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排序方式: 共有196条查询结果,搜索用时 718 毫秒
71.
Champagne N.J. II Williams J.T. Sharpe R.M. Hwu S.-U. Wilton D.R. 《Antennas and Propagation, IEEE Transactions on》1992,40(1):102-108
A method of moments formulation for the current on arbitrarily shaped thin wires is applied to the problem of radiation and scattering from Archimedean spiral antennas. This formulation includes impedance loading along the wires. Additional analysis is performed to take advantage of structures which exhibit discrete rotational symmetry. Numerical results for a four-arm Archimedean spiral antenna with and without impedance loading are compared, showing that the loading significantly affects the current distribution and the far-field pattern for the higher order modes 相似文献
72.
73.
Due to the oscillatory characteristics of stresses near interface crack tips, the stress intensity factor Ki, i = I, II, III, should be modified and the energy release rate Gi, i = 1, 2, 3, of each fracture mode calculated by the virtual crack closure method may not exist. Based upon a near-tip solution for interface cracks between dissimilar anisotropic media, a proper definition for the stress intensity factors and energy release rates for general anisotropic bimaterial interface cracks is provided in this paper, which is applicable for the delaminated composites. Moreover, this definition can be reduced to the classical definition for a crack tip in homogeneous media when the two materials become the same. A simple quadratic relation between Ki and Gi is derived, which is further reduced explicitly for orthotropic bimaterials. The influence of fiber orientation and the coupling among opening, shearing and tearing mode fracture are studied numerically. The results show that the classical stress intensity factors and energy release rates are still the dominant stress intensity and energy release rate of the mixed mode condition induced by the interface. 相似文献
74.
Reduction in leakage current of low-temperature thin-gate oxide byrepeated spike oxidation technique
Chao-Chi Hong Chang-Yun Chang Chaung-Yuan Lee Jenn-Gwo Hwu 《Electron Device Letters, IEEE》2002,23(1):28-30
A novel repeated spike oxidation (RSO) technique had been used to grow low-temperature thin-gate oxide. Around the similar effective oxide thickness extracted from the capacitance-voltage (C-V) curves under quantum mechanical effect consideration, the leakage currents of RSO samples were near one order of magnitude lower than those of typical ones. Flat band voltage shift or electron trapping in RSO oxides during current-voltage (I-V) measurement had not been observed. The reduction of interface state densities and the improvement in oxide uniformity would be the possible reasons for the reduction in leakage currents of RSO samples 相似文献
75.
Sun CJ Chow GM Soo EW Wang JP Hwu YK Cho TS Je JH Lee HH Kim JW Noh DY 《Journal of nanoscience and nanotechnology》2001,1(3):271-273
The effects of long-range and short-range orders of Ti underlayer thickness on the magnetic properties of sputtered Co72 Cr21 Pt7 films were investigated using synchrotron X-ray scattering and X-ray absorption near-edge structure spectroscopy. The results were consistent with that of magnetic measurements and X-ray photoelectron spectroscopy. For thin Ti underlayers (10 nm), the oxidation of Ti and significant mixing of other elements within this underlayer did not promote texture development, further resulting in poor texturing of magnetic films and undesirable magnetic properties. Increased crystallinity and texture of metallic Ti in thicker underlayers enhanced the magnetic peak alignment and its properties. 相似文献
76.
Yang G.W. Hwu R.J. Xu Z.T. Ma X.Y. 《IEEE journal of selected topics in quantum electronics》2000,6(4):577-584
We conduct a theoretical analysis of the design, fabrication, and performance measurement of high-power and high-brightness strained quantum-well lasers emitting at 0.98 /spl mu/m. The material system of interest consists of an Al-free InGaAs-InGaAsP active region and AlGaAs cladding layers. Some key parameters of the laser structure are theoretically analyzed, and their effects on the laser performance are discussed. The laser material is grown by metal-organic chemical vapor deposition and demonstrates high quality with low-threshold current density, high internal quantum efficiency, and extremely low internal loss. High-performance broad-area multimode and ridge-waveguide single-mode laser devices are fabricated. For 100-/spl mu/m-wide stripe lasers having a cavity length of 800 /spl mu/m, a high slope efficiency of 1.08 W-A, a low vertical beam divergence of 34/spl deg/, a high output power of over 4.45 W, and a very high characteristic temperature coefficient of 250 K were achieved. Lifetime tests performed at 1.2-1.3 W (12-13 mW//spl mu/m) demonstrates reliable performance. For 4-/spl mu/m-wide ridge waveguide single-mode laser devices, a maximum output power of 394 mW and fundamental mode power up to 200 mW with slope efficiency of 0.91 mW//spl mu/m are obtained. 相似文献
77.
P. P. Lee R. J. Hwu L. P. Sadwick H. Balasubramaniam B. R. Kumar R. Alvis R. T. Lareau M. C. Wood 《Journal of Electronic Materials》1998,27(5):405-408
There is a significant interest in the area of improving high temperature stable contacts to III-V semiconductors. Two attractive
material systems that offer promise in this area are dysprosium phosphide/gallium arsenide (DyP/GaAs) and dysprosium arsenide/gallium
arsenide (DyAs/GaAs). Details of epitaxial growth of DyP/GaAs and DyAs/GaAs by molecular beam epitaxy (MBE), and their characterization
by x-ray diffraction, transmission electron microscopy, atomic force microscopy, Auger electron spectroscopy, Hall measurements,
and high temperature current-voltage measurements is reported. DyP is lattice matched to GaAs, with a room temperature mismatch
of less than 0.01% and is stable in air with no sign of oxidation, even after months of ambient exposure. Both DyP and DyAs
have been grown by solid source MBE using custom designed group V thermal cracker cells and group III high temperature effusion
cells. High quality DyP and DyAs epilayer were consistently obtained for growth temperatures ranging from 500 to 600°C with
growth rates between 0.5 and 0.7 μm/h. DyP epilayers are n-type with electron concentrations of 3 × 1020 to 4 × 1020 cm−3, room temperature mobilities of 250 to 300 cm2/V·s, and a barrier height of 0.81 eV to GaAs. DyAs epilayers are also n-type with carrier concentrations of 1 × 1021 to 2 × 1021 cm−3, and mobilities between 25 and 40 cm2/V·s. 相似文献
78.
The one invited paper and four selected papers in this special issue provide a good sampling of advances in the broad space of accelerator applications and architectures. 相似文献
79.
Yen-Hao Shih Jenn-Gwo Hwu 《Electron Device Letters, IEEE》1999,20(11):545-547
A novel technique called chemical-assisted electron stressing followed by annealing (CAESA) is proposed to improve a thin gate oxide film's quality, After conventional oxide growth, the wafer was put into diluted HF solution (0.245%) and was current stressed in liquid with Si substrate biased negatively, It is believed the stressing current will find the local weak spots and damage them by the energy release of electrons, With additional high-temperature rapid thermal annealing (RTA), the damaged spots will be annealed out. It is found that the charge-to-breakdown Qbd of oxide can be significantly improved by the CAESA process, 相似文献
80.