Magazine article Science News

Electron Holography on a Crystal Canvas

Magazine article Science News

Electron Holography on a Crystal Canvas

Article excerpt

Electron holography on a crystal canvas

Surface scientist expend a great deal of effort pinpointing the locations of atoms on or near a material's surface--a task they would find easier and more revealing if they could obtain three-dimensional images with enough resolution to depict the atoms' precise locations. That capability now seems within reach.

For the first time, a team of researchers has reconstructed a surface's three-dimensional crystal structure from the pattern generted by electrons emitted from surface atoms. The results prove that a diffraction pattern produced by such electrons can be interpreted as a hologram -- the electron-generated equivalent of the visible-light holograms so often used today as security features on credit cards.

"Experimentalists have been seeing these [diffraction] patterns for years. They had jsut never thought of interpreting them as holograms," says physicist Dilano K. Saldin of the university of Wisconsin-Milwaukee. He and his colleagues describe their reconstruction technique inthe Aug. 20 PHYSICAL REVIEW LETTERS.

When an atom near the surface emits an electron, that electron may come directly to the surface or it may bounce off a neighboring atom before emerging. Because electrons also behave like waves, electrons traveling along paths of different lengths would overlap at the detector, producing a distinctive interference pattern. The intensity of that diffraction pattern would vary from place to place, depending on the angle at which the electrons leave the surface. …

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