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Spectrally Resolved Specular Reflections of Thermal Phonons from Atomically Rough Surfaces

Ravichandran, Navaneetha K. and Zhang, Hang and Minnich, Austin J. (2018) Spectrally Resolved Specular Reflections of Thermal Phonons from Atomically Rough Surfaces. Physical Review X, 8 (4). Art. No. 041004. ISSN 2160-3308. doi:10.1103/physrevx.8.041004.

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The reflection of waves from rough surfaces is a fundamental process that plays a role in diverse fields such as optics, acoustics, and seismology. While a quantitative understanding of the reflection process has long been established for many types of waves, the precise manner in which thermal phonons of specific wavelengths reflect from atomically rough surfaces remains unclear owing to limited control over terahertz-frequency phonon generation and detection. Knowledge of these processes is critical for many applications, however, and is particularly important for recent attempts to create novel materials by coherently interfering thermal phonons. Here, we report measurements of a key property for these efforts, the phonon-wavelength-dependent specularity parameter, which describes the probability of specular reflections of thermal phonons at a surface. Our experiments show evidence of specular surface reflections of terahertz thermal phonons in our samples around room temperature and indicate a sensitivity of these reflections to surface imperfections on the scale of just 2–3 atomic planes. Our work demonstrates a general route to probe the microscopic interactions of thermal phonons with surfaces that are typically inaccessible with traditional experiments.

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Minnich, Austin J.0000-0002-9671-9540
Additional Information:© 2018 the Author(s). Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. (Received 22 March 2018; revised manuscript received 13 September 2018; published 5 October 2018) his work was supported by the National Science Foundation under Grant No. CBET CAREER 1254213. The authors thank A. A. Maznev and K. A. Nelson for fruitful discussions about the TG experiment and L. Lindsay for providing the ab initio phonon properties. N. K. R. thanks the Resnick Sustainability Institute at Caltech and the Dow Chemical Company for fellowship support. A. J. M. and N. K. R. originated the research. H. Z. and N. K. R. fabricated the silicon membrane samples. N. K. R. conducted the TG experiments and performed the BTE and the Bayesian inference calculations. N. K. R. performed the TEM imaging with help from Carol Garland at the Kavli Nanoscience Institute at Caltech. N. K. R. and A. J. M. analyzed the results and prepared the manuscript. All authors studied and commented on the manuscript. The authors declare no competing financial interests.
Group:Resnick Sustainability Institute, Kavli Nanoscience Institute
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Resnick Sustainability InstituteUNSPECIFIED
Dow Chemical CompanyUNSPECIFIED
Issue or Number:4
Record Number:CaltechAUTHORS:20181005-141404733
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:90144
Deposited By: George Porter
Deposited On:05 Oct 2018 23:25
Last Modified:16 Nov 2021 00:41

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