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Electron holography delivers atomic resolution, providing new insights into material structures

​Researchers at Leti, a CEA Tech institute, recently developed an electron holography technique capable of imaging material structures with a spatial resolution of just one atom.

Published on 5 March 2018

Electron holography, a transmission electron microscopy (TEM) technique, can be used to image a material's crystal lattice, delivering valuable insights into the material's electrostatic potential. Crystal lattices, which are determined by the chemical structure of the atoms that make them up, provide information about a material's properties. Previously, images obtained using electron holography contained too much noise to determine the role of a single atom in a material's structure. However, researchers at Leti recently developed a method that fills this gap.

To reduce the amount of noise in images, the researchers combined several images to obtain a single one offering greater precision. Combining holograms is much more complex than combining conventional images—it requires sophisticated image processing capabilities. The researchers had to modify the equipment to enable the capture of a suitable series of holograms and develop image processing software to combine the holograms captured.

The method was tested on single-layer MoS2, where it was used to generate images that let the researchers see the electrostatic potential of a single sulfur atom vacancy with a resolution of less than 1 angstrom. Because it provides insights into the chemical nature of an atom, the method could bring real benefits to the microelectronics industry, where it could be used to map semiconductor dopants very locally or to observe defects in a nanostructure due to extra or missing atoms at specific locations. Finally, the method will improve the reliability of magnetic or electrical field images as well as strain maps measured by electron holography, while providing high sensitivity.

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