Interfacial thermal resistance plays a critical role in heat dissipation, when the mean free paths of heat energy carriers approach or exceed the characteristic lengths of devices. Deep understanding on electron and phonon scattering, as well as their coupling behaviors are of importance for interfacial heat transport enhancement. In this work, complicated influential mechanisms of interface defects on phonon scattering are studied, from the aspects of both time‐domain thermoreflectance (TDTR) measurements and atomistic simulations. Particularly, this study focuses on the comprehensive influence of inelastic phonon scattering on interfacial thermal conductance (hK) of hexagonal and amorphous boron nitride (BN)/copper (Cu) interfaces with nonreactive and nondiffusive features. The TDTR results imply that the hK of Al/a‐BN/Cu is ≈80% higher than that of Al/h‐BN/Cu counterpart, with the comparable film thicknesses, grain sizes, and interface roughness. Although lower local strain near h‐BN/Cu interface can boost electron–phonon coupling, inelastic phonon scattering at a‐BN/Cu interface may greatly promote the interfacial heat transport. The authors believe multiple phonons scattering accompanied by high‐frequency phonons transformation to low‐frequency phonons within a‐BN may provide more phonon–phonon coupling channels at the a‐BN/Cu interface. The present findings may provide more insights to understand nanoscale heat transport mechanisms at metal/nonmetal interfaces.

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Engineering the surface orientation of face-centered cubic (fcc) metals to the close-packed {111} plane can significantly enhance their oxidation resistance. However, owing to the synergetic effect of surface energy density (γ˙) and strain energy density (ω), such close-packed surface orientation can currently only be achieved by atomic-level thin film epitaxy or monocrystallization of polycrystalline metals. In this study, we characterized the microstructures of pure copper (Cu) foil and two types of graphene-coated Cu (Gr/Cu) foils and observed a 12~14 nm thick reconstructed surface layer with the {111} orientation in the high-temperature deposited Gr/{001} Cu surface. Combining the statistical results with thermodynamic analysis, we proposed a surface melting-solidification mechanism for the reconstruction of the Cu surface from {001} orientation to {111} orientation. This process is dominated by Gr/Cu interfacial energy and is particularly promoted by high-temperature surface melting. We also validated such a mechanism by examining Cu surfaces coated by h-BN (hexagonal boron nitride) and amorphous carbon. Our findings suggest a possible strategy to enhance the surface properties of fcc metals via engineering surface crystallography.

Interfacial bonding that directly influences the functional and mechanical properties of metal/nonmetal composites is commonly estimated by destructive pull-off measurements such as scratch tests, etc. However, these destructive methods may not be applicable under certain extreme environments; it is urgently necessary to develop a nondestructive quantification technique to determine the composite's performance. In this work, the time-domain thermoreflectance (TDTR) technique is applied to study the inter-relationship between interfacial bonding and interface characteristics through thermal boundary conductance (G) measurements. We think that interfacial phonon transmission capability plays a decisive role in influencing interfacial heat transport, especially for scenarios with a large mismatch of phonon density of states (PDOS). Moreover, we demonstrated this method at (100) and ( 111) cubic boron nitride/copper (c-BN/Cu) interfaces by both experimental and simulation efforts. The results show that the TDTR-measured G of the (100) c-BN/Cu interface (30 MW/m 2 •K) is about 20% higher than that of the (111) c-BN/Cu (25 MW/m 2 •K), which is ascribed to that higher interfacial bonding of the (100) c-BN/Cu endows it with better interfacial phonon transmission capability. In addition, detailed comparison of 10+ other metal/nonmetal interfaces exhibits similar positive relationship for interfaces with a large PDOS mismatch but negative relationship for interfaces with a small PDOS mismatch. The latter one is attributed to that extra inelastic phonon scattering and electron transport channels abnormally promoting interfacial heat transport. This work may provide some insights into quantitatively establishing inter-relationship between interfacial bonding and interface characteristics.

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