Browsing by Author "Chang, Wen-Yuan"

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Compact and Dual-Band Arbitrary Power-Split Quadrature Coupler Using the Composite Right/Left-Handed Transmission Lines
(2014)
Chi, Pei-Ling
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Chang, Wen-Yuan
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資訊工程學系
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電機學院
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Department of Computer Science
In this paper, a dual-band quadrature coupler is proposed for arbitrary power divisions using the composite right/left-handed (CRLH) transmission lines. The presented prototype is based on two identical CRLH transmission lines of 50 ohm and a pair of lumped-element parallel tanks loaded to the CRLH host lines. The power division ratio at either frequency is determined by the electrical length of the 50-Omega CRLH lines, which facilitates coupler realization of arbitrary power split, even for a large division ratio. By applying the CRLH lines, the dual operating frequencies as well as the corresponding power split ratios can be arbitrarily designed, which on the contrary is infeasible by microstrip lines. Two coupler prototypes were developed for power division ratios of 10/10 dB and 10/6 dB at 0.9/1.8 GHz. In particular, the first fabricated coupler occupies only 18% footprint of the 0.9-GHz microstrip branch-line coupler. Experimental results are in good agreement with simulation data.
Improved Performance of ZnO-Based Resistive Memory by Internal Diffusion of Ag Atoms
(2012-08-01)
Peng, Chung-Nan
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Wang, Chun-Wen
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Huang, Jian-Shiou
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Chang, Wen-Yuan
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Wu, Wen-Wei
An Ag/ZnO/Pt memory device, which has much better resistive switching behaviour than Pt/ZnO/Pt device was demonstrated. The detailed resistive mechanisms for the Pt/ZnO/Pt and the Ag/ZnO/Pt systems are proposed and investigated. Microstructures are observed by transmission electron microscope (TEM), indicating that the formation of conducting path for both systems is different. For the Pt/ZnO/Pt device, the conductive filament path is constructed by the oxygen vacancies from top to bottom electrodes under a larger enough bias at a forming process. For the Ag/ZnO/Pt device, the filament path was grown by oxygen vacancies combined with an internal diffusion of Ag atoms under a large bias and can provide the lowest energy barrier for electrons transported between two electrodes during set and reset processes, which reduces formation of other conducting paths after each switching. Accordingly, the stable switching performance of the Ag/ZnO/Pt device can be achieved over 100 cycles even the thickness of ZnO film <25 nm.
Resistive switching of Au/ZnO/Au resistive memory: an in situ observation of conductive bridge formation
(2012-10-08)
Peng, Chung-Nan
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Wang, Chun-Wen
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Chan, Tsung-Cheng
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Chang, Wen-Yuan
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Wang, Yi-Chung
A special chip for direct and real-time observation of resistive changes, including set and reset processes based on Au/ZnO/Au system inside a transmission electron microscope (TEM), was designed. A clear conducting bridge associated with the migration of Au nanoparticles (NPs) inside a defective ZnO film from anode to cathode could be clearly observed by taking a series of TEM images, enabling a dynamic observation of switching behaviors. A discontinuous region (broken region) nearby the cathode after reset process was observed, which limits the flow of current, thus a high resistance state, while it will be reconnected to switch the device from high to low resistance states through the migration of Au NPs after set process. Interestingly, the formed morphology of the conducting bridge, which is different from the typical formation of a conducting bridge, was observed. The difference can be attributed to the different diffusivities of cations transported inside the dielectric layer, thereby significantly influencing the morphology of the conducting path. The current TEM technique is quite unique and informative, which can be used to elucidate the dynamic processes in other devices in the future.