Browsing by Issue Date, starting with "2009-03-13"

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Dynamics of Particle-Hole Pair Creation in Graphene
(2009-03-13)
Lewkowicz, M.
;
Rosenstein, B.
;
電子物理學系
;
Department of Electrophysics
The process of coherent creation of particle-hole excitations by an electric field in graphene is quantitatively described. We calculate the evolution of the current density, number of pairs, and energy after switching on the electric field. In particular, it leads to a dynamical visualization of universal finite resistivity without dissipation in pure graphene. We show that the dc conductivity of pure graphene is pi/2e(2)/h rather than the often cited value of 4/pi e(2)/h. This value coincides with the ac conductivity calculated and measured recently at optical frequencies. The effect of temperature and random chemical potential (charge puddles) are considered and explain the recent experiment on suspended graphene. A possibility of Bloch oscillations is discussed within the tight binding model.
《.hack//G.U. TRILOGY》
(2009-03-15)
曾韋澐
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Department of Communication and Technology
;
傳播與科技學系
0
又見棄養潮　滿街可魯跑
(2009-03-15)
趙祿平
;
Department of Communication and Technology
;
傳播與科技學系
敘述動物電影與棄養潮
STEP UP ! 舞力全開 !
(2009-03-15)
洪上筑
;
Department of Communication and Technology
;
傳播與科技學系
怎麼還是梅竹花絮QQ
電玩之歌音樂新領域
(2009-03-15)
何宛芯
;
Department of Communication and Technology
;
傳播與科技學系
文化與音樂
現外籍婚姻《我的強娜威》
(2009-03-15)
林潔
;
Department of Communication and Technology
;
傳播與科技學系
　　
《太陽》之下飛翔
(2009-03-15)
蔡尚翰
;
Department of Communication and Technology
;
傳播與科技學系
《太陽》之下飛翔陳綺貞之樂評
百萬人生《Q&A》
(2009-03-15)
王成宇
;
Department of Communication and Technology
;
傳播與科技學系
貧民百萬富翁原著
梅竹誰在鬧網路攻訐戰
(2009-03-15)
邵奕儒
;
Department of Communication and Technology
;
傳播與科技學系
梅竹賽後，體育場上的戰爭延伸至學生慣用的言論天地─網路
Carbon attachment on the aluminum nitride gate dielectric in the pentacene-based organic thin-film transistors
(2009-03-15)
Zan, Hsiao-Wen
;
Chou, Cheng-Wei
;
Wang, Chung-Hwa
;
Song, Ho-Tsung
;
Hwang, Jenn-Chang
This study presents carbon attachment on an aluminum nitride (AlN) gate dielectric to improve the device performance of pentacene-based organic thin-film transistors (OTFTs). This approach produces high OTFT performance on an aged AlN surface. A high mobility of 0.67 cm(2)/V s was achieved on an AlN surface aged for 14 days, compared to a mobility of 0.05 cm(2)/V s on an as-deposited AlN surface. This improvement in device performance is correlated with carbon attachment on the AlN surface, which lowers surface energy. The lowered surface energy made the surface less polar, as measured by a contact angle instrument. The chemical composition of the aged AlN surface was analyzed using x-ray photoelectron spectroscopy before pentacene deposition. Enhanced C=C bonding at 284.5 eV was observed on the aged AlN surface. These enhanced C=C bonds favored the growth of large pentacene islands in the initial growth stage, which may improve OTFT device performance.
《家有囍事2009》迎來新年賀歲片
(2009-03-15)
鄭秀芳
;
Department of Communication and Technology
;
傳播與科技學系
0
Influence of thermal annealing on the electron emission of InAs quantum dots containing a misfit defect state
(2009-03-15)
Chen, J. F.
;
Yang, C. H.
;
Hsu, R. M.
;
Wang, U. S.
;
電子物理學系
We have investigated the effect of postgrowth thermal annealing on the electron emission from InAs quantum dots (QDs) containing a misfit-related defect state induced by strain relaxation. Additional carrier depletion in the GaAs bottom layer near the QD, caused by the defect state, can effectively suppress electron tunneling from the QD, leading to the observation of a thermal emission from the QD electron ground state to the GaAs conduction band with a large emission energy of 213 meV, in contrast to defect-free nonrelaxed QDs in which an emission of 58 meV from the QD electron ground state to first excited state is observed. The emission energy is reduced to 193 meV and to 164 meV after annealing at 650 and 700 degrees C for 1 min, respectively. This emission energy reduction is correlated with the photoluminescence blueshift which is attributed to the interdiffusion of atoms across the QD interface. The electron emission from the QD first excited and ground states is found to be a thermal emission at high temperatures and a tunneling emission at low temperatures. The tunneling energy barrier is found to be comparable to the thermal emission energy, supporting a thermal emission to the GaAs conduction band. This study illustrates a significant effect of a defect state on the electron-emission process in the QDs, suggesting the possibility of modifying the electron emission time of the QDs by purposely introducing a deep defect state.
《家有囍事》第三樁
(2009-03-15)
林麗珊
;
Department of Communication and Technology
;
傳播與科技學系
影評
自治自覺　原住民當自強
(2009-03-15)
葉曉昀
;
Department of Communication and Technology
;
傳播與科技學系
談論原住民族在台灣最好的生存之道就是擁有自主權
Growth of free-standing GaN layer on Si(111) substrate
(2009-03-15)
Yang, Tsung Hsi
;
Ku, Jui Tai
;
Chang, Jet-Rung
;
Shen, Shih-Guo
;
Chen, Yi-Cheng
This investigation demonstrates the epitaxial growth of a free-standing GaN layer on Si(1 1 1) using a funnel-like GaN nano-rod buffer structure. The funnel-like GaN nano-rods were directly grown on Si substrates by RF-plasma molecular beam epitaxy. Free-standing GaN layers were achieved through the coalescence of funnel-like GaN nano-rods by the metalorganic chemical vapor deposition. This study examines the structure, optical characteristics and stress of GaN nano-rods and free-standing GaN layers. The c-axis lattice constant of the strain-free Ga-face GaN layer on Si is 5.1844 angstrom, as determined by high-resolution X-ray diffraction. The fully relaxed band edge at 3.468 eV without deep-level emission around 2.3 eV, was revealed in a free-standing GaN layer on Si, using photoluminescence. (C) 2008 Elsevier B.V. All rights reserved.
《真愛旅程》對虛假社會進行革命
(2009-03-15)
張雅晴
;
Department of Communication and Technology
;
傳播與科技學系
真愛旅程對虛假社會進行革命
第四十二期總編輯的話
(2009-03-15)
徐苾芬
;
Department of Communication and Technology
;
傳播與科技學系
我是總編了好緊張
Optical properties of a-plane InGaN/GaN multiple quantum wells on r-plane sapphire substrates with different indium compositions
(2009-03-15)
Chiu, C. H.
;
Kuo, S. Y.
;
Lo, M. H.
;
Ke, C. C.
;
Wang, T. C.
A-plane In(x)Ga(1-x)N/GaN (x=0.09, 0.14, 0.24, and 0.3) multiple-quantum-wells (MQWs) samples, with a well width of about 4.5 nm, were achieved by utilizing r-plane sapphire substrates. Optical quality was investigated by means of photoluminescence (PL), cathodoluminescence, and time resolved PL measurements (TRPL). Two distinguishable emission peaks were examined from the low temperature PL spectra, where the high- and low-energy peaks were ascribed to quantum wells and localized states, respectively. Due to an increase in the localized energy states and absence of quantum confined Stark effect, the quantum efficiency was increased with increasing indium composition up to 24%. As the indium composition reached 30%, however, pronounced deterioration in luminescence efficiency was observed. The phenomenon could be attributed to the high defect densities in the MQWs resulted from the increased accumulation of strain between the InGaN well and GaN barrier. This argument was verified from the much shorter carrier lifetime at 15 K and smaller activation energy for In(0.3)Ga(0.7)N/GaN MQWs. In addition, the polarization-dependent PL revealed that the degree of polarization decreased with increasing indium compositions because of the enhancement of zero-dimensional nature of the localizing centers. Our detailed investigations indicate that the indium content in a-plane InGaN/GaN MQWs not only has an influence on optical performance, but is also important for further application of nitride semiconductors.
《貧民百萬富翁》好運發自內心
(2009-03-15)
陳怡秀
;
Department of Communication and Technology
;
傳播與科技學系
影評
Enhanced field-effect mobility in pentacene based organic thin-film transistors on polyacrylates
(2009-03-15)
Cheng, Jung-An
;
Chuang, Chiao-Shun
;
Chang, Ming-Nung
;
Tsai, Yun-Chu
;
Shieh, Han-Ping D.
We reported on organic thin-film transistors (OTFTs) with high dielectric constant polymer, poly(2,2,2-trifluoroethyl methacrylate) (PTFMA), as the gate dielectric. In top-contact OTFTs, the field-effect mobility was enhanced by applying a dielectric buffer layer poly(alpha-methylstyrene) to the bare PTFMA. After improving interfacial affinity within the active layer/dielectrics, deposited pentacene grain size and device performance were enhanced dramatically. The corresponding mobility, threshold voltage, and on/off current ratio were 0.70 cm(2) V(-1) s(-1), -10.5 V, and 5.4x10(5), respectively. The moderately improved interface also suppressed the hole-trapping effect, which led to less hysteresis and minimized threshold voltage shift.