In situ Determination and Imaging of Physical Properties of Soft Organic Materials by Analytical Transmission Electron Microscopy

Abstract

Analytical transmission electron microscopy (ATEM) offers great flexibility in identification of the structural-chemical organization of soft materials at the level of individual macromolecules. However, the determination of mechanical characteristics such as hardness/elasticity of the amorphous and polycrystalline organic substances by ATEM has been problematic so far. Here, we show that energy filtered TEM (EFTEM) measurements enable direct identification and study of mechanical properties in complex (bio-)polymer systems of relevance for different industrial and (bio-)medical applications. We experimentally demonstrate strong correlations between hardness/elasticity of different polymers (polycaprolactone, polylactid, polyethelene, etc.) and their volume plasmon energy. Thickness and anisotropy effects, which substantially mask the material contrast in EFTEM bulk plasmon images, can be adequately removed by normalizing the latter by carbon elemental map. EFTEM data has been validated using atomic force microscopy phase images, where phase shift related to the hardness and elastic modulus of the materials.

Stability of Halide Perovskite Solar Cell Devices: In Situ Observation of Oxygen Diffusion under Biasing

“…Interestingly, the oxygen migration under the forward bias is limited to the MAPbI 3 layer only (i.e., no further migration into the spiro‐OMeTAD layer) as confirmed by EELS spectra taken at the spiro‐OMeTAD showing no change in oxygen signal in all conditions (Figure S7, Supporting Information). In addition to the change in the O(K) signal, other dramatic transitions under the forward bias (II) can be observed from the low‐loss EELS in Figure b: (i) the bulk plasmon of MAPbI 3 at 15.2 eV, which originates from a collective excitation of electrons in the bulk resonated by incident electrons, significantly reduced, and (ii) Pb(O 5 ) at 21 eV and Pb(O 4 ) at 22.5 eV merged into a single broad peak. Reduction of the bulk plasmon can be explained by amorphization of the MAPbI 3 as observed by the SAD shown earlier (Figure c‐2).…”