Direct Observation of the Strong Interaction Between Carbon Nanotubes and Quartz Substrate

We present a chemical vapor deposition (CVD) method for the growth of uniform single-walled carbon nanotube (SWNT) arrays on a stable temperature (ST)-cut single crystal quartz substrate using a mixture of methanol and ethanol as carbon source. It is found that introducing methanol during the growth can improve the density and the length of the well-aligned SWNTs in the arrays as well as increase the SWNT/quartz interaction. Obvious "up-shifts" of G-band frequencies in the Raman spectra have been found for the aligned SWNTs. A well-designed control experiment shows that the G-band "up-shifts" originate from the strong interaction between SWNTs and the quartz substrate. It is believed that exploring this interaction will help to elucidate the growth mechanism; ultimately, this will help realize the promise of controlling the chirality of SWNTs.