Browsing by Author "Tang, Xiao-Dong"

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Atomic-Scale Visualization of Polarization Pinning and Relaxation at Coherent BiFeO3/LaAlO3 Interfaces
(2014-02-01)
Huang, Rong
;
Ding, Hang-Chen
;
Liang, Wen-I
;
Gao, Yong-Chao
;
Tang, Xiao-Dong
Complex oxide heterointerfaces, which play host to an incredible variety of interface physical phenomena, are of great current interest in introducing new functionalities to systems. Here, coherent super-tetragonal BiFeO3/LaAlO3 and rhombohedral BiFeO3/LaAlO3 heterointerfaces are investigated by using a combination of high-angle annular dark-field (HAADF) imaging and annular bright-field (ABF) imaging in a spherical aberration (Cs) corrected scanning transmission electron microscope (STEM), and first-principles calculations. The complicated ferroelectric polarization pinning and relaxation that occurs at both interfaces is revealed with atomic resolution, with a dramatic change in structure of BiFeO3, from cubic to super-tetragonal-like. The results enable a detailed explanation to be given of how non-bulk phase structures are stabilized in thin films of this material.
Proton-Mediated Phase Control in Flexible and Transparent Mott Transistors
(1970-01-01)
Deng, Xing
;
Zhao, Yi-Feng
;
Zhong, Ni
;
Yue, Fang-Yu
;
Huang, Rong
To meet the development of wearable and energy-efficient flexible electronics, multifunctional oxide film on soft substrate and its versatile phase control are in demand. Here, flexible VO2 film is directly deposited on mica via van der Waals epitaxy, exhibiting pronounced metal-insulator (MI) transition and infrared (IR) switching properties. Using a rubbery solid ionic gel as gate insulator, a fully flexible and transparent VO2-channel Mott transistor is successfully demonstrated. The prototype Mott transistor processes excellent mechanical flexibility and giant on/off current ratio of approximate to 10(5)% even at room temperature. Highly reversible suppression of MI transition is realized by applying small gate voltages and the nonvolatile phase modulation suggests an electrochemical reaction mechanism. X-ray diffraction and secondary-ion mass spectroscopy analyses, together with theoretical calculation, confirm that electrically controlled phase transformation is mainly caused by reversible and nonvolatile proton (H+) doping into VO2 lattices. Significant modulation of IR transmittance (>40%) is observed in the VO2 Mott transistor, which is attributed to electrically driven phase transition between insulating VO2 and metallic HxVO2 phases. The flexible and transparent Mott transistor provides a good platform for proton-mediated Mottronics and realizes novel electric control of optical characteristics, showing a promising application for flexible energy-saving smart windows.
The preparation, and structural and multiferroic properties of B-site ordered double-perovskite Bi2FeMnO6
(2017-06-14)
Sun, Lin
;
Fang, Yue-Wen
;
He, Jun
;
Zhang, Yuanyuan
;
Qi, Ruijuan
We report the structural, magnetic, and ferroelectric properties of double-perovskite Bi2FeMnO6 in which Fe3+ and Mn3+ cations are present with alternative ordering along the [111] direction. High-flux synchrotron X-ray diffraction and high resolution transmission electron microscopy show that the pseudo-cubic lattice of Bi2FeMnO6 consists of alternatively corner-shared octahedra of FeO6 and MnO6. In the highly ordered Bi2FeMnO6 thin films, the unusual spin-glassy magnetic state is observed below 18 K by a superconducting quantum interference device, and this is ascribed to the magnetic frustration at the [111] Fe3+ and Mn3+ planes as indicated by X-ray magnetic circular dichroism measurements. Combining with the orbital model analysis based on Goodenough-Kanamori-Anderson rules, first-principles calculations and Monte Carlo simulations suggest that magnetic frustration is dominated by the long-range second nearest neighboring antiferromagnetic interactions of Fe3+-Fe3+ and Mn3+-Mn3+ and leads to the surprisingly weak magnetism. On the other hand, robust room-temperature ferroelectricity in Bi2FeMnO6 films is confirmed by piezoelectric force microscopy through electrically switching the polarization state and the ferroelectric retention.