Nanoengineering of Carbon Nanotubes and the Status of its Applications
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Nanoengineering of Carbon Nanotubes and The Status of Its Applications Yoshikazu Nakayama and Seiji Akita Department of Physics & Electronics, Osaka Prefecture University, Sakai, Osaka 599-8531, Japan ABSTRACT We have developed a well-controlled method for manipulating carbon nanotubes. The first crucial process involved is to prepare a nanotube array, named nanotube cartridge. We have found the ac electrophoresis of nanotubes by which nanotubes are aligned at the knife-edge. The nanotubes used were multiwalled and prepared by an arc discharge with a relatively high gas temperature. The second important process is to transfer a nanotube from the nanotube cartridge onto a substrate in a scanning electron microscope. Using this method, we have developed nanotube tips and nanotube tweezers that operate in a scanning probe microscope. The nanotube probes have been applied for observation of biological samples and industrial samples to clarify their advantages. The nanotube tweezers have demonstrated their motion in scanning-electron-microscope and operated to carry nanomaterials in a scanning probe microscope.
INTRODUCTION It is well known that carbon nanotubes[1] have unique structure and properties which are quit suitable for probes used in a scanning probe microscope (SPM). Conventional SPM probes are made of Si or Si3N4 and have shapes of a pyramid or cone with a tip radius of curvature of 10 nm or often much larger. On the other hand, nanotube probes have following advantages. (1) Small tip radii of curvature (the minimum value is ~ 0.5 nm) significantly improve their lateral resolution. (2) High aspect ratios of 10~103 provide the ability to probe the abrupt height transitions with high fidelity. (3) Tips of nanotubes can be cut and chemically functionalized to be used as a probe for a chemical force microscope.[2] (4) Nanotubes whose tip has a small particle of magnetic metal are used as a probe for a magnetic force microscope.[3] These probes have also operated with a high resolution due to the high aspect ratios. (5) Nanotubes are mechanically flexible and can be elastically buckled without damage.[4-7] Thus nanotube probes are robust and will not be broken off by an accidental crash on a sample surface, whereas conventional probes are easily chipped. The elastic buckling of nanotubes also limits the maximum force that can be applied to a sample, which can prevent damage to delicate organic and biological samples. (6) Both ends of nanotubes are generally capped, when they are prepared by an arc discharge method. These caps are so chemically and physically stable that nanotube probes will have a long life (small wearing degree) and can be used for nanoprocess such as deposition and etching using a SPM. In order to fabricate nanotube probes, the attachment techniques of a nanotube onto a conventional Si tip under the observations of an optical microscope[4] and a scanning electron microscope (SEM)[6,7] have been adopted. The growth of a nanotube from a Si tip has also been examined as a mass-production process.[
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