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Mechanical Modulation of Colossal Magnetoresistance in Flexible Epitaxial Perovskite Manganite
(1970-01-01)
Yen, Min
;
Lai, Yu-Hong
;
Kuo, Chang-Yang
;
Chen, Chien-Te
;
Chang, Chun-Fu
Heteroepitaxially flexible oxide systems have been intensely developed and considered as the most promising materials for leading the creation of next-generation flexible electronic devices. Among them, perovskite manganites have attracted significant attention with their abundant and novel properties such as colossal magnetoresistance (CMR) and metal-insulator transition. However, the requirement of high quality samples hampers this field, not to mention the advanced nanoengineering. In this study, fluorophlogopite mica (F-mica) is selected as a flexible substrate to fabricate heteroepitaxial Pr0.5Ca0.5MnO3(PCMO) with a nanocolumn structure. Through a precise control of thickness, different morphologies are realized to manipulate the magnetotransport properties (reduction of melting field). Moreover, thanks to the excellent flexibility of F-mica, mechanical modulation of CMR (approximate to 1000%) can be achieved in different flex modes while the magnetic properties remain unaffected. Detailed bending tests are performed to study the behavior of resistive change (approximate to 30%). Through the combination of high flexibility, high quality PCMO, and well-designed nanocolumn structure, the study exhibits the significant controllability of CMR via mechanical bending, and manifests the potential of such a heteroepitaxially flexible oxide system which can be applied on flexible magnetoresistive devices and sensors.
Transparent Flexible Heteroepitaxy of NiO Coated AZO Nanorods Arrays on Muscovites for Enhanced Energy Storage Application
(1970-01-01)
Van-Qui Le
;
Phuoc-Anh Le
;
Wu, Shu-Chi
;
Lai, Yu-Hong
;
Lin, Yan-Gu
Transparent flexible energy storage devices are considered as important chains in the next-generation, which are able to store and supply energy for electronic devices. Here, aluminum-doped zinc oxide (AZO) nanorods (NRs) and nickel oxide (NiO)-coated AZO NRs on muscovites are fabricated by a radio frequency (RF) magnetron sputtering deposition method. Interestingly, AZO NRs and AZO/NiO NRs are excellent electrodes for energy storage application with high optical transparency, high conductivity, large surface area, stability under compressive and tensile strain down to a bending radius of 5 mm with 1000 bending cycles. The obtained symmetric solid-state supercapacitors based on these electrodes exhibit good performance with a large areal specific capacitance of 3.4 mF cm(-2), long cycle life 1000 times, robust mechanical properties, and high chemical stability. Furthermore, an AZO/NiO//Zn battery based on these electrodes is demonstrated, yielding a discharge capacity of 195 mAh g(-1) at a current rate of 8 A g(-1) and a discharge capacity of over 1000 cycles with coulombic efficiency to 92%. These results deliver a concept of opening a new opportunity for future applications in transparent flexible energy storage.
Topological Hall Effect in Single Thick SrRuO3 Layers Induced by Defect Engineering
(1970-01-01)
Wang, Changan
;
Chang, Ching-Hao
;
Herklotz, Andreas
;
Chen, Chao
;
Ganss, Fabian
The topological Hall effect (THE) has been discovered in ultrathin SrRuO3 (SRO) films, where the interface between the SRO layer and another oxide layer breaks the inversion symmetry resulting in the appearance of THE. Thus, THE only occurs in ultrathin SRO films of several unit cells. In addition to employing a heterostructure, the inversion symmetry can be broken intrinsically in bulk SRO by introducing defects. In this study, THE is observed in 60-nm-thick SRO films, in which defects and lattice distortions are introduced by helium ion irradiation. The irradiated SRO films exhibit a pronounced THE in a wide temperature range from 5 to 80 K. These observations can be attributed to the emergence of Dzyaloshinskii-Moriya interaction as a result of artificial inversion symmetry breaking associated with the lattice defect engineering. The creation and control of the THE in oxide single layers can be realized by ex situ film processing. Therefore, this work provides new insights into the THE and illustrates a promising strategy to design novel spintronic devices.
Unexpected Giant Microwave Conductivity in a Nominally Silent BiFeO3 Domain Wall
(1970-01-01)
Huang, Yen-Lin
;
Zheng, Lu
;
Chen, Peng
;
Cheng, Xiaoxing
;
Hsu, Shang-Lin
Nanoelectronic devices based on ferroelectric domain walls (DWs), such as memories, transistors, and rectifiers, have been demonstrated in recent years. Practical high-speed electronics, on the other hand, usually demand operation frequencies in the gigahertz (GHz) regime, where the effect of dipolar oscillation is important. Herein, an unexpected giant GHz conductivity on the order of 10(3) S m(-1) is observed in certain BiFeO3 DWs, which is about 100 000 times greater than the carrier-induced direct current (dc) conductivity of the same walls. Surprisingly, the nominal configuration of the DWs precludes the alternating current (ac) conduction under an excitation electric field perpendicular to the surface. Theoretical analysis shows that the inclined DWs are stressed asymmetrically near the film surface, whereas the vertical walls in a control sample are not. The resultant imbalanced polarization profile can then couple to the out-of-plane microwave fields and induce power dissipation, which is confirmed by the phase-field modeling. Since the contributions from mobile-carrier conduction and bound-charge oscillation to the ac conductivity are equivalent in a microwave circuit, the research on local structural dynamics may open a new avenue to implement DW nano-devices for radio-frequency applications.
Observation of oxygen pyramid tilting induced polarization rotation in strained BiFeO3 thin film
(1970-01-01)
Song, Dongsheng
;
Liu, Heng-Jui
;
Kovacs, Andras
;
Dunin-Borkowski, Rafal E.
;
Chu, Ying-Hao
Oxygen octahedral tilting has been recognized to strongly interact with spin, charge, orbital, and lattice degrees of freedom in perovskite oxides. Here, we observe a strain-driven stripe-like morphology of two supertetragonal (monoclinic Cc and Cm) phases in the strained BiFeO3/LaAlO3 thin films. The two supertetragonal phases have a similar giant axial ratio but differences in oxygen pyramid tilting mode. Especially, the competition between polar instability and oxygen pyramid tilting is identified using atomically resolved scanning transmission electron microscopy, leading to the polarization rotation across the phase boundary. In addition, microtwins are observed in the Cc phase. Our findings provide new insights of the coupling between ferroelectric polarization and oxygen pyramid tilting in oxide thin films and will help to design novel phase morphology with desirable ferroelectric polarization and properties for new applications in perovskite oxides.
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.
Enhanced Ferroelectric Functionality in Flexible Lead Zirconate Titanate Films with In Situ Substrate-Clamping Compensation
(1970-01-01)
Winestook, Rachel Onn
;
Saguy, Cecile
;
Ma, Chun-Hao
;
Chu, Ying-Hao
;
Ivry, Yachin
Much attention has recently been given to flexible and wearable integrated electronic devices, with a strong emphasis on real-time sensing, computing, and communication technologies. Thin ferroelectric films exhibit switchable polarization and strong electromechanical coupling, and hence are in widespread use in such technologies, albeit not when flexed. Effects of extrinsic strain on thin ferroelectric films are still unclear, mainly due to the lack of suitable experimental systems that allow cross structural-functional characterization with in situ straining. Moreover, although the effects of intrinsic strain on ferroelectric films, e.g., due to film-substrate lattice mismatch, have been extensively investigated, it is unclear how these effects are influenced by external strain. A method to strain thin films homogenously in situ is developed, allowing structural characterization as well as functional switching and piezorsponse measurements at the nanoscale, while retaining the sample under constant straining conditions. Using this method, thin films of PbZr0.2Ti0.8O3, which were grown on a flexible mica substrate, are strained to reduce substrate clamping effects and increase the tetragonality. Consequently, the domain stability is increased, the coercive field value is decreased, and imprint effects are reduced. This method also allows direct characterization of the relationship between the lattice parameters and nanoscale properties of other flexible materials.
Local Conduction at the BiFeO3-CoFe2O4 Tubular Oxide Interface
(1970-01-01)
Hsieh, Ying-Hui
;
Liou, Jia-Ming
;
Huang, Bo-Chao
;
Liang, Chen-Wei
;
He, Qing
"In strongly correlated oxides, heterointerfaces, manipulating the interaction, frustration, and discontinuity of lattice, charge, orbital, and spin degrees of freedom, generate new possibilities for next generation devices. In this study, existing oxide heterostructures are examined and local conduction at the BiFeO3-CoFe2O4 vertical interface is found. In such heteronanostructures the interface cannot only be the medium for the coupling between phases, but also a new state of the matter. This study demonstrates a novel concept on for oxide interface design and opens an alternative pathway for the exploration of diverse functionalities in complex oxide interfaces."

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