Thermal transport across diamond/copper interface functionalized by self-assemble monolayer

Copper and diamond composite is regarded as one of the most promising candidates for effective condensed heat dissipation. However, thermal boundary conductance (TBC) between copper and diamond becomes a key factor for deciding thermal conductivity. Interface functionalization using self-assemble monolayer (SAM) is a well-known method for enhancing TBC of a solid interface. While the underlying mechanism has been discussed in terms of strengthening the bonds or bridging of the lattice vibrational spectra, there is a need for more experiment-simulation coupled work on a well-defined system. In this sense, the copper and diamond system is ideal as the soft copper and hard diamond give rise to a large mismatch in the lattice vibration frequencies and the smoothness/uniformity.
In this study, we measure the TBC of copper/SAM/diamond interface by the time-domain thermoreflectance method. By using ellipsometer, X-ray photo-electro spectroscopy, and Fourier transform infrared spectroscopy, morphology and the chemical bonding of the SAM on copper and diamond are clearly observed. In addition, molecular dynamics simulations are carried out to explain the measured dependence of TBC. We found that there is a comprehensive correlation between the chain length, functional group, and TBC.