Manipulation of Carbon Nanotubes
In an Electron Microscope
Two Nanomanipulators were installed inside of an field-emission
scanning electron microscope (FE-SEM, JEOL JSM-6700F) for moving, bending,
cutting, and biasing of nanostructured materials. In situ characterizations
of electron beam-induced junctions between the tip and carbon nanotubes
were carried out and a carbon-nanotube transistor on pre-patterned metal
electrodes was produced.
The diameter of the produced Carbon Nanotubes (CNT)
ranges from 30 to 50 nm and the tube is metal-particle free. A fragment
of soot was brought into a specimen chamber. Fragments usually revealed
nanotubes sticking out in all directions, as shown in Fig. 1.
It is possible to fix a single carbon nanotube strand at the tip
of one manipulator in the following way:
After attaching the single nanotube to the tip, the manipulator was moved away from the fragment of nanotubes to pull this single tube out of its bundle.
A carbon-nanotube transistor is constructed on patterned electrodes, where four electrodes are aligned in parallel within a mm. In order to place an individual CNT on those electrodes, first a single strand of nanotube was moved onto the electrodes. A new CNT bundle on the tip of the second Nanomanipulator was prepared by similar EBID method to form a second sharp tip. This allows to press a single strand of nanotube placed already on the electrode without damage, as shown in Fig. 2. The other manipulator was then pulled out carefully, which left a single strand of the nanotube successfully on the metal electrodes, as shown in Fig. 3. It turned out that this approach with two maneuverable manipulators can save labor time and reduce the trial and error during the manipulation and could be applied for any type of interconnections between nanostructured materials and macroworld characterization systems and even in cautious MEMS fabrications.
A CNT was attached at an AFM tip, as shown in Fig. 4. An electrostatic
force exerted between the nanotube and AFM tip attracted the nanotube
towards the AFM tip and the nanotube abruptly stuck to the tip. When the
nanotube was misaligned to the tip axis, it was carefully dragged to align
along the tip axis by the counter manipulator. After locally spot-welding
with the EBID a single nanotube was well adhered at the AFM tip, see Figure
The conductivity trough a CNT and its junctions is measured by
connecting two manipulators through a single strand of the CNT, as shown
in Fig. 5. The I-V curve is demonstrated in Fig. 6 and the characteristics
of the I-V curve is under study.