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Microscope's misleading tips.

Although atomic-force microscopes reveal atomic-scale details not seen with many other imaging techniques, Swiss physicists warn that those details may not always be real.

These microscopes map the landscape of a surface by monitoring fluctuations in the forces between atoms in a very fine imaging tip and those in the material under investigation. Scientists have used the microscopes to study active molecules and to move molecules around (SN: 3/17/90, p.165). But P. Grutter and colleagues at the University of Basel in Switzerland have discovered that imperfections in these tips can lead to spurious results.

In the June 1 APPLIED PHYSICS LETTERS, the researchers show how one atomic-force microscope tip misrepresented the topography of a diamond film. Examination with a scanning electron microscope and with a scanning tunneling microscope revealed that the film surface consists of sharp tips and steep facets formed by oriented crystals. But the atomic-force microscope depicted the surface as truncated pyramids. The microscope's tip had that same squared-off shape.

Tips are etched in batches from silicon wafers. The scientists found three flawed tips in a batch of 10 and concluded that dust or imperfect processing led to the bad tips. They suggest that scientists characterize and calibrate tips before using them.
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Title Annotation:imperfections can lead to errors
Publication:Science News
Article Type:Brief Article
Date:Jun 13, 1992
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