Correlation between interlayer thickness and diamond/Cu interfacial thermal conductivity at the nanoscale

To elucidate the correlation between the interlayer thickness and the interfacial thermal conductivity (ITC) of the diamond/Cu interface at the nanoscale, diamond/W(WC)/Cu nanolayered structures with varying interlayer thicknesses were prepared by magnetron sputtering, and their ITC was directly measured by time-domain thermoreflectance (TDTR) system. The results indicate that an excessively thin interlayer enhances interfacial scattering, thereby shortening the effective mean free path (MFP) of hot carriers, which suppresses thermal transport and limits the overall thermal conductivity. When the interlayer thickness approaches the MFP of hot carriers, the significantly reduced interfacial scattering promotes cross-interface transport, resulting in peak ITC of 101.5 MW/(m²·K) for W (20 nm) and 88 MW/(m²·K) for WC (15 nm), respectively. However, further increasing the interlayer thickness introduces considerable bulk thermal resistance and defect scattering, which decreases the transport efficiency of hot carriers and ultimately reduces the ITC at the diamond/Cu interface.