Abstract
We predict the cross-plane phonon thermal conductivity of Stillinger-Weber silicon thin films as thin as 17.4 nm using the lattice Boltzmann method. The thin films are modeled using bulk phonon properties obtained from harmonic and anharmonic lattice dynamics calculations. We use this approach, which considers all of the phonons in the first Brillouin-zone, to assess the suitability of common assumptions. Specifically, we assess the validity of: (i) neglecting the contributions of optical modes, (ii) the isotropic approximation, (iii) assuming an averaged bulk mean-free path, and (iv) the Matthiessen rule. Because the frequency-dependent contributions to thermal conductivity change as the film thickness is reduced, assumptions that are valid for bulk are not necessarily valid for thin films.
Highlights
Thermal transport in microstructured and nanostructured materials can be significantly different than in bulk
We show that because the frequencydependent contributions to thermal conductivity change as the film thickness is reduced, approximations that are valid for bulk are not necessarily valid for thin films
The smallest film thickness we investigate is 17.4 nm, where we expect that the bulk phonon properties can be combined with a suitable boundary scattering model to accurately model the thermal transport
Summary
Thermal transport in microstructured and nanostructured materials can be significantly different than in bulk. Boundary effects become significant and properties predicted for the bulk phasee.g., thermal conductivity, phonon relaxation timesmay not be suitable for modeling thermal transport. The Matthiessen rule, which assumes that different scattering mechanisms are independent. By investigating these approximations, we willidetermine when they can be used to predict the phonon properties and thermal conductivity of bulk systems without introducing significant error, andiiunderstand how their validity changes as system lengths are reduced from bulk to the nanometer scale. We show that because the frequencydependent contributions to thermal conductivity change as the film thickness is reduced, approximations that are valid for bulk are not necessarily valid for thin films
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
