Revisiting thermal conductivity and interface conductance at the nanoscale

Dollfus

et al. 2021

Preprint

A Full Band Monte Carlo simulatorhas been developed to considerphonon transmission across interfaces disposedperpendicularlyto the heat flux. This solver of the Boltzmann transport equation does not require any assumption on the shape the phonon distribution and can naturally consider all phonon transport regimes from the diffusive to the fully ballistic regime. This simulatoris used to study single and double Si/Ge heterostructures from the micrometer scale downto the nanometer scale,i.e. in all phonon transport regime from fully diffusive toballistic.A methodology to determine the thermal conductivity atthermal interfaces is presented.

Section: Ii1 Definitions Based On Semi-spherical Temperature Conceptsupporting

confidence: 59%

Section: Ii1 Definitions Based On Semi-spherical Temperature Conceptmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Study of Phonon Transport Across Si/Ge Interfaces Using Full-Band Phonon Monte Carlo Simulation

Dollfus

et al. 2021

Preprint

“…As detailed in Ref. [13], the hemispherical temperatures T + and T − are defined, even in out-of-equilibrium conditions, as the temperature of phonon sub-populations with a positive/negative (oriented toward the cold/hot thermostat, respectively) giving the same energy density E as that obtained from an equilibrium distribution. Thus, it satisfies the following relationship:…”

Section: Thermal Parametersmentioning

confidence: 99%

“…Where Ω is the volume of the considered reciprocal space f BE is the Bose-Einstein distribution function and 𝜔 s the phonon angular frequency of state s. These temperatures are instrumental to work out a realistic value of the interface conductance G int in heterostructures [13] :…”

Section: Thermal Parametersmentioning

confidence: 99%

Spectral Simulation of Heat Transfer Across Polytype Interfaces

Izitounene

Crystal Research and Technology

et al. 2022

Polytype nanowires fabricated in both silicon and germanium are particularly attractive for thermoelectric engineering. In this work, the transport of phonons across polytype heterojunctions such as Si 3C/Si 2H and Ge 3C/Ge 2H is theoretically studied by using a particle Monte Carlo simulation for phonons. Full‐Band dispersions and phonon‐phonon scattering rates are calculated by using the density‐functional theory. Phonon transmission across interfaces is implemented by using a Full‐Band version of the Diffusive Mismatch Model. First, the different transport regimes (diffusive, ballistic, and intermediate) for homogenous 3C and 2H Si and Ge bars are investigated by using the Knudsen number as well as the spectral contributions of the thermal flux. Then, single and double polytype Si and Ge heterostructures are studied. The variation of the interface thermal conductance as a function of the geometric dimension as well as the effects of the spectral distribution of the flux are investigated. This local indicator of the phonon transport regime can be used as a local indicator of the occurrence of the out of equilibrium transport regime. Finally, it is shown that the polytype interfaces exhibit significant thermal resistances and generate an out of equilibrium phonon transport regime around the interface over several nanometers.

Study of phonon transport across Si/Ge interfaces using Full-Band phonon Monte Carlo simulation

Izitounene

et al. 2022

J Comput Electron

Self Cite

A Full Band Monte Carlo simulator has been developed to consider phonon transmission across interfaces disposed perpendicularly to the heat flux. This solver of the Boltzmann transport equation does not require any assumption on the shape the phonon distribution and can naturally consider all phonon transport regimes from the diffusive to the fully ballistic regime. This simulator is used to study single and double Si/Ge heterostructures from the micrometer scale down to the nanometer scale, i.e. in all phonon transport regime from fully diffusive to ballistic. A methodology to determine the thermal conductivity at thermal interfaces is presented.