科研之友
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摘要
We report in this paper a convenient and effective method to identify the structures of superlong well-aligned single-walled carbon nanotubes (SWNTs) via the combination of electrodeposition of Ag particles on the SWNTs with Raman spectroscopy. The suitable density and the visibility of the Ag-deposited long nanotubes make it possible to acquire Raman spectra from isolated individual long nanotubes very easily. The results reveal that the superlong well-oriented SWNT arrays on SiO(2)/Si wafer fabricated by EtOH-CVD using Fe/Mo nanoparticles as catalyst exhibit a lower percentage of metallic SWNTs (m-SWNTs) (similar to 5%). Among other SWNTs, similar to 62% are semiconducting SWNTs (s-SWNTs) and similar to 32% are so-called quasi-insulators, which are believed to be caused inevitably by the defects during growth process. Small amount of nanotubes are so-called quasi-metallic. Furthermore, the structural uniformity of the long SWNTs can be also evaluated by the deposition of Ag along the length and Raman spectroscopy. Besides, on the basis of the in situ laser irradiation on individual SWNTs, it was found that s-SWNT is more stable than m-SWNT. The m-SWNT can be changed to s-SWNT under laser beam with an appropriate conditions, providing a facile method to generate alternative m- and s-SWNT multiple junction on one individual long SWNT, which may have special electrical properties and potential applications in nanoelectronics.
