Thermal conductivity and spectral phonon properties of freestanding and supported silicene

Abstract

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.

Thermal transport in silicene nanotubes: Effects of length, grain boundary and strain

“…For instance, the thermal conductivity of ASNT and ZSNT decreases by about 50% when the temperature increases from 300-550 K while it decreases 18% in the temperature growth from 550-700 K. We notice that the thermal conductivity of silicene nanotubes versus temperature is not sensitive to chirality thus the MD results obtained for ASNT and ZSNT are the same. Our findings are in agreement with previously research reported on the temperature dependence of the thermal conductivity of bulk silicene and silicene nanosheets [47,49]. Studying the thermal properties of silicene nanotubes under extreme condition such as defects and strain is essential for practical applications.…”

“…In semimetals, such as silicene, the contribution of electrons on the thermal conductivity at room temperature and above is less than that of phonons. Therefore, non-equilibrium molecular dynamics (NEMD) simulation that ignores electron transport can be used to investigate the thermal properties of silicene [47]. In this research, the non-equilibrium molecular dynamics (NEMD) simulation is carried out using Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) [48] to study the effect of the grain boundary, axial strain, random vacancy defect, and temperature on the thermal conductivity of silicene nanotubes.…”

Phonon thermal conduction in novel 2D materials

“…Unlike graphene in which all carbon atoms form honey-cone structures within a flat plane, silicon atoms in silicone show a buckled structure, resulting in unique thermal transports fundamentally differing from that in other 2D materials, namely (a) longitudinal and transverse acoustic phonons dominate the thermal transports and the acoustic out-of-plane phonon modes only have less than 10% contributions to the total thermal conductivity [114][115][116][117]; (b) thermal conductivity increases dramatically with tensile strain due to enhancement in acoustic phonon lifetime [118][119][120]. Unfortunately, no experiment on thermal conductivity in silicene has been reported.…”

Molecular dynamics study of interfacial thermal transport between silicene and substrates

“…Wang et al, 13 Li et al 5 and Hu et al 2 employed the Tersoff potential to investigate the thermal conductivity of free-standing and supported single layer silicene. Tersoff potential 12 has been widely used to describe the Si atom interactions in bulk silicon and silicon nanotubes.…”