Co-designing growth factors for the synthesis of (6, 5)-enriched single-walled carbon nanotube horizontal arrays

Precise control over the diameter and chirality of single-walled carbon nanotubes (SWNTs) is critical for scalable electronic applications, yet it remains a challenge for horizontally aligned arrays. Although low-temperature powder synthesis routinely yields sub-1 nm SWNTs with relatively high chirality selectivity, directly transferring these growth conditions to substrate-guided horizontal arrays has been hindered by poorly understood catalyst evolution and coupled growth factors (gas, temperature, pressure etc). Here, we employ a machine-learning-assisted framework that integrates systematic experiments with interpretable models to optimize the growth parameters, enabling sub-1 nm SWNT growth in horizontal arrays at low temperatures. Our ML model reveals that SWNT formation is governed by kinetic competition between amorphous-carbon deposition and graphitized-carbon incorporation, with catalytic cracking acting as the dominant carbon source under low-temperature conditions. Further, we successfully achieve horizontally aligned SWNT arrays enriched in (6, 5) nanotubes with a chiral selectivity of approximately 70% at 650 °C under an optimized environment predicted by the ML model. This is the first demonstration of sub-1 nm chiral-selective growth in horizontal arrays at such a low temperature. This work bridges the long-standing gap between powder and horizontal-array growth and establishes a rational, data-driven strategy for the deterministic synthesis of SWNTs.