Tube-tube and tube-surface interactions in straight suspended carbon nanotube structures

An investigation concerning the tautness of suspended carbon nanotubes (CNTs) grown using the chemical vapor deposition (CVD) method is presented. The suspended nanotubes were analyzed with both a transmission electron microscope (TEM) and a high-resolution scanning electron microscope (HR-SEM). The HR-SEM and TEM investigations revealed that the interaction between CNTs among themselves as well as with the surface on which they are grown is a primary cause for the tautness of suspended tubes. Specifically, the tube-tube and tube-surface dynamics cause adjoining tubes to create a "zipper-effect", thereby straightening and tightening them. Suspended CNTs cling to each other and to as much of the surface as possible and thus minimize their total energy, creating taut, suspended structures. This effect can be so strong so as to force wide tubes to buckle, with no other external force involved. The implications of this study include all forms of alignment processes of nanotubes using the CVD method. The results presented here provide the groundwork for the capability of fine-tuning the control of CNT network formation using substrate mechanical features.