We report a controlled process to make carbon-nanotube tips for scanning probe microscopes. The process consists of three steps: (1) purification and alignment of carbon nanotubes using electrophoresis, (2) transfer of a single aligned nanotube onto a conventional Si tip under the view of a scanning electron microscope, and (3) attachment of the nanotube on the Si tip by carbon deposition. Nanotube tips fabricated using this procedure exhibit strong adhesion and are mechanically robust. Finally, the performance of these tips is demonstrated by imaging the fine structure of twinned deoxyribonucleic acid with tapping-mode atomic force microscopy in air.

We report a well controlled method to make carbon nanotube tips for a scanning probe microscope (SPM). A multiwalled carbon nanotube, which is purified by the electrophoresis, is transferred onto a conventional Si tip for a SPM using a scanning electron microscope (SEM) equipped with two independent specimen stages. The nanotube is fixed on the Si tip by electron beam deposition of carbon. A force curve measurement of nanotubes using the nanotube tips in the SEM reveals that Young's modulus of a nanotube of 20 nm diameter is 1.1 TPa and the fixing of nanotubes by the carbon deposit is effective. The nanotube tips are used to image plasmid deoxyribonucleic acids on mica by tapping mode. The average resolution by using the nanotube tips is about two times higher than that by the best Si tips.

Articles you may be interested inMagnetic force microscopy measurements in external magnetic fields-comparison between coated probes and an iron filled carbon nanotube probe Metal capped carbon nanotubes, prepared by catalytic decomposition of benzene, have been applied as a magnetic force microscope tip. The particles at the end of nanotubes were about 35 nm in diameter, which were found to be Ni 3 C from the electron diffraction pattern. The other end of the nanotubes was attached on the tip of conventional Si probes. The magnetization of the particles was carried out parallel to the nanotube axis by applying a pulsed magnetic field of 12.5 T. We demonstrate the performance of these carbon nanotube probes by imaging the stored signal in magnetic recording media with magnetic force microscopy.

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.

The linear response theory has been used to calculate the dielectric response of a tunnelling quantum dot superlattice to an external perturbation using a simple model, including the many-body effect, in a reasoned manner. Explicit analytical results for the dispersion relation are derived. The transition behaviour from a one-dimensional chain to a quasi-two-dimensional tunnelling semiconductor superlattice is discussed.