Browsing by Issue Date, starting with "2011-01-31"

Now showing 1 - 20 of 42311

Compact microdisk cavity laser with type-II GaSb/GaAs quantum dots
(2011-01-31)
Hsu, K. S.
;
Chiu, T. T.
;
Lin, Wei-Hsun
;
Chen, K. L.
;
Shih, M. H.
Microdisk lasers with active region made of type-II GaSb/GaAs quantum dots on the GaAs substrate have been demonstrated. A microdisk cavity with diameter of 3.9 mu m was fabricated from a 225-nm-thick GaAs layer filled with GaSb quantum dots. Lasing at wavelengths near 1000 nm at 150 K was achieved for this microdisk. A high threshold characteristic temperature of 77 K was also observed. It is found that the lasing wavelength matches closely with the first-order whispering-gallery mode of the cavity as obtained from the finite-element method simulation. (c) 2011 American Institute of Physics. [doi: 10.1063/1.3543839]
A reflective polarizer-free electro-optical switch using dye-doped polymer-stabilized blue phase liquid crystals
(2011-01-31)
Lin, Yi-Hsin
;
Chen, Hung-Shan
;
Chiang, Tsung-Han
;
Wu, Chun-Hung
;
Hsu, Hsu-Kuan
We demonstrate a reflective polarizer-free electro-optical switch using dye-doped polymer-stabilized blue phase liquid crystals (DDPSBP-LC). At the voltage-off state, the dye molecules and liquid crystals form the structure of the double twist cylinders. As a result, the DDPSBP-LC is in dark state due to the combination of Bragg reflection and light absorption. At the voltage-on state, the blue phase structure is unwound locally. The DDPSBP-LC is then in bright state because of the small light absorption only. The applications of such a switch are shutter glass of 3D displays, and electronic papers. (C) 2011 Optical Society of America
Stacked GeO/SrTiO(x) Resistive Memory with Ultralow Resistance Currents
(2011-01-31)
Cheng, C. H.
;
Chin, Albert
;
Yeh, F. S.
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
We report a high performance and low-power operated resistive memory. Using stacked covalent-bond-dielectric GeO(x) on metal-oxide SrTiO(x) to form the cost-effective Ni/GeO(x)/SrTiO(x)/TaN resistive random access memory, ultralow set power of small 1 mu W (0.9 mu A at 1.2 V), reset power of 13 pW (0.13 nA at 0.1 V), fast 50 ns switching time and good 10(6) cycling endurance are realized. (C) 2011 American Institute of Physics. [doi:10.1063/1.3549689]
Implementation issues of the nearfield equivalent source imaging microphone array
(2011-01-31)
Bai, Mingsian R.
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Lin, Jia-Hong
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Tseng, Chih-Wen
;
機械工程學系
;
Department of Mechanical Engineering
This paper revisits a nearfield microphone array technique termed nearfield equivalent source imaging (NESI) proposed previously. In particular, various issues concerning the implementation of the NESI algorithm are examined. The NESI can be implemented in both the time domain and the frequency domain. Acoustical variables including sound pressure, particle velocity, active intensity and sound power are calculated by using multichannel inverse filters. Issues concerning sensor deployment are also investigated for the nearfield array. The uniform array outperformed a random array previously optimized for far-field imaging, which contradicts the conventional wisdom in far-field arrays. For applications in which only a patch array with scarce sensors is available, a virtual microphone approach is employed to ameliorate edge effects using extrapolation and to improve imaging resolution using interpolation. To enhance the processing efficiency of the time-domain NESI, an eigensystem realization algorithm (ERA) is developed. Several filtering methods are compared in terms of computational complexity. Significant saving on computations can be achieved using ERA and the frequency-domain NESI, as compared to the traditional method. The NESI technique was also experimentally validated using practical sources including a 125 cc scooter and a wooden box model with a loudspeaker fitted inside. The NESI technique proved effective in identifying broadband and non-stationary sources produced by the sources. (C) 2010 Elsevier Ltd. All rights reserved.
Nitrogenated amorphous InGaZnO thin film transistor
(2011-01-31)
Liu, Po-Tsun
;
Chou, Yi-Teh
;
Teng, Li-Feng
;
Li, Fu-Hai
;
Shieh, Han-Ping
This work presents the electrical characteristics of the nitrogenated amorphous InGaZnO thin film transistor (a-IGZO:N TFT). The a-IGZO: N film acting as a channel layer of a thin film transistor (TFT) device was prepared by dc reactive sputter with a nitrogen and argon gas mixture at room temperature. Experimental results show that the in situ nitrogen incorporation to IGZO film can properly adjust the threshold voltage and enhance the ambient stability of a TFT device. Furthermore, the a-IGZO: N TFT has a 44% increase in the carrier mobility and electrical reliability and uniformity also progress obviously while comparing with those not implementing a nitrogen doping process. (C) 2011 American Institute of Physics. [doi:10.1063/1.3551537]
A facile route to prepare PdPt alloys for ethanol electro-oxidation in alkaline electrolyte
(2011-01-31)
Lin, Sheng-Chieh
;
Chen, Jing-Yu
;
Hsieh, Yi-Fan
;
Wu, Pu-Wei
;
材料科學與工程學系
We adopted a displacement reaction in acidic solution that enabled the spontaneous reduction of Pd and Pt cations in conjunction with corrosive dissolution of Ni. The composition for the PdPt was adjusted by varying the concentration of Pd and Pt cations. From SEM images and XRD patterns, the PdPt formed an fcc alloy uniformly deposited on the Ni substrate. Electro-oxidation of ethanol was conducted in alkaline electrolyte for samples of Pd, Pt, and PdPt alloys. In cyclic voltammetric profiles, the Pd(77)Pt(23) revealed the highest electrocatalytic ability in both apparent current and mass activity, followed by Pd(87)Pt(13), Pd, and Pt. Similar behaviors were observed in life time measurements in which stable performances for ethanol electro-oxidation were obtained. (C) 2010 Elsevier B.V. All rights reserved.
Vertical polymer phototransistor featuring photomultiplication due to base-field shielding
(2011-01-31)
Zan, Hsiao-Wen
;
Tsai, Wu-Wei
;
Meng, Hsin-Fei
;
物理研究所
;
光電工程學系
We introduce a vertical polymer phototransistor with low operational voltage (-1.5 V). A blended polymer layer with both acceptor and donor materials was used as a channel material in the vertical space-charge-limited transistor. Under illumination, we obtained external quantum efficiency (EQE) as high as 360% at 620 nm. We propose the effects of base-field shielding as a means to explain high EQE. This proposition has been supported by two-dimensional simulation of the device. (C) 2011 American Institute of Physics. [doi:10.1063/1.3552714]
Stacked GeO/SrTiOx Resistive Memory with Ultralow Resistance Currents
(2011-01-31)
Cheng, C. H.
;
Chin, Albert
;
Yeh, F. S.
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
We report a high performance and low-power operated resistive memory. Using stacked covalent-bond-dielectric GeOx on metal-oxide SrTiOx to form the cost-effective Ni/GeOx/SrTiOx/TaN resistive random access memory, ultralow set power of small 1 mu W (0.9 mu A at 1.2 V), reset power of 13 pW (0.13 nA at 0.1 V), fast 50 ns switching time and good 10(6) cycling endurance are realized. (C) 2011 American Institute of Physics. [doi:10.1063/1.3549689]
2-Step self-assembly method to fabricate broadband omnidirectional antireflection coating in large scale
(2011-02-01)
Yeung, K. M.
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Luk, W. C.
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Tam, K. C.
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Kwong, C. Y.
;
Tsai, M. A.
We have developed a simple and reproducible 2-step self-assembly method for the fabrication of broadband, omnidirectional antireflection coating on glass substrate with 4 in. size. The glass surface has been modified to be positively charged, then the negatively charged nano silica is self-assembled to the glass substrate by electrostatic attraction. The nanostructure on the glass substrate reduces the reflection significantly, which results in enhanced transmittance. Transmittance as high as 97.7% at 499 nm has been obtained for a double-side coated glass substrate. Obvious reduction in weighted reflectance is still observed up to 60 degrees incident angle. (C) 2010 Elsevier B.V. All rights reserved.
Investigation of the Atmospheric Helium Dielectric Barrier Discharge Driven by a Realistic Distorted-Sinusoidal Voltage Power Source
(2011-02-01)
Hung, C. -T.
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Chiu, Y. -M.
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Hwang, F. -N.
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Chiang, M. -H.
;
Wu, J. -S.
The non-equilibrium atmospheric-pressure parallel-plate helium dielectric barrier discharge (DBD) driven by a realistic 20 kHz distorted-sinusoidal voltage waveform has been investigated by means of simulations and experiments. A self-consistent one-dimensional fluid modeling code considering the non-local electron energy balance was applied to simulate the helium DBD. The effect of selecting plasma chemistry was investigated by comparing simulations with experiments. The results show that the simulations, which include more excited helium, metastable helium and electron-ion-related reaction channels, can faithfully reproduce the measured discharged temporal current quantitatively. Based on the simulated discharge properties, we have found that there is complicated mode transition of discharges from the long Townsend-like to the "dark current"-like, then to the short primary Townsend-like and the short secondary Townsend-like for the helium DBD that is driven by a realistic distorted-sinusoidal voltage power source. Discharge properties in different periods of discharge are discussed in detail in the paper.
All-optical controllable trapping and transport of subwavelength particles on a tapered photonic crystal waveguide
(2011-02-01)
Lin, Pin-Tso
;
Lee, Po-Tsung
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光電工程學系
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Department of Photonics
We propose that a tapered photonic crystal waveguide design can unify optical trapping and transport functionalities to advance the controllability of optical manipulation. Subwavelength particles can be trapped by a resonance-enhanced field and transported to a specified position along the waveguide on demand by varying the input wavelength. A simulated transport ability as high as 148 (transport distance/wavelength variation) is obtained by the waveguide with 0.1 degrees tilted angle. Stable trapping of a 50 nm polystyrene particle can be achieved with input power of 7 mW. We anticipate that this design would be beneficial for future life science research and optomechanical applications. (C) 2011 Optical Society of America
Hybrid-Patent Classification Based on Patent-Network Analysis
(2011-02-01)
Liu, Duen-Ren
;
Shih, Meng-Jung
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資訊管理與財務金融系註：原資管所+財金所
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Department of Information Management and Finance
Effective patent management is essential for organizations to maintain their competitive advantage. The classification of patents is a critical part of patent management and industrial analysis. This study proposes a hybrid-patent-classification approach that combines a novel patent-network-based classification method with three conventional classification methods to analyze query patents and predict their classes. The novel patent network contains various types of nodes that represent different features extracted from patent documents. The nodes are connected based on the relationship metrics derived from the patent metadata. The proposed classification method predicts a query patent's class by analyzing all reachable nodes in the patent network and calculating their relevance to the query patent. It then classifies the query patent with a modified k-nearest neighbor classifier. To further improve the approach, we combine it with content-based, citation-based, and metadata-based classification methods to develop a hybrid- classification approach. We evaluate the performance of the hybrid approach on a test dataset of patent documents obtained from the U.S. Patent and Trademark Office, and compare its performance with that of the three conventional methods. The results demonstrate that the proposed patent-network-based approach yields more accurate class predictions than the patent network-based approach.
Development of an improved spatial reconstruction technique for the HLL method and its applications
(2011-02-01)
Smith, Matthew R.
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Lin, K. -M.
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Hung, C. -T.
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Chen, Y. -S.
;
Wu, J. -S.
The integral form of the conventional HLL fluxes are presented by taking integrals around the control volume centred on each cell interface. These integrals are demonstrated to reduce to the conventional HLL flux through simplification by assuming spatially constant conserved properties. The integral flux expressions are then modified by permitting the analytical inclusion of spatially linearly varying conserved quantities. The newly obtained fluxes (which are named HLLG fluxes for clarification, where G stands for gradient inclusion) demonstrate that conventional reconstructions at cell interfaces are invalid and can produce unstable results when applied to conventional HLL schemes. The HLLG method is then applied to the solution of the Euler Equations and Shallow Water Equations for various common benchmark problems and finally applied to a 1D fluid modeling for an argon RF discharge at low pressure. Results show that the correct inclusion of flow gradients is shown to demonstrate superior transient behavior when compared to the existing HLL solver and conventional spatial reconstruction without significantly increasing computational expense. (C) 2010 Elsevier Inc. All rights reserved.
靜態隨機存取記憶體裝置
(2011-02-01)
楊仕琪
;
楊皓義
;
莊景德
;
黃威
本發明係揭露一種靜態隨機存取記憶體裝置，包含複數個記憶體組、複數個寫入控制電路、複數個電源開關組及一位址解碼器，每一寫入控制電路對應連接於每一記憶體組，當位址解碼器接收一寫入資料而產生一控制訊號，並據此開啟其中一電源開關組，使對應之寫入控制電路將一寫入位元資料寫入於對應之記憶體組內，寫入完成後隨之關閉，以減少靜態隨機存取記憶體裝置中的電晶體開啟時間，讓電晶體可進入回復的狀態，因此，可有效減緩晶片（IC）中的靜態隨機存取記憶體受正/負溫度偏壓不穩定性的影響，進而提高存取速度、穩定度及降低功率消耗等優點。
奈米級之藥物傳送裝置、製備方法及用途
(2011-02-01)
陳三元
;
胡尚秀
;
劉典謨
;
郭冠廷
在此揭示活體內監控及釋放藥物的奈米裝置與方法。所揭示的奈米裝置特徵在於具有一裝載有藥物的奈米球，可透過磁性刺激而將其中的藥物釋出。也可將此奈米裝置當作一種顯影劑，於活體內造影並監控所釋出藥物或是單獨注入活體標的位置處之藥物的濃度與分佈情形。
Enhanced Stimulated Emission from Optically Pumped Gallium Nitride Nanopillars
(2011-02-01)
Lo, Ming-Hua
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Cheng, Yuh-Jen
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Kuo, Hao-Chung
;
Wang, Shing-Chung
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光電工程學系
We report the observation of an enhanced stimulated emission from optically pumped GaN nanopillars. The nanopillars were fabricated from an epitaxial wafer by patterned etching followed by crystalline regrowth. When the sample was optically excited, a strong stimulated emission peak emerged from a broad spontaneous emission background. The emission was attributed to electron-hole plasma gain at high carrier density. The emission slope efficiency was greatly enhanced by 20 times compared with a GaN substrate under the same pumping configuration. We remark that the enhancement is due to better gain and photon interaction from the multiple scattering of photons among nanopillars. (C) 2011 The Japan Society of Applied Physics
IMS EMERGENCY SERVICES: A PRELIMINARY STUDY
(2011-02-01)
Lin, Yi-Bing
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Tsai, Meng-Hsun
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Tu, Yuan-Kuang
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資訊學院
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College of Computer Science
Emergency call and walkie-talkie are two services utilized in emergency situations. During Typhoon Morakot in 2009, we experienced the deficiency of emergency call service that cannot continuously track callers in real time and walkie-talkie communications where a speaker may not be granted the permission to talk. These issues can be resolved by the emergency call and push-to-talk over cellular services in IP Multimedia Subsystem. This article conducts a preliminary study on how these two services can be effectively exercised in IMS.
SU-8 serial MEMS switch for flexible RF applications
(2011-02-01)
Chao, Tzu-Yuan
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Hsu, M. C.
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Lin, C-D
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Cheng, Y. T.
;
電子工程學系及電子研究所
This paper presents a novel SU-8 micromachining process for MEMS series switch fabrication. The switch is designed with a clamped-clamped SU-8 (5 mu m)/Cu (2 mu m)/SU-8 (3 mu m) beam structure driven by electrostatic force, which is fabricated on a silicon substrate with a resistivity of similar to 5 Omega cm. Experimental results show that the switch can exhibit better than -4.48 dB insertion loss and -28.2 dB isolation up to 12 GHz. Such a large insertion loss is mainly caused by substrate loss which can be further reduced down to -0.75 dB as long as the substrate resistivity is increased up to 100 Omega cm.
Nano Approach Investigation of the Conduction Mechanism in Polyaniline Nanofibers
(2011-02-01)
Lin, Yen-Fu
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Chen, Chien-Hsiang
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Xie, Wen-Jia
;
Yang, Sheng-Hsiung
;
Hsu, Chain-Shu
A nanotechnological approach is applied to measurements of the electric field dependence of resistance under a high electric field while in low voltage. With this technique, the conduction mechanism on a mesoscopic scale is explored in a single, nonagglomerated nanofiber. Polyaniline nanofibers are prepared by vigorous mixing of aniline and oxidation agent ammonium persulfate in acid solution. They exhibit a uniform nanoscale morphology rather than agglomeration as that produced via conventional chemical oxidation. The as-synthesized polyaniline nanofibers are doped (dedoped) with a HCl acid (NH(3) base), and their temperature behaviors of resistances follow an exponential function with an exponent of T(-1/2). To measure the conduction mechanism in a single nanofiber, the dieiectrophoresis technique is implemented to position nanofibers on top of two electrodes with a nanogap of 100-600 nm, patterned by electron-beam lithography. After the devices are irradiated by electron beam to reduce contact resistances, their temperature behaviors and electric field dependences are unveiled. The experimental results agree well with the theoretical model of charging energy limited tunneling. Other theoretical models such as Efros-Shklovskii and Mott's one-dimensional hopping conduction are excluded after comparisons and arguments. Through fitting, the size of the conductive grain, separation distance between two grains, and charging energy per grain in a single polyaniline nanofiber are estimated to be about 4.9 nm, 2.8 nm, and 78 meV, respectively. The nanotechnological approach, where the nanogap and the dielectrophoresis technique are used for single nanofiber device fabrication, Is applied for determination of mesoscopic charge transport in a polyaniline conducting polymer.
Large field-induced strains in a lead-free piezoelectric material
(2011-02-01)
Zhang, J. X.
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Xiang, B.
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He, Q.
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Seidel, J.
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Zeches, R. J.
Piezoelectric materials exhibit a mechanical response to electrical inputs, as well as an electrical response to mechanical inputs, which makes them useful in sensors and actuators(1). Lead-based piezoelectrics demonstrate a large mechanical response, but they also pose a health risk(2). The ferroelectric BiFeO(3) is an attractive alternative because it is lead-free, and because strain can stabilize BiFeO(3) phases with a structure that resembles a morphotropic phase boundary(3). Here we report a reversible electric-field-induced strain of over 5% in BiFeO(3) films, together with a characterization of the origins of this effect. In situ transmission electron microscopy coupled with nanoscale electrical and mechanical probing shows that large strains result from moving the boundaries between tetragonal- and rhombohedral-like phases, which changes the phase stability of the mixture. These results demonstrate the potential of BiFeO(3) as a substitute for lead-based materials in future piezoelectric applications.