Structural Characterization in TEM by 3D Electron Diffraction / Micro-ED
Dr. Partha Das Application Scientist NanoMEGAS Belgium
In recent years there has been a huge interest in characterization for various materials where more than 300 structures have been solved (minerals, zeolites, MOFS, aperiodic crystals, archaeological artefacts, functional materials, organic pharmaceuticals, proteins etc.) using 3D Electron Diffraction from nanometer size crystals in TEM. The principle of acquiring TEM 3D-ED data consists of focusing the electron beam on a nanometer size crystal (50-500 nm), while sampling thereciprocal/diffraction space in small steps using beam precession or continuous crystal rotation (with or without beam PED, technique known as 3D Electron Diffraction Tomography/Micro-ED). ED intensities can be registered using CCD cameras or ultra- sensitive pixelated detectors. Acquired 3D-ED data can be used to determine ab-initio crystal unit cell, space group and atomic positions. Further dynamical refinement can also be performed using PED to detect H atoms, refine occupancies an improve reliability of the structural model down to 1-3 pm accuracy. In this webinar various examples will be shown how 3D-ED method has been applied successfully to solve structures of a big variety of nanocrystalline materials.