| 研究概要 |
This year, we studied and published a paper entitled "Direct observation of zipper-like wall-to-wall coalescence of double-wall carbon nanotubes" on an international journal CARBON 71 (2014) 159-165. This work, for the first time, demonstrates that detailed in situ TEM observation of reactions dynamics/phase transformations is possible under extreme high temperature ～2000℃. This achievement is enabled by utilizing carbon nanotube network as a sample heater and supporting stage with micrometer size. On account of resistive Joule heating, carbon nanotube heater is heated up to very high temperature leading to high temperature reactions/transformations. The very much limited heating-induced thermal drift by using carbon nanotubes and excellent thermal ability of carbon nanotubes contribute most to the successful direct observation wall-to-wall coalescence of double-wall carbon nanotubes (DWCNTs). Our study provides a useful and feasible technique for reliable in situ TEM observation of reaction dynamics/phase transformations compatible with extreme high temperature (> 2000℃).
Another study is regarding the fundamental study of effect of inter-layer coupling on the electronic structures in one-dimensional space. This time, individual free-standing DWCNTs are used and the inter-layer coupling effect on optical transition energies of individual DWCNTs are addressed. Again, in situ TEM observation is used for obtaining the key structural chiral indices of individual free-standing DWCNTs, whereas Rayleigh scattering spectroscopy is used for probing the optical transition energies. We found that inter-layer coupling effect is strong in the one-dimensional DWCNT system : most of the transition energies are downshifted compared with pristine single-wall carbon nanotube and the degree of shifts depends on the electronic types of the two tubes.
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| 今後の研究の推進方策 |
Initiated by celebrated- graphene research, two-dimensional transition-metal dichalcogenides (TMDCs), such as MoS_2, WS_2 etc., has recently attracted tremendous research attention in the field of materials science owing to their unique electronic structures. In particUlar, semiconducting TMDCs possess direct bandgap in the monolayer form, which makes them promising in optoelectronic device applications. Two-dimensional NbS_2 nanosheets, which are superconductor in bulk, on the other hand, have not been explored very well. We proposea direct chemical vapor deposition (CVD) growth of NbS_2 nanosheets on Si/SiO_2 substrates and the exfoliated hexagonal boron nitride flakes. Structure of grown NbS_2 will be characterized using Raman spectroscopy and microscopy including SEM and AFM. We also want to measure the transport properties of NbS_2 nanosheets.
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