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SUMMARY:Low-dose 2D and 4D STEM imaging of beam-sensitive materials
DTSTART:20210729T140000
DTSTAMP:20260916T085840Z
UID:30d6693b6a0f9952a05e4aeab0ff5ec36b0fcc0a70cfb0a7b2a26888
CATEGORIES:Conferences - Seminars
DESCRIPTION:Prof. Pete Nellist - University of Oxford\nScanning transmissi
 on electron microscopy (STEM) has not been widely regarded as an instrumen
 t suitable for low-dose imaging work\, yet there is mounting evidence that
  a focused probe scanning rapidly over a sample can lead to reduced damage
  compared to wide-field illumination for the same total electron fluence.
   Many materials of current interest\, including hybrid perovskites for p
 hotovoltaic applications\, Li-ion battery materials and polymers\, are hig
 hly beam sensitive.  Here we demonstrate the application of both 2D and 4
 D STEM methods for low-dose structure determination.  I will show how low
 -angle annular dark-field (LAADF) imaging reveals previously unobserved de
 fect structures in the hybrid perovskite formamidinium lead iodide (FAPbI3
 ) used in photovoltaic applications.  Electron ptychography can be used t
 o measure the small phase shifts that arise during electron transmission t
 hrough light elements.  I will described how we use the technique and sho
 w direct imaging of atomic structure of a crystalline domains in the polye
 ster\, polyethylene naphthalate (PEN)\, and polyvinyl alcohol (PVA) .  Di
 screpancies between the observed structures and those previously determine
 d using X-ray diffraction are found.
LOCATION:Zoom https://epfl.zoom.us/j/2019908135 https://epfl.zoom.us/j/201
 9908135
STATUS:CONFIRMED
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