Estimation of anisotropic thermal conductivity in nanoscale confined semiconductors via lattice Boltzmann method

A novel transient thermal transport model based on lattice Boltzmann method is developed to capture the sub-continuum effects including anisotropic thermal behavior of solids at nanoscale. Rigorous boundary condition treatment is incorporated via ghost boundary formulation. These subcontinuum effects deviate significantly from the bulk behavior and can not be accurately captured by the continuum based models such as Fourier equation. We observed that as the thickness of the semiconductor film is decreased to the scale of its carrier's mean free path, the thermal conductivity of the film reduces drastically from its bulk value and starts to show anisotropic behavior. In addition, a temperature jump, which does not exist at the bulk conditions, is observed at the interfaces. These sub-continuum effects are successfully captured by the lattice Boltzmann model and simple equations have been developed to accurately estimate these effects using the film geometry and properties.