Browsing by Issue Date, starting with "2003-01-30"

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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
;
光電工程學系
;
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
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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.
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Liao, C. T.
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電子物理學系
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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.
Low-temperature synthesis multiwalled carbon nanotubes by microwave plasma chemical vapor deposition using CH4-CO2 gas mixture
(2003-02-01)
Chen, M
;
Chen, CM
;
Shi, SC
;
Chen, CF
;
材料科學與工程學系
Vertically aligned carbon nanotubes (CNTs) with multiwalled structures were successfully grown on a Fe-deposited Si substrate at low temperatures below 300 degreesC by microwave plasma chemical vapor deposition using of a CH4-CO2 gas mixture. The low temperature would be beneficial for reducing the diameter of CNTs but it will also decrease the growth rate on the substrate. The low-temperature growth of CNTs was achieved by decreasing both the microwave power and the total gas pressure. The constituents of the gas mixture are also key factors in chemical vapor deposition. After deposition, the microstructure morphology of CNTs was observed by using scanning electron microscope and high-resolution transmission microscope. The results showed that even at low temperature a high yield of carbon nanotubes with a high emission current density and a small diameter is obtained. Vertically aligned multiwalled CNTs with a diameter about 12 nm were investigated by scanning electron microscope (SEM) and high-resolution transmission electron microscope (HRTEM).
High-performance P-channel Schottky-barrier SOI FinFET featuring self-aligned PtSi source/drain and electrical junctions
(2003-02-01)
Lin, HC
;
Wang, MF
;
Hou, FJ
;
Lin, HN
;
Lu, CY
A simplified and improved Schottky-barrier metal-oxide-semiconductor device featuring a self-aligned offset channel length, PtSi Schottky junction, and reduced oxide thickness underneath the sub-gate was proposed and demonstrated. To alleviate the drawbacks related to the nonself-aligned offset channel length in the original version, a self-aligned offset channel length is achieved in, the new device by forming the silicide source/drain junction self-aligning to the sidewall spacers abutting the gate. This results in not only one mask count saving but also better device performance, as facilitated by, the reduced offset channel length of the self-aligned sidewall spacers. Moreover, the adoption of PtSi for the Schottky junction further improves the on-state current of p-channel operation, while a thinner oxide employed underneath the sub-gate effectively reduces the sub-gate bias needed to form the electrical junction to below 5 V. Significant improvement in on-current as well as leakage current reduction is achieved in the new improved device.
A novel fiber-laser-based sensor network with self-healing function
(2003-02-01)
Peng, PC
;
Tseng, HY
;
Chi, S
;
光電工程學系
;
Department of Photonics
In this letter, we, present a novel fiber-laser-based sensor network. with self-healing. function and demonstrate its effectiveness. The network survivability and capacity for a multipoint sensor system ate enhanced by adding switches in a self-healing ring architecture. The fiber laser adopted in this system is a linear-cavity filter Bragg grating (FBG) laser leading to the signal-to-noise ratio. over 52 dB for the sensor network. The network survivability of a ten-point FBG sensor is experimentally examined. The experimental results show that the proposed system can facilitate reliable, sensing network for a large-scale and multipoint smart structure.
A neural network approach for structural identification and diagnosis of a building from seismic response data
(2003-02-01)
Huang, CS
;
Hung, SL
;
Wen, CM
;
Tu, TT
;
土木工程學系
This work presents a novel procedure for identifying the dynamic characteristics of a building and diagnosing whether the building has been damaged by earthquakes, using a back-propagation neural network approach. The dynamic characteristics are directly evaluated from the freighting matrices of the neural network trained by observed acceleration responses and input base excitations. Whether the building is damaged under a large earthquake is assessed by comparing the modal parameters and responses for this large earthquake with those for a small earthquake that has not Caused this building any damage. The feasibility of the approach is demonstrated through processing the dynamic responses of a five-storey steel frame. subjected to different strengths of the Kobe earthquake, in shaking table tests. Copyright (C) 2002 John Wiley Sons, Ltd.
Error-resilient image coding (ERIC) with smart-IDCT error concealment technique for wireless multimedia transmission
(2003-02-01)
Lee, YS
;
Ong, KK
;
Lee, CY
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
The fields of multimedia and wireless communications have grown rapidly in recent years, leading to a great demand for an image-coding scheme that has both compression and error-resilient capabilities. Because bandwidth is a valuable and limited resource, the compression technique is applied to wireless multimedia communication. However, strong data dependency will be created while the bit-rate reduction is achieved. Transmission errors always results in significant quality degradation. In this paper, an error-resilient image coding for discrete-cosine-transform-based image compression is proposed. It can successfully prevent errors from propagating across image block boundaries with little overhead. Additionally, a. novel Post-processing error concealment. scheme is presented to retain low-frequency information and discard suspicious high-frequency information. Low-resolution information, rather than total corruption, can be obtained during the image-decoding process. Because of low complexity and latency properties, it is very suitable for wireless mobile applications. Simulation results show that good image quality (PSNR = 31.78dB) and a low fraction of corruptive blocks (less than 5%) can be achieved even when the bit error rate is 0.1%.