|AVS 54th International Symposium|
|In-situ Electron Microscopy Topical Conference||Monday Sessions|
|Session:||Dynamics of Nanostructures|
|Presenter:||S. Takeda, Osaka University and CREST-JST, Japan|
|Authors:||S. Takeda, Osaka University and CREST-JST, Japan
H. Yoshida, Osaka University and CREST-JST, Japan
Y. Homma, Tokyo University of Science and CREST-JST, Japan
|Correspondent:||Click to Email|
Solid-gas reaction is a fundamental process of the synthesis of various nanomaterials. For example, carbon nanotubes (CNTs), one of the most promising nanomaterials for future nanotechnology, are grown from metal catalysts in gases containing carbon. In order to apply nanomaterials to future nanodevices, their growth mechanism needs to be better understood at the atomic level. In this respect, transmission electron microscopy (TEM) equipped with an environmental cell (E-cell), which is occasionally called environmental-TEM (ETEM), is one of the best techniques. We have examined the importance of ETEM for the study of the growth mechanism of CNTs via computer simulation of high resolution ETEM images of CNTs under an actual growth condition.1 Moreover, several pioneer works have revealed various solid-gas reactions by ETEM. In this work, the growth process of CNTs has been actually observed by a newly designed ETEM (FEI Tecnai F20 equipped with E-cell) which has an information limit of nearly 0.15 nm even in 10 mbar N2 gas. CNTs were grown by catalytic chemical vapor deposition (CVD) of methane, acetylene and so on. The metal catalysts, such as Co and Ni were deposited on a silicon substrate with surface oxide. In our CVD process, the pressure of gases ranges from 1 to 103 Pa and the temperature is set at 600 to 800°C. We investigate the growth mechanism and dynamics of CNTs via in situ observations of both catalyst nanoparticles and CNTs. As an example, we have succeeded in the observation of the growth of a short multi-walled CNT (MWNT). During the growth of the MWNT, the shape of the catalyst changes drastically. Before the growth, the shape of the catalyst is a sphere. Then, the shape changes into an elongated shape. At a certain moment, the catalyst lifts off the substrate and contracts to a spherical shape. At the same time, a MWNT grows. The details including other in situ observations of CNT growth will be presented at the meeting.
1 H. Yoshida and S. Takeda, Phys. Rev. B 72, 195428 (2005).