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Electron refraction at high resolution and precision

Electron beam defection as measured by micro-diffraction (b) and DPC signal (c) after passing through a parallel plate micro-capacitor (a) at different applied voltages.

Research article “Correlative micro-diffraction and differential phase contrast study of mean inner potential and subtle beam-specimen interaction“, by Mingjian Wu and Erdmann Spiecker, has been accepted for publication in the journal Ultramicroscopy.

Probing nanometer scale electrostatic (Coulomb) potential and/or the corresponding electric field, and establishing structure- properties relationships at this length scale in advanced functional materials are not only of fundamental interest but also of technological relevance and importance. With this study the authors tend to establish methods to study the electrostatic potential and electric field at nano-scale inside (e.g., charged surface and interfaces) and outside (e.g., stray field) materials, with the scope to be compatible with in-situ studies. Mean inner potential (MIP) of a crystalline is a well defined quantity and has been extensively studied both experimentally and theoretically for many materials. Therefore, the measurement of MIP of a well-known material can be regarded not only as an additional independent measure of MIP of this particular material, but also as an approach to validate/calibrate the methods themselves for their further application in extracting electrostatic potential and electric field in samples quantitatively. In this study, MIP of Si and GaAs are determined to be consistent with literature values. Furthermore, the authors observed subtle beam-specimen interaction in the form of Fresnel finges displacements, and achieved a quantitatively good agreement with simulation, based on that, they proposed a quasi-contactless mode of probing electrostatic potential.

The paper is included in the special issue “PICO 2017”, and will be presented at “The 4th conference on Frontiers of Aberration Corrected Electron Microscopy – PICO 2017”, which will be held from 30 April to 4 May 2017 in Kasteel Vaalsbroek.

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