Electric-field-enhanced growth of carbon nanotubes for scanning probe microscopy

The influence of an electric field on carbon nanotube (CNT) growth using hot-filament chemical vapour deposition is investigated. Acetylene (C2H2) gas diluted with hydrogen is used as the source gas for the growth of CNTs, and a bias voltage of -300 V is applied to the sample stage during growth. The silicon substrate onto which the CNT is grown is prepared by sputtering a thin catalysed metal (Ni) film onto the surface, and the CNT is selectively grown from the tip of a silicon protrusion on the substrate. It is found that the application of a high electrostatic field with a negative substrate bias enhances the growth of CNTs in this situation. This effect is successfully applied to the fabrication of a CNT tip supported by a silicon cantilever for use in scanning probe microscopy.