Phonon state modulated by interfacial binding at carbon/copper interface

B Zhong and JM Ni and Q Zhang and HY Huang and YF Liu and J Song and Y Liu and TX Fan, ACTA MATERIALIA, 296, 121211 (2025).

DOI: 10.1016/j.actamat.2025.121211

Enhancing interfacial binding strength and vibrational matching has been demonstrated to improve the thermal boundary conductance (TBC) at metal/non-metal interfaces. However, these factors are inherently interrelated and their individual contributions cannot be identified. In this study, we aim to disentangle this correlation using classical immiscible interfaces, including graphene/copper (Gr/Cu) interface as a counterpart, hydrogenated Gr (H-Gr)/Cu interface with high interfacial binding energy but low vibrational matching, and hexagonal boron nitride (BN)/Cu interface with similar interfacial binding energy but high vibrational matching. Compared to Gr/Cu interface, time-domain thermoreflectance measurements showed that the TBC values decreased by similar to 28% at H-Gr/Cu interface but increased by similar to 34% at BN/Cu interface. Density functional theory (DFT) calculations also revealed that the overlap of phonon density of states manifested a 32% decrease at H-Gr/Cu interface but a 73% increase at BN/Cu interface. In addition, DFT results indicated a similar interfacial binding energy of BN/Cu interface, rather than a nearly one-order of magnitude (similar to 875%) higher energy value at H-Gr/Cu interface. The converse trend between binding energy and vibrational matching can be explained by the simple harmonic motion model, where enhanced interfacial binding energy leads to higher-frequency phonon vibrations. Our non-equilibrium molecular dynamics simulations validated this behavior at these interfaces, demonstrating that the one order of magnitude increased binding energy results in a 20-47% further reduction in vibrational matching. Therefore, our results suggest that interfaces with low vibrational matching may exhibit low TBC values, even when such interfaces possess high interfacial binding energy. This work highlights the importance of balancing interfacial binding strength and vibrational matching, which may facilitate the rational design of carbon/Cu interfaces targeting ultra-high thermal transport.

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