X-ray imaging

Baby steps

With improved optics and intensity, X-ray reflectivity can now provide subnanometre vertical resolution of surface features.

Credit: © 2006 Nature Physics

Imaging surfaces with atomic resolution is usually the domain of surface scanning probes. However, these techniques are not always well suited to real-time measurements or harsh chemical environments — in some cases the scanning tip can react with the underlying surface. Although X-ray imaging techniques can meet many of these challenges, they typically lack the spatial resolution.

Now, Paul Fenter and co-workers1 from Argonne National Laboratory in the USA show that X-ray reflectivity can be pushed to image subnanometre defects on a surface. In Fenter’s experiment, X-rays are tightly focused onto a surface and the reflected X-rays are collected by a charge-coupled device camera. On perfectly smooth surfaces, there is no change in the reflected intensity as the beam moves across the surface. However, when the beam hits a surface bump or defect, some of the reflected X-rays have a slightly different path length and the intensity changes, which allows the surface topography to be mapped.

Surface growth or chemical reactions often occur at ‘steps’ in a partially completed monolayer. This X-ray imaging technique could be used to monitor real-time step growth, both non-invasively and in reactive chemical environments.

References

  1. 1

    Fenter, P. et al. Nature Phys. (2006). 10.1038/nphys419

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Thomas, J. Baby steps. Nature Nanotech (2006). https://doi.org/10.1038/nnano.2006.96

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