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Development and verification of the coaxial heterogeneous hyperspectral system for the Wax Apple tree
(2019-01-01)
Li, Yi-Sheng
;
Yan, Yung-Jhe
;
Shih, Ruei-Siang
;
Chang, Chao-Hsin
;
Chen, Tzung-Cheng
This paper presents the design of the coaxial heterogeneous hyperspectral system, concurrently sensing for the visible (YES) light and short-wave infrared (SWIR) light wavelengths under the same space axis. By the designed mechanism, this hyperspectral system can provide more hands and broader wavelengths in every scan. The adequate spectral information of the target makes the analysis more comprehensive. For this hyperspectral system, the spatial correction and spectral correction are required. The spatial correction deals with the spatial match between the VIS and SWIR data. Moreover, the spectral correction is to eliminate the different response of the YES and SWIR sensor. The purpose of these corrections was to verify the design and provide the accurate reflection spectrum.
Giant Resistivity Change of Transparent ZnO/Muscovite Heteroepitaxy
(2020-05-13)
Yen, Min
;
Lai, Yu-Hong
;
Zhang, Chun-Li
;
Cheng, Hou-Yung
;
Hsieh, Yi-Ting
The piezoresistive effect has shown a remarkable potential for mechanical sensor applications and been sought for its excellent performance. A great attention was paid to the giant piezoresistive effect and sensitivity delivered by silicon-based nanostructures. However, low thermal stability and complicated fabrication process hinder their practical applications. To overcome these issues and enhance the functionalities, we envision the substantial piezopotential in a zinc oxide (ZnO)/muscovite (mica) heteroepitaxy system based on theoretical consideration and realize it in practice. High piezoresistive effect with giant change of resistivity (-80 to 240%) and large gauge factor (>1000) are demonstrated through mechanical bending. The detailed features of heteroepitaxy, electrical transport, and strain are probed to understand the mechanism of such a giant resistivity change. In addition, a bending model is established to reveal the distribution of strain. Finally, we demonstrate a flex sensor featuring high sensitivity, optical transparency, and two-segment sensing with a great potential toward practical applications. Such an oxide heteroepitaxy exhibits excellent piezoresistive properties and mechanical flexibility. In the near future, the importance of flex sensors will emerge because of the precise control in the automation industries, and our results lead to a new design in the field of flex sensors.
UAV 3D modeling with multi-spectral imaging: An example of wax apple tree
(2019-01-01)
Shih, Ruei-Siang
;
Li, Yi-Sheng
;
Yan, Yung-Jhe
;
Yu, Chun
;
Huang, Wei-Tsang
As the Unmanned aerial vehicle (UAV) become ubiquitous, many early studies utilizing the UAV for three-dimensional (3D) modeling system are successively proposed as well. The advantage of using UAV successfully advances efficiency and reduces the cost time for simplifying the process of collecting data. Moreover, the characteristics of the light sized and suspension of new designed UAV could allow the users to gather the precise data from the rugged terrain and through a crowd of trees and may build a detail 3D and hyperspectral images. By those high-resolution 3D model data, the texture and shape of observation can be seen and brings research into further analysis. However, there are some limits that the information of 3D modeling data in RGB wide bands is not adequate to investigate vegetation research. The hyper spectrum collects the information of tens of bands with the narrow bandwidth could analyze the detail difference between abnormal and normal situations when the plant is growing. Therefore, how to combine hyperspectral data into a 3D modeling system would be important when researches want to attain the location data and spectral image simultaneously. In this study, the UAV will be loaded with two kinds of systems, and try to build the model include 3D modeling information and spectral information. As a result, it can monitor the growth condition of plants, their environment, also the precise location at the same time so that it can make vegetation analysis more complete.
Oxide Heteroepitaxy-Based Flexible Ferroelectric Transistor
(2019-07-24)
Tsai, Meng-Fu
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Jiang, Jie
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Shao, Pao-Wen
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Lai, Yu-Hong
;
Chen, Jhih-Wei
With the rise of Internet of Things, the presence of flexible devices has attracted significant attention owing to design flexibility. A ferroelectric field-effect transistor (FeFET), showing the advantages of high speed, nondestructive readout, and low-power consumption, plays a key role in next-generation technology. However, the performance of these devices is restricted since conventional flexible substrates show poor thermal stability to integrate traditional ferroelectric materials, limiting the compatibility of wearable devices. In this study, we adopt flexible muscovite mica as a substrate due to its good thermal properties and epitaxial integration ability. A flexible FeFET composed of oxide heteroepitaxy on muscovite is realized by combining an aluminum-doped zinc oxide film as the semiconductor channel layer and a Pb(Zro7Ti0.3)03 film as the ferroelectric gate dielectric. The excellent characteristics of the transistor together with superior thermal stability and mechanical flexibility are demonstrated through various mechanical bending and temperature measurements. The on/off current ratio of the FeFET is higher than 103, which based on the field effect in the transfer curve. The smallest bending radius that can be achieved is 5 mm with a cyclability of 300 times and a retention of 100 h. This study opens an avenue to use oxide heteroepitaxy to construct a FeFET for next-generation flexible electronic systems.
Deterministic optical control of room temperature multiferroicity in BiFeO3 thin films
(2019-06-01)
Liou, Yi-De
;
Chiu, Yu-You
;
Hart, Ryan Thomas
;
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.
Poly(vinyl alcohol)-controlled synthesis of monodispersed crosslinked poly(methyl methacrylate) microparticles with significantly improved mechanical properties
(2019-07-01)
Kao, Yu-Chen
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Chen, Chun-Hua
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Whang, Wha-Tzong
;
Chen, Yi-Chun
;
Chen, Kai-Chi
A facile synthesis concept focusing on the poly(vinyl alcohol) (PVA) concentration induced interfacial energy effects in seed swelling polymerization was realized for the successful fabrication of a series of monodispersed poly(methyl methacrylate) (PMMA) microparticles with four crosslinking agents, 2,2-bis[(methacryloyloxy)methyl]butyl methacrylate, 1,2-ethanediyl bis(2-methylacrylate), 1,3-divinylbenzene and 1,2-ethanediyl diacetate. We revealed a special role of PVA in regulating the diffusion of crosslinking agents as well as the swelling degree of latex seeds and, more noticeably, the consequent improved mechanical properties of the crosslinked PMMA microparticles formed. The highest recovery rate obtained from the PMMA microparticles with 0.6 wt% PVA approached 67%, which is higher than or comparable to reported values. This work not only developed a new facile synthesis approach for producing highly uniform tough crosslinked PMMA microparticles for more potential applications but also provided valuable insights into fundamental aspects of seed swelling polymerization. (c) 2019 Society of Chemical Industry
Epitaxial AlN on c-plane sapphire by plasma nitriding
(2019-06-01)
Chen, Yi-Chun
;
Chang, Li
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材料科學與工程學系
;
Department of Materials Science and Engineering
Nitridation of sapphire to form epitaxial AlN by microwave plasma containing nitrogen gas has been investigated to be an efficient process. Structural characterization with chemical analysis by X-ray diffraction and X-ray photoelectron spectroscopy shows that an epitaxial AlN film containing oxygen can form on sapphire by using pure nitrogen plasma. Furthermore, nitridation with N-2/H-2 plasma not only improves the crystallinity of the epitaxial AlN film without oxygen, but also significantly increases the nitridation rate to 9 nm min(-1), resulting in 270 nm thick AlN for 30 min plasma nitriding. (C) 2019 The Japan Society of Applied Physics
Electrical polarization induced by atomically engineered compositional gradient in complex oxide solid solution
(2019-04-12)
Wu, Ping-Chun
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Huang, Rong
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Hsieh, Ying-Hui
;
Wang, Bo
;
Yen, Min
Control of inhomogeneity in materials in order to avoid unexpected effects to the system remains a challenge. In this study, we seek to engineer inhomogeneity in materials and anticipate new properties. Through precise control of composition at the atomic scale, an electrical polarization is induced in the composition-graded LaAIO(3)-SrTiO3 solid solution epitaxially deposited on NdGaO3 substrates. By tailoring the direction of compositional gradient, the relationship between structure and electrical polarization is simulated via phase-field modeling and revealed by a combination of scanning transmission electron microscopy and scanning probe microscopy. The analysis of the results indicates that the induced polarization is due to the flexoelectric effect in the compositional gradient system. The results of this study provide a new pathway for obtaining a new material genome. Moreover, by a suitable design of the new genome, that is, by using different combinations of compositional gradient geometries, local conduction can be obtained and manipulated, providing a new approach to obtain the desired properties.
Tetragonal BiFeO3 on yttria-stabilized zirconia
(2015-11-01)
Liu, Heng-Jui
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Du, Yu-Hao
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Gao, Peng
;
Huang, Yen-Chin
;
Chen, Hsiao-Wen
High structural susceptibility of multiferroic BiFeO3 (BFO) makes it a potential replacement of current Pb-based piezoelectrics. In this study, a tetragonal phase is identified based on a combination of x-ray diffraction, scanning transmission electronic microscopy, x-ray absorption spectroscopy, and Raman spectroscopy when BFO is grown on yttria-stabilized zirconia (YSZ) substrates. To distinguish the discrepancy between this tetragonal phase and common cases of monoclinic BFO, piezoelectric force microscopy images and optical property are also performed. It shows a lower electrostatic energy of ferroelectric domains and a large reduction of band gap for BFO grown on YSZ substrate comparing to the well-known one grown on LaAlO3 substrate. Our findings in this work can provide more insights to understand the structural diversity of multiferroic BFO system for further applications. (C) 2015 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported License.
Magnetic-coupled phase anomaly in mixed-phase BiFeO3 thin films
(2017-08-01)
Huang, Yen-Chin
;
Liou, Yi-De
;
Liu, Heng-Jui
;
Lee, Hsin-Hua
;
Chen, Yi-Chun
The rich phase diagram of rhombohedral (R)-like and tetragonal (T)-like monoclinic polymorph in strained BiFeO3 (BFO) films brings on various functionalities. Finding correlations of physical ordering parameters in this system is generally difficult because T-like and R-like phases are undistinguishable in many aspects. In this study, the magnetic-coupled structural transitions of the mixed-phase BFO at low temperatures were investigated by atomic force microscopy (AFM), X-ray diffraction (XRD), and Raman spectroscopy. To resolve the complexity resulted from the similarity between T-like and R-like phases, we analyzed the Raman spectra on a micro-scale region with various T/R ratios, which is in situ manipulated by an AFM tip carrying a dc bias. Phonons of T-like and R-like phases were thus successfully separated. Based on temperature-dependent XRD and resolved Raman spectra, we observed two isostructural transitions at around 225 K and 150 K, and they are strongly correlated with the magnetic ordering in the mixed-phase BFO film. Moreover, through the effective spin-lattice coupling, the evolution of the T/R polymorph is changed by the magnetic cooling process at low temperatures. This study provides a pathway to modulate phonon behaviors by magnetic fields in a highly strained system. (C) 2017 Author(s).

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