Thermal conductivity of surface phonon polaritons in SiC elliptical nanofibers

Abstract Surface phonon polaritons (SPhPs) in polar dielectric are considered to be a class of potential efficient heat carriers for heat dissipation in micro electric devices, due to their high contribution to the thermal conductivity. In this work, the contribution of SPhPs to the thermal conductivity of a fiber with a general elliptical cross-section area was studied. The effects of cross-sectional size and shape of the SiC elliptical nanofibers were investigated. A method for analytically solving the dispersion relation of SPhPs in elliptical fibers was firstly presented, based on which the contribution of SPhPs to the thermal conductivity was further analyzed. It was found that the SPhP-contributed thermal conductance of a SiC nanofiber with an equivalent diameter of 19.4 nm is about 51.2 pW·K −1 , which is comparable to that contributed by phonons. Importantly, this value is also comparable to that reported for nanofilms. For eccentrics being smaller than 0.6, the effect of the eccentricity can be neglected, and there is a power-function relationship between the thermal conductivity and the equivalent diameter, i. e. <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi mathvariant="italic">λ</mml:mi> <mml:mo>~</mml:mo> <mml:msup> <mml:mrow> <mml:mi>d</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mi>α</mml:mi> </mml:mrow> </mml:msup> </mml:math> , <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>α</mml:mi> <mml:mo>=</mml:mo> <mml:mn>1.222</mml:mn> </mml:math> . When the eccentricity becomes larger than 0.6, the thermal conductivity increases rapidly because the geometry approaches the one of a film. This study shows a great potential of utilizing SPhPs in nanofibers as effective carriers for heat dissipation.