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

Abstract

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 (Oads) 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.

Understanding the “Activation” of the Nanocluster [HxPMo12O40⊂H4Mo72Fe30(O2CMe)15O254(H2O)98-y(EtOH)y] for Low Temperature Growth of Carbon Nanotubes

“…The excessive growth temperatures required with FeMoC appear to counter previous work with Fe-Mo catalyst systems demonstrating CNT growth at temperatures as low as 550°C [22][23][24]. It should be noted that both Fe and Mo have been shown to be efficient catalysts both independently and as mixed metal nanoparticles [25][26][27][28][29][30]; thus, FeMoC should be ''active'' for CNT growth, but under the prior growth conditions studied it is not [16][17][18][19][20][21].…”

Investigation of growth dynamics of carbon nanotubes

“…Since then, chirality selective growth of SWCNTs was succeeded on a number of different catalysts: CoMo [106–108], FeCo [109], FeRu [110], NiFe [111], Co [112–114], FeCu [115], Au [116], CoMn [117], Ni [118], Fe [119–120], CoPt [121], Co x Mg 1−x O [122], CoSO 4 [123], WCo alloy [124–125] and Mo 2 C [126]. SiO 2 or MgO were used as catalyst support.…”

“…SiO 2 or MgO were used as catalyst support. The synthesis was conducted using different carbon precursors: CO [105–108 112–115 117–119 122–123], C 2 H 5 OH [107,109,120–121 124–126], CH 3 OH [107], CH 4 [110,116] and C 2 H 2 [111]. Table 1 summarizes the reports on the chirality selective synthesis of SWCNTs.…”

“…The authors of recent works [113,119–120 123–126] succeeded in the selective growth of SWCNTs with chiralities that are different from (6,5). In [113,123], near-armchair SWCNTs with a chirality of (9,8) were selectively synthesized.…”

Catalytic Growth of Carbon Nanotubes by Direct Liquid Injection CVD Using the Nanocluster [HxPMo12O40⊂H4Mo72Fe30(O2CMe)15O254(H2O)98-y(EtOH)y]

“…The addition of 25 Fe atoms to FeMoC through coordination would suggest that 139 atoms are sufficient, but 114 are not. When considering that both Mo and Fe have demonstrated effective catalytic performance both independently and as mixed heterogenous nanoparticles [19][20][21][22], FeMoC should be catalytically active, but under the growth conditions reported in prior work it is not [16,17,23,24]. We have recently shown that this is in part due to both incomplete catalyst activation and the sublimation of a portion of the Mo component during the slow catalyst activation process [25,26].…”