In 2018 researchers from Cornell University built an extremely high power detector that used an algorithm-driven process called ptychography to triple the resolution of the current state-of-the-art electron microscopes. The breakthrough set a record resolution in the process. A caveat with that machine was that it only functions with ultrathin samples only a few atoms thick.
A new team led by some of the same researchers from Cornell has beat their 2018 record by a factor of two using a new electron microscope pixel array detector (EMPAD) that uses a more refined 3D reconstruction algorithm. Researchers on the project say the resolution is so fine-tuned the only blurring remaining is from the thermal jiggling of the atoms in the sample itself. The team of researchers was led by David Mueller, who says that the new microscope doesn’t just set a new record; it defines a new regime which is effectively going to be an ultimate limit for resolution.
Mueller also says the development opens up a lot of new measurement possibilities for things that scientists have wanted to do for a long time. The breakthrough solved a long-standing problem by undoing multiple scattering of the beam in the sample, something scientist Hans Bethe defined in 1928 that has blocked scientists from resolving the matter in the past.
Ptychography scans using overlapping scattering patterns were material samples and looks for changes in the overlapping regions. Mueller says scientists are chasing speckle patterns that look a lot like laser pointer patterns that cats enjoy attacking. Scientists want to see how the pattern changes and can compute the shape of the object that caused that pattern.
The detector is slightly defocused, and the beam is broad to capture the widest range of data possible. The complicated algorithms the team developed reconstruct the pattern resulting in an extremely precise image with precision to a picometer.