Direct Thermal Resistance Measurement of a Single Defect in Graphite

Lattice defects in crystalline materials play a critical role in tuning thermal transport, as their thermal properties are highly sensitive to the atomic structure. However, characterizing such structure–property relationships has been hampered by the challenges in directly measuring thermal properties at the single-defect level. Here, we employ in situ scanning transmission electron microscopy–electron energy loss spectroscopy (STEM–EELS) to characterize ripplocation boundary-like defects (RBDs, i.e., curved lattice boundaries) in graphite, revealing their atomic-scale lattice dynamics and quantifying their local thermal resistance. At the RBD cores, we observe distinct spectral broadening of the out-of-plane and transverse acoustic phonon modes, a signature of enhanced localized phonon scattering. In situ STEM-EELS measurements reveal that the local thermal resistance of the RBDs is approximately 3–5 times higher than that of the defect-free matrix. Specifically, the typical thermal resistance of individual RBDs ranges from 4.69 × 10–11 to 8.06 × 10–11 m2·K·W–1, exhibiting dependence on the bending angle. These findings establish a quantitative link between the RBD atomic configurations, phonon features, and thermal resistance, providing guidelines for defect-engineered thermal management of graphite-based materials.