Browsing by Issue Date, starting with "2003-01-20"

Now showing 1 - 20 of 72962

A 1.2-V fully integrated 2.4-GHz low-noise amplifier in 0.35-mu m CMOS technology
(2003-01-20)
Meng, CC
;
Chiang, MH
;
Wu, TH
;
電信工程研究所
;
Institute of Communications Engineering
A 1.2-V fully integrated 0.35-mum inductively degenerated common source CMOS low-noise amplifier has been demonstrated at 2.4 GHz in this paper. A simple common source configuration can be operated at lower voltage and has lower output impedance when compared with a conventional high output impedance cascode LNA circuit topology. The input matching inductance, output matching inductance, and source degeneration inductance are integrated on a single chip. The fully integrated 2.4-GHz CMOS LNA has 5.27-dB power gain, 17-dB input return loss, 15413 output return loss, 4-dB noise figure, and -1-dBm IIPIdB and 8-dBm IIP3 at V-dd = 1.2 V and I-dd = 10 mA, respectively. (C) 2003 Wiley Periodicals, Inc.
A novel method for short leaky-wave antennas to suppress the reflected wave
(2003-01-20)
Wang, CJ
;
Guan, HL
;
Jou, CF
;
傳播研究所
;
Institute of Communication Studies
A method to suppress the back lobe of a short leaky-wave antenna (LWA) by using an aperture-fed patch antenna on the backside is demonstrated in this paper. The aperture-fed patch antenna is connected to the open end of the LWA. This design offers another radiation path of the reflected wave and creates another radiation pattern on the back plane of the substrate. Experimental results show that the suppression of the reflected wave can be 10 dB at 10.0 GHz with an LWA length of 6 cm (2 wavelengths). Compared to the conventional design, this novel structure can radiate as efficiently as LWA at a length a wavelengths. The two radiation patterns on different planes have great potential in many applications and can provide more flexibility to traditional designs. (C) 2003 Wiley Periodicals, Inc.
Identification and characterization of KvgAS, a two-component system in Klebsiella pneumoniae CG43
(2003-01-21)
Lai, YC
;
Lin, GT
;
Yang, SL
;
Chang, HY
;
Peng, HL
A two-component system encoding gene cluster kvgAS that is present only in virulent Klebsiella pneumoniae CG43 was isolated and its sequence determined. RT-PCR and Southern analysis demonstrated that kvgAS is organized as an operon. No apparent effect of a kvgS deletion on bacterial virulence was observed in a mouse peritonitis model. In the presence of paraquat or 2,2-dipyridyl, the activity of kvgAS promoter in the kvgS mutant was found to be reduced to half of the level in the wild-type strain. The data suggest that the KvgAS system is autoregulated and plays a role in countering free radical stresses and sensing iron-limiting conditions. (C) 2002 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.
Overflow control in mobile communication using N-class replacement
(2003-01-23)
Sue, KL
;
Lo, CC
;
資訊管理與財務金融系註：原資管所+財金所
;
Department of Information Management and Finance
A strategy called N-class replacement (NR) policy is proposed to overcome visitor location register (VLR) overflow in a mobile communication system. The NR policy requires only few bits in the VLR record. It is feasible for separated VLR databases in real mobile networks. For the rate of excellent replacement, the simulation results show that the NR policy outperforms currently proposed policies.
Triplet-to-singlet exciton formation in poly(p-phenylene-vinylene) light-emitting diodes
(2003-01-24)
Lin, LC
;
Meng, HF
;
Shy, JT
;
Horng, SF
;
Yu, LS
The triplet to singlet exciton formation ratio in a MEH-PPV light-emitting diode is measured by comparing the triplet-induced absorptions with optical and electric excitations at the same singlet exciton density. The ratio is a strong universal decreasing function of the averaged electric field. Using 4 ns for singlet to triplet intersystem crossing time, the ratio is significantly larger than the spin-independent value 3 at intermediate field but is reduced to about 2 for higher field.
Preparation and cathodoluminescence of ZnO phosphor
(2003-01-30)
Lin, CH
;
Chiou, BS
;
Chang, CH
;
Lin, JD
;
電子工程學系及電子研究所
Zinc oxide phosphors (ZnO:Zn) were prepared with solid state sintering of ZnO powders with ZnS and screen printed onto ITO-coated glass substrates to form a thin layer. Structural characterization carried out by X-ray diffraction (XRD) analysis suggests that the Zn atoms originated from the decomposition of ZnS, and diffuse to occupy the oxygen vacancies in the host lattice. Both lattice parameters a and c decrease slightly with the increase of ZnS content and/or firing temperature. The cathodoluminescent (CL) peak band varies with ZnS content and ranges from 494 to 508 nm, which is close to the green band of ZnO phosphor. Various mechanisms have been proposed in literatures to explain the origin of the green emission band. Among them, the presence of oxygen vacancies and trace ZnS residue are possible causes for the green emission in this study. CL spectra and CIE color loci suggest that ZnO:Zn phosphor with 5 wt.% ZnS can be. used as a green primary for color picture tubes. (C) 2002 Elsevier Science B.V. All rights reserved.
Role of an intermediate phase (Ba,Sr)(2)Ti2O5CO3 in doped (Ba0.7Sr0.3)TiO3 thin films
(2003-01-30)
Chen, SY
;
Wang, HW
;
Huang, LC
;
材料科學與工程學系
;
Department of Materials Science and Engineering
(Ba0.7Sr0.3)TiO3 (BST) thin films doped with La, Nb, and Mg ions were prepared by metal-organic deposition method (MOD) on Pt/Ti/SiO2/Si substrates. An intermediate phase formed under an annealing temperature of 550-650 degreesC, and disappeared at higher temperatures during the formation of BST. The intermediate phase was analyzed by X-ray diffraction (XRD) analysis, transmission electron microscopy (TEM), Fourier transform-infrared spectroscopy (FT-IR) and Raman spectra and found to be an oxycarbonate with a chemical formula of (Ba,Sr)(2)TiO5CO3. The stability of this intermediate phase increased with the addition of dopants, irrespective of doping types. It is proposed that distortion of crystal structure, physical constraint in the two-dimensions and small grain size favor the existence of poor crystallized (Ba,Sr)(2)Ti2O5CO3. (C) 2002 Elsevier Science B.V. All rights reserved.
Atomistics of Ge deposition on Si(100) by atomic layer epitaxy
(2003-01-31)
Lin, DS
;
Wu, JL
;
Pan, SY
;
Chiang, TC
;
物理研究所
Chlorine termination of mixed Ge/Si(100) surfaces substantially enhances the contrast between Ge and Si sites in scanning tunneling microscopy observations. This finding enables a detailed investigation of the spatial distribution of Ge atoms deposited on Si(100) by atomic layer epitaxy. The results are corroborated by photoemission measurements aided by an unusually large chemical shift between Cl adsorbed on Si and Ge. Adsorbate-substrate atomic exchange during growth is shown to be important. The resulting interface is thus graded, but characterized by a very short length scale of about one monolayer.
An all-digital phase-locked loop for high-speed clock generation
(2003-02-01)
Chung, CC
;
Lee, CY
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
An all-digital phase-locked loop (ADPLL) for high-speed clock generation is presented in this brief. The proposed ADPLL architecture uses both a digital control mechanism and a ring oscillator and, hence, can be implemented with standard cells. The ADPLL implemented in a 0.3-mum one-poly-four-metal CMOS process can operate from 45 to 510 MHz and achieve worst case frequency acquisition in 46 reference clock cycles. The power dissipation of the ADPLL is 100 mW (at 500 MHz) with a 3.3-V power supply. From chip measurement results, the P-k-P-k jitter of the output clock is < 70 ps; and the root-mean-square jitter of the output clock is < 22 ps. A systematic way to design the ADPLL with the specified standard cell library is also presented in this brief. The proposed ADPLL can easily be ported to different processes in a short time. Thus, it can reduce the design time and design complexity of the ADPLL, making it very suitable for system-on-chip applications.
Low temperature radio-frequency-sputtered (Ba, Sr)TiO3 films on Pt/TiN/Ti/Si substrates with various oxygen/argon mixing ratios
(2003-02-01)
Shye, DC
;
Chiou, BS
;
Lai, MJ
;
Hwang, CC
;
Jiang, CC
(Ba, Sr) TiO3 (BST) films were fabricated on Pt/TiN/Ti/Si substrates by low temperature radio frequency magnetron cosputtering at 300degreesC. Material and electrical properties of BST films sputtered at low temperatures are significantly affected by the O-2/(Ar + O-2) mixing ratio (OMR). Plasma emission spectra indicate that the deposition rate declines at a higher OMR due to oxide formation on the target surface. The dielectric constant of the BST films can reach a maximum of 364 at 5% OMR. The ten-year lifetime of the time-dependent dielectric breakdown implies that the reliability of the capacitor can be enhanced at a higher OMR due to compensation of oxygen vacancies and smaller grain sizes. Current-voltage analysis indicates that the leakage current of the Pt/BST/Pt capacitor is limited by Schottky emission (SE)/Poole-Frenkel emission (PF) at a lower/higher applied field. The applied field boundary between SE and PF shifts toward higher field as OMR increases. Moreover, an energy band model was proposed and this leakage mechanism was discussed. (C) 2003 The Electrochemical Society.
Co-evolution as a computational and cognitive model of design
(2003-02-01)
Maher, ML
;
Tang, HH
;
建築研究所
;
Institude of Architecture
Co-evolutionary design has been developed as a computational model that assumes two parallel search spaces: the problem space and the solution space. The design process iteratively searches each space using the other space as the basis for a fitness function when evaluating the alternatives. Co-evolutionary design can also be developed as a cognitive model of design by characterizing the way in which designers iteratively search for a design solution, making revisions to the problem specification. This paper presents the computational model of co-evolutionary design and then describes a protocol study of human designers looking for evidence of co-evolution of problem specifications and design solutions. The study shows that co-evolutionary design is a good cognitive model of design and highlights the similarities and differences between the computational model and the cognitive model. The results show that the two kinds of co-evolutionary design complement each other, having strengths in different aspects of the design process.
Thermochromism of silver oxide for optical switching layers in volumetric optical disks
(2003-02-01)
Wu, FH
;
Shieh, HPD
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光電工程學系
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Department of Photonics
For reading and writing on a lower targeted recording layer of volumetric optical disks, transmitted laser power is decreased by absorption and reflection of the upper layers. Thus, a layer of thermo-chromatic material, such as silver oxide, has been added as an optical switching layer next to the recording layers to modulate the optical characteristics of the recording layers by the diffraction limited laser beam during writing. The optical switching structure can reduce peak writing laser energy by 42%. Consequently, optical switching layer is promising for volumetric recording to optimize R/W performance.
Effect of aging treatment on the mechanical properties of C-250 maraging steel by flow forming
(2003-02-01)
Lee, IK
;
Chou, CP
;
Cheng, CM
;
Kuo, IC
;
機械工程學系
The technique of forward flow forming has been used to produce a long, thin walled tube made of C-250 maraging steel. The forward flow forming can save raw material, increase strength, and reduce the production process time. Because the work hardening effect on solution-treated C-250 using flow forming is minimal, the flow-formed tube requires an additional heat treatment to obtain higher hardness and strength. With the direct aging treatment, low elongation values are obtained, making this treatment unsuitable for the engineering design. It was found that the 540 degreesC/6 h/AC over-aging treatment results in better strength and elongation values. The strengthening phase of the flow-formed C-250 maraging steel was found to be the intermetallic compound of Fe3Mo.
BCS-like superconductivity in MgCNi3
(2003-02-01)
Lin, JY
;
Ho, PL
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Huang, HL
;
Lin, PH
;
Zhang, YL
The low-temperature specific heat C(T,H) of the superconductor MgCNi3 has been measured in detail. DeltaC/gamma(n)T(c)=1.97 is estimated from the anomaly at T-c. At low temperatures, the electronic contribution in the superconducting state follows C-es/gamma(n)T(c)approximate to7.96 exp(-1.46T(c)/T). The magnetic-field dependence of gamma(H) is found to be linear with respect to H. T-c estimated from the McMillan formula agrees well with the observed value. All the specific-heat data appear to be consistent with each other within the moderate-coupling BCS context. It is amazing that such a superconductor unstable to ferromagnetism behaves so conventionally. The Debye temperature Theta(D)=287 K and the normal state gamma(n)=33.6 mJ/mol K-2 are determined for the present sample.
Magnetotransport of thick Disordered CuGe Samples
(2003-02-01)
Hsu, Shih-ying
;
Chen, J. Y.
;
Liao, C. T.
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電子物理學系
;
Department of Electrophysics
Ambipolar Schottky barrier silicon-on-insulator metal-oxide-semiconductor transistors
(2003-02-01)
Lin, HC
;
Wang, MF
;
Lu, CY
;
Huang, TY
;
電子工程學系及電子研究所
A novel Schottky barrier silicon-on-insulator metal-oxide-semiconductor field-effect transistor featuring metallic source/drain and an electrical drain junction has been fabricated and characterized. The formation of electrical drain junction, or the field-induced drain (FID), is controlled by a metal field-plate overlying the passivation oxide. Excellent ambipolar operation is demonstrated on the device. Specifically, on/off current ratios up to 10(8) and 10(7) are observed for p- and n-channel operations, respectively. Meanwhile, the off-state leakage current shows very weak dependence on the voltage difference between the main-gate and the drain, highlighting the effectiveness of FID. Finally, negative differential conductance effect is observed for n-channel operation, which is identified as due to dynamic hot electron trapping during device characterization. (C) 2002 Elsevier Science Ltd. All rights reserved.
PECVD-Ti/TiNx barrier with multilayered amorphous structure and high thermal stability for copper metallization
(2003-02-01)
Wu, WF
;
Ou, KL
;
Chou, CP
;
Hsu, JL
;
機械工程學系
Ultrathin (10 nm) Ti films with an amorphous structure were deposited by low temperature (<500 &DEG;C) plasma enhanced chemical vapor deposition (PECVD) using TiCl4 and H-2 as reactants. Ammonia plasma was further employed to post-treat the PECVD-Ti barrier layer to improve barrier properties. An amorphous TiNx layer forms on the surface of the PECVD-Ti layer after ammonia plasma post-treatment. The resulting films have a multilayered amorphous Ti/TiNx structure. Furthermore, the effective resistivity of resulting Ti/TiNx film reduces to 122 μ&UOmega; cm. Improved barrier capability against Cu diffusion is found for the Ti/TiNx barrier layer because the Cu/TiNx /Ti/n(+)-p junction diodes retain low leakage current densities even after annealing at 500 &DEG;C for 1 h. Ti/TiNx barrier layers present lengthened grain structures to effectively impede Cu diffusion, thus acting as much more effective barriers than are conventional Ti and TiN films. (C) 2002 The Electrochemical Society.
Substrate-triggered ESD protection circuit without extra process modification
(2003-02-01)
Ker, MD
;
Chen, TY
;
電機學院
;
College of Electrical and Computer Engineering
A substrate-triggered technique is proposed to improve electrostatic discharge (ESD) protection efficiency of ESD protection circuits without extra salicide blocking and ESD-implantation process modifications in a salicided shallow-trench-isolation CMOS process. By using the layout technique, the whole E.SD protection circuit can be merged into a compact device structure to enhance the substrate-triggered efficiency. This substrate-triggered design can increase ESD robustness and reduce the trigger voltage of the ESD protection device. This substrate-triggered ESD protection circuit with a field oxide device of channel width of 150 mum can sustain a human-body-model ESD level of 3250 V without any extra process modification. Comparing to the traditional ESD protection,design of gate-grounded nMOS (ggnMOS) with silicide-blocking process modification in a 0.25-mum salicided CMOS process, the proposed substrate-triggered design without extra process modification can improve ESD robustness per unit silicon area from the original 1.2 V/mum(2) of ggnMOS to 1.73 V/mum(2).
An analytical approach for the fast design of high-power waveguide windows
(2003-02-01)
Lin, MC
;
Chung, HM
;
Burke, A
;
電子物理學系
;
Department of Electrophysics
An analytical approach is presented to achieve the fast design of high-power waveguide windows. The analytical calculation is compared with the result of numerical simulation via the finite-element code high frequency structure simulator and the experiments of W-band waveguide windows performed at the Stanford Linear Accelerator Center (SLAC), Stanford University, Stanford, CA. The closed form has been carried out to enhance the accuracy and efficiency, and the exact calculation agrees with the experimental results and the numerical simulation very well. (C) 2002 Elsevier Science B.V. All rights reserved.
Information searching strategies in Web-based science learning: The role of Internet self-efficacy
(2003-02-01)
Tsai, MJ
;
Tsai, CC
;
師資培育中心
;
Center of Teacher Education
The purpose of this study was to explore students' information searching strategies in Web-based science learning activities and further examine the influence of students' Internet self-efficacy on these strategies. Eight subjects were randomly selected from a pool of 73 college freshmen based on mixed genders and Internet self-efficacy levels. In-depth case studies and comparisons were used to analyse subjects' Web-based searching and learning achievement, online searching strategies and the role of Internet self-efficacy. The results showed evidence that high Internet self-efficacy students had better information searching strategies and learned better than those with low Internet self-efficacy in a Web-based learning task. This study further proposed a framework for analysing Web-based searching strategies. This study also reflected the importance of explicitly helping students acquire better metacognitive Web searching strategies.