Preferential growth of semiconducting single-walled carbon nanotubes by a plasma enhanced CVD method

Single-walled carbon nanotubes (SWNT) are grown by a plasma enhanced chemical vapor deposition (PECVD) method at 600 degreesC. The nanotubes are of high quality as characterized by microscopy, Raman spectroscopy, and electrical transport measurements. High performance field effect transistors are obtained with the PECVD nanotubes. Interestingly, electrical characterization reveals that nearly 90% of the nanotubes are semiconductors and thus highly preferential growth of semiconducting over metallic tubes in the PECVD process. Control experiments with other nanotube materials find that HiPco nanotubes consist of similar to61% semiconductors, while laser ablation preferentially grows metallic SWNTs (similar to70%). The characterization method used here should also be applicable to assessing the degree of chemical separation of metallic and semiconducting nanotubes.