Nanoscale Thermal Imaging of Dislocation-Mediated Heat Transport

Abstract

Dislocations in crystalline materials are widely exploited to tailor the thermal conductivity of semiconductors and thermoelectrics, yet a critical gap persists: direct measurement of local thermal resistance at individual buried dislocations, along with its spatial extent, remains elusive due to the limitations of conventional thermal probes. Here, we use in situ scanning transmission electron microscopy-electron energy-loss spectroscopy to map nanoscale temperature distributions across a low-angle SrTiO3 grain boundary with periodic dislocation arrays. Our results reveal a temperature drop of 47 K across the dislocation array. The associated temperature-field distortions are concentrated near the dislocation cores, consistent with stronger local thermal resistance at these discrete sites rather than a uniformly distributed resistance along the array. We further identify a distinct two-scale heat transport characteristic near the dislocation array: core-dominated effects over approximately 4.8-6.2 nm and extended inter-core influences over approximately 10.3-14.3 nm. Atomic-scale structural and vibrational analyses further reveal core-associated atomic reconstruction and localized optical-phonon perturbations, providing a microscopic basis for the stronger local thermal resistance inferred near dislocation cores. These findings quantitatively resolve spatial heterogeneity of dislocation-mediated heat transport, uncover its atomic-scale mechanism, and provide a quantitative basis for defect engineering, guiding the design of high-performance thermoelectrics, semiconductors, high-temperature structural alloys, and other functional crystalline materials.