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Thermal Conductivity Reduction in a Nanophononic Metamaterial versus a Nanophononic Crystal: A Review and Comparative Analysis
Author(s) -
Hussein Mahmoud I.,
Tsai ChiaNien,
Honarvar Hossein
Publication year - 2020
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.201906718
Subject(s) - metamaterial , materials science , thermal conductivity , phonon , silicon , thermoelectric materials , thermoelectric effect , scattering , optoelectronics , reduction (mathematics) , phonon scattering , condensed matter physics , mean free path , nanotechnology , optics , composite material , physics , thermodynamics , geometry , mathematics
Abstract The notion of a locally resonant metamaterial—widely applied to light and sound—has recently been introduced to heat, whereby the thermal conductivity is reduced primarily by intrinsic localized atomic vibrations rather than scattering mechanisms. This article reviews and analyzes this new emerging concept, termed nanophononic metamaterial (NPM), and contrasts it with the competing concept of a nanophononic crystal (NPC) in which thermal conductivity reduction is realized primarily via nanoscale Bragg scattering. Both the NPM and NPC core mechanisms require the presence of a sufficient level of wave behavior, which is possible when there is a relatively wide distribution of the phonon mean free path (MFP). Silicon serves as a perfect material to form NPMs and NPCs given its relatively large average phonon MFP. This offers a unique opportunity considering silicon's abundance and mature fabrication technology. It is shown in this comparative study that while both the NPM and NPC nanosystems may be rendered to serve as extreme insulators of heat, an NPM may do so without excessive reduction in the minimum feature size–which is key to keeping the electrical properties intact. This trait makes a silicon‐based NPM poised to serve as a low‐cost thermoelectric material with exceptional performance.