Triggering Lattice Oxygen Release for Semiconducting Carbon Nanotube Array Synthesis

Lattice oxygen in metal oxides offers potential pathways for advanced catalyst design, including catalysts for the selective growth of semiconducting single-walled carbon nanotubes (s-SWCNTs). In this study, an increase of lattice-oxygen release flux up to 10⁵ is achieved via a lattice oxygen triggering (LOT) strategy for oxide catalysts. The LOT strategy is experimentally realized by ion implantation of titanium (Ti) and iron (Fe) elements into the sapphire substrate, followed by an annealing process for Ti migration onto the surface and Fe stable substitution in the sapphire lattice. The LOT process occurs when Fe atoms dope into Ti oxides, forming the catalysts for SWCNT growth. The continuously released lattice oxygen serves as an in situ etchant for precise removal of metallic tubes, resulting in the direct synthesis of horizontally aligned s-SWCNT arrays with >98% purity. Field-effect transistors based on the s-SWCNT arrays exhibit ultralow subthreshold swing of 60 mV dec^-1, and high carrier mobility of 2291 cm²·V^-1·s^-1. This LOT strategy establishes a paradigm for tuning lattice oxygen kinetics and thermodynamics, opening avenues for an oxygen-centric catalyst design in nanomaterial synthesis.