Phonon mean free path analysis in polycrystalline nanostructured thin films

초록

The phonon mean free path in polycrystalline nanostructured thin films was investigated. To simultaneously analyze the values in each direction of the anisotropic structures of the thin films, a novel phonon transport simulation method was developed by integrating the two existing methods. This combined phonon transport simulation valuated the mean free path in the modeled polycrystalline nanostructured thin films. The results indicate that the mean free path in both the in-plane and cross-plane directions increases as the grain size becomes nonuniform. Furthermore, we found that the mean free path in the polycrystalline nanostructured thin films can be predicted from bulk polycrystalline nanostructure and theoretical solutions for plain thin films, regardless of the grain size uniformity. Coupled with another finding that grain-shape-based descriptors correlate quantitatively with the mean free path in bulk polycrystalline nanostructures, it is concluded that the mean free path in polycrystalline nanostructured thin films can be predicted without the need to implement phonon transport simulations. © 2024 Elsevier Ltd

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