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Atom Probe Microscope will Revolutionize Materials Study

In high-tech materials, the action is down at the atomic level. The problem is not always making materials at that scale, but knowing what you've made. Enter the three-dimensional atom probe (3DAP) microscope being developed by Materials Science and Engineering Professor Thomas F. Kelly. This 3DAP is able to make atomic-scale maps of the position and identity of millions of atoms. There are just a handful of these microscopes in the world at this point.

Professor Kelly has specialized in making a very high-speed 3DAP which will ultimately record one million atoms per second. Just how much faster is that than current methods? To study material containing one billion atoms, over a distance of about one micrometer, a fast 3DAP would only take about 17 minutes. With current methods, the same analysis would take more than a year. That's a quantum leap for the study of many critical materials, says Kelly.

Kelly and others with Atom Microscope

Materials Science and Engineering Associate Professor Thomas F. Kelly (left) and graduate students Mei Zhou (center) and Dave Larson with the college's new Atom Probe Microscope. (61K JPG)

The 3DAP will play a role in greatly improving the development and manufacture of a number of high-tech materials. For example, it will help design and create stronger structural metals like steels and aluminum alloys. Electronic devices will benefit from better silicon-based semi-conductors and compound semi-conductor structures as seen by 3DAP. "Companies and researchers developing new materials need much more precise information about how improvements are made and performance is enhanced," he says. One could liken current methods to a nearly hit-and-miss proposition--"You can make changes in the process which improve the material, but you don't have any way of knowing why it improved." This makes further improvements more difficult to predict and make. "But if you can see the interface more sharply, at the atomic level, you can see what's better. You may find that what you've done is the best so far achieved--but not necessarily the best there could be."

Other types of scientific studies will find 3DAP a revolutionary tool as well. For example, scientists (including Materials Science and Engineering Assistant Professor Susan E. Babcock) are actively studying the segregation of impurities to grain boundaries, which are the internal interfaces of materials. Segregation of this type often limits the properties in many classes of materials, and understanding them more thoroughly could have wide-ranging implications. For example, many highly publicized failures in high-strength metals and ceramics components in bridges or aircraft are caused by this segregation, says Kelly. Another basic science application for 3DAP is studying very small-scale nucleation and growth phenomena--"it has not been possible to study these kinds of processes down towards the atomic scale which is where everything is happening," says Kelly.

The basic, patented 3DAP is operational and has already produced three-dimensional images. The development team, which includes Kelly and both graduate and undergraduate students, has patented and almost completed installation of a new stage called the Local Electrode Atom Probe (LEAP) which will make it much easier to analyze planar structures like semi-conductors. LEAP will for the first time make it possible to analyze thin films on substrates with implications for electronic structures and magnetic recording structures. LEAP will also make it much easier to achieve the high pulsing rates 3DAP needs to see that revolutionary million atoms per second.

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