Diameter-Specific Growth of Semiconducting SWNT Arrays Using Uniform Mo₂C Solid Catalyst

Semiconducting single-walled nanotube (s-SWNT) arrays with specific diameters are urgently demanded in the applications in nanoelectronic devices. Herein, we reported that by using uniform Mo₂C solid catalyst, aligned s-SWNT (∼90%) arrays with narrow-diameter distribution (∼85% between 1.0 and 1.3 nm) on quartz substrate can be obtained. Mo₂C nanoparticles with monodisperse sizes were prepared by using molybdenum oxide-based giant clusters, (NH₄)₄₂[Mo₁₃₂O₃₇₂(H₃CCOO)₃₀(H₂O)₇₂]·10H₃CCOONH₄·300H₂O­(Mo₁₃₂), as the precursor that was carburized by a gas mixture of C₂H₅OH/H₂ during a temperature-programmed reduction. In this approach, the formation of volatile MoO₃ was inhibited due to the annealing and reduction at a low temperature. As a result, uniform Mo₂C nanoparticles are formed, and their narrow size-dispersion strictly determines the diameter distribution of SWNTs. During the growth process, Mo₂C selectively catalyzes the scission of C–O bonds of ethanol molecules, and the resultant absorbed oxygen (O_ads) preferentially etches metallic SWNTs (m-SWNTs), leading to the high-yield of s-SWNTs. Raman spectroscopic analysis showed that most of the s-SWNTs can be identified as (14, 4), (13, 6), or (10, 9) tubes. Our findings open up the possibility of the chirality-controlled growth of aligned-SWNTs using uniform carbide nanoparticles as solid catalysts for practical nanoelectronics applications