Molecular dynamics simulation of mechanical interface behavior of copper and single walled carbon nanotube bundles

Because of their remarkable thermal, mechanical and electrical properties, Carbon Nanotubes (CNTs) have significant potential to be employed in nano/micro-electrical applications as interconnects. However, they must be adaptable to the current copper (Cu) technology for this transition to occur. In this study, a hybrid structure of CNTs and Cu is used as interconnects. Molecular Dynamics (MD) simulation of the interface is conducted in order to evaluate mechanical integrity of CNT-Cu composite material. CNT-Cu interface has been studied by simulating different arrangements of Single Wall Carbon Nanotubes (SWCNTs) at the interface of a Cu slab. Displacement controlled loading has been applied to pull-out CNTs from the interface with Cu while Cu is spatially fixed. Pull-out forces have been determined for several different cases where multiple CNT strands interfaced with Cu slab. Pull-out force vs. displacement curve has been recorded for each case. The results show similar behavior of these curves. After pullout force reaches a maximum value, it oscillates around an average force with descending amplitude until the strand/s is/are completely pulled-out. A linear relationship between pullout forces and the number of CNT strands was observed. When multiple layers of CNTs were studied at the interface of Cu, second order effect was found to be negligible. Embedded length has no significance on the average pull-out force. However, the amplitude of oscillations increases as the length of CNT strand increases. As expected when one end of CNT strand was fixed, owing to its extraordinary strength, substantial amount of force was required to pull it out. Finally an analytical relationship is proposed to determine the interfacial shear strength between Cu and CNT bundle in interconnects.