Electron microscopy and electron diffraction of molecular compounds

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This project addresses the structure of various molecular assemblies investigated in the FOR 2824 by different electron microscopic techniques. The questions, which will be answered, are the exact arrangement of the molecular materials in crystalline solids as well as the degree of long-range order or the absence thereof. It is especially important to quantify the mesoscopic disorder in amorphous / crystalline mixtures as well as the nearest neighbor arrangement in amorphous solids and glasses. Only if the structure is clarified, we will be able to develop an understanding of the extremely nonlinear optical properties in experiment and in theory together with the partner projects. To answer these questions, the imaging conditions will be further adopted to the highly radiation sensitive specimen. Scanning transmission electron microscopy (STEM) with a precessing beam will be used to tackle the exact Radial Distribution Function, also for differently synthesized samples. Scanning precession electron diffraction will also yield the urgently needed information on the lateral distribution of amorphous and crystalline regions. Electron energy loss spectroscopy (EELS) will be applied to quantify chemical bonding and especially the change of bonding during irradiation, an important topic for later device applications. 4-dimensional STEM will be developed further to also be able to quantify electric fields in samples consisting of molecular materials and the results thereof will be correlated with the findings in the partner projects.