gas on the BAPbI_4 film. • The increased dimensional perovskite shows a smaller band gap than 2D perovskite. • The mixed perovskite system shows the vertical crystal orientation. • The mixed perovskite cell exhibits the higher Jsc and FF than 2D perovskite cell. - Abstract: The controlled growth of mixed dimensional perovskite structures, (C_6H_5CH_2NH_2)(CH_3NH_3)_n_-_1Pb_nI_3_n_+_1, through the introduction of CH_3NH_3I molecule vapor into the two-dimensional perovskite C_6H_5CH_2NH_3PbI_4 structure and its application in photovoltaic devices is reported. The dimensionality of (C_6H_5CH_2NH_2)(CH_3NH_3)_n_-_1Pb_nI_3_n_+_1 is controlled using the exposure time to the CH_3NH_3I vapor on the C_6H_5CH_2NH_3PbI_4 perovskite film. As the stacking of the lead iodide lattice increases, the crystallographic planes of the inorganic perovskite compound exhibit vertical growth in order to facilitate efficient charge transport. Furthermore, the devices have a smaller band gap, which offers broader absorption and the potential to increase the photocurrent density in the solar cell. As a result, the photovoltaic device based on the (C_6H_5CH_2NH_2)(CH_3NH_3)_n_-_1Pb_nI_3_n_+_1 perovskite exhibits a power conversion efficiency of 5.43% with a short circuit current density of 14.49 mA cm"−"2, an open circuit voltage of 0.85 V, and a fill factor of 44.30 for the best power conversion efficiency under AM 1.5G solar irradiation (100 mW cm"−"2), which is significantly higher than the 0.34% of the pure two-dimensional BAPbI_4 perovskite-based solar cell.

  15. Hybrid dual gate ferroelectric memory for multilevel information storage

    KAUST Repository

    Khan, Yasser

    2015-01-01

    Here, we report hybrid organic/inorganic ferroelectric memory with multilevel information storage using transparent p-type SnO semiconductor and ferroelectric P(VDF-TrFE) polymer. The dual gate devices include a top ferroelectric field-effect transistor (FeFET) and a bottom thin-film transistor (TFT). The devices are all fabricated at low temperatures (∼200°C), and demonstrate excellent performance with high hole mobility of 2.7 cm2 V-1 s-1, large memory window of ∼18 V, and a low sub-threshold swing ∼-4 V dec-1. The channel conductance of the bottom-TFT and the top-FeFET can be controlled independently by the bottom and top gates, respectively. The results demonstrate multilevel nonvolatile information storage using ferroelectric memory devices with good retention characteristics.

  16. Amine treatment induced perovskite nanowire network in perovskite solar cells: efficient surface passivation and carrier transport

    Science.gov (United States)

    Xiao, Ke; Cui, Can; Wang, Peng; Lin, Ping; Qiang, Yaping; Xu, Lingbo; Xie, Jiangsheng; Yang, Zhengrui; Zhu, Xiaodong; Yu, Xuegong; Yang, Deren

    2018-02-01

    In the fabrication of high efficiency organic-inorganic metal halide perovskite solar cells (PSCs), an additional interface modifier is usually applied for enhancing the interface passivation and carrier transport. In this paper, we develop an innovative method with in-situ growth of one-dimensional perovskite nanowire (1D PNW) network triggered by Lewis amine over the perovskite films. To our knowledge, this is the first time to fabricate PSCs with shape-controlled perovskite surface morphology, which improved power conversion efficiency (PCE) from 14.32% to 16.66% with negligible hysteresis. The amine molecule can passivate the trap states on the polycrystalline perovskite surface to reduce trap-state density. Meanwhile, as a fast channel, the 1D PNWs would promote carrier transport from the bulk perovskite film to the electron transport layer. The PSCs with 1D PNW modification not only exhibit excellent photovoltaic performances, but also show good stability with only 4% PCE loss within 30 days in the ambient air without encapsulation. Our results strongly suggest that in-situ grown 1D PNW network provides a feasible and effective strategy for nanostructured optoelectronic devices such as PSCs to achieve superior performances.

  17. Understanding the physical properties of hybrid perovskites for photovoltaic applications

    Science.gov (United States)

    Huang, Jinsong; Yuan, Yongbo; Shao, Yuchuan; Yan, Yanfa

    2017-07-01

    New photovoltaic materials have been searched for in the past decades for clean and renewable solar energy conversion with an objective of reducing the levelized cost of electricity (that is, the unit price of electricity over the course of the device lifetime). An emerging family of semiconductor materials — organic-inorganic halide perovskites (OIHPs) — are the focus of the photovoltaic research community owing to their use of low cost, nature-abundant raw materials, low-temperature and scalable solution fabrication processes, and, in particular, the very high power conversion efficiencies that have been achieved within the short time of their development. In this Review, we summarize and critically assess the most recent advances in understanding the physical properties of both 3D and low-dimensional OIHPs that favour a small open-circuit voltage deficit and high power conversion efficiency. Several prominent topics in this field on the unique properties of OIHPs are surveyed, including defect physics, ferroelectricity, exciton dissociation processes, carrier recombination lifetime and photon recycling. The impact of ion migration on solar cell efficiency and stability are also critically analysed. Finally, we discuss the remaining challenges in the commercialization of OIHP photovoltaics.

  18. Relaxor ferroelectricity, ferromagnetic and optical second harmonic properties in lanthanum lithium niobate (La{sub 0.05}Li{sub 0.85}NbO{sub 3}) nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Díaz-Moreno, Carlos A., E-mail: cdiazmoreno@utep.edu [Department of Physics of University of Texas at El Paso, 500 W. University Ave, El Paso, TX 79968 (United States); Ding, Yu; Li, Chunqiang [Department of Physics of University of Texas at El Paso, 500 W. University Ave, El Paso, TX 79968 (United States); Portelles, Jorge [Facultad de Física, Universidad de La Habana, San lázaro y L, 10400 (Cuba); Universidad Nacional Autónoma de México, Centro de Nanociencias y Nanotecnología, km 107 Carretera Tijuana-Ensenada, Ensenada, B.C. 22860 (Mexico); Heiras, J. [Universidad Nacional Autónoma de México, Centro de Nanociencias y Nanotecnología, km 107 Carretera Tijuana-Ensenada, Ensenada, B.C. 22860 (Mexico); Hurtado-Macias, A. [Centro de Investigación en Materiales Avanzados S.C., Miguel de Cervantes #120, Complejo Industrial Chihuahua, Chihuahua, C.P. 31109 (Mexico); Department of Physics and Astronomy, University of Texas at San Antonio, One UTSA Circle, San Antonio, TX 78249 (United States); Farias, J.R. [Instituto de Ingeniería y Tecnología, UACJ, Avenida del Charro #450 N. Cd. Juárez, Chihuahua, C.P. 32310 (Mexico); González-Hernández, J. [Centro de Ingeniería y Desarrollo Industrial, Santiago de Querétaro 76130, Qro (Mexico); Yacamán, M.J. [Department of Physics and Astronomy, University of Texas at San Antonio, One UTSA Circle, San Antonio, TX 78249 (United States); and others

    2017-07-01

    Relaxor ferroelectricity, ferromagnetism and Second Harmonic Generation properties were founded and studied as a function of a reduction heat treatment at 650 °C in a Ar-5%H{sub 2} atmosphere in stoichiometric La{sub 0.05}Li{sub 0.85}NbO{sub 3} nanoparticles of 40 nm. A diffuse dielectric anomaly related with relaxor behavior from 25 °C to 800 °C in a frequency range from 100 Hz to 1 MHz was founded. It also shows ferromagnetic anhysterestic type and ferroelectric hysteresis loops at room temperature with a magnetic spin remnant of 2.5 × 10{sup −3} emu/g and polarization saturation of 0.235 μC/cm{sup 2}, remnant polarization of 0.141 μC/cm{sup 2}, coercive field of 1.35 kV/cm, respectively. It shows very good second harmonic generation signal at 450 nm and 500 nm. High Resolution Transmission Electron Microscopy, X-ray Photoelectron Spectroscopy and Raman spectroscopy, indicate an ABO{sub 3} perovskite structure, new electronic binding energy structure for La (5s, 4d), Li (1s), Nb (4s, 3d, 4p) and oxygen (1s, 2s) and new vibrations modes on octahedron NbO{sub 6} related to multiferroic single phase nanoparticles, respectively.

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

    Directory of Open Access Journals (Sweden)

    G. G. Guzmán-Verri

    2016-06-01

    Full Text Available 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.

  20. A prediction of rate-dependent behaviour in ferroelectric polycrystals

    International Nuclear Information System (INIS)

    Kim, Sang-Joo

    2007-01-01

    Rate-dependent behaviour of a polycrystalline ferroelectric material is predicted based on thermal activation theory and a representative volume element model. First, the behaviour of a ferroelectric single crystal is calculated from a recently proposed three-dimensional free energy model [S.J. Kim, S. Seelecke, Int. J. Solids Struct. 44 (2007) 1196-1209]. Then, from the calculated single crystal responses, poling behaviour of a ferroelectric polycrystal is obtained in three different ways, two representative volume element models and Gaussian integration method. It is found that a dodecahedron representative volume element consisting of 210 crystallites is the best choice among the three methods. Finally, the behaviour of a ferroelectric polycrystal under various electric and stress loads is calculated using the chosen RVE model. The calculated responses are compared qualitatively with experimental observations, and the effects of crystal orientation and polycrystallinity are discussed

  1. Perovskite oxide SrTiO3 as an efficient electron transporter for hybrid perovskite solar cells

    KAUST Repository

    Bera, Ashok

    2014-12-11

    In this work, we explored perovskite oxide SrTiO3 (STO) for the first time as the electron-transporting layer in organolead trihalide perovskite solar cells. The steady-state photoluminescence (PL) quenching and transient absorption experiments revealed efficient photoelectron transfer from CH3NH3PbI3-xClx to STO. Perovskite solar cells with meso-STO exhibit an open circuit voltage of 1.01 V, which is 25% higher than the value of 0.81 V achieved in the control device with the conventional meso-TiO2. In addition, an increase of 17% in the fill factor was achieved by tailoring the thickness of the meso-STO layer. We found that the application of STO leads to uniform perovskite layers with large grains and complete surface coverage, leading to a high shunt resistance and improved performance. These findings suggest STO as a competitive candidate as electron transport material in organometal perovskite solar cells.

  2. Paintable Carbon-Based Perovskite Solar Cells with Engineered Perovskite/Carbon Interface Using Carbon Nanotubes Dripping Method.

    Science.gov (United States)

    Ryu, Jaehoon; Lee, Kisu; Yun, Juyoung; Yu, Haejun; Lee, Jungsup; Jang, Jyongsik

    2017-10-01

    Paintable carbon electrode-based perovskite solar cells (PSCs) are of particular interest due to their material and fabrication process costs, as well as their moisture stability. However, printing the carbon paste on the perovskite layer limits the quality of the interface between the perovskite layer and carbon electrode. Herein, an attempt to enhance the performance of the paintable carbon-based PSCs is made using a modified solvent dripping method that involves dripping of the carbon nanotubes (CNTs), which is dispersed in chlorobenzene solution. This method allows CNTs to penetrate into both the perovskite film and carbon electrode, facilitating fast hole transport between the two layers. Furthermore, this method is results in increased open circuit voltage (V oc ) and fill factor (FF), providing better contact at the perovskite/carbon interfaces. The best devices made with CNT dripping show 13.57% power conversion efficiency and hysteresis-free performance. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Perovskite oxide SrTiO3 as an efficient electron transporter for hybrid perovskite solar cells

    KAUST Repository

    Bera, Ashok; Wu, Kewei; Sheikh, Arif D.; Alarousu, Erkki; Mohammed, Omar F.; Wu, Tao

    2014-01-01

    In this work, we explored perovskite oxide SrTiO3 (STO) for the first time as the electron-transporting layer in organolead trihalide perovskite solar cells. The steady-state photoluminescence (PL) quenching and transient absorption experiments revealed efficient photoelectron transfer from CH3NH3PbI3-xClx to STO. Perovskite solar cells with meso-STO exhibit an open circuit voltage of 1.01 V, which is 25% higher than the value of 0.81 V achieved in the control device with the conventional meso-TiO2. In addition, an increase of 17% in the fill factor was achieved by tailoring the thickness of the meso-STO layer. We found that the application of STO leads to uniform perovskite layers with large grains and complete surface coverage, leading to a high shunt resistance and improved performance. These findings suggest STO as a competitive candidate as electron transport material in organometal perovskite solar cells.

  4. Structural, dielectric and ferroelectric characterization of PZT thin films

    Directory of Open Access Journals (Sweden)

    Araújo E.B.

    1999-01-01

    Full Text Available In this work ferroelectric thin films of PZT were prepared by the oxide precursor method, deposited on Pt/Si substrate. Films of 0.5 mm average thickness were obtained. Electrical and ferroelectric characterization were carried out in these films. The measured value of the dielectric constant for films was 455. Ferroelectricity was confirmed by Capacitance-Voltage (C-V characteristics and P-E hysteresis loops. Remanent polarization for films presented value around 5.0 µC/cm2 and a coercive field of 88.8 kV/cm.

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

    Science.gov (United States)

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

    2018-05-01

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

  6. High-performance solution-processed polymer ferroelectric field-effect transistors

    NARCIS (Netherlands)

    Naber, RCG; Tanase, C; Blom, PWM; Gelinck, GH; Marsman, AW; Touwslager, FJ; Setayesh, S; De Leeuw, DM; Naber, Ronald C.G.; Gelinck, Gerwin H.; Marsman, Albert W.; Touwslager, Fred J.

    We demonstrate a rewritable, non-volatile memory device with flexible plastic active layers deposited from solution. The memory device is a ferroelectric field-effect transistor (FeFET) made with a ferroelectric fluoropolymer and a bisalkoxy-substituted poly(p-phenylene vinylene) semiconductor

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

    Science.gov (United States)

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

    2010-07-20

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

  8. Oxyfluoride Chemistry of Layered Perovskite Compounds

    Directory of Open Access Journals (Sweden)

    Yoshihiro Tsujimoto

    2012-03-01

    Full Text Available In this paper, we review recent progress and new challenges in the area of oxyfluoride perovskite, especially layered systems including Ruddlesden-Popper (RP, Dion-Jacobson (DJ and Aurivillius (AV type perovskite families. It is difficult to synthesize oxyfluoride perovskite using a conventional solid-state reaction because of the high chemical stability of the simple fluoride starting materials. Nevertheless, persistent efforts made by solid-state chemists have led to a major breakthrough in stabilizing such a mixed anion system. In particular, it is known that layered perovskite compounds exhibit a rich variety of O/F site occupation according to the synthesis used. We also present the synthetic strategies to further extend RP type perovskite compounds, with particular reference to newly synthesized oxyfluorides, Sr2CoO3F and Sr3Fe2O5+xF2−x (x ~ 0.44.

  9. Guest–host interaction in ferroelectric liquid crystal–nanoparticle

    Indian Academy of Sciences (India)

    Ferroelectric Cu-doped ZnO (Cu–ZnO) nanoparticles have been added to the pure ferroelectric liquid crystal (FLC) Felix 17/100. The nanoparticles are bigger in size as compared to FLC molecules; therefore, they distort the existing geometry of FLC matrix and set up an antiparallel correlation with the dipole moments of the ...

  10. Efficient Luminescence from Perovskite Quantum Dot Solids

    KAUST Repository

    Kim, Younghoon; Yassitepe, Emre; Voznyy, Oleksandr; Comin, Riccardo; Walters, Grant; Gong, Xiwen; Kanjanaboos, Pongsakorn; Nogueira, Ana F.; Sargent, Edward H.

    2015-01-01

    © 2015 American Chemical Society. Nanocrystals of CsPbX3 perovskites are promising materials for light-emitting optoelectronics because of their colloidal stability, optically tunable bandgap, bright photoluminescence, and excellent photoluminescence quantum yield. Despite their promise, nanocrystal-only films of CsPbX3 perovskites have not yet been fabricated; instead, highly insulating polymers have been relied upon to compensate for nanocrystals' unstable surfaces. We develop solution chemistry that enables single-step casting of perovskite nanocrystal films and overcomes problems in both perovskite quantum dot purification and film fabrication. Centrifugally cast films retain bright photoluminescence and achieve dense and homogeneous morphologies. The new materials offer a platform for optoelectronic applications of perovskite quantum dot solids.

  11. Efficient Luminescence from Perovskite Quantum Dot Solids

    KAUST Repository

    Kim, Younghoon

    2015-11-18

    © 2015 American Chemical Society. Nanocrystals of CsPbX3 perovskites are promising materials for light-emitting optoelectronics because of their colloidal stability, optically tunable bandgap, bright photoluminescence, and excellent photoluminescence quantum yield. Despite their promise, nanocrystal-only films of CsPbX3 perovskites have not yet been fabricated; instead, highly insulating polymers have been relied upon to compensate for nanocrystals\\' unstable surfaces. We develop solution chemistry that enables single-step casting of perovskite nanocrystal films and overcomes problems in both perovskite quantum dot purification and film fabrication. Centrifugally cast films retain bright photoluminescence and achieve dense and homogeneous morphologies. The new materials offer a platform for optoelectronic applications of perovskite quantum dot solids.

  12. Neutral- and Multi-Colored Semitransparent Perovskite Solar Cells.

    Science.gov (United States)

    Lee, Kyu-Tae; Guo, L Jay; Park, Hui Joon

    2016-04-11

    In this review, we summarize recent works on perovskite solar cells with neutral- and multi-colored semitransparency for building-integrated photovoltaics and tandem solar cells. The perovskite solar cells exploiting microstructured arrays of perovskite "islands" and transparent electrodes-the latter of which include thin metallic films, metal nanowires, carbon nanotubes, graphenes, and transparent conductive oxides for achieving optical transparency-are investigated. Moreover, the perovskite solar cells with distinctive color generation, which are enabled by engineering the band gap of the perovskite light-harvesting semiconductors with chemical management and integrating with photonic nanostructures, including microcavity, are discussed. We conclude by providing future research directions toward further performance improvements of the semitransparent perovskite solar cells.

  13. Development of High Efficiency Four-Terminal Perovskite-Silicon Tandems

    Science.gov (United States)

    Duong, The Duc

    This thesis is concerned with the development of high efficiency four-terminal perovskite-silicon tandem solar cells with the potential to reduce the cost of solar energy. The work focuses on perovskite top cells and can be divided into three main parts: developing low parasitic absorption and efficient semi-transparent perovskite cells, doping perovskite materials with rubidium, and optimizing perovskite material's bandgap with quadruple-cation and mixed-halide. A further section investigates the light stability of optimized bandgap perovskite cells. In a four-terminal mechanically stacked tandem, the perovskite top cell requires two transparent contacts at both the front and rear sides. Through detailed optical and electrical power loss analysis of the tandem efficiency due to non-ideal properties of the two transparent contacts, optimal contact parameters in term of sheet resistance and transparency are identified. Indium doped tin oxide by sputtering is used for both two transparent contacts and their deposition parameters are optimized separately. The semi-transparent perovskite cell using MAPbI3 has an efficiency of more than 12% with less than 12% parasitic absorption and up to 80% transparency in the long wavelength region. Using a textured foil as anti-reflection coating, an outstanding average transparency of 84% in the long wavelength is obtained. The low parasitic absorption allows an opaque version of the semi-transparent perovskite cell to operate efficiently in a filterless spectrum splitting perovskite-silicon tandem configuration. To further enhance the performance of perovskite cells, it is essential to improve the quality of perovskite films. This can be achieved with mixed-perovskite FAPbI3/MAPbBr3. However, mixed-perovskite films normally contain small a small amount of a non-perovskite phase, which is detrimental for the cell performance. Rb-doping is found to eliminate the formation of the non-perovskite phase and enhance the crystallinity of

  14. Concurrent transition of ferroelectric and magnetic ordering near room temperature.

    Science.gov (United States)

    Ko, Kyung-Tae; Jung, Min Hwa; He, Qing; Lee, Jin Hong; Woo, Chang Su; Chu, Kanghyun; Seidel, Jan; Jeon, Byung-Gu; Oh, Yoon Seok; Kim, Kee Hoon; Liang, Wen-I; Chen, Hsiang-Jung; Chu, Ying-Hao; Jeong, Yoon Hee; Ramesh, Ramamoorthy; Park, Jae-Hoon; Yang, Chan-Ho

    2011-11-29

    Strong spin-lattice coupling in condensed matter gives rise to intriguing physical phenomena such as colossal magnetoresistance and giant magnetoelectric effects. The phenomenological hallmark of such a strong spin-lattice coupling is the manifestation of a large anomaly in the crystal structure at the magnetic transition temperature. Here we report that the magnetic Néel temperature of the multiferroic compound BiFeO(3) is suppressed to around room temperature by heteroepitaxial misfit strain. Remarkably, the ferroelectric state undergoes a first-order transition to another ferroelectric state simultaneously with the magnetic transition temperature. Our findings provide a unique example of a concurrent magnetic and ferroelectric transition at the same temperature among proper ferroelectrics, taking a step toward room temperature magnetoelectric applications.

  15. On bistable states retention in ferroelectric Langmuir-Blodgett films

    Science.gov (United States)

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

    2003-08-01

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

  16. Switching Characteristics of Ferroelectric Transistor Inverters

    Science.gov (United States)

    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.

  17. High-accuracy determination for optical indicatrix rotation in ferroelectric DTGS

    OpenAIRE

    O.S.Kushnir; O.A.Bevz; O.G.Vlokh

    2000-01-01

    Optical indicatrix rotation in deuterated ferroelectric triglycine sulphate is studied with the high-accuracy null-polarimetric technique. The behaviour of the effect in ferroelectric phase is referred to quadratic spontaneous electrooptics.

  18. Photocatalysis: HI-time for perovskites

    DEFF Research Database (Denmark)

    Vesborg, Peter Christian Kjærgaard

    2017-01-01

    Organolead halide perovskite solar absorbers demonstrate high photovoltaic efficiencies but they are notorious for their intolerance to water. Now, methylammonium lead iodide perovskites are used to harvest solar energy — in water — via photocatalytic generation of hydrogen from solutions...

  19. The operational mechanism of ferroelectric-driven organic resistive switches

    NARCIS (Netherlands)

    Kemerink, M.; Asadi, K.; Blom, P.W.M.; Leeuw, D.M. de

    2012-01-01

    The availability of a reliable memory element is crucial for the fabrication of 'plastic' logic circuits. We use numerical simulations to show that the switching mechanism of ferroelectric-driven organic resistive switches is the stray field of the polarized ferroelectric phase. The stray field

  20. The operational mechanism of ferroelectric-driven organic resistive switches

    NARCIS (Netherlands)

    Kemerink, M.; Asadi, K. (Kamal); Blom, P.W.M.; Leeuw, de D.M.

    2012-01-01

    The availability of a reliable memory element is crucial for the fabrication of ‘plastic’ logic circuits. We use numerical simulations to show that the switching mechanism of ferroelectric-driven organic resistive switches is the stray field of the polarized ferroelectric phase. The stray field

  1. The operational mechanism of ferroelectric-driven organic resistive switches

    NARCIS (Netherlands)

    Kemerink, Martijn; Asadi, Kamal; Blom, Paul W. M.; de Leeuw, Dago M.

    The availability of a reliable memory element is crucial for the fabrication of 'plastic' logic circuits. We use numerical simulations to show that the switching mechanism of ferroelectric-driven organic resistive switches is the stray field of the polarized ferroelectric phase. The stray field

  2. Planar-integrated single-crystalline perovskite photodetectors

    KAUST Repository

    Saidaminov, Makhsud I.

    2015-11-09

    Hybrid perovskites are promising semiconductors for optoelectronic applications. However, they suffer from morphological disorder that limits their optoelectronic properties and, ultimately, device performance. Recently, perovskite single crystals have been shown to overcome this problem and exhibit impressive improvements: low trap density, low intrinsic carrier concentration, high mobility, and long diffusion length that outperform perovskite-based thin films. These characteristics make the material ideal for realizing photodetection that is simultaneously fast and sensitive; unfortunately, these macroscopic single crystals cannot be grown on a planar substrate, curtailing their potential for optoelectronic integration. Here we produce large-area planar-integrated films made up of large perovskite single crystals. These crystalline films exhibit mobility and diffusion length comparable with those of single crystals. Using this technique, we produced a high-performance light detector showing high gain (above 104 electrons per photon) and high gain-bandwidth product (above 108 Hz) relative to other perovskite-based optical sensors.

  3. Making and Breaking of Lead Halide Perovskites

    KAUST Repository

    Manser, Joseph S.

    2016-02-16

    A new front-runner has emerged in the field of next-generation photovoltaics. A unique class of materials, known as organic metal halide perovskites, bridges the gap between low-cost fabrication and exceptional device performance. These compounds can be processed at low temperature (typically in the range 80–150 °C) and readily self-assemble from the solution phase into high-quality semiconductor thin films. The low energetic barrier for crystal formation has mixed consequences. On one hand, it enables inexpensive processing and both optical and electronic tunability. The caveat, however, is that many as-formed lead halide perovskite thin films lack chemical and structural stability, undergoing rapid degradation in the presence of moisture or heat. To date, improvements in perovskite solar cell efficiency have resulted primarily from better control over thin film morphology, manipulation of the stoichiometry and chemistry of lead halide and alkylammonium halide precursors, and the choice of solvent treatment. Proper characterization and tuning of processing parameters can aid in rational optimization of perovskite devices. Likewise, gaining a comprehensive understanding of the degradation mechanism and identifying components of the perovskite structure that may be particularly susceptible to attack by moisture are vital to mitigate device degradation under operating conditions. This Account provides insight into the lifecycle of organic–inorganic lead halide perovskites, including (i) the nature of the precursor solution, (ii) formation of solid-state perovskite thin films and single crystals, and (iii) transformation of perovskites into hydrated phases upon exposure to moisture. In particular, spectroscopic and structural characterization techniques shed light on the thermally driven evolution of the perovskite structure. By tuning precursor stoichiometry and chemistry, and thus the lead halide charge-transfer complexes present in solution, crystallization

  4. Giant enhancement in the ferroelectric field effect using a polarization gradient

    Energy Technology Data Exchange (ETDEWEB)

    Gu, Zongquan [Department of Electrical and Computer Engineering, Drexel University, Philadelphia, Pennsylvania 19104 (United States); Islam, Mohammad A. [Department of Materials Science and Engineering, Drexel University, Philadelphia, Pennsylvania 19104 (United States); Department of Physics, State University of New York at Oswego, Oswego, New York 13126 (United States); Spanier, Jonathan E., E-mail: spanier@drexel.edu [Department of Electrical and Computer Engineering, Drexel University, Philadelphia, Pennsylvania 19104 (United States); Department of Materials Science and Engineering, Drexel University, Philadelphia, Pennsylvania 19104 (United States); Department of Physics, Drexel University, Philadelphia, Pennsylvania 19104 (United States)

    2015-10-19

    Coupling of switchable ferroelectric polarization with the carrier transport in an adjacent semiconductor enables a robust, non-volatile manipulation of the conductance in a host of low-dimensional systems, including the two-dimensional electron liquid that forms at the LaAlO{sub 3} (LAO)-SrTiO{sub 3} (STO) interface. However, strength of the gate-channel coupling is relatively weak, limited in part by the electrostatic potential difference across a ferroelectric gate. Here, through application of phenomenological Landau-Ginzburg-Devonshire theory and self-consistent Poisson-Schrödinger model calculations, we show how compositional grading of PbZr{sub 1−x}Ti{sub x}O{sub 3} ferroelectric gates enables a more than twenty-five-fold increase in the LAO/STO channel conductance on/off ratios. Incorporation of polarization gradients in ferroelectric gates can enable breakthrough performance of ferroelectric non-volatile memories.

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

    Science.gov (United States)

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

    2018-06-01

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

  6. Parity-Forbidden Transitions and Their Impact on the Optical Absorption Properties of Lead-Free Metal Halide Perovskites and Double Perovskites.

    Science.gov (United States)

    Meng, Weiwei; Wang, Xiaoming; Xiao, Zewen; Wang, Jianbo; Mitzi, David B; Yan, Yanfa

    2017-07-06

    Using density functional theory calculations, we analyze the optical absorption properties of lead (Pb)-free metal halide perovskites (AB 2+ X 3 ) and double perovskites (A 2 B + B 3+ X 6 ) (A = Cs or monovalent organic ion, B 2+ = non-Pb divalent metal, B + = monovalent metal, B 3+ = trivalent metal, X = halogen). We show that if B 2+ is not Sn or Ge, Pb-free metal halide perovskites exhibit poor optical absorptions because of their indirect band gap nature. Among the nine possible types of Pb-free metal halide double perovskites, six have direct band gaps. Of these six types, four show inversion symmetry-induced parity-forbidden or weak transitions between band edges, making them not ideal for thin-film solar cell applications. Only one type of Pb-free double perovskite shows optical absorption and electronic properties suitable for solar cell applications, namely, those with B + = In, Tl and B 3+ = Sb, Bi. Our results provide important insights for designing new metal halide perovskites and double perovskites for optoelectronic applications.

  7. Phase diagrams of ferroelectric nanocrystals strained by an elastic matrix

    Science.gov (United States)

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

    2018-01-01

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

  8. Depth resolved lattice-charge coupling in epitaxial BiFeO3 thin film

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Hyeon Jun; Lee, Sung Su; Kwak, Jeong Hun; Kim, Young-Min; Jeong, Hu Young; Borisevich, Albina Y.; Lee, Su Yong; Noh, Do Young; Kwon, Owoong; Kim, Yunseok; Jo, Ji Young

    2016-12-01

    For epitaxial films, a critical thickness (tc) can create a phenomenological interface between a strained bottom layer and a relaxed top layer. Here, we present an experimental report of how the tc in BiFeO3 thin films acts as a boundary to determine the crystalline phase, ferroelectricity, and piezoelectricity in 60 nm thick BiFeO3/SrRuO3/SrTiO3 substrate. We found larger Fe cation displacement of the relaxed layer than that of strained layer. In the time-resolved X-ray microdiffraction analyses, the piezoelectric response of the BiFeO3 film was resolved into a strained layer with an extremely low piezoelectric coefficient of 2.4 pm/V and a relaxed layer with a piezoelectric coefficient of 32 pm/V. The difference in the Fe displacements between the strained and relaxed layers is in good agreement with the differences in the piezoelectric coefficient due to the electromechanical coupling.

  9. Symmetry mismatch-driven perpendicular magnetic anisotropy for perovskite/brownmillerite heterostructures.

    Science.gov (United States)

    Zhang, Jing; Zhong, Zhicheng; Guan, Xiangxiang; Shen, Xi; Zhang, Jine; Han, Furong; Zhang, Hui; Zhang, Hongrui; Yan, Xi; Zhang, Qinghua; Gu, Lin; Hu, Fengxia; Yu, Richeng; Shen, Baogen; Sun, Jirong

    2018-05-15

    Grouping different transition metal oxides together by interface engineering is an important route toward emergent phenomenon. While most of the previous works focused on the interface effects in perovskite/perovskite heterostructures, here we reported on a symmetry mismatch-driven spin reorientation toward perpendicular magnetic anisotropy in perovskite/brownmillerite heterostructures, which is scarcely seen in tensile perovskite/perovskite heterostructures. We show that alternately stacking perovskite La 2/3 Sr 1/3 MnO 3 and brownmillerite LaCoO 2.5 causes a strong interface reconstruction due to symmetry discontinuity at interface: neighboring MnO 6 octahedra and CoO 4 tetrahedra at the perovskite/brownmillerite interface cooperatively relax in a manner that is unavailable for perovskite/perovskite interface, leading to distinct orbital reconstructions and thus the perpendicular magnetic anisotropy. Moreover, the perpendicular magnetic anisotropy is robust, with an anisotropy constant two orders of magnitude greater than the in-plane anisotropy of the perovskite/perovskite interface. The present work demonstrates the great potential of symmetry engineering in designing artificial materials on demand.

  10. High-Tc ferroelectrics and superconductors

    International Nuclear Information System (INIS)

    Muller, K.A.

    1990-01-01

    The meaning of the title refers to transition temperatures T c in ferroelectrics (FE) and superconductors (S). The highest T c 's in either field are observed in oxides: 1770 K in the ferroelectric La 2 TiO 7 and 125 K in the superconductor Tl 2 Ca 2 Cu 3 O 10 . Therefore, the question can be asked whether the observed high T c 's in oxide FE and S are a pure coincidence or whether there may be an underlying reason for it. This question is addressed first by recalling recent advances concerning anharmonic FE-properties and then by reviewing S-findings in the new compounds related to these properties

  11. Planar-integrated single-crystalline perovskite photodetectors

    KAUST Repository

    Saidaminov, Makhsud I.; Adinolfi, Valerio; Comin, Riccardo; Abdelhady, Ahmed L.; Peng, Wei; Dursun, Ibrahim; Yuan, Mingjian; Hoogland, Sjoerd; Sargent, Edward H.; Bakr, Osman

    2015-01-01

    Hybrid perovskites are promising semiconductors for optoelectronic applications. However, they suffer from morphological disorder that limits their optoelectronic properties and, ultimately, device performance. Recently, perovskite single crystals

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

    Science.gov (United States)

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

    2017-07-01

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

  13. Highly Efficient Spectrally Stable Red Perovskite Light-Emitting Diodes.

    Science.gov (United States)

    Tian, Yu; Zhou, Chenkun; Worku, Michael; Wang, Xi; Ling, Yichuan; Gao, Hanwei; Zhou, Yan; Miao, Yu; Guan, Jingjiao; Ma, Biwu

    2018-05-01

    Perovskite light-emitting diodes (LEDs) have recently attracted great research interest for their narrow emissions and solution processability. Remarkable progress has been achieved in green perovskite LEDs in recent years, but not blue or red ones. Here, highly efficient and spectrally stable red perovskite LEDs with quasi-2D perovskite/poly(ethylene oxide) (PEO) composite thin films as the light-emitting layer are reported. By controlling the molar ratios of organic salt (benzylammonium iodide) to inorganic salts (cesium iodide and lead iodide), luminescent quasi-2D perovskite thin films are obtained with tunable emission colors from red to deep red. The perovskite/polymer composite approach enables quasi-2D perovskite/PEO composite thin films to possess much higher photoluminescence quantum efficiencies and smoothness than their neat quasi-2D perovskite counterparts. Electrically driven LEDs with emissions peaked at 638, 664, 680, and 690 nm have been fabricated to exhibit high brightness and external quantum efficiencies (EQEs). For instance, the perovskite LED with an emission peaked at 680 nm exhibits a brightness of 1392 cd m -2 and an EQE of 6.23%. Moreover, exceptional electroluminescence spectral stability under continuous device operation has been achieved for these red perovskite LEDs. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Water-Induced Dimensionality Reduction in Metal-Halide Perovskites

    KAUST Repository

    Turedi, Bekir

    2018-03-30

    Metal-halide perovskite materials are highly attractive materials for optoelectronic applications. However, the instability of perovskite materials caused by moisture and heat-induced degradation impairs future prospects of using these materials. Here we employ water to directly transform films of the three-dimensional (3D) perovskite CsPbBr3 to stable two-dimensional (2D) perovskite-related CsPb2Br5. A sequential dissolution-recrystallization process governs this water induced transformation under PbBr2 rich condition. We find that these post-synthesized 2D perovskite-related material films exhibit excellent stability against humidity and high photoluminescence quantum yield. We believe that our results provide a new synthetic method to generate stable 2D perovskite-related materials that could be applicable for light emitting device applications.

  15. A thermally robust and thickness independent ferroelectric phase in laminated hafnium zirconium oxide

    Directory of Open Access Journals (Sweden)

    S. Riedel

    2016-09-01

    Full Text Available Ferroelectric properties in hafnium oxide based thin films have recovered the scaling potential for ferroelectric memories due to their ultra-thin-film- and CMOS-compatibility. However, the variety of physical phenomena connected to ferroelectricity allows a wider range of applications for these materials than ferroelectric memory. Especially mixed HfxZr1-xO2 thin films exhibit a broad compositional range of ferroelectric phase stability and provide the possibility to tailor material properties for multiple applications. Here it is shown that the limited thermal stability and thick-film capability of HfxZr1-xO2 can be overcome by a laminated approach using alumina interlayers.

  16. Origins and mechanisms of hysteresis in organometal halide perovskites

    Science.gov (United States)

    Li, Cheng; Guerrero, Antonio; Zhong, Yu; Huettner, Sven

    2017-05-01

    Inorganic-organic halide organometal perovskites, such as CH3NH3PbI3 and CsPbI3, etc, have been an unprecedented rising star in the field of photovoltaics since 2009, owing to their exceptionally high power conversion efficiency and simple fabrication processability. Despite its relatively short history of development, intensive investigations have been concentrating on this material; these have ranged from crystal structure analysis and photophysical characterization to performance optimization and device integration, etc. Yet, when applied in photovoltaic devices, this material suffers from hysteresis, that is, the difference of the current-voltage (I-V) curve during sweeping in two directions (from short-circuit towards open-circuit and vice versa). This behavior may significantly impede its large-scale commercial application. This Review will focus on the recent theoretical and experimental efforts to reveal the origin and mechanism of hysteresis. The proposed origins include (1) ferroelectric polarization, (2) charge trapping/detrapping, and (3) ion migration. Among them, recent evidence consistently supports the idea that ion migration plays a key role for the hysteretic behavior in perovskite solar cells (PSCs). Hence, this Review will summarize the recent results on ion migration such as the migrating ion species, activation energy measurement, capacitive characterization, and internal electrical field modulation, etc. In addition, this Review will also present the devices with alleviation/elimination of hysteresis by incorporating either large-size grains or phenyl-C61-butyric acid methyl ester molecules. In a different application, the hysteretic property has been utilized in photovoltaic and memristive switching devices. In sum, by examining these three possible mechanisms, it is concluded that the origin of hysteresis in PSCs is associated with a combination of effects, but mainly limited by ion/defect migration. This strong interaction between ion

  17. Epitaxial graphene electronic structure and transport

    International Nuclear Information System (INIS)

    De Heer, Walt A; Berger, Claire; Wu Xiaosong; Sprinkle, Mike; Hu Yike; Ruan Ming; First, Phillip N; Stroscio, Joseph A; Haddon, Robert; Piot, Benjamin; Faugeras, Clement; Potemski, Marek; Moon, Jeong-Sun

    2010-01-01

    Since its inception in 2001, the science and technology of epitaxial graphene on hexagonal silicon carbide has matured into a major international effort and is poised to become the first carbon electronics platform. A historical perspective is presented and the unique electronic properties of single and multilayered epitaxial graphenes on electronics grade silicon carbide are reviewed. Early results on transport and the field effect in Si-face grown graphene monolayers provided proof-of-principle demonstrations. Besides monolayer epitaxial graphene, attention is given to C-face grown multilayer graphene, which consists of electronically decoupled graphene sheets. Production, structure and electronic structure are reviewed. The electronic properties, interrogated using a wide variety of surface, electrical and optical probes, are discussed. An overview is given of recent developments of several device prototypes including resistance standards based on epitaxial graphene quantum Hall devices and new ultrahigh frequency analogue epitaxial graphene amplifiers.

  18. Ferroelectricity and Piezoelectricity in Free-Standing Polycrystalline Films of Plastic Crystals.

    Science.gov (United States)

    Harada, Jun; Yoneyama, Naho; Yokokura, Seiya; Takahashi, Yukihiro; Miura, Atsushi; Kitamura, Noboru; Inabe, Tamotsu

    2018-01-10

    Plastic crystals represent a unique compound class that is often encountered in molecules with globular structures. The highly symmetric cubic crystal structure of plastic crystals endows these materials with multiaxial ferroelectricity that allows a three-dimensional realignment of the polarization axes of the crystals, which cannot be achieved using conventional molecular ferroelectric crystals with low crystal symmetry. In this work, we focused our attention on malleability as another characteristic feature of plastic crystals. We have synthesized the new plastic/ferroelectric ionic crystals tetramethylammonium tetrachloroferrate(III) and tetramethylammonium bromotrichloroferrate(III), and discovered that free-standing translucent films can be easily prepared by pressing powdered samples of these compounds. The thus obtained polycrystalline films exhibit ferroelectric polarization switching and a relatively large piezoelectric response at room temperature. The ready availability of functional films demonstrates the practical utility of such plastic/ferroelectric crystals, and considering the vast variety of possible constituent cations and anions, a wide range of applications should be expected for these unique and attractive functional materials.

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

    Directory of Open Access Journals (Sweden)

    Jianyi Liu

    2014-09-01

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

  20. Fabrication of Semiconducting Methylammonium Lead Halide Perovskite Particles by Spray Technology

    Science.gov (United States)

    Ahmadian-Yazdi, Mohammad-Reza; Eslamian, Morteza

    2018-01-01

    In this "nano idea" paper, three concepts for the preparation of methylammonium lead halide perovskite particles are proposed, discussed, and tested. The first idea is based on the wet chemistry preparation of the perovskite particles, through the addition of the perovskite precursor solution to an anti-solvent to facilitate the precipitation of the perovskite particles in the solution. The second idea is based on the milling of a blend of the perovskite precursors in the dry form, in order to allow for the conversion of the precursors to the perovskite particles. The third idea is based on the atomization of the perovskite solution by a spray nozzle, introducing the spray droplets into a hot wall reactor, so as to prepare perovskite particles, using the droplet-to-particle spray approach (spray pyrolysis). Preliminary results show that the spray technology is the most successful method for the preparation of impurity-free perovskite particles and perovskite paste to deposit perovskite thin films. As a proof of concept, a perovskite solar cell with the paste prepared by the sprayed perovskite powder was successfully fabricated.