Vertically Aligned Single-Walled Carbon Nanotube Growth from Ir Catalysts by Alcohol Gas Source Method
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MRS Advances © 2019 Materials Research Society DOI: 10.1557/adv.2019.155
Vertically Aligned Single-Walled Carbon Nanotube Growth from Ir Catalysts by Alcohol Gas Source Method Takuya Okada1 Takahiro Saida1 Shigeya Naritsuka2 and Takahiro Maruyama1,3 1
Department of Applied Chemistry, Meijo University, Tempaku, Nagoya 468-8502, Japan
2
Department of Materials Science and Engineering, Meijo University, Tempaku, Nagoya468-8502, Japan
3
Nanomaterials Center, Meijo University, Nagoya 468-8502, Tempaku, Japan
Abstract
We demonstrated that single-walled carbon nanotubes (SWCNTs) grew from Ir catalysts by an alcohol catalytic chemical vapor deposition (ACCVD) method using a gas source-type CVD system. At an ethanol pressure of 1×10−1 Pa at 800°C, vertically aligned SWCNTs (VASWCNTs) were grown on SiO2/Si substrates. As the growth time became longer, the VASWCNT became thicker, and it reached almost 5 m for a growth time of 180 min. The Raman spectroscopy results showed that the diameters of the grown SWCNTs were mainly distributed below 1.1 nm, indicating that the SWCNTs grown from Ir catalysts had small diameters compared with those from other metal catalysts.
INTRODUCTION At present, several groups have reported high yield growth of vertically aligned SWCNTs (VA-SWCNTs) via the chemical vapor deposition (CVD) method. Hata et al. succeeded in the growth of VA-SWCNTs that were 2.5 mm thick within 10 min via the so-called “super-growth” technique [1]. The researchers used Fe catalysts on Al2O3 buffer layers for SWCNT growth and enhanced the growth rate by supplying a small amount of water to a C2H4 feedstock gas during the SWCNT growth. Other groups fabricated SWCNT forests using excited species with Fe catalysts [2, 3]. However, when Fe was used as the catalyst, the diameters of most of the VA-SWCNTs were larger than 1
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nm, and typically, they were distributed between 1 and 3 nm. VA-SWCNTs have also been reported in the SWCNT growth via CVD using Co catalysts. A University of Tokyo group performed alcohol catalytic CVD (ACCVD) using Co/Mo catalysts on quartz substrates and obtained VA-SWCNTs that were up to 20 m thick [4, 5]. Y. Homma’s group also fabricated uniform SWCNT forests that were ~350 m in thickness using Co catalysts on Al2O3 buffer layers [6, 7]; however, the radial breathing mode (RBM) peaks for the grown SWCNTs were mainly distributed below 250 cm−1, indicating that most of their diameters were larger than ~1 nm. However, for application in transistors, it is desirable to obtain semiconducting SWCNTs that have diameters less than 1 nm with a high efficiency. In this study, we performed SWCNT growth via ACCVD using Ir catalysts. Ir is one of the platinum group elements, and it belongs to the same family of Co and Rh. Generally, for a transition metal c
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