3D Positions of Atoms Observed for First Time

[Guest_Jim_*]

Atoms are very small things, so it is hard to know where exactly they are in an object. In the past we have been able to estimate their locations using X-ray crystallography, which measures how X-rays interact with a crystal, but this has its limits. Now researchers at the University of California, Los Angeles have successfully mapped atoms in three-dimensions for the first time.

To perform this study the researchers used a scanning transmission electron microscope at Berkeley Lab. This microscope is able to image the location of atoms, but can only scan in two dimensions. To overcome this limitation, the target sample will have to be rotated through multiple angles in order to build a complete, 3D picture. This can be problematic though as the electron beam can damage a sample. The researchers addressed this by keeping the energy of the beam below the radiation damage threshold of the tungsten sample they were aiming it. It took tilting the sample 62 times, but eventually they were able to build a 3D model of the 3769 atom comprising the sample's tip.

The sample consisted of nine layers and on the sixth one the researchers found a point defect where either an atom was missing or another atom of a different element was located. Point defects like this can affect a material's properties, so being able to catch one is important. Indeed this research and future studies of other materials could significantly improve our understanding of each material's properties.

Source: University of California, Los Angeles

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