Reducing Electron Beam Damage with Multipass Transmission Electron Microscopy

With the introduction of hardware aberration correction, direct electron detectors, ultra-bright electron sources and highly precise spectrometers, it seems like we are approaching the pinnacle of transmission electron microscopy (TEM) imaging and spectroscopy. However, the field of electron microscopy is still far from the ultimate signal-to-noise and efficiency limits imposed by electron scattering physics. Current TEM experiments where images are measured with high quantum efficiency detectors can approach the shot noise (or Poisson noise) limits, but the true upper bound for signal-to-noise for any electron imaging measurement is the Heisenburg limit [1]. Some initially proposed methods for approaching this measurement limit were quantum techniques such as highly-entangled measurement particles, which are impractical to use in a large-scale imaging experiments using photons. Entangling large numbers of electrons is even more difficult and seems unlikely to be achieved with existing technology. However, there is an alternative method to approach the Heisenburg limit: allowing the electron probe to interact with the sample many times before the image intensity measurement [2], as in the recently proposed design for a multipass transmission electron microscope [3,4].