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Multiple phonon processes contributing to inelastic scattering during thermal boundary conductance at solid interfaces

Journal of Applied Physics

Hopkins, Patrick E.

A new model is developed that accounts for multiple phonon processes on interface transmission between two solids. By considering conservation of energy and phonon population, the decay of a high energy phonon in one material into several lower energy phonons in another material is modeled assuming diffuse scattering. The individual contributions of each of the higher order inelastic phonon processes to thermal boundary conductance are calculated and compared to the elastic contribution. The overall thermal boundary conductance from elastic and inelastic (three or more phonon processes) scattering is calculated and compared to experimental data on five different interfaces. Improvement in value and trend is observed by taking into account multiple phonon inelastic scattering. Three phonon interfacial processes are predicted to dominate the inelastic contribution to thermal boundary conductance. © 2009 American Institute of Physics.

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Thermal conductivity measurements on polycrystalline silicon microbridges using the 3ω technique

Journal of Heat Transfer

Hopkins, Patrick E.; Phinney, Leslie M.

The thermal performance of microelectromechanical systems devices is governed by the structure and composition of the constituent materials as well as the geometrical design. With the continued reduction in the characteristic sizes of these devices, experimental determination of the thermal properties becomes more difficult. In this study, the thermal conductivity of polycrystalline silicon (polysilicon) microbridges are measured with the transient 3ω technique and compared with measurements on the same structures using a steady state Joule heating technique. The microbridges with lengths from 200 μm to 500 μm were designed and fabricated using the Sandia National Laboratories SUMMiT V™ surface micromachining process. The advantages and disadvantages of the two experimental methods are examined for suspended microbridge geometries. The differences between the two measurements, which arise from the geometry of the test structures and electrical contacts, are explained by bond pad heating and thermal resistance effects. Copyright © 2009 by ASME.

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Results 51–60 of 60
Results 51–60 of 60