Aberration-corrected scanning transmission electron microscopy for atomic-resolution studies of functional oxides

Abstract

Electron microscopy has undergone a major revolution in the past few years because of the practical implementation of correctors for the parasitic lens aberrations that otherwise limit resolution. This has been particularly significant for scanning transmission electron microscopy (STEM) and now allows electron beams to be produced with a spot size of well below 1 Å , sufficient to resolve inter-atomic spacings in most crystal structures. This means that the advantages of STEM, relatively straightforward interpretation of images and highly localised analysis through electron energy-loss spectroscopy, can now be applied with atomic resolution to all kinds of materials and nanostructures. As this review shows, this is revolutionising our understanding of functional oxide ceramics, thin films, heterostructures and nanoparticles. This includes quantitative analysis of structures with picometre precision, mapping of electric polarisation at the unit cell scale, and mapping of chemistry and bonding on an atom-by-atom basis. This is also now providing the kind of high quality data that are very complementary to density functional theory (DFT) modelling, and combined DFT/microscopy studies are now providing deep insights into the structure and electronic structure of oxide nanostructures. Finally, some suggestions are made as to the prospects for further advances in our atomistic understanding of such materials as a consequence of recent technical advances in spectroscopy and imaging.

Atomic structure study of the pyrochloreYb2Ti2O7and its relationship with low-temperature magnetic order

“…when the inner angle of the ADF detector is only a little larger than the probe convergence angle α, coherent diffraction effects can produce strain contrast that is very sensitive to crystal orientation that compromises the ability to relate intensities to atomic number [38]. Here, therefore, for images intended to be sensitive to composition, we use an ADF detector inner angle at least 4.6 times the probe convergence angle α, giving a scattered intensity proportional to a small power of the atomic number, Z 1.5 to Z 2 [52,53].…”

“…1(b) contain quantifiable composition information [38,39] due to the atomic number sensitivity of high-angle (Rutherford) electron scattering [40][41][42][43]. Thus, it may be expected that analysis of image intensities may provide data that is sensitive to the composition of the Yb and Ti sublattices.…”

Oxygen vacancy ordering induced displacements of cations in yttria-stabilized zirconia

“…[7][8][9] The clear view of atom positions enables direct comparison of experiment with theory modeling. 7,8,[10][11][12] In this work, we employ the contrast based on the high-angle scattering of electrons (Z-contrast) in a STEM mode to image the cation sub-lattice only, which allows for directly measuring vacancy-induced displacements of cations in YSZ. In conjunction with density-functional theory (DFT) calculations, we show that the location and concentration of oxygen vacancies in YSZ can be determined from the measured atomic displacements of the cation sub-lattice.…”

Evolution of interfacial structure of Co-based periodic multilayers upon annealing

“…Unlike bright field (BF) imaging, HAADF imaging reduces the diffraction and phase contrast and the collected signal is dependent on the atomic number Z [11,12], the shape of the atom and the total number of atoms encountered by the electron probe. Therefore, HAADF STEM image intensity is highly sensitivity to the atomic number (Z n with 1.5 < !…”