For more than a century, scientists have relied on X-ray crystallography to elucidate the properties of crystalline materials. While their structure is highly ordered, perfect crystals seldom exist, and their defects are often studied. To this end, Miao et al.1 reported on an atomic electron tomograph (AET) that provides 0.5-Å resolution of small, solid samples such as grain boundaries in nanoparticles and dislocations in crystals, as well as point defects.
The AET uses a fine electron beam to scan the sample, yielding a 2-D image. Rotating the sample about a tilt axis gives a series of 2-D images. A computer then aligns the tilt images and performs an inversion to Fourier slices using a partial Fourier transform. An interactive 3-D reconstruction is computed, which provides the coordinates of individual atoms. These are summed to give a 3-D image.
The authors cite potential applications of AET, illustrated by figures in their article1:
- Experimental demonstration of AET without assuming crystallinity or using averaging.
- 3-D imaging of crystal defects in materials at atomic resolution.
- The three consecutive internal atomic layers further confirm that the atomic steps continuously vary along the consecutive layers.
- 3-D measurements of individual atom coordinates, atomic displacements and the strain tensor in materials.
- 3-D structure determination of ligand-protected gold nanoparticles at atomic resolution.
AET appears to be a huge advance in imaging technology for the direct observation of structure and defects on the atomic scale.
Reference
- Miao, J.; Ercius, P. et al. Atomic electron tomography: 3D structures without crystals. Science Sept 23, 2016, 353(6306); doi: 10.1126/science.aaf2157.
Robert L. Stevenson, Ph.D., is Editor Emeritus, American Laboratory/Labcompare; e-mail: [email protected].
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