Title: Thermal boundary conductance of metal diamond interfaces predicted by machine learning interatomic potentials

Abstract: Thermal boundary conductance (TBC) across metal diamond interfaces plays a critical role in the thermal management of future diamond based ultrawide bandgap semiconductor devices. Molecular dynamics is a sophisticated method to predict TBC but is limited by the lack of reliable potential describing metal diamond interfaces. In this work, we report the development of machine learning interatomic potentials and the prediction of TBCs of several technologically promising metal diamond interfaces using nonequilibrium molecular dynamics. The predicted TBCs of Al, Zr, Mo, and Au-diamond interfaces are approximately 316, 88, 52, and 55 MW/m2K, respectively, after quantum corrections. The corresponding thermal boundary resistances are equivalent to 0.8 {\mu}m thick of Al, 1.4 {\mu}m Mo, 0.3 {\mu}m Zr, and 5.3 {\mu}m Au, respectively. We also find that the conventional simple models, such as the acoustic mismatch model and diffuse mismatch model, even including the full-band phonon dispersion from first principles, largely misestimate the TBC values because of their inability to include inelastic transmission as well as interfacial structural and bonding details. The quantum-corrected TBC values for the metal diamond interfaces correlate well with the quantum corrected phonon specific heat of metals, instead of diamond. Additionally, our comparative analysis of Debye temperature and elastic modulus in these systems reveals that the former parameter correlates more strongly with the TBC than the latter. These low TBC values need to be considered in future diamond based semiconductor devices.