We demonstrate the resonance wavelength and quality factor dependence of 50nm defect-hole placement within photonic crystal L3 microcavities. Proper placement of defect-holes leads to a 12% increase in photonic crysta...
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ISBN:
(纸本)9781557529107
We demonstrate the resonance wavelength and quality factor dependence of 50nm defect-hole placement within photonic crystal L3 microcavities. Proper placement of defect-holes leads to a 12% increase in photonic crystal sensor detection sensitivity.
There have been reports of improvements in the thermoelectric figure of merit through the use of nanostructured materials to suppress the lattice thermal conductivity. Here, we report on a fundamental study of the com...
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Though not very often, there are some cases in the literature where discrepancies exist in the temperature dependence of elastic constants of materials. A particular example of this case is the behavior of C12 coeffic...
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Though not very often, there are some cases in the literature where discrepancies exist in the temperature dependence of elastic constants of materials. A particular example of this case is the behavior of C12 coefficient of a simple metal, aluminum. In this paper we attempt to provide insight into various contributions to temperature dependence in elastic properties by investigating the thermoelastic properties of fcc aluminum as a function of temperature through the use of two computational techniques and experiments. First, ab initio calculations based on density functional theory (DFT) are used in combination with quasiharmonic theory to calculate the elastic constants at finite temperatures through a strain-free energy approach. Molecular dynamics (MD) calculations using tight-binding potentials are then used to extract the elastic constants through a fluctuation-based formalism. Through this dynamic approach, the different contributions (Born, kinetic, and stress fluctuations) to the elastic constants are isolated and the underlying physical basis for the observed thermally induced softening is elucidated. The two approaches are then used to shed light on the relatively large discrepancies in the reported temperature dependence of the elastic constants of fcc aluminum. Finally, the polycrystalline elastic constants (and their temperature dependence) of fcc aluminum are determined using resonant ultrasound spectroscopy (RUS) and compared to previously published data as well as the atomistic calculations performed in this work.
Topological insulators is a newly discovered class of materials with the Dirac cone type dispersion at the surface and conventional band in the volume of the material. We present results of the study of the low-freque...
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ISBN:
(纸本)9781457701894
Topological insulators is a newly discovered class of materials with the Dirac cone type dispersion at the surface and conventional band in the volume of the material. We present results of the study of the low-frequency excess noise in thin films made of Bi 2 Se 3 topological insulator material. The films were prepared through mechanically cleavage from the bulk crystal via the “graphene-like” exfoliation procedure. We verified the quality and crystallinity of Bi 2 Se 3 samples with the micro-Raman spectroscopy. Our fabricated devices have linear current voltage characteristics in the low bias region with the current fluctuation noise spectral density SI proportional to 1/f for frequency f less than 10 kHz. The noise spectral density SI showed the square law dependence on the source-drain current and changed from about ~10 -22 to 10 -18 A 2 /Hz as current changes form ~10 -7 to 10 -5 A. Our results can be used for understanding electron transport and trap dynamics, and for reducing low-frequency noise in topological insulator devices.
We report in situ infrared measurements of ion-induced reconfiguration and dissociation of bonded hydrogen associated with various defects in silicon at low temperatures. Defect-associated Si-H complexes were prepared...
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We report in situ infrared measurements of ion-induced reconfiguration and dissociation of bonded hydrogen associated with various defects in silicon at low temperatures. Defect-associated Si-H complexes were prepared by low-temperature proton implantation in silicon followed by room-temperature annealing. As a result of subsequent low-temperature He3 ion irradiation, we observed (1) ion-induced dissociation of Si-H complexes, (2) a notable difference in the dissociation rate of interstitial- and vacancy-type defects, and, unexpectedly, (3) the growth of bond-centered hydrogen, which is generally observed in association with low-temperature proton implantation. These findings provide insight into the mechanisms responsible for the dissociation of hydrogen bonds in silicon and thus have important implications for bond-selective nanoscale engineering and the long-term reliability of state-of-the-art silicon semiconductor and photovoltaic devices.
The crystal structure of PrCoO3 has been studied with high-resolution neutron powder diffraction and pair-distribution-function analysis in the temperature range from 12–600 K. The compound has the orthorhombic (Pbnm...
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The crystal structure of PrCoO3 has been studied with high-resolution neutron powder diffraction and pair-distribution-function analysis in the temperature range from 12–600 K. The compound has the orthorhombic (Pbnm) perovskite structure over the entire temperature range. The temperature dependence of the average Co-O bond length shows clear anomalies near 60 K and 200 K where anomalous temperature dependencies of thermal conductivity and magnetic susceptibility have been reported. The data show a constant intermediate-spin-state fraction within 60
X-ray microfluorescence imaging technique has been used as a significant tool in order to investigate minerals contents in some kinds of materials. The aim of this study was to evaluate the elemental distribution of c...
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An optical-coding technique for microfluidic flow cytometers to detect forward scattering and large angle scattering signals that can be used to differentiate beads and cells.
An optical-coding technique for microfluidic flow cytometers to detect forward scattering and large angle scattering signals that can be used to differentiate beads and cells.
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