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

Growth of single-walled carbon nanotubes (SWNTs) was carried out on SiO2/Si substrates with Pt catalysts at 400, 450, and 700°C under various ethanol pressures using an alcohol gas source method in a high vacuum, and the grown SWNTs were characterized by scanning electron microscopy (SEM) and Raman spectroscopy. Irrespective of the growth temperature, both G band and RBM peaks were observed in the Raman spectra under the optimal ethanol pressure ( Pa), indicating that SWNTs grew below 450°C from Pt. At 400°C, both average diameter and diameter distribution were drastically reduced, and those were fairly smaller and narrower, compared to those for SWNTs grown with Co. 1. Introduction Single-walled carbon nanotubes (SWNTs) have attracted great interest for nanometer-scale devices, such as field effect transistor (FET) [1, 2] and LSI interconnects [3, 4]. Among a lot of methods for SWNTs growth, catalytic chemical vapor deposition (CVD) has several advantages such as high yield production, low growth temperature, and good controllability of SWNT position and diameter. As a result, CVD is widely used for the SWNT growth at present [5]. To realize SWNT-based devices compatible with LSI manufacturing processes, SWNT growth by CVD under low pressure is significant since the SWNT growth under a high vacuum prevents surface contamination during the fabrication process. In addition, SWNT growth in a high vacuum is useful for in situ observations during the growth, such as scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Thus far, SWNT growth using CVD under low pressure has been performed by several groups. For the purpose of in situ observations, Homma et al. carried out carbon nanotube (CNT) growth by low-pressure alcohol CVD at 1–20？Pa [6, 7]. Shiokawa et al. succeeded in growing SWNTs by a cold-wall CVD using ethanol at 0.05？Pa in an ultra-high vacuum (UHV) chamber [8]. Our group also achieved SWNT growth at an ambient ethanol pressure of 1 × 10？4？Pa with a Co catalyst, adopting a gas source method in a UHV chamber, a type of cold-wall CVD. However, the SWNT yield decreased considerably, because the growth temperature had to be reduced to 400°C to obtain SWNTs under low ethanol pressure [9–11]. 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°C for application to fabrication of SWNT devices compatible with