Sowing Clean‐Release Salt Catalyst for the Synthesis of Contamination‐Free Single‐walled Carbon Nanotube Arrays

Abstract Horizontal arrays of single‐walled carbon nanotubes (SWCNTs) have shown immense potential for application in emerging devices due to their excellent electrical and thermal properties. The direct growth of SWCNT arrays using high‐activity metal catalysts is one of the promising methods to approach the mass production of dense SWCNT arrays. However, an inevitable obstacle lies in the post‐purification of metal residual. Herein, a sowing strategy to prepare size‐tunable potassium chloride (KCl) catalysts for the efficient growth of the SWCNT array with a density of 10 tubes per micron is reported. Through a controllable etching process, numerous surface defects (e.g., vacancies and kinks) are uniformly generated on the substrate as seed pit‐like sites for the accommodation and anchoring of catalysts. The well‐distributed KCl catalysts with a homogeneous size of ≈1.4 nm enable the growth of ≈1.3 nm SWCNTs through a vapor‐liquid‐solid mechanism. Importantly, 94 at.% KCl catalysts can be dramatically removed through a simple water‐washing process, thus leaving contamination‐free SWCNT arrays behind. Interestingly, 85% of nanotubes show metallic properties, which is demonstrated by the combination of electrical characterization and the multi‐laser Raman spectroscopy. This sowing strategy contributes to the direct growth of uncontaminated high‐density SWCNT arrays.