Collaborative Research: Thermal Transport via Four-Phonon and Exciton-Phonon Interactions in Layered Electronic and Optoelectronic Materials

University Of Texas At Austin, Austin TX

Investigators

Abstract

Semiconductor research and development over the past several decades have enabled widespread use of electronic and optoelectronic devices in society. Among the challenges that the semiconductor industry is facing, it has become increasingly difficult to remove the large density of heat generation and prevent overheating of silicon microchips. As one of the approaches to overcoming this challenge, atomic layered materials are now being actively investigated as next-generation electronic and optoelectronic materials due to their potentially superior electric, optical, and thermal properties compared to those of silicon. Compared to the silicon properties that have been extensively investigated, many properties of these emerging materials have remained to be understood. Heat can be transported by atomic vibration waves in these layered materials and other solids. It is currently unclear how the highly nonlinear interatomic springs influence the heat transfer ability of the atomic vibration in these layered materials. In addition, light illumination on semiconductors can excite electrons to high-energy states that are referred as excitons. There is currently a knowledge gap in the heat-carrying ability of these excitons and their influence on the atomic vibration waves. This project aims to address the outstanding questions on these two specific fundamentals that control the heat transport properties in these layered materials. The obtained knowledge will be used to build new simulation tools, enhance online courses and classroom instruction, and develop hands-on education modules to aid the recruitment and training of a diverse population of next-generation workforce in thermal engineering. The goal of this project is to advance the fundamental understanding of the effects of four-phonon and exciton-phonon interactions in thermal transport and energy dissipation in emerging layered electronic and optoelectronic materials. Specifically, four outstanding questions that are essential for the operation of emerging layered electronic and optoelectronic materials will be addressed: (1) How four-phonon interactions impact the thickness dependence of the lattice thermal conductivity in multi-layered graphene and carbon nanotubes (CNTs); (2) Whether four-phonon interactions reduce or broaden the temperature window of hydrodynamic phonon transport in graphitic materials; (3) Whether exciton diffusion can provide another channel for heat transport from hot spots in layered optoelectronic and electronic materials; and (4) How exciton-phonon coupling influences the lattice thermal transport and local non-equilibrium in emerging TMD devices. These questions will be addressed by new computational models that integrate frontier first-principles theory of exciton-phonon and four-phonon coupling, and unique nanoscale thermal metrology tools including the multi-probe thermal transport and photo-heat current measurements. The obtained fundamental understanding of four-phonon and exciton-phonon interactions helps to establish the foundation for modeling and controlling energy dissipation and thermal transport in emerging layered electronic and optoelectronic devices. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.