Materials Science

Tubular Switches

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Science  26 May 2006:
Vol. 312, Issue 5777, pp. 1107
DOI: 10.1126/science.312.5777.1107a

The mechanical strength and resilience of carbon nanotubes (CNTs) have prompted investigations of their use in applications ranging from fibers to molecular switches. A less commonly exploited property is the unusually low sliding friction characterizing the relative motion of the concentric hollow cylinders that make up double- or multiwalled CNTs—an action analogous to the extension or contraction of a collapsible spyglass.

Deshpande et al. have taken advantage of this property in fabricating nanotube-based voltage-gated switches. First, they mounted low-resistance (10 to 20 kilohms) CNTs on gold leads over a silicon gate region. Application of a 4.5-V bias across the leads cleaved the tubes in two, leaving an insulating gap of 5 to 20 nm in the middle and thereby creating an “off” state. Subsequent application of a higher bias (5 to 10 V) reestablished electrical contact, creating a conductive “on” state. The authors attributed this behavior to a charge-induced sliding of the inner tubes through the outer shells and across the gap, an explanation supported by the observation that the outer shells remained rigidly fixed to the leads. For double-walled CNTs, successive application of a 9-V bias across the leads and a 110-V gate potential cycled the device between on and off states. — PDS

Nano Lett. 6, 10.1021/nl052513f (2006).

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