Session: 11-60-01: Simulations of Thermal Transport in Nanostructures and across Interfaces

Paper Number: 119974

119974 - Phonon Thermal Transport Between Two-Dimensional Materials Separated by a Vacuum Gap 

Graphene and silicene are two-dimensional materials with a hexagonal honeycomb structure made of carbon and silicon atoms, respectively. Graphene is the thinnest, strongest, and the most electrically conductive material. Due to these unique properties, graphene is making a significant impact on many industries such as electronics, medicine, energy, defense, and transport. Silicene has demonstrated potential for applications in electronic and photonic devices, lithium-ion batteries, as well as sensors. Understanding phonon transport across in-plane sheets of graphene and silicene separated by a sub-nanometric vacuum gap is important not only from a fundamental point of view, but also for thermal management of graphene-based and silicene-based electronics and nanodevices. This problem is also of significance for analyzing the effect of cracks and defects on thermal conductivity of graphene and silicene. In this presentation, we use the atomistic Green’s function method to study energy transport via phonons through a sub-nanometric vacuum gap between two in-plane sheets of graphene and silicene. The graphene sheets are semi-infinite with a width of 10 nm. The thermal conductance is obtained for various gaps ranging from 0 to 10 Å and various temperatures ranging from 5 to 500 K. The interatomic interactions within the graphene sheets are modeled using the Tersoff potential, while the Lennard-Jones potential is used for modeling the interactions between graphene atoms across the vacuum gap. The Stillinger-Weber potential is used for modeling the interactions between silicene atoms located in the same sheet, and the interaction of silicene atoms across the gap is modeled using the Lennard-Jones potential. It is found that for both graphene and silicene, thermal conductance monotonically increases with increasing the temperature. The larger thermal conductance at higher temperatures is due to a reduction in the group velocity of atoms which results in a higher density of states for phonons. The spectral distributions of thermal conductance show that thermal transport through the vacuum gap is mostly due to the contribution from acoustic phonons. At all temperatures, graphene has a thermal conductance several orders of magnitude greater than that for silicene. It is also found that thermal conductance rapidly decreases by seven orders of magnitude when the gap size is increased to 1 1.5 Å, while the rate of decreasing thermal conductance reduces with increasing the gap beyond 1.5Å. The findings of this work have implications for thermal management of graphene- and silicene-based devices and can contribute to developing reliable nanoelectronics and optoelectronic applications.

Acknowledgment: This work is supported by the National Science Foundation through grant number CBET- 2046630.

Presenting Author: Md Jahid Hasan Sagor University of Maine

Presenting Author Biography: Md Jahid Hasan is a Ph.D. student at the University of Maine. He started his Ph.D. studies in 2021 after completing a bachelor's degree in Mechanical Engineering at the Bangladesh University of Engineering and Technology in 2018. Hasan's thesis is focused on modeling heat transfer in the extreme near-field regime, where the heat-exchanging media are separated by gaps smaller than a few nanometers.

Authors:

Md Jahid Hasan Sagor University of Maine
Sheila Edalatpour University of Maine