Electron microscopes are the workhorses of modern solid-state physics. Want to know what your latest transistor looks like? Throw it under a transmission or scanning electron microscope. However, transmission electron microscopes don't have great resolution. To play with the big boys, you need to move to scanning transmission electron microscopy (STEM). Unlike a transmission electron microscope, which works very much like a normal microscope with electrons replacing photons, the STEM acts like an extremely local probe of the sample's conductivity. In doing so, an image can be built up with a resolution determined by how tightly focused the stream of electrons being conducted are.
That gets determined by how well you can correct for aberrations induced by the focusing optics; improvements here depend on how much you know about the optics and the electron beam. Until now, most of the aberration correction has focused on the optics. Now, new research from Berkeley has shown that accounting for the profile of the electron beam can provide a significant enhancement in image resolution. So much so that the resolution may now be limited by unknowns in the sample itself.
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