The role of Cr interlayer in determining interfacial thermal conductance between Cu and diamond

Interfacial thermal conductance (h) plays a decisive role in attaining high thermal conductivity in diamond particles reinforced Cu matrix (Cu/diamond) composites for promising thermal management applications. In this article, Cu/Cr bilayer films were deposited onto a single-crystalline diamond substrate by magnetron sputtering to form a Cu/Cr/diamond sandwich structure to clarify the role of the Cr interlayer in determining h between Cu and diamond. The 50 nm-thick Cr film was deposited at 773 K with various lengths of holding time to regulate the transformation of Cr to Cr3C2. The h between Cu and diamond was experimentally measured by a timedomain thermoreflectance technique. The Cu/Cr/Cr3C2/diamond structure with a mixed Cr and Cr3C2 interlayer exhibits an h value of 168 MW/m(2)K, higher than 57 MW/m(2)K for the Cu/diamond structure, 96 MW/m(2)K for the Cu/Cr/diamond structure, and 86 MW/m(2)K for the Cu/Cr3C2 /diamond structure. The Cr interlayer improves the interfacial bonding and reduces the acoustic impedance mismatch between Cu and diamond; however, the full transformation of Cr to Cr3C2 reduces the h value due to lower thermal conductivity of Cr3C2 than Cr. This study provides guideline for interface modification to attain high thermal conductivity in Cu/diamond composites.