Jian Min Zuo1 Yu-Tsun Shao1 Renliang Yuan1

1, University of Illinois, Urbana-Champaign, Urbana, Illinois, United States

Complex crystals, formed by solid solutions or crystal growth, are characterized by locally varying composition, lattice, symmetry and chemical bonding. Examples include semiconductor heterostructures, where modulation of composition and lattice leads to quantum confinement, relaxor-ferrielectrics with locally varying polarization and doped high-Tc superconductors. Characterization of local lattice and bonding in these crystals is an outstanding challenge. Here, we report on a scanning CBED (convergent beam electron diffraction) approach to meet this challenge. Scanning CBED is performed by deflecting the electron probe and recording CBED patterns at each probe position. When it is combined with energy filtering, this technique provides all information carried by electron scattering, plus the advantage of scanning and localization using a nm-sized electron probe. In this talk, we will present methodologies for extracting local lattice, symmetry and bonding information and discuss their limitations. Applications to the determination of local lattice [1], symmetry and symmetry fluctuations in ferroelectric perovskites [2] and determination of bonding in oxides [3] will be demonstrated. Future applications of scanning CBED using fast detectors promises a full determination of crystal potential, electric and magnetic fields, however, realization of such promises require better understanding of electron diffraction through non-idealized potential and magnetic fields that requires new and improved inversion schemes. The research was supported by DOE BES.

[1] R Yuan, Y Meng, J Zhang, JM Zuo, Microscopy and Microanalysis 23 (S1), 180-181, 2017
[2] Y-T Shao, J-M Zuo, Acta Cryst. B73, 708-714, 2017
[3] JM Zuo, JCH Spence, Advanced Transmission Electron Microscopy, Springer Science+ Business Media New York, 2017