In situ tailoring and manipulation of carbon nanotubes.

Multiwalled carbon nanotubes (MWNTs), with their excellent properties, have long been considered as a model material for realizing the potential of nanotechnology. Several techniques have been developed to tailor and manipulate MWNTs, and they have shown promise in the construction of nanobalances, nanosensors, SPM probes, nanoelectronics, fuel cells, and so on. In order to achieve their full capability, MWNTs need to be modified in length, diameter, and shape to atomic-scale precision. Therefore, the synergy of various techniques and sequential operations in real time is often required. Here we report on an in situ method that combines several tailoring and manipulation techniques using an ultra-high-vacuum transmission electron microscope/scanning tunneling microscope (UHV TEM/STM) system. We demonstrate nanoscale precision in the engineering and fabricating of a MWNT with two examples; a probe for investigating single nanoparticles and a balance with singleatom mass resolution. We carried out our experiments in an ultra-high-vacuum transmission electron microscope (UHV-TEM, JEOL JEM2000V) combined with a scanning tunneling microscope (STM; built inhouse) riding on a nanopositioning system. The nanopositioning system provided coarse mechanical motions in three dimensions and the fine adjustments were performed with a piezo-tube scanner. The MWNTs (Alfa, 3–24 nm in diameter, stock #43197) were first attached to a gold knife edge electrode using the electrophoresis technique (applying a 6 MHz AC voltage of 8 V). The assembly was then loaded into the electron microscope. A pre-inserted gold STM tip was aligned and connected with a chosen MWNT under TEM observation at an operating voltage of 200 kV. The bottom of Figure 1a shows such an initial MWNT with 15 walls and about 1.87 nm inner diameter attached to the STM