Development of Fabrication Method of High Aspect Ratio Nanoscale Pit Using Carbon Nanotube Probe

We developed a fabrication method for high-aspect-ratio nanoscale pits 60 nm in diameter by using a multi-wall carbon nanotube (MWNT) as a scanning tunneling microscope probe. We used a single-wall carbon nanotube (SWNT) to fabricate a pit whose diameter is in the single nanometers. We investigated the application the pull-method to SWNT probe manufacturing, under various manufacturing conditions. In addition, we investigated the relationship between the diameter of carbon nanotube (CNT) and fabricated pit in order to determine the diameter of a pit fabricated using a SWNT probe of the minimum diameter. The nanoscale pits were produced in highly oriented pyrolytic graphite. SWNT probes were synthesized using a mixed dispersion liquid with both MWNT and SWNT. SWNTs were attached to the apex of the MWNT in this process. The success rate for synthesis was about 17 %. CNT probes 7, 10 and 40 nm in diameter used under the conditions of a bias voltage of 4 V, tunnel current of 1 nA and fabrication time of 180 s, yielded fabricated pits with the respective diameters of 9, 14 and 45 nm. From the results, it is thought that a fabricated pit is 2 nm greater in diameter than the CNT that fabricates it. If a SWNT that is 0.4 nm in diameter, the minimum diameter, is used in this fabrication method, the diameter of the fabricated pit is expected to be 2.4 nm. This demonstrates that STM fabrication using CNT probes can be useful in fabricating single nanoscale structures by controlling the diameter of the CNT.