Electrical probing of single-wall carbon nanotubes suspended over trenches

Transport characterization of individual suspended single-wall carbon nanotubes (CNTs), spanning 50 μm deep trenches and having lengths of up to 100 μm, has been performed using a nanoprobe configuration in a scanning electron microscope (SEM). This configuration provides direct electrical contact to, and mechanical manipulation of, the CNT. The carbon nanotubes are grown from catalyst on the insulating SiO₂ surface of the trench structure via chemical vapor deposition, and span the trenches in the gas flow direction. This approach provides a fundamental investigation of the intrinsic transport properties of the nanotubes without disorder induced by the substrate or chemical residues from conventional lithographic patterning processes. The suspended CNTs are probed in an SEM chamber, and the use of a mobile probe as a gate electrode allows identification of metallic and semiconducting nanotubes. The ability of in-situ manipulation of the CNTs using the probes allows characterization of both unstressed (straight) and stressed (bent) CNTs. Details of the growth and fabrication procedures and characterization of transport on these long, suspended CNTs will be presented.