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 correspon ds to an individual SWNT, has been difficult to produce in high yield. To o vercome this difficulty, a straightfoward and easily implemented method tha t enables very high-yield fabrication of individual SWNT probes has been de veloped. This new method is based upon the observation that microfabricated tips can "pick up" vertically aligned SWNTs grown from planar substrate su rfaces. Substrates with isolated, vertically aligned SWNT are first prepare d by chemical vapor deposition and then imaged with commercial microfabrica ted silicon AFM tips. The silicon tips pick up individual SWNTs from the su bstrate during imaging to create well-aligned SWNT probes. The SWNT tips ha ve been etched using a procedure that allows variation of the nanotube leng th with 2 nm control. Studies of gold nanocluster standards demonstrate tha t these individual SWNT tips are capable of high resolution and robust imag ing in air and fluids, and thus these tips are expected to open up new oppo rtunities in nanoscale science and technology.