Ultra-Efficient Heat Transport Across a "2.5D" All-Carbon sp²/sp³ Hybrid Interface

Single- and few-layer graphene-based thermal interface materials (TIMs) with extraordinary high-temperature resistance and ultra-high thermal conductivity are very essential to develop the next-generation integrated circuits. However, the function of the as-prepared graphene-based TIMs would undergo severe degradation when being transferred to chips, as the interface between the TIMs and chips possesses a very small interfacial thermal conductance. Here, a "2.5D" all-carbon interface containing rich covalent bonding, namely a sp²/sp³ hybrid interfaces is designed and realized by a plasma-assisted chemical vapor deposition with a function of ultra-rapid quenching. The interfacial thermal conductance of the 2.5D interface is excitingly very high, up to 110-117 MWm^-2 K^-1 at graphene thickness of 12-25 nm, which is even more than 30 % higher than various metal/diamond contacts, and orders of magnitude higher than the existing all-carbon contacts. Atomic-level simulation confirm the key role of the efficient heat conduction via covalent C-C bonds, and reveal that the covalent-based heat transport could contribute 85 % to the total interfacial conduction at a hybridization degree of 22 at %. This study provides an efficient strategy to design and construct 2.5D all-carbon interfaces, which can be used to develop high performance all-carbon devices and circuits.