ABSTRACT
The experiments were carried out in a JEM-3100FEF (JEOL) TEM using a “Nanofactory Instruments AB” STM-TEM holder [8]. As shown in the schematics of Fig. 9.1, a multiwalled CNT protruding from the edge of a gold wire was approached to a W tip that was delicately driven by a piezo-tube. After the end-to-end physical contact was established (Fig. 9.2a), a positive bias applied to the gold wire was slowly increased until the W tip started to locally melt (at the contact area) due to induced Joule heating. As shown in Fig. 9.2b, both the tip-end and side surfaces of W tip become smooth and clean due to Joule heating-induced in situ annealing effects. A passing current exceeding 150 mA drives the further structural transformation, during which the W tip and CNT fuse together (Fig. 9.2c). The graphitic shells of the CNT head have been dissolved into the W tip during the fusion process, which causes the end of W to swell and to show the optical contrast different from the right-handside pristine region (the arrow in Fig. 9.2c indicates the apparent contrast boundary). As the graphitic shells of the CNT continuously dissolve into the W tip, the carbide region within the W tip expands
Figure 9.1 Schematic diagram of the experimental setup inside TEM. Side contact with gold wire and end-to-end contact with tungsten tip are established for the two CNT ends. Reproduced from Adv. Mater., 22, pp. 9398 (2010). Copyright © 2010, Wiley [8].
