Browsing by Issue Date, starting with "2008-11-24"

Now showing 1 - 20 of 54086

Near-resonant high order nonlinear absorption of ZnO thin films
(2008-11-24)
Chan, Yun-Pei
;
Lin, Ja-Hon
;
Hsu, Chih-Chang
;
Hsieh, Wen-Feng
;
光電工程學系
Nonlinear optical absorption of ZnO thin film grown by the laser molecular beam epitaxy was investigated by the Z-scan method using a frequency-doubled femtosecond Ti:sapphire laser. Due to near-exciton resonance, an enormous enhancement of two photon absorption (TPA) is about 3000 cm/GW at 390 nm which is about 6.5 times larger than the previously reported at two-photon exciton resonance in near-IR regime and 710 times larger than that of ZnO bulk measured at 532 nm. Besides, the free-carrier absorption resulting from linear absorption and TPA becomes essential when the excitation approaches the exciton resonance. (C) 2008 Optical Society of America
從科技與環保的觀點看服務學習
(2008-11-24)
邵揮洲
;
開放教育推動中心
;
Open Education Office
課程日期： 2008年11月24日(三) 演講人：邵揮洲教授內容摘要：從服務學習的觀點看科技與環保：服務學習；關心健康、關愛世界(科技與環保、生活的真相)；大自然環境的破壞(氣候災變、環境暖化、少年暴力增加、遍地毒害)；人類健康意受到極大威脅(食衣住行育樂各方面)；建立新的人生觀，實踐儉樸生活(LOHAS)。內容：影音實況影音(*.flv檔)
The investigation of capture/emission mechanism in high-k gate dielectric soft breakdown by gate current random telegraph noise approach
(2008-11-24)
Chung, Steve S.
;
Chang, C. M.
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
In this paper, the trapping/detrapping in high-k gate dielectrics has been analyzed by gate current random telegraph noise (I(G)) measurement. Gate current is suppressed when traps capture electrons and recovers for empty traps. By statistically extracting capture and emission times, we can understand the trap properties. Besides, the influence will be understood by observing the variation of Gate current fluctuation. Through the analysis of the device after soft-breakdown (SBD), the deterioration of the dielectric will change the capture cross section. Moreover, the traps in the SBD path have been identified as the cause of a huge increase in the gate leakage.
Circa conservation of vibrational energy among three strongly coupled modes of a cyanine dye molecule studied by quantum-beat spectroscopy with a 7 fs laser
(2008-11-24)
Kobayashi, Takayoshi
;
Wang, Ying
;
Wang, Zhuan
;
Iwakura, Izumi
;
電子物理學系
Real-time energy exchange among the three vibrational modes forming a triplet with frequencies omega(1), omega(2), and omega(3) satisfying a 'circa sum-frequency relation', namely omega(1) + omega(2) congruent to omega(3) in a cyanine dye molecule has been studied with a 7-fs pulse laser. There are two triplets with average frequencies of the components of (146, 279, 432 cm (1)) and (279, 432, 738 cm (1)). Even though the circa sum-frequency relation is satisfied, circa- conservation of the vibrational energy holds among the three components only in the latter triplet. The difference between the two is ascribed to the symmetry of the molecular vibrational modes. (C) 2008 Elsevier B. V. All rights reserved.
Using Solvent Immersion to Fabricate Variably Patterned Poly(methyl methacrylate) Brushes on Silicon Surfaces
(2008-11-25)
Chen, Jem-Kun
;
Hsieh, Chih-Yi
;
Huang, Chih-Feng
;
Li, P. -M.
;
Kuo, Shiao-Wei
In this paper we describe a graft polymerization/solvent immersion method for generating various patterns of polymer brushes. We used a very-large-scale integration (VLSI) process to generate well-defined patterns of polymerized methyl methacrylate (MMA) on patterned Si(100) surfaces. A monolayer of Si(CH3)(3) groups was first generated to form an inert surface by reacting a hydroxylated Si surface with hexamethyldisilazane in a thermal evaporator. Oxygen plasma was the used to reactivate the patterned surface under a duty ratio of 1: 1 using electron beam lithography. The surface-generated oxygen species, such as Si-O and Si-O-O, reacted with the initiator for atom transfer radical polymerization (ATRP) on the patterned hydroxylated surface. The ATRP initiator on the patterned surface was then used for the graft polymerization of MMA to prepare the PMMA brushes. After immersion of wafers presenting lines and dots of these PMMA brushes in water and tetrahydrofuran, we observed mushroom- and brush-like regimes, respectively, for the PMMA brushes with various pattern resolutions.
Syntheses, Specific Interactions, and pH-Sensitive Micellization Behavior of Poly [vinylphenol-b-2-(dimethylamino)ethyl methacrylate] Diblock Copolymers
(2008-11-25)
Chen, Shih-Chien
;
Kuo, Shiao-Wei
;
Liao, Chun-Syong
;
Chang, Feng-Chih
;
應用化學系
We have used anionic polymerization to prepare a series of poly [vinylphenol-b-2(dimethylamino)ethyl methacrylate] (PVPh-b-PDMAEMA) block copolymers. These block copolymers are miscible, with strong specific interactions occurring between the OH groups of the PVPh segments and the tertiary ammonium groups of the PDMAEMA segments. These PVPh-b-PDMAEMA diblock copolymers exhibit higher glass transition temperatures than do the corresponding PVPh/partially protonated PDMAEMA blends obtained from DMSO solution, which we suspect exist in the form of separate coils. The blocks of the PVPh-b-PDMAEMA diblock copolymers interact strongly, resulting in polymer complex aggregation similar to the behavior of PVPh/partially protonated PDMAEMA blend complexes obtained from methanol solution. The spin-lattice relaxation times in the rotating frame, determined through solid state NMR spectroscopic analysis, provided clear evidence that the polymer complex aggregates formed from the diblock copolymers have shorter values of TV, than do the corresponding separated coils in the miscible blends. In addition, these PVPh-b-PDMAEMA diblock copolymers exhibit a novel type of pH sensitivity: at low pH, compact spherical micelles are formed possessing PDMAEMA coronas and PVPh cores; at medium pH, vesicles are observed, consisting of partially protonated hydrophilic PDMAEMA shells and hydrophobic PVPh cores; at high pH, the spherical micelles that formed comprised ionized PVPh coronas and deprotonated hydrated-PDMAEMA cores, i.e., phase inversion of the micelles formed at pH 2.
Temporary lag and anticipated synchronization and anti-synchronization of uncoupled time-delayed chaotic systems
(2008-11-25)
Ge, Zheng-Ming
;
Wong, Yu-Ting
;
Li, Shih-Yu
;
機械工程學系
;
Department of Mechanical Engineering
Without any control scheme and coupling terms, temporary lag and anticipated synchronization and temporary lag and anticipated anti-synchronization are newly discovered in two identical double Mackey-Glass systems with different initial conditions. When all initial conditions are positive, the lag synchronization is obtained. The negative initial values make the time history inverse and temporary lag anti-synchronization occur. The phenomena both appear intermittently. (C) 2008 Elsevier Ltd. All rights reserved.
Selective area growth carbon nanotubes by metal imprint method
(2008-11-25)
Wu
;
YewChung Sermon
;
Chao
;
Chi Wei
;
Hou
Manufacturing methods of using a metal imprint technique for growing carbon nanotubes on selective areas and the structures formed thereof are provided. One of the manufacturing methods includes steps of forming a first substrate with tapered structures applied with a metal catalyst, imprinting a second substrate on the first substrate for being a growth substrate, and growing carbon nanotubes on the growth substrate. The other manufacturing method includes steps of forming a first substrate with tapered structures, imprinting the first substrate on a second substrate applied with a metal catalyst for forming a second growth substrate, and growing carbon nanotubes on the second grown substrate. And, the formed structures of the present invention include a substrate, plural carbon nanotubes, and plural imprinted vestiges.
A High Efficiency Surface Modification Process for Multiwalled Carbon Nanotubes by Electron Cyclotron Resonance Plasma
(2008-11-27)
Tseng, Wen-Shou
;
Tseng, Chyuan-Yow
;
Chuang, Pi-Kai
;
Lo, An-Ya
;
Kuo, Cheng-Tzu
A novel process of surface modification for multiwalled carbon nanotubes (MWCNTs) by using electron cyclotron resonance plasma is proposed. The process uses a H(2)/O(2) gas mixture as etching gas and applies a bias voltage of -250 DCV to the process stage to extract and accelerate hydrogen and oxygen cations. The generated high density and high incident energy cations are employed to create defects on the surface of nanotubes through ion bombardment. The oxygen cations with high reduction potential are simultaneously applied, oxidizing the surface of the nanotubes so as to form functional groups on the side walls most effectively. Additionally, being far from the plasma sheath, the MWCNTs can be maintained at a lower temperature to prevent from being decomposed under the high energy plasma. The efficiency of this method was systematically analyzed using X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and thermogravimetric analysis. The experimental results have shown that the proposed method is a highly effective way to functionalize MWCNTs, resulting in the nanotubes with high concentration of oxygen-containing functional groups and minimal structural damage within very short process time.
Theoretical Investigation of Molecular Properties of the First Excited State of the Thiophenoxyl Radical
(2008-11-27)
Cheng, Chi-Wen
;
Lee, Yuan-Pern
;
Witek, Henryk A.
;
應用化學系
;
應用化學系分子科學碩博班
Accurate ab initio study of the lowest excited state (A (2)B(2)) of the thiophenoxyl radical is presented. The calculated equilibrium geometries, excitation energies, and harmonic vibrational frequencies show that the A (2)B(2) <- X (2)B(1) excitation in C(6)H(5)S has different characteristics than the analogous transition in the phenoxyl radical. Vertical excitation energies for other low-lying (<4.5 eV) excited states of the thiophenoxyl radical are also presented and compared with available experimental data.
Experimental and theoretical investigations of ionization/dissociation of cyclopentanone molecule in a femtosecond laser field
(2008-11-28)
Wang, Qiaoqiao
;
Wu, Di
;
Jin, Mingxing
;
Liu, Fuchun
;
Hu, Feifei
The ionization/dissociation mechanism of cyclopentanone has been experimentally investigated in molecular beam by irradiating with intense 394 and 788 nm laser fields with pulse duration of 90 fs. The range of laser intensities varied from 3 X 10(13) to 4 X 10(14) W/cm(2). For both wavelengths, the singly charged parent ion is observable while the doubly charged one cannot be found easily, although the fragmentation pattern supports its presence. Meanwhile, the extent of fragmentation at 788 nm is less than that in the 394 nm case. We quantitatively analyze the ionization processes of cyclopentanone in intense femtosecond laser by comparing the calculation results of ionization rate constants obtained from Ammosov-Delone-Krainov, Keldysh, and Keldysh-Faisal-Reiss (KFR) theories based on hydrogenlike atom model. We also compare the experimental and theoretical results; the generalized KFR theory is found to be useful in predicting the ionization yields of singly and doubly charged cyclopentanone ion. To interpret the dissociation patterns of the cyclopentanone ions, we have used the Rice-Ramsperger-Kassel-Marcus theory with the potential surfaces obtained from the ab initio quantum chemical calculations. (c) 2008 American Institute of Physics.
Structure and predissociation of the 3p sigma(u)D (3)Sigma(+)(u) Rydberg state of N(2): First extreme-ultraviolet and new near-infrared observations, with coupled-channels analysis
(2008-11-28)
Wang, Qiaoqiao
;
Wu, Di
;
Jin, Mingxing
;
Liu, Fuchun
;
Hu, Feifei
The 3p sigma(u)D (3)Sigma(+)(u) Rydberg state of N(2) is studied experimentally using two high-resolution spectroscopic techniques. First, the forbidden D (3)Sigma(+)(u)-X (1)Sigma(+)(g) transition is observed for the first time via the (0,0) band of (14)N(2) and the (1,0) band of (15)N(2), using 1 extreme-ultraviolet +1 ultraviolet two-photon-ionization laser spectroscopy. Second, the Rydberg-Rydberg transition D (3)Sigma(+)(u)-E (3)Sigma(+)(g) is studied using near-infrared diode-laser photoabsorption spectroscopy, thus extending the previous measurements of Kanamori [J. Chem. Phys. 95, 80 (1991)], to higher transition energies, and thereby revealing the (2,2) and (3,3) bands. The combined results show that the D(v=0-3) levels exhibit rapidly increasing rotational predissociation as v increases, spanning nearly four orders of magnitude. The D-state level structure and rotational predissociation signature are explained by means of a coupled-channels model which considers the electrostatically coupled (3)Pi(u) Rydberg-valence manifold, together with a pure-precession L-uncoupling rotational interaction between the 3p sigma(u)D (3)Sigma(+)(u) and 3p pi(u)G (3)Pi(u) Rydberg p-complex components.
A morphologically stable host material for efficient phosphorescent green and red organic light emitting devices
(2008-11-28)
Ho, Meng-Huan
;
Balaganesan, Banumathy
;
Chu, Ta-Ya
;
Chen, Teng-Ming
;
Chen, Chin H.
A carbazole-based host material, 4,4'-N,N'-[di(3, 6-di(t-butyl)carbazole]biphenyl (ttbCBP), with four t-butyl steric spacers on peripheral carbazole moieties was effectively synthesized through Friedel-Crafts Alkylation. Owing to the presence of sterically hindered t-butyl groups, ttbCBP exhibits a high glass transition temperature (175 degrees C) and is morphologically stable. This host material also preserves the characteristics of wide band-gap of 3.2 eV and high triplet energy of 2.64 eV. In addition, ttbCBP has been shown to be effective hosts for green and red phosphorescent emitters in organic electrophosphorescent devices. (C) 2008 Elsevier B.V. All rights reserved.
Direct observation of super-excited states in methane created by a femtosecond intense laser field
(2008-11-28)
Azarm, A.
;
Xu, H. L.
;
Kamali, Y.
;
Bernhardt, J.
;
Song, D.
We report, for the first time, a direct observation of the super-excited states of CH(4) in femtosecond intense laser fields using a pump (800 nm)-probe (1338 nm) technique. An unambiguous depletion of the CH (A (2) Delta -> X (2)Pi) fluorescence signal as a function of the delay time is attributed to the de-excitation of the super-excited states by the probe laser pulse. The lifetime of the super-excited state is measured to be about 160 fs.
Structure and predissociation of the 3p sigma(u)D (3)Sigma(+)(u) Rydberg state of N(2): First extreme-ultraviolet and new near-infrared observations, with coupled-channels analysis
(2008-11-28)
Wang, Qiaoqiao
;
Wu, Di
;
Jin, Mingxing
;
Liu, Fuchun
;
Hu, Feifei
The 3p sigma(u)D (3)Sigma(+)(u) Rydberg state of N(2) is studied experimentally using two high-resolution spectroscopic techniques. First, the forbidden D (3)Sigma(+)(u)-X (1)Sigma(+)(g) transition is observed for the first time via the (0,0) band of (14)N(2) and the (1,0) band of (15)N(2), using 1 extreme-ultraviolet +1 ultraviolet two-photon-ionization laser spectroscopy. Second, the Rydberg-Rydberg transition D (3)Sigma(+)(u)-E (3)Sigma(+)(g) is studied using near-infrared diode-laser photoabsorption spectroscopy, thus extending the previous measurements of Kanamori [J. Chem. Phys. 95, 80 (1991)], to higher transition energies, and thereby revealing the (2,2) and (3,3) bands. The combined results show that the D(v=0-3) levels exhibit rapidly increasing rotational predissociation as v increases, spanning nearly four orders of magnitude. The D-state level structure and rotational predissociation signature are explained by means of a coupled-channels model which considers the electrostatically coupled (3)Pi(u) Rydberg-valence manifold, together with a pure-precession L-uncoupling rotational interaction between the 3p sigma(u)D (3)Sigma(+)(u) and 3p pi(u)G (3)Pi(u) Rydberg p-complex components.
另類生活　活出現代的我
(2008-11-30)
梁素茵
;
Department of Communication and Technology
;
傳播與科技學系
未命名
大學生　課後都在忙什麼？
(2008-11-30)
林麗珊
;
Department of Communication and Technology
;
傳播與科技學系
高中畢業以後，大家會各奔前程，選擇繼續升學或是投身社會；近年來，澳門越來越多畢業生會選擇到台灣唸書，當中原因包括：澳門的大學數量少、科系少、社團少、崇拜台灣、訓練個人獨立生活等；然而，留在澳門唸書的同學也為數不少，因為賭業開放增加就業機會，同學們可以利用課餘時間去打工賺錢。兩地文化各異，因而令大學生的課外活動也各有特色，直接影響彼此的價值觀。
Simple Life──望鄉部落
(2008-11-30)
林潔
;
Department of Communication and Technology
;
傳播與科技學系
照片故事
撥弦的成功哲學─王祈文
(2008-11-30)
徐苾芬
;
Department of Communication and Technology
;
傳播與科技學系
還是XDDD
劉大潭以活躍邏輯代步人生
(2008-11-30)
楊睿愷
;
Department of Communication and Technology
;
傳播與科技學系
劉大潭對於生命的堅持與肯定，讓他勇往直前，突破自我。