Massive reduction in thermal conductivity of silicon irradiated with silicon ions – Paper Published in Physical Review Materials – Congrats Ethan Scott!

Congratulations to Ethan Scott who recently published his paper on “Phonon scattering effects from point and extended defects on thermal conductivity studied via ion irradiation of crystals with self-impurities,” in Physical Review Materials (Scott, E. A., Hattar, K., Rost, C.M., Gaskins, J.T., Fazli, M., Ganski, C., Li, C., Bai, T., Wang, Y., Esfarjani, K., Goorsky, M., Hopkins, P.E., “Phonon-strain scattering effects from point and extended defects on thermal conductivity studied via ion irradiation of crystals with self-impurities,” Physical Review Materials 2, 095001 (2018). PDF).



Fundamental theories predict that reductions in thermal conductivity from point and extended defects can arise due to phonon scattering with localized strain fields. To experimentally determine how these strain fields impact phonon scattering mechanisms, we employ ion irradiation as a controlled means of introducing strain and assorted defects into the lattice. In particular, we observe the reduction in thermal conductivity of intrinsic natural silicon after self-irradiation with two different silicon isotopes, 28Si+ and 29Si+. Irradiating with an isotope with a nearly identical atomic mass as the majority of the host lattice produces a damage profile lacking mass impurities and allows us to assess the role of phonon scattering with local strain fields on the thermal conductivity. Our results demonstrate that point defects will decrease the thermal conductivity more so than spatially extended defect structures assuming the same volumetric defect concentrations due to the larger strain per defect that arises in spatially separated point defects. With thermal conductivity models using density functional theory, we show that for a given defect concentration, the type of defect (i.e., point vs extended) plays a negligible role in reducing the thermal conductivity compared to the strain per defect in a given volume.

DOI: 10.1103/PhysRevMaterials.2.095001


This material is based upon work supported by the Air Force Office of Scientific Research under award number FA9550-18-1-0352. The authors would like to thank D. Buller and R. Sisson with their assistance with the implantation, as well as the Nuclear Regulatory Commission for their support of this research through the Jump Start in Nuclear Materials Education and Research Graduate Fellowship Program at the University of Virginia. We also appreciate support from the Office of Naval Research under a MURI program, Grant No. N00014-18-1-2429. This work was performed, in part, at the Center for Integrated Nanotechnologies, an Office of Science User Facility operated for the U.S. Department of Energy (DOE) Office of Science. Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. DOE’s National Nuclear Security Administration under contract DE-NA-0003525. The views expressed in the article do not necessarily represent the views of the U.S. DOE or the United States Government.


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