Browsing by Issue Date, starting with "2010-11-15"

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Long electron dephasing length and disorder-induced spin-orbit coupling in indium tin oxide nanowires
(2010-11-15)
Hsu, Yao-Wen
;
Chiu, Shao-Pin
;
Lien, An-Shao
;
Lin, Juhn-Jong
;
電子物理學系
We have measured the quantum-interference magnetoresistances in two single indium tin oxide (ITO) nanowires between 0.25 and 40 K, by using the four-probe configuration method. The magnetoresistances are compared with the one-dimensional weak-(anti)localization theory to extract the electron dephasing length L-phi. We found, in a 60-nm-diameter nanowire with a low resistivity of rho(10 K) =185 mu Omega cm, that L-phi is long, increasing from 150 nm at 40 K to 520 nm at 0.25 K. Therefore, the nanowire reveals strict one-dimensional weak-localization effect up to several tens of degrees of kelvin. In a second 72-nm-diameter nanowire with a high resistivity of rho(10 K)=1030 mu Omega cm, the dephasing length is suppressed to L-phi(0.26 K)=200 nm, and thus a crossover of the effective device dimensionality from one to three occurs at about 12 K. In particular, disorder-induced spin-orbit coupling is evident in the latter sample, manifesting weak-antilocalization effect at temperatures below similar to 4 K. These observations demonstrate that versatile quantum-interference effects can be realized in ITO nanowires by controlling differing levels of atomic defects and impurities.
On investigation of high T-c superconductors with Electron Paramagnetic Resonance spectrometers
(2010-11-15)
Shaltiel, D.
;
von Nidda, H. -A. Krug
;
Shapiro, B. Ya.
;
Bogoslavsky, B.
;
Rosenstein, B.
Following the discovery of high T-c superconductors, many researchers have applied EPR spectrometers to investigate their properties using the regular instructions to operate the spectrometer. As no substantial information was obtained it was soon practically abandoned. Investigations performed recently with the EPR technique, using a different operating method than the conventional one and the introduction of a detailed theoretical study related to the interaction of the JV with the microwave magnetic field lead to new and important results related to properties of high anisotropy superconductors indicating that the EPR spectrometer can be used to investigate properties of high anisotropy superconductors. The failures when using conventional operating method to obtain meaningful results and the method used in the present work to carry out the measurements in a proper manner are presented. Some important results obtained in investigating high anisotropy superconductors by the EPR technique are presented. (C) 2010 Elsevier B.V. All rights reserved.
Mini-slot scheduling for IEEE 802.16d chain and grid mesh networks
(2010-11-15)
Liang, Jia-Ming
;
Wu, Ho-Cheng
;
Chen, Jen-Jee
;
Tseng, Yu-Chee
;
資訊工程學系
This work considers the mini-slot scheduling problem in IEEE 802.16d wireless mesh networks (WMNs) An efficient mini-slot scheduling needs to take into account the transmission overhead, the scheduling complexity, and the signaling overhead to broadcast the scheduling results We are interested in chain and grid WMNs, which are the basic topologies of many applications We propose scheduling schemes that are featured by low complexity and low signaling overhead. Compared to existing works, this work contributes in developing low-cost schemes to find periodical and regular schedules that achieve near-optimal transmission latencies by balancing between transmission overhead and pipeline efficiency and that are more practical and easier to implement To minimize the transmission latency, we model the transmission latency as a function of the transmission size and the subscriber stations' traffic demands, and take the first-order derivative of the transmission size to find the minimum latency Simulation results show that our schemes significantly improve over existing works in computational complexity while maintain similar or better transmission latencies (C) 2010 Elsevier B.V All rights reserved.
Boundary influence on the entropy of a Lozi-type map
(2010-11-15)
Juang, Jonq
;
Chang, Yu-Chuan
;
應用數學系
;
數學建模與科學計算所(含中心)
;
Department of Applied Mathematics
Let T be a Henon-type map induced from a spatial discretization of a reaction-diffusion system. With the above-mentioned description of T. the following open problems were raised in [V.S. Afraimovich, S B. Hsu, Lectures on Chaotic Dynamical Systems, AMS International Press, 2003]. Is it true that, in general, h(T) = h(D)(T)= h(N)(T) = hl((1)),(l(2)) (T)? Here h(T) and hl((1),(2)) (T) (see Definitions 1.1 and 1.2) are, respectively, the spatial entropy of the system T and the spatial entropy of T with respect to the lines e(l) and E(2), and h(D)(T) and h(N)(T) are spatial entropy with respect to the Dirichlet and Neuman boundary conditions. If it is not true, then which parameters of the lines l((1)), i = 1.2, are responsible for the value of h(T)? What kind of bifurcations occurs if the lines l((1)) move? In this paper, we show that this is in general not always true. Among other things, we further give conditions for which the above problem holds true. (C) 2010 Elsevier Inc. All rights reserved.
Ultrafast quasiparticle dynamics in heavy Ca-doped YBCO thin films
(2010-11-15)
Luo, C. W.
;
電子物理學系
;
Department of Electrophysics
The dynamics of photoinduced quasiparticle in the Y(1-x)Ca(x)Ba(2)Cu(3)O(7-delta) thin films is revealed by using the femtosecond reflection spectroscopy. For the case of x = 0.3, two distinct components have been clearly observed in the transient reflectivity change (Delta R/R). The positive component of Delta R/R appears well below T(c). Moreover, the divergent peak of temperature-dependent relaxation time (tau), which is believed to intimately relate to the opening of superconducting gap, shifts to lower temperature as increasing the Ca-doping in YBa(2)Cu(3)O(7-delta). (C) 2010 Elsevier B.V. All rights reserved.
Carbazole-Based Conjugated Polymers Incorporating Push/Pull Organic Dyes: Synthesis, Characterization, and Photovoltaic Applications
(2010-11-15)
Hsu, So-Lin
;
Chen, Chia-Min
;
Wei, Kung-Hwa
;
材料科學與工程學系
;
Department of Materials Science and Engineering
We have synthesized and characterized two new carbazole-based conjugated polymers, PCDCN and PCDTA, incorporating two strong light-absorbing organic dyes. These polymers exhibit relatively low band gaps (similar to 1.5 eV) and broad absorption ranges (from 300 to 700 nm). We fabricated polymer solar cells incorporating these polymers as donors and [6,6]-phenyl-C(71)-butyric acid methyl ester (PC(71)BM) as the acceptor. At a blending ratio of 1: 4, we obtained power conversion efficiencies, under simulated AM 1.5 (100 mW/cm(2)) conditions, of 2.31% and 2.47% for the PCDCN- and PCDTA-based devices, respectively. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 5126- 5134, 2010
Inelastic electron tunneling spectroscopy study of ultrathin Al(2)O(3)-TiO(2) dielectric stack on Si
(2010-11-15)
Liu, Zuoguang
;
Cui, Sharon
;
Kornblum, Lior
;
Eizenberg, Moshe
;
Chang, Ming-Feng
We report the properties of an ultrathin Al(2)O(3)-TiO(2) dielectric stack with the equivalent-oxide thickness=1.0 nm. The stack exhibits nondiscernable interfacial layer on Si, and absence of serious Al(2)O(3)-TiO(2) intermixing. Inelastic electron tunneling spectroscopy (IETS) has been used to provide a wealth of information concerning the phonons, bonding vibration modes, and traps in the Al(2)O(3)-TiO(2) gate dielectric stack as well as its interfaces in a metal-oxide-Si structure. The IETS spectra before and after forming gas annealing suggest that the reduction of traps is related to the formation of Si-H bonds at the oxide-Si interface. (C) 2010 American Institute of Physics. [doi:10.1063/1.3518478]
2-3 mu m mid infrared light sources using InGaAs/GaAsSb "W" type quantum wells on InP substrates
(2010-11-15)
Pan, C. H.
;
Lin, S. D.
;
Lee, C. P.
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
We have investigated the InGaAs/GaAsSb/InAlGaAs/InAlAs type-II "W" quantum wells (QWs) grown on InP substrates by molecular beam epitaxy. The photoluminescence (PL) emission wavelength longer than 2.56 mu m at room temperature (RT) is demonstrated for the first time in this material system. The PL emission peaks of our designed samples can cover a wide range from 2 to 2.5 mu m at cryogenic temperature. The samples show good optical quality that the reduction in integrated PL intensity is only around one order of magnitude from 35 K to RT. We found that the integrated PL intensity decreased as the emission wavelength increased, which is due to the reduction in the electron-hole wave function overlap. This is consistent with the calculated result. In the power dependent PL measurements, the emission peak of "W" type QWs show blue shifts with the excitation power (P-ex) but does not follow the P-ex(1/3) rule as predicted by type-II band bending model. The localized states filling effect gives reasonable explanations for the observed phenomena. (C) 2010 American Institute of Physics. [doi:10.1063/1.3506427]
Amorphous indium-gallium-zinc-oxide visible-light phototransistor with a polymeric light absorption layer
(2010-11-15)
Zan, Hsiao-Wen
;
Chen, Wei-Tsung
;
Hsueh, Hsiu-Wen
;
Kao, Shih-Chin
;
Ku, Ming-Che
This work demonstrates a real-time visible-light phototransistor comprised of a wide-band-gap amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film transistor (TFT) and a narrow-band-gap polymeric capping layer. The capping layer and the IGZO layer form a p-n junction diode. The p-n junction absorbs visible light and consequently injects electrons into the IGZO layer, which in turn affects the body voltage as well as the threshold voltage of a-IGZO TFT. The hysteresis behavior due to the charges at IGZO back interface is also discussed. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3517506]
Inelastic electron tunneling spectroscopy study of ultrathin Al2O3-TiO2 dielectric stack on Si
(2010-11-15)
Liu, Zuoguang
;
Cui, Sharon
;
Kornblum, Lior
;
Eizenberg, Moshe
;
Chang, Ming-Feng
We report the properties of an ultrathin Al2O3-TiO2 dielectric stack with the equivalent-oxide thickness=1.0 nm. The stack exhibits nondiscernable interfacial layer on Si, and absence of serious Al2O3-TiO2 intermixing. Inelastic electron tunneling spectroscopy (IETS) has been used to provide a wealth of information concerning the phonons, bonding vibration modes, and traps in the Al2O3-TiO2 gate dielectric stack as well as its interfaces in a metal-oxide-Si structure. The IETS spectra before and after forming gas annealing suggest that the reduction of traps is related to the formation of Si-H bonds at the oxide-Si interface. (C) 2010 American Institute of Physics. [doi:10.1063/1.3518478]
2-3 mu m mid infrared light sources using InGaAs/GaAsSb "W" type quantum wells on InP substrates
(2010-11-15)
Pan, C. H.
;
Lin, S. D.
;
Lee, C. P.
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
We have investigated the InGaAs/GaAsSb/InAlGaAs/InAlAs type-II "W" quantum wells (QWs) grown on InP substrates by molecular beam epitaxy. The photoluminescence (PL) emission wavelength longer than 2.56 mu m at room temperature (RT) is demonstrated for the first time in this material system. The PL emission peaks of our designed samples can cover a wide range from 2 to 2.5 mu m at cryogenic temperature. The samples show good optical quality that the reduction in integrated PL intensity is only around one order of magnitude from 35 K to RT. We found that the integrated PL intensity decreased as the emission wavelength increased, which is due to the reduction in the electron-hole wave function overlap. This is consistent with the calculated result. In the power dependent PL measurements, the emission peak of "W" type QWs show blue shifts with the excitation power (P(ex)) but does not follow the P(ex)(1/3) rule as predicted by type-II band bending model. The localized states filling effect gives reasonable explanations for the observed phenomena. (C) 2010 American Institute of Physics. [doi:10.1063/1.3506427]
Long electron dephasing length and disorder-induced spin-orbit coupling in indium tin oxide nanowires
(2010-11-15)
Hsu, Yao-Wen
;
Chiu, Shao-Pin
;
Lien, An-Shao
;
Lin, Juhn-Jong
;
電子物理學系
We have measured the quantum-interference magnetoresistances in two single indium tin oxide (ITO) nanowires between 0.25 and 40 K, by using the four-probe configuration method. The magnetoresistances are compared with the one-dimensional weak-(anti)localization theory to extract the electron dephasing length L(phi). We found, in a 60-nm-diameter nanowire with a low resistivity of rho(10 K) =185 mu Omega cm, that L(phi) is long, increasing from 150 nm at 40 K to 520 nm at 0.25 K. Therefore, the nanowire reveals strict one-dimensional weak-localization effect up to several tens of degrees of kelvin. In a second 72-nm-diameter nanowire with a high resistivity of rho(10 K)=1030 mu Omega cm, the dephasing length is suppressed to L(phi)(0.26 K)=200 nm, and thus a crossover of the effective device dimensionality from one to three occurs at about 12 K. In particular, disorder-induced spin-orbit coupling is evident in the latter sample, manifesting weak-antilocalization effect at temperatures below similar to 4 K. These observations demonstrate that versatile quantum-interference effects can be realized in ITO nanowires by controlling differing levels of atomic defects and impurities.
Amorphous indium-gallium-zinc-oxide visible-light phototransistor with a polymeric light absorption layer
(2010-11-15)
Zan, Hsiao-Wen
;
Chen, Wei-Tsung
;
Hsueh, Hsiu-Wen
;
Kao, Shih-Chin
;
Ku, Ming-Che
This work demonstrates a real-time visible-light phototransistor comprised of a wide-band-gap amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film transistor (TFT) and a narrow-band-gap polymeric capping layer. The capping layer and the IGZO layer form a p-n junction diode. The p-n junction absorbs visible light and consequently injects electrons into the IGZO layer, which in turn affects the body voltage as well as the threshold voltage of a-IGZO TFT. The hysteresis behavior due to the charges at IGZO back interface is also discussed. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3517506]
Controlled large strain of Ni silicide/Si/Ni silicide nanowire heterostructures and their electron transport properties
(2010-11-15)
Wu, W. W.
;
Lu, K. C.
;
Chen, K. N.
;
Yeh, P. H.
;
Wang, C. W.
Unusually large and compressively strained Si in nanoheterostructures of Ni silicide/Si/Ni silicide, in which the strain of the Si region can be achieved up to 10%, has been produced with point contact reactions between Si and Ni nanowires in an ultrahigh vacuum transmission electron microscope. The growth rate and relationships between the strain and the spacing of the Si region have been measured. Based on the rate and relationships, we can control the Si dimension and, in turn, the strain of remaining Si can be tuned with appropriate spacing. Since one-dimensional nanoheterostructures may have potential applications in nanoelectronic devices, the existent strain will further affect carrier mobility and piezoresistance coefficients in the Si region. Electrical measurements on the nanodevices from such nanoheterostructures show that the current output closely correlates with the Si channel length and compressive strain. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3515421]
Ultrafast quasiparticle dynamics in heavy Ca-doped YBCO thin films
(2010-11-15)
Luo, C. W.
;
電子物理學系
;
Department of Electrophysics
The dynamics of photoinduced quasiparticle in the Y(1-x)Ca(x)Ba(2)Cu(3)O(7-delta) thin films is revealed by using the femtosecond reflection spectroscopy. For the case of x = 0.3, two distinct components have been clearly observed in the transient reflectivity change (Delta R/R). The positive component of Delta R/R appears well below T(c). Moreover, the divergent peak of temperature-dependent relaxation time (tau), which is believed to intimately relate to the opening of superconducting gap, shifts to lower temperature as increasing the Ca-doping in YBa(2)Cu(3)O(7-delta). (C) 2010 Elsevier B.V. All rights reserved.
On investigation of high T(c) superconductors with Electron Paramagnetic Resonance spectrometers
(2010-11-15)
Shaltiel, D.
;
von Nidda, H. -A. Krug
;
Shapiro, B. Ya.
;
Bogoslavsky, B.
;
Rosenstein, B.
Following the discovery of high T(c) superconductors, many researchers have applied EPR spectrometers to investigate their properties using the regular instructions to operate the spectrometer. As no substantial information was obtained it was soon practically abandoned. Investigations performed recently with the EPR technique, using a different operating method than the conventional one and the introduction of a detailed theoretical study related to the interaction of the JV with the microwave magnetic field lead to new and important results related to properties of high anisotropy superconductors indicating that the EPR spectrometer can be used to investigate properties of high anisotropy superconductors. The failures when using conventional operating method to obtain meaningful results and the method used in the present work to carry out the measurements in a proper manner are presented. Some important results obtained in investigating high anisotropy superconductors by the EPR technique are presented. (C) 2010 Elsevier B.V. All rights reserved.
Light Emission Enhancement of GaN-Based Photonic Crystal With Ultraviolet AlN/AlGaN Distributed Bragg Reflector
(2010-11-15)
Chen, Cheng-Chang
;
Chen, Jun-Rong
;
Yang, Yi-Chun
;
Shih, M. -H.
;
Kuo, Hao-Chung
In this study, we demonstrated two-dimensional (2-D) photonic crystal band-edge coupling operation in the ultraviolet wavelength range. The light extraction enhancement was obtained from the photonic crystal structure with an ultraviolet AlN/AlGaN distributed Bragg reflector (UVDBR). The DBR provides a high reflectivity of 85% with 15-nm stopband width. A fivefold enhancement in photoluminescence emission was also achieved compared with the emission from the unpatterned area on the same sample at 374 nm wavelength. We also study the photonic crystal band-edge coupling with finite-difference time-domain and plane-wave expansion methods.
生醫感測器
(2010-11-16)
陳昱翰
;
廖倫德
;
趙昌博
;
林進燈
一種生醫感測器包括一光源、一探針陣列、以及一光感測器。光源用以發射一紅外光。探針陣列與一使用者之皮膚接觸，以檢測自皮膚發出並經由探針陣列傳遞之一電波訊號。探針陣列包括一基板、以及設置於基板之多個探針，其中基板與探針為可透光以使該紅外光通過探針陣列進入皮膚內紅外光通過探針陣列進入皮膚內。光感測器用以感測皮膚中紅外光吸收情形之一紅外光訊號。本發明藉由採用可透光探針以在功能性方面整合電波量測裝置與紅外光量測裝置於同一機構上。
有機光敏性光電裝置
(2010-11-16)
孟心飛
;
洪勝富
;
曾信榮
;
陳恩禎
;
朱家宏
一種有機光敏性之光電裝置，包括陽極；形成於該陽極上之包括供體部和受體部之有機光敏層；形成於該有機光敏層上之電洞阻擋層，使該有機光敏層夾置於該陽極和該電洞阻擋層之間；以及形成於該電洞阻擋層上之陰極，使該電洞阻擋層夾置於該陰極和該有機光敏層之間。此外，視需要地，該電洞阻擋層之最高電子佔據能階(HOMO)大於該供體部之最高電子佔據能階至少0.3eV。本發明之光電裝置有效地抑制暗電流以提升應用於偵測器時的靈敏度。
一種生物感測器
(2010-11-16)
孟心飛
;
洪勝富
;
趙宇強
;
洪韻茹
;
蔡佩妤
一種應用於生物感測環境之生物感測器，且為一可在液態環境下進行偵測的固態元件。本發明之生物感測器至少包含生物感測層、發光二極體、以及光偵測二極體；生物感測層於吸收、吸附及/或鍵結來自於生物體內部訊息傳遞時所釋放出的生物物質後，將導致其本身之發光性質之改變，經由發光二極體因激發所產生之光線的作用，致使生物感測層放出螢光；此些螢光經光偵測二極體吸收後，被轉變成可判讀的光電流訊號，進而，藉由光電流訊號之判讀而得知生物體內訊息交換之含意。