<p>Fast pixelated detectors in scanning transmission electron microscopy (STEM) enable acquisition of a two-dimensional diffraction pattern at every probe position, known as four-dimensional STEM (4D-STEM). In 4D-STEM, each measured intensity has dual character, forming a pixel in diffraction space, and equally a pixel in real space. Applying binary masks in diffraction space is often used to produce ‘virtual’ bright-field or annular-dark field images. Here we present a complementary method for atomic-resolution 4D-STEM, using correlation between real-space images (templates) and the data to create weighted masks in diffraction space. These weighted masks provide significant improvement over binary masks, and can produce images specific to different types of atom columns. We demonstrate this approach by obtaining separate high contrast images of Li and O columns in LiFePO<sub>4</sub> and O columns in PbTiO<sub>3</sub>. This method provides a computationally straightforward route to probe 4D-STEM data, and is particularly effective for specimens of moderate thickness where multiple scattering produces strong correlations in diffraction patterns.</p>

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Template-Derived Masks for 4D-STEM

  • Yining Xie,
  • Eoin Moynihan,
  • Marin Alexe,
  • Louis F. J. Piper,
  • Ana M. Sanchez,
  • Richard Beanland

摘要

Fast pixelated detectors in scanning transmission electron microscopy (STEM) enable acquisition of a two-dimensional diffraction pattern at every probe position, known as four-dimensional STEM (4D-STEM). In 4D-STEM, each measured intensity has dual character, forming a pixel in diffraction space, and equally a pixel in real space. Applying binary masks in diffraction space is often used to produce ‘virtual’ bright-field or annular-dark field images. Here we present a complementary method for atomic-resolution 4D-STEM, using correlation between real-space images (templates) and the data to create weighted masks in diffraction space. These weighted masks provide significant improvement over binary masks, and can produce images specific to different types of atom columns. We demonstrate this approach by obtaining separate high contrast images of Li and O columns in LiFePO4 and O columns in PbTiO3. This method provides a computationally straightforward route to probe 4D-STEM data, and is particularly effective for specimens of moderate thickness where multiple scattering produces strong correlations in diffraction patterns.