Browsing by Issue Date, starting with "2013-07-08"

Now showing 1 - 20 of 31185

Abnormal sub-threshold swing degradation under dynamic hot carrier stress in HfO2/TiN n-channel metal-oxide-semiconductor field-effect-transistors
(2013-07-08)
Tsai, Jyun-Yu
;
Chang, Ting-Chang
;
Lo, Wen-Hung
;
Chen, Ching-En
;
Ho, Szu-Han
This work finds abnormal sub-threshold swing (S.S.) degradation under dynamic hot carrier stress (HCS) in n-channel metal-oxide-semiconductor field-effect-transistors with high-k gate dielectric. Results indicate that there is no change in S.S. after dynamic HCS due to band-to-band hot hole injection at the drain side which acts to diminish the stress field. Moreover, the impaired stress field causes the interface states to mainly distribute in shallow states. This results in ON state current and transconductance decreases, whereas S.S. degradation is insignificant after dynamic HCS. The proposed model is confirmed by one-side charge pumping measurement and gate-to-drain capacitance at varying frequencies. (C) 2013 AIP Publishing LLC.
Unraveling the origins of electromechanical response in mixed-phase bismuth ferrite
(2013-07-08)
Vasudevan, R. K.
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Okatan, M. B.
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Liu, Y. Y.
;
Jesse, S.
;
Yang, J. -C.
The origin of giant electromechanical response in a mixed-phase rhombohedral-tetragonal BiFeO3 thin film is probed using subcoercive scanning probe microscopy based multiple-harmonic measurements. Significant contributions to the strain arise from a second-order harmonic response localized at the phase boundaries. Strain and dissipation data, backed by thermodynamic calculations, suggest that the source of the enhanced electromechanical response is the motion of phase boundaries. These findings elucidate the key role of labile phase boundaries, both natural and artificial, in achieving thin films with giant electromechanical properties.
Adiabatically driven Brownian pumps
(2013-07-08)
Rozenbaum, Viktor M.
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Makhnovskii, Yurii A.
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Shapochkina, Irina V.
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Sheu, Sheh-Yi
;
Yang, Dah-Yen
We investigate a Brownian pump which, being powered by a flashing ratchet mechanism, produces net particle transport through a membrane. The extension of the Parrondo's approach developed for reversible Brownian motors [Parrondo, Phys. Rev. E 57, 7297 (1998)] to adiabatically driven pumps is given. We demonstrate that the pumping mechanism becomes especially efficient when the time variation of the potential occurs adiabatically fast or adiabatically slow, in perfect analogy with adiabatically driven Brownian motors which exhibit high efficiency [Rozenbaum et al., Phys. Rev. E 85, 041116 (2012)]. At the same time, the efficiency of the pumping mechanism is shown to be less than that of Brownian motors due to fluctuations of the number of particles in the membrane.
Self-assembly of hierarchical MoSx/CNT nanocomposites (2 < x < 3): towards high performance anode materials for lithium ion batteries
(2013-07-09)
Shi, Yumeng
;
Wang, Ye
;
Wong, Jen It
;
Tan, Alex Yuan Sheng
;
Hsu, Chang-Lung
Two dimension (2D) layered molybdenum disulfide (MoS2) has emerged as a promising candidate for the anode material in lithium ion batteries (LIBs). Herein, 2D MoSx (2 <= x <= 3) nanosheet-coated 1D multiwall carbon nanotubes (MWNTs) nanocomposites with hierarchical architecture were synthesized via a high-throughput solvent thermal method under low temperature at 2006 degrees C. The unique hierarchical nanostructures with MWNTs backbone and nanosheets of MoSx have significantly promoted the electrode performance in LIBs. Every single MoSx nanosheet interconnect to MWNTs centers with maximized exposed electrochemical active sites, which significantly enhance ion diffusion efficiency and accommodate volume expansion during the electrochemical reaction. A remarkably high specific capacity (i.e., >1000 mAh/g) was achieved at the current density of 50 mA g(-1), which is much higher than theoretical numbers for either MWNTs or MoS2 along (similar to 372 and similar to 670 mAh/g, respectively). We anticipate 2D nanosheets/1D MWNTs nanocomposites will be promising materials in new generation practical LIBs.
Flexible micro-system and fabrication method thereof
(2013-07-09)
Chao Tzu-Yuan
;
Liang Chia-Wei
;
Cheng Yu-Ting
A fabrication method for integrating chip(s) onto a flexible substrate in forming a flexible micro-system. The method includes a low-temperature flip-chip and a wafer-level fabrication process. Using the low-temperature flip-chip technique, the chip is bonded metallically onto the flexible substrate. To separate the flexible substrate from the substrate, etching is used to remove the sacrificial layer underneath the flexible substrate. The instant disclosure applies standardized micro-fabrication process for integrating chip(s) onto the flexible substrate. Without using special materials or fabrication procedures, the instant disclosure offers a cost-effective fabrication method for flexible micro-systems.
Wetted wall venturi scrubber with a 2-stage venturi throat
(2013-07-09)
Tsai Chuen-Jinn
A venturi scrubber which avoids clogging in the throat by dust particles is developed. The scrubber includes a venturi tube, two scrubbing fluid conduits and a storage tank. The venturi tube has a converging section, a diverging section and a throat section which is connected between the converging section and the diverging section. The scrubbing fluid conduit has a top end connected with the bottom end of the converging section of the venturi tube, and a bottom end extending into the storage tank. Thereby, scrubbing fluid can be guided directly into the storage tank without passing through the throat section. As a result, the clogging of dust particles on the converging section of the venturi throat can be minimized and the abnormal increase in the pressure drop of the air flow through the throat can also be avoided.
Self-assembly of hierarchical MoSx/CNT nanocomposites (2<x<3): towards high performance anode materials for lithium ion batteries
(2013-07-09)
Shi, Yumeng
;
Wang, Ye
;
Wong, Jen It
;
Tan, Alex Yuan Sheng
;
Hsu, Chang-Lung
Two dimension (2D) layered molybdenum disulfide (MoS2) has emerged as a promising candidate for the anode material in lithium ion batteries (LIBs). Herein, 2D MoSx (2 <= x <= 3) nanosheet-coated 1D multiwall carbon nanotubes (MWNTs) nanocomposites with hierarchical architecture were synthesized via a high-throughput solvent thermal method under low temperature at 2006 degrees C. The unique hierarchical nanostructures with MWNTs backbone and nanosheets of MoSx have significantly promoted the electrode performance in LIBs. Every single MoSx nanosheet interconnect to MWNTs centers with maximized exposed electrochemical active sites, which significantly enhance ion diffusion efficiency and accommodate volume expansion during the electrochemical reaction. A remarkably high specific capacity (i.e., >1000 mAh/g) was achieved at the current density of 50 mA g(-1), which is much higher than theoretical numbers for either MWNTs or MoS2 along (similar to 372 and similar to 670 mAh/g, respectively). We anticipate 2D nanosheets/1D MWNTs nanocomposites will be promising materials in new generation practical LIBs.
Method for face recognition and synthesis
(2013-07-09)
Lee Ping-Han
;
Hung Yi-Ping
A method of recognizing an object in an image is provided, the method comprises the following steps. The image having the object is provided, and principal traits of the object are encoded in order to generate a first trait code. The first trait code is compared with data stored in a database so as to obtain a plurality of differences. A minimum of the plurality of differences is found. This method can be applied to synthesize human faces.
Sensing element integrating silicon nanowire gated-diodes, manufacturing method and detecting system thereof
(2013-07-09)
Sheu Jeng-Tzong
;
Chen Chen-Chia
The invention disclosed a sensing element integrating silicon nanowire gated-diodes with microfluidic channel, a manufacturing method and a detecting system thereof. The sensing element integrating silicon nanowire gated-diodes with a microfluidic channel includes a silicon nanowire gated-diode, a plurality of reference electrodes, a passivation layer and a microfluidic channel. The reference electrodes are formed on the silicon nanowire gated-diodes, and the passivation layer having a surface decorated with chemical materials is used for covering the silicon nanowire gated-diodes, and the microfluidic channel is connected with the passivation layer. When a detecting sample is connected or absorbed on the surface of the passivation layer, the sensing element integrating silicon nanowire gated-diodes with the microfluidic channel can detect an electrical signal change.
靴帶式驅動電路
(2013-07-11)
何盈杰
;
張家齊
;
蘇朝琴
本發明係關於一種能利用其所具有之回授機制來抑制反轉電流以提升其資料傳輸速率，並降低其所消耗之功率的靴帶式驅動電路。其包括：一包含一前端輸入端、一第一反相器、一第二反相器、一第一PMOS電晶體、一第一NMOS電晶體、一第二PMOS電晶體、一第二NMOS電晶體、一第一電容、一第二電容及一前端輸出端的第一級升降壓電路；以及一包含一後端輸入端及一後端輸出端的後端CMOS反相器驅動電路。其中，前端輸出端除了連接至第二PMOS電晶體之汲極與第二NMOS電晶體之汲極以外，更連接至第一PMOS電晶體之閘極與第一NMOS電晶體之閘極，以形成一回授機制抑制反轉電流。
HIGH ELECTRON MOBILITY GaN-BASED TRANSISTOR STRUCTURE
(2013-07-11)
CHANG EDWARD YI
;
CHANG CHIA-HUA
;
LIN YUEH-CHIN
;
CHEN YU KONG
;
LIU SHIH-CHIEN
A high electron mobility GaN-based transistor structure comprises a substrate, an epitaxial GaN layer formed on the substrate, at least one ohmic contact layer formed on the epitaxial GaN layer, a metallic gate layer formed on the epitaxial GaN layer, and a diffusion barrier layer interposed between the metallic gate layer and the epitaxial GaN layer. The diffusion barrier layer hinders metallic atoms of the metallic gate layer from diffusing into the epitaxial GaN layer, whereby are improved the electric characteristics and reliability of the GaN-based transistor.
Red and Green Fluorosulfide phosphor, Preparation Method and White-Light Emitting Diodes Thereof
(2013-07-11)
Chen Teng-Ming
;
Wu Yun-Chen
Novel red and green fluorosulfide phosphors have a chemical formula of (A1-x-yCexBy)SF, wherein A and B are both trivalent metal ions, 0
Broadband terahertz conductivity and optical transmission of indium-tin-oxide (ITO) nanomaterials
(2013-07-15)
Yang, Chan-Shan
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Chang, Chan-Ming
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Chen, Po-Han
;
Yu, Peichen
;
Pan, Ci-Ling
Indium-tin-oxide (ITO) nanorods (NRs) and nanowhiskers (NWhs) were fabricated by an electron-beam glancing-angle deposition (GLAD) system. These nanomaterials are of interests as transparent conducting electrodes in various devices. Two terahertz (THz) time-domain spectrometers (TDS) with combined spectral coverage from 0.15 to 9.00 THz were used. These allow accurate determination of the optical and electrical properties of such ITO nanomaterials in the frequency range from 0.20 to 4.00 THz. Together with Fourier transform infrared spectroscopic (FTIR) measurements, we found that the THz and far-infrared transmittance of these nanomaterials can be as high as 70% up to 15 THz, as opposed to about 9% for sputtered ITO thin films. The complex conductivities of ITO NRs, NWhs as well films are well fitted by the Drude-Smith model. Taking into account that the volume filling factors of both type of nanomaterials are nearly same, mobilities, and DC conductivities of ITO NWhs are higher than those of NRs due to less severe carrier localization effects in the former. On the other hand, mobilities of sputtered ITO thin films are poorer than ITO nanomaterials because of larger concentration of dopant ions in films, which causes stronger carrier scattering. We note further that consideration of the extreme values of Re{sigma} and Im{sigma} as well the inflection points, which are functions of the carrier scattering time (tau) and the expectation value of cosine of the scattering angle (gamma), provide additional criteria for accessing the accuracy of the extraction of electrical parameters of non-Drude-like materials using THz-TDS. Our studies so far indicate ITO NWhs with heights of similar to 1000 nm show outstanding transmittance and good electrical characteristics for applications such as transparent conducting electrodes of THz Devices. (C) 2013 Optical Society of America
Time-Resolved Spectroscopic and Imaging Studies on Laser Ablation of Molecular Systems: From Mechanistic Study to Bio/Nano Applications
(2013-07-15)
Masuhara, Hiroshi
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應用化學系
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應用化學系分子科學碩博班
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Department of Applied Chemistry
;
Institute of Molecular science
Studies on laser ablation of polymer films, molecular crystals in solution, protein solution, and culture media containing living cells are summarized and considered. Dynamics and mechanism of laser ablation were systematically studied by utilizing time-resolved spectroscopy and imaging; femtosecond-nanosecond transient absorption and emission spectroscopy, nanosecond shadowgraphy, nanosecond-nanometer interferometry, femtosecond surface light scattering imaging. It was confirmed by integrating both data that primary processes of laser ablation can be well understood in the framework of Jablonski diagram. For nanosecond laser ablation of doped polymers, it was demonstrated that cyclic multiphoton absorption is an efficient photothermal conversion process leading to photothermal ablation. For femtosecond laser ablation of dye films, transient pressure mechanism was proposed indicating photomechanical ablation. As applications of laser ablation, nanoparticle preparation, protein crystallization, and manipulation of living cells are presented. Laser ablation of molecular crystals in poor solvent gives small fragments whose size are in a few tens nm. The fabricated nanocolloids are stable without adding detergents and their size was the smallest as nanoparticles produced by the top-down-method. Multiphoton laser ablation of water generates local impulsive force due to bubble formation, shockwave propagation, and local convection flow. The force triggers molecular and protein crystallization in their supersaturated solutions, whose mechanisms are described and considered. The impulsive force is also very useful for manipulating living cells and its high potential was confirmed by examining cell functions such as division, differentiation, death, and migration. Finally summary and future plan are presented.
High spectral efficient W-band OFDM-RoF system with direct-detection by two cascaded single-drive MZMs
(2013-07-15)
Huang, Hou-Tzu
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Lin, Chun-Ting
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Ho, Chun-Hung
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Liang, Wan-Ling
;
Wei, Chia-Chien
W-band wireless transmission has attracted a lot of interest due to its wider available bandwidth (i.e. 75-110 GHz). In this article, we propose a direct-detection orthogonal frequency division multiplexing radio over fiber (OFDM-RoF) system via two cascaded single-drive MZMs at center frequency of 103 GHz. We discuss maximum bandwidth of different modulation formats under forward error correction (FEC) threshold (3.8x10(-3)). Up to 40-Gbps 16-QAM OFDM signals is achieved over 25-km fiber and 2-m wireless transmission. To overcome the penalty from uneven frequency response, bit-loading algorithm is applied to discuss data rate and spectral efficiency with signal bandwidth from 5 to 10 GHz. With 10-GHz bandwidth, 46.4-Gb/s data rate and 4.64-bit/s/Hz spectral efficiency was achieved. To achieve 40-Gbps data rate, the required bandwidth of OFDM signal with bit-loading is 2 GHz less than that without bit-loading. (C) 2013 Optical Society of America
Coherently wavelength injection-locking a 600-mu m long cavity colorless laser diode for 16-QAM OFDM at 12 Gbit/s over 25-km SMF
(2013-07-15)
Li, Yi-Cheng
;
Chi, Yu-Chieh
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Cheng, Min-Chi
;
Lu, I-Cheng
;
Chen, Jason
The coherent injection-locking and directly modulation of a long-cavity colorless laser diode with 1% end-facet reflectance and weak-resonant longitudinal modes is employed as an universal optical transmitter to demonstrated for optical 16-QAM OFDM transmission at 12 Gbit/s over 25 km in a DWDM-PON system. The optimized bias current of 30 mA (similar to 1.5Ith) with corresponding extinction ratio (ER) of 6 dB and the external injection power of -9 dBm is (are) required for such a wavelength-locked universal transmitter to carry the 16-QAM and 122-subcarrier formatted OFDM and data-stream. By increasing external injection-locking from. 9 dBm to 0 dBm, the peak-to-peak chirp of the OFDM data stream reduces from 7.7 to 5.4 GHz. The side mode suppression ratio (SMSR) of up to 50 dB is achieved with wider detuning range between -0.5 nm to 2.0 nm under an injection power of 0 dBm. By modulating such a colorless laser diode with an OFDM data stream of 122 subcarriers at a central carrier frequency of 1.5625 GHz and a total bandwidth of 3 GHz, the transmission data rate of up to 12 Gbit/s in standard single-mode fiber over 25 km is demonstrated to achieve an error vector magnitude (EVM) of 5.435%. Such a universal colorless DWDM-PON transmitter can deliver the optical OFDM data-stream at 12 Gbit/s QAM-OFDM data after 25-km transmission with a receiving power sensitivity of -7 dBm at BER of 3.6x10(-7) when pre-amplifying the OFDM data by 5 dB. (C) 2013 Optical Society of America
Mechanism of Schottky barrier height modulation by thin dielectric insertion on n-type germanium
(2013-07-15)
Tsui, Bing-Yue
;
Kao, Ming-Hong
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電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Although high channel electron mobility has been reported after some passivation techniques, the performance of n-channel Ge metal-oxide-semiconductor field-effect transistor is still limited by the high Schottky barrier height at the metal/n-Ge contact interface, which comes from the Fermi level pinning effect. Recent experiments demonstrated that the Schottky barrier height can be reduced by inserting a thin dielectric layer between metal and Ge. However, the mechanism has not been well clarified. In this paper, the metal induced gap state model, the dipole layer model, and the fixed charge model are verified by varying contact metals, dielectric thicknesses, as well as the annealing temperatures. The pinning factor is improved slightly by dielectric insertion but its value is independent of the dielectric thickness and is still much lower than the ideal value of the non-pinning case. This pinning effect is consistent with the Fermi level pinning at the metal/TiO2 interface. After thermal process, no interfacial layer forms at the TiO2/Ge interface and the TiO2 crystallizes gradually after annealing but the Schottky barrier height increases. Since the amount of fixed charges in the thin dielectric layer estimated from a metal-insulator-semiconductor structure is about 2 x 10(11) cm(-2) and is insufficient to produce the observed 0.5 eV Schottky barrier height reduction, it is thus recommended that the main mechanism comes from the change of interface dipoles and the annealing effect is attributed to the short-range ordering of the TiO2 layer. Furthermore, dielectric with low conduction band offset which has good thermal stability should be explored. (C) 2013 AIP Publishing LLC.
Electronic relaxation and coherent phonon dynamics in semiconducting single-walled carbon nanotubes with several chiralities
(2013-07-15)
Kobayashi, Takayoshi
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Nie, Zhaogang
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Du, Juan
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Okamura, Kotaro
;
Kataura, Hiromichi
Coherent phonon (CP) dynamics and electronic relaxation in single-walled carbon nanotubes (SWNTs) are investigated in femtosecond pump-probe experiments. Using a sensitive multichannel lock-in amplifier, chirality-specific electronic relaxation and vibrational dynamics are resolved in SWNT ensembles composed of several chiral systems without the need for selective isolation of the different species by purification. The dynamics of vibrational wave packets are studied based on oscillatory changes in the absorbance of the systems. Modulations corresponding to the radial breathing mode (RBM), observed in the time traces of the absorbance change for the four chiral systems (6,4), (6,5), (7,5), and (8,3), have been analyzed in detail. The vibrational modes of the CP spectra are identified from the two-dimensional distribution of probe photon energy versus Fourier frequency. Resonance conditions and mode frequencies lead to definite chirality assignments. Coherent RBM phonon generation is analyzed using the probe photon energy-dependent amplitude profiles as a result of the spectral shift induced by wave-packet motion on the potential surface. The present study clarifies that the observed probe photon energy dependence is due to both the imaginary and real parts of the third-order susceptibility, corresponding to Raman (and Raman-like) gain and loss processes and to molecular phase modulation, respectively. The imaginary part is the dominant contribution to the modulation in the difference absorbance. It shows probe photon energy dependence in the form of a difference in absorbed photon energy between the spectra that are shifted and unshifted with vibrational frequency. The size of the Huang-Rhys factors from the difference fitting to the (6,4), (6,5), and (8,3) systems are 0.26, 0.32, and 0.75, respectively. The trend of the factors originates in the stiffness differences of the SWNT structures. The real part depends on the derivative of the absorbed photon energy spectrum due to cross-phase modulation, resulting from the change in refractive index during the molecular vibrations. This process induces a probe spectral change, as evidenced by first-derivative fitting using a small number of data points of probe photon energies. The effective nonlinear refractive index for each chiral system is determined to range from 0.2 to 3.1 x 10(-17) cm(2)/W.
High-Accuracy Waveguide Leaky-Mode Analysis Using a Multidomain Pseudospectral Frequency-Domain Method Incorporated With Stretched Coordinate PML
(2013-07-15)
Wang, Chih-Yu
;
Liu, Hsuan-Hao
;
Chung, Shih-Yung
;
Teng, Chun-Hao
;
Chen, Chung-Ping
A recently developed pseudospectral frequency-domain (PSFD) method employing a penalty scheme is further incorporated with stretched coordinate perfectly matched layers (PMLs) in order to solve waveguide leaky modes. Several standard leaky-mode slab and circular waveguides, including the W-type and M-type ones, are examined first by solving their complex effective indexes and field profiles, showing that the PSFD method achieves computational accuracy on the order of. Then, this high-accuracy solver is used to analyze waveguide structures with more complicated geometries, such as the leaky six-air-hole fiber, for which self convergence of accuracy in calculated effective indexes is demonstrated to be on the orders of, and two rectilineal waveguides with sharp corners, i.e., the rib waveguide and the photonic wire. Comparison of the PSFD method obtained results for these more complicated waveguide structures with those from other methods in the literature is presented and discussed.
High-power high-repetition-rate subpicosecond monolithic Yb:KGW laser with self-mode locking
(2013-07-15)
Zhuang, W. Z.
;
Chang, M. T.
;
Liang, H. C.
;
Chen, Y. F.
;
電子物理學系
We report on a high-power subpicosecond monolithic self-mode-locked Yb:KGW laser with the pulse repetition rate up to several tens of gigahertz. Experimental results reveal that not only the repetition rate but also the pulse width depend on the length of the laser crystal. Using a coated Yb:KGW crystal with a length of 3.36 mm, mode-locked pulses with pulse duration of 850 fs at the repetition rate of 22.4 GHz have been achieved. With an incident pump power of 10.5 W, an average output power of 3.6 W was achieved which corresponds to the optical conversion efficiency of 34.3%. (C) 2013 Optical Society of America