Browsing by Author "Kuo, Wei-Cheng"

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A Nanostructuring Method to Decouple Electrical and Thermal Transport through the Formation of Electrically Triggered Conductive Nanofilaments
(2018-07-12)
Retamal, Jose Ramon Duran
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Kang, Chen-Fang
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Lien, Der-Hsien
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Kuo, Wei-Cheng
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Juang, Zhen-Yu
Transforming thermal energy into electric energy and vice versa needs the decoupling of electrical transport from thermal transport. An innovative strategy is proposed by forming/disrupting electrically triggered conductive nanofilaments within semiconducting thin films to switch thermoelectric properties between two states without further material modification and manufacturing processes. It can also controllably adjust the degree of decoupling, providing a potential resolution and performance adjustability for heat/coldness control or power consumption reduction on demand.
An Automatic Light Monitoring System with Light-to-Frequency Converter for Flower Planting
(2008)
Kuo, Wei-Cheng
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Chiang, Cheng-Tai
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Huang, Yu-Chung
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電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
In this paper, an automatic light monitoring system with light-to-frequency converter for flower planting is newly proposed. Based on the requirements for flower planting, the proposed light monitoring system is thus analyzed and designed. Besides, the designed light transducer which is implemented as a light-to-frequency converter, is attractive due to that a digitized signal is produced without realizing the analog to digital converter Hence, the hardware cost could be reduced. All the functions and performance of the proposed light monitoring system are successfully proven through measurement results. The proposed light monitoring system is rather suitable for the needs in a large flower planting area.
Complex Oxide-Noble Metal Conjugated Nanoparticles
(2013-04-11)
Guo, Jun-Ling
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Chiou, Yao-De
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Liang, Wen-I
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Liu, Heng-Jui
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Chen, Ying-Jiun
Hybrid nanoparticles (NPs) composed of multiple components offer new opportunities for next-generation materials. In this study, a paradigm for the noble metal/ternary complex oxide hybrid NPs is reported by adopting pulsed laser ablation in liquids. As model hybrids, gold-spinel heterodimer (Au-CoFe2O4) and gold-pervoskite heterodimer (Au-SrTiO3) NPs are investigated. This work has demonstrated the diverse playgroup of NP conjugation enlarged by complex oxides.
Effects of Structural Strain and Rare-Earth Moments on Spin Cycloidal-Plane in Multiferroic Rare-Earth Manganites
(2016-05)
Hsiao, Yen-Fu
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Kuo, Wei-Cheng
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Mi, Chun-Wei
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Chang, Kai-Ting
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Luo, Chih-Wei
A series of orthorhombic multiferroic manganites (o-ReMnO3) thin films with deliberately designed strain states and different rare-earth elements were prepared to unveil the roles played by the strain and 4f-electron moments in determining the magnetic ordering and associated polarizations. The results obtained from temperature-dependent magnetization, dielectric and ferroelectric measurements revealed that the orientations of magnetic reordering and polarization varied with the specific rare-earth element involved. Namely, with the increase of total angular momentum J of the 4f-electrons of rare-earth element the orientation of magnetic reordering was changed from the b-axis (sinusoidal state) for Yb3+ to the a-axis (ab-cycloidal) for Tm3+ and, eventually to the c-axis (bc-cycloidal) for Er3+ and Ho3+. These results indicate that the Re-Mn magnetic exchange interaction plays a more important role than the external strain does in determining the magnetic and hence polarization states in multiferroic o-ReMnO3 manganites. Our results also confirmed the coexistence of different magnetic spin states in o-ReMnO3 thin films.
Epitaxial integration of a nanoscale BiFeO3 phase boundary with silicon
(2016-01-01)
Liang, Wen-I
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Peng, Chun-Yen
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Huang, Rong
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Kuo, Wei-Cheng
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Huang, Yen-Chin
The successful integration of the strain-driven nanoscale phase boundary of BiFeO3 onto a silicon substrate is demonstrated with extraordinary ferroelectricity and ferromagnetism. The detailed strain history is delineated through a reciprocal space mapping technique. We have found that a distorted monoclinic phase forms prior to a tetragonal-like phase, a phenomenon which may correlates with the thermal strain induced during the growth process.
Epitaxial integration of a nanoscale BiFeO3 phase boundary with silicon
(2016)
Liang, Wen-I
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Peng, Chun-Yen
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Huang, Rong
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Kuo, Wei-Cheng
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Huang, Yen-Chin
The successful integration of the strain-driven nanoscale phase boundary of BiFeO3 onto a silicon substrate is demonstrated with extraordinary ferroelectricity and ferromagnetism. The detailed strain history is delineated through a reciprocal space mapping technique. We have found that a distorted monoclinic phase forms prior to a tetragonal-like phase, a phenomenon which may correlates with the thermal strain induced during the growth process.
Self-Assembled Epitaxial Core-Shell Nanocrystals with Tunable Magnetic Anisotropy
(2015-09-02)
Liao, Sheng-Chieh
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Chen, Yong-Lun
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Kuo, Wei-Cheng
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Cheung, Jeffrey
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Wang, Wei-Cheng
Self-formed conductive nanofilaments in (Bi, Mn)O-x for ultralow-power memory devices
(2015-04-01)
Kang, Chen-Fang
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Kuo, Wei-Cheng
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Bao, Wenzhong
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Ho, Chih-Hsiang
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Huang, Chun-Wei
Resistive random access memory (RRAM) is one of the most promising candidates as a next generation nonvolatile memory (NVM), owing to its superior scalability, low power consumption and high speed. From the materials science point of view, to explore optimal RRAM materials is still essential for practical application. In this work, a new material (Ni, Mn)0 (BMO) is investigated and several key performance characteristics of Pt/ BMO/Pt structured device, including switching performance, retention and endurance, are examined in details. Furthermore, it has been confirmed by high-resolution transmission electron microscopy that the underlying switching mechanism is attributed to formation and disruption of metallic conducting nanofilaments (CNFs). More importantly, the power dissipation for each CNF is as low as 3.8/20 fJ for set/reset process, and a realization of cross-bar structure memory cell is demonstrated to prove the downscaling ability of proposed RRAM. These distinctive properties have important implications for understanding switching mechanisms and implementing ultralow power-dissipation RRAM based on BMO. (C) 2015 Elsevier Ltd. All rights reserved.
Strong magnetic enhancement in self-assembled multiferroic-ferrimagnetic nanostructures
(2013)
Chen, Ying-Jiun
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Hsieh, Ying-Hui
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Liao, Sheng-Chieh
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Hu, Zhiwei
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Huang, Meng-Jie
In the past decade, self-assembled vertical nano-heterostructures have drawn considerable attention because a high interface-to-volume ratio can be used to tailor or create functionalities. We have systematically investigated the magnetic properties of oxide heterostructures consisting of the CoFe2O4 nanopillars embedded in the BiFeO3 matrix using macroscopic magnetization measurements and element-selective soft X-ray absorption magnetic circular dichroism (XMCD) at the Co- and Fe-L-2,L-3 edge. The magnetization and XMCD data show that the total ordered magnetic moment of Co2+ in CoFe2O4-BiFeO3 nano-heterostructures is strongly enhanced. This study clearly indicates that the high interface-to-volume ratio vertical nanostructure creates a strong ferromagnetic and antiferromagnetic magnetic coupling via an interface. Furthermore, the magnetic coupling can be tuned in the multiferroic-ferrimagnetic self-assembled heterostructures by controlling the spacing between nanopillars.