In situ cyclic telescoping of multi‐walled carbon nanotubes

Abstract

In this work, we perform an in‐depth study of the cyclic telescoping of multi‐walled carbon nanotubes (MWCNTs) inside a transmission electron microscope. The nanotubes are observed in real time, while simultaneously measuring their electrical properties. To date, examples of in situ TEM nanotube telescoping have remained few in number due to the highly specialized equipment and technical expertise required. Experiments were conducted by first ‘sharpening’ a MWCNT by approaching it with a piezo‐controlled tungsten tip and applying a voltage pulse. This results in controlled and localized peeling of the outer walls, giving rise to a telescope structure. The exposed core is then contacted with the tungsten tip and reproducibly pulled out then re‐inserted, while measuring conductance behavior at each movement step. Figure 1 shows an example of in situ telescoping of a MWCNT in real time. Results demonstrate that an electrical current can be maintained for multiple in‐and‐out cycles (up to 11 cycles have been tested to date), and for telescoping distances of up to 650 nm. This is exemplified in Figure 2. The systems display complex conductance behavior, with of some MWCNT telescopes demonstrating improved conduction (and current) as a function of the number of cycles, while for most these properties diminish. Control experiments have been conducted to investigate the effect of the electron beam on the behavior of the MWCNTs, and have indicated that changes in conductance behavior are not strongly influenced by the imaging process under normal beam conditions. One potential application for these structures is use as flexible electrical contacts, which allow for relative motion of the two electrodes, while maintaining electrical conduction. The authors would like to acknowledge funding as provided by the National Institute for Materials Science (NIMS), through the International Center for Materials Nanoarchitectonics (MANA).