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Sharper tips for microscopy

Scanning microscopy is a common tool used by researchers to examine minute details of samples such as chips used in computers and electronics. The quality of a scanning tunneling microscope image depends on the size and shape of a very small metal probe. To produce very sharp tips that resist wear, NSF-funded researchers created field-directed sputter sharpening (FDSS).

During FDSS, a beam of gaseous ions bombards a probe while a voltage is applied to the tip. The voltage creates an electric field that deflects the ion beam. The sharper the tip, the more the ions are deflected, resulting in a probe that is increasingly eroded around the tip, but not at the tip itself. By this self-enhancing process, probes made of tungsten, platinum-iridium alloy or tungsten coated with ultra-hard hafnium diboride can be reproducibly sharpened to a 1 to 4 nanometer radius of curvature at the tip.

Through parallel processing FDSS can sharpen hundreds of probes simultaneously. The process can also sharpen or repair probes that dull or break during use. A startup company, TipTek, LLC, is commercializing the technology with the help of NSF's Small Business Innovation Research (SBIR) program. 

Images (1 of )

  • a platinum-iridium tip before (left) and after (right) sharpening
  • comparison of probe sharpening using conventional and FDSS processing
A platinum-iridium tip before (a) and after (b) sharpening.
Joseph W. Lyding, University of Illinois at Urbana-Champaign
Probe patterns (a) and with FDSS processing (b).
Joseph W. Lyding, University of Illinois at Urbana-Champaign

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