Browsing by Author "Lee, HY"

Now showing 1 - 20 of 26

A macro model of silicon spiral inductor
(2002-05-01)
Su, CY
;
Chen, LP
;
Chang, SJ
;
Tseng, BM
;
Lin, DC
A new automatic parameter extraction method for modeling Of silicon Spiral inductors is presented. The Concepts on self-resonance frequency (f(sr)) and quality factor of a spiral inductor are utilized to develop the concise extraction procedures. In the mean time, the presented extraction procedures are programmed as a macro to execute all the extractions automatically and shorten the extraction time effectively. Without any additional optimization or curve fitting, almost all the patterns of S-parameters between the measured and the simulation of extracted data implemented with the extraction macro are less than 5%. The programmed extraction macro makes it fast and accurate to extract and characterize the behaviours or silicon-based spiral inductors with different structures and substrate resistivities. It provides a concrete foundation commercial silicon radiofrequency (RF) Circuit design to realizing on-chip silicon RF integrated circuits. Furthermore, the directly extracted equivalent model parameters, without an optimization, also provide a rule to fairly, effectively and phsically judge the performance of a spiral inductor. (C) 2002 Elsevier Science Ltd. All rights reserved.
An automatic macro program for radio frequency MOSFET characteristics analysis
(2001-10-01)
Su, CY
;
Chang, SJ
;
Chen, LP
;
Ho, YP
;
Huang, GW
The parameter extraction language (PEL) in Agilent IC-CAP software is used to develop an automatic macro program for the analysis of the characteristics of RF MOSFETs. By using this powerful macro program, the time spent on the measurement of the MOSFET characteristics and the related analysis is effectively reduced. This macro program permits a fast and accurate method to obtain the DC and RF characteristics of MOSFETs with different device geometries and operating conditions. It is also suitable for high volume measurements and analyses of MOSFET, and provides a solid jou 71 dation for RF circuit design.
Bayesian estimation for time-series regressions improved with exact likelihoods
(2004-10-01)
Chen, CWS
;
Lee, JC
;
Lee, HY
;
Niu, WF
;
統計學研究所
We propose an estimation procedure for time-series regression models under the Bayesian inference framework. With the exact method of Wise [Wise, J. (1955). The autocorrelation function and spectral density function. Biometrika, 42, 151-159], an exact likelihood function can be obtained instead of the likelihood conditional on initial observations. The constraints on the parameter space arising from the stationarity conditions are handled by a reparametrization, which was not taken into consideration by Chib [Chib, S. (1993). Bayes regression with autoregressive errors: A Gibbs sampling approach. J. Econometrics, 58, 275-294] or Chib and Greenberg [Chib, S. and Greenberg, E. (1994). Bayes inference in regression model with ARMA(p, q) errors. J. Econometrics, 64, 183-206]. Simulation studies show that our method leads to better inferential results than their results.
Binding effect of surface-modified cadmium sulfide on the microstructure of PS-b-PEO block copolymers
(2004-06-15)
Jeng, US
;
Sun, YS
;
Lee, HY
;
Hsu, CH
;
Liang, KS
CdS nanoparticles with surfaces modified by mercaptoethanol have been synthesized for greater solubility in dimethylformamide (DMF) and the ability to preferentially bind to the poly(ethylene oxide) (PEO) blocks of polystyrene-block-poly(ethylene oxide) (PS-b-PEO) copolymer. The size of the surface-modified CdS nanoparticles (M-CdS) in DMF can be characterized by the Schultz distribution of a mean radius of 18.4 Angstrom and a polydispersity of 0.5, using small-angle X-ray scattering (SAXS). These M-CdS nanoparticles can further disperse in the PS-b-PEO, with a slightly larger mean radius than that observed in DMF. The uptake of M-CdS nanoparticles for the PEO blocks of the PS-b-PEO saturates around 7% in volume fraction. The binding of the nanoparticles promotes a segregation of the PEO/nanoparticles and leads to spherical PEO/M-CdS microdomains in the composite film with a greatly enhanced thermal stability. The structural information obtained from X-ray scattering agrees well with the transmission electron microscopy images and differential scanning calorimetry results.
Characteristics of deep levels in As-implanted GaN films
(2002-09-02)
Lee, L
;
Lee, WC
;
Chung, HM
;
Lee, MC
;
Chen, WH
Hall, current-voltage and deep level transient spectroscopy measurements were used to characterize the electric properties of n-type GaN films implanted with As atoms. After 800 degreesC thermal annealing for 60 min, one additional deep level located at E-C-0.766 eV was found in the films. We presume this induced trap is an arsenic-related point defect, most likely antisite in nature. (C) 2002 American Institute of Physics.
Composition determination of semiconductor quantum wires by X-ray scattering
(2005-02-28)
Hsu, CH
;
Tang, MT
;
Lee, HY
;
Huang, CM
;
Liang, KS
Self-assembled semiconductor nano-structures, e.g. quantum dots and wires, have recently attracted intensive interests due to their potential applications in optoelectronic industry. Strain field, compositional profile, size, and shape are the key factors determining the physical properties of these nano-structures. However, due to their mesoscopic size, it is a challenge to accurately determine those geometric and chemical parameters. In this work, we present the structural and compositional investigation of GaAs quantum wires grown on InP(0 0 1) substrates by grazing incidence X-ray scattering. In particular, we applied resonant X-ray scattering to determine the compositional distribution within the wires. With properly chosen diffraction peak and X-ray energy range, the profile of energy scan is highly sensitive to the composition of the region with selected lattice constant. As compared to other composition determination methods, which rely on the intensity ratio either between a strong and a weak diffraction or between the same Bragg diffraction collected at different energies, the profile of energy scan is not affected by the significant intensity modulation introduced by inter-wire correlation. Therefore, this method can be applied to systems of various surface morphologies and ordered structures and still provides compositional information with high accuracy and good resolution. (C) 2004 Elsevier B.V. All rights reserved.
Critiquing contractors' scheduling by integrating rule-based and case-based reasoning
(2004-09-01)
Dzeng, RJ
;
Lee, HY
;
土木工程學系
;
Department of Civil Engineering
Nowadays, projects involve many activities. Hence, the review process requires the scheduler to be experienced both in field operations and in computer scheduling software. However, the dilemma faced by contractors is that many senior project managers are experienced in the field but not in computers, whereas many young engineers are skilled in computers but not in field operations. This work proposes a generalized framework to represent schedule knowledge, and a computer-based system that analyzes a project schedule and offers corrective advice on potential errors by integrating case-based and rule-based reasoning. (C) 2004 Elsevier B.V. All rights reserved.
Crystallization kinetics and crystallization behavior of syndiotactic polystyrene/clay nanocomposites
(2001-09-01)
Tseng, CR
;
Lee, HY
;
Chang, FC
;
應用化學系
;
Department of Applied Chemistry
We investigated the effects of montmorillonite (clay) on the crystallization kinetics of syndiotactic polystyrene (sPS) with isothermal differential scanning calorimetry analyses. The clay was dispersed into the sPS matrix via melt blending on a scale of 1-2 nm or up to about 100 nih, depending on the surfactant treatment. For a crystallization temperature of 240 degreesC, the isothermal crystallization data were fitted well with the Avrami crystallization equation. Crystallization data on the kinetic parameters (i.e., the crystallization rate constant, Avrami exponent, clay content, and clay/surfactant cation-exchange ratio), were also investigated. Experimental results indicated that the crystallization rate constant of the sPS nanocomposite increased with increasing clay content. The clay played a vital role in facilitating the formation on the thermodynamically more favorable all-beta -form crystal when the sPS was melt-crystallized. (C) 2001 John Wiley & Sons, Inc.
Effect of coplanar probe pad design on noise figures of 0.35 mu m MOSFETs
(2000-07-20)
Su, CY
;
Chen, LP
;
Chang, SJ
;
Huang, GW
;
Ho, YP
The effects of different coplanar ground-signal-ground (GSG) probe pads on the noise figure characteristics of submicron MOSFETs are presented. Devices with top-level metal as probe pads shielded by grounded bottom-level metal possess the most appropriate probe pad structure for characterising the noise performance of MOSFETs. Equivalent circuits of the probe pads are used to explain the different noise behaviours.
Effects of phase transformation on photoluminescence behavior of ZnO : Eu prepared in different solvents
(2006)
Yang, CC
;
Cheng, SY
;
Lee, HY
;
Chen, SY
;
材料科學與工程學系
Europium doped zinc oxide (Eu:ZnO) powder has been prepared by mixing ZnO and Eu2O3 in deionized water and acetone solvents. The influence of phase transformation of Eu-doped ZnO powders mixed in different solvents on the luminescence behavior has been investigated. When the powder was mixed in deionized water and then sintered at high temperatures, Eu3+ ions were detected in the ZnO matrix. The intrinsic red photoluminescence (D-5(0)->F-7(2)) of Eu3+ was easily shielded by the ZnO intrinsic defect as the samples were excited with 325 nm short wavelength as a consequence of the energy level of Eu-Zn(circle) (0.19 eV) being closer to conduction band than the one of Zn-1(circle circle) (0.22 eV). Therefore, no red emission can be detected. In contrast, as the Eu-doped ZnO powder was mixed in acetone solvent (without OH-), no Eu3+ ions could be detected in the ZnO matrix. In addition, the red emission could be detected not only under excitation with long wavelength (532 nm) but also at short wavelength (325 nm). (C) 2005 Elsevier Ltd and Techna Group S.r.l. All rights reserved.
Effects of yttrium codoping on photoluminescence of erbium-doped TiO2 films
(2001-12-01)
Ting, CC
;
Chen, SY
;
Hsieh, WF
;
Lee, HY
;
材料科學與工程學系
Er3+-Y3+ codoped TiO2 films were prepared on a fused silica substrate by the sol-gel process. The effect of Y3+ codoping on the similar to1.54 mum photoluminescence (PL) properties of Er3+-doped TiO2 films are investigated. Enhancement of PL properties due to Y3+ codoping by a factor of 10 for intensity and of 1.5 for the full width at half maximum in comparison with the Er3+-Al3+ codoped SiO2 system has been observed in the film annealed at Er3+:Y3+:Ti4+=5:30(similar to 50):100. Extended x-ray absorption fine structure measurements show that the local chemical environment of Er3+ ions in the Er3+-Y3+ codoped TiO2 films is similar to that in Er2O3. The average spatial distance between Er3+ ions is enlarged due to the partial substitution of Y3+ for Er3+ ions in the Er2O3-like local structure. It is believed that the more intense PL emission of the Er3+-Y3+ codoped TiO2 films can be attributed to the better dispersion and distorted local structure of Er3+ ions in the TiO2 host matrix by yttrium codoping. (C) 2001 American Institute of Physics.
Frequency stabilizations of GaN blue diode laser
(2001)
Chang, F
;
Lee, HY
;
Huang, MS
;
Wang, SC
;
光電工程學系
Miscibility, specific interactions, and self-assembly behavior of phenolic/polyhedral oligomeric silsesquioxane hybrids
(2004-03-15)
Lee, YJ
;
Kuo, SW
;
Huang, WJ
;
Lee, HY
;
Chang, FC
The miscibility of a phenolic resin with polyhedral oligomeric silsesquioxane (POSS) hybrids and the specific interactions between them were investigated with Fourier transform infrared (FTIR) spectroscopy and wide-angle X-ray diffraction (WAXD). An analysis of the morphology and microstructure was performed with polarized optical microscopy and atomic force microscopy (AFM). The interassociation equilibrium constant between the phenolic resin and POSS (38.7) was lower than the self-association equilibrium constant of pure phenolic (52.3) according to the Painter-Coleman association model. This result indicated that POSS was partially miscible with the phenolic resin. A polarized optical microscopy image of a phenolic/POSS hybrid material (20 wt % POSS) indicated that the crystals of POSS were arranged evenly in the phenolic matrix; the self-assembled array of POSS crystals was also confirmed by AFM. This phenomenon was consistent with the FTIR spectroscopy and WAXD analyses. (C) 2004 Wiley Periodicals, Inc.
Physical characteristics and infrared fluorescence properties of sol-gel derived Er3+-Yb3+ codoped TiO2
(2003-08-01)
Ting, CC
;
Chen, SY
;
Lee, HY
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Er3+-Yb3+ codoped TiO2 films were prepared on fused silica by sol-gel processes. The Yb3+ codoping effect on the physical characteristics and similar to1.54 mum photoluminescence (PL) properties of Er3+-doped TiO2 films was investigated. Maximum similar to1.54 mum PL intensity occurs in Er3+ (5 mol %)-Yb-3+ (30 mol %) codoped TiO2 samples annealed at 700degreesC. However, when the concentration of Yb3+ ions is more than 30 mol %, the back energy transfer effect from Er3+ to Yb3+ will deteriorate the similar to1.54 mum PL efficiency. Extended x-ray absorption fine structure measurements show that the average spatial distance between Er3+ ions is slightly decreased due to the partial substitution of Yb3+ for Er3+ ions in the local structure. The Yb3+ ion in the Er3+-Yb3+ codoped TiO2 samples not only plays the role of disperser but is also a sensitizer of the Er3+ ion. This dual effect leads to larger PL intensity in the Er3+-Yb3+ codoped TiO2 system in comparison with Er3+-Y3+ codoped TiO2 samples. Compared with SiO2 films with Er3+ (5 mol%)-Yb3+ (30 mol %) codoped and annealed at optimal temperature of 985degreesC, the Er3+ -Yb3+ codoped TiO2 film obtains better PL properties at lower annealing temperature. (C) 2003 American Institute of Physics.
Physical characterization of ZnO nanorods grown on Si from aqueous solution and annealed at various atmospheres
(2005-11-01)
Yang, CC
;
Chen, SY
;
Lee, HY
;
材料科學與工程學系
;
Department of Materials Science and Engineering
High-density ZnO nanorods were vertically grown on Si coated with ZnO film (ZnO/Si substrate) from aqueous solution at low temperatures. The ZnO nanorods after annealed in various atmospheres still present good c-axis crystalline character but exhibit remarkable differences in photoluminescence (PL) properties. Enhancement of PL properties due to N-2-atmosphere annealing for ultraviolet emission can be attributed to the reduction of defect density because the nonparamagnetic singly ionized state (N-) can easily occupy the oxygen vacancies as evidenced by Raman spectroscopy and electron paramagnetic resonance spectrometry. The extended x-ray absorption fine structure reveals that the annealing atmosphere shows no apparent influence on the deep-level defects of ZnO nanorods except that some ions are possibly trapped or adsorbed on the surface of the ZnO nanorods. (c) 2005 American Vacuum Society.
Preparation and characterization of polystyrene-clay nanocomposites by free-radical polymerization
(2002-08-15)
Tseng, CR
;
Wu, JY
;
Lee, HY
;
Chang, FC
;
應用化學系
The polymerizable cationic surfactant, vinylbenzyldimethylethanolammouium chloride (VBDEAC), was synthesized to functionalize montmorillonite (MMT) clay and used to prepare exfoliated polystyrene-clay nanocomposites. The organophilic MMT was prepared by Na(+) exchanged montmorillonite and ammonium cations of the VBDEAC in an aqueous medium. Polystyrene-clay nanocomposites were prepared by free-radical polymerization of the styrene containing intercalated organophilic MMT. Dispersion of the intercalated montmorillonite in the polystyrene matrix determined by X-ray diffraction reveals that the basal spacing is higher than 17.6 nm. These nanocomposites were characterized by differential scanning calorimetry (DSC), transmission electron micrograph (TEM), thermal gravimetric analysis (TGA), and mechanical properties. The exfoliated nanocomposites have higher thermal stability and better mechanical properties than the pure polystyrene. (C) 2002 Wiley Periodicals, Inc.
Preparation and crystallization behavior of syndiotactic polystyrene-clay nanocomposites
(2001-12-01)
Tseng, CR
;
Wu, JY
;
Lee, HY
;
Chang, FC
;
應用化學系
Syndiotactic polystyrene/modified-clay nanocomposites have been prepared by solution blending by mixing pure s-PS and organophilic clay with adsorbed cetyl pyridium chloride (CPC) in dichlorobenzene. The dispersability of the clay in syndiotactic polystyrene/modified-clay nanocomposites was studied using X-ray and transmission electron microscopy. The clay is well dispersed into the s-PS matrix using solution blending with scale in 1-2 nm or in a few tenths similar to 100 nm depending on surfactant treatment. The CPC is partially compatible with s-PS and allows syndiotactic polystyrene chains intercalating into clay layers. The crystallization behavior of alpha- and beta -crystals for syndiotactic polystyrene nanocomposite has been thoroughly examined using the Fourier transform infrared and differential scanning calorimetry. Our results further demonstrate that the presence of the clay plays a vital role in facilitating the formation on the thermodynamically more favorable beta form crystal when the s-PS is melt- or cold-crystallized. (C) 2001 Elsevier Science Ltd. All rights reserved.
Properties of nitrogen-implanted p-type ZnO films grown on Si3N4/Si by radio-frequency magnetron sputtering
(2004-06-14)
Lin, CC
;
Chen, SY
;
Cheng, SY
;
Lee, HY
;
材料科學與工程學系
An nitrogen-implanted p-type ZnO film has been grown on a Si substrate buffered with Si3N4 using radio-frequency magnetron sputtering. The Si3N4 buffer layer can effectively improve film stoichiometry and reduce the formation of oxygen vacancies compared to ZnO on Si. The electrical properties of the p-type ZnO films implanted with 5x10(12)-1x10(14) cm(-2) N+ dose show a hole concentration of 5.0x10(16)-7.3x10(17) cm(-3), hole mobility of 2.51-6.02 cm(2)/V s, and resistivity of 10.11-15.3 Omega cm. The p-type ZnO films also showed an excellent crystallinity and a strong ultraviolet emission peak near 3.30 eV at room temperature. Moreover, as evidenced by extended x-ray absorption fine structure analysis, the local structure of the p-type ZnO films was changed due to the substitution of nitrogen ions for oxygen ions in p-type ZnO films. Our finding of p-type ZnO films grown on a Si3N4/Si substrate could provide a simple method to fabricate reproducible p-type ZnO films on silicon substrate for the development of large-scale optoelectronic integration device. (C) 2004 American Institute of Physics.
Quasi-two-dimensional simulation of scour and deposition in alluvial channels
(1997-07-01)
Lee, HY
;
Hsieh, HM
;
Yang, JC
;
Yang, CT
;
土木工程學系
Most existing sediment routing models are one-dimensional models and hence they cannot be used Co simulate lateral channel bed deformations. Conversely, a two-dimensional model is computationally time consuming, and is not suitable for long-term simulation. Using the stream tube concept, a one-dimensional model is extended to a quasi-two-dimensional model in this study. It is capable of simulating lateral variations of channel cross section through the adjustments of stream tube boundaries. The model has an option to treat the suspended load and bed load separately and hence is able to simulate the deposition behavior of the suspended sediment under a nonequilibrium process. The model also provides options to solve either de Saint Venant equation or energy equation and hence can be applied in both steady and unsteady flow conditions. An assessment of this model's performance has been conducted through a comparison to an analytical solution and a set of experimental data, The application of this model to the Keelung River and the Shiemen Reservoir in Taiwan also gave convincing results.
Quasi-two-dimensional simulation of scour and deposition in alluvial channels - Closure
(1999-02-01)
Lee, HY
;
Hsieh, HM
;
Yang, JC
;
Yang, CT
;
土木工程學系