Influence of stiffness of carbon-nanotube probes in atomic force microscopy

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Abstract
We report the influence of stiffness of carbon nanotubes for probes of a scanning probe microscope on images. Multiwalled carbon-nanotube probes are fabricated by manipulation under the direct view of a scanning electron microscope. Using this manipulation, it is also revealed that a Hamaker constant of 60×10-20 J for the van der Waals attraction is for a sidewall of the nanotube and the metallic surface at a vacuum of ~10-3 Pa. The force curve measurements at a steep slope in air reveal the influence of the force acting not only on the tip of the probes but also on the wall of the tip. The origin of this effect is discussed in terms of the van der Waals attraction and the adhesive energy estimated from the force curve. This phenomenon is suppressed using a nanotube probe consisting of bundled nanotubes at the base to improve the stiffness for samples of high roughness.