Imaging carbon nanotubes by scanning electron microscopy

Scanning electron microscopy (SEM) is used as a primary tool for imaging of nanostructures, including carbon nanotubes. Recent developments of the SEM technique have opened new capabilities for sample analysis at the nanoscale with potential industrial and metrological applications. We will discuss selective imaging of single-walled carbon nanotubes on insulators. The role of the electron beam parameters, effect of surrounding media and substrate, and carbon nanotubes properties on their appearance as seen by an SEM are analysed. The comparison of scanning electron microscopy with atomic force microscopy images will also be presented. Our results support some of the commonly accepted opinions about why such images appear as they do, but mostly contradict them. At the same time our discovery opens new analytical possibilities for applications of an SEM. Funding for this work has been provided by a NASA/MSFC Phase II SBIR, Contract No. NAS8-02102, through a subcontract from Lytec, LLC., and by the NSF NIRT Program, Grant No. 0304506. SEM was done at the Electron Probe Instrumentation Centre at Northwestern University.