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Researchers at the University of California, Irvine have developed a new scanning transmission electron microscopy method that enables visualization of the electric charge density of materials at sub-angstrom resolution.
With this technique, the UCI scientists were able to observe electron distribution between atoms and molecules and uncover clues to the origins of ferroelectricity, the capacity of certain crystals to possess spontaneous electric polarization that can be switched by the application of an electric field. The research, which is highlighted in a study published today in Nature, also revealed the mechanism of charge transfer between two materials.
Method - Advancement - Electron - Microscopy—from - Atoms
"This method is an advancement in electron microscopy—from detecting atoms to imaging electrons—that could help us engineer new materials with desired properties and functionalities for devices used in data storage, energy conversion and quantum computing," said team leader Xiaoqing Pan, UCI's Henry Samueli Endowed Chair in Engineering and a professor of both materials science & engineering and physics & astronomy.
Employing a new aberration-corrected scanning transmission electron microscope with a fine electron probe measuring half an angstrom and a fast-direct electron detection camera, his group was able to acquire a 2-D raster image of diffraction patterns from a region of interest in the sample. As obtained, the data sets are 4-D, since they consist of 2-D diffraction patterns from each probe location in a 2-D scanning area.
Microscope - Electron - Probe - Angstrom - Camera
"With our new microscope, we can routinely form an electron probe as small as 0.6 angstrom, and our high-speed camera with angular resolution can acquire 4-D STEM images with 512 x 512 pixels at greater than 300 frames per second," Pan said. "Using this technique, we can see the electron charge distribution between atoms in two different perovskite oxides, non-polar strontium titanate and ferroelectric bismuth ferrite."
Electron charge density in bulk materials can be measured by X-ray or electron diffraction techniques by...
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