High-Yield Assembly of Individual Single-Walled Carbon Nanotube Tips for Scanning Probe Microscopies

The structural and mechanical properties of single-walled carbon nanotubes (SWNTs) make them ideal tips for scanning probe microscopies such as atomic force microscopy (AFM). However, the ideal nanotube probe, which corresponds to an individual SWNT, has been difficult to produce in high yield. To overcome this difficulty, a straightforward and easily implemented method that enables very high-yield fabrication of individual SWNT probes has been developed. This new method is based upon the observation that microfabricated tips can "pick up" vertically aligned SWNTs grown from planar substrate surfaces. Substrates with isolated, vertically aligned SWNT are first prepared by chemical vapor deposition and then imaged with commercial microfabricated silicon AFM tips. The silicon tips pick up individual SWNTs from the substrate during imaging to create well-aligned SWNT probes. The SWNT tips have been etched using a procedure that allows variation of the nanotube length with 2 nm control. Studies of gold nanocluster standards demonstrate that these individual SWNT tips are capable of high resolution and robust imaging in air and fluids, and thus these tips are expected to open up new opportunities in nanoscale science and technology.