Nanoscale Thermal Imaging of Dislocation-Mediated Heat Transport

Dislocations are widely used to tailor lattice thermal conductivity in semiconductors and thermoelectrics, yet the local thermal resistance of individual buried dislocations and their spatial extent remain experimentally unresolved. Here, operando scanning transmission electron microscopy-electron energy-loss spectroscopy thermometry, atomic-resolution imaging, vibrational spectroscopy, and nonequilibrium molecular dynamics are combined to map heat transport across a dislocation array within a 5°SrTiO₃ low-angle grain boundary. The effective thermal conductance of the dislocation array is estimated to be ∼35.4 MW m^{- 2} K^{- 1} using the bulk reference conductivity, corresponding to a Kapitza length of ∼339 nm. Nanoscale temperature maps reveal a spatially heterogeneous resistance landscape: reconstructed dislocation cores act as sharp thermal bottlenecks over ∼2.14-5.17 nm, with steeper local temperature gradients than inter-core regions, whereas inter-core regions show weaker but more extended modulation over ∼8.34-11.57 nm. Correlative structural and vibrational analyses show that Ti─O bond distortion, Ti valence change, P4 optical-phonon blueshift, and reduced local-bulk phonon density-of-states overlap create a core-specific vibrational environment. These results uncover the underlying mechanism whereby atomic-scale core reconstruction generates nanoscale localized thermal resistance, and offer quantitative descriptors for defect-structure-guided thermal design.