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摘要
Research on heat conduction in periodic nanoporous silicon films has drawn much attention due to its importance for developing highly efficient thermoelectric devices. Here, the thermal transport in two-dimensional (2D) periodic silicon nanoporous films is studied by a phonon Monte Carlo (MC) method and the theoretical analyses based on the Boltzmann transport equation (BTE). It is found that both the cross-plane and the in -plane effective thermal conductivities are significantly reduced when compared to those in the diffusive limit, and decrease with the increasing porosity or the decreasing period length. Importantly, our work reveals a strong anisotropy of the effective thermal conductivity of the 2D In-planc heat conduction in 2D periodic nanoporous films; that is, the effective thermal conductivity nunoporous film in the in-plane direction is significantly less than that in the cross plane direction, due to the anisotropic effects of material removal and pore boundary scattering. Interestingly, even the influence of the specular parameter that depends on the pore boundary roughness is anisotropic in this case, which could provide an anisotropic tuning method on the effective thermal conductivities of the periodic nanoporous films. In addition, the effective thermal conductivity models, which well concern the anisotropy and the specular parameter dependence, are derived on the basis of Matthiessen's rule by introducing the geometrical factors that can be obtained from the MC simulations. The good agreements have been achieved between the present models and the MC simulations, verifying the validity of the models.
- 出版日期2017-3-9
- 单位清华大学
