In nanoscale systems, the presence of defects significantly affects transport properties. Writing in Physical Review B, Steven Hunt and co-workers at the University of California, Irvine, present a scanning probe technique that allows them to distinguish different types of defects in single-walled carbon nanotubes.
Carbon nanotubes are very good nanoscale conductors with a mean free path of the order of a micrometer. The structure of single-walled carbon nanotubes is usually very clean and free of defects, however, when chemically modified or doped, defects can be inadvertently introduced.
Hunt et al. show they can identify point defects caused by the oxidation of nanotubes when immersed in water, sulfuric acid, and hydrochloric acid using the technique of scanning gate spectroscopy, which combines scanning probe microscopy and transport measurements. Based on their measurements, they develop a scattering model that takes into account the kind of defect and its resultant effect on transport. The next step will be to investigate a broader range of defects that occur when functionalizing carbon nanotubes. – Daniel Ucko