STM Positioning of Individual Atoms (:51)
The Scanning Tunneling Microscope is not a traditional microscope. Rather than showing a direct image, it uses a very sharp tip—having only a single or a few atoms at its apex—to scan the surface of a material. By bringing the tip very close to the sample surface and applying a bias voltage, a flow of current can be measured between the tip and the sample due to the quantum mechanical effect of electron tunneling. Keeping this tunneling current constant and recording the vertical movement of the tip across the surface makes it possible to study the structure of the surface, atom by atom.
As in this video, the STM can even be used to manipulate individual atoms and molecules. In 1989, IBM scientist Don Eigler in a famous experiment used his newly developed low-temperature STM to position 35 xenon atoms to spell "IBM".
Courtesy of IBM Research - Zurich