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discovered_02_2013

discovered 02 .13 research WWW.Hzdr.DE // S.N.I.P.E.R. is the name given to a one-by-one-and-a-half-meter small facility at the HZDR's ion beam center. It is the setup that René Heller intends to use for depositing individual ions onto surfaces in a controlled manner. Whereas at the ion beam center charged particles are typically accelerated to high energies and impact on materials in order to change their properties, physicist René Heller has taken on the challenge of decelerating a handful of particles, in particular those that are highly charged, and using the benefits of their unique properties. These particles can potentially induce damage to the material surface that is spatially limited on a nanometer scale. In this way, nanostructures can be produced on the surface without inflicting radiation-induced damage to the material's bulk. In terms of their electric charge, atoms are neutral. When stripping an atom of its negatively charged electrons, you end up with a positively charged ion. The more electrons an atom is stripped of, the more energy is required for the ionizing to take place. The total amount of energy remains stored inside the ion in the form of potential energy. S.N.I.P.E.R. is capable of stripping xenon atoms of up to 44 electrons. The resulting highly charged ions thus become carriers of a huge amount of energy, which is released on a femtosecond time scale, or a millionth of a billionth of a second, during collision with a solid surface. Furthermore, the area of interaction with the surface is limited to a mere few square nanometers so that the ions give off an enormous amount of energy on a very small time and size scale. The result: tiny morphologic structures at the surface such as hillocks or holes in the nanometer range. Since the ions are comparatively slow, they do not penetrate the material very deeply and produce nanostructures only right where they are supposed to, that is, at the surfaces. Working with the TU Vienna, René Heller and his colleagues were able to answer the physically challenging question of which conditions tend to promote nanocrater or nanohillock formation. Filtering single particles Like many physicists from around the World, René Heller’s vision is to selectively "engrave" individual ions onto a surface, each of them spaced but a few nanometers apart. Given this rather ambitious goal, his facility's unique name, ONE ATOM AT A TIME: With the help of a glass capillary and a tip, similar to the kind used in atomic force microscopes, accelerated particles are being sorted out of their packet. Diagram: Sander Münster _TEXT . Christine Bohnet High-precision bullets

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