Competing effects of strain and vacancy defect on thermal conductivity of silicene: A computational study

We theoretically investigate the thermal conductivity of freestanding silicene under isotropic tensile strain in a wide range of temperature and in the presence of important scatterings. Based on the phonon Boltzmann transport equation within the relaxation time approximation and using the strain-dependent force constants obtained from the first-principle calculations, we calculate the variations of thermal conductivity of strained infinite and finite-size silicene with the single-vacancy defects and boundary scatterings and compare them with those in the case of unstrained silicene. Particularly, we are interested in exploring the competition between the two opposing effects; strain induces enhancement and vacancy defects cause reduction in thermal conductivity. We show that the presence of vacancy defects has a more remarkable and much stronger effect in strained silicene and is able to remove or shift the peak created by strain in the thermal conductivity of infinite silicene. Interestingly, we find that the thermal conductivity suppression due to the vacancy defects varies with strain. Furthermore, presented results indicate that by increasing the temperature, the thermal conductivity becomes less sensitive to the strain and the difference between infinite and finite size samples gradually disappears. Finally, our calculations show that the effect of specularity parameter of boundary scattering is more pronounced at intermediate strain values.