Production of individual suspended single-walled carbon nanotubes using the ac electrophoresis technique

Abstract

We have developed a new method for aligning individual suspended single-walled carbon nanotubes (SWNTs) using a combination of the ac electrophoresis technique and electron beam lithography. A poly(methyl methacrylate) (PMMA) “underpinning” was used in the region between the Au electrodes to prevent the carbon nanotube (CNT) from falling down on to the substrate. O2 plasma ashing was used to control the height of the underpinning PMMA layer so that it was same as that of the pre-defined electrodes. The biggest advantage of this method is that one can easily align the suspended nanostructure in a controllable manner. This method can also be applied to making suspended structures of organic materials that are sensitive to acid treatment. We measured the temperature-dependent I–V characteristics of the suspended SWNTs and found that most of the aligned SWNTs were metallic.