Selective alignment of semiconducting single-walled carbon-nanotubes grown on quartz single crystal surfaces

Shimoyama, Iwao   ; Li, X.*; Shimada, Takashi*

It has been reported that single-walled carbon-nanotubes (SWNTs) align on several single crystal surfaces with chemical vapor deposition. In order to investigate the alignment mechanism, we measured polarization-dependent Raman spectra of aligned SWNTs formed on quartz single crystal surfaces. High- and low-frequency components in tangential vibration modes of Raman spectra, i.e., G (1590cm) and G bands (1575cm), exhibited different magnitudes of polarization dependence. High-frequency G band always showed larger polarization dependence than low-frequency G band independently of polarization configuration, resonant excitation condition, and growth condition. Base on these results, we concluded that different polarization dependences between G and G bands originated from different orientations of semiconducting and metallic SWNTs. This suggests that semiconducting SWNTs selectively align on quartz crystal surfaces.