AVS 47th International Symposium
    Nanotubes - Science and Applications Monday Sessions
       Session NM+NS-MoA

Paper NM+NS-MoA9
Study on Field Emission Mechanism of Carbon Nanotube using High-resolution Electron Microscopy

Monday, October 2, 2000, 4:40 pm, Room 309

Session: Carbon Nanotubes: Nanoelectronics and Field Emission
Presenter: T. Kuzumaki, The University of Tokyo, Japan
Authors: T. Kuzumaki, The University of Tokyo, Japan
H. Ichinose, The University of Tokyo, Japan
Y. Horiike, The University of Tokyo, Japan
Correspondent: Click to Email
In investigation of the relation between the tip structures and the field electron emission characteristics of the nanotube, we have found that the nanotube tip is plastically deformed during cold emission. Our studies with a high-resolution transmission electron microscope reveal that the deformation occurred at the local domain containing an isolated pentagonal carbon ring in the polyhedral cap and a convexity is formed along the electric field direction. Semi-empirical molecular orbital calculations show that the pentagon and heptagon pair is introduced into the hexagonal network with a pentagonal carbon ring by heterogeneous nucleation mechanism, and the resulting convexity structure is formed at the tip. The electron emission characteristics of the closed nanotube show that the threshold voltage was high for the first run and the current increased quickly. After the second run the emission started at rather lower voltage and increased gradually. Fowler - Nordheim (F-N) plots show that the first run does not show a straight line. There is no marked change to gradient the second run. The decreasing of the threshold voltage after the second run is possibly due to the structural change of the nanotube tip. The opened nanotubes also show the notable structural change at the tip. The deformed structure can be explained by introducing sp@super 3@ - like line defects in the hexagonal carbon network. In the opened nanotube, the gradient of the F-N plots is decreasing corresponding to change of structure. The formation of the emission site contributes greatly to the stable and highly efficient electron emission from the nanotubes.