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排序方式: 共有548条查询结果,搜索用时 15 毫秒
31.
S. S. Hullavarad R. D. Vispute B. Nagaraj V. N. Kulkarni S. Dhar T. Venkatesan K. A. Jones M. Derenge T. Zheleva M. H. Ervin A. Lelis C. J. Scozzie D. Habersat A. E. Wickenden L. J. Currano M. Dubey 《Journal of Electronic Materials》2006,35(4):777-794
In this paper we report recent advances in pulsed-laser-deposited AIN thin films for high-temperature capping of SiC, passivation
of SiC-based devices, and fabrication of a piezoelectric MEMS/NEMS resonator on Pt-metallized SiO2/Si. The AlN films grown using the reactive laser ablation technique were found to be highly stoichiometric, dense with an
optical band gap of 6.2 eV, and with a surface smoothness of less than 1 nm. A low-temperature buffer-layer approach was used
to reduce the lattice and thermal mismatch strains. The dependence of the quality of AlN thin films and its characteristics
as a function of processing parameters are discussed. Due to high crystallinity, near-perfect stoichiometry, and high packing
density, pulsed-laser-deposited AlN thin films show a tendency to withstand high temperatures up to 1600°C, and which enables
it to be used as an anneal capping layer for SiC wafers for removing ion-implantation damage and dopant activation. The laser-deposited
AlN thin films show conformal coverage on SiC-based devices and exhibit an electrical break-down strength of 1.66 MV/cm up
to 350°C when used as an insulator in Ni/AlN/SiC metal-insulator-semiconductor (MIS) devices. Pulsed laser deposition (PLD)
AlN films grown on Pt/SiO2/Si (100) substrates for radio-frequency microelectrical and mechanical systems and nanoelectrical and mechanical systems
(MEMS and NEMS) demonstrated resonators having high Q values ranging from 8,000 to 17,000 in the frequency range of 2.5–0.45
MHz. AlN thin films were characterized by x-ray diffraction, Rutherford backscattering spectrometry (in normal and oxygen
resonance mode), atomic force microscopy, ultraviolet (UV)-visible spectroscopy, and scanning electron microscopy. Applications
exploiting characteristics of high bandgap, high bond strength, excellent piezoelectric characteristics, extremely high chemical
inertness, high electrical resistivity, high breakdown strength, and high thermal stability of the pulsed-laser-deposited
thin films have been discussed in the context of emerging developments of SiC power devices, for high-temperature electronics,
and for radio frequency (RF) MEMS. 相似文献
32.
RE Howells CW Redman KK Dhar P Sarhanis C Musgrove PW Jones J Alldersea AA Fryer PR Hoban RC Strange 《Canadian Metallurgical Quarterly》1998,4(10):2439-2445
Epithelial ovarian cancer is generally associated with a poor outcome, although the mechanisms that determine survival and progression-free interval (PFI) are unclear. Data from ovarian tumors showing associations between (a) null genotypes at the glutathione S-transferase GSTM1 and GSTT1 loci and expression of p53 protein and (b) outcome and expression of p53 suggest that polymorphism at these loci is a factor determining outcome. Accordingly, we have studied the association between the GSTM1 null and GSTT1 null genotypes and survival and PFI in 148 women with epithelial ovarian cancer. Although we did not find an association between individual genotypes and outcome, women with both GSTM1 null and GSTT1 null genotypes demonstrated poorer survival (P = 0.001) and reduced PFI (P = 0.003). Thus, no cases with both these genotypes survived past 42 months postdiagnosis. In contrast, 43% of the women without this combination survived beyond this time. Because response to chemotherapy is a major factor determining outcome in ovarian cancer, we also examined the data for associations between the glutathione S-transferase genotypes and response to such treatment. Thus, in 78 patients treated with chemotherapy, the combination of GSTM1 null and GSTT1 null was associated with unresponsiveness to primary chemotherapy (P = 0.004); none of the eight patients with both these genotypes responded, compared with 38 of 70 (54%) of patients with other genotype combinations. The effect of the combination of genotypes on survival and PFI was lost in a multivariate model that included response to chemotherapy as a confounding factor. This suggests that the combination of GSTM1 null/GSTT1 null is associated with outcome because of its influence on response to chemotherapy. These preliminary findings may provide a basis for the selection of patients for treatment with chemotherapeutic agents. 相似文献
33.
D Dhar 《Bulletin of Materials Science》1984,6(4):817-822
An elementary introduction to the concept of fractals is given. Some examples of fractals drawn from nature are briefly discussed.
It is suggested that fractal geometry may be useful in characterizing the grain size and shape distributions in polycrystalline
solids. 相似文献
34.
Granulomas and cholestatic--hepatocellular injury associated with phenylbutazone. Report of two cases 总被引:1,自引:0,他引:1
A combined cholestatic-hepatocellular injury and noncaseating granulomas occurred in two patients 1 and 4 weeks after phenylbutazone therapy. Both patients were jaundiced, one had a macular rash, and both had peripheral blood eosinophilia. Symptoms and signs subsided, and abnormal findings from tests of hepatic function rapidly returned to normal following withdrawal of the drug. Sections of liver biopsy specimens 6 months later showed no granulomas or other pathologic changes. Previously reported cases are reviewed. 相似文献
35.
The growth and microstructure of Cd1–x
Zn
x
S films were studied by depositing the films on to freshly cleaved NaCl, KCl, and LiF substrates at various x values (0相似文献
36.
C. B. Samantaray A. Dhar D. Bhattacharya M. L. Mukherjee S. K. Ray 《Journal of Materials Science: Materials in Electronics》2001,12(7):365-370
The effect of post-deposition annealing on the structural and optical properties of barium strontium titanate, Ba0.8Sr0.2TiO3 film has been investigated. The films have been deposited on oxidized p-silicon substrates by r.f. magnetron sputtering followed by annealing in O2 atmosphere at different temperatures. In situ deposition has also been carried out at 550 °C for comparison. The nature of the variation of refractive index and extinction coefficient with annealing temperature and wavelength has been studied. Absorption band edges shift towards lower photon energy values as the temperature is increased causing a reduction in the optical band gap energy. Infrared absorption bands show a cubic symmetry at lower frequency and are found to be broadened and even split at higher frequency. 相似文献
37.
Alberto Mazzoldi Mario Tesconi Alessandro Tognetti Walter Rocchia Giovanni Vozzi Giovanni Pioggia Arti Ahluwalia Danilo De Rossi 《Materials science & engineering. C, Materials for biological applications》2008,28(7):1057-1064
Carbon nanotube (NT) actuators were fabricated using the micromolding method. In order to prevent the nanotubes from aggregating, they were enclosed in a partially cross-linked polyvinylalcohol–polyallylamine matrix. A unimorph matrix bender in the form of a small multi-layered strip, 5 mm × 15 mm was fabricated. The resulting composite system: NT/PVA, solid polymer electrolyte and metal contact, was characterised using impedance analysis and cyclic voltammetry. Initial measurements on electro-mechanical transduction show a conversion efficiency of 0.2 μm/mV. An electrochemical model of the impedance of the system was then developed, with which the experimental results agree fairly well. 相似文献
38.
39.
Priyalal Wijewarnasuriya Yuanping Chen Greg Brill Nibir Dhar David Benson Lucia Bubulac Dennis Edwall 《Journal of Electronic Materials》2010,39(7):1110-1117
We have performed a detailed study of dark current versus voltage to understand existing limitations in dark current and address
the nonuniformity of dark current in devices fabricated on HgCdTe grown on silicon substrates. One interesting observation
is that trap-assisted tunneling, g-r currents, are not found close to zero bias in certain devices. Devices from the low end
of the R
0
A distribution show heavy shunting paths close to zero bias. We believe that these shunting paths may be the limiting cause
of tail distributions in fabricated focal plane array tail distributions. Possible causes for these shunting paths are surface
charges associated with dislocation cores and impurity gettering at dislocation cores. The measured non-anti-reflection (AR)-coated
quantum efficiency (QE) was 0.576 at 78 K and displays the classical response versus wavelength. The measured QE on isolated
single devices is consistent with the 256 × 256 focal-plane array mean QE. Obtained average dark currents are on the order
of mid 10−5 A cm–2, which is one order of magnitude higher than dark currents obtained from arrays on lattice-matched substrates. On average,
arrays on lattice-mismatched substrates show performance characteristics inferior to those of arrays fabricated on lattice-matched
substrates. This inferior performance is due to array pixel operability, as can be seen from the tail of the distribution
and the average dark currents, which are one order of magnitude higher than those obtained on lattice-matched substrates. 相似文献
40.
Manav R. Bhatnagar M. K. Arti Are Hjørungnes Ranjan Bose Lingyang Song 《Wireless Personal Communications》2010,54(1):69-81
In this paper, we propose high-rate space–time coding for cooperative wireless networks to reduce the overall delay incurred
in relaying signals to multiple receivers. The relay structure is optimized in order to achieve maximum SNR at the receiver
nodes. The proposed scheme provides a significant reduction in the delay required for the relaying and transmission of the
signals to the multiple receivers with a minute loss in performance. We have also shown by simulation that this loss in the
performance could be recovered by selecting more number of relays. We propose two relaying strategies for high-rate space–time
codes, which are very useful in providing high data-rate in wireless cooperative networks. 相似文献