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Zhen Zhou, Jin Luo, Wei Sun, Jing-Feng Li
Extensive studies on (Bi0.5Na0.5)TiO3-BaTiO3 piezoceramics have aroused growing interest in developing high-performance piezoelectric films based on this promising lead-free piezoelectric system. High quality (1 - x%) (Bi0.5Na0.5)TiO3-x% BaTiO3 (x = 0-15) thin films were synthesized on Pt(111)/Ti/SiO2/Si(100) substrates via a sol-gel method. The phase transitions as functions of composition and temperature were investigated by X-ray diffraction (XRD) and temperature-dependent Raman spectra analysis. A morphotropic phase boundary (MPB) located at 5 ≤ x ≤ 10 was found in the films, being identical to that in bulk materials...
July 19, 2017: Physical Chemistry Chemical Physics: PCCP
Song Mi Lee, Sung-Ho Shin, Junghyo Nah, Min Hyung Lee
Appropriate control of energy band bending at the interface between semiconductors and electrolytes are closely related to performance of photoelectrochemical (PEC) water splitting. Dipoles formed near the surface of semiconductors induces energy band bending at the interface. Energy band bending control has been demonstrated by employing charged molecules and piezoelectric materials. However, chemical and piezoelectric approaches have demerit of chemical instability and inducement of instantaneous dipole, respectively...
July 19, 2017: Nanotechnology
Wan-Ying Zhang, Yuan-Yuan Tang, Peng-Fei Li, Ping-Ping Shi, Wei-Qiang Liao, Da-Wei Fu, Heng-Yun Ye, Yi Zhang, Ren-Gen Xiong
With the flourishing development of (CH3NH3)PbI3, three-dimensional (3D) organic-inorganic perovskites with unique structure-property flexibility have become a worldwide focus. However, they still face great challenges in effec-tively inducing ferroelectricity. Despite the typical 3D perovskite structure and the ability of dabco to trigger phase transition, unfortunately [H2dabco]RbCl3 (dabco = 1,4-diazabicyclo[2.2.2]octane) adopts a nonpolar crystal structure without ferroelectricity. Within larger RbI3 framework, we assemble N-methyl-dabco gained by reducing the molecular symmetry of dabco into a new 3D organic-inorganic perovskite...
July 18, 2017: Journal of the American Chemical Society
Junhua Luo, Lina Li, Zhihua Sun, Peng Wang, Weida Hu, Sasa Wang, Chengmin Ji, Maochun Hong
Two-dimensional (2D) layered hybrid perovskites have shown great potentials in optoelectronics. However, although great efforts have been made, 2D hybrid perovskite ferroelectrics remain rare. Here, we constructed the first ferroelectric with 2D multilayered perovskite framework, (C4H9NH3)2(CH3NH3)2Pb3Br10 (1), by tailored alloying mixed-organic-cations into the prototype of CH3NH3PbBr3. For the first time, concrete ferroelectricity was created by molecular reorientation and synergic ordering of organic cations, which is unprecedented for the known 2D hybrid perovskites...
July 18, 2017: Angewandte Chemie
O García-Zaldívar, T Escamilla-Díaz, M Ramírez-Cardona, M A Hernández-Landaverde, R Ramírez-Bon, J M Yañez-Limón, F Calderón-Piñar
The stabilization of δ-phase of poly(vinylidene fluoride) PVDF in a 14 µm-thickness ferroelectric membrane is achieved by a simple route based on the use of a dimethylformamide (DMF)/acetone solvent, in which the application of external electric field is not required. X-ray diffraction and calorimetric experiments on heating reveal that, at 154 °C, the original mixture between ferroelectric δ-phase and paraelectric α-phase transits to a system with only this latter phase in the crystalline fraction. A gradual and slight increment of amorphous fraction up to the melting at 161 °C is also observed...
July 17, 2017: Scientific Reports
Amit Choudhary, Ambika Bawa, Rajesh, Surinder P Singh, Ashok M Biradar
The fluctuations of unwound helical structure have been observed in deformed helix ferroelectric liquid crystal (DHFLC) and conventional FLC sample cells. The helix is partially unwound by strong anchoring on the substrates. In such sample cells, the helical decarlization lines are not observed in the texture under crossed polarized microscope. The dielectric spectroscopy is employed to observe the behavior of dielectric relaxation processes in these sample cells. A dielectric relaxation process is observed at a lower frequency than the Goldstone mode processes in DHFLC and FLC, which we call partially unwound helical mode (p-UHM)...
June 2017: Physical Review. E
S V Ulyanov
The correlation function of the director fluctuations in a free-standing smectic ferroelectric film is calculated theoretically. In the functional of free energy, the anisotropy of the Coulomb interaction of polarization charges is taken into account. The results of calculations were used to obtain the angular dependences of scattered light intensity. It has been shown that for relatively thick films, the anisotropy of the Coulomb interaction of polarization charges can change significantly the scattered light intensity...
June 2017: Physical Review. E
Steven J Brewer, Cory D Cress, Samuel C Williams, Hanhan Zhou, Manuel Rivas, Ryan Q Rudy, Ronald G Polcawich, Evan R Glaser, Jacob L Jones, Nazanin Bassiri-Gharb
The ability to tailor the performance of functional materials, such as semiconductors, via careful manipulation of defects has led to extraordinary advances in microelectronics. Functional metal oxides are no exception - protonic-defect-conducting oxides find use in solid oxide fuel cells (SOFCs) and oxygen-deficient high-temperature superconductors are poised for power transmission and magnetic imaging applications. Similarly, the advantageous functional responses in ferroelectric materials that make them attractive for use in microelectromechanical systems (MEMS), logic elements, and environmental energy harvesting, are derived from interactions of defects with other defects (such as domain walls) and with the lattice...
July 13, 2017: Scientific Reports
Gabriele D'Avino, Manuel Souto, Matteo Masino, Jonas K H Fischer, Imma Ratera, Xavier Fontrodona, Gianluca Giovannetti, Matthieu J Verstraete, Anna Painelli, Peter Lunkenheimer, Jaume Veciana, Alberto Girlando
No abstract text is available yet for this article.
July 12, 2017: Nature
Laura E Abramiuc, Liviu C Tănase, Alexei Barinov, Nicoleta G Apostol, Cristina Chirilă, Lucian Trupină, Lucian Pintilie, Cristian M Teodorescu
The stability of thin films of lead zirco-titanate (PZT) under intense soft X-ray beams is investigated by time-resolved photoelectron spectromicroscopy with a lateral resolution below 1 micrometer. Surface dissociation is observed when samples are irradiated with intense (5 × 10(23) photons per s per m(2)) soft X-rays, with promotion of reduced lead on the surface. On areas exhibiting outwards polarization (P((+))), the reduced lead is formed at the expense of P((+))-PZT. On areas presenting co-existing P((+)) states with areas without out-of-plane polarization (P((0))), the reduced lead is formed at the expense of the P((0))-PZT component, while the P((+))-PZT remains constant...
July 12, 2017: Nanoscale
Tomoaki Yamada, Daisuke Ito, Tomas Sluka, Osami Sakata, Hidenori Tanaka, Hiroshi Funakubo, Takahiro Namazu, Naoki Wakiya, Masahito Yoshino, Takanori Nagasaki, Nava Setter
Strain engineering is a widespread strategy used to enhance performance of devices based on semiconductor thin films. In ferroelectrics strain engineering is used to control the domain pattern: When an epitaxial film is biaxially compressed, e.g. due to lattice mismatch with the substrate, the film displays out-of-plane, often strongly enhanced polarization, while stretching the film on the substrate results in in-plane polarization. However, this strategy is of a limited applicability in nanorods because of the small rod/substrate contact area...
July 12, 2017: Scientific Reports
Bao-Wen Li, Minoru Osada, Yoon-Hyun Kim, Yasuo Ebina, Kosho Akatsuka, Takayoshi Sasaki
Complex perovskite oxides offer tremendous potential for controlling their rich variety of electronic properties including high-TC superconductivity, high- ferroelectricity, and quantum magnetism. Atomic-scale control of these intriguing properties in ultrathin perovskites is an important challenge for exploring new physics and device functionality at atomic dimensions. Here, we demonstrate atomic-scale engineering of dielectric responses using two-dimensional (2D) homologous perovskite nanosheets (Ca2Nam-3NbmO3m+1; m = 3-6)...
July 12, 2017: Journal of the American Chemical Society
Ji Zhang, Wei Sun, Jiangtao Zhao, Lei Sun, Lei Li, Xue-Jun Yan, Ke Wang, Zheng-Bin Gu, Zhen-Lin Luo, Yanbin Chen, Guo-Liang Yuan, Ming-Hui Lu, Shan-Tao Zhang
Thin films of 0.85BiFe1-2xTixMgxO3-0.15CaTiO3 (x = 0.1 and 0.2, abbreviated to C-1 and C-2, respectively) have been fabricated on (001) SrTiO3 substrate with and without a conductive La0.7Sr0.3MnO3 buffer layer. The X-ray θ-2θ and ϕ scans, atomic force microscopy, and cross-sectional transmission electron microscopy confirm the (001) epitaxial nature of the thin films with very high growth quality. Both the C-1 and C-2 thin films show well-shaped magnetization-magnetic field hysteresis at room temperature, with enhanced switchable magnetization values of 145...
July 19, 2017: ACS Applied Materials & Interfaces
Simone Fabiano, Negar Sani, Jun Kawahara, Loïg Kergoat, Josefin Nissa, Isak Engquist, Xavier Crispin, Magnus Berggren
Poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) is an organic mixed ion-electron conducting polymer. The PEDOT phase transports holes and is redox-active, whereas the PSS phase transports ions. When PEDOT is redox-switched between its semiconducting and conducting state, the electronic and optical properties of its bulk are controlled. Therefore, it is appealing to use this transition in electrochemical devices and to integrate those into large-scale circuits, such as display or memory matrices...
June 2017: Science Advances
Claudio Cazorla, Oswaldo Diéguez, Jorge Íñiguez
Spin-phonon interactions are central to many interesting phenomena, ranging from superconductivity to magnetoelectric effects. However, they are believed to have a negligible influence on the structural behavior of most materials. For example, magnetic perovskite oxides often undergo structural transitions accompanied by magnetic signatures whose minuteness suggests that the underlying spin-phonon couplings are largely irrelevant. We present an exception to this rule, showing that novel effects can occur as a consequence...
June 2017: Science Advances
Qiang Zhao, Hanlin Wang, Zhenjie Ni, Jie Liu, Yonggang Zhen, Xiaotao Zhang, Lang Jiang, Rongjin Li, Huanli Dong, Wenping Hu
Organic electronics based on poly(vinylidenefluoride/trifluoroethylene) (P(VDF-TrFE)) dielectric is facing great challenges in flexible circuits. As one indispensable part of integrated circuits, there is an urgent demand for low-cost and easy-fabrication nonvolatile memory devices. A breakthrough is made on a novel ferroelectric random access memory cell (1T1T FeRAM cell) consisting of one selection transistor and one ferroelectric memory transistor in order to overcome the half-selection problem. Unlike complicated manufacturing using multiple dielectrics, this system simplifies 1T1T FeRAM cell fabrication using one common dielectric...
July 10, 2017: Advanced Materials
Cong Lu, Chisato Temba, Nobuo Nakajima, Shuhei Kawakami, Naoki Ishimatsu, Hiroshi Maruyama
X-ray absorption spectra at the Ti <i>K</i>-edge of a SrTiO<sub>3</sub> single crystal under uniaxial pressure were measured to obtain evidence of uniaxial pressure-induced polarization predicted in SrTiO<sub>3</sub> from the electronic viewpoint. The pre-edge 3<i>d</i>-<i>e</i><sub>g</sub> peak decreases in intensity with increasing uniaxial pressure, together with an energy shift to higher energy side. Contrary to uniaxial deformation, these changes were independent of incident X-ray polarization...
July 10, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Felicia A McGuire, Yuh-Chen Lin, Katherine Price, G Bruce Rayner, Sourabh Khandelwal, Sayeef Salahuddin, Aaron D Franklin
It has been shown that a ferroelectric material integrated into the gate stack of a transistor can create an effective negative capacitance (NC) that allows the device to overcome "Boltzmann tyranny". While this switching below the thermal limit has been observed with Si-based NC field-effect transistors (NC-FETs), the adaptation to 2D materials would enable a device that is scalable in operating voltage as well as size. In this work, we demonstrate sustained sub-60 mV/dec switching, with a minimum subthreshold swing (SS) of 6...
July 12, 2017: Nano Letters
Pankaj Sharma, Qi Zhang, Daniel Sando, Chi Hou Lei, Yunya Liu, Jiangyu Li, Valanoor Nagarajan, Jan Seidel
Ferroelectric domain walls are atomically sharp topological defects that separate regions of uniform polarization. The discovery of electrical conductivity in specific types of walls gave rise to "domain wall nanoelectronics," a technology in which the wall (rather than the domain) stores information. This paradigm shift critically hinges on precise nanoengineering of reconfigurable domain walls. Using specially designed nanofabricated electrodes and scanning probe techniques, we demonstrate a prototype nonvolatile ferroelectric domain wall memory, scalable to below 100 nm, whose binary state is defined by the existence or absence of conductive walls...
June 2017: Science Advances
Nouamane Laanait, Wittawat Saenrang, Hua Zhou, Chang-Beom Eom, Zhan Zhang
X-ray diffraction imaging is rapidly emerging as a powerful technique by which one can capture the local structure of crystalline materials at the nano- and meso-scale. Here, we present investigations of the dynamic structure of epitaxial monodomain BiFeO3 thin-films using a novel full-field Bragg diffraction imaging modality. By taking advantage of the depth penetration of hard X-rays and their exquisite sensitivity to the atomic structure, we imaged in situ and in operando, the electric field-driven structural responses of buried BiFeO3 epitaxial thin-films in micro-capacitor devices, with sub-100 nm lateral resolution...
2017: Advanced Structural and Chemical Imaging
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