FIB/Electron Microscope Project Pursues Single-Atom Imaging
Alexander E. Braun, Senior Editor -- Semiconductor International, 12/26/2007
FEI Co. (Hillsboro, Ore.) and Netherlands-based Foundation for Fundamental Research on Matter (FOM), which links academic and industrial physical research resources to attain specific commercial goals, have launched a joint research project aimed at advancing electron microscopes and focused ion beam (FIB) systems to enable the structure of materials to be made visible and processed at the single-atom scale.
The admittedly ambitious research program has a double purpose: first, to advance and harness the existing potential in electron microscopes and ion beam systems for a full range of applications in physics and biology; second, to research the interaction between electron beams, ion beams, laser light and matter.
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| Atomic-resolution images of single-wall carbon nanotubes with CuI filling at 80 KeV acceleration voltage. (Source: B. Freitag, FEI Co.; sample courtesy of Prof. Kiselev) |
According to Frank de Jong, FEI’s director of research and technology, the program will initially work to find ways of using existing equipment to the best advantage by determining how to use it to its full potential. “This includes improving sample and test methodologies, as well as upgrading some of the software and procedures used,” he said. “In this part of the program, for instance, we’re looking to improve 3-D reconstruction methods — the way in which 3-D data is extracted from samples and processed. Here, we’re concerned not with improving the instrument itself, but the methodology of how it is used to get better results.”
The second part of the program targets a few important parts of these instruments, where researchers expect to produce improvements by working in cooperation with academia. “Here, we’re looking at ion and electron sources,” de Jong said. “In the case of electron microscopes, one of the universities has some interesting ideas on how to improve the electron source by manipulating it with a laser beam, by having it interact with and improve the source’s characteristics. We’re also looking at new ion source possibilities.”
Before single-atom imaging can come to pass, formidable hurdles must be eliminated. As de Jong put it, “We’re on the brink of imaging individual atoms in solid materials, such as metals. We already have images of small metal particles used as catalysts. If you look at the rim of those particles, it is almost possible to view single atoms in 2-D. We want to do this in 3-D.” To accomplish this feat, it would be necessary to produce sample images from two different tilt angles and then reconstruct them in a manner similar to that used by X-ray tomography, which tilts the source and detector around the patient. “We’re not yet at the stage where we are able to use electron tomography to obtain a 3-D image of an atom,” de Jon conceded. The group, however, is confident that it will be possible to do this with solid materials, because these are essentially immune to the effects of an electron beam. The real challenge lies in doing it with more delicate biological materials — viruses, proteins or cell structures.
Because the first part of the program does not require rebuilding or prototyping, de Jong expects results in 1-1.5 years. In the case of new sources and other developments, which would be needed for the dynamics required for atom imaging, this may take longer because it will require experimenting with things never done before. “Between 65 to 80% of the effort will be in applied research. This is far from being just a matter of straightforward engineering,” de Jong said.
The effort’s magnitude cannot be underestimated, particularly because as results are obtained, still further capabilities will be pursued. “We’ll go beyond just resolving power,” de Jong said. “If you can see an individual atom in 3-D, you should also be able to determine what kind it is — carbon, iron, phosphorous. There are spectroscopic techniques that can be used, but combining them with the means with which to see single atoms will take considerable more research and work. Eventually, we’d like to do these observations in a dynamic environment and actually see the atom move from one position to another, as when it is deformed in an interface, for example. I don’t know whether this is physically feasible. If it is, we’ll be able to learn considerably more from any material that we choose to observe.”
The FOM-FEI research program has a five-year term, a total budget of €2.7M ($3.88M), and will run at Delft University of Technology, Technische Universiteit Eindhoven, FOM and FEI laboratories in the Netherlands and United States.
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