Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 24 for “"boundary scattering"”.
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Modeling the thermoelectric properties of bulk and nanocomposite thermoelectric materials
… due to their random nature and unknown grain boundary scattering mechanisms. In this thesis we introduce new models for phonon and electron transport in nanocomposites. For phonon modeling we develop an analytical formula for the phonon thermal conductivity using the effective medium …
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Electrical and thermal transport in 2- and 3-dimensional periodic holey silicon
… It has been conclusively demonstrated that boundary scattering in nanostructured silicon e ectively reduces thermal transport, resulting in an enhanced thermoelectric Figure of merit ZT. However, claims of high ZT are quantitatively misleading since electrical and thermal properties are …
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Experimental study of thermal conductivity reduction of silicon-germanium nanocomposite for thermoelastic application
… the thermal conductivity by increasing phonon boundary scattering at interfaces. In the first method, SiGe alloys were annealed at a temperature higher than the melting point to increase the number of grain boundaries. In the second method, SiGe composites were made with nanosize silicon …
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Theory, Fabrication and Characterization of Micromachined Electrolytic Solution Conductivity Sensors
… than the bulk material due to free electron boundary scattering. Four-wire resistance measurements are used to eliminate the effect of lead resistance for the RTD fabricated on the probe tip. The RTD integrated on the probe tip achieved an accuracy of +/-0.5% from 0 to 100°C with a …
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Influence of Structural Relaxation Upon the Low Temperature Properties of Metallic Glasses
… We have found no effect upon (kappa)(,ph) due to boundary scattering in our samples. We have deduced the "glassy" thermal conductivity (kappa)(,glass) for Zr(,3)Rh and PdSiCu from our measurements, where 1/(kappa)(,glass) is the thermal resistivity intrinsic to the disordered state of the solid.
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Theoretical investigation of thermoelectric properties of bulk and nano-scaled semiconductors
… a system due to a significant increase in boundary scattering. It will be well shown that the thermal conductivity of nanoscale semiconductors significantly decreases compared to that of bulk semiconductors. Considering an enhancement of ZT, a decrease in thermal conductivity is a …
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Scanned pulsed laser annealing of Cu thin films
… could be used to quantify the effects of grain boundary scattering and the role of crystallographic orientation in interfacial electromigration. Earlier research on scanned continuous laser annealing suggested that control of the thermal gradient would lead to an improved ability to manipulate …
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Electronic properties of Bi nanowaves
… band structure and considering the wire boundary and grain boundary scattering not present in bulk bismuth.
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Semiclassical approaches to Quantal Andreev Billiards and Other Topics in Inhomogeneous Superconductivity
… periodic orbits that creep around the billiard boundary. The second involves quasiparticle motion near an extended impurity in a d-wave superconductor. Via an extension of the quasiclassical approximation, the idea that sign-variations in the superconducting pair-potential lead to low-energy …
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Phonon scattering from substitutional impurities and lattice defects in silver chloride
… of this investigation was to study phonon scattering by substitutional impurities and lattice defects in silver chloride crystals by means of the thermal conductivity technique. In addition, far infrared absorption measurements were made on some of the doped crystals. The thermal …
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Effect of phonon transport on the Seebeck coefficient and thermal conductivity of silicon nanowire arrays
… that has been attributed to the increased scattering of heat conducting phonons from the surface disorder introduced by etching. The reduction is below the incoherent limit for phonon scattering at the boundary, the so-called Casimir limit. A new model of partially coherent phonon transport …
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Spectroscopic surface scattering of confined acoustic phonons in silicon nanostructures
… silicon membranes and nanowires. Surface scattering dominates intrinsic Akhiezer damping at frequencies > 60 GHz, thereby enabling us to probe phonon-boundary interactions over wavelengths ∼ 42 - 140 nm. To quantitatively understand the dependence of boundary scattering on RMS roughness …
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Optical transient grating measurements of micro/nanoscale thermal transport and mechanical properties
… membrane indicate the breakdown of the diffuse boundary scattering approximation. The transient grating technique was used to generate surface acoustic waves and measure their dispersion in a monolayer of 0.5 - 1 [mu]m diameter silica spheres. The measured dispersion curves show "avoided …
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Reliability, power dissipation, sensing, and thermal transport in carbon nanomaterials and devices
… is limited by substrate phonon and grain boundary scattering, but can be significantly enhanced by transferring subsequent layers of CVD graphene. Overall, the research summarized in this dissertation represents a significant advancement in the understanding of the reliability and …
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Zinc oxide nanowire field effect transistors for sensor applications
… of larger grains and thus reduction in the grain-boundary scattering. Six volatile organic compounds (VOCs) were sensed at room temperature using the direct-write EBL fabricated ZnO devices under UV sensitisation. As the surface-to-volume ratio increases with the decreasing channel width (from 50 …
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Electrical Transport and Scattering Mechanisms in Thin Silver Films for Thermally Insulating Glazing
… conductive behavior originates from electron scattering at interfaces (Fuchs-Sondheimer model) or grain boundaries (Mayadas-Shatzkes model). To achieve a fundamental understanding of the prevailing electron scattering mechanisms, aluminum-doped zinc oxide (ZnO:Al) / Ag / ZnO:Al layer stacks …
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Phonon scattering from substitutional impurities and lattice defects in cadmium sulfide
… in HC1 gives a ""perfectly rough"" surface for boundary scattering of phonons. A theoretical analysis utilizing the Debye thermal conductivity integral was successfully applied to the data for the pure crystal. Coefficients derived from computer fits to the data agree with those calculated from …
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Photodetection using ultrathin metal films
… lengths > 15 nm, currently limited by grain boundary scattering. Further, our density functional theory analysis shows that the addition of small amounts of Au to the Ag lattice significantly enhances the hot hole generation rate.
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Exploring electron and phonon transport at the nanoscale for thermoelectric energy conversion
… transport equation (BTE) and a new grain boundary scattering model to understand how thermoelectric properties are affected in nanocomposites, as well as to identify strategies which could lead to more efficient materials. The second portion of the thesis focuses on determining how to more …
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