Resumen

ESPARZA, Rodrigo. Atomic resolution imaging of light elements using low voltage Cs-corrected HAADF and ABF-STEM. Mundo nano [online]. 2020, vol.13, n.25, pp.45-60.  Epub 25-Nov-2020. ISSN 2448-5691.  https://doi.org/10.22201/ceiich.24485691e.2020.25.69636.

Scanning transmission electron microscopy (STEM) can give structural and chemical information down to 0.1 nm of spatial resolution, which sub-angstrom resolution is achieved with a spherical aberration corrector for the probe. In the STEM, the electron probe is focused and scanned over the sample and the image is formed by measuring the transmitted electron intensity arising after the electron-specimen interactions. The scattered electron intensity that cross the sample can be employed to obtain bright and dark field images. The STEM is a powerful instrument to understand the physical properties of nanostructures which requires the local structure and local chemistry to be determined at the atomic scale. Therefore, STEM is a technique able to identify the atomic columns and the position of atoms using simulation techniques. In this work, the basic instrumental parameters using high angle annular dark field (HAADF-STEM) and annular bright field (ABF-STEM) modes were evaluated using a standard sample of Si[110]. Also, experimental HAADF-STEM and annular bright field (ABF-STEM) images of LaAlO3 sample were obtained at 80 kV and compared with simulated images obtained by using the multi slice dynamical diffraction method. Using the ABF-STEM technique, it was possible to clearly visualize the atomic columns of the La, O and Al elements included in the sample. Images simulated were found to agree well with experimental images.

Palabras llave : scanning transmission electron microscopy; annular bright field; high angle annular dark field; image simulations.

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