Towards the synthesis of semiconducting single-walled carbon nanotubes by floating-catalyst chemical vapor deposition: Challenges of reproducibility

High-purity semiconducting single-walled carbon nanotubes (s-SWCNTs) are of paramount significance for the fabrication of high-performance electronics. Here, we present continuous production of highpurity, long, and isolated s-SWCNTs by gas-phase synthesis, retaining the pristine morphologies of assynthesized nanotubes. The s-SWCNTs were synthesized at ca. 920 degrees C using ethanol and methanol as carbon source and growth enhancer, respectively in N2 and H2. The purity of as-produced s-SWCNTs with a mean length of 15.2 mm can reach 98% as determined by optical absorption spectroscopy. We observed that the overpressure in the reactor and methanol are the principal causes of the enrichment of sSWCNTs. Specifically, the s-SWCNTs were found to be more negatively charged, and oxygen-contained species play critical roles in the s-SWCNT synthesis. Through the demonstration of field-effect transistors, the s-SWCNTs exhibit a high mean charge carrier mobility of 453.3 cm2 V-1 s-1 which is 2.27 times higher than that of the transistors fabricated with high-quality dispersion-processed SWCNTs. Additionally, we discuss the challenges of synthesis repeatability and recommend a few tips to improve reproducibility. Our study represents an important step towards the scalable production of clean, long, and isolated s-SWCNTs with high purity and narrow bandgap distribution.(c) 2022 The Author(s). Published by Elsevier Ltd.