AVS 49th International Symposium
    Nanotubes: Science and Applications Topical Conference Monday Sessions
       Session NT-MoM

Paper NT-MoM9
High-resolution Transmission Electron Microscopy Study of Catalyst Metal Particle at the Tip of Carbon Nanotube

Monday, November 4, 2002, 11:00 am, Room C-209

Session: Nanotubes: Growth and Characterization
Presenter: T. Ikuno, Osaka University, Japan
Authors: T. Ikuno, Osaka University, Japan
S. Takahashi, Osaka University, Japan
K. Kamada, Osaka University, Japan
S. Ohkura, Osaka University, Japan
M. Katayama, Osaka University, Japan
T. Hirao, Osaka University, Japan
K. Oura, Osaka University, Japan
Correspondent: Click to Email
Carbon nanotubes (CNTs) have been attracted much attention due to their fundamental research interest and potential applications. Control of alignement of CNT is essential for applications such as field emission display (FED), quantum wire, and field effect transistor. For FED application, to concentrate electric field at the CNT tip, vertically aligned CNT is desirable. On the other hand, lateral alignment is necessary for nanodevice application. In this study, we have performed high-resolution transmission electron microscopy (TEM) analysis focused on the metal particle at the tip of CNT to clarify correlation between growth mechanism of CNT and crystallography of metal catalyst. Specimens are randomly and vertically aligned CNTs which are synthesized on Ni (50 Å)/ Si (100) substrates by thermal chemical vapor deposition and RF-plasma CVD, respectively. From TEM observation of Ni particle at the tip, it was found that randomly CNT (bamboo-like CNT) has spherical Ni particle at the tip, and vertically CNT (multi-wall CNT) has a wedge shape with flat facets. Both particles were found to be monocrystalline. The crystalline orientations of the particles were also investigated. The axial directions of the vertically CNT are mainly parallel to the <111> and <311> direction of Ni. From high-resolution TEM image of Ni / CNT interface, graphite layers were formed along the ridge line of Ni particle for randomly CNTs, whereas they were formed along specific planes parallel to the growth direction for vertically CNTs. On the basis of these results, we will discuss the mechanism of alignment process associated with growth front of graphite layers precipitated from the Ni particle. This work was performed with Japan Fine Ceramic Center under the Frontier Carbon Technology Project of the New Energy and Industrial Technology Development Organization.