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Missions Background Home FIRST LEGO League Home |  |
Individual Atom Manipulation |
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When scientists want to build something on the nanoscale they have two choices: (1) they can have the different building blocks come together on their own (also known as self-assembly), (2) they can move the different building blocks individually. The smallest building block out there is the atom. Within the last 20 years scientists have learned how to move atoms individually - an amazing feat because atoms are extraordinarily small. This process is called atom manipulation. |
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The Invention of the STM Before scientists could build at the atomic scale they needed a tool to help them observe it. Before the 1980's there was no instrument or microscope that could image the atomic scale. |
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In 1981 the Scanning Tunneling Microscope (STM) was invented by Gerd Binning and Heinrich Rohrer at IBM; the pair later received the 1986 Nobel Prize in physics for this accomplishment. The STM has ultra-high resolution and can image single atoms. This instrument allowed scientists to view a world that they could not view before: the world of the nanoscale. Many people believe that the invention of the STM was the birth of nanoscience. |
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Binning and Rohrer with their Nobel prize (1) |
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"Seeing" an Atom No one has ever seen an atom. The wavelength of visible light is more than 1000 times bigger than an atom, so light can not be used to see an atom. |
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Scanning Tunneling Microscopes work by moving a probe tip over a surface we want to image. The probe tip is an extremely sharp - just one or two atoms at its point. There is a small electric voltage on the probe tip and depending on the height of different parts of the surface, more or less current will flow from the tip to the surface. By noting the changes in current we can recreate an image of the surface at the atomic level. |
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| As the tip moves over a surface, it "feels" atoms as increases in current. | An STM image of a silicon surface - each bump is one atom. |
Atom Manipulaton STM can be used not only to image atoms but to move them as well. This was first shown by Don Eigler in 1989 when he released this image of 35 Xenon atoms arranged on a surface. Can you guess what company he worked for? |
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Xenon atoms on a nickel surface. (2) |
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Atoms can be moved on surfaces with STM by creating a what is called a tunable bond between the probe tip and the atom. When the current flowing between the atom and the probe tip increases, the atom gets stuck under the tip. The tip with the atom can then be moved to another part of the surface and the current decreased to let the atom go from the tip. |
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Increasing the current creates a bond between the tip and the atom. |
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