Thermal conductivity and spectral phonon properties of freestanding and supported silicene

We conduct molecular dynamics (MD) simulations to study the thermal conductivity of freestanding silicene and silicene supported on an amorphous silicon dioxide (SiO2) substrate in the temperature range from 300 to 900 K. The results show that the thermal conductivity decreases with increasing temperature and that the presence of the SiO2 substrate results in a great reduction, up to 78% at 300 K, to the thermal conductivity of silicene. With atomic trajectories from equilibrium MD simulations, we perform spectral energy density analysis to compute the thermal conductivities, spectral phonon relaxation times, and spectral phonon mean free paths (MFPs) of freestanding and supported silicene at 300 K. When silicene is put on a SiO2 substrate, the phonon relaxation times are decreased from 1-13 ps to less than 1 ps, and the phonon MFPs are reduced from 10-120 nm to 0-20 nm. We also calculate the thermal conductivity contributions from all phonon branches and find that the thermal conductivities of freestanding and supported silicene are mainly (>85%) contributed by the longitudinal and transverse acoustic phonons, while the out-of-plane acoustic phonons have a contribution less than 3%. Our study predicts the reduction of the thermal conductivity of silicene due to substrate effects and provides a fundamental understanding of the reduction in terms of the spectral phonon relaxation times and MFPs. (C) 2015 AIP Publishing LLC.