General effective medium model for phonon heat flow in highly confined semiconductor nanosystems

Brendan McBennett; Albert Beardo; Emma E. Nelson; Baowen Li; Henry C. Kaptyen; Margaret M. Murnane; Joshua L. Knobloch

doi:10.1117/12.2670522

27 April 2023 General effective medium model for phonon heat flow in highly confined semiconductor nanosystems

Brendan McBennett, Albert Beardo, Emma E. Nelson, Baowen Li, Henry C. Kaptyen, Margaret M. Murnane, Joshua L. Knobloch

Proceedings Volume 12496, Metrology, Inspection, and Process Control XXXVII; 124963P (2023) https://doi.org/10.1117/12.2670522
Event: SPIE Advanced Lithography + Patterning, 2023, San Jose, California, United States

Conference Poster

Abstract

Nanostructured semiconductors can exhibit thermal properties unachievable in bulk systems and will play a crucial role in next-generation nanoelectronics and energy efficient devices, where heat evacuation poses a critical limitation. However, first principles models are too computationally challenging for 3D nanostructured geometries, while ballistic phonon descriptions make overly-simplistic assumptions about the nature of phonon-boundary interactions. Here, we study heat flow in a 3D nanostructured silicon metalattice of <<100nm feature size, using an infrared pump laser to excite the sample and an extreme ultraviolet probe to monitor its relaxation. Analyzing surface acoustic waves launched by metallic gratings fabricated on the sample surface, we nondestructively extract the metalattice’s elastic properties and porosity, validated by electron tomography, which are required parameters to model the heat flow. With the same measurement, we observe the heat flow dynamics to exhibit a Fourier-like behavior with an ultra-low apparent thermal conductivity. Through an analogy to rarefied gas flow in porous media, we explain this and similar measurements of phonon transport in silicon nanomeshes, porous nanowires and nanowire networks. We separate the geometry-dependent permeability contribution to thermal conduction from an intrinsic viscous component, which scales universally with porosity across all systems where feature sizes are much smaller than the dominant phonon mean free paths. This leads to an analytic description of thermal conduction in highly-confined silicon nanosystems, enabling their representation as effective media in engineering applications.

Citation Download Citation

Brendan McBennett, Albert Beardo, Emma E. Nelson, Baowen Li, Henry C. Kaptyen, Margaret M. Murnane, and Joshua L. Knobloch "General effective medium model for phonon heat flow in highly confined semiconductor nanosystems", Proc. SPIE 12496, Metrology, Inspection, and Process Control XXXVII, 124963P (27 April 2023); https://doi.org/10.1117/12.2670522

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