Unraveling the mechanisms of thermal boundary conductance at the graphene-silicon interface: Insights from ballistic, diffusive, and localized phonon transport regimes

Effective heat dissipation is critical for the performance and longevity of electronic devices. This study delves into the intricacies of thermal boundary conductance (TBC) between multilayer graphene and silicon, scrutinizing its correlation with graphene thickness. Employing a combination of the no-transducer time-domain thermal reflection technique and nonequilibrium molecular dynamics simulations with empirical and machine-learning based potentials, we discover an intriguing behavior: TBC initially increases with graphene thickness, but it eventually converges, suggesting that this phenomenon originates from the transition of the phonon transport from the ballistic to the diffusive regime in multilayer graphene. It is further demonstrated that a graphene-${\mathrm{MoS}}_{2}$ heterostructure exhibits a thickness-independent TBC behavior due to the strong phonon localization across the entire frequency range. The present study emphasizes the significance of incorporating phonon transport regimes in the design and optimization of thermal interfaces, laying the groundwork for innovative strategies to enhance heat dissipation in electronic devices.