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Direct photolithographic route to selective growth of single-walled carbon nanotubes using a modified photoresist with ferrocene

We report a direct photolithographic route to selective growth of single-walled carbon nanotubes (SWNTs) using a simple mixture of ferrocene and conventional photoresist as a catalytic photoresist (Cat-PR), which play the role of both a catalyst and a photoresist for SWNT patterned growth. Using the Cat-PR, catalytic nanoparticles with diameters of 3–10 nm were formed on the defined regions and SWNTs with diameters of 1.0–1.5 nm were selectively grown on the pre-patterned catalyst. For the successful growth of SWNTs on the pre-defined regions, all organics of the Cat-PR should be completely removed by a burning process in order to obtain catalytically active nanoparticles. The quality and density of the grown SWNTs were dramatically improved by supplying water vapour during the nanotube growth, possibly due to the enhanced activity of nanoparticles. Most radial breathing mode (RBM) peaks of the grown SWNTs in Raman spectra from 785 nm laser excitation are assigned to the semiconducting nanotubes. It is also demonstrated that nanotubes suspended between three-dimensional stands can be easily prepared by using the Cat-PR patterns as an etch mask.