Browsing by Author "Chen, Jui-Yuan"

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Applications of p-n homojunction ZnO nanowires to one-diode one-memristor RRAM arrays
(2020-10-01)
Chen, Jui-Yuan
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Wu, Min-Ci
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Ting, Yi-Hsin
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Lee, Wei-Che
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Yeh, Ping-Hung
Nanowire (NW) structure is superior at defining the direction of device due to its one-dimension feature. In this work, the p-n ZnO NWs were successfully synthesized, and were able to vertically grow on Ta2O5 substrate. Thus, the well-performed Au/p-n ZnO NWs/Ta2O5/Au one-diode one-memoristor device was fabricated. The p-n ZnO NWs not only exhibited excellent rectifying behavior, but also played the role of oxygen storing during filaments formation. Therefore, the low-leakage device aimed to build high-density crossbar arrays which was required for accelerating the combination of 5 G with AI in near future applications. (C) 2020 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
Atomic Imaging of Molybdenum Oxide Nanowires with Unique and Complex Periodicity by Advanced Electron Microscopy
(2020-03-11)
Ting, Yi-Hsin
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Huang, Chun-Wei
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Yasuhara, Akira
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Chen, Sheng-Yuan
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Chen, Jui-Yuan
Crystalline Mo5O14 exhibits distinctive structural features such as tunnel structure and pseudolamellar arrangement according to the ideal model. However, the spatial resolution of the conventional technique of transmission electron microscopy (TEM) is insufficient to distinguish the actual positions of atoms. In this work, we aimed to systematically analyze and identify the Mo5O14 nanowires fabricated by the chemical vapor deposition (CVD) process. Utilizing high-angle annular dark-field (HAADF), annular bright-field (ABF), and enhanced annular bright-field (E-ABF) within the scanning transmission electron microscope (STEM) mode reveals the structural features at the atomic scale. In addition, the ultrahigh resolution images have confirmed the crystallographic insights in [001] growth direction for the Mo5O14 nanowires with a tunnel structure throughout the nanowire. The cross-sectional images show the unique close-packed plane and atomic arrangement with a network of MoO6 octahedra and MoO7 pentagonal bipyramids. These results are consistent with the theoretical atomic arrangement, supporting the realization of Mo5O14-type catalysts used in the selective oxidation process and battery applications.
Copper silicide/silicon nanowire heterostructures: in situ TEM observation of growth behaviors and electron transport properties
(2013)
Chiu, Chung-Hua
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Huang, Chun-Wei
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Chen, Jui-Yuan
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Huang, Yu-Ting
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Hu, Jung-Chih
Copper silicide has been studied in the applications of electronic devices and catalysts. In this study, Cu3Si/Si nanowire heterostructures were fabricated through solid state reaction in an in situ transmission electron microscope (TEM). The dynamic diffusion of the copper atoms in the growth process and the formation mechanism are characterized. We found that two dimensional stacking faults (SF) may retard the growth of Cu3Si. Due to the evidence of the block of edge-nucleation (heterogeneous) by the surface oxide, center-nucleation (homogeneous) is suggested to dominate the silicidation. Furthermore, the electrical transport properties of various silicon channel length with Cu3Si/Si heterostructure interfaces and metallic Cu3Si NWs have been investigated. The observations not only provided an alternative pathway to explore the formation mechanisms and interface properties of Cu3Si/Si, but also suggested the potential application of Cu3Si at nanoscale for future processing in nanotechnology.
Direct Observation of Dual-Filament Switching Behaviors in Ta2O5-Based Memristors
(2017-04-18)
Chang, Chia-Fu
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Chen, Jui-Yuan
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Huang, Chun-Wei
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Chiu, Chung-Hua
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Lin, Ting-Yi
Direct observation of melting behaviors at the nanoscale under electron beam and heat to form hollow nanostructures
(2012)
Huang, Chun-Wei
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Hsin, Cheng-Lun
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Wang, Chun-Wen
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Chu, Fu-Hsuan
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Kao, Chen-Yen
"We report the melting behaviours of ZnO nanowire by heating ZnO-Al2O3 core-shell heterostructures to form Al2O3 nanotubes in an in situ ultrahigh vacuum transmission electron microscope (UHV-TEM). When the ZnO-Al2O3 core-shell nanowire heterostructures were annealed at 600 degrees C under electron irradiation, the amorphous Al2O3 shell became single crystalline and then the ZnO core melted. The average vanishing rate of the ZnO core was measured to be 4.2 nm s(-1). The thickness of the Al2O3 nanotubes can be precisely controlled by the deposition process. Additionally, the inner geometry of nanotubes can be defined by the initial ZnO core. The result shows a promising method to obtain the biocompatible Al2O3 nanotubes, which may be applied in drug delivery, biochemistry and resistive switching random access memory (ReRAM)."
Direct Observation of Sublimation Behaviors in One-Dimensional In2Se3/In2O3 Nanoheterostructures
(2015-06-02)
Hsin, Cheng-Lun
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Huang, Chun-Wei
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Chen, Jui-Yuan
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Liao, Kuo-Cheng
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Liu, Po-Liang
Recently, in situ transmission electron microscopy (TEM) has provided a route to analyze structural characterization and chemical evolution with its powerful and unique applications. In this paper, we disclose the detailed phenomenon of sublimation on the atomic scale. In2Se3/In2O3 nanowires were synthesized via the vapor-liquid-solid mechanism and studied in an ultra-high-vacuum (UHV) TEM at high temperature in real time. During in situ observation of the sublimation process of the nanowires, the evolution and reconstruction of the exposed In2Se3 surface progressed in different manners with time. The surface structure was decomposed by mass-desorption and stepwise-migration processes, which are also energetically favored processes in the ab initio calculation. This study developed a new concept and will be essential in the development of atomic kinetics.
Dynamic Evolution of Conducting Nanofilament in Resistive Switching Memories
(2013-08-01)
Chen, Jui-Yuan
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Hsin, Cheng-Lun
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Huang, Chun-Wei
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Chiu, Chung-Hua
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Huang, Yu-Ting
Resistive random access memory (ReRAM) has been considered the most promising next-generation nonvolatile memory. In recent years, the switching behavior has been widely reported, and understanding the switching mechanism can improve the stability and scalability of devices. We designed an innovative sample structure for in situ transmission electron microscopy (TEM) to observe the formation of conductive filaments in the Pt/ZnO/Pt structure in real time. The corresponding current-voltage measurements help us to understand the switching mechanism of ZnO film. In addition, high-resolution transmission electron microscopy (HRTEM) and electron energy loss spectroscopy (EELS) have been used to identify the atomic structure and components of the filament/disrupted region, determining that the conducting paths are caused by the conglomeration of zinc atoms. The behavior of resistive switching is due to the migration of oxygen ions, leading to transformation between Zn-dominated ZnO1-x and ZnO.
Dynamic Observation of Phase Transformation Behaviors in Indium(III) Selenide Nanowire Based Phase Change Memory
(2014-09-01)
Huang, Yu-Ling
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Huang, Chun-Wei
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Chen, Jui-Yuan
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Ting, Yi-Hsin
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Lu, Kuo-Chang
Phase change random access memory (PCRAM) has been extensively investigated for its potential applications in next-generation nonvolatile memory. In this study, indium(III) selenide (In2Se3) was selected due to its high resistivity ratio and lower programming current. Au/In2Se3-nanowire/Au phase change memory devices were fabricated and measured systematically in an in situ transmission electron microscope to perform a RESET/SET process under pulsed and dc voltage swept mode, respectively. During the switching, we observed the dynamic evolution of the phase transformation process. The switching behavior resulted from crystalline/amorphous change and revealed that a long pulse width would induce the amorphous or polycrystalline state by different pulse amplitudes, supporting the improvement of the writing speed, retention, and endurance of PCRAM.
Dynamic observation on the growth behaviors in manganese silicide/silicon nanowire heterostructures
(2015-01-01)
Hsieh, Yu-Hsun
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Chiu, Chung-Hua
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Huang, Chun-Wei
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Chen, Jui-Yuan
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Lin, Wan-Jhen
Metal silicide nanowires (NWs) are very interesting materials with diverse physical properties. Among the silicides, manganese silicide nanostructures have attracted wide attention due to their several potential applications, including in microelectronics, optoelectronics, spintronics and thermoelectric devices. In this work, we exhibited the formation of pure manganese silicide and manganese silicide/silicon nanowire heterostructures through solid state reaction with line contacts between manganese pads and silicon NWs. Dynamical process and phase characterization were investigated by in situ transmission electron microscopy (in situ TEM) and spherical aberration corrected scanning transmission electron microscopy (Cs-corrected STEM), respectively. The growth dynamics of the manganese silicide phase under thermal effects were systematically studied. Additionally, Al2O3, serving as the surface oxide, altered the growth behavior of the MnSi nanowire, enhancing the silicide/Si epitaxial growth and effecting the diffusion process in the silicon nanowire as well. In addition to fundamental science, this significant study has great potential in advancing future processing techniques in nanotechnology and related applications.
Enhanced Reliability of In-Ga-ZnO Thin-Film Transistors Through Design of Dual Passivation Layers
(2018-07-01)
Abliz, Ablat
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Wan, Da
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Chen, Jui-Yuan
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Xu, Lei
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He, Jiawei
This paper investigates the effects of different passivation layers (PVLs) on the electrical performance and reliability of amorphous indium gallium zinc oxide (a-In-Ga-ZnO) thin film transistors (TFTs). By rational design, the fabricated a-InGaZnO TFT with hafnium oxide and aluminum oxide (HfO2/Al2O3) dual PVLs exhibits a field-effect mobility of 13.5 cm(2)/Vs, low sub threshold swing of 0.32 V/decade, and especially, small threshold voltage shifts of 0.5 (-0.6) V and 1.1 (-1.2) V under positive (negative) gate bias, and light illumination stress at the relative humidity of 40%. Furthermore, the a-In-Ga-ZnO TFTs with HfO2/Al2O3 dual PVLs maintain reasonable mobility and electrical performance even exposure to ambient condition for up to four months. This enhanced stability is attributed to the presence of high-quality HfO2/Al2O3 dual PVLs, which not only could suppress the photodesorption, reduce the total trap density and subgap photoexcitation behavior, but also protect the channel from environmental effects. Thus, the rational-designed HfO2/Al2O3 dual PVLs passivated a-In-Ga-ZnO TFTs with superior reliability represent a great step toward the achievement of long-term reliable zinc oxide-based oxide TFTs.
High on/off ratio black phosphorus based memristor with ultra-thin phosphorus oxide layer
(2019-11-04)
Wang, Yudan
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Wu, Facai
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Liu, Xingqiang
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Lin, Jun
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Chen, Jui-Yuan
The scaling down of switching media encounters high leakage current in the traditional oxide material based memristors, resulting in high power consumption of chips. Two-dimensional (2D) materials promise an ultimate device scaling down to atomic layer thickness. Herein, black phosphorus (BP) and its self-assembly phosphorous oxide (BP) memristors are constructed, which leverages the high on/off ratio operation of oxides and low leakage current of 2D materials with high performance. The memristors exhibit reproducible and reliable switching characteristics with the on/off ratio >10(7) and data retention >10(4) s. Depending on the high reproducibility, basic "AND" and "OR" gates have been constructed on flexible substrates. Moreover, on the basis of the symmetry and linearity of conductance in the devices, the neural network simulation for supervised learning presents an online learning accuracy of 91.4%. This work opens an avenue for future flexible electronics.
In Situ Analysis of Growth Behaviors of Cu2O Nanocubes in Liquid Cell Transmission Electron Microscopy
(2019-08-06)
Lin, Ya-Hsuan
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Chen, Jui-Yuan
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Chen, Fu-Chun
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Kuo, Ming-Yu
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Hsu, Yung-Jung
Metal oxides have attracted substantial attention over the years and are commonly used in the semiconductor industry because of their excellent physical and chemical properties. Among the various metal oxides, cuprous oxide (Cu2O) is regarded as a promising material. It is inexpensive, earth-abundant, and nontoxic; therefore, it can be used in catalysis, sensors, solar cells, and p-type semiconductors. However, the redox reaction of Cu2O is still uncertain. The size, morphology, and structure of Cu2O strongly influence its properties. In this work, we developed a new synthesis method of Cu2O that involves reducing the precursor by an electron beam without reducing agent. The growth process of Cu2O nanocubes was observed via in situ liquid cell transmission electron microscopy (in situ LCTEM). The nucleation kinetics, oscillating growth behavior, and redox reaction of the Cu2O nanocubes in the liquid phase were systematically studied. Cu2O exhibited a round shape at the beginning and transformed into a cubic shape afterward. Interestingly, the Cu2O nanocubes grew clearly under long-term observation; however, their diameters increased and fluctuated during the short-term observation. The electron beam not only stimulated the solution to reduce the nanocubes but also caused electron radiation effect to the nanocubes. During the Cu2O growth and dissolution, the cubic shape evolved with specific planes in the {100} family. Our direct observation sheds light on the preparation of Cu2O by a reduction method, extending the study of reaction kinetics and providing a new way to synthesize metal oxides.
In Situ Observation of Au Nanostructure Evolution in Liquid Cell TEM
(2017-11-23)
Chen, Ying-Chen
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Chen, Jui-Yuan
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Wu, Wen-Wei
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材料科學與工程學系
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Department of Materials Science and Engineering
Gold nanostructures (NSs) have been widely investigated due to their unique properties. Understanding their growth behaviors during synthesis will be beneficial in designing and applying to many functional nanodevices. It is important to enrich the fundamental science and technology of the synthesis and characterization through real time evolution. In this work, we observed the dynamic growth of Au NSs by using liquid in situ transmission electron microscopy (TEM). The solution was sealed in a liquid cell, and the results indicated that the thicker solution layer tended to form multi twinned decahedral NSs; in contrast, nanoplates easily formed in the thinner solution layer. The silver halide model, relying on side-face structures, and the Wulff construction can be used to explain the formation of NSs. Additionally, we analyzed the growth rate of different morphologies to elucidate their growth behaviors. The growth mechanism and formation kinetics of different shapes of Au NSs were systematically studied, which provided direct evidence toward and extended the study of reaction kinetics for modifying the morphology of NSs.
In Situ TEM and Energy Dispersion Spectrometer Analysis of Chemical Composition Change in ZnO Nanowire Resistive Memories
(2013-04-16)
Huang, Yu-Ting
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Yu, Shih-Ying
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Hsin, Cheng-Lun
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Huang, Chun-Wei
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Kang, Chen-Fang
Resistive random-access memory (ReRAM) has been of wide interest for its potential to replace flash memory in the next-generation nonvolatile memory roadmap. In this study, we have fabricated the Au/ZnO-nanowire/Au nanomemory device by electron beam lithography and, subsequently, utilized in situ transmission electron microscopy (TEM) to observe the atomic structure evolution from the initial state to the low-resistance state (LRS) in the ZnO nanowire. The element mapping of LRS showing that the nanowire was zinc dominant indicating that the oxygen vacancies were introduced after resistance switching. The results provided direct evidence, suggesting that the resistance change resulted from oxygen migration.
In Situ TEM Investigation of the Electrochemical Behavior in CNTs/MnO2-Based Energy Storage Devices
(2017-09-19)
Tsai, Tsung-Chun
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Huang, Guan-Min
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Huang, Chun-Wei
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Chen, Jui-Yuan
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Yang, Chih-Chieh
Transition metal oxides have attracted much interest owing to their ability to provide high power density in lithium batteries; therefore, it is important to understand the electrochemical behavior and mechanism of lithiation-delithiation processes. In this study, we successfully and directly observed the structural evolution of CNTs/MnO2 during the lithiation process using transmission electron microscopy (TEM). CNTs/MnO2 were selected due to their high surface area and capacitance effect, and the lithiation mechanism of the CNT wall expansion was systematically analyzed. Interestingly, the wall spacings of CNTs/MnO2 and CNTs were obviously expanded by 10.92% and 2.59%, respectively. The MnO2 layer caused structural defects on the CNTs surface that could allow penetration of Li+ and Mn4+ through the tube wall and hence improve the ionic transportation speed. This study provided direct evidence for understanding the role of CNTs/MnO2 in the lithiation process used in lithium ion batteries and also offers potential benefits for applications and development of supercapacitors.
In situ TEM observation of Au-Cu2O core-shell growth in liquids
(2019-06-07)
Chen, Fu-Chun
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Chen, Jui-Yuan
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Lin, Ya-Hsuan
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Kuo, Ming-Yu
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Hsu, Yung-Jung
Heterogeneous nanoparticles are widely used in catalysis, sensors and biology due to their versatile functions. Among the various heterogeneous nanoparticles, Au-Cu2O core-shell nanoparticles show high stability and short response times for use as sensors and catalysts and have thus attracted much attention. Previous studies show that the properties of Au-Cu2O are mainly related to the shape and size of the Au-Cu2O nanoparticles. However, the forming behavior of heterostructures and the mechanism have not been fully explored. In this work, liquid cell transmission electron microscopy (LCTEM) was used to investigate the formation of these interesting Au-Cu2O nanoparticles and their process of aggregation. The electron beam and dispersion of gold nanoparticles are both important parameters for the reduction reaction in in situ LCTEM. The Au-Cu2O core-shell nanoparticles can be synthesized to have two morphologies, multifaceted and cubic. The nanoparticles grew into these different morphologies due to the amount of remaining citrate ligands on the surface of the gold nanoparticles. For the multifaceted nanoparticles, the epitaxy of the two components is confirmed from high-resolution TEM images and electron diffraction patterns with an epitaxial relationship of Au (020)//Cu2O (020) and Au [101]//Cu2O [101]. The growth rate is approximately 210 nm(2) s-1. On the other hand, the cubic nanoparticles nucleate and grow independently. The growth kinetics and elemental distributions have been systematically studied. In addition, the nanoclusters would float, rotate, and finally aggregate with the surrounding clusters. This in situ experiment sheds light on the growth mechanisms of nanostructures and will improve the applicability and controllability of heterostructure synthesis.
In-situ TEM observation of Multilevel Storage Behavior in low power FeRAM device
(2017-04-01)
Chiu, Chung-Hua
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Huang, Chun-Wei
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Hsieh, Ying-Hui
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Chen, Jui-Yuan
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Chang, Chia-Fu
The quest for non-volatile memories has attracted tremendous attention, especially in mature ferroelectric random access memory (FeRAM) with properties of high read/write speed and low power consumption. Strain engineering of multiferroic BiFeO3 (BFO) has recently become the subject of broad research interest because of its intriguing properties. In this study, we demonstrate the switchable diode characteristics in highly strained BFO thin films. Using a unique in situ electrical transmission electron microscopy (TEM), we verify the correlation between ferroelectric resistive switching with multilevel states and polarization reversal. Structural investigation confirms that the phase transition from mixed phase to pure T-like phase, accompanying with the polarization reversal by external bias, is the origin of the multilevel states. The switchable diode with multilevel resistive switching can be explained in terms of the variation of the barrier height, governed by ferroelectric polarization and polarity of the external bias. This research model, i.e., engineering of the room inside, can offer an approach toward high-density memories.
Low Power Consumption Nanofilamentary ECM and VCM Cells in a Single Sidewall of High-Density VRRAM Arrays
(1970-01-01)
Wu, Min-Ci
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Ting, Yi-Hsin
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Chen, Jui-Yuan
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Wu, Wen-Wei
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交大名義發表
The technologies of 3D vertical architecture have made a major breakthrough in establishing high-density memory structures. Combined with an array structure, a 3D high-density vertical resistive random access memory (VRRAM) cross-point array is demonstrated to efficiently increase the device density. Though electrochemical migration (ECM) resistive random access (RRAM) has the advantage of low power consumption, the stability of the operating voltage requires further improvements due to filament expansions and deterioration. In this work, 3D-VRRAM arrays are designed. Two-layered RRAM cells, with one inert and one active sidewall electrode stacked at a cross-point, are constructed, where the thin film sidewall electrode in the VRRAM structure is beneficial for confining the expansions of the conducting filaments. Thus, the top cell (Pt/ZnO/Pt) and the bottom cell (Ag/ZnO/Pt) in the VRRAM structure, which are switched by different mechanisms, can be analyzed at the same time. The oxygen vacancy filaments in the Pt/ZnO/Pt cell and Ag filaments in the Ag/ZnO/Pt cell are verified. The 40 nm thickness sidewall electrode restricts the filament size to nanoscale, which demonstrates the stability of the operating voltages. Additionally, the 0.3 V operating voltage of Ag/ZnO/Pt ECM VRRAM demonstrates the potential of low power consumption of VRRAM arrays in future applications.
Mass transport phenomena in copper nanowires at high current density
(2016-04)
Huang, Yu-Ting
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Huang, Chun-Wei
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Chen, Jui-Yuan
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Ting, Yi-Hsin
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Cheng, Shao-Liang
Electromigration in Cu has been extensively investigated as the root cause of typical breakdown failure in Cu interconnects. In this study, Cu nanowires connected to Au electrodes are fabricated and observed using in situ transmission electron microscopy to investigate the electro- and thermo-migration processes that are induced by direct current sweeps. We observe the dynamic evolution of different mass transport mechanisms. A current density on the order of 10(6) A/cm(2) and a temperature of approximately 400 A degrees C are sufficient to induce electro- and thermo-migration, respectively. Observations of the migration processes activated by increasing temperatures indicate that the migration direction of Cu atoms is dependent on the net force from the electric field and electron wind. This work is expected to support future design efforts to improve the robustness of Cu interconnects.
Ni/NiO/HfO2 Core/Multishell Nanowire ReRAM Devices with Excellent Resistive Switching Properties
(2018-11-01)
Huang, Ting-Kai
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Chen, Jui-Yuan
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Ting, Yi-Hsin
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Wu, Wen-Wei
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交大名義發表
Resistive random-access memory (ReRAM) is one of the most promising types of nonvolatile memory because it has several important advantages, for example, a simple metal-insulator-metal structure, fast operating speed, high endurance, high retention, and low energy consumption. However, the reliability of ReRAM nanodevices is not persistent, and the complete switching mechanism is not fully understood. In this study, a unique 1D Ni/NiO/HfO2 core/multishell ReRAM nanodevice is designed and fabricated. The different properties, including the electrical characteristics, surface morphology, and elemental distribution, are systematically investigated. The Ni/NiO/HfO2 heterostructure nanowire ReRAM device exhibits excellent electrical characteristics and resistive switching properties. It is remarkable that the endurance could be maintained up to 200 cycles, which is extremely good for a 1D ReRAM device. Additionally, a focused-ion beam technique is used to prepare samples for subsequent transmission electron microscopic (TEM) observation. From the TEM analysis, the position of the conducting filaments is verified and the elemental composition of the conducting filaments is confirmed. The migration of hafnium ions forms the conducting filaments between the HfO2 layer and Ni core, resulting in the switching characteristic. The study enriches the understanding of the mechanism and provides a design to enhance the resistive switching properties of ReRAM nanodevices.