Nanostructuring enforced sandwich-tubular CNT-Cu interconnects

The miniaturization of microchips requires high strength and conductivity of nanoscale interconnects. With utmost mechanical strength, carbon nanotubes (CNTs) are a common reinforcement. An open issue is how to improve the mechanical strength of CNT-metal composites in nanoscale. Here, via structure engineering, we introduce a novel CNT-sandwiched tubular copper nanocomposite. Theoretical enhancement factor referring to 5-nm-wire copper is approximately 4, 10, and 6 folds for Young's modulus, ultimate tensile strength, and tensile toughness, respectively, using single-walled CNT reinforcers. The enhancement can be further increased with the number of walls of CNT, as well as the reduction of the cross-section size. The reinforcement is proportional to CNT volume fraction, which is higher than that of conventional Halpin-Tsai model, up to 2 times. Even at the high temperature of 900 K, the nanocomposite structure still has a considerably high Young's modulus (219.8 GPa), ultimate tensile strength (26.0 GPa) and tensile toughness (2.22 GJ m⁻³), suggesting advanced high-temperature applications. Vibration density of state analysis reveals the origin of the enhancement and the change of C[sbnd]C bonds state during tensile process. The abnormally high reinforcement suggests the essential role of nanostructure engineering.