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

Paper Number: 119969

119969 - Near-Interface Effects on Interfacial Phonon Transport 

Interfacial thermal transport is essential to the thermal management in microelectronics, which has become one of the major bottlenecks to the continued scaling of microelectronics for the next generation and beyond as microelectronics become increasingly smaller with higher power density. The prediction of interfacial thermal conductance (ITC) requires an understanding of heat carriers' properties and their scattering mechanisms at the interface. In 1959, Little proposed the acoustic mismatch model (AMM) to access the interfacial thermal transport, which assumed all phonons elastically transferred across the interfaces. Swartz and Pohl then proposed the diffuse mismatch model (DMM) by considering the incident phonons were completely scattered diffusively. Therefore, the DMM excludes the wave nature of phonons, which leads to an underestimation of the contribution of low-frequency phonons for predicted ITC. Furthermore, atomistic Green's function (AGF) was developed to solve the phonon transfer across the solid/solid interfaces based on the phonon gas model (PGM). All these methods mentioned above consider the interfacial thermal transport via phonon-phonon couplings across the ideal interface with no thickness. However, recent studies suggest that the phonon-phonon couplings, as well as the phonon nonequilibrium distribution in the near-interface region, may affect interfacial thermal transport. In this work, we quantitatively characterize the thermal transport across Ar/heavy-Ar (Ar/h-Ar) and Cu/Si interfaces by considering phonon-phonon couplings in the near-interface region and across the interface. By performing the spectral heat current decomposition in the frame of nonequilibrium molecular dynamics (NEMD) simulations and phonon correlation analysis, we systematically study the phonon-phonon couplings across the interface and in the near-interface region. We further investigate the influence of temperature and interfacial adhesion on the interfacial thermal transport, in which the phonon-phonon couplings in the near-interface region are found to be strongly correlated to temperature and interfacial adhesion. The phonon-phonon couplings in the near-interface region can either hinder or benefit the interfacial thermal transport depending on the competition between the phonon-phonon scattering and the phonon-phonon coherence. The dual effect of the phonon-phonon couplings in the near-interface region is stemming from the wave-particle duality of phonons, i.e., these wave-like low-frequency phonons can benefit the interfacial thermal transport via phonon coherence, while the high-frequency phonons behave like particles and hinder the thermal transport via scatterings. For the Ar/h-Ar interfaces, we find that the phonon-phonon couplings in the near-interface region can be ignored for the interfacial thermal transport as the contribution from phonon-phonon coherence is offset by that from the phonon-phonon scatterings. For Cu/Si interfaces, the phonon-phonon couplings in the near interfacial region are found to benefit the interfacial thermal transport at low temperatures (i.e., < 400 K) when the low-frequency phonon-phonon coherence is dominant. When the phonon-phonon scatterings become more important at high temperatures (i.e., > 400 K), the phonon-phonon couplings in the near-interface region, therefore, hinder the interfacial thermal transport. Our work here provides a fundamental physical understanding of interfacial thermal transport, considering phonon-phonon couplings across the interface and in the near-interface region. 

Presenting Author: Yanguang Zhou The Hong Kong University of Science and Technology

Presenting Author Biography: Dr. Yanguang Zhou received his Ph.D. degree with “Ausgezeichnet” in the Mechanical Engineering Department at RWTH-Aachen University. He worked as a postdoc research associate and an assistant visiting project scientist at the University of California, Los Angeles (UCLA) before joining Hong Kong University of Science and Technology (HKUST) as an assistant professor. Dr. Zhou’s group at HKUST designs advanced materials & structures, i.e., thermoelectric materials, magnetic materials and nanocomposites, via using nanotechnologies (both experimental and theoretical methods), with applications in water harvesting and thermal management. His research has been published in Nature Communications, Nano Letters, Advanced Functional Materials, International Journal of Heat and Mass Transfer and Physical Review B. Dr. Zhou is a receipt of AICES Fellowship, Chinese Government Award for Outstanding Self-financed Students Abroad, Borchers-Plakette at RWTH-Aachen University and Hong Kong SciTech Pioneers Award.

Authors:

Yanguang Zhou The Hong Kong University of Science and Technology