Browsing by Author "Wu, Ping-Chun"

Now showing 1 - 11 of 11

A Fast Route Towards Freestanding Single-Crystalline Oxide Thin Films by Using YBa(2)Cu(3)O(7-x)as a Sacrificial Layer
(2020-08-28)
Chang, Yao-Wen
;
Wu, Ping-Chun
;
Yi, Jhih-Bang
;
Liu, Yu-Chen
;
Chou, Yi
Researchers have long been seeking multifunctional materials that can be adopted for next-generation nanoelectronics, and which, hopefully, are compatible with current semiconductor processing for further integration. Along this vein, complex oxides have gained numerous attention due to their versatile functionalities. Despite the fact that unbounded potential of complex oxides has been examined over the past years, one of the major challenges lies in the direct integration of these functional oxides onto existing devices or targeted substrates that are inherently incompatible in terms of oxide growth. To fulfill this goal, freestanding processes have been proposed, in which wet etching of inserted sacrificial layers is regarded as one of the most efficient ways to obtain epitaxial high-quality thin films. In this study, we propose using an alternative oxide, YBa2Cu3O7(YCBO), as a sacrificial layer, which can be easily dissolved in light hydrochloric acid in a more efficient way, while protecting selected complex oxides intact. The high epitaxial quality of the selected complex oxide before and after freestanding process using YBCO as a sacrificial layer is comprehensively studied via a combination of atomic force microscopy, X-ray diffraction, transmission electron microscopy, and electrical transports. This approach enables direct integration of complex oxides with arbitrary substrates and devices and is expected to offer a faster route towards the development of low-dimensional quantum materials.
A Simple Fiber Bragg Grating-Based Sensor Network Architecture with Self-Protecting and Monitoring Functions
(2011-02-01)
Yeh, Chien-Hung
;
Chow, Chi-Wai
;
Wu, Ping-Chun
;
Tseng, Fan-Gang
;
光電工程學系
A novel fiber Bragg grating (FBG)-based passive sensor architecture, which can be used to protect the fiber cut and monitor the multiple sensors simultaneously, is proposed and experimentally demonstrated. Here, we employ a wavelength-tunable erbium-doped fiber (EDF) laser scheme with 25 km cavity length acting as the detecting light source in central office (CO). Each FBG sensor, serving as a feedback element, is used in proposed sensor architecture. By tuning the tunable bandpass filter (TBF) placing inside cavity to match the corresponding Bragg wavelength of FBG over the amplification bandwidth, we can retrieve the related wavelength lasing for the FBG sensing and monitoring simultaneously. Moreover, the survivability and capacity of the passive FBG sensor architecture can be also enhanced.
Development of oxide heteroepitaxy for soft technology
(2018-06-21)
Wu, Ping-Chun
;
Chu, Ying-Hao
;
材料科學與工程學系
;
電子物理學系
;
Department of Materials Science and Engineering
Soft technology has been an emerging field since flexible and wearable electronics started flourishing. In this research field, oxides can play an important role due to their intriguing functionalities and superior thermal and chemical stabilities. To deliver high-quality thin films or structures based on oxides, heteroepitaxy is essential. However, the lack of a suitable approach remains an obstacle for flexible oxide heteroepitaxy. Recently, due to the advancement of growth facilities and characterization tools, various techniques have been employed to acquire flexible oxide heteroepitaxy. This review highlights the methods as well as direct and indirect approaches that are essential for developing oxide heteroepitaxy with mechanical flexibility. We also provide an overview, classifying the fields in terms of applications involving flexible oxide heteroepitaxy and the development of oxide-based approaches.
Electrical polarization induced by atomically engineered compositional gradient in complex oxide solid solution
(2019-04-12)
Wu, Ping-Chun
;
Huang, Rong
;
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.
Epitaxial Yttria-Stabilized Zirconia on Muscovite for Flexible Transparent Ionic Conductors
(2018-12-01)
Wu, Ping-Chun
;
Lin, Yu-Pin
;
Juan, Yung-Hsiang
;
Wang, Yao-Ming
;
Do Thi-Hien
The advantages of ionic conductors have attracted great interest worldwide because they can fit the requirements that standard electrical conductors struggle to meet. Yttria-stabilized zirconia (YSZ) is the most common ionic conductor for various practical applications. In this study, in order to bring ionic conductors into the field of soft technology, transparent YSZ films with superior mechanical flexibility were epitaxially grown on a muscovite substrate by pulsed-laser deposition. The epitaxial relationship between YSZ and muscovite has been well established, indicating a high-crystallinity thin film. The heterostructure of YSZ/muscovite exhibits excellent ionic conductivity with great mechanical flexibility. The smallest bending radius of this heterostructure that can be achieved is similar to 10 mm with excellent mechanical cyclabilty (>800 cycles) and stability (>10(5) s), serving as a new platform to fabricate highly flexible ionic conductors.
Heteroepitaxy of Fe3O4/Muscovite: A New Perspective for Flexible Spintronics
(2016-12-14)
Wu, Ping-Chun
;
Chen, Ping-Fan
;
Thi Hien Do
;
Hsieh, Ying-Hui
;
Ma, Chun-Hao
Spintronics has captured a lot of attention since it was proposed. It has been triggering numerous research groups to make their efforts on pursuing spin-related electronic devices. Recently, flexible and wearable devices are in a high demand due to their outstanding potential in practical applications. In order to introduce spintronics into the realm of flexible devices, we demonstrate that it is feasible to grow epitaxial Fe3O4 film, a promising candidate for realizing spintronic devices based on tunneling magnetoresistance, on flexible muscovite. In this study, the heteroepitaxy of Fe3O4/muscovite is characterized by X-ray diffraction, high-resolution transmission electron microscopy, and Raman spectroscopy. The chemical composition and magnetic feature are investigated by a combination of X-ray photoelectron spectroscopy and X-ray magnetic circular dichroism. The electrical and magnetic properties are examined to show the preservation of the primitive properties of Fe3O4. Furthermore, various bending tests are performed to show the tunability of functionalities and to confirm that the heterostructures retain the physical properties under repeated cycles. These results illustrate that the Fe3O4/muscovite heterostructure can be a potential candidate for the applications in flexible spintronics.
Magnetic Mesocrystal-Assisted Magnetoresistance in Manganite
(2014-11-01)
Yang, Jan-Chi
;
He, Qing
;
Zhu, Yuan-Min
;
Lin, Jheng-Cyuan
;
Liu, Heng-Jui
Mesocrystal, a new class of crystals as compared to conventional and well-known single crystals and polycrystalline systems, has captured significant attention in the past decade. Recent studies have been focused on the advance of synthesis mechanisms as well as the potential on device applications. In order to create further opportunities upon functional mesocrystals, we fabricated a self-assembled nanocomposite composed of magnetic CoFe2O4 mesocrystal in Sr-doped manganites. This combination exhibits intriguing structural and magnetic tunabilities. Furthermore, the antiferromagnetic coupling of the mesocrystal and matrix has induced an additional magnetic perturbation to spin-polarized electrons, resulting in a significantly enhanced magnetoresistance in the nanocomposite. Our work demonstrates a new thought toward the enhancement of intrinsic functionalities assisted by mesocrystals and advanced design of novel mesocrystal-embedded nanocomposites.
Measurement of Organic Chemical Refractive Indexes Using an Optical Time-Domain Reflectometer
(2012-01-01)
Yeh, Chien-Hung
;
Chow, Chi-Wai
;
Sung, Jiun-Yu
;
Wu, Ping-Chun
;
Whang, Wha-Tzong
In this investigation, we propose and experimentally demonstrate a method for measuring the refractive index (RI) of liquid organic chemicals. The scheme is based on a single-mode fiber (SMF) sensor and an optical time-domain reflectometer (OTDR). Here, due to the different reflectance (R) between the SMF and organic liquid chemicals, the reflected power level of the backscattering light (BSL) measured by the OTDR would be different. Therefore, we can measure the RI of chemical under test via the measured BSL level. The proposed RI sensor is simple and easy to manipulate, with stable detected signals, and has the potential to be a valuable tool for use in biological and chemical applications.
Thickness dependence of transport behaviors in SrRuO3 /SrTiO3 superlattices
(2020-01-03)
Wu, Ping-Chun
;
Song, Haili
;
Yuan, Ye
;
Feng, Bin
;
Ikuhara, Yuichi
Ultrathin oxide films have attracted considerable attention due to the potential for the integration of next-generation devices. However, the transport behaviors of the ultrathin oxide films are yet to be explored due to the high resistance caused by the strong influence of the interface and substrates. In this paper, an attempt is made to engineer the transport behaviors in ultrathin oxides. To exclude the high-resistance issue, conductive SrRuO3 with thickness down to two unit cells is embedded in insulating SrTiO3 in the form of superlattices. With precise control of the thickness in each layer, the transport behaviors, as well as the anomalous Hall effects, in SrRuO3 can be systematically manipulated. The analysis indicates that the diversity of the anomalous Hall effects is attributed to the change of Berry curvatures. The results give a pathway to the control of physical properties in ultrathin oxide systems by thickness engineering.
Transparent Antiradiative Ferroelectric Heterostructure Based on Flexible Oxide Heteroepitaxy
(2018-09-12)
Ma, Chun-Hao
;
Jiang, Jie
;
Shao, Pao-Wen
;
Peng, Qiang-Xiang
;
Huang, Chun-Wei
In the era of Internet of Things, the demand for flexible and transparent electronic devices has shifted to the forefront of materials science research. However, the radiation damage to key performance of transparent devices under radiative environment remains as a critical issue. Here, we present a promising technology for nonvolatile transparent electronic devices based on flexible oxide heteroepitaxy. A direct fabrication of epitaxial lead lanthanum zirconate titanate on transparent flexible mica substrate with indium tin oxide electrodes is presented. The transparent flexible ferroelectric heterostructures not only retain their superior performance, thermal stability, reliability, and mechanical durability, but also exhibit remarkably robust properties against to a strong radiation exposure. Our study demonstrates an extraordinary concept to realize transparent flexible nonvolatile electronic devices for the design and development of next-generation smart devices with potential application in electronics, automotive, aerospace, and nuclear systems.
Tunable disorder and localization in the rare-earth nickelates
(2019-05-02)
Wang, Changan
;
Chang, Ching-Hao
;
Huang, Angus
;
Wang, Pei-Chun
;
Wu, Ping-Chun
We demonstrate that transport in metallic rare-earth nickelates can be engineered by directly tuning the electronic mean free path. Using irradiation as a tool to induce disorder, we drive this system from a metallic phase into an Anderson insulator. This proceeds via an intermediate regime which shows a thermal crossover from insulating to metallic behavior. We argue that this phase falls within the paradigm of weak localization in three dimensions. We develop a theoretical model for the temperature dependence of resistivity which shows good agreement with our data. The three-dimensional weak localization picture is supported by magnetoconductivity, which scales as similar to B-2 up to several tesla. Interestingly, our data indicate that this phase lies in the Mott-Ioffe-Regel regime with the mean free path approaching the lattice constant. Upon further increasing disorder, the charge carriers are localized, leading to insulating behavior at all temperatures. Our results show that irradiation provides a "clean" tuning knob for the mean free path, without altering other system parameters. This suggests promising directions for studies of Anderson localization.