Wednesday, August 16, 2006

US Patent 7091096 - Electrochemical Fabrication of Nanotube FET


One of the most significant problems in nanotube-based electronics is the separation of metallic-type nanotubes from semiconductive-type nanotubes. In order to form a nanotube transistor semiconductor-type nanotubes are necessary, however most of the fabrication procedures used to make nanotubes produce a mixture of both types. Several techniques have been developed to sort the semiconductive-type from the metallic-type and other techniques use current burn off methods to remove the unwanted metallic-type. This patent proposes an electrochemical approach that electrically neutralizes the metallic type nanotubes so as to create nanotube field effect transistors. Claim 1 reads:

1. A method of fabricating a structure with field-effect transistors, said transistors each comprising a source electrode, a drain electrode, a channel extending between the source and drain electrodes and at least one gate electrode associated with the channel for controlling the conductance of the channel, wherein the channel comprises one or more semiconducting single-wall carbon nanotubes, the method including the steps of a) depositing a plurality of single-wall carbon nanotubes on a substrate, said carbon nanotubes comprising a mixture of metallic carbon nanotubes and semiconducting carbon nanotubes, b) providing before or after step a) source and drain electrodes on the substrate so that one or more carbon nanotubes extend between the source and drain electrodes, c) applying a variable gate voltage to switch off the semiconducting tubes extending between the source and drain electrodes, d) wetting the surface of the structure including the transistors with a chemical to achieve a chemical bond between a radical supplied by said chemical and some carbon atoms of the metallic nanotubes, whereby these metallic nanotubes become non-conductive.