Researchers at the University of Rochester in New York, Portland State University in Oregon and Harvard University in Cambridge, Mass., have reported a spatial resolution of 25 nm in their study of the near-field Raman imaging of single-walled carbon nanotubes. They presented the findings of their experiments in the March 7 issue of Physical Review Letters.

Their setup featured 20- to 30-nm-diameter silver probes and 633-nm laser illumination with a 1.4-NA inverted optical microscope. The scientists produced near-field Raman images (above) of two samples of nanotubes and demonstrated that it is possible to resolve the spectra of 5-nm-high Ni/Y catalyst particles separated by 35 nm in the 1.7-nm-diameter tubes.

They have since achieved 17-nm resolution with the technique.