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 to 8.06 × 10 m·K·W, 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.