Microscope etches ultrathin lines

So far, no lithographic technique has rivaled electron beam lithography for etching nanoscale lines and shapes, but the process is not appropriate for widespread use because it is expensive and cannot be operated in parallel.

Researchers from the University of Sheffield in England have shown that it is possible to match electron beam resolution for organic materials using an ultraviolet laser shown through a near-field optical microscope. Near-field microscopes emit light through tiny apertures placed very close to a surface, yielding non-radiating light that covers an area many times smaller than the light's wavelength.

The researchers etched 20-nanometer features into a single layer of molecules on a gold surface using 244-nanometer ultraviolet light.

The method could be used to make highly miniaturized arrays of proteins and DNA for biological sensors and analyzers.

The effect is caused by the interaction of light with the polycrystalline gold surface, and the resolution corresponds to the gold's grain size. Using single-crystal gold yielded resolutions at or above the aperture size of 50 nanometers, according to the researchers.

In principle the process can be used in fluid, opening the prospect of doing nanoscale photolithography at the same time as fluid flows through a system. This would make it possible to build multi-component molecular structures by flowing appropriate chemicals during the lithography process, according to the researchers.

They are working on parallelizing the method. The technique could be used to produce a highly miniaturized, high-throughput biological analysis system within three years, according to the researchers. The work appeared in the June 30, 2004 issue of Nano Letters.