Browsing by Issue Date, starting with "2006-01-21"

Now showing 1 - 20 of 63791

Potassium ion recognition by 15-crown-5 functionalized CdSe/ZnS quantum dots in H2O
(2006-01-21)
Chen, CY
;
Cheng, CT
;
Lai, CW
;
Wu, PW
;
Wu, KC
Based on 15-crown-5 functionalized CdSe/ZnS quantum dots (QDs), we report a novel fluorogenic sensor to probe K+ ions in H2O; recognition of K+ can be achieved via the Forster type of energy transfer between two different color QDs, so that [K+] of the order of 10(-6) M can be promptly detected.
全空乏型絕緣層上矽晶金氧半場效電晶體裝置及其製法
(2006-01-21)
崔秉鉞
;
林家彬
本發明提出一種奈米尺寸之高性能絕緣層上矽晶金氧半場效電晶體裝置及其製法，其特徵在於裝置包括：一金屬氧化物半導體形成於絕緣層上矽晶基板之上；一金屬矽化物層，在閘極方面具有單一之全金屬矽化物閘極、高介電常數介電層以及可調變功函數之部件；在源、汲極部分則具有除了完全反應之金屬矽化物之源、汲極外，以及修正蕭基接面之源極與汲極結構。
Path-dependent human identification using a pyroelectric infrared sensor and Fresnel lens arrays
(2006-01-23)
Fang, JS
;
Hao, Q
;
Brady, DJ
;
Shankar, M
;
Guenther, BD
This paper presents a design and development of a low power consumption, and low cost, human identification system using a pyroelectric infrared (PIR) sensor whose visibility is modulated by a Fresnel lens array. The optimal element number of the lens array for the identification system was investigated and the experimental results suggest that the lens array with more elements can yield a better performance in terms of identification and false alarm rates. The other parameters of the system configuration such as the height of sensor location and sensor-to-object distance were also studied to improve spectral distinctions among sensory data of human objects. The identification process consists of two parts: training and testing. For the data training, we employed a principal components regression (PCR) method to cluster data with respect to different registered objects at different speed levels. The feature data of different objects walking along the same path in training yet at random speeds are then tested against the pre-trained clusters to decide whether the target is registered, and which member of the registered group it is. (c) 2006 Optical Society of America.
Synthesis and characterization of light-emitting H-bonded complexes and polymers containing bis(pyridyl) emitting acceptors
(2006-01-24)
Lin, HC
;
Tsai, CM
;
Huang, GH
;
Tao, YT
;
材料科學與工程學系
A series of bis(pyridyl) acceptor emitters are synthesized and the LC and photophysical (PL and EL) properties of their supramolecular structures, including H-bonded polymer networks and trimers, are explored. Unique mesomorphic properties may be introduced into these H-bonded complexes and polymers containing nonmesogenic acceptor emitters. In addition, the emission properties of bis(pyridyl) acceptor emitters can be adjusted by their surrounding nonphotoluminescent proton donors. Compared with pure bis(pyridyl) acceptor emitters, red-shifts of PL emission wavelengths were observed in most of the H-bonded complexes and polymers. Because of the higher acidity value of m-PC(10)BA (16) and its stronger H-bonded effect in H-bonded polymer complexes, the largest red-shift of 93 nm in lambda(max) value of PL has occurred in the fully H-bonded polymer network p-PBBBP-OC8 (8)/m-PC(10)BA (16) in contrast to pure emitter p-PBBBP-OC8 (8). A very narrow full width at half-maximum (fwhm) value (38 nm) of EL spectra can be obtained in the device of H-bonded complexes blended with PVK, and a higher brightness of EL is produced at an appropriate annealing temperature.
Induced twisting in the self-assembly of chiral Schiff-based rod-coil amphiphiles
(2006-01-24)
Sung, CH
;
Kung, LR
;
Hsu, CS
;
Lin, TF
;
Ho, RM
A series of novel organic superstructures exhibiting diverse aggregate morphologies with liquid-crystalline-like properties were prepared by a simple precipitation method. Here, a chiral sugar moiety was simply introduced at the Schiff-based rod end of rod-coil molecules. In contrast to coil-coil molecules, the self-assembled rod-coil molecules exhibit a high segregation strength for phase separation because of their liquid-crystalline-like behavior. The morphological transformation of self-assembled chiral Schiff-based rod-coil amphiphiles, from a platelet-like morphology to helical twists, was obtained by increasing the length of the hydrophobic tail. Consistent with theoretical predictions, the bending force from the chiral entity depends on the size of the adjacent hydrophobic tail. That is, the size of hydrophobic chain determines the threshold of bending for the formation of a helical morphology. Moreover, by introducing an additional tethered hydrophobic chain self-assembled spherical vesicles can be obtained through the collapse of the twisted shape.
MOCVD growth of highly strained 1.3 mu m InGaAs : Sb/GaAs vertical cavity surface emitting laser
(2006-01-25)
Chang, YA
;
Chu, JT
;
Ko, CT
;
Kuo, HC
;
Lin, CF
In0.45Ga0.55As:Sb/GaAs (1.3 mu m) vertical cavity surface emitting lasers (VCSELs) were grown by metalorganic chemical vapor deposition (MOCVD). A In0.45Ga0.55As:Sb/GaAs quantum well (QW) exhibited an emission wavelength of 1.26 mu m with narrow fullwidth at half-maximum (FWHM) of 35.9meV. For the fabricated VCSEL with 5 mu m diameter oxide-confined aperture, a room-temperature (RT).threshold current of 2.1 mA and an output power of 0.9 mW with 1.3 mu m emission were obtained. The 3 dB modulation frequency was measured to be 7.6 GHz. (c) 2005 Elsevier B.V. All rights reserved.
Quaternary AlInGaN multiple quantum well 368 nm light-emitting diode
(2006-01-25)
Wang, TC
;
Kuo, HC
;
Lee, ZH
;
Chuo, CC
;
Tsai, MY
We report high output power from AlInGaN multiple quantum well (MQW) ultraviolet light-emitting diodes. The high Al containing cladding layer, electron blocking layer and p-contact layer were chosen for transparency at 365 nm to reduce the internal absorption, reduce electron overflow and enhance output power. The UV output power was as high as 1.52 mW at 20 mA at 368 nm under room temperature CW operation. The maximum output power in CW operation is 11 mW at 170 mA. In this letter, we demonstrate a helpful and easy way to measure and calculate the junction temperature of AlInGaN UVLEDs. (c) 2005 Elsevier B.V. All rights reserved.
Structural evolution of AlN nano-structures: Nanotips and nanorods
(2006-01-25)
Shi, SC
;
Chattopadhyay, S
;
Chen, CF
;
Chen, KH
;
Chen, LC
Aluminum nitride (AIN) nanostructures were prepared using thermal chemical vapour deposition process. At growth temperatures of 950 degrees C, AIN nanotips with apex diameters of 10 nm, base diameters of similar to 100 nm, and length of similar to 2000 nm were obtained. Whereas when the growth temperature was 1200 degrees C, we obtained shorter and ihicker AIN nanorods. Compelling microscopic evidences were obtained to show that stacked AIN platelets of diminishing size formed the building blocks for the nanotips. A reducing Ehrlich-Schwoebel barrier introduced into a diffusion mediated growth model explains the formation of AIN nanorods at increasing growth temperatures. (c) 2005 Elsevier B.V. All rights reserved.
Manifestation of weak localization and long-range correlation in disordered wave functions from conical second harmonic generation
(2006-01-27)
Chen, YF
;
Su, KW
;
Lu, TH
;
Huang, KF
;
電子物理學系
We experimentally demonstrate that the near-field patterns of conical second harmonic generation of a laser in random domain structures can be used to explore the spatial structure of two-dimensional disordered wave functions with weak localization. The statistics of the experimental near-field patterns agree very well with the theoretical distributions. In addition to the short-range correlation, the localization effects are found to contribute a nearly constant value to the long-range correlation. The result of this Letter also confirms the possibility of using conical second harmonic generation as a diagnostic tool for topographical characterization of crystals.
Observation of spatially coherent polarization vector fields and visualization of vector singularities
(2006-01-27)
Chen, YF
;
Lu, TH
;
Huang, KF
;
電子物理學系
;
Department of Electrophysics
We present experimental observations of polarization vector fields from a highly isotropic microchip laser with a large Fresnel number. The experimental polarization vector field leads to complex entanglement of spatial structures and polarization states. We theoretically derive the representation of generalized coherent states to reconstruct the experimental polarization-resolved patterns. The analytical and precise reconstruction enables the vector singularities to be clearly visualized.
Fabrication of single-crystal tin nanowires by hydraulic pressure injection
(2006-01-28)
Chen, CC
;
Bisrat, Y
;
Luo, ZP
;
Schaak, RE
;
Chao, CG
Tin (Sn) nanowires, with 15 and 60 mn average diameter and up to 10 mu m in length, were fabricated by an injection process using a hydraulic pressure method. The Sn melt was injected into an anodic aluminium oxide (AAO) template and solidified to form nanowires. By back etching the aluminium substrate and barrier layer, the nanowire array ends were partially exposed from the bottom face of the AAO template. The filling ratio of nanowires inside and through the thickness of the AAO template was found to be close to 100%. The nanowires were also found to be dense and continuous with uniform diameter throughout their length. Transmission electron microscope (TEM) and x-ray diffraction (XRD) studies on the 60 nm diameter nanowires revealed that the nanowires were single crystals with body-centred-tetragonal (bct) structure predominantly growing along the [100] direction. The current method of synthesizing nanowires is straightforward, low-cost and suitable for low-melting point (< 650 degrees C) metals including low-melting point alloys with stoichiometric composition.
Triplet-triplet energy-transfer coupling: Theory and calculation
(2006-01-28)
You, ZQ
;
Hsu, CP
;
Fleming, GR
;
應用化學系分子科學碩博班
;
Institute of Molecular science
Triplet-triplet (TT) energy transfer requires two molecular fragments to exchange electrons that carry different spin and energy. In this paper, we analyze and report values of the electronic coupling strengths for TT energy transfer. Two different methods were proposed and tested: (1) Directly calculating the off-diagonal Hamiltonian matrix element. This direct coupling scheme was generalized from the one used for electron transfer coupling, where two spin-localized unrestricted Hartree-Fock wave functions are used as the zero-order reactant and product states, and the off-diagonal Hamiltonian matrix elements are calculated directly. (2) From energy gaps derived from configuration-interaction-singles (CIS) scheme. Both methods yielded very similar results for the systems tested. For TT coupling between a pair of face-to-face ethylene molecules, the exponential attenuation factor is 2.59 A(-1)(CIS/6-311+G(**)), which is about twice as large as typical values for electron transfer. With a series of fully stacked polyene pairs, we found that the TT coupling magnitudes and attenuation rates are very similar irrespective of their molecular size. If the polyenes were partially stacked, TT couplings were much reduced, and they decay more rapidly with distance than those of full-stacked systems. Our results showed that the TT coupling arises mainly from the region of close contact between the donor and acceptor frontier orbitals, and the exponential decay of the coupling with separation depends on the details of the molecular contacts. With our calculated results, nanosecond or picosecond time scales for TT energy-transfer rates are possible. (c) 2006 American Institute of Physics.
Rotational entangled states between two coupled molecules
(2006-01-28)
Liao, YY
;
Chen, YN
;
Li, CM
;
Chuu, DS
;
電子物理學系
A method is proposed to create entanglement between two coupled identical polar molecules separated at a distance of tens of nanometres. Entangled states of two coupled polar molecules controlled by half-cycle pulses are studied theoretically. The von Neumann entropy is calculated to characterize the degree of entanglement. By varying the pulse shape of the applied laser, transition from regular to irregular behaviour occurs. Moreover, the entanglement is also found to be enhanced by applying multiple laser pulses. The behaviour from quantum to classical limit is also discussed.
Semiconducting single-walled carbon nanotubes exposed to distilled water and aqueous solution: Electrical measurement and theoretical calculation
(2006-01-30)
Lu, MP
;
Hsiao, CY
;
Lo, PY
;
Wei, JH
;
Yang, YS
We fabricate and measure a single-walled carbon nanotube transistor having a liquid-gate electrode. The ratio value of I-on/I-off is as high as 10(4), indicating the presence of a semiconducting channel. A passivation layer over the source/drain electrode greatly suppresses the liquid-gate leakage by about three orders of magnitude. The channel currents are noticeably distinct between two liquid samples: distilled water and aqueous solution (1x10(-4) M NaCl). This biological sensing ability is attributed to the different electrical double-layer capacitances with respect to the bulk part of the channel. The corresponding theoretical calculation is carried out in detail. (c) 2006 American Institute of Physics.
Manufacturing method of thin film transistor
(2006-01-31)
Chang
;
Kow Ming
;
Chung
;
Yuan Hung
A method of manufacturing a thin film transistor for solving the drawbacks of the prior arts is disclosed. The method includes steps of providing an insulating substrate, sequentially forming a source/drain layer, a primary gate insulating layer, and a first conducting layer on the insulating substrate, etching the first conducting layer to form a primary gate; sequentially forming a secondary gate insulating layer and a second conducting layer on the primary gate; and etching the second conducting layer to form a first secondary gate and a second secondary gate.
雪泥
(2006-02-01)
管管
Optical properties of surface micromachining with randomly distributed etch holes
(2006-02-01)
Tien, CH
;
Lee, CH
;
光電工程學系
;
顯示科技研究所
;
Department of Photonics
Optical micromachining or microelectromechanical systems (MEMS) typically require etch holes to reduce the time required to release the micromechanical structure during the sacrificial undercutting. However, high-order diffraction beams generated by the periodic etch-hole array often deteriorate the optical performance by generating noise and erroneous crosstalk signals in. most optical systems. In this study, we examined the diffraction from a perforated micromirror and proposed a random distributed etch-hole layout. Due to the superposition of cosine functions with random periods, noise caused by high-order beams can be averaged effectively.
Memory effect on the inelastic interaction of electrons moving parallel to a solid surface
(2006-02-01)
Kwei, CM
;
Hsu, YH
;
Tu, YH
;
Tung, CJ
;
電子工程學系及電子研究所
It is generally assumed that two successive inelastic interactions between an electron and a solid are independent of each other. In other words, the electron has no memory of its previous interaction. However, the previous interaction of the electron generates a potential that should influence its succeeding inelastic interaction. The aim of this work is to establish a model to account for the memory effect of an electron between two successive inelastic interactions. On the basis of the dielectric response theory, formulae for differential inverse inelastic mean free paths (DIIMFPs) and inelastic mean free paths (IMFPs) considering the memory effect were derived for electrons moving parallel to a solid surface by solving the Poisson equation and applying suitable boundary conditions. These mean free paths were then calculated with the extended Drude dielectric function for a Cu surface. It was found that the DIIMFP and the IMFP with the memory effect for electron energy E lay between the corresponding values without the memory effect for electron energy E and previous energy Eo. The memory effect increased with increasing electron energy loss, E-0 - E-1 in the previous inelastic interaction. Copyright (c) 2005 John Wiley & Sons, Ltd.
雪泥
(2006-02-01)
管管
A compact DSP core with static floating-point arithmetic
(2006-02-01)
Lin, TJ
;
Lin, HY
;
Chao, CM
;
Liu, CW
;
Jen, CW
A multimedia system-on-a-chip (SoC) usually contains one or more programmable digital signal processors (DSP) to accelerate data-intensive computations. But most of these DSP cores are designed originally for standalone applications, and they must have some overlapped (and redundant) components with the host microprocessor. This paper presents a compact DSP for multi-core systems, which is fully programmable and has been optimized to execute a set of signal processing kernels very efficiently. The DSP core was designed concurrently with its automatic software generator based on high-level synthesis. Moreover, it performs lightweight arithmetic-the static floating-point (SFP), which approximates the quality of floating-point (FP) operations with the hardware similar to that of the integer arithmetic. In our simulations, the compact DSP and its auto-generated software can achieve 3X performance (estimated in cycles) of those DSP cores in the dual-core baseband processors with similar computing resources. Besides, the 16-bit SFP has above 40 dB signal to round-off noise ratio over the IEEE single-precision FP, and it even outperforms the hand-optimized programs based on the 32-bit integer arithmetic. The 24-bit SFP has above 64 dB quality, of which the maximum precision is identical to that of the single-precision FP. Finally, the DSP core has been implemented and fabricated in the UMC 0.18 mu m 1P6M CMOS technology. It can operate at 314.5 MHz while consuming 52mW average power. The core size is only 1.5 mmx1.5 mm including the 16 KB on-chip memory and the AMBA AHB interface.