Amorphous carbon interlayer modulated interfacial thermal conductance between Cu and diamond

Introducing an interlayer is an effective method to improve the interfacial thermal conductance (G) of highly mismatched Cu/diamond interface. However, the relative role of interfacial bonding effect and vibrational bridging effect of the interlayer is still not clear. Herein, we introduce amorphous carbon (a-C) layer by Ar ion bombardment, oxygenated a-C layer by Ar/O₂ mixture ion bombardment, and C-O bond by acid treatment at the Cu/diamond interface to regulate the interfacial bonding effect and vibrational bridging effect. The G of Cu/diamond is increased by 44% with increasing interfacial bonding strength from 12 mN to 17 mN and then is independent on interfacial bonding strength above 17 mN, which mainly comes from the interfacial bonding effect. Compared with the as-cleaned Cu/diamond interface, a 35% increase of G is obtained by inserting a 4.5 nm-thick a-C interlayer between Cu and diamond, which mainly comes from the vibrational bridging effect. The vibrational bridging effect overwhelms the interfacial bonding effect in improving the G of Cu/diamond interface when the interfacial bonding strength is relatively high. The findings give insights into the mechanisms dictating heat transfer of highly mismatched metal/non-metal interface and provide a new avenue for improving the G of Cu/diamond interface.