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90° Partial Dislocation Structure
 On the left: Model calculation showing a proposed structure for an important defect in the silicon crystal, viewed using a 2 Angstrom (0.2 nanometers) resolution. Atom columns are indicated by the dots. Near neighbor connectivity of the atoms is indicated by the lines. Bright areas indicate strong scattering of the 2 Angstrom electron beam.
On the right: The same structure viewed with a 1 Angstrom diameter beam. Details in the four column group (red) will become apparent. [ More picture options ] [ Get permission to re-use ]
Atom Interaction
 Au Test Objects
In the middle: 5 nanometer-sized crystals of gold are supported by a thin carbon film -- a little like beach balls on a trampoline. The atomic structure of the gold crystal can be viewed using the sub-Angstrom sized beam of electrons. A consequence of using such a small beam, is that the atoms become more visible. In small regions near the gold crystals, gold atoms are arranged in regular arrays. The patterns arranged around the image are indicate the regularity and orientation of these arrays. So, for instance, in the upper right, the pattern of six spots, arranged around the one central spot, tells us that the atoms near the gold crystal on the upper right, are arranged in a six-fold, or hexagonal, packing structure. [ More picture options ] [ Get permission to re-use ]  Ge30Si70 / Si Quantum Well
In the process of creating "strained silicon" to improve the speed of a transistor, we must make atomically abrupt interfaces between silicon and an alloy of germanium and silicon. Using the very small electron beam, we can scan across the interface structure, in a raster fashion, similar to what is done in a tv screen, to produce the image seen here. On the left, the Ge30Si70 alloy is brighter because the Ge influences the electron beam more strongly than silicon. Therefore, we can image the atomic composition at the interface. The pattern in the lower left indicates the degree of ordering, as it did above for the gold crystals. [ More picture options ] [ Get permission to re-use ]  Au Two-Atom Interaction
Single atoms of gold are easily observed on the surface of the carbon film. These move around, partly in response to interactions with other atoms, partly by thermal fluctuations, and partly by interaction with the electron beam. When two of them approach, they feel an attractive force. As they approach closer, this attractive force turns into a repulsive force. This can be seen in real time: sumamrized by the frames labeled by time. In this case, two atoms approach, circling one another (indicated by the arrows). Then one of the atoms moves rapidly away to a spot about 0.5 nanometers distance away. Finally the other atom follows. These frames are taken from the AVI Animation 1. Real time movie that shows the two atom interaction
(AVI Animation 1, .3 MB)
This sequence shows the dissolution of a gold crystal under influence of the electron beam. The crystal changes its shape, and atoms evaporate away from it. At one point the whole atom cluster explodes into individual atoms, and the reforms into a smaller cluster. It does this at least one more time becore is has completely disassembled into single atoms which disperse.
(AVI Animation 2, 7.2 MB) [ More picture options ] [ Get permission to re-use ]  Comparison with previous performance for Ge30Si70
This panel compares the performance of the electron microscope with and without the aberration correction. In the top panels, we show a "shadow map" pattern that tells us about the quality of the optical system. The featureless "patch" in the middle is an area that transmits electrons faithfully to make the very small electron beam. The bigger the patch, the better. In the middle, we show the image results. On the left, we cannot resolve the pairs atom columns in Si that are separated by 0.135 nanometers. On the right, these pairs are easily resolved. The patterns at the bottom, again, indicate the faithfulness with which we image the structure. The greater number of spots on the right indicate that smaller spatial distances are being reproduced on the right. [ More picture options ] [ Get permission to re-use ]
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