High lateral resolution imaging with sharpened tip of multi-walled carbon nanotube scanning probe

We report a tip sharpening process for multiwalled carbon nanotube (MWCNT) scanning probes and demonstrate its application in high lateral resolution imaging. The sharpening of the tip is an in-situ process employing the atomic force microscope. The method involves current-induced oxidation in ambient atmosphere by locally stripping away the outer layers at the very tip of the MWCNT. This process requires an applied voltage in the 2-3 V range, which is lower than that required for shortening the nanotube. Direct scanning microscopic data reveal sharpened tips with a radius of curvature normally less than 5 urn. Multiple scan experiments show that the sharpened tips undergo no degradation in image quality, suggesting that the sharpened tips are very robust. Our unique fabrication process for producing a robust multiwalled CNT scanning probe coupled with the tip sharpening method has demonstrated the development of a universal probe for high aspect ratio as well as high lateral resolution imaging applications.