Electrical transport across contacting multiwalled carbon nanotubes revealed by <i>in situ</i> electron microscopy

Understanding electrical transport of nanoscale contacts is crucial for the performance and reliability of flexible electronics and composite materials, yet a comprehensive understanding of this interfacial electrical transport remains elusive. Here, we developed an experimental method within scanning electron microscopy (SEM) to simultaneously visualize the morphology of a single contact junction and in situ measure the electrical transport between two multiwalled carbon nanotubes that are separately bonded on a movable nanoprobe and an electrode. The correlation analysis of real-time captured contact morphology and in situ measured electrical contact resistance (ECR) demonstrates that structural non-uniformity, local curvature, and surface defects dominate ECR, overshadowing the impact of macroscopic contact geometry such as the crossing angle. Besides, sustained current flow induces Joule heating, which can fuse the CNTs at the contact and reduce ECR by up to 70.5%, which is supported by the bonded junction after the separation. It was also found that under certain contact conditions, an open circuit persists despite physical contact, which is attributed to the presence of an amorphous surface layer. Our work provides direct insights into the interplay between morphology, defects, and electrical transport at the CNT–CNT junction, offering guidance for optimizing the design of nanoscale electronic and thermoelectric devices.