Interfacial strength between single wall carbon nanotubes and copper material: Molecular dynamics simulation

Due to their promising mechanical and electrical properties, carbon nanotubes (CNTs) have the potential to be employed in many nano/microelectronic applications e.g., through silicon vias (TSVs), interconnects, transistors, etc. In particular, use of CNT bundles inside annular cylinders of copper (Cu) as TSV is proposed in this study. To evaluate mechanical integrity of CNT-Cu composite material, a molecular dynamics (MD) simulation of the interface between CNT and Cu is conducted. Different arrangements of single wall carbon nanotubes (SWCNTs) have been studied at interface of a Cu slab. Pullout forces have been applied to a SWCNT while Cu is spatially fixed. This study is repeated for several different cases where multiple CNT strands are interfaced with Cu slab. The results show similar behavior of the pull-out-displacement curves. After pull-out 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 pull-out forces and the number of CNT strands was observed. Second order interaction effect was found to be negligible when multiple layers of CNTs were studied at the interface of Cu. C-Cu van der Waals (vdW) interaction was found to be much stronger than C-C vdW's interactions. Embedded length has no significance on the average pull-out force. However, the amplitude of oscillations increases as the length of CNTs increases. As expected when one end of CNT strand was fixed, owing to its extraordinary strength, large 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.