Relation between the thermal conductivity and grain size in a polycrystalline silicene sheet

Abstract

Silicene, a two-dimensional allotrope of silicon, has outstanding mechanical and electrical properties which have triggered extensive research on its application in the field of developing faster computer chips, more efficient solar cells, improved medical technologies, vehicle, and aircraft parts, etc. In this work, we have demonstrated a way to use large-scale molecular dynamics to explore the effective thermal conductivity of nano-grained polycrystalline 2-D Silicene sheets and compare it with a pristine one. By performing non-equilibrium molecular dynamics (NEMD) simulations, the effect of grain size on the thermal conductivity of polycrystalline Silicene sheets has been investigated. For both pristine and polycrystalline Silicene sheet, structures of 30 nm × 30 nm are considered and Stillinger-Weber potential is used to investigate the atoms’ interaction with theneighborhood. The temperature profiles are used to find the thermal conductivity by Fourier’s Law of conduction. Comparing with the pristine Silicene sheet we have found a very intriguing result. Our results reveal that the ultra-fine nano-grained Silicene structures have an increasing trend for thermal conductivity commensurate with grain size. Larger the grain size becomes, higher the thermal conductivity is. However, for very small grain size the thermal conductivity is considerably less than the pristine structure. It is also noticed that the thermal conductivity of smaller grain size structures shows more grain size dependency while the thermal conductivity for larger grain size exhibits trivial gradient and almost converges to some certain range of values.The grain size based rising trend is then evaluatedby specific heat calculation.The density of states (DOS) is ultimately calculated for different grain sizes to verify the trend of changing thermal conductivities on the basis of noise sensitivity.