Browsing by Author "Wu, Chia-Wei"

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Electron Emission Properties of Nitrogen-Induced Localized Defects in InAsN/GaAs Quantum Dots
(2011-11-01)
Yang, Cheng-Hong
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Hsieh, Meng-Chien
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Wu, Chia-Wei
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Chang, Yen-Ting
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Wu, Yue-Han
The electron-emission properties of nitrogen-induced (N-induced) localized defects in InAsN/GaAs quantum dots (QDs) are investigated in detail by capacitance-voltage (C-V) profiling and bias-dependent deep-level transient spectroscopy (DLTS). The incorporation of nitrogen (N) into InAs QDs is shown to produce localized defects near QDs and threading-dislocation-related defects in the top GaAs layer. The threading dislocation is associated with an electron-emission energy of approximately 0.648 eV and emission from the sample surface toward the QDs. The electron-emission energy from the QDs associated with the localized defects increases from 0.19 to 0.36 eV, indicating that both types of defect near QDs have low electron emission energies. Therefore, the change in emission energy is attributable to the defects across the QD interface where a band offset exists. The C-V profile at 300 K shows extended carrier depletion near the QDs. As ac frequency increases, an electron-emission peak emerges at the QDs; this peak is followed by another prominent peak, suggesting that the localized defect that is responsible for this latter peak has an energy below the QD electron ground state. On the basis of a C-V profile simulation, this defect is located at the QD at the observed emission energy below the GaAs conduction band, 360 meV. A comparison with InAsN QD and strain relaxation InAs QD samples reveals that the localized defect arises from a nitrogen alloy fluctuation in the QD. The energy location of this defect reveals a possibility that incorporated N is associated with a particular mode. (C) 2011 The Japan Society of Applied Physics
OneM2M-based IoT Protocol Integration
(2017-01-01)
Wu, Chia-Wei
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Lin, Fuchun Joseph
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Wang, Chia-Hong
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Chang, Norman
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資訊工程學系
In order to enable the development of smart services, many IoT platforms were proposed to securely and reliably connect IoT devices to the Internet and to each other. Examples are IoTivity from Open Connectivity Foundation (OCF), AllJoyn from AllSeen Alliance, Weave from Google and HomeKit from Apple. However, such fragmentation of IoT platforms has made the development of IoT applications very difficult as it requires each IoT device and application support many protocols in order to connect to an available platform. To resolve this problem, we propose to use oneM2M International standards as the middleware for IoT protocols integration. The oneM2M technical specifications have defined how oneM2M can be used to interwork with IoTivity and AllJoyn based on Interworking Proxy Application Entity (IPE). In this paper, we propose how to design and implement such an IPE based on the oneM2M specifications for bridging oneM2M and IoTivity/AllJoyn. In particular, we address the mappings of device management functions among these platforms where standard specifications are still lacking. Via actual implementation, we evaluate two interworking designs for device management in order to identify the best one for protocol integration.
Planar Diplexer Design Using Hairpin Resonators Loaded with External Capacitors for Improvement of Isolation and Stopband Rejection Levels
(2019-01-01)
Tsao, Yi-Fan
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Huang, Ting-Jui
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Hsu, Heng-Tung
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Wu, Chia-Wei
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交大名義發表
We have successfully demonstrated the design and implementation of a planar diplexer operating at 900MHz and 1800MHz intended for cellular system applications. Using hairpin resonators loaded with external capacitors, we managed to obtain 40% size reduction compared to the ones without external loading with substantial improvement in the band-to-band isolation.
Tunable nitrogen-doped graphene sheets produced with in situ electrochemical cathodic plasma at room temperature for lithium-ion batteries
(2019-06-01)
Yen, Po-Jen
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Ilango, P. Robert
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Chiang, Ya-Chi
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Wu, Chia-Wei
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Hsu, Yung-Chi
This paper describes a facile and tunable method, performed at room temperature and amenable to mass-production, for the preparation of nitrogen-doped graphene sheets using in situ electrochemical cathodic plasma exfoliation of a graphite/melamine composite. The plasma generated at the submerged surface of the graphite/melamine composite electrode not only exfoliated the graphite granules into graphene sheets but also induced the doping of nitrogen atoms. The sizes and morphologies of the graphene sheets, comprising four to five layers of graphene, were confirmed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Tuning the concentration of melamine in the graphite/melamine composites led to different levels of nitrogen-doping in the graphene sheets; the stability of the nitrogen-doped graphene sheets was investigated in various harsh environments. Furthermore, the use of the 4.63 at% nitrogen-doped graphene sheets as anode materials resulted in lithium-ion batteries displaying excellent performance, with a capacity of 488 mA h g(-1) at 100 mA g(-1) after 100 cycles that was better than that of the device incorporating pristine graphene sheets (344 mA h g(-1) at 100 mA g(-1) after 100 cycles). This method is a new and tunable approach for producing massive amounts of nitrogen-doped graphene sheets from graphite powder at room temperature. (C) 2019 Elsevier Ltd. All rights reserved.
Using Different Ions to Tune Graphene Stack Structures from Sheet- to Onion-Like During Plasma Exfoliation, with Supercapacitor Applications
(2019-04-23)
Yen, Po-Jen
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Sahoo, Sumanta Kumar
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Chiang, Ya-Chi
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Huang, Shih-Yu
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Wu, Chia-Wei
In this article, we report a facile and simple approach for tuning graphene nanosheet structures (GNS) with different ions in the electrolytes through cathodic plasma exfoliation process in electrochemical reactions. We obtained sheet- and onion-like GNS when aqueous electrolyte NaOH and H2SO4, respectively, were present during plasma exfoliation in the electrochemical reactions, as evidenced from scanning electron microscopy and transmission electron microscopy images. Moreover, the onion-like GNS exhibited a specific surface area of 464m(2) g(-1) and a supercapacitive performance of 67.1F g(-1), measured at a scan rate of 5mV s(-1) in 1M NaCl; these values were much higher than those (72m(2) g(-1) and 21.6F g(-1), respectively) of the sheet-like GNS. This new approach for efficiently generating tunable stacked graphene structures with different ions, in the cathodic plasma exfoliation process, has promising potentials for use in energy storage devices.