Single-Walled Carbon Nanotube Growth in High Vacuum Using Pt Catalyst in Alcohol Gas Source Method

Abstract

Growth of single-walled carbon nanotubes (SWNTs) was carried out on SiO 2 /Si substrates at 700 C with Pt catalysts using an alcohol gas source method in a high vacuum. Scanning electron microscopy observations and Raman spectroscopy measurements showed the optimal ethanol pressure to be 1 × 10 −4 Pa, which was much smaller than that used in the SWNT growth with a Co catalyst. Raman spectra measured with various excitation wavelengths showed that the G/Si ratios of the SWNTs grown with the Pt catalyst at 1 × 10 −4 Pa was fairly larger than those grown with the Co catalyst at 1 × 10 −1 Pa, indicating that the SWNT yield of the former was higher than that of the latter, in spite of the lower ethanol pressure. These results indicate that by using the Pt catalyst, the optimal ethanol pressure was considerably reduced, compared to the conventional Co catalyst. The usefulness of Pt catalyst for SWNT growth under low pressure was demonstrated for the first time.

Low Temperature Growth of Single-Walled Carbon Nanotubes from Pt Catalysts under Low Ethanol Pressure by Alcohol Gas Source Method

“…At the growth temperature of SWNTs, those residual carbon atoms should be crystallized to hexagonal carbon network, forming carbon nanocaps on the catalyst particle surface. Previously, we discussed that the remarkable reduction of optimal ethanol pressure for Pt catalyst was due to the SWNT growth by a diffusion process of carbon atoms on the catalyst surface without dissolution into Pt [12]. We consider that the small bulk solubility of carbon atoms into Pt leads to the lower ethanol pressure necessary for the Journal of Nanotechnology 5 SWNT growth.…”

“…Recently, we grew SWNTs using Pt catalysts and showed that SWNTs could be grown even at ambient ethanol pressure of 1 × 10 −4 Pa, while keeping the yield compatible with Co catalysts at 1 × 10 −1 Pa [12,13]. However, it is desirable to reduce the growth temperature to 400…”

Growth of Single-Walled Carbon Nanotubes from Pt catalysts by the Alcohol Gas Source Method under Low Ethanol Pressure: Growth Temperature Dependence

“…The nominal thickness of Pt was 0.2 nm, which was the optimal thickness to obtain the highest SWNT yield. SWNTs were then grown with the alcohol gas source method in a UHV chamber, a type of cold-wall chemical vapor deposition (CVD) equipment [2]. Ethanol gas was supplied to the substrate surface for 1 h through a stainless steel nozzle with a hole (diameter: 0.5 nm) at the tip.…”

“…To fabricate carbon nanotube (CNT) devices in a conventional LSI process, it is desirable to grow SWNTs at low temperature under high vacuum. So far, we reported that, by using the Pt catalysts, SWNTs could be grown at 700ºC under an ethanol pressure of 10 -3 Pa, while keeping the yield comparable with that grown with Co catalyst at 10 -1 Pa [2,3]. For application to the fabrication of CNT devices compatible with present CMOS, it is important to reduce the growth temperature to below 500ºC.…”

Growth Mechanism of Single-Walled Carbon Nanotubes from Pt Catalysts by Alcohol Catalytic CVD

“…Thus far, we have reported SWCNT growth using Co catalysts in an alcohol gas source method, a type of cold-wall chemical vapor deposition (CVD) and succeeded in SWCNT growth at 400ºC by optimizing the growth condition [2]. Recently, by using Pt as catalysts, we attained SWCNT growth under an ethanol pressure of 10 -3 Pa, while the SWCNT yield was larger than those grown from Co catalysts at the growth temperature of 700ºC [3].…”