Scalable Alignment of Carbon Nanotubes via Shear

Abstract

Semiconducting carbon nanotubes must be aligned at optimal packing densities prior to the integration of this material into transistors, however, this has been historically difficult to accomplish on a wafer-scale. Here, we use solution-based shear to deposit continuous films of well-aligned, individualized, semiconducting nanotubes across target substrates. We are able to generate shear up to 10,000 s-1, which serves to align the carbon nanotubes, by forcing the carbon nanotubes in organic solvent through sub-mm tall channels. To investigate the effect of the alignment on charge transport properties, transistors are fabricated parallel and perpendicular to the alignment direction. The parallel transistors perform with 7× faster mobility while still retaining a high on/off ratio of 105. Optimized experimental conditions enable alignment within a ±32°, at 50 nanotubes µm-1, on a 10 × 10 cm2 substrate.