Atomic resolution scanning/transmission electron microscopy (S/TEM) is nowadays a standard method used to reveal catalysts' nanostructures [1]. However, the active nature of catalysts renders them susceptible to alterations by high-energy electron beams. Resulting radiation effects, including heating, electrostatic charging, radiolysis, displacement damage, sputtering, and hydrocarbon contamination, might introduce structural artifacts and prevent interpreting the actual structure of these complex catalyst/support systems [2]. Electron-beam-assisted (de)activation of supported nanocatalysts (metalsupport interactions and interparticle interactions) needs to be considered. Hence, it is necessary to study and, ultimately, to minimize electron beam effects in order to characterize the pristine catalyst structure in these investigations.

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Quantitative applications of high resolution TEM are often bottlenecked by the complexity of the formed lattice images. In general terms, lattice images do not reveal the real atomic structure of the sample directly, can be distorted, and information about the sample thickness and chemical composition are heavily encoded. These drawbacks relate to the presence of lens aberrations and dynamic diffraction. The development of Cs corrected TEM [1, 2] and software that reconstructs the complex electron exit wave function [3-6] aim at removing lens aberrations and dynamic diffraction that cause variations of the electron wave's amplitude and phase with the sample thickness and limit a direct interpretation. One approach to relate the reconstructed electron exit wave to the crystal structure and chemical composition of the sample is through utilization of the channeling theory [7] that gives an intuitive analytical description between the structure and the exit wave. This approach basically models the crystal columns as focal lenses and the wave inside the crystal can be described by a 1s state. Analyzes is then carried out column by column to retrieve the crystal structure from the exit wave [8].In this paper, we present a new concept to retrieve the potential map from the exit wave based on reversed multi-slice calculations. This algorithm uses a non-linear optimization scheme to find an optimum phase grating that satisfies two boundary conditions: knowledge of the entrance surface wave and the measured exit surface wave. After the phase grating is retrieved, the position and composition in the atomic column can be quantified. Fig. 1 shows the phase of an electron exit wave of Al:Cu bi-crystal that was reconstructed from a focal series of 20 images. Figure 2 shows retrieved potential map of the Al and Cu atoms, respectively, that reveals Cu segregation to the boundary. Result and limitations of the procedure will be discussed in detail.

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In binary metal oxides (BMO), polymorphic transitions can result in various crystallographic structures which have been shown to exhibit very different and distinct physical and chemical properties. Thus, exact structural determination is essential as these changes in their crystal structures offer fine control over a wide variety of different properties and, therefore, open up a wide field of applications. However, distinguishing between different BMO polymorphs is not trivial. A combination of high-resolution X-ray diffraction (XRD), Raman and infrared-ray (IR) spectroscopy might be perform to identify phases. However, this is not a universal approach because strategies for phase identification vary with materials system, and, in the case of BMO polymorphs, might not work at all because of limitations of standard Raman/IR spectrum data of inorganics crystal. Conventional electron-microscopy-based characterization techniques, such as selected area electron diffraction (SAED), nanobeam diffraction (NBE), highresolution TEM (HRTEM), high-resolution STEM (HRSTEM), provide information that is not always sufficient for polymorph determination, especially in nanocrystalline BMO. A general and universal approach to overcome this and to confirm a specific crystal structure is performing TEM tilt experiments obtaining data from at least 4-6 zone axis orientation (e.g., using SAED patterns, NBE patterns, HRTEM or HRSTEM images). However, this is a complicate experiment and, in case of beam-sensitive materials, this time-consuming approach might not work.