Journal Article

Arrays of horizontal carbon nanotubes of controlled chirality grown using designed catalysts

Yang, Liangwei, Zhang, Jin, Wang, Zequn, Zhang, Shuchen, Qi, Kuo, Deng, Shibin, Bai, Xuedong, Ding, Feng, Tong, Lianming, Wang, Xiao, Kang, Lixing, Li, Qingwen

2017

Overview

Horizontal arrays of metallic or semiconducting carbon nanotubes with controlled chirality are grown from specially designed solid carbide catalysts. Controlling the chirality of carbon nanotubes The era of Moore's law, which predicts a doubling in the number of transistors per microprocessor chip every two years, seems to be coming to an end. Researchers are therefore developing alternative materials to use in nanoelectronic devices. Arrays of horizontal nanotubes are particularly appealing because this architecture optimizes current output. Now Jin Zhang and colleagues report the synthesis of two different horizontal carbon nanotube arrays with controlled chirality, one metallic and one semiconducting. The authors achieve this by using catalyst arrays that are designed to select for nanotubes with a specific diameter and crystal symmetry. The authors target nanotubes with the chiral structure (2 m , m ), which is fast growing and can be further enriched by optimizing the growth conditions. These findings are a further step towards a new generation of high-performance electronic devices and integrated circuits based on carbon nanotechnology. The semiconductor industry is increasingly of the view that Moore’s law—which predicts the biennial doubling of the number of transistors per microprocessor chip—is nearing its end 1 . Consequently, the pursuit of alternative semiconducting materials for nanoelectronic devices, including single-walled carbon nanotubes (SWNTs), continues 2 , 3 , 4 . Arrays of horizontal nanotubes are particularly appealing for technological applications because they optimize current output. However, the direct growth of horizontal SWNT arrays with controlled chirality, that would enable the arrays to be adapted for a wider range of applications and ensure the uniformity of the fabricated devices, has not yet been achieved. Here we show that horizontal SWNT arrays with predicted chirality can be grown from the surfaces of solid carbide catalysts by controlling the symmetries of the active catalyst surface. We obtained horizontally aligned metallic SWNT arrays with an average density of more than 20 tubes per micrometre in which 90 per cent of the tubes had chiral indices of (12, 6), and semiconducting SWNT arrays with an average density of more than 10 tubes per micrometre in which 80 per cent of the nanotubes had chiral indices of (8, 4). The nanotubes were grown using uniform size Mo 2 C and WC solid catalysts. Thermodynamically, the SWNT was selectively nucleated by matching its structural symmetry and diameter with those of the catalyst. We grew nanotubes with chiral indices of (2 m , m ) (where m is a positive integer), the yield of which could be increased by raising the concentration of carbon to maximize the kinetic growth rate in the chemical vapour deposition process. Compared to previously reported methods, such as cloning 5 , 6 , seeding 7 , 8 and specific-structure-matching growth 9 , 10 , 11 , our strategy of controlling the thermodynamics and kinetics offers more degrees of freedom, enabling the chirality of as-grown SWNTs in an array to be tuned, and can also be used to predict the growth conditions required to achieve the desired chiralities.

• Publisher: Nature Publishing Group UK,Nature Publishing Group
• Subject: 639/301/357/551 / 639/925/357/73 / Carbon / Catalysts / Cloning / Growth conditions / Growth rate / Humanities and Social Sciences / letter / multidisciplinary / Nanotechnology / Nanotubes / Science / Spectrum analysis / Symmetry / Thermodynamics