Carbon nanotube tips for a scanning probe microscope: their fabrication and properties

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.