Triggering Lattice Oxygen Release for Semiconducting Carbon Nanotube Array Synthesis.

Area of Science:

• Materials Science and Engineering
• Nanotechnology
• Catalysis

Background:

• Lattice oxygen in metal oxides is crucial for advanced catalyst design.
• Selective growth of semiconducting single-walled carbon nanotubes (s-SWCNTs) requires precise catalyst control.
• Existing methods for s-SWCNT synthesis often yield mixtures of metallic and semiconducting tubes.

Purpose of the Study:

• To develop a novel strategy for enhancing lattice oxygen release from oxide catalysts.
• To achieve direct synthesis of high-purity, horizontally aligned s-SWCNT arrays.
• To explore the potential of oxygen-centric catalyst design for nanomaterial synthesis.

Main Methods:

• Implementation of a lattice oxygen triggering (LOT) strategy using ion implantation of titanium (Ti) and iron (Fe) into a sapphire substrate.
• Annealing process to facilitate Ti surface migration and Fe substitution within the sapphire lattice.
• Formation of catalysts via doping of Fe atoms into Ti oxides, initiating the LOT process.

Main Results:

• Achieved a significant increase in lattice-oxygen release flux (up to 10^5).
• Successfully synthesized horizontally aligned s-SWCNT arrays with >98% purity due to in situ etching of metallic tubes by released oxygen.
• Fabricated field-effect transistors from s-SWCNT arrays demonstrating excellent performance (subthreshold swing of 60 mV dec⁻¹, carrier mobility of 2291 cm²·V⁻¹·s⁻¹).

Conclusions:

• The LOT strategy provides a paradigm for controlling lattice oxygen kinetics and thermodynamics in oxide catalysts.
• This approach enables the precise synthesis of high-purity semiconducting nanomaterials.
• Opens new avenues for oxygen-centric catalyst design in the synthesis of advanced nanostructures.