Vapor–solid–solid growth of single-walled carbon nanotubes

Single-walled carbon nanotubes (SWCNTs) are promising for nanoscale electronics and photonics, but practical deployment requires chirality control. Most catalytic chemical vapor deposition (CCVD) growth of SWCNTs proceeds on liquid metal nanoparticles via a vapor–liquid–solid (VLS) mechanism and yields broad chirality distributions, whereas improved selectivity has been reported for high-melting-point crystalline catalysts, suggesting vapor–solid–solid (VSS) growth. However, the atomistic mechanism and kinetics of VSS SWCNT growth remain unclear. Here, microsecond-timescale, machine-learning-driven growth simulations on rhenium nanoparticles reveal that VSS growth is diffusion-limited, governed by facet-dependent surface carbon transport and carbon-driven facet reconfiguration, and proceeds without catalyst melting. Carbon surface diffusion is up to ∼ 50 × slower than diffusion in liquid iron, imposing an upper bound on sustainable carbon supply and defining a narrow growth window: low temperatures promote carbon accumulation and multiple nucleation, whereas high temperatures favor graphitic encapsulation. In contrast to defect-free VLS growth, defects persist, indicating slow defect healing, and equilibrium simulations reveal suppressed edge configurational entropy with stabilization of zigzag-rich, Klein-decorated edges. Together, these results establish facet evolution and surface diffusion as joint regulators of transport-limited VSS growth and motivate stringent control of temperature and carbon supply.