Rate-selected growth of ultrapure semiconducting carbon nanotube arrays.

Zhu, Zhenxing; Wei, Nan; Cheng, Weijun; Shen, Boyuan; Sun, Silei; Gao, Jun; Wen, Qian; Zhang, Rufan et al. · Nat Commun · 2019

basic_science · Level V

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Abstract

Carbon nanotubes (CNTs) are promising candidates for smart electronic devices. However, it is challenging to mediate their bandgap or chirality from a vapor-liquid-solid growth process. Here, we demonstrate rate-selected semiconducting CNT arrays based on interlocking between the atomic assembly rate and bandgap of CNTs. Rate analysis confirms the Schulz-Flory distribution which leads to various decay rates as length increases in metallic and semiconducting CNTs. Quantitatively, a nearly ten-fold faster decay rate of metallic CNTs leads to a spontaneous purification of the predicted 99.9999% semiconducting CNTs at a length of 154 mm, and the longest CNT can be 650 mm through an optimized reactor. Transistors fabricated on them deliver a high current of 14 μA μm<sup>-1</sup> with on/off ratio around 10<sup>8</sup> and mobility over 4000 cm<sup>2</sup> V<sup>-1</sup> s<sup>-1</sup>. Our rate-selected strategy offers more freedom to control the CNT purity in-situ and offers a robust methodology to synthesize perfectly assembled nanotubes over a long scale.