Spectral analysis of coherent and incoherent phonon transport in silicon nanomeshes

HR Cui and T Maranets and TF Ma and Y Wang, PHYSICAL REVIEW B, 110, 075301 (2024).

DOI: 10.1103/PhysRevB.110.075301

In this paper, we investigate the spectral thermal transport properties of silicon nanomeshes (SNMs) with large and small holes arranged periodically, aperiodically in the x direction (ap-x), and fully aperiodically (ap-xy). Our simulations reveal a significant reduction in thermal conductivity (kappa) of small-hole SNMs due to ap-x aperiodicity, in contrast with large-hole SNMs. Spectral phonon analysis indicates that low-frequency phonons in small-hole SNMs are notably suppressed by ap-x aperiodicity, like one-dimensional superlattices. Spectral energy density analysis shows the existence of well-defined coherent phonon modes in small-hole SNMs in the 0-3 THz range; spectral thermal conductivity analysis shows that these modes transport ballistically in the SNM. In contrast, ap-x aperiodicity has negligible impact on large-hole SNMs, attributed to hindered coherent phonon formation. Surprisingly, low-frequency phonons in small-hole SNMs demonstrate enhanced heat transfer capabilities compared with large-hole counterparts, highlighting coherent phonon behavior. Finally, while the heat flux splitting and shape factors effectively categorize kappa for large-hole SNMs, their utility is limited for small-hole SNMs, emphasizing the importance of coherent phonon considerations in thermal transport analysis.

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