Surface scattering controlled heat conduction in semiconductor thin films

Phonon-surface scattering is the fundamental mechanism behind thermal transport phenomena at the nanoscale. Despite its significance, typical approaches to describe the interaction of phonons with surfaces do not consider all relevant physical quantities involved in the phonon-surface interaction, n...

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Veröffentlicht in:Journal of applied physics 2016-11, Vol.120 (20)
Hauptverfasser: Malhotra, Abhinav, Maldovan, Martin
Format: Artikel
Sprache:eng
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Zusammenfassung:Phonon-surface scattering is the fundamental mechanism behind thermal transport phenomena at the nanoscale. Despite its significance, typical approaches to describe the interaction of phonons with surfaces do not consider all relevant physical quantities involved in the phonon-surface interaction, namely, phonon momentum, incident angle, surface roughness, and correlation length. Here, we predict thermal conduction properties of thin films by considering an accurate description of phonon-surface scattering effects based on the rigorous Beckmann-Kirchhoff scattering theory extended with surface shadowing. We utilize a Boltzmann transport based reduced mean-free-path model for phonon transport in thin-films to predict the wavelength and mean-free-path heat spectra in Si and SiGe films for different surface conditions and show how the thermal energy distribution can be tailored by the surface properties. Using the predicted wavelength spectra, we also introduce a measure to quantify phonon-confinement effects and show an enhanced confinement in Ge alloyed Si thin films. The impact of surface roughness and correlation lengths on thermal conductivities is also studied, and our numerical predictions show excellent agreement with experimental measurements. The results allow to elucidate and quantitatively predict the amount of thermal energy carried by different phonons at the nanoscale, which can be used to design improved optoelectronic and thermoelectric devices.
ISSN:0021-8979
1089-7550
DOI:10.1063/1.4968542