Concentrating on Etching

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Science  26 Jun 2009:
Vol. 324, Issue 5935, pp. 1621
DOI: 10.1126/science.324_1621b

The etching of nanometer-scale features on substrates is usually achieved with polymeric masks patterned by ultraviolet lithography, with resolution tied to the irradiation wavelength. Liu et al. report an alternative approach, whereby carbon nanotubes can act as catalysts for etching trenches in silicon dioxide 4 to 6 nm deep and about 60 nm in width. They first grew carbon nanotubes on silicon via chemical vapor deposition, with diameters of 1 to 4 nm. Immersion in basic solution led to etching rates that were about three times faster in the vicinity of the carbon nanotubes than elsewhere on the substrate, an effect which the authors attribute to the greater concentration of hydroxide groups that adsorb on the hydrophobic surface of the nanotubes in the electrical double layer. Atomic force microscopy revealed that most of the carbon nanotubes on the surface were released into solution after etching.

J. Am. Chem. Soc. 131, 10.1021/ja903333s (2009).

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