Atomic-scale thermal metrology with electron beams: thermometry, phonon dynamics spectroscopy, and nanoscale heat...

Understanding how heat flows and dissipates at the atomic scale is critical for improving the performance and reliability of modern nanoelectronics and energy materials. Electron beam techniques-enabled by the high spatial resolution of transmission and scanning electron microscopy (TEM and SEM)-offer powerful, non-contact methods to probe local temperature and atomic vibrations beyond the reach of traditional optical or scanning probe approaches. In this review, we focus on three major fronts of recent progress in electron beam-based thermal analysis. First, we highlight advances in mapping atomic vibrations using vibrational electron energy-loss spectroscopy (EELS) in scanning TEM, which allow researchers to study how heat-carrying quasiparticles such as phonons, magnons, and polaritons behave near defects, grain boundaries, and interfaces. Second, we provide a comprehensive overview of electron beam-based thermometry techniques, including both EELS-based methods-such as plasmon energy shifts, core-loss edge shifts, and phonon peak analysis-and non-EELS thermometric signals derived from electron scattering, diffraction, cathodoluminescence, and electron beam current-based responses. These approaches are compared in terms of temperature sensitivity, spatial resolution, and practical implementation across TEM and SEM platforms. Third, we examine the use of focused electron beams as localized, non-contact nanoscale heat sources, which enables direct measurement of thermal conductivity, interfacial resistance, and heat dissipation pathways in nanostructures. This capability also supports emerging applications in materials characterization and additive nanofabrication. We further discuss the underlying electron-matter interactions that give rise to these thermometric signals, and outline current limitations, including moderate sensitivity, demanding sample preparation, and the need for advanced calibration and modeling-particularly in heterogeneous or device-scale systems. We conclude by highlighting opportunities for advancing e-beam thermal metrology through improved instrumentation, robust theoretical modeling, and data-driven analysis, establishing these approaches as powerful and quantitative framework for studying heat flow and energy transport at the atomic scale.