Session: 03-03: Micro/Nanoscale Interfacial Transport Phenomena

Paper Number: 140379

140379 - Role of Anharmonicity in Dictating the Thermal Boundary Conductance Across Interfaces Comprised of Two-Dimensional Materials 

Abstract: 

Understanding the fundamental mechanisms governing heat transport across interfaces comprised of two-dimensional (2D) materials is crucial for the further development of next generation of optoelectronic devices based on 2D heterostructures for which one of the main factors affecting the device performance is their poor thermal management. In this study, through systematic atomistic simulations, we show that along with the relevance of flexural modes and the strength of interaction between the graphene and MoS₂-based 2D and three-dimensional (3D) substrate, the intrinsic anharmonicity and the strength of coupling between the modes of the 2D material dictates the temperature dependent thermal boundary conductance across the dimensionally mismatched 2D-3D interfaces. Specifically, we conduct nonequilibrium molecular dynamics simulations on computational domains with graphene or MoS₂-based layers encapsulated between two semi-infinite crystalline or amorphous silicon leads across a wide temperature range (of 50 - 600 K). We find that the graphene-based heterostructures demonstrate drastically higher anharmonic interactions that are significantly weaker in the MoS₂-based structures. Moreover, we show that while the interfacial conductance across a graphene and crystalline silicon interface demonstrates considerable temperature dependence, the conductance across a graphene and amorphous silicon interface has no significant temperature dependence. In contrast, the thermal boundary conductance for the MoS₂-based heterostructures with both the crystalline and amorphous leads demonstrate no significant temperature dependence. Our spectral energy density calculations along with our spectrally resolved heat flux accumulation calculations on the various interfaces, provide critical insights into the mode- and spectral-level details that dictate thermal boundary conductances across these 2D-3D interfaces. These calculations highlight the importance of anharmonic coupling across the entire vibrational spectrum as well as the strong hybridization of a broader spectrum of the flexural modes with substrate Rayleigh waves in graphene heterostructures, which give rise to the relatively higher and drastically different heat transport mechanisms with a much more pronounced temperature dependence across these interfaces as compared to the MoS₂-based heterostructures. Through these understandings, we show that one strategy to enhance heat conductance across 2D-3D interfaces is to increase the anharmonic coupling between the acoustic and optic modes in the 2D materials by inducing a stronger van der Waals interaction strength with the substrates. Our findings elucidate the fundamental heat-transfer mechanisms dictating thermal boundary conductances across 2D-3D interfaces, and as such, will be crucial for heat dissipation in the next generation of optoelectronic devices where the utilization of 2D materials are becoming ubiquitous.

DOI: https://doi.org/10.1103/PhysRevApplied.20.014039

Presenting Author: Sandip Thakur University of Rhode Island

Presenting Author Biography: I'm a graduate research assistant at the Energy Transport and Ultrafast Spectroscopy Lab, University of Rhode Island, USA. My research is primarily focused on delving into the fundamental aspects of heat transfer, with the overarching goal of controlling and tuning thermal properties at the submicron length scale and femto-to-picosecond time scales. To achieve this, I employ laser-based optical techniques for experimental investigations and utilize state-of-the-art computational tools, including atomistic molecular dynamics simulations, to unravel the intrinsic mechanisms of heat transfer at the nano/macro scale, particularly in addressing the issue of wasted heat generated during the operation of optoelectronic devices.

Authors:

Sandip Thakur University of Rhode Island
Ashutosh Giri University of Rhode Island