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Communication Dans Un Congrès Année : 2018

Full Band Ab-Initio Monte Carlo simulation of heat transfer in nanostructures

Résumé

Modeling accurately the heat transfer in devices having a characteristic length close to the phonon mean free path in which the Fourier’s heat transport formalism reaches its limits is challenging [1]. Besides when the lateral size of the structure also reaches the nanoscale, the role of the phonon reflections at the external interfaces becomes of high importance. The Boltzmann’s transport equation for phonons (pBTE) can be used to investigate heat transport regimes beyond the diffusive regime in structures in the range of few nanometers to few microns. A stochastic resolution of the pBTE based on particle Monte Carlo (MC) algorithm is very efficient in terms of computational resources in the case of complex systems [2]. In this work, an original versatile particle MC simulator in which the material parameters, i.e. phonon dispersion and scattering rates, are parametrized by using ab initio calculations is presented [3]. It is a Full-band simulator as both the dispersion and the scattering rates are computed in the entire 3D Brillouin zone. Besides, for modeling the transport at rough external interfaces, a combination of specular and diffuse phonon reflections at the external rough interfaces have been implemented in phase space. This coupling between MC and ab-initio methods overcomes the main limitation of the MC approach by allowing the study of a large set of phases and materials without any empirical parameter. Moreover, the thermal transport can be investigated along all transport directions. In this work the phonon transport in rough nanowires and thin films made of both cubic (Si3C) and hexagonal (Si2H) Silicon have been carefully investigated by using our MC approach. For instance, the effective thermal conductivity is plotted as a function of the length in Figure a). The transition from a ballistic regime in short devices to a diffusive regime in long devices is clearly illustrated. In Figure b) the angular distribution of the density of states (DOS) shows that the main direction of the thermal flux in Si3C is [100] but [111] and [110] are also significant. Finally, the contribution of each phonon band is detailed. References: [1] D.G. Cahill, et al., J. App. Phys. 93, 793 (2003) [2] D. Lacroix, et al., Appl. Phys. Lett. 89, 103104 (2006) [3] L. Chaput, et al., Appl. Phys. Lett. 112, 033104 (2018)
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Dates et versions

hal-01951979 , version 1 (11-12-2018)

Identifiants

  • HAL Id : hal-01951979 , version 1

Citer

B. Davier, J. Larroque, Philippe Dollfus, Laurent Chaput, S. Volz, et al.. Full Band Ab-Initio Monte Carlo simulation of heat transfer in nanostructures. Nanoscale and Microscale Heat Transfer VI, Dec 2018, Levi, Finland. ⟨hal-01951979⟩
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