Browsing by Issue Date, starting with "2010-08-19"

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Suppression of Octahedral Tilts and Associated Changes in Electronic Properties at Epitaxial Oxide Heterostructure Interfaces
(2010-08-19)
Borisevich, A. Y.
;
Chang, H. J.
;
Huijben, M.
;
Oxley, M. P.
;
Okamoto, S.
Epitaxial oxide interfaces with broken translational symmetry have emerged as a central paradigm behind the novel behaviors of oxide superlattices. Here, we use scanning transmission electron microscopy to demonstrate a direct, quantitative unit-cell-by-unit-cell mapping of lattice parameters and oxygen octahedral rotations across the BiFeO(3)-La(0.7)Sr(0.3)MnO(3) interface to elucidate how the change of crystal symmetry is accommodated. Combined with low-loss electron energy loss spectroscopy imaging, we demonstrate a mesoscopic antiferrodistortive phase transition near the interface in BiFeO(3) and elucidate associated changes in electronic properties in a thin layer directly adjacent to the interface.
Self-assembly of an A-B diblock copolymer blended with a C homopolymer and a C-D diblock copolymer through hydrogen bonding interaction
(2010-08-19)
Chen, Wan-Chun
;
Kuo, Shiao-Wei
;
Chang, Feng-Chih
;
應用化學系
;
Department of Applied Chemistry
In this study, we investigated the miscibility, phase behavior, and self-assembled nanostructures formed from the immiscible crystalline-amorphous diblock copolymer poly(epsilon-caprolactone-b-4-vinyl pyridine) (PCL-b-P4VP, A-B) when blended with the homopolymer poly(vinyl phenol) (PVPh, C) and the diblock copolymer poly(vinyl phenol-b-styrene) (PVPh-b-PS, C-D). Long-range-ordered microphase separation was difficult to achieve in the PCL-b-P4VP/PVPh (A-B/C) blend system because PVPh interacted with both the P4VP and PCL blocks simultaneously through hydrogen bonding interactions. In contrast, we observed sharp, multiple orders of diffraction in the SAXS profiles of the PCL-b-P4VP/PVPh-b-PS (A-B/C D) blend system, indicating that perfect microphase separation occurred because the incorporation of the PS block induced the PVPh block to hydrogen bond preferentially with the P4VP block. This simple A-B/C-D (PCL-b-P4VP/PVPh-b-PS) diblock copolymer mixture exhibited self-assembly behavior (a three-lamella phase) similar to that of a corresponding ABC triblock copolymer. (C) 2010 Elsevier Ltd. All rights reserved.
Effects of sputtering pressure and Al buffer layer thickness on properties of AZO films grown by rf magnetron sputtering
(2010-08-20)
Tseng, C. H.
;
Wang, W. H.
;
Chang, H. C.
;
Chou, C. P.
;
Hsu, C. Y.
Transparent and conductive Al-doped (2 wt.%) zinc oxide (AZO) films were deposited on inexpensive soda-lime glass substrates by using rf magnetron sputtering at room temperature. This study analyzed the effects of argon sputtering pressure, which varied in the range from 0.46 to 2.0 Pa, on the morphological, electrical and optical properties of AZO films. The only (0 0 2) diffraction peak of the film were observed at 20 similar to 34.45 degrees, exhibiting that the AZO films had hexagonal ZnO wurtzite structure, and a preferred orientation with the c-axis perpendicular to the substrate. By applying a very thin aluminum buffer layer with the thickness of 2 nm, findings show that the electrical resistivity was 9.46 x 10(-4) Omega-cm, and the average optical transmittance in the visible part of the spectra was approximately 81%. Furthermore, as for 10 nm thick buffer layer, the electrical resistivity was lower, but the transmittance was decreased. (C) 2010 Elsevier Ltd. All rights reserved.
資料搜尋方法及其數值資料編碼方法
(2010-08-21)
鄭哲聖
;
單智君
;
鍾崇斌
本發明係揭露一種資料搜尋方法及其數值資料編碼方法，此方法將已排序之複數個數值分成複數個群組，每一群組之第一個數值係代表為跳躍點，而其他數值係代表為內部點，接著，使用一第一編碼演譯程序對該些群組之跳躍點進行編碼，以產生複數個跳躍點編碼值，並使用一空間預估程序，預估此些內部點以一第二編碼演譯程序進行編碼時所需之位元保留空間，繼之，根據該第二編碼演譯程序對該些群組之該些內部點進行編碼，以產生複數個內部點編碼值。最後，根據群組之排列順序及位元保留空間，將跳躍點編碼值及內部點編碼值依序排列，以產生一輸出編碼資料。
消除正交分頻多工系統中因通道時變產生載波間干擾的方法
(2010-08-21)
吳文榕
;
許兆元
正交分頻多工(OFDM)系統於高速移動的環境下，通道在一OFDM符元(symbol)內具有時變特性，此時變特性會造成載波間正交性喪失而互相干擾，降低系統效能，因此本發明即在提供一種消除正交分頻多工系統中因通道時變產生載波間干擾的方法，其係利用線性時變通道之干擾矩陣本身的特殊結構，配合牛頓疊代(iteration)法化簡反矩陣運算，並使用快速傅立葉轉換降低運算量，不需使用額外電路即可達到消除載波間干擾之目的。
Solid-phase thermodynamic interpretation of ion desorption in matrix-assisted laser desorption/ionization
(2010-08-22)
Lai, Yin Hung
;
Wang, Chia Chen
;
Lin, Sheng Hsian
;
Wang, Yi Sheng
;
Lee, Yuan Tseh
交大e-News第077期
(2010-08-23)
Secretariat
;
國立交通大學秘書室
High-gain complementary inverter with InGaZnO/pentacene hybrid ambipolar thin film transistors
(2010-08-23)
Liu, Po-Tsun
;
Chou, Yi-Teh
;
Teng, Li-Feng
;
Fuh, Chur-Shyang
;
光電工程學系
Ambipolar thin film transistors (TFTs) with InGaZnO/pentacene heterostructure channels are demonstrated for a high-voltage-gain complementary metal oxide semiconductor (CMOS) inverter. The ambipolar TFT exhibits a electron mobility of 23.8 cm(2)/V s and hole mobility of 0.15 cm(2)/V s for the InGaZnO and pentacene, respectively. The thermal annealing process was also studied to adjust electron concentration reducing operating voltage of the CMOS inverter. The voltage gain achieves as high as 60 obtained in the first and third quadrants of the voltage transfer characteristic. The high performance and simple manufacture of the heterostructure CMOS inverter show promise as critical components in various electrical applications. (C) 2010 American Institute of Physics. [doi:10.1063/1.3483616]
2-D modeling of dual-mode acoustic phonon excitation of a triangular nanoplate
(2010-08-23)
Tai, Po-Tse
;
Yu, Pyng
;
Tang, Jau
;
光電工程學系
;
Department of Photonics
In this theoretical work, we investigated coherent phonon excitation of a triangular nanoplate based on 2-D Fermi-Pasta-Ulam lattice model. Based on the two-temperature model commonly used in description of laser heating of metals, we considered two kinds of forces related to electronic and lattice stresses. Based on extensive simulation and analysis, we identified two major planar phonon modes, namely, a standing wave mode related to the triangle bisector and another mode corresponding to half of the side length. This work elucidates the roles of laser-induced electronic stress and lattice stress in controlling the initial phase and the amplitude ratio between these two phonon modes. (C) 2010 Elsevier B.V. All rights reserved.
Formation, Binding, and Stability of O-Ag-CO(2)-Ag-O Compounds on Ag(100) Investigated by Low Temperature Scanning Tunneling Microscopy and Manipulation
(2010-08-26)
Hsieh, Ming-Feng
;
Li, Hong-Doa
;
Lin, Deng-Sung
;
Morgenstern, Karina
;
物理研究所
The understanding of reaction intermediates in heterogeneous catalysis has important implications for the design of novel catalysts. We investigate the adsorption of CO(2) on oxygen precovered Ag(100) at low temperature (17 K) by scanning tunneling microscopy and inelastic electron tunneling manipulation at 5 K. On the terraces, the adsorption leads to O-Ag-CO(2)-Ag-O compounds with reduced binding of the oxygen to the surface as compared to the separately adsorbed molecules. The compound can be either dissociated into a bistable O-Ag-CO(2) compound at 1.6 V, dissociated into its constituents at 2.2 V, or reacted at 6.5 V into a species, which we tentatively attribute to CO(3). The thus obtained carbon trioxide or carbonate is an intriguing reaction intermediate, because it is not stable in the gas phase. Our detailed study of coadsorbed species outlines a possibility to investigate precursors of reactions that involve the substrate atoms.
Tunable Fano-Kondo resonance in side-coupled double quantum dot systems
(2010-08-26)
Chung, Chung-Hou
;
Lee, Tsung-Han
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電子物理學系
;
Department of Electrophysics
We study the interference between the Fano and Kondo effects in a side-coupled double quantum dot system where one of the quantum dots couples to conduction-electron bath while the other dot only side couples to the first dot via antiferromagnetic (AF) spin-exchange coupling. We apply both the perturbative renormalization-group (RG) and numerical renormalization-group (NRG) approaches to study the effect of AF coupling on the Fano line shape in the conduction leads. With particle-hole symmetry, the AF spin-exchange coupling competes with the Kondo effect and leads to a local spin-singlet ground state for arbitrary small coupling, so-called "two-stage Kondo effect." As a result, via NRG we find the spectral properties of the Fano line shape in the tunneling density of states rho(c)(omega) of conduction-electron leads shows double dip-peak features at the energy scale around the Kondo temperature and the one much below it, corresponding to the two-stage Kondo effect; it also shows an universal scaling behavior at very low energies. We find the qualitative agreement between the NRG and the perturbative RG approaches. Relevance of our work to the experiments is discussed.
Coherent multiple-stage optical rectification terahertz wave generator
(2010-08-26)
Pan, Ci-Ling
;
Huang, Jung Y.
;
Chang, Chen-Shiung
;
Chen, Ching-Wei
;
Lin, Yu-Shian
The present invention coherent multiple-stage optical rectification terahertz wave generator discloses the generation of single-cycle terahertz radiation with two-stage optical rectification in GaSe crystals. By adjusting the time delay between the pump pulses employed to excite the two stages, the terahertz radiation from the second GaSe crystal can constructively superpose with the seeding terahertz field from the first stage. The high mutual coherence between the two terahertz radiation fields is ensured with the coherent optical rectification process and can be further used to synthesize a desired spectral profile of output coherent THz radiation. The technique is also useful for generating high amplitude single-cycle terahertz pulses, not limited by the pulse walk-off effect from group velocity mismatch in the nonlinear optical crystal used.
Formation, Binding, and Stability of O-Ag-CO2-Ag-O Compounds on Ag(100) Investigated by Low Temperature Scanning Tunneling Microscopy and Manipulation
(2010-08-26)
Hsieh, Ming-Feng
;
Li, Hong-Doa
;
Lin, Deng-Sung
;
Morgenstern, Karina
;
物理研究所
The understanding of reaction intermediates in heterogeneous catalysis has important implications for the design of novel catalysts. We investigate the adsorption of CO2 on oxygen precovered Ag(100) at low temperature (17 K) by scanning tunneling microscopy and inelastic electron tunneling manipulation at 5 K. On the terraces, the adsorption leads to O-Ag-CO2-Ag-O compounds with reduced binding of the oxygen to the surface as compared to the separately adsorbed molecules. The compound can be either dissociated into a bistable O-Ag-CO2 compound at 1.6 V, dissociated into its constituents at 2.2 V, or reacted at 6.5 V into a species, which we tentatively attribute to CO3. The thus obtained carbon trioxide or carbonate is an intriguing reaction intermediate, because it is not stable in the gas phase. Our detailed study of coadsorbed species outlines a possibility to investigate precursors of reactions that involve the substrate atoms.
Wide spectral range confocal microscope based on endlessly single-mode fiber
(2010-08-30)
Hubbard, R.
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Ovchinnikov, Yu. B.
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Hayes, J.
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Richardson, D. J.
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Fu, Y. J.
We report an endlessly single mode, fiber-optic confocal microscope, based on a large mode area photonic crystal fiber. The microscope confines a very broad spectral range of excitation and emission wavelengths to a single spatial mode in the fiber. Single-mode operation over an optical octave is feasible. At a magnification of 10 and lambda = 900 nm, its resolution was measured to be 1.0 mu m (lateral) and 2.5 mu m (axial). The microscope's use is demonstrated by imaging single photons emitted by individual InAs quantum dots in a pillar microcavity. (C) 2010 Optical Society of America
A new low-voltage-driven GRIN liquid crystal lens with multiple ring electrodes in unequal widths
(2010-08-30)
Kao, Yung-Yuan
;
Chao, Paul C. -P.
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Hsueh, Chieh-Wen
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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
This work is dedicated to design a novel liquid crystal (LC) lens device with multiple ring electrodes in unequal widths, in order to offer tunability on focusing quality and to lower the level of applied voltage. The number and widths of the multiple ring electrodes are pre-designed and optimized to offer the on-line tunability on individual electrode voltages to render a better refraction index distribution for focusing, as compared to the past hole-type LC lenses. The resulted refractive index distribution is expected to offer similar focusing effects based on the theory of the gradient refraction index (GRIN) lens. The transparent electrodes of this new LC lens are placed at the inner surface of the LC cell to minimize the driving voltages, in results, less than 10V, for the same level of focusing power and an easy practical operation. A new fabrication process in the wafer level to bury bus lines is developed for generating smooth electrical fields over the lens aperture. In addition, a dielectric layer is coated between electrodes and the LC layer. (C) 2010 Optical Society of America
Nonequilibrium occupation number and charge susceptibility of a resonance level close to a dissipative quantum phase transition
(2010-08-30)
Chung, Chung-Hou
;
Latha, K. V. P.
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電子物理學系
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Department of Electrophysics
Based on the recent paper [Phys. Rev. Lett. 102, 216803 (2009)], we study the nonequilibrium occupation number n(d) and charge susceptibility chi of a resonance level close to dissipative quantum phase transition of the Kosterlitz-Thouless (KT) type between a delocalized phase for weak dissipation and a localized phase for strong dissipation. The resonance level is coupled to two spinless fermionic baths with a finite bias voltage and an Ohmic bosonic bath representing the dissipative environment. The system is equivalent to an effective anisotropic Kondo model out of equilibrium. Within the nonequilibrium renormalization-group approach, we calculate nonequilibrium magnetization M and spin susceptibility chi in the effective Kondo model, corresponding to 2n(d)-1 and chi of a resonance level, respectively. We demonstrate the smearing of the KT transition in the nonequilibrium magnetization M as a function of the effective anisotropic Kondo couplings, in contrast to a perfect jump in M at the transition in equilibrium. In the limit of large bias voltages, we find M and chi at the KT transition and in the localized phase show deviations from the equilibrium Curie-law behavior. As the system gets deeper in the localized phase, both n(d)-1/2 and chi decrease more rapidly to zero with increasing bias voltages.
Bimodel onset strain relaxation in InAs quantum dots with an InGaAs capping layer
(2010-08-30)
Chen, J. F.
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Chen, Ross C. C.
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Chiang, C. H.
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Chen, Y. F.
;
Wu, Y. H.
Capping InAs quantum dots (QDs) with an InGaAs layer allows strain relaxation to induce a low-energy electron state below a set of fine dot family states, which is consistent with photoluminescence (PL) spectra. The evolution of InAs thickness suggests a bimodal onset relaxation, i.e., a fine dot family that is strain-relieved by indium outdiffusion from the QDs, as suggested by transmission electron microscopy, and a low-energy dot family that is strain relaxed by the generation of lattice misfits. The indium outdiffusion can explain an abnormal PL blueshift in 70 meV in the fine dot family at onset of strain relaxation. (C) 2010 American Institute of Physics. [doi:10.1063/1.3483757]
Selective acoustic phonon mode excitation of multi-mode silver nanoprisms
(2010-08-30)
Tai, Po-Tse
;
Yu, Pyng
;
Huang, Jane
;
Tang, Jau
;
光電工程學系
Nanoprisms are known to exhibit two major planar phonon modes in ultrafast experiments, namely, a stronger mode related to the bisector height and a weaker mode related to half of the edge length. In this work we demonstrated photoacoustic excitation of a specific acoustic phonon mode in silver nanoprisms using two properly timed pump pulses. Using this technique, we could selectively excite only the weak totally symmetric mode while suppressing the dominant breathing mode. Via direct observation of such a mode, which is hardly detectable directly with the conventional single pump pulse technique, we could elucidate the roles of hot electrons in photoinduced ultrafast structural dynamics in laser-heated nanoparticles. (C) 2010 Elsevier B.V. All rights reserved.
Barrier-overpassing transporter
(2010-08-31)
Cheng
;
Pi-Ying
;
Guo
;
Fang-Fu
;
Wong
The present invention discloses a barrier-overpassing transporter, which comprises: a support frame carrying a rider or another load; a sensing/adjusting module detecting a tilting state of the support frame and maintaining the support frame in a horizontal state; a ground contact module arranged below the support frame supporting an effective load and lifting the support frame to overpass a surface of a barrier; and a wireless transceiver module collecting and transmitting information to enable adjustments and activities responding to interior states of the transporter. Thereby, the present invention can provide a safe, stable, reliable, comfortable, convenient and low-cost barrier-overpassing transporter.
Growth and photoresponse study of PdO nanoflakes reactive-sputter deposited on SiO2
(2010-09-01)
Huang, Chien-Jung
;
Pan, Fu-Ming
;
Chen, Hsiu-Ying
;
Li-Chang
;
材料科學與工程學系
This study prepares PdO nanostructures on a SiO2 substrate by reactive-sputter deposition and examines photoresponse characteristics of the thin films. PdO thin films deposited at 25 degrees C is composed of bowed nanoflakes standing on the SiO2 substrate, which have a single-crystalline structure after thermal anneal at 400 degrees C. The 400 degrees C-annealed nanoflake thin film has a band gap energy in the red-light range (similar to 2.06 eV), and exhibits a very sensitive photoresponse upon the UV (365 nm) illumination. The high photoresponse sensitivity of the 400 degrees C-annealed nanoflake thin film is ascribed to a lower density of recombination centers and traps due to an excellent crystallinity and a high carrier extraction efficiency due to a low electrical resistivity. A slight decrease in the photocurrent density during the initial stage of the UV illumination is attributed to adsorption of O-2(-) anions on the 400 degrees C-annealed nanoflakes. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3476567]