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ISSN Online: 2377-424X

ISBN Print: 978-1-56700-421-2

International Heat Transfer Conference 15
August, 10-15, 2014, Kyoto, Japan

In-Plane Thermal Conductivity of Si Thin Films from First-Principles Calculation

Get access (open in a dialog) DOI: 10.1615/IHTC15.ppe.009064
pages 7015-7034

Resumo

It is well-known that thermal conductivities along thin films are generally lower than the bulk values. Precedent studies on the in-plane thermal transport in thin films mainly focused on the phonon boundary scattering and often neglected the variation in the phonon-phonon scattering. However, when thin film thickness decreases, the number of mutually interacting phonons decreases and so does the scattering rate. Based on the first-principles calculations and lattice dynamics theory and only taking into account the available modes in thin films, the in-plane thermal conductivities of Si thin films have been systematically investigated. The contributions of individual thin-film phonon modes to the thermal transport in thin films under different temperatures have been studied and the dependence of phonon-phonon scattering on the thin film thickness has been clarified. Since the boundary scattering tends to lower the thermal conductivity while the expurgation of some interphonon scattering processes can enhance the thermal transport, the relative strength of these two mechanisms in determining the thermal transport in thin films has also been discussed. Besides, the effect of surface roughness is also taken into account by adopting a reflectivity that depends on surface roughness and phonon wavelength. Free from any fitting parameters and less dependent on the potentials chosen, our calculation can simulate heat transport in extremely thin films or under low temperature limit.