Rate-selected growth of ultrapure semiconducting carbon nanotube arrays

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−1 with on/off ratio around 108 and mobility over 4000 cm2 V−1 s−1. 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.

Band Engineering of Carbon Nanotubes for Device Applications

“…(D) Rate-selected growth method. Adapted with permission from Zhu et al 23 Copyright 2019, Springer Nature. (E) DGU solution separation method.…”

Bandgap‐Coupled Template Autocatalysis toward the Growth of High‐Purity sp2Nanocarbons

“…To investigate the relationship between the bandgap of CNT and the growth kinetics, we similarly depict the growth rate by TOF, which represents the counts of C2 assembled onto one circumferential active site per second. And the method to derive TOF for a CNT with specific chirality from length rate is TOF = R × Q atom / m , [ 75 ] where R is length growth rate, Q atom is the number of carbon atoms within a 1 nm long CNT wall and m is the chiral index. It is necessary to note that elongation can happen on both ends of the CNT seed during the cloning growth, different from the metal‐catalyzed CVD.…”

“…Recently, our investigation has revealed a clear interlocking relationship between growth kinetics of ultralong CNTs and their bandgap, [ 75 ] where the growth follows vapor–liquid–solid mode. Hence, the kinetics and the template atomic assembly dominate the growth process.…”

“…As shown in Figure 10e, Rayleigh images of individual CNTs obeying tip growth mode manifest that the colors of CNTs changed once or several times at the end, indicating that the growing CNTs would approach death after several chirality changes induced by topological defects. Our statistical results of kinetic growth of ultralong CNTs [ 75 ] evidently show that the percentage of defective CNTs would decrease sharply as the length increases (Figure 10f), arising from the defect‐induced disturbance for growth and resultant inferiority in kinetic competence than perfect CNTs.…”

Nanoscale Patterning of Carbon Nanotubes: Techniques, Applications, and Future

“…1) CNTFETs can have superior electrical and mechanical properties and be scaled to smaller dimensions than possible with standard Si CMOS FETs ( Figure a–c). [ 132b,319 ] CNTFETs have excellent intrinsic carrier mobility, [ 91,320 ] small subthreshold slopes that can potentially reach lower than the theoretical minimum of Si FETs (60 mV dec −1 ), [ 321 ] high on‐state current density up to 900 µA µm −1 , [ 322 ] and high transconductance. [ 219b,300c,307a ] These properties have the potential to allow Moore's Law to hold true, where conventional Si continues running into issues when scaling down.…”