Browsing by Author "Huang, Yen-Lin"

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An improved algorithm for sorting by block-interchanges based on permutation groups
(2010-04-01)
Huang, Yen-Lin
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Huang, Cheng-Chen
;
Tang, Chuan Yi
;
Lu, Chin Lung
;
生物科技學系
Given a chromosome represented by a permutation of genes, a block-interchange is proposed as a generalized transposition that affects the chromosome by swapping two non-intersecting segments of genes. The problem of sorting by block-interchanges is to find a minimum series of block-interchanges for sorting one chromosome into another. In this paper, we present an O(n + delta log delta) time algorithm for solving the problem of sorting by block-interchanges, which improves a previous algorithm of O(delta n) time proposed by Lin et al. (2005) [14], where n is the number of genes and delta is the minimum number of block-interchanges required to sort a chromosome. (C) 2010 Elsevier B.V. All rights reserved.
Analytical Noise Optimization of Single-/Dual-Band MOS LNAs With Substrate and Metal Loss Effects of Inductors
(2019-07-01)
Chang, Wei Ling
;
Meng, Chinchun
;
Ni, Jung-Hung
;
Ch, Kai-Chun
;
Chang, Chih-Kai
Analytical noise formulations and design optimization of single- and dual-band inductively source-degenerated MOS low-noise amplifiers (LNAs) with the substrate and metal loss effects of on-chip inductors are established in this paper. It reveals that the noise figures of both single-/dual-band LNAs degrade substantially under the consideration of the loss effects. However, by increasing the device size, the noise optimization methodology of simultaneous noise and input match for a single-band LNA still holds true with concern for the loss effects. For a dual-band LNA, analytical noise optimization for a balanced noise design is established for inductors with metal and substrate loss and indicates a larger device size. The substrate and metal loss effects of inductors can be mitigated using integrated passive device (IPD) process for the input match network. The demonstrated single-band 0.18-mu m MOS LNAs with and without IPD process show noise figures of 1.53 and 2.52 dB at 2.4 GHz, respectively. Subsequently, the implemented dual-band 0.18-mu m MOS LNAs with and without IPD process show noise figures of 1.6/2.6 and 3.25/4.1 dB at 2.4/5 GHz, respectively.
Anisotropic superconductivity induced by periodic multiferroic domain patterns
(2019-12-06)
Huang, Yen-Lin
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Huang, Bo-Chao
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Wang, Yan-Ting
;
Xue, Fei
;
Lin, Jheng-Cyuan
The competition between order parameters, such as ferroelectricity, ferromagnetism, and superconductivity, is one of the most fascinating topics in condensed matter physics. Here, we report intriguing anisotropic superconductivity in YBa2Cu3O7-x films induced by a multiferroic, BiFeO3, with periodic domain patterns. The anisotropic superconductivity was investigated by transport measurements and supported by phase-field simulations, and then the detailed local electronic structures were revealed by cross-sectional scanning tunneling microscopy. We found that the oxygen redistribution in YBa2Cu3O7-x modulated by the ferroelectric polarization in BiFeO3 was the key mechanism driving this anisotropic superconductivity. The presented heteroarchitecture of a high-temperature superconductor and a domain-engineered multiferroic provides a new approach to tune superconductivity and offers potential advantages for the design of future multifunctional devices.
Anomalous Electronic Anisotropy Triggered by Ferroelastic Coupling in Multiferroic Heterostructures
(2016-02-03)
Ju, Changcheng
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Yang, Jan-Chi
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Luo, Cheng
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Shafer, Padraic
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Liu, Heng-Jui
Atomic mechanism of polarization-controlled surface reconstruction in ferroelectric thin films
(2016-04-01)
Gao, Peng
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Liu, Heng-Jui
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Huang, Yen-Lin
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Chu, Ying-Hao
;
Ishikawa, Ryo
At the ferroelectric surface, the broken translational symmetry induced bound charge should significantly alter the local atomic configurations. Experimentally revealing the atomic structure of ferroelectric surface, however, is very challenging due to the strong spatial variety between nano-sized domains, and strong interactions between the polarization and other structural parameters. Here, we study surface structures of Pb(Zr0.2Ti0.8)O-3 thin film by using the annular bright-field imaging. We find that six atomic layers with suppressed polarization and a charged 180 degrees domain wall are at negatively poled surfaces, no reconstruction exists at positively poled surfaces, and seven atomic layers with suppressed polarization and a charged 90 degrees domain wall exist at nominally neutral surfaces in ferroelastic domains. Our results provide critical insights into engineering ferroelectric thin films, fine grain ceramics and surface chemistry devices. The state-of-the-art methodology demonstrated here can greatly advance our understanding of surface science for oxides.
Atomic-scale mechanism of internal structural relaxation screening at polar interfaces
(2018-05-25)
Li, Mingqiang
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Cheng, Xiaoxing
;
Li, Ning
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Liu, Heng-Jui
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Huang, Yen-Lin
The effective screening of the polarization bound charge is a prerequisite to stabilize the ferroelectricity in ferroelectric thin films. Here, by combining annular bright field imaging and electron energy-loss spectroscopy (EELS) in an aberration-corrected scanning transmission electron microscope with phase-field simulations, we investigate the screening mechanism by quantitatively measuring the structural relaxation at Pb(Zr0.2Ti0.8)O-3/SrTiO3 interfaces. We find that the thickness of the interfacial layer is similar to 3.5 unit cells (similar to 1.4 nm) in a domain with upward polarization and similar to 5.5 unit cells (similar to 2.2 nm) in a domain with downward polarization. Phase-field simulations, an EELS analysis, and a lattice parameter analysis verify the existence of interfacial oxygen vacancies accounting for the narrower interfacial layer in the domain with upward polarization. Our study indicates the internal structural relaxation at the interface is the dominant mechanism for the polarization charge screening for ferroelectric films grown on insulating substrates and has implications for our understanding of domain switching in ferroelectric devices.
Complex strain evolution of polar and magnetic order in multiferroic BiFeO3 thin films
(2018-09-21)
Chen, Zuhuang
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Chen, Zhanghui
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Kuo, Chang-Yang
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Tang, Yunlong
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Dedon, Liv R.
Electric-field control of magnetism requires deterministic control of the magnetic order and understanding of the magnetoelectric coupling in multiferroics like BiFeO3 and EuTiO3. Despite this critical need, there are few studies on the strain evolution of magnetic order in BiFeO3 films. Here, in (110)-oriented BiFeO3 films, we reveal that while the polarization structure remains relatively unaffected, strain can continuously tune the orientation of the antiferromagnetic-spin axis across a wide angular space, resulting in an unexpected deviation of the classical perpendicular relationship between the antiferromagnetic axis and the polarization. Calculations suggest that this evolution arises from a competition between the Dzyaloshinskii-Moriya interaction and single-ion anisotropy wherein the former dominates at small strains and the two are comparable at large strains. Finally, strong coupling between the BiFeO3 and the ferromagnet Co0.9Fe0.1 exists such that the magnetic anisotropy of the ferromagnet can be effectively controlled by engineering the orientation of the antiferromagnetic-spin axis.
Deterministic optical control of room temperature multiferroicity in BiFeO3 thin films
(2019-06-01)
Liou, Yi-De
;
Chiu, Yu-You
;
Hart, Ryan Thomas
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Kuo, Chang-Yang
;
Huang, Yen-Lin
Controlling ferroic orders (ferroelectricity, ferromagnetism and ferroelasticity) by optical methods is a significant challenge due to the large mismatch in energy scales between the order parameter coupling strengths and the incident photons. Here, we demonstrate an approach to manipulate multiple ferroic orders in an epitaxial mixed-phase BiFeO3 thin film at ambient temperature via laser illumination. Phase-field simulations indicate that a light-driven flexoelectric effect allows the targeted formation of ordered domains. We also achieved precise sequential laser writing and erasure of different domain patterns, which demonstrates a deterministic optical control of multiferroicity at room temperature. As ferroic orders directly influence susceptibility and conductivity in complex materials, our results not only shed light on the optical control of multiple functionalities, but also suggest possible developments for optoelectronics and related applications.
Direct observation of weakened interface clamping effect enabled ferroelastic domain switching
(2019-06-01)
Li, Mingqiang
;
Wang, Bo
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Liu, Heng-Jui
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Huang, Yen-Lin
;
Zhang, Jingmin
Reversible switching of non-180 degrees ferroelastic domains that largely alters the local strain distribution enables many electromechanical, electromagnetic and electroacoustic applications. However, in thin films, the ferroelastic domain walls are usually believed to be immobile because of the interface clamping and/or dislocation pinning. Here, using in situ and aberration-corrected transmission electron microscopy, we directly observe reversible switching of individual 90 degrees domains in dislocation-free PbTiO3 thin films and uncover the weakened interface clamping effect. We find the tetragonality is suppressed to similar to 1.017 while the polarization vectors rotate 45 degrees in the a-domain near the interface. These huge structural distortions at the interface is mainly responsible for the weakened clamping effect and thus the ability to switch ferroelastic domains. The switching is fully reversible (i.e., either electric field or mechanical stress can re-establish the erased domain) regardless of polarization orientation of the c-domain matrix. Phase-field modeling also shows excellent agreement with experimental observations. Our study reveals the mechanism of controllable and reversible ferroelastic domain switching, enabling the design of new actuators, sensors, and electromagnetic devices. (C) 2019 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
Electric Field Writing of Ferroelectric Nano-Domains Near 71 degrees Domain Walls with Switchable Interfacial Conductivity
(2018-08-01)
Yang, Shuzhen
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Peng, Ren-Ci
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He, Qing
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Huang, Yen-Lin
;
Huang, Yijing
Conducting ferroelectric domain walls attract a wide range of research interest due to their promising applications in nanoelectronics. In this study, we reveal an unexpected enhanced conductivity near the well-aligned 71 degrees nonpolar domain walls in BiFeO3. Such an interfacial conductivity is induced by the creation of up-polarized nano-domains near the 71 degrees domain walls, as revealed by the combination of the piezo-response force microscopy (PFM) and conducting atomic force microscopy (c-AFM) imaging techniques, as well as phase-field simulations. The upward polarized domains are suggested to lower the Schottky barrier at the interface between the tip and sample surface, and then give rise to the enhanced interfacial conductivity. The result provides a new strategy to tune the local conductance in ferroelectric materials and opens up new opportunities to design novel nanoelectronic devices.
Manipulating magnetoelectric energy landscape in multiferroics
(2020-06-05)
Huang, Yen-Lin
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Nikonov, Dmitri
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Addiego, Christopher
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Chopdekar, Rajesh, V
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Prasad, Bhagwati
Magnetoelectric coupling at room temperature in multiferroic materials, such as BiFeO3, is one of the leading candidates to develop low-power spintronics and emerging memory technologies. Although extensive research activity has been devoted recently to exploring the physical properties, especially focusing on ferroelectricity and antiferromagnetism in chemically modified BiFeO3, a concrete understanding of the magnetoelectric coupling is yet to be fulfilled. We have discovered that La substitutions at the Bi-site lead to a progressive increase in the degeneracy of the potential energy landscape of the BiFeO3 system exemplified by a rotation of the polar axis away from the < 111 > (pc) towards the < 112 > (pc) discretion. This is accompanied by corresponding rotation of the antiferromagnetic axis as well, thus maintaining the right-handed vectorial relationship between ferroelectric polarization, antiferromagnetic vector and the Dzyaloshinskii-Moriya vector. As a consequence, La-BiFeO3 films exhibit a magnetoelectric coupling that is distinctly different from the undoped BiFeO3 films. BiFeO3 has a wide application but the impact of rare-earth substitution for the evolution of the coupling mechanism is unknown. Here, the authors reveal the correlation between ferroelectricity, antiferromagnetism, a weak ferromagnetic moment, and their switching pathways in La-substituted BiFeO3.
Possible absence of critical thickness and size effect in ultrathin perovskite ferroelectric films
(2017-06-06)
Gao, Peng
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Zhang, Zhangyuan
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Li, Mingqiang
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Ishikawa, Ryo
;
Feng, Bin
Although the size effect in ferroelectric thin films has been known for long time, the underlying mechanism is not yet fully understood and whether or not there is a critical thickness below which the ferroelectricity vanishes is still under debate. Here, we directly measure the thickness-dependent polarization in ultrathin PbZr0.2Ti0.8O3 films via quantitative annular bright field imaging. We find that the polarization is significantly suppressed for films <10-unit cells thick (similar to 4 nm). However, approximately the polarization never vanishes. The residual polarization is similar to 16 mu Ccm(-2) (similar to 17%) at 1.5-unit cells (similar to 0.6 nm) thick film on bare SrTiO3 and similar to 22 mu Ccm(-2) at 2-unit cells thick film on SrTiO3 with SrRuO3 electrode. The residual polarization in these ultrathin films is mainly attributed to the robust covalent Pb-O bond. Our atomic study provides new insights into mechanistic understanding of nanoscale ferroelectricity and the size effects.
Pulsed laser deposition of complex oxide heteroepitaxy
(2019-08-01)
Huang, Yen-Lin
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Liu, Heng-Jui
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Ma, Chun-Hao
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Yu, Pu
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Chu, Ying-Hao
The modern studies of complex oxides have been mainly driven by the development of advanced growth and characterization techniques, which provide researchers unprecedented access to new insights and functionalities of these materials. Epitaxial growth of thin films and related architectures offers a pathway to the discovery and stabilization of a wide spectrum of new possibilities in conjunction with the availability of high quality materials that produced with larger lateral sizes and being grown constrainedly. Compared with conventional growth techniques, such as sputtering, spin coating, sol-gel processes, metal-organic chemical vapor deposition, molecular beam epitaxy and so on, no other single advance in the creation of oxide materials has had as pronounced an impact as pulsed laser deposition. In pursuit of the fruitful functionalities and exciting physical phenomena among complex oxides, pulsed laser deposition technique has played an important role to fulfill the flurry of complex oxides in recent decades. In this article, we focus on the details of the growth of epitaxial oxide thin films and the related polymorphs, as well as recent advances in control of the oxide heteroepitaxy via pulsed laser deposition.
SARSA: a web tool for structural alignment of RNA using a structural alphabet
(2008-07-01)
Chang, Yen-Fu
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Huang, Yen-Lin
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Lu, Chin Lung
;
生物科技學系
;
生物資訊及系統生物研究所
SARSA is a web tool that can be used to align two or more RNA tertiary structures. The basic idea behind SARSA is that we use the vector quantization approach to derive a structural alphabet (SA) of 23 nucleotide conformations, via which we transform RNA 3D structures into 1D sequences of SA letters and then utilize classical sequence alignment methods to compare these 1D SA-encoded sequences and determine their structural similarities. In SARSA, we provide two RNA structural alignment tools, PARTS for pairwise alignment of RNA tertiary structures and MARTS for multiple alignment of RNA tertiary structures. Particularly in PARTS, we have implemented four kinds of pairwise alignments for a variety of practical applications: (i) global alignment for comparing whole structural similarity, (ii) semiglobal alignment for detecting structural motifs, (iii) local alignment for finding locally similar substructures and (iv) normalized local alignment for eliminating the mosaic effect of local alignment. Both tools in SARSA take as input RNA 3D structures in the PDB format and in their outputs provide graphical display that allows the user to visually view, rotate and enlarge the superposition of aligned RNA molecules. SARSA is available online at http://bioalgorithm.life.nctu.edu.tw/SARSA/.
SoRT(2): a tool for sorting genomes and reconstructing phylogenetic trees by reversals, generalized transpositions and translocations
(2010-07-01)
Huang, Yen-Lin
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Huang, Chen-Cheng
;
Tang, Chuan Yi
;
Lu, Chin Lung
;
生物科技學系
SoRT(2) is a web server that allows the user to perform genome rearrangement analysis involving reversals, generalized transpositions and translocations (including fusions and fissions), and infer phylogenetic trees of genomes being considered based on their pairwise genome rearrangement distances. It takes as input two or more linear/circular multi-chromosomal gene (or synteny block) orders in FASTA-like format. When the input is two genomes, SoRT(2) will quickly calculate their rearrangement distance, as well as a corresponding optimal scenario by highlighting the genes involved in each rearrangement operation. In the case of multiple genomes, SoRT(2) will also construct phylogenetic trees of these genomes based on a matrix of their pairwise rearrangement distances using distance-based approaches, such as neighbor-joining (NJ), unweighted pair group method with arithmetic mean (UPGMA) and Fitch-Margoliash (FM) methods. In addition, if the function of computing jackknife support values is selected, SoRT(2) will further perform the jackknife analysis to evaluate statistical reliability of the constructed NJ, UPGMA and FM trees. SoRT(2) is available online at http://bioalgorithm.life.nctu.edu.tw/SORT2/.
Sorting by Reversals, Generalized Transpositions, and Translocations Using Permutation Groups
(2010-05-01)
Huang, Yen-Lin
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Lu, Chin Lung
;
生物資訊及系統生物研究所
;
Institude of Bioinformatics and Systems Biology
In this article, we consider the problem of sorting a linear/circular, multi-chromosomal genome by reversals, block-interchanges (i.e., generalized transpositions), and translocations (including fusions and fissions) where the used operations can be weighted differently, which aims to find a sequence of reversal, block-interchange, and translocation operations such that the sum of these operation weights in the sequence is minimum. It is known that this sorting problem can be solved in polynomial time on the basis of breakpoint graphs, when block-interchanges are weighted 2 (or >= 3) and the others are weighted 1. In this study, we design a novel and easily implemented algorithm for this problem by utilizing the permutation group theory in algebra.
Space- and Time-Resolved Mapping of Ionic Dynamic and Electroresistive Phenomena in Lateral Devices
(2013-08-01)
Strelcov, Evgheni
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Jesse, Stephen
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Huang, Yen-Lin
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Teng, Yung-Chun
;
Kravchenko, Ivan I.
A scanning probe microscopy-based technique for probing local ionic and electronic transport and their dynamic behavior on the 10 ms to 10 s scale is presented. The time-resolved Kelvin probe force microscopy (tr-KPFM) allows mapping of surface potential in both space and time domains, visualizing electronic and ionic charge dynamics and separating underlying processes based on their time responses. Here, tr-KPFM is employed to explore the interplay of the adsorbed surface ions and bulk oxygen vacancies and their role in the resistive switching in a Ca-substituted bismuth ferrite thin film.
Spin filtering of a termination-controlled LSMO/Alq(3) heterojunction for an organic spin valve
(2017-09-21)
Lam, Tu-Ngoc
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Huang, Yen-Lin
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Weng, Ke-Chuan
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Lai, Yu-Ling
;
Lin, Ming-Wei
La1-xSrxMnO3 (LSMO) is weLL known as an efficient spin-injection electrode in ferromagnetic organic hybrid-based organic spin valves (OSV). Herein, we examine the influence of three terminating Layers of LSMO fiLms (mixed-, MnO2-, and LaSrO- (LSO-) terminated) on the spin filter at the bottom interface of tri (8-hydroxyquinoLine) aluminum (ALq(3)) deposited on these substrates. Angle-dependent X-ray photoelectron spectra (XPS) demonstrated the presence of SrO segregation at the outermost Layer for three types of LSMO fiLms but in different amounts that might contribute to their magnetic properties. A weak surface coupling between LSMO and Alq(3) was obtained through a small increase of Mn L-edge X-ray magnetic circular dichroism (XMCD) but it does not vary the bulk magnetic properties of LSMO fiLms upon Alq(3) adsorption (LSMO/Alq(3)). The surface dipoles due to the interaction between LSMO fiLms and Alq(3) were found to be 0.5, 0.5, and 0.7 eV for the mixed-ter/Alq(3), MnO2-ter/Alq(3), and LSO-ter/Alq(3) interfaces, respectively. Our results indicate that the segregated SrO Layer Ways an important role in the surface electronic and magnetic properties at LSMO/Alq(3) interfaces, which contributes to a fundamental understanding of the spin injection and transport in LSMO-Alq(3) hybrid-based OSV devices.
Tunable photoelectrochemical performance of Au/BiFeO3 heterostructure
(2016)
Huang, Yen-Lin
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Chang, Wei Sea
;
Chien Nguyen Van
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Liu, Heng-Jui
;
Tsai, Kai-An
Ferroelectric photoelectrodes, other than conventional semiconductors, are alternative photo-absorbers in the process of water splitting. However, the capture of photons and efficient transfer of photo-excited carriers remain as two critical issues in ferroelectric photoelectrodes. In this work, we overcome the aforementioned issues by decorating the ferroelectric BiFeO3 (BFO) surface with Au nanocrystals, and thus improving the photoelectrochemical (PEC) performance of BFO film. We demonstrate that the internal field induced by the spontaneous polarization of BFO can (1) tune the efficiency of the photo-excited carriers\' separation and charge transfer characteristics in bare BFO photoelectrodes, and (2) modulate an extra optical absorption within the visible light region, created by the surface plasmon resonance excitation of Au nanocrystals to capture more photons in the Au/BFO heterostructure. This study provides key insights for understanding the tunable features of PEC performance, composed of the heterostructure of noble metals and ferroelectric materials.
Unexpected Giant Microwave Conductivity in a Nominally Silent BiFeO3 Domain Wall
(1970-01-01)
Huang, Yen-Lin
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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.