Spectral Control of Thermal Boundary Conductance between Copper and Carbon Crystals by Self-Assembled Monolayers

Controlling the thermal boundary conductance (TBC) between copper and carbon crystals is important since it can bottleneck the thermal conductivity when reinforcing copper with carbon-crystals fillers, namely diamond or graphite, to develop heat sinks and spreaders needed for the thermal management. In this work, by using the nonequilibrium molecular dynamics simulation, we show how the TBC of copper/diamond is smaller than that of copper/graphite by an order of magnitude due to poorer overlap of the lattice vibrational spectra. To improve the TBC at the copper/ diamond interface, the covalently bonded self-assembled monolayers (SAMs) with different chain lengths are installed at the interface. The TBC is significantly improved and increases with the chain length to approach the value of the copper/ graphite interface. The spectral analysis further identifies that this is because the length due to disordering of the collective SAMs structure, enhancing the spectral transmission in low-frequency vibrational modes with copper. The obtained results are useful to improve the thermal conductivity of metal/carbon-crystal composite materials.