Computational Insights into the Effects of Heteroatom Doping of Graphene on the Interfacial Phonon Thermal Transport in Graphene–Diamond Heterostructures

Efficient thermal management in 2D–3D heterostructures hinges upon phonon transmission across weakly bound interfaces, yet how heteroatom doping of the 2D layer reshapes vibrational coupling remains unclear. Here, we combine nonequilibrium molecular dynamics (NEMD) simulation with vibrational spectral analysis and complementary density functional theory (DFT) calculations to investigate phonon-mediated thermal transport across graphene–diamond (Gr–D) interfaces as Gr is substitutionally doped with nitrogen (N), boron (B), and silicon (Si) at dopant concentrations of 5, 10, and 15% at 298 K. The undoped Gr–D heterostructure (control) exhibits an interfacial thermal conductance (ITC) of ∼14 MW m –2 K –1 . N-doping yields ITC values comparable to the control (∼11–14 MW m –2 K –1 ), while B-doping gives a modest increase of ITC up to ∼16 MW m –2 K –1 at 15% dopant concentration. Remarkably, Si-doping of Gr produces a monotonic, large ITC enhancement from ∼19 to 57 MW m –2 K –1 going from 5 to 15% dopant concentration, a 3-fold gain over the control. Frequency-resolved analysis shows a dopant-induced bimodal redistribution of the out-of-plane projected density of states (PDOS), reweighting from the 8–20 THz (mid) band into the 0–8 (low) and 20–40 THz (high) bands with Si causing the strongest shift and the largest Bose–Einstein (BE)-weighted spectral overlap with diamond. Out-of-plane BE-weighted overlap strongly correlates with ITC, indicating that spectral matching rather than intrinsic damping contributes to thermal phonon transport. DFT results show that Si-doping increases the interfacial interaction energy and produces localized charge accumulation between the protruded Si and topmost diamond C atoms, consistent with stronger vibrational coupling inferred from NEMD. Together, these results provide a mechanistic framework for understanding the role of dopants in simultaneously increasing out-of-plane spectral co-occupancy and strengthening interfacial coupling that can raise ITC in Gr–D and other similar 2D–3D heterostructures.