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Extra long nanotubes by CVD

Shengdong Li and other researchers of University of California, presented a growth procedure for nanotubes, long enough to behave as electrical nano-resonators with resonant frequencies in the GHz range using CVD.
Lindberg furnace
CVD was carried out using a 3” Lindberg furnace. This furnace is a general purpose atmospheric annealing system. Its operating temperature range is 200-1100C in atmosphere, N2, O2 or 5% forming gas (H2/N2) ambients. The quartz furnace tube can handle substrates from pieces through 4"/100mm. Substrates are loaded and unloaded in a quartz boat (Thermo Electron Corporation makes such furnaces).
CVD procedure
A gas recipe that favors the synthesis and essential for the success of this experiment to make ultra-long and high quality SWNTs was adopted by them. Acetylene, known to produce MWNTs at 700-800 C as the carbon source and high purity methane were used to favor the production of SWNTs. H2 was used to suppress the deposition of amorphous carbon and thus maintain the high purity of as obtained SWNTs. After heating up the 3” quartz tube to 900 C under an argon atmosphere, the argon was replaced by a co-fow of 1000 sccm methane (99.999%) and 200 sccm hydrogen for 12 minutes. All the process were performed under manual control, including purging Ar, increasing the temperature, flowing active gases and cooling down the system in the Ar atmosphere again to get ultra-long and high quality SWNTs.

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