One-step dry deposition technique for aligning single-walled carbon nanotubes

Here, we present a robust and dry technology to obtain aligned films of high-quality single-walled carbon nanotube (SWCNT) films. We employ a tandem reactor approach connecting an aerosol CVD setup, producing an aerosol of individual nanotubes, with a thermophoretic deposition chamber. To reach the nanotube alignment on the deposition substrate, we integrate temperature gradient-induced thermophoretic force, which deposits the SWCNT aerosol, with shear force, which orients the nanotubes along the flow. High Reynolds numbers required for the alignment lured us to the regions of high flow rates and, correspondingly, extreme temperature gradients (20,000 K/cm), which has not been assessed previously. Using a comprehensive set of methods (aerosol scanning mobility particle size spectrometry, UV-vis-NIR spectroscopy, scanning electron microscopy, etc.), we prove the nanotubes to deposit with the same rate regardless of the size and observe an orientation of aerosol SWCNT at Reynolds numbers > 1000. With the orientation of carbon nanotubes, we obtain anisotropic thin films with the state-of-the-art equivalent sheet resistance values among pristine SWCNTs, opening bright opportunities for transparent electronics.