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Maciej Ptak, Mirosław Mączka, Anna Gągor, Adam Sieradzki, Bartosz Bondzior, Przemysław Dereń, S Pawlus
We report the synthesis, crystal structure, dielectric, vibrational and emission spectra of heterometallic MOFs, [C2H5NH3][Na0.5Cr0.5(HCOO)3] (EtANaCr), [C2H5NH3][Na0.5Al0.5(HCOO)3] (EtANaAl) and [C2H5NH3][Na0.5Al0.475Cr0.025(HCOO)3] (EtANaAlCr). These compounds crystallize in non-centrosymmetric monoclinic polar structures (space group Pn) and undergo order-disorder phase transitions upon heating to the monoclinic centrosymmetric structure (space group P21/n) at 369 (EtANaAl) and 373 K (EtANaCr). In principle, they are ferroelectric below these temperatures...
October 18, 2016: Physical Chemistry Chemical Physics: PCCP
Deepa Singh, Deepak, Ashish Garg
In this manuscript, we study the combined effect of mechanical strain and electric field cycling on the ferroelectric properties and polarization fatigue of P(VDF-TrFE) based flexible thin film capacitors from the perspective of flexible memory applications. The devices show nearly 80% retention of ferroelectric polarization after 30 000 bending cycles at mechanical strains of up to ca. 0.8%, mimicking a typical number of bending cycles a product is expected to go through. On the other hand, electric field cycling of the unstrained as well as mechanically strained devices results in over 50% drop in the ferroelectric polarization of the capacitors within 10(5) bipolar switching cycles...
October 17, 2016: Physical Chemistry Chemical Physics: PCCP
Menghao Wu, Shuai Dong, Kailun Yao, Jun-Ming Liu, Xiao Cheng Zeng
Realization of ferroelectric semiconductors by conjoining ferroelectricity with semiconductors remain a challenging task because most present-day ferroelectric materials are unsuitable for such a combination due to their wide bandgaps. Herein we show first-principles evidence towards the realization of a new class of 2D ferroelectric semiconductors through covalent functionalization of many prevailing 2D materials. Members in this new class of 2D ferroelectric semiconductors include covalently functionalized germanene, and stanene (Nat...
October 14, 2016: Nano Letters
Liviu Cristian Tănase, Nicoleta Georgiana Apostol, Laura Elena Abramiuc, Cristian Alexandru Tache, Luminița Hrib, Lucian Trupină, Lucian Pintilie, Cristian Mihail Teodorescu
Atomically clean lead zirco-titanate PbZr0.2Ti0.8O3 (001) layers exhibit a polarization oriented inwards P((-)), visible by a band bending of all core levels towards lower binding energies, whereas as introduced layers exhibit P((+)) polarization under air or in ultrahigh vacuum. The magnitude of the inwards polarization decreases when the temperature is increased at 700 K. CO adsorption on P((-)) polarized surfaces saturates at about one quarter of a monolayer of carbon, and occurs in both molecular (oxidized) and dissociated (reduced) states of carbon, with a large majority of reduced state...
October 14, 2016: Scientific Reports
Ran Su, Dawei Zhang, Yang Liu, Jiangbo Lu, Zhipeng Wang, Linglong Li, Jihong Bian, Ming Wu, Xiaojie Lou, Yaodong Yang
A giant electrocaloric effect (ECE) can be achieved in ferroelectric thin films, which demonstrates the applications of thin films in alternative cooling. However, electrocaloric thin films fabricated by conventional techniques, such as the pulsed laser deposition or sol-gel methods, may be limited by high costs, low yield and their dependence on substrates. In this study, we present a new bottom-up strategy to construct electrocaloric Ba0.8Sr0.2TiO3 thin films by assembling precisely designed building blocks of ferroelectric nanocubes, which is supported by detailed structural characterization...
October 14, 2016: Physical Chemistry Chemical Physics: PCCP
Tikhon Vergentev, Iurii Bronwald, Dmitry Chernyshov, Semen Gorfman, Stephanie H M Ryding, Paul Thompson, Robert J Cernik
Synchrotron X-rays on the Swiss Norwegian Beamline and BM28 (XMaS) at the ESRF have been used to record the diffraction response of the PMN-PT relaxor piezoelectric 67% Pb(Mg1/3Nb2/3)O3-33% PbTiO3 as a function of externally applied electric field. A DC field in the range 0-18 kV cm(-1) was applied along the [001] pseudo-cubic direction using a specially designed sample cell for in situ single-crystal diffraction experiments. The cell allowed data to be collected on a Pilatus 2M area detector in a large volume of reciprocal space using transmission geometry...
October 1, 2016: Journal of Applied Crystallography
Takahiro Shimada, Tao Xu, Yoshitaka Uratani, Jie Wang, Takayuki Kitamura
Unconventional phases and their transitions in nanoscale systems are recognized as an intriguing avenue for both unique physical properties and novel technological paradigms. Although the multiferroic phase has attracted considerable attention due to the coexistence and cross-coupling of electric and magnetic order parameters, mutually exclusive mechanism between ferroelectricity and ferromagnetism leaves conventional ferroelectrics such as PbTiO3 simply nonmagnetic. Here, we demonstrate from first principles that ultrathin PbTiO3 nanowires exhibit unconventional multiferroic phases with emerging ferromagnetism and coexisting ferroelectric/ferrotoroidic ordering...
October 13, 2016: Nano Letters
Yaojin Wang, Lijun Chen, Guoliang Yuan, Haosu Luo, Jiefang Li, D Viehland
The new generation of ternary Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 ferroelectric single crystals have potential applications in high power devices due to their surperior operational stability relative to the binary system. In this work, a reversible, large electric field induced strain of over 0.9% at room temperature, and in particular over 0.6% above 380 K was obtained. The polarization rotation path and the phase transition sequence of different compositions in these ternary systems have been determined with increasing electric field applied along [001] direction based on x-ray diffraction data...
October 13, 2016: Scientific Reports
Magdalena Owczarek, Karl A Hujsak, Daniel P Ferris, Aleksandrs Prokofjevs, Irena Majerz, Przemysław Szklarz, Huacheng Zhang, Amy A Sarjeant, Charlotte L Stern, Ryszard Jakubas, Seungbum Hong, Vinayak P Dravid, J Fraser Stoddart
Flexible organic materials possessing useful electrical properties, such as ferroelectricity, are of crucial importance in the engineering of electronic devices. Up until now, however, only ferroelectric polymers have intrinsically met this flexibility requirement, leaving small-molecule organic ferroelectrics with room for improvement. Since both flexibility and ferroelectricity are rare properties on their own, combining them in one crystalline organic material is challenging. Herein, we report that trisubstituted haloimidazoles not only display ferroelectricity and piezoelectricity-the properties that originate from their non-centrosymmetric crystal lattice-but also lend their crystalline mechanical properties to fine-tuning in a controllable manner by disrupting the weak halogen bonds between the molecules...
October 13, 2016: Nature Communications
Xin Chen, Shi Pan, Pei-Jian Feng, Huafeng Bian, Xu Han, Jia-Hao Liu, Xu Guo, Dongzhong Chen, Haixiong Ge, Qun-Dong Shen
A bioinspired photodetector with signal transmissible to neuron cells is fabricated. Photoisomerization of the dye molecules embedded in the ferroelectric polymer membrane achieves electric polarization change under visible light. The photodetector realizes high sensitivity, color recognition, transient response, and 3D visual detection with resolution of 25 000 PPI, and, impressively, directly transduces the signal to neuron cells.
October 12, 2016: Advanced Materials
Anton V Ievlev, Petro Maksymovych, Morgan Trassin, Jan Seidel, Ramamoorthy Ramesh, Sergei V Kalinin, Olga S Ovchinnikova
Domain formation and ferroelectric switching is fundamentally inseparable from polarization screening, which on free surfaces can be realized via band bending and ionic adsorption. In the latter case, polarization switching is intrinsically coupled to the surface electrochemical phenomena, and the electrochemical stage can control kinetics and induce long-range interactions. However, despite extensive evidence towards the critical role of surface electrochemistry, little is known about the nature of the associated processes...
October 11, 2016: ACS Applied Materials & Interfaces
Y B Xu, Y L Tang, Y L Zhu, Y Liu, S Li, S R Zhang, X L Ma
Ferroelectric thin films grown on high index substrates show unusual structural and switching dynamics due to their special strain states. Understanding the misfit relaxation behavior is crucial to facilitate the high index thin film growth with improved quality. In this paper, ferroelectric PbTiO3 thin films were grown on LaAlO3 (111) substrates by pulsed laser deposition technique. The microstructures were investigated by combinations of conventional and aberration-corrected transmission electron microscopy...
October 11, 2016: Scientific Reports
Andrew J Yost, Artem Pimachev, Chun-Chih Ho, Seth B Darling, Leeyih Wang, Wei-Fang Su, Yuri Dahnovsky, TeYu Chien
Scanning tunneling microscopy is utilized to investigate the local density of states of a CH3NH3PbI3-xClx perovskite in cross-sectional geometry. Two electronic phases, 10-20 nm in size, with different electronic properties inside the CH3NH3PbI3-xClx perovskite layer are observed by the dI/dV mapping and point spectra. A power law dependence of the dI/dV point spectra is revealed. In addition, the distinct electronic phases are found to have preferential orientations close to the normal direction of the film surface...
October 10, 2016: ACS Applied Materials & Interfaces
Sahar Saremi, Ruijuan Xu, Liv R Dedon, Julia A Mundy, Shang-Lin Hsu, Zuhuang Chen, Anoop R Damodaran, Scott P Chapman, Joseph T Evans, Lane W Martin
A novel approach to on-demand improvement of electronic properties in complex-oxide ferroelectrics is demonstrated whereby ion bombardment - commonly used in classic semiconductor materials - is applied to the PbTiO3 system. The result is deterministic reduction in leakage currents by 5 orders of magnitude, improved ferroelectric switching, and unprecedented insights into the nature of defects and intergap state evolution in these materials.
October 10, 2016: Advanced Materials
Takahiro Shimada, Le Van Lich, Koyo Nagano, Jian-Shan Wang, Jie Wang, Takayuki Kitamura
Topological objects of nontrivial spin or dipolar field textures, such as skyrmions, merons, and vortices, interacting with applied external fields in ferroic materials are of great scientific interest as an intriguing playground of unique physical phenomena and novel technological paradigms. The quest for new topological configurations of such swirling field textures has primarily been done for magnets with Dzyaloshinskii-Moriya interactions, while the absence of such intrinsic chiral interactions among electric dipoles left ferroelectrics aside in this quest...
October 7, 2016: Scientific Reports
L Yang, X Li, M F Liu, P L Li, Z B Yan, M Zeng, M H Qin, X S Gao, J-M Liu
The magnetically induced electric polarization behaviors in multiferroic TmMn2O5 in response to varying temperature and magnetic field are carefully investigated by means of a series of characterizations including the high precision pyroelectric current technique. Here polycrystalline rather than single crystal samples are used for avoiding the strong electrically self-polarized effect in single crystals, and various parallel experiments on excluding the thermally excited current contributions are performed...
October 7, 2016: Scientific Reports
Zheng Li, Jing Ma, Zhipeng Gao, Giuseppe Viola, Vladimir Koval, Amit Mahajan, Xuan Li, Chenglong Jia, Cewen Nan, Haixue Yan
Spark plasma sintering was employed in order to obtain textured Aurivillius phase ceramics that simultaneously exhibit ferroelectric and ferromagnetic properties at room temperature. The sintered multiferroics are layer-structured, nearly single-phase materials. Although a small amount of the secondary phase consisting of magnetic Co and Fe was detected by SEM/EDX, a majority of the observed ferromagnetic behaviour was attributed to the Aurivillius phase Bi4.25La0.75Ti3Fe0.5Co0.5O15 based on the observed magnetic anisotropy...
September 13, 2016: Dalton Transactions: An International Journal of Inorganic Chemistry
Hongli Guo, Wissam A Saidi, Jin Zhao
The two-dimensional electron gas (2DEG) formed at the interface between two insulating materials LaAlO3 (LAO) and SrTiO3 (STO) has recently generated a lot of interest. Here, based on first-principles density functional theory calculations, we investigate the existence and stability of the 2DEG under the application of a biaxial strain on the LAO/STO(001) heterostructure. The compressive strain induces ferroelectric (FE) polarization in STO, which allows for the tunability of the 2DEG by reversing the STO polarization orientation...
October 5, 2016: Physical Chemistry Chemical Physics: PCCP
Mandar M Shirolkar, Xiaolei Dong, Jieni Li, Shiliu Yin, Ming Li, Haiqian Wang
Particle size significantly affects the properties and therefore the potential applications of multiferroics. However, is there special particle size effect in BiFeO3, which has a spiral modulated spin structure? This is still under investigation for sub-5 nm BiFeO3. In this report, the structural, electronic and magnetic properties are investigated for chemically synthesized BiFeO3 nanoparticles with an average size of 3 nm. We observed nanotwinning features in the specific size regime of the nanoparticles (2-4 nm)...
September 14, 2016: Physical Chemistry Chemical Physics: PCCP
Meng Su, Zhenyu Yang, Lei Liao, Xuming Zou, Johnny C Ho, Jingli Wang, Jianlu Wang, Weida Hu, Xiangheng Xiao, Changzhong Jiang, Chuansheng Liu, Tailiang Guo
A new type of ferroelectric FET based on the single nanowire is demonstrated. The design of the side-gated architecture not only simplifies the manufacturing process but also avoids any postdeposition damage to the organic ferroelectric film. The devices exhibit excellent performances for nonvolatile memory applications, and the memory hysteresis can be effectively modulated by adjusting the side-gate geometries.
September 2016: Advanced Science (Weinheim, Baden-Wurttemberg, Germany)
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