Expert Profile:

Prof. Jae Sik Jin is currently a Professor in the Department of Smart Manufacturing Systems at Chosun College of Science and Technology, South Korea, a position he has held since April 2015. He received his B.S. degree in Mechanical Design Engineering from Seoul National University of Science and Technology in 1998, his M.S. degree in Mechanical Engineering from Hanyang University in 2000, and his Ph.D. in Mechanical and Aerospace Engineering from Seoul National University in 2007. Prior to his academic career, he gained extensive industry experience as an engineer at Doosan Mecatec and GM Korea Technical Center. Following his Ph.D., he conducted advanced research as a Postdoctoral Fellow at the Micro Thermal System Research Center at Seoul National University, the Department of Mechanical Engineering at Massachusetts Institute of Technology (MIT), and the Department of Aerospace and Mechanical Engineering at Saint Louis University. He also served as a Research Associate Professor at the Korea Advanced Institute of Science and Technology (KAIST) and as a Senior Researcher at the Samsung SDI Battery Research Plan/Institute. His extensive background spans both cutting-edge academic research and industrial applications in mechanical systems.

Title of Presentation:

 Beyond Phonon Polarization: Full-Dispersion Boltzmann Transport Analysis of Spectral Phonon Nonequilibrium in Nanoscale Silicon Devices

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M. Interactions between Phonon and Other Energy Carriers

Understanding nanoscale heat transport in semiconductor devices requires a spectral description beyond Fourier’s law and scalar thermal conductivity. When heat generation is confined to submicron or nanoscale regions, phonon populations become nonequilibrium, and the thermal response depends on phonon dispersion, polarization, group velocity, modal heat capacity, relaxation time, and intermodal scattering. This talk reviews a series of full phonon-dispersion Boltzmann transport studies for silicon-based thin films and devices. Early Monte Carlo and finite-volume solutions demonstrated the importance of simultaneously considering phonon dispersion and polarization for microscale and submicron heat conduction. These models enabled stable calculation of nonequilibrium phonon distribution fields and were later extended to electron–phonon interaction problems in SOI and NMOS transistors. The main focus is recent mode-resolved analysis of quasiballistic heat transport and hotspot thermal resistance in thin silicon layers. The results show that logarithmic quasiballistic scaling arises only from selected phonon modes forming a log-uniform conductivity plateau, while fully ballistic long-mean-free-path phonons produce a saturated nonlogarithmic background. Furthermore, hotspot thermal resistance is governed not by long mean free paths alone, but by spectral energy routing into modes with low modal heat capacity and weak intermodal coupling. Additional topics include temperature-dependent phonon relaxation, Akhiezer damping, and vibration-induced modification of acoustic phonon transport. Together, these studies indicate that nanoscale thermal resistance should be interpreted as a mode-resolved energy-storage and energy-transfer problem, rather than simply as a ballistic correction to Fourier conduction.