Carbon nanotubes (CNTs) offer exceptional electronic properties, making them promising candidates for high-performance thin-film transistor (TFT) applications. However, conventional fabrication exposes CNT surfaces to resists, leaving persistent residues that degrade dielectric and contact interfaces, resulting in reduced on-state current, lower mobility, poor subthreshold swing, and device nonuniformity. Existing approaches, including ultraviolet-ozone treatment, wet etching, or sacrificial layers, partially mitigate contamination but cannot fully eliminate residues and often limit device scaling. Here, we introduce a fabrication process for top-gate CNT TFTs that achieves resist-contamination-free interfaces using atomic layer etching (ALE) technology. A Y₂O₃ sacrificial layer defines the active region, enabling high-quality atomic layer deposition of the gate dielectric. Selective ALE precisely etches the dielectric above source/drain regions, with Ar plasma power tuned to minimize damage to underlying CNTs, yielding excellent metal contacts. CNT TFTs fabricated with this approach demonstrate a maximum on-state current of 27.1 μA/μm and peak mobility of 141 cm²/(V·s) at a channel length of 2 μm, and also exhibit excellent performance uniformity, low contact resistance, and low interface trap density. These devices surpass other CNT, low-temperature polycrystalline silicon (LTPS), indium-gallium-zinc-oxide (IGZO), and transition metal dichalcogenide (TMDC) TFTs in performance, scalability, and process simplicity. This work provides a scalable pathway towards high-performance CNT TFTs and also suggests potential for miniaturized transistors, as ALE’s vertical, highly directional etch preserves lateral dimensions.

Semiconducting single-walled carbon nanotubes (s-SWCNTs) are fascinating materials for future electronic and optical applications. Conjugated polymer wrapping is one of the most promising methods for mass production of high purity s-SWCNTs. However, its chiral selectivity is relatively inferior to other s-SWCNT production methods. In this paper, the chiral selectivity of two polymers, poly[(9,9-dioctylfluorenyl-2,7-diyl)-alt-co-(6,6′-{2,2′-bipyridine})] (PFO-BPy) and poly[9-(1-octylonoyl)-9H-carbazole-2,7-diyl] (PCz), which are representatives of widely used polyfluorene and polycarbazole families, respectively, were comparatively studied. Both polymers exhibited high selectivity for a subset of existing chiral species in each of the commercially available raw SWCNT materials (CoMoCAT, HiPco, and arc-discharge) which cover a diameter range of 0.6–1.8 nm. Less chiral species were selected by PFO-BPy from small diameter (< 1 nm) raw SWCNT materials, while more from large diameter (> 1.2 nm) raw materials. High chiral purity (6, 5) (> 99%) and (7, 5) (> 75%) solutions were extracted by PFO-BPy and PCz from CoMoCAT materials, respectively. The different chiral angle and diameter selections for different raw materials by both polymers were ascribed to their different geometrical structures and related polymer-tube interactions. Our work provides indispensable information for better understanding the mechanism of polymer wrapping method and improving extraction of single chirality s-SWCNTs.

Semiconducting single-walled carbon nanotubes (s-SWCNTs) are the foundation of CNT-based electronics and optoelectronics. For practical applications, s-SWCNTs should be produced with high purity, high structural quality, low cost, and high yield. Currently conjugated polymer wrapping method shows great potential to fulfill these requirements due to its advantages of simple operation process, high purity separation, and easy scaling-up. However, only a small portion of both CNTs and polymers go into the final solution, and most of them are discarded after a single use, resulting in high cost and low yield. In this paper, we introduce a closed-loop recycling strategy, in which raw materials (CNTs and polymers) and solvents were all recycled and reused for multiple separation cycles. In each cycle, high-purity (> 99.9%) s-SWCNTs were obtained with no significant change of structural quality. After 7 times of recycling and separation, the material cost was reduced to ~ 1% in comparison with commercially available products, and total yield was increased to 36% in comparison with 2%–5% for single cycle separation. Our proposed closed-loop recycling strategy paves the way for low-cost and high-yield mass production of high-quality s-SWCNTs.