In the May 21 2021 issue of the journal Science researchers report they have developed an electron microscope that has 3 to 10 times greater resolution than any microscope that has existed before and is able to produce ultraprecise images of picometer (1-trillionth of a meter) precision. And it can do this in 3-D with much thicker samples than has been possible before. David Muller the lead Author of the paper says he thinks an instrument like this could be used to map the synapse connections in the human brain, he refers to it as "connectomics on demand". Muller says:
"It’s reached a regime which is effectively going to be an ultimate limit for resolution. We basically can now figure out where the atoms are in a very easy way. This opens up a whole lot of new measurement possibilities of things we’ve wanted to do for a very long time.[...] Until now, we’ve all been wearing really bad glasses. And now we actually have a really good pair. Why wouldn’t you want to take off the old glasses, put on the new ones, and use them all the time?"
From May 21, 2021 issue of the journal Science:
Locating atoms with higher precision
Two major problems that limit the resolution and interpretation of electron microscopy images are lens aberrations and multiple scattering. Chen et al. overcame these issues with ptychography, a technique that uses coherent scattering and multiple overlapping illumination spots to reconstruct an image from far-field diffraction patterns. This method works at a resolution that is limited, not by optics, but rather by the scattering strength of the sample, so it can work better with thicker samples. The authors achieved ultimate lateral resolution better than the thermal vibration of atoms in a PrScO3 sample and showed that it is theoretically possible to identify single dopant atoms.
Science, this issue p. 826
Transmission electron microscopes use electrons with wavelengths of a few picometers, potentially capable of imaging individual atoms in solids at a resolution ultimately set by the intrinsic size of an atom. However, owing to lens aberrations and multiple scattering of electrons in the sample, the image resolution is reduced by a factor of 3 to 10. By inversely solving the multiple scattering problem and overcoming the electron-probe aberrations using electron ptychography, we demonstrate an instrumental blurring of less than 20 picometers and a linear phase response in thick samples. The measured widths of atomic columns are limited by thermal fluctuations of the atoms. Our method is also capable of locating embedded atomic dopant atoms in all three dimensions with subnanometer precision from only a single projection measurement.
John K Clark
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