Carbon Nanotubes

Physics / mechanism

Single-walled carbon nanotubes (SWCNTs) are rolled graphene sheets; chirality vector (n,m) determines whether they’re metallic or semiconducting. Semiconducting SWCNTs have bandgaps ~0.4–1.2 eV (diameter-tunable), carrier mobilities up to ~10,000 cm²/V·s, and current-carrying capacity ~10⁹ A/cm²—well beyond copper or silicon. Multi-walled CNTs (MWCNTs) sacrifice electrical precision for mechanical performance: tensile strength ~60 GPa, Young’s modulus ~1 TPa. State of the art: IBM/MIT demonstrated 14,000-CNT-transistor chips at sub-10 nm effective gate length; Carbonics and SiCarbon are pushing RF and logic CNTFETs toward tape-out. Chirality-sorted, 99.9% semiconducting purity is now achievable at small scale via gel chromatography and aqueous two-phase separation.

Competitive landscape

Competing approaches in the post-silicon transistor race: GaN and SiC own high-power RF and power electronics now; III-V (InGaAs, GaAs) leads high-frequency RF with mature fab infrastructure; 2D materials (MoS₂, WSe₂) offer monolayer channel thickness but suffer contact resistance and wafer-scale uniformity problems. Graphene is faster but zero-bandgap, requiring engineered confinement. Against copper interconnects, CNT vias compete with Ru and Co from Applied Materials and Lam Research at sub-20 nm nodes.

Companies using

Connected ideas

Sources

Frontier (open questions)

• To be added.