Interfacial Behavior and Atomic Structures of Femtosecond Laser Self-Limiting Covalent Joining Carbon Nanotubes

The continuous miniaturization, integration, and intelligence of microelectronics are promoting the transformation of the micro/nanomanufacturing mode from the traditional top-down to bottom-up. Bottom-up manufacturing is essentially the assembly of smaller structural units such as atoms, molecules, nanoparticles, or wires into relatively large and complex structural systems, while the assembly process relies on reliable and efficient nanoconnections or interfacial contacts, which restricts the transformation process of nanofunctional materials to practical applications. Aiming at this purpose, the interfacial behavior and the atomic structures of self-limiting covalent joining carbon nanotubes (CNTs) by the femtosecond (fs) laser irradiation method were investigated. Experimental results show that the defects of CNTs are first reduced with the increase of the laser fluence. As the laser energy reaches 39.216 mJ/cm2, two CNTs in physical contact are successfully interconnected with covalent bonds with a small necking near the joint. The irradiation parameters of the fs pulse laser are obtained for the optimal connection of two separated CNTs. Molecular dynamics simulations reveal that how the two separated CNTs evolve into a covalent nanojunction dominated by sp2 bonds and that there is a high connection strength at the connection node. This covalent interconnection method, if further expanded, provides a potential support for realizing the atomic network reconfiguration and performance improvement of carbon-based functional nanomaterials and nanodevices.