Abstract
Ptychographic imaging in transmission electron microscopy is based on the detection of a huge number of diffraction patterns generated as an electron-beam probe scans the sample. Unlike conventional diffraction experiments where information about the phase of the scattered beam is lost, by scanning the entire sample and recording the diffraction patterns, an inversion analysis can reconstruct the complex amplitude of the beam and ultimately the atomic positions. Probe beams continue to decrease in size and can be much smaller than the distance between scatterers. The diffraction spots also broaden and interfere with one another (see the figure). Analysis of this interference allows more information to be extracted, such as minute details of nuclei position and electronic structure that define physical properties and enable visualization of subtle details of electric fields, orbital orderings, ferroic behavior, and perhaps local spins. Ptychography and related techniques are poised to revolutionize the field of electron microscopy, in much the same way as they have in x-ray crystallography (1), and as aberration correction has achieved for imaging, provided that some key challenges can be met.
