Browsing by Author "Lee, YC"

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A novel bi-directional amplifier with applications in active Van Atta retrodirective arrays
(2003-02-01)
Chung, SJ
;
Chen, SM
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Lee, YC
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電信工程研究所
;
Institute of Communications Engineering
A novel two-port bi-directional amplifier, which may simultaneously amplify the waves coming from both ports, is proposed and demonstrated in this paper. Using this amplifier, a two-element active Van Atta retrodirective array is implemented and compared to a four-element passive array. The bi-directional amplifier is constructed by two identical one-port reflection-type amplifiers and a 3-dB 90degrees hybrid. The reflection-type amplifier is designed using an FET with a single-power-supply configuration. A quarter-wavelength microstrip radial stub is connected to the device's source terminal to narrow down the negative-resistance frequency range so as to avoid oscillation at undesired frequencies. The fabricated bi-directional amplifier provides the transmission gain over the frequency band from 5.76 to 6.88 GHz, with a peak value of 9.1 dB at 6.04 GHz. Printed Yagi antennas with four directors are adopted to build both the active and passive Van Atta arrays. The 3-dB back-scattering beamwidth of the active array is measured as wide as 74degrees. Finally, it is observed from the measurements that, although only half of the antenna elements are used, the active Van Atta array produces a back-scattering field level 4.5 dB,, on average, higher than the passive one does. This verifies the performance of the bi-directional amplifier.
A pseudo-2D adaptive decision feedback equalizer for high density magnetic recording system
(1995)
Lee, YC
;
Wei, CH
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Comprehensive investigation on fluorosilicate glass prepared by temperature-difference-based liquid-phase deposition
(2000-01-01)
Yeh, CF
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Lee, YC
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Wu, KH
;
Su, YC
;
Lee, SC
This study investigates the properties of fluorosilicate glass film prepared by temperature-difference-based liquid-phase deposition. Experimental results indicate that the deposition temperature can significantly affect the deposition rate and film properties. As the deposition temperature increases from 15 to 35 degrees C, the deposition rate increases exponentially from 30 to 687 Angstrom/h. Meanwhile, the F and OH contents increase from 2.56 to 3.49% and from 0.16 to 0.5%, respectively. The dielectric constants;ind stresses for the films deposited at 15, 25, and 35 degrees C, are 3.56/63 MPa, 3.46/43 MPa, and 3.66/73 MPa, respectively. The current densities at 2 MV/cm for the films deposited at 15, 25, and 35 degrees C are 6.9 x 10(-9), 4.6 x 10(-9), and 3.6 x 10(-7) A/cm(2), respectively. For the film deposited at 25 degrees C. the dielectric constant and the stress are minimal because of the high F content, low OH content, and low bond strain. The properties are also compared with those of fluorosilicate glass prepared by plasma-enhanced chemical vapor deposition. In addition to exhibiting a lower dielectric constant and much better resistance to moisture, the film prepared by temperature-difference-based liquid-phase deposition also shows a comparable or better insulating property, revealing a reliable intermetal dielectric with a low dielectric constant. (C) 2000 The Electrochemical Society. S0013-4651(99)04-019-7. All rights reserved.
Dark current and trailing-edge suppression in ultrafast photoconductive switches and terahertz spiral antennas fabricated on multienergy arsenic-ion-implanted GaAs
(2005-07-01)
Liu, TA
;
Lin, GR
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Lee, YC
;
Wang, SC
;
Tani, M
We report ultrafast (similar to 2.7 ps, instrument limited) switching responses of a multienergy- implanted GaAs:As' photoconductive switches (PCSs) with suppressed trailing edge and reduced dark. current. This material is highly resistive with dark current as low as 0.94 mu A at a bias of 40 V. The carrier mobility of the former is similar to 590 cm(2)/V s, resulting in a small-signal optical responsivity of similar to 2 mA/W. Pumped at 100 mW and biased at 80 V, the multienergy-implanted GaAs: As+ PCS exhibits peak response (0.35 V) comparable to the best result of single-energy-implanted ones. The improvement on photoconductive response is crucial for the generation of shorter terahertz emission pulses from spiral antennas fabricated on multienergy-implanted GaAs:As+ (0.8 ps) than single-energy-implanted GaAs (1.2 ps), with the central frequency blueshifted to 0.2 THz (from 0.15 THz) and the spectral bandwidth broadened to 0.18 THz (from 0.11 THz). (c) 2005 American Institute of Physics.
Dissociation of energy-selected c-C2H4S+ in a region 10.6-11.8 eV: Threshold photoelectron-photoion coincidence experiments and quantum-chemical calculations
(2005-08-01)
Fang, YS
;
Lin, IF
;
Lee, YC
;
Chiang, SY
;
應用化學系
Dissociation of energy-selected c-C2H4S+ was investigated in a region of 10.6-11.8 eV with a threshold photoelectron-photoion coincidence technique and a synchrotron as a source of vacuum ultraviolet radiation. Branching ratios and average releases of kinetic energy in channels of formation of c-C2H4S+, CH3CS+, and HCS+ were obtained from well-resolved time-of-flight peaks in coincidence mass spectra. Measured average releases of kinetic energy for channel CH3CS++H of least energy are substantial and much greater than calculated with quasiequilibrium theory; in contrast, small releases of kinetic energy near the appearance onset for channel HCS++CH3 agree satisfactorily with statistical calculations. Calculations of molecular electronic structures and energetics of c-C2H4S+ and C2H3S+ isomers and various fragments and transition states were also performed with Gaussian 3 method to establish dissociation mechanisms. A predicted dissociation energy of 11.05 eV for c-C2H4S -> HCS++CH3 agrees with a linearly extrapolated threshold at 10.99 +/- 0.04 eV and a predicted dissociation mechanism that c-C2H4S+ isomerizes to CH3CHS+ before dissociating to HCS++CH3 supports the experimental results. The large releases of kinetic energy for channel CH3CS++H might result from a dissociation mechanism according to which c-C2H4S+ isomerizes to a local minimum CH3CSH+ and then dissociates through a transition state to form CH3CS++H. (C) 2005 American Institute of Physics.
Edge-preserving texture filtering for real-time rendering
(2003-03-01)
Lee, YC
;
Jen, CW
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電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Texture filtering is essential in enhancing the visual quality of real-time rendering. Conventional schemes do not consider the characteristics of texture content, thus the sharpness of edges in texture images cannot be retained. This paper proposes a novel texture-filtering algorithm, which consists of edge-preserving interpolation and edge-preserving MIP-map prefiltering. The memory bandwidth requirement is kept the same as in conventional schemes by dynamically adjusting the interpolation kernel. Hardware implementation is also provided to show the real-time processing capability.
Improved quadratic normal vector interpolation for realistic shading
(2001)
Lee, YC
;
Jen, CW
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電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Interpolation for normal vectors is an important stage of Phong shading. Linear interpolation cannot represent the geometry of surfaces adequately in some situations. Previous quadratic interpolation for normal vectors generates visual artifacts for arch-type curves and triangle scan conversion. To eliminate those artifacts, we propose an improved quadratic interpolation for normal vectors with little computational overhead. Perspective-correct version for obtaining perspective foreshortening is also presented.
Index rendering: Hardware-efficient architecture for 3-D graphics in multimedia system
(2002-09-01)
Liang, BS
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Lee, YC
;
Yeh, WC
;
Jen, CW
;
電子工程學系及電子研究所
Real-time three-dimensional (3-D) graphics emerges rapidly in multimedia applications, but it suffers from requirements for huge computation, high bandwidth, and large buffer. In order to achieve hardware efficiency for 3-D graphics rendering, we propose a novel approach named index rendering. The basic concept of index rendering is to realize 3-D rendering pipeline by using asynchronous multi-dataflows. Because triangle information can be divided into several parts with each part capable of being transferred independently and asynchronously. At last, all data are converged by the index to generate the final image. Index rendering approach can eliminate unnecessary operations in traditional 3-D graphics pipeline. The unnecessary operations are caused by the invisible pixels and triangles in the 3-D scene. Previous work, deferred shading, eliminates the operations relating to invisible pixels, but it requires huge tradeoffs in bandwidth and buffer size. With index rendering, we can eliminate operations on both invisible pixels and triangles with less tradeoffs as compared with deferred shading approach. The simulation and analysis results show that the index rendering approach can reduce 10%-70% of lighting operations when using flat and Gouraud shading process and decrease 30%-95% when using Phong shading. Furthermore, it saves 70% of buffer size and 50%-70% of bandwidth compared with deferred shading approach. The result also indicates that this approach of index rendering is especially suitable for low-cost portable rendering device. Hence, index rendering is a hardware-efficient architecture for 3-D graphics, and it makes rendering hardware easier to be integrated into multimedia system, especially in system-on-a-chip (SOC) design.
Luminescence of selective area growth of epitaxial ZnO nanowires and random-growth-oriented nanobelts
(2006-03-14)
Hsu, HC
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Cheng, HM
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Wu, CY
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Huang, HS
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Lee, YC
Epitaxial ZnO nanowires and random-growth-oriented nanobelts were grown on c-plane sapphire with and without a pre-coated ZnO epilayer film. On the pre-coated ZnO epilayer, ZnO nanowires are vertically aligned with good in-plane alignment as a result of homoepitaxy, whereas on the bare c-plane sapphire, besides a few nanowires vertically aligned with [0001]znO parallel to [0001](Al2O3), the nanowires were properly aligned with three-fold rotation symmetry. The ZnO nanowires are well-defined hexagonal crystals with diameters of 70-500 nm and lengths of up to several micrometres. In the junction regions between the pre-coated epilayer and the bare sapphire surface, however, ZnO nanobelts (nanoribbons) were found. Cathodoluminescence measurements revealed that the emission at 3.26 eV is correlated with free-exciton recombination and the broad green emission at 2.48 eV is attributed to surface defects. The stronger green emission implies that more surface defects exist on the side walls of nanowires and nanobelts. In Raman scattering, the E1 (LO) mode is sensitive to the orientation of nanostructure that is consistent with the cathodoluminescence results.
Newly developed low-K and low-stress fluorinated silicon oxide utilizing temperature-difference liquid-phase deposition technology
(1998)
Yeh, CF
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Lee, YC
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Lee, SC
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電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
To meet the requirements of low-K and low-stress intermetal dielectric (IMD) for future ULSI devices, a novel temperature-difference liquid-phase deposition (TD-LPD) method is proposed. The deposition solution of supersaturated silicic acid with high concentration of fluorine can be achieved by raising deposition temperature larger than 15 degrees C from dissolution temperature (0 degrees C). Because fluorine atoms can easily be incorporated with the technique, TD-LPD fluorine-doped SiO2 (FSG) exhibits low-K (similar to 3.4) and low-stress (similar to 40MPa) property. In this paper, to study the interaction between TD-LPD FSG and moisture, the FSG is annealed and moisture stressed repeatedly as in a real process. Since K is sensitive to moisture absorption, and the stress is sensitive to the dehydration reaction between Si-OH's, the both are monitored as indices. A feasible mechanism is proposed to explain the variation in K/stress during annealing and boiling cycles.
Novel barrier dielectric liner prepared by liquid-phase deposition and NH3-plasma annealing
(2000-12-01)
Yeh, CF
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Lee, YC
;
Chen, CM
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Wu, KH
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電子工程學系及電子研究所
A novel barrier dielectric liner prepared by liquid-phase deposition and post-deposition NH3-plasma annealing is proposed as a capping layer to be used on damascene trenches of low-permittivity dielectric. The liner technology meets the essential requirements such as (1) thin and conformal deposition, (2) a low leakage current level, and (3) effective blocking of Cu penetration. With this barrier dielectric liner, Cu damascene interconnection is expected to have a low leakage current and high resistance to Cu penetration into the low-permittivity dielectrics even if the barrier metal fails locally.
Novel sidewall capping for degradation-free damascene trenches of low-permittivity methylsilsesquioxane
(2000-04-15)
Yeh, CF
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Lee, YC
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Su, YC
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Wu, KH
;
Lin, CH
A low-permittivity organic dielectric, methylsilsesquioxane (MSQ), used as an interlevel dielectric is expected to reduce the parasitic capacitance in integrated circuit. However, MSQ film can he easily degraded during resist ashing after the film is etched with the damascene trenches being created. In this work, a novel sidewall capping technology is developed to solve the degradation issue. Prior to resist ashing, a high-quality, low-permittivity oxide him is selectively deposited onto the sidewalls of MSQ trenches using selective liquid-phase deposition. Experimental results demonstrate that the capping oxide can effectively protect the sidewalls of MSQ trenches from ashing-induced degradation.
O-2-plasma degradation of low-k organic dielectric and its effective solution for damascene trenches
(2000)
Yeh, CF
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Lee, YC
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Su, YC
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Wu, KH
;
Lin, CH
Methylsilsesquioxane, an organic spin-on dielectric, has attracted much attention as a promising low-k inter-Cu-metal dielectric because of its sufficiently low dielectric constant (<2.8) and excellent thermal stability (>500 degreesC). However, we found that MSQ film would be easily degraded during resist ashing in O-2-plasma ambient after the film is etched with the damascene trenches being created. An innovative sidewall capping technology as an effective solution of this ashing-induced degradation has been successfully developed. This new technology has potential to fulfill the highly reliable damascene process toward Cu/MSQ integration.
Optical studies of the Holmium-doped InGaAsP epilayers
(2003-12-01)
Lee, YC
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Shu, GW
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Cheng, IM
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Chen, CP
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Shen, JL
Photoluminescence (PL), contactless electroreflectance (CER), and Raman scattering measurements have been used to study the structural properties of Ho-doped InGaAsP epilayers. Both the full width at half maximum (FWHM) of PL and the broadening parameter of CER are decreased as the doping amount of Ho element increases. This indicates that Ho doping greatly reduces the residual impurities and improve the quality of epilayers. The Raman spectra of Ho-doped InGaAsP epilayers are found to have asymmetric line shapes. Using a spatial correlation model, it is found the asymmetric broadening of the Raman signal is not influenced by the Ho doping. We hence conclude that the introduction of the Ho element can greatly reduce the residual impurities of LPE-grown layers, but no large amounts of Ho element are being incorporated into the epilayers during the purification. (C) 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Recombination dynamics of luminescence in colloidal CdSe/ZrS quantum dots
(2005-09-01)
Lee, WZ
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Shu, GW
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Wang, JS
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Shen, JL
;
Lin, CA
Recombination dynamics of photoluminescence (PL) in colloidal CdSe/ZnS quantum dots (QDs) were studied using time-resolved PL measurements. The PL intensity shows a biexponential decay at 9 K, consisting of a fast component (similar to 1 ns) and a slow component (similar to 6.3 ns). Based on the emission-energy and temperature dependence of carrier lifetimes, we suggest that the fast and slow PL decay of colloidal CdSe/ZnS QDs originates from recombination of the delocalized carriers in the internal core states and the localized carriers at the interface, respectively.
Reliability of fluorinated silicon oxide film prepared by temperature difference-based liquid phase deposition
(2000-11-01)
Yeh, CF
;
Lee, YC
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Lee, SC
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電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Fluorinated silicon oxide film prepared by using temperature difference-based liquid phase deposition is very potential for use as an intermetal dielectric owing to its high fluorine concentration (8.6 atom %), low dielectric constant (3.46), low stress (41 MPa) low leakage current density (4.6 X 10(-9) A/cm(2) at 2 MV/cm), and low deposition temperature (room temperature). In this work, we closely examine reliability issues including resistance to water absorption and thermal stability by adopting the repeatedly annealing (400 degreesC) and boiling test. After the test, the net increase in the dielectric constant is only 0.02; the stress changes within -24 to 41 MPa with a resultant zero stress; the leakage current density increases slightly to 8.0 X 10(-9) A/cm(2). Obviously the film will preserve its attractive properties in a back-end process similar to the test. Accompanied with the investigation of p-etch rate, thermal desorption spectroscopy, and Fourier transform infrared spectroscopy, a feasible mechanism that accounts for the variation of the properties during the test is proposed. A high temperature (>400 degreesC) annealing effect is also studied. The film is thermally stable up to 600 degreesC, which is limited by the decomposition of Si-F bonds. The thermal stability of 600 degreesC is obviously sufficient for intermetal dielectric application. (C) 2000 The Electrochemical Society. S0013-4651(99)12-019-6. All rights reserved.
Satellite sensor image classification using cascaded architecture of neural fuzzy network
(2000-03-01)
Lin, CT
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Lee, YC
;
Pu, HC
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電控工程研究所
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Institute of Electrical and Control Engineering
Satellite sensor images usually contain many complex factors and mixed pixels, so a high classification accuracy is not easy to attain. Especially, for a nonhomogeneous region, gray values of satellite sensor images vary greatly and thus, direct statistic gray values fail to do the categorization task correctly. The goal of this paper is to develop a cascaded architecture of neural fuzzy networks with feature mapping (CNFM) to help the clustering of satellite sensor images, In the CNFM, a Kohonen's self-organizing feature map (SOFM) is used as a preprocessing layer for the reduction of feature domain, which combines original multi-spectral gray values, structural measurements from co-occurrence matrices, and spectrum features from wavelet decomposition. In addition to the benefit of dimensional reduction of feature space, Kohonen's SOFM can remove some noisy areas and prevent the following training process from being overoriented to the training patterns, The condensed measurements are then forwarded into a neural fuzzy network, which performs supervised learning for pattern classification. The proposed cascaded approach is an appropriate technique for handling the classification problem in areas that exhibit large spatial variation and interclass heterogeneity (e.g., urban-rural infringing areas). The CNFM is a general and useful structure that can give us favorable results in terms of classification accuracy and learning speed, Experimental results indicate that our structure can retain high accuracy of classification (90% in average), while the training time is substantially reduced if our system is compared to the commonly used backpropagation network. The CNFM appears to be more reasonable and practical than the conventional implementation.
Selective SiO2-xFx growth with liquid-phase deposition for MEMS technology
(1996)
Yeh, CF
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Lee, YC
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Su, JL
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電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
Smart dielectrics of fluorinated silicon glass prepared by liquid phase deposition method
(2001)
Yeh, CF
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Chen, TF
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Lee, YC
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Liu, CH
;
Lin, SS
Fluorinated silicon glass (FSG) film prepared by using liquid-phase deposition (LPD) is very potential for use as a smart dielectric owing to its high fluorine concentration (8.6 at %), low dielectric constant (3.46), low stress (43 Mpa), low leakage current density (4.6E-9 A/cm(2) at 2 MV/cm) and low deposition temperature (room temperature). By temperature difference and conventional water-adding methods, the LPD technologies and the key process parameters affecting the physicochemical properties and the electrical characteristics will be introduced. Furthermore, the LPD FSG has been applied as gate oxide to MOSFET's and polysilicon TFT's. Owing to its novel property of selective deposition, LPD FSG has been also employed to cap the sidewalls for degradation-free damascene trenches, and to fabricate micro contact holes for the n(+)/p diodes and the Schottky diodes.
The substrate effect on the in-plane orientation of vertically well-aligned ZnO nanorods grown on ZnO buffer layers
(2005-12-01)
Cheng, HM
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Hsu, HC
;
Yang, S
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Wu, CY
;
Lee, YC
Vertically well-aligned ZnO nanorods were synthesized without employing any metal catalysts on various substrates including glass, Si(111), 6H-SiC(0001) and sapphire (0001), which were pre-coated with c-oriented ZnO buffer layers, by simple physical vapour deposition. The alignments of the ZnO nanorods on the different substrates depend on the crystallographic alignments of the pre-coated ZnO buffer layers. The ZnO nanorods grown on glass and Si(111) are vertically aligned but randomly oriented in the in-plane direction. In contrast, the vertically aligned ZnO nanorods on 6H-SiC(0001) and sapphire (0001) show an in-plane alignment with azimuthally sixfold symmetry, which indicates the epitaxial relationship between ZnO and the substrate. Similarly, photoluminescence measurements show the distinct appearance of ZnO nanorods on different substrates. Besides the UV band, which was attributed to the recombination of free excitons near the band edge, defect-related visible emissions were also observed for the samples grown on both glass and Si(111) substrates. However, the ZnO nanorods exhibit only strong band edge emission peaks with no noticeable deep level emissions when grown on the 6H-SiC(0001) and sapphire (0001) substrates, which confirms the good crystalline and optical quality of the epitaxial ZnO nanorods.