The metal/diamond interface consisting of two highly dissimilar materials is widely present in high-power microelectronic devices using a diamond film as a heat spreader or using a metal matrix/diamond filler composite as a heat sink for thermal management applications. To improve the interfacial thermal conductance (G), a common method is to add an appropriate interlayer in between the two materials; however, the effect of the interlayer on G is still not clear. In this work, we prepare a Cu/TiC/diamond structure by magnetron sputtering to detect how the crystallinity, grain size, and thickness of the TiC interlayer influence G between Cu and diamond. We characterize in detail the interface by transmission electron microscopy and X-ray photoelectron spectroscopy and measure experimentally G by the time-domain thermoreflectance technique. The results indicate that the higher crystallinity and thinner interlayer are both beneficial to the improvement of G between Cu and diamond, but the G is insensitive to the grain size of TiC. An increase of G between Cu and diamond as much as 48% can be reached by a highly crystallized 10 nm thick TiC interlayer. The microscopic characteristics of the TiC interlayer have played a decisive role for G between Cu and diamond. While an inserted interlayer in principle has a potential to enhance G between two dissimilar materials, the low crystallinity and large thickness of the interlayer will weaken the enhancement or even reverse this positive effect. The G of a sandwiched structure can be regulated in a wide range by the microscopic characteristics of the interlayer, which provides guidelines for preparation of metal/nonmetal interfaces with high interfacial thermal conductance for thermal management applications.
Keywords: highly dissimilar materials; interfacial thermal conductance; interlayer; sandwich structure; thermal management applications; time-domain thermoreflectance.