Study on Lattice Thermal Conductivity of Silicon Thin Film with Aligned Nano-pores

A frequency-dependent phonon Boltzmann transport equation solver is presented to numerically study the lattice thermal conductivity of nano-porous silicon thin film based on the Discrete Ordinates Method. We find that not only characteristic size and porosity, but also the shapes of both unit cell and pore do affect the lattice thermal conductivity. Therefore, we arranged a series of computational cases by the orthogonal design method to investigate the influence of geometric parameters L_x, L_y, a_x/L_x and a_y/L_y (L_x is unit cell length, L_y unit cell width, a_x pore length and a_y pore width). Furthermore, a non-linear regression model is established depending on the data obtained from those computational cases. The result shows that lattice thermal conductivity of nano-porous silicon thin film decreases obviously with the increase of a_x/L_x and a_y/L_y. Among these four geometric parameters, a_y/L_y is the most significant factor while L_x and L_y have little effect on lattice thermal conductivity. The proposed regression model can offer useful suggestion for the fabrication of nano-porous silicon thin film with lower lattice thermal conductivity.