Phonon thermal transport in diamond-graphene superlattices

Diamond-graphene superlattices, constructed by periodically assembling diamond and graphene domains via strong covalent bonds, have attracted increasing attention due to their potential to integrate the outstanding properties of both materials. While diamond and graphene individually exhibit ultrahigh thermal conductivity, the phonon transport characteristics of their covalently bonded superlattice structures remain poorly understood, especially regarding the role of strong sp²-sp³ interfaces. This lack of understanding hampers the rational design of carbon-based composites for efficient thermal management.

In this study, we employ non-equilibrium molecular dynamics simulations to systematically investigate phonon-mediated thermal transport in diamond-graphene superlattices. We demonstrate that the interfacial thermal conductance reaches 6.33 × 10⁹ W/m²K, a value significantly higher than most other covalently bonded heterostructures, owing to strong carbon–carbon bonding and low atomic mass. Moreover, the thermal conductivity exhibits a distinct non-monotonic dependence on periodic length, reflecting a transition from coherent to incoherent phonon transport regimes: it decreases below a coherence threshold and increases beyond it. Temperature variation from 200 to 600 K does not shift the coherence-period minimum, indicating that the coherence–incoherence crossover is robust within this temperature range.

These findings address a key knowledge gap in understanding heat conduction in covalently bonded carbon superlattices. They provide fundamental insights into the mechanisms of phonon coherence and interfacial transport, offering valuable guidance for the design of advanced thermal interface materials and next-generation nanoelectronic devices where efficient heat dissipation is essential.