Applied Physics

Tip Top Assembly

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Science  25 Jun 2004:
Vol. 304, Issue 5679, pp. 1877
DOI: 10.1126/science.304.5679.1877c

Scanning probe microscopy uses the lateral movement of a sharp probe across a specimen and is used to characterize surface properties. For many applications, carbon nanotubes make ideal probe tips because they are mechanically robust but will buckle elastically instead of damaging the surface. They also can detect deep trenches and can be functionalized for simultaneous probing and chemical sensing. However, sticking a nanotube onto the end of a probe is a hit-or-miss process, and attempts to grow them in the right place are not yet reliable.

By combining standard silicon micromachining techniques with nanoscale controlled synthesis, Ye et al. fabricated 244 probe tips on a single 4-inch wafer. Catalyst particles are deposited by electron beam lithography at select locations and protected from etching. The rest of the cantilever is patterned and etched, and the protection is then removed from the catalyst particles. The nanotubes are then grown using plasma-enhanced chemical vapor deposition, where the plasma induces an electric field that directs the growth of the nanotubes parallel to the field; no trimming or post-synthesis finishing of the nanotubes is necessary. — MSL

Nano Lett. 10.1021/nl049341r (2004).

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