A super-resolution x-ray microscope

Swiss researchers have developed a very-high-resolution x-ray microscope. Their approach combines two well-known microscopy techniques, coherent diffractive imaging (CDI) and scanning transmission x-ray microscopy (STXM). As a result, the new system offers both the high penetration power of x-rays and high spatial resolution. This method will allow other scientists to look inside semiconductors or biological samples without altering them. It could be used to identify nanometer defects in buried semiconductor devices or to improve the performance of future semiconductor devices. The research team doesn't give details on availability of this microscope. But read more...

Swiss researchers have developed a very-high-resolution x-ray microscope. Their approach combines two well-known microscopy techniques, coherent diffractive imaging (CDI) and scanning transmission x-ray microscopy (STXM). As a result, the new system offers both the high penetration power of x-rays and high spatial resolution. This method will allow other scientists to look inside semiconductors or biological samples without altering them. It could be used to identify nanometer defects in buried semiconductor devices or to improve the performance of future semiconductor devices. The research team doesn't give details on availability of this microscope. But read more...

Super-resolution X-ray microscopy method

You can see above the results of this new microscopy method. On the left is "a conventional Scanning Electron Micrograph (SEM) image of the sample." And on the right panel, "the novel super-resolution X-ray microscopy method visualizes details and line defects in the buried nanostructure." (Credit: P. Thibault and F. Pfeiffer, PSI/EPFL) You'll find here additional images in high-resolution format. The two pictures above were picked from this specific set (PDF format, 3 pages, 591 KB).

This research work has been done by researchers from the Paul Scherrer Institut and the Ecole Polytechnique Fédérale de Lausanne (EPFL), both located in Switzerland. The team was led by Franz Pfeiffer, Assistant Professor at EPFL, and by PSI researcher Pierre Thibault.

Here is quote from Pfeiffer about how the team implemented its new method. "Researchers have been working on such super-resolution microscopy concepts for electrons and x-rays for many years. Only the construction of a dedicated multi-million Swiss-franc instrument at PSI's Swiss Light Source allowed us to achieve the stability that is necessary to implement our novel method in practice."

And what are the characteristics of this new system? "The new instrument uses a Megapixel Pilatus detector (whose big brother will be detecting collisions from CERN's Large Hadron Collider), which has excited the synchrotron community for its ability to count millions of single x-ray photons over a large area. This key feature makes it possible to record detailed diffraction patterns while the sample is raster-scanned through the focal spot of the beam. In contrast, conventional x-ray (or electron) scanning microscopes measure only the total transmitted intensity."

The software was conceived by Thibault. "These diffraction data are then treated with an algorithm conceived by the Swiss team. 'We developed an image reconstruction algorithm that deals with the several tens of thousands of diffraction images and combines them into one super-resolution x-ray micrograph,' explains PSI researcher Pierre Thibault. 'In order to achieve images of the highest precision, the algorithm not only reconstructs the sample but also the exact shape of the light probe resulting from the x-ray beam.'"

This research work appears in the latest issue of Science Magazine under the title "High-Resolution Scanning X-ray Diffraction Microscopy" (Volume 321, Issue 5887, Pages 379-382, July 18, 2008).

Here is a link to the abstract. "Coherent diffractive imaging (CDI) and scanning transmission x-ray microscopy (STXM) are two popular microscopy techniques that have evolved quite independently. CDI promises to reach resolutions below 10 nanometers, but the reconstruction procedures put stringent requirements on data quality and sample preparation. In contrast, STXM features straightforward data analysis, but its resolution is limited by the spot size on the specimen. We demonstrate a ptychographic imaging method that bridges the gap between CDI and STXM by measuring complete diffraction patterns at each point of a STXM scan. The high penetration power of x-rays in combination with the high spatial resolution will allow investigation of a wide range of complex mesoscopic life and material science specimens, such as embedded semiconductor devices or cellular networks."

For more information, you should read a previous EPFL news release, "New technology sharpens X-ray vision" (January 20, 2008). In this document, the researchers stated that they've developed a new method for producing dark-field X-ray images more precise than the ones produced by current methods.

X-ray images of a chicken wing

You can see above the results of this dark-field microscopy method. On the left is a traditional X-ray image of a chicken wing, while a much more detailed dark-field image appears on the right. (Credit: PSI/EPFL) Here are two links of larger versions of these left and right photos.

Here is the introduction of this EPFL news release. "Researchers at the Paul Scherrer Institute (PSI) and the EPFL in Switzerland have developed a novel method for producing dark-field X-ray images at wavelengths used in typical medical and industrial imaging equipment. Dark-field images provide more detail than ordinary X-ray radiographs and could be used to diagnose the onset of osteoporosis, breast cancer or Alzheimer's disease, to identify explosives in hand luggage, or to pinpoint hairline cracks or corrosion in functional structures. Up until this point, dark-field X-ray imaging required sophisticated optics and could only be produced at facilities like the PSI's 300m-diameter synchrotron."

Sources: Ecole Polytechnique Fédérale de Lausanne, Switzerland, July 18, 2008; and various websites

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