Atomic‐Scale Interface Phonon Engineering for Thermal Management: An Electron Microscopy Review

ABSTRACT Ongoing miniaturization and rising power density of electronic devices have drastically increased heat flux densities, making thermal management a critical bottleneck for device performance and reliability. While theoretical models have long underscored the role of interface phonon modes in governing interfacial heat transfer, recent transformative progress has emerged in experimental techniques for probing these modes. Notably, scanning transmission electron microscopy coupled with electron energy‐loss spectroscopy (STEM‐EELS) has achieved breakthroughs in visualizing interface phonons, featuring sub‐nanometer spatial resolution and momentum resolution across Brillouin zones. This technique has recently been extended to dynamically probing nonequilibrium phonon transport, performing quantitative nanoscale thermometry, and conducting in situ measurements of interfacial Kapitza resistance, offering direct experimental insights into heat transport mechanisms. These capabilities have spurred interface engineering strategies as powerful tools to deliberately modulate phonon‐mediated thermal conductance. Here recent advances are highlighted, unresolved challenges are identified, and promising directions are outlined in atomic‐scale interfacial thermal transport, laying a foundation for the rational design of advanced electronic materials, thermal management materials, and thermoelectric materials.