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R Mankowsky, A von Hoegen, M Först, A Cavalleri
We report on the demonstration of ultrafast optical reversal of the ferroelectric polarization in LiNbO_{3}. Rather than driving the ferroelectric mode directly, we couple to it indirectly by resonant excitation of an auxiliary high-frequency phonon mode with femtosecond midinfrared pulses. Because of strong anharmonic coupling between these modes, the atoms are directionally displaced along the ferroelectric mode and the polarization is transiently reversed, as revealed by time-resolved, phase-sensitive, second-harmonic generation...
May 12, 2017: Physical Review Letters
Phil Szuromi
No abstract text is available yet for this article.
May 26, 2017: Science
Sining Yun, Xiao Zhou, Jacky Even, Anders Hagfeldt
Hybrid halide perovskite solar cells (PSCs) exceeding 22% power conversion efficiencies (PCEs) have attracted considerable global attention due to the intrinsic nature of perovskite. Although we all know about that perovskite plays a significant role in the operation of PSCs, the fundamental theories associated with perovskite have not been resolved by the exponential increase in research effort. This raises questions about whether the first-principles calculations are sufficiently addressing the underlying issues in perovskite...
May 23, 2017: Angewandte Chemie
Ying Liu, Yinlian Zhu, Yunlong Tang, Yujia Wang, Yixiao Jiang, Yaobin Xu, Bin Zhang, Xiuliang Ma
Ferroelectrics hold promise for sensors, transducers, and telecommunications. With the demand of electronic devices scaling down, they take the form of nanoscale films. However, the polarizations in ultrathin ferroelectric films are usually reduced dramatically due to the depolarization field caused by incomplete charge screening at interfaces, hampering the integrations of ferroelectrics into electric devices. Here, we design and fabricate a ferroelectric/multiferroic BiFeO3/PbTiO3 system, which exhibits discontinuities in both chemical valence and ferroelectric polarization across the interface...
May 25, 2017: Nano Letters
Sen Zhang, Qianping Chen, Yan Liu, Aitian Chen, Lifeng Yang, Peisen Li, Zhou Shi Ming, Yi Yu, Wen Sun, Xiaozhong Zhang, Yuelei Zhao, Young Sun, Yonggang Zhao
Strain-mediated ferromagnetic/ferroelectric heterostructures have played an important role among the multiferroic materials to investigate the electric-field control of magnetism in the past decade, owing to their excellent performances such as room temperature operation and large magnetoelectric coupling effect. Due to the different ferroelectric-switching-originated strain behaviors and varied interfacial coupling effect, both loop-like (non-volatile) and butterfly-like (volatile) converse magnetoelectric effects have been reported...
May 25, 2017: ACS Applied Materials & Interfaces
Xiaofeng Yin, Xiaoning Li, Wen Gu, Fangfang Wang, Yijun Zou, Shujie Sun, Zhengping Fu, Yalin Lu
Ferroelectricity may promote the photocatalytic performance because carrier separation efficiency can be effectively improved by the internal electrostatic field caused by spontaneous polarization. Heterostructures which combine ferroelectric materials with other semiconductor materials can be further advantageous to the photocatalysis process. In this work, the Bi1.65Fe1.16Nb1.12O7 was hybridized with g-C3N4 via a facile low temperature method. The results of high resolution transmission electron microscopy (HRTEM) confirmed that the tight interface were formed between g-C3N4 and Bi1...
May 24, 2017: ACS Applied Materials & Interfaces
Martin Schmidbauer, Dorothee Braun, Toni Markurt, Michael Hanke, Jutta Schwarzkopf
A novel concept to obtain a ferroelectric material with enhanced piezoelectric properties is proposed. This approach is based on the combination of two pathways: (i) the evolution of a ferroelectric monoclinic phase and, (ii) the coexistence of different types of ferroelectric domains leading to polarization discontinuities at the domain walls. Each of these pathways enables polarization rotation in the material which is responsible for giant piezoelectricity. Targeted incorporation of anisotropic epitaxial lattice strain is used to implement this approach...
May 23, 2017: Nanotechnology
Ensieh Seyedhosseini, Konstantin Romanyuk, Daria Vasileva, Semen Vasilev, Alla Nuraeva, Pavel Zelenovskiy, Maxim S Ivanov, Anna N Morozovska, Vladimir Ya Shur, Haidong Lu, Alexei Gruverman, Andrei Leonidovitch Kholkin
Self-assembly of ferroelectric materials attracts significant interest because it offers a promising fabrication route to novel structures useful for microelectronic devices such as non-volatile memories, integrated sensors/actuators, or energy harvesters. In this work, we demonstrate a novel approach for self-assembly of organic ferroelectrics (as exemplified by ferroelectric β-glycine) using evaporative dewetting, which allows forming quasi-regular arrays of nano- and microislands with preferred orientation of polarization axes...
May 23, 2017: ACS Applied Materials & Interfaces
Ying-Hao Chu, Tahta Amrillah, Yugandhar Bitla, Kwangwoo Shin, Tiannan Yang, Ying-Hui Hsieh, Yu-You Chiou, Heng-Jui Liu, Thi Hien Do, Dong Su, Yi-Chun Chen, Shien-Uang Jen, Long-Qing Chen, Kee Hoon Kim, Jenh-Yih Juang
Magnetoelectric nanocomposites have been a topic of intense research due to their profound potential in the applications of electronic devices based on the spintronic technology. Nevertheless, in spite of significant progress made in the growth of high-quality nanocomposite thin films, the substrate clamping effect still remains as a major hurdle in realizing the ultimate magnetoelectric coupling. To overcome this obstacle, an alternative strategy of fabricating self-assembled ferroelectric-ferrimagnetic bulk heterojunction on flexible muscovite via the van der Waals epitaxy is adopted...
May 22, 2017: ACS Nano
Aleksey A Kudreyko, Nail G Migranov, Olga V Bachurina, Song Wanqing
Light transmittance of a short-pitch deformed-helix ferroelectric liquid crystal cell was numerically studied when low and high voltage frequencies ([Formula: see text] kHz and [Formula: see text] kHz, respectively) are applied to the cell. The reported finding in the decay of light transmittance at increasing frequency is obtained due to reasonable simplifications of the temporal dependence of director's azimuthal angle. By taking experimentally known data, we numerically demonstrate that the increase in temperature of ferroelectric liquid crystals yields an insignificant change of light transmittance within all visible spectra...
May 2017: European Physical Journal. E, Soft Matter
Wei-Wei Peng, Robert Tétot, Gang Niu, Emilie Amzallag, Bertrand Vilquin, Jean-Blaise Brubach, Pascale Roy
Due to the remarkable possibilities of epitaxially growing strontium titanate (SrTiO3 or STO) on silicon, this oxide is widely used as a buffer layer for integrating other perovskite oxides which allows for the development of various functional electronic devices on silicon. Moreover, STO is known to be an incipient ferroelectric in bulk but may become ferroelectric when in the form of strained ultrathin films. Given the importance of the potential applications for electronics if this property is demonstrated, we performed a spectroscopic study of STO on Si(001) templates coupling experimental and ab initio investigations...
May 19, 2017: Scientific Reports
Zhongnan Xi, Jieji Ruan, Chen Li, Chunyan Zheng, Zheng Wen, Jiyan Dai, Aidong Li, Di Wu
Recently, ferroelectric tunnel junctions have attracted much attention due to their potential applications in non-destructive readout non-volatile memories. Using a semiconductor electrode has been proven effective to enhance the tunnelling electroresistance in ferroelectric tunnel junctions. Here we report a systematic investigation on electroresistance of Pt/BaTiO3/Nb:SrTiO3 metal/ferroelectric/semiconductor tunnel junctions by engineering the Schottky barrier on Nb:SrTiO3 surface via varying BaTiO3 thickness and Nb doping concentration...
May 17, 2017: Nature Communications
Charlotte A L Dixon, Jason A McNulty, Steven Huband, Pamela A Thomas, Philip Lightfoot
The perovskite Li0.2Na0.8NbO3 is shown, by powder neutron diffraction, to display a unique sequence of phase transitions at elevated temperature. The ambient temperature polar phase (rhombohedral, space group R3c) transforms via a first-order transition to a polar tetragonal phase (space group P42mc) in the region 150-300°C; these two phases correspond to Glazer tilt systems a(-)a(-)a(-) and a(+)a(+)c(-), respectively. At 500°C a ferroelectric-paraelectric transition takes place from P42mc to P42/nmc, retaining the a(+)a(+)c(-) tilt...
May 1, 2017: IUCrJ
Brendan J Kennedy
The ferroelectric-paraelectric transition in Li0.2Na0.8NbO3 is between two extremely rare perovskite polytypes. How the unprecedented sequence of structures was established shows that even old oxides can play new tricks.
May 1, 2017: IUCrJ
Chang Jae Roh, Sun Young Hamh, Chang-Soo Woo, Kwang-Eun Kim, Chan-Ho Yang, Jong Seok Lee
We investigate the ferroelectric state of a tetragonal BiFeO3 thin film grown on a LaAlO3 (001) substrate using an optical second harmonic generation (SHG) microscope. Whereas the ferroelectric state of this material hosts nanometer-sized domains which again form micrometer-sized domains of four different configurations, we could figure out the characteristic features of each domain from the SHG mapping with various sizes of the probe beam, i.e., from 0.7 to 3.9 μm in its diameter. In particular, we demonstrate that a single micrometer-sized domain contributes to the SHG as a coherent summation of the constituent nanometer-sized domains, and multi-micrometer-sized domains contribute to the SHG as an incoherent summation of each micro-domain...
December 2017: Nanoscale Research Letters
Raymond G P McQuaid, Michael P Campbell, Roger W Whatmore, Amit Kumar, J Marty Gregg
Ferroelectric domain walls constitute a completely new class of sheet-like functional material. Moreover, since domain walls are generally writable, erasable and mobile, they could be useful in functionally agile devices: for example, creating and moving conducting walls could make or break electrical connections in new forms of reconfigurable nanocircuitry. However, significant challenges exist: site-specific injection and annihilation of planar walls, which show robust conductivity, has not been easy to achieve...
May 16, 2017: Nature Communications
Xiaoyu Wu, Urko Petralanda, Lu Zheng, Yuan Ren, Rongwei Hu, Sang-Wook Cheong, Sergey Artyukhin, Keji Lai
Domain walls (DWs) in ferroic materials, across which the order parameter abruptly changes its orientation, can host emergent properties that are absent in the bulk domains. Using a broadband (10(6) to 10(10) Hz) scanning impedance microscope, we show that the electrical response of the interlocked antiphase boundaries and ferroelectric DWs in hexagonal rare-earth manganites (h-RMnO3) is dominated by the bound-charge oscillation rather than free-carrier conduction at the DWs. As a measure of the rate of energy dissipation, the effective conductivity of DWs on the (001) surfaces of h-RMnO3 at gigahertz frequencies is drastically higher than that at dc, whereas the effect is absent on surfaces with in-plane polarized domains...
May 2017: Science Advances
Qinglin Deng, Mengjiao Li, Junyong Wang, Peng Zhang, Kai Jiang, Jinzhong Zhang, Zhigao Hu, Junhao Chu
Two-dimensional layered K4Nb6O17 (KN) was easily formed as a secondary phase caused by the volatilization of alkali metal ions, when preparing ferroelectric K x Na1-x NbO3 based ceramics and films. In this work, it was believed that KN film is with weak ferroelectricity and has a little effect on the ferroelectric properties of K x Na1-x NbO3 based films. Moreover, temperature dependent (77-500 K) dielectric functions of KN film have been firstly extracted by fitting ellipsometric spectra with the Adachi dielectric function model and a four-phase layered model...
May 15, 2017: Scientific Reports
Fangping Zhuo, Qiang Li, Jinghan Gao, Qingfeng Yan, Yiling Zhang, Xiaoqing Xi, Xiangcheng Chu
(Pb,La)(Zr,Sn,Ti)O3 (PLZST) single crystals with their chemical composition located at the tetragonal antiferroelectric region are grown via the flux method in a PbO-PbF2-B2O3 mixture. Segregation of the Ti(4+) component in the as-grown crystals is observed due to the strong affinity between the oxygen anion and Ti(4+) ions. The critical electric field of the antiferroelectric to ferroelectric phase transition is determined to be about 0.5 kV mm(-1). The electric field induced ferroelectric phase transforms back into the antiferroelectric phase at a depolarization temperature of 125 °C...
May 15, 2017: Physical Chemistry Chemical Physics: PCCP
Shradhanjali Sahoo, T R Ravindran, Sharat Chandra, R M Sarguna, B K Das, T N Sairam, V Sivasubramanian, C Thirmal, P Murugavel
Diisopropylammonium bromide (DIPAB) can be crystallized either in an orthorhombic (P212121) or in a monoclinic (P21) structure at room temperature depending on synthesis conditions. The non-polar orthorhombic structure exhibits a subtle, irreversible transformation into the ferroelectric monoclinic-II (m-II) phase above ~421K. At a slightly higher temperature of 426K this m-II (P21) phase reversibly transforms into a disordered, paraelectric monoclinic-I (P21/m) structure. We synthesized DIPAB in the orthorhombic structure, heated it to obtain the m-II phase and carried out a systematic study of their Raman and IR spectra...
May 5, 2017: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
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