In a transmission electron microscope (TEM), electron diffraction patterns and images of specimens are recorded as an intensity distribution. This loss of the phase of the exit wave limits the information that is available about the specimen.
In this work, we develop a simple method to retrieve the full exit wave from a single electron diffraction pattern. Unlike conventional diffractive-imaging techniques, a straight edge is placed close to the object. This straight edge not only provides a scattered reference wave to interfere with the object wave, but also greatly simplifies the reconstruction process due to the mathematical convenience afforded by its shape, as has been demonstrated for X-rays [1].
In practice, the straight edge could be implemented by a square aperture. Here we test a simple experimental set-up. A square hole is milled by focused ion beam on a thick metal foil. Some features are left at the corner as the test object to be reconstructed. The test object is successfully reconstructed using a single diffraction pattern with six independent reconstructions.
This method opens the possibility of determining exit wave phases from just a single diffraction pattern, with potential applications in beam-sensitive materials and biological samples. Furthermore, the fast reconstruction process makes it a promising in-situ imaging technique for magnetic materials.
Acknowledgement:
The authors acknowledge the assistance from Dr. Amelia Liu and Dr. Gediminas Gervinskas with FIB at the Monash Centre for Electron Microscopy. This research used equipment funded by Australian Research Council grants LE0454166 and LE0882821 at the Monash Centre for Electron Microscopy (a node of Microscopy Australia).