We have developed nanotweezers consisting of carbon nanotubes that will operate in an atomic force microscope. The two nanotubes were attached on the metal electrodes patterned on a conventional Si tip and their fixations were made by carbon deposition. These processes were made under the view of a scanning electron microscope. The application of a dc voltage to the two nanotube arms induces their movement to approach each other. The numerical simulation by taking into account the balance between the electrostatic attraction and the bending moment of the nanotubes well explains the motion of the nanotube arms.
Helical carbon nanocoils exhibit excellent field emission properties, and are thus expected to be applicable as electron emitters in field emission displays. We have synthesized carbon nanocoils with different diameters by the catalytic thermal decomposition of acetylene using iron-indium-tin-oxide catalysts. It is found that the turn-on voltage is decreased by decreasing the average diameter of the grown carbon nanocoils. The turn-on voltage of as low as 30 V at the electrode gap of 130 mm was achieved when the coil diameter is decreased to 60 nm. The calculation for the concentration of the electric field on the coil surface has been performed using a finite element method. It is found that the strength of the electric field around the top ring of a coil is increased with the decrease of the tubular diameter of the coil and has a similar value as that at the tip of a carbon nanotube, suggesting that the efficiency of the field emission from nanocoils would be higher than that from nanotubes. These results can explain the high stability of field emission from carbon nanocoils.
100-µm-long vertically aligned multiwall carbon nanotubes were grown in 1 s. A thermal chemical vapor deposition method at 700°C was used with a catalyst of iron films and a carbon source gas of acetylene diluted with helium. This study revealed a novel rapid growth mode that appears in the beginning of chemical vapor deposition when the rate of increase in the concentration of carbon source gas is high at the substrate. This new growth mode, which precedes a normal growth mode, provides well-crystallized and straight nanotubes.
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