Carbon-nanotube tips for scanning probe microscopy: Preparation by a controlled process and observation of deoxyribonucleic acid

We report a controlled process to make carbon-nanotube tips for scanning pr obe microscopes. The process consists of three steps: (1) purification and alignment of carbon nanotubes using electrophoresis, (2) transfer of a sing le 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 c arbon deposition. Nanotube tips fabricated using this procedure exhibit str ong adhesion and are mechanically robust. Finally, the performance of these tips is demonstrated by imaging the fine structure of twinned deoxyribonuc leic acid with tapping-mode atomic force microscopy in air. (C) 1999 Americ an Institute of Physics. [S0003-6951(99)00226-0].