Berlin 2018 – scientific programme

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O: Fachverband Oberflächenphysik

O 80: Poster: Scanning Probe Techniques - Method Development

O 80.4: Poster

Wednesday, March 14, 2018, 18:15–20:30, Poster A

Etching tungsten nanotips using nitrogen gas in a field ion microscope — •Alexander Ihle, Sören Zint, Daniel Ebeling, and André Schirmeisen — Institute of Applied Physics, Justus Liebig University Giessen, Germany

Ultra-sharp tungsten nanotips are used in various applications. For low temperature atomic force microscopes, e.g., where quartz tuning forks are used as sensors nanotips are often fabricated from thin tungsten wire. To achieve ultimate lateral resolution or for functionalizing the tips with single CO molecules extremely sharp tips with radii in the nm or even in the sub-nm regime are needed. In 2006 Rezeq et al. [1] introduced a new method for tip fabrication, where electrochemically etched tungsten tips are further sharpened in a subsequent step by field-assisted etching with nitrogen gas. Therewith, tip radii below 1 nm can be reproducibly fabricated. Here, we are analyzing the effect of the nitrogen pressure on the tip etching process. To precisely determine the tip radius we use the so-called feature size mapping method [2]. Our measurements reveal that the tip radius decreases linearly in time for various nitrogen gas pressures in a range between 5.6 x 10-8 mbar and 5 x 10-6 mbar. Therefore, the etching rate at a specific pressure is constant. Furthermore, it is demonstrated that the etching rates increase linearly with higher nitrogen pressures, which allows us to precisely estimate the process time.

[1] Rezeq et al. The Journal of Chemical Physics 124, 204716 (2006)

[2] Zint et al. Phys. Rev. B 90, 241413 (2014)