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61.
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
62.
Schurgers C. Kulkarni G. Srivastava M.B. 《Parallel and Distributed Systems, IEEE Transactions on》2002,13(10):1056-1065
Sensor networks consist of autonomous wireless sensor nodes that are networked together in an ad hoc fashion. The tiny nodes are equipped with substantial processing capabilities, enabling them to combine and compress their sensor data. The aim is to limit the amount of network traffic, and as such conserve the nodes' limited battery energy. However, due to the small packet payload, the MAC header is a significant, and energy-costly, overhead. To remedy this, we propose a novel scheme for a MAC address assignment. The two key features which make our approach unique are the exploitation of spatial address reuse and an encoded representation of the addresses in data packets. To assign the addresses, we develop a purely distributed algorithm that relies solely on local message exchanges. Other salient features of our approach are the ability to handle unidirectional links and the excellent scalability of both the assignment algorithm and address representation. In typical scenarios, the MAC overhead is reduced by a factor of three compared to existing approaches 相似文献
63.
D. G. Kuberkar N. A. Shah M. R. Gonal R. Prasad R. G. Kulkarni 《Journal of Superconductivity》2000,13(1):37-40
It has been reported that, by adding equal amounts of CaO and CuO to non superconducting La3Ba3Cu6O
z
(La-336), a series of superconductors with nominal compositions La3Ca
y
Ba3Cu6+y
O
z
were prepared with maximum Ton
c 80K. Similar studies on addition of CaO and CuO in nonsuperconducting LaBaCu2O
z
(La-112) resulted into superconducting LaCaBaCu3O
z
(La-1113). To date no attempt has been made to synthesize La2CaBa2Cu5O
z
(La-2125) superconducting phase by addition of CaO and CuO to non superconducting La2Ba2Cu4O
z
(La-224) system. Also no reports are published to study the effect of replacing larger La3+-ions (1.01Å) by smaller rare earth ions viz Y3+(0.89Å), Er3+(0.91Å), Gd3+(0.91Å) on the structural and superconducting properties of (La2–x
R
x
)Ba2(Ca
y
Cu4+y
)O
z
(LRBCaC); 0.0 x 0.5; y=2x system. In this paper, we report the method of synthesis, structural and superconducting property characterization using X-ray diffraction, oxygen content measurements using iodometry, resistivity measurements using d.c. four probe technique and a.c. susceptibility measurements in the temperature range RT to 15K. Also a comparative study, on the evolution of superconducting phase with Ca-concentration for different rare earth substitutions for LRBCaC system in the context of hole doping mechanism, is carried out. 相似文献
64.
S. C. Sabharwal Sangeeta Madhumita Goswami S. K. Kulkarni B. D. Padalia 《Journal of Materials Science: Materials in Electronics》2000,11(4):325-329
Beta barium borate (-BBO) crystals have been grown by the top seeded solution growth technique (TSSG) using Na2O as a flux. The crystals exhibited high transparency and the absence of inclusions and found to have sodium contamination in the range 150 to 230 p.p.m. The effect of this contamination on some crystal properties of interest has been investigated. The presence of impurities causes optical absorption below 550 nm in BBO crystals of both and -phases. X-ray photo emission spectroscopy (XPS) measurements performed on these crystals show that sodium gives rise to a measurable shift in the binding energies of the constituent ions. Further, the results show that Na+ ions enter into the lattice substitutionally and provide charge trapping sites close to the band edge. 相似文献
65.
Two new encoding strategies, namely, wedge and twist codes, which are based on the DNA helical parameters, are introduced to represent DNA sequences in artificial neural network (ANN)-based modeling of biological systems. The performance of the new coding strategies has been evaluated by conducting three case studies involving mapping (modeling) and classification applications of ANNs. The proposed coding schemes have been compared rigorously and shown to outperform the existing coding strategies especially in situations wherein limited data are available for building the ANN models. 相似文献
66.
Dafone inhibits the lipid peroxidation significantly in a concentration dependent manner. The inhibition was found to be an uncompetitive type with the inhibition constant (Ki) of 62.5muM On the other hand complexation with metal ions results in a significant reversal from antioxidant to pro-oxidant properties for the resulting complexes which are cationic and with associated halometallate anions. The nature of the potentiation in case of the ferric compound was of competitive type with activation constant (Ka) having the value 32.5muM. The neutral copper-dafonate complex, however, inhibits lipid peroxidation with increase in concentration. 相似文献
67.
Selective flocculation of iron oxide-kaolin mixtures using a modified polyacrylamide flocculant 总被引:1,自引:0,他引:1
S A Ravi Shankar Pradip M G Deo R A Kulkarni S Gundiah 《Bulletin of Materials Science》1988,10(5):423-433
High molecular weight polyacrylamides were synthesized and successfully modified to contain up to 8·3% hydroxamate functional
groups. The selective flocculation tests carried out on 1:1 iron oxide/kaolin mixtures using parent polyacrylamide, polyacrylic
acid and the modified polyacrylamide, confirm the possibility of enhancing selectivity through introduction of iron chelating
functional groups in commercially available polymers. Starting with a feed grade of 35% iron, 92% recovery with acceptable
grade of 60% iron has been achieved using the modified polyacrylamide.
NCL communication No. 4415 相似文献
68.
The structural and electrical properties of the oxidic spinel Zn0·5Cu0·5Fe
x
Cr2−x
O4 (x=0·8, 0·9, 1·0, 1·1) have been investigated through X-ray diffraction, electrical resistivity, and thermoelectric measurements.
X-ray diffraction data showed formation of single spinel phase with cubic structure. D.C. resistivity measurements from room
temperature to 850 K was carried out and activation energy for all the compositions evaluated. Thermoelectric measurements
showedp-type semiconducting nature in all the samples. 相似文献
69.
P. K. Patro R. D. Deshmukh A. R. Kulkarni C. S. Harendranath 《Journal of Electroceramics》2004,13(1-3):479-485
Sr0.5Ba0.5Nb2O6 (SBN50) has been synthesized by coprecipitation method using Sr(NO3)2, Ba(NO3)2 and Nb-oxalate as precursors and ammonium hydroxide as precipitant. Calcination at 1150C resulted in pure SBN50 phase (XRD) and nano powder with size varying between 100–250 nm (TEM). The average grain size (SEM) in the sintered pellets ranged from 2.5 to 5 m as the sintering temperature varied from 1250 to 1350C. The maximum sintered density was observed to be 93% of th. The plot of dielectric constant vs. temperature clearly showed a shift of dielectric maxima (max) with frequency, indicating the relaxor nature of SBN50. The room temperature dielectric constant (RT > 2300) observed for all these samples is higher compared to the earlier reported values (RT 1500). The Tc (for 1 KHz) varied from 47–60C depending on the sintering conditions. The hystersis loops were recorded at various temperatures. The maximum saturation polarization for the unpoled pellets was found to be 2.3 C/cm2 when sintered at 1350C. The improvement in dielectric and ferroelectric behavior is attributed to the enhanced homogeneity attained by the coprecipitation synthesis route used in the present study. Correlations between microstructure (sintering conditions) and dielectric behavior is explored. 相似文献
70.
Kulkarni RG 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2001,48(5):1283-1288
A new technique called sidelobe cancellation technique (SCT) to achieve high stopband rejection in SAW filters is described, for varying requirements of shape factor and sidelobe levels, by using an eigenfunction approach. Cosine series functions with improved sidelobe levels are employed. Each design is characterized by the order of the cosine series and the number of functions used to obtain a particular shape factor and rejection. Limited trimming of shape factor also can be achieved in each design. The filters described here are compared with the Kaiser window filter and are found to be efficient. Measured response of a prototype SAW filter using the approach given in this paper is plotted, and it is in good agreement with the simulated response 相似文献