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Scanning Tunneling Microscope scanning tunneling microscope (not to be confused with scanning electron microscopes), or STM, is the most powerful type of microscope ever built. It is used to obtain images of conductive surfaces at an atomic scale ~2 Angstrom (2 x 10-10 m). It can also be used to alter the observed material by manipulating individual atoms, triggering chemical reactions, and creating ions by removing individual electrons from atoms and then reverting them to atoms by replacing the electrons. Overview The STM is a non-optical microscope which employs principles of quantum mechanics. A very fine probe is moved over the surface of the material under study, and a voltage is applied between probe and the surface. Depending on the voltage and its characteristics electrons will "tunnel" (this is a quantum-mechanical effect) or jump from the probe to the surface (or vice-versa depending on the polarity), resulting in a weak electric current. The size of this current is exponentially dependent on the distance between probe and the surface. By scanning the probe over the surface and measuring the current, one can thus reconstruct the surface structure of the material under study. Adjustments of the distance between probe and surface are done using a servo loop and converse piezoelectricity. See also
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