Dose-Controlled, Floating Evaporative Self-assembly and Alignment of Semiconducting Carbon Nanotubes from Organic Solvents

Arrays of aligned semiconducting single-walled carbon nanotubes (s-SWCNTs) with exceptional electronic-type purity were deposited at high deposition velocity of 5 mm min–1 by a novel “dose-controlled, floating evaporative self-assembly” process with excellent control over the placement of stripes and quantity of s-SWCNTs deposited. This approach uses the diffusion of organic solvent on the water–air interface to deposit aligned s-SWCNT (99.9%) tubes on a partially submerged hydrophobic substrate, which is withdrawn vertically from the surface of water. By decoupling the s-SWCNT stripe formation from the evaporation of the bulk solution and by iteratively applying the s-SWCNTs in controlled “doses”, we show through polarized Raman studies that the s-SWCNTs are aligned within ±14°, are packed at a density of ∼50 s-SWCNTs μm–1, and constitute primarily a well-ordered monodispersed layer. The resulting field-effect transistor devices show high performance with a mobility of 38 cm2 V–1 s–1 and on/off ratio of 2.2 × 106 at 9 μm channel length.