Browsing by Author "Li, Jiangyu"

Now showing 1 - 9 of 9

Conductive tail-to-tail domain walls in epitaxial BiFeO3 films
(2018-08-20)
Jin, Yaming
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Xiao, Shuyu
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Yang, Jan-Chi
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Zhang, Junting
;
Lu, Xiaomei
The complex conductive behavior of ferroelectric domain walls is attracting more and more attention for their potential application as an independent nanoelectronic component. For the (001) epitaxial BiFeO3 films, we find that the domain wall conductivity varies among 71 degrees domain walls, with tail-to-tail (T-T) domain walls more conductive than head-to-head (H-H) and head-to-tail (H-T) ones. Furthermore, it is observed that most of the conductive areas are composed of two parallel lines around the T-T domain walls. These experimental results can be well simulated by our theoretical model based on the polarization configuration and a tunneling mechanism. Our work will help to understand the mechanism of domain wall conductance in ferroelectric materials and further promote the usage of domain walls in advanced nano-devices. Published by AIP Publishing.
Design of magnetoelectric coupling in a self-assembled epitaxial nanocomposite via chemical interaction
(2014)
Liang, Wen I.
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Liu, Yuangming
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Liao, Sheng Chieh
;
Wang, Wei Cheng
;
Liu, Heng Jui
A chemically induced magnetoelectric coupling effect in ferroelectric/antiferromagnetic self-assembled vertical nanocomposites is designed. A concrete connection between chemical diffusion and the induced magnetic moment is revealed. Importantly, this study shows the strong magnetoelectric coupling effect, which is key to extend the design of functionality in vertical nanocomposites.
Deterministic, Reversible, and Nonvolatile Low-Voltage Writing of Magnetic Domains in Epitaxial BaTiO3/Fe3O4 Heterostructure
(2018-09-01)
Zhong, Gaokuo
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An, Feng
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Bitla, Yugandhar
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Wang, Jinbin
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Zhong, Xiangli
The ability to electrically write magnetic bits is highly desirable for future magnetic memories and spintronic devices, though fully deterministic, reversible, and nonvolatile switching of magnetic moments by electric field remains elusive despite extensive research. In this work, we develop a concept to electrically switch magnetization via polarization modulated oxygen vacancies, and we demonstrate the idea in a multiferroic epitaxial heterostructure of BaTiO3/Fe3O4 fabricated by pulsed laser deposition. The piezoelectricity and ferroelectricity of BaTiO3 have been confirmed by macro- and microscale measurements, for which Fe(3)O(4 )serves as the top electrode for switching the polarization. X-ray absorption spectroscopy and X-ray magnetic circular dichroism spectra indicate a mixture of Fe2+ and Fe3+ at O-h sites and Fe3+ at T-d sites in Fe3O4, while the room-temperature magnetic domains of Fe3O4 are revealed by microscopic magnetic force microscopy measurements. It is demonstrated that the magnetic domains of Fe(3)O(4 )can be switched by not only magnetic fields but also electric fields in a deterministic, reversible, and nonvolatile manner, wherein polarization reversal by electric field modulates the oxygen vacancy distribution in Fe3O4, and thus its magnetic state, making it attractive for electrically written magnetic memories.
Giant Enhancement of Ferroelectric Retention in BiFeO3 Mixed-Phase Boundary
(2014-09-24)
Huang, Yen-Chin
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Liu, Yunya
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Lin, Yi-Tsu
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Liu, Heng-Jui
;
He, Qing
A large enhancement of nanodomain retentionis shown in the mixed-phase region of a strained BiFeO3 epitaxial film. The superior ferroelectric retention is attributed to a lower elastic-energy density at the phase boundaries, which act as periodic pinning centers for the domain wall motion. This study delivers a new pathway of incorporating an elastic-energy term to assist ferroelectric retention.
Highly flexible, robust, stable and high efficiency perovskite solar cells enabled by van der Waals epitaxy on mica substrate
(2019-06-01)
Jia, Chunmei
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Zhao, Xingyu
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Lai, Yu-Hong
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Zhao, Jinjin
;
Wang, Pei-Chun
Flexible and lightweight solar cells are promising for numerous emerging applications, and organometallic halide perovskites are particularly suitable for flexible solar cell applications. Transferring state of art high efficiency perovskite solar cells (PSCs) processing onto a flexible substrate, however, is challenging, requiring substantial redevelopment of materials compositions, device architectures, and processing conditions. In this work, highly flexible, robust, stable, and high efficiency PSCs based on mica substrate have been successfully developed, exhibiting a champion photovoltaic conversion efficiency (PCE) of 18.0%, retaining more than 91.7% of the original PCE after 5000 cycles of large deformation bending, and being relatively stable against humidity under elevated temperature. Key to such excellent performance is the inorganic and transparent mica substrate that is chemically inert and stable under high temperature, so that processing developed for glass-based high efficiency perovskite solar cells (PSCs) can be readily applied without modification. Furthermore, the layered mica substrate is highly flexible, and van der Waals epitaxial growth of transparent conducing ITO relaxes the mechanical constraint on the PSCs substantially, reducing the strain in the device even under large bending deformation. We believe inorganic flexible mica substrate can be used as a platform for high efficiency PSCs compatible to glass substrate, speeding up the development of flexible PSCs substantially.
Nanoscale Control of Phase Variants in Strain-Engineered BiFeO(3)
(2011-08-01)
Vasudevan, Rama K.
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Liu, Yunya
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Li, Jiangyu
;
Liang, Wen-I
;
Kumar, Amit
Development of magnetoelectric, electromechanical, and photovoltaic devices based on mixed-phase rhombohedral-tetragonal (R-T) BiFeO(3) (BFO) systems is possible only if the control of the engineered R phase variants is realized. Accordingly, we explore the mechanism of a bias induced phase transformation in this system. Single point spectroscopy demonstrates that the T -> R transition is activated at lower voltages compared to T -> - T polarization switching. With phase field modeling, the transition is shown to be electrically driven. We further demonstrate that symmetry of formed R-phase rosettes can be broken by a proximal probe motion, allowing controlled creation of R variants with defined orientation. This approach opens a pathway to designing next-generation magnetoelectronic and data storage devices in the nanoscale.
Nanoscale Control of Phase Variants in Strain-Engineered BiFeO3
(2011-08-01)
Vasudevan, Rama K.
;
Liu, Yunya
;
Li, Jiangyu
;
Liang, Wen-I
;
Kumar, Amit
Development of magnetoelectric, electromechanical, and photovoltaic devices based on mixed-phase rhombohedral-tetragonal (R-T) BiFeO3 (BFO) systems is possible only if the control of the engineered R phase variants is realized. Accordingly, we explore the mechanism of a bias induced phase transformation in this system. Single point spectroscopy demonstrates that the T -> R transition is activated at lower voltages compared to T -> - T polarization switching. With phase field modeling, the transition is shown to be electrically driven. We further demonstrate that symmetry of formed R-phase rosettes can be broken by a proximal probe motion, allowing controlled creation of R variants with defined orientation. This approach opens a pathway to designing next-generation magnetoelectronic and data storage devices in the nanoscale.
Piezoelectric and piezomagnetic force microscopies of multiferroic BiFeO3-LiMn2O4 heterostructures
(2014-08-14)
Eshghinejad, Ahmad
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Liang, Wen-I.
;
Chen, Qian Nataly
;
Ma, Feiyue
;
Liu, Yuanming
BiFeO3-LiMn2O4 (BFO-LMO) heterostructures were fabricated via pulsed laser deposition, and their ferroelectric and ferromagnetic properties were probed by magnetic force microscopy (MFM), piezoresponse force microscopy (PFM), and the newly developed piezomagnetic force microscopy (PmFM). MFM imaging shows no clear distinction between BFO and LMO phases, while PFM and PmFM mappings clearly distinguish LMO nanopillars from BFO matrix. Linear piezoelectric and piezomagnetic responses have been observed in both phases, with the effects more prominent in BFO. The strong piezomagnetic response in BFO is believed to arise from Mn doping, while piezoelectric-like response of LMO is attributed to ionic activities as well as vertical geometry of the heterostructure. The limitation of global excitation of PmFM is also discussed. (C) 2014 AIP Publishing LLC.
PROBING MULTIFERROIC HETEROSTRUCTURES OF BiFeO3-LiMn2O4 USING MAGNETIC, PIEZOELECTRIC AND PIEZOMAGNETIC FORCE MICROSCOPIES
(2014-01-01)
Eshghinejad, Ahmadreza
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Liang, Wen-I
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Chen, Qian Nataly
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Ma, Feiyue
;
Chu, Ying-Hao
In this study magnetic force microscopy (MFM), piezore-sponse force microscopy (PFM), and the newly developed piezomagnetic force microscopy (PmFM) techniques are used to probe the ferroelectric and ferromagnetic properties of BiFeO3-LiMn2O4 (BFO-LMO) heterostructures at nano-scale. The PmFM technique is also used to probe the ferromagnetic properties of CoFe2O4 (CFO) as a case study. The PFM and PmFM mappings of the BFO-LMO heterostructures clearly distinguish the BFO matrix and LMO nanopillars while the MFM mapping is ambiguous. The relatively high piezomagnetic response of BFO matrix is believed to be due to the Mn doping while the piezoelectric-like response of LMO nanopillars is due to the ionic activities and the vertical geometry of its heterostructure. Lastly, limitations of the PmFM technique are discussed.