New kinds of four-dimensional scanning diffraction experiments in transmission electron microscopy enabled by high-speed direct electron detectors
by
Colin Ophus(LBNL)
→
US/Pacific
50 Auditorium
50 Auditorium
Description
Traditional scanning transmission electron microscopy (STEM) detectors are large, single pixels that integrate a subset of the transmitted electron beam signal scattered from each electron probe position. These transmitted signals are extremely rich in information, containing localized information on sample structure, composition, phonon spectra, three-dimensional defect crystallography and more. Conventional STEM imaging experiments record only 1-2 values per probe position, throwing away most of the diffracted signal information. With the introduction of extremely high speed direct electron detectors, we can now record a full image of the diffracted electron probe at each position, producing a four-dimensional dataset we refer to as a 4D-STEM experiment. In this talk, I describe the challenges and opportunities created by 4D-STEM.
The 4D-STEM experiments that will be covered: (1) mapping out local structure and composition by matching the experimental patterns to diffraction simulations. (2) Local strain measurements over a very large field of view using nanobeam electron diffraction. (3) Virtual dark field imaging using arbitrary detectors. (4) A new form of efficient, linear phase contrast imaging, called matched illumination and detector interferometry (MIDI)-STEM. (5) Ptychography and ptychographic extension of MIDI-STEM to improve signal transfer.
