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Electrostatic charging of specimens during electron, photon or ion irradiation is a complicated and poorly understood phenomenon, which can affect the acquisition and interpretation of experimental data and alter the functional properties of the constituent materials. It is usually linked to secondary electron emission, but also depends on the geometry and electrical properties of the specimen. Here, we use off-axis electron holography in the transmission electron microscope to study electron-beam-induced charging of an insulating Al2O3 nanotip on a conducting support. The measurements are performed under parallel electron illumination conditions as a function of specimen temperature, electron dose, primary electron energy and surface cleanliness. We observe a lack of reproducibility of charge density measurements after cycling the specimen temperature. Surprisingly, we find both positively and negatively charged regions in closely adjacent parts of the specimen.

Chemical communications : ChemComm 10(19), 3130-3133 (2022). doi:10.1039/D1CC07172F, Published by Royal Society of Chemistry, Cambridge

Ultramicroscopy 241, 113593 (2022). doi:10.1016/j.ultramic.2022.113593, Published by Elsevier Science, Amsterdam

ACS applied energy materials 3(6), 5101-5106 (2020). doi:10.1021/acsaem.0c00543, Published by ACS Publications, Washington, DC

We use an electron holographic method to determine the charge distribution along a quasi-one-dimensional W5O14 nanowire during in situ field emission in a transmission electron microscope. The results show that the continuous charge distribution along the nanowire is not linear, but that there is an additional accumulation of charge at its apex. An analytical expression for this additional contribution to the charge distribution is proposed and its effect on the field enhancement factor and emission current is discussed.

With operando transmission electron microscopy visualizing the solid-solid electrode-electrolyte interface of silicon active particles and lithium oxide solid electrolyte as a model system, we show that (de)lithiation (battery cycling) does not require all particles to be in direct contact with electrolytes across length scales of a few hundred nanometers. A facile lithium redistribution that occurs between interconnected active particles indicates that lithium does not necessarily become isolated in individual particles due to loss of a direct contact. Our results have implications for the design of all-solid-state battery electrodes with improved capacity retention and cyclability. ©

We demonstrate the ability to record a tomographic tilt series containing 3487 images in only 3.5 s by using a direct electron detector in a transmission electron microscope. The electron dose is lower by at least one order of magnitude when compared with that used to record a conventional tilt series of fewer than 100 images in 15-60 minutes and the overall signal-to-noise ratio is greater than 4. Our results, which are illustrated for an inorganic nanotube, are important for ultra-low-dose electron tomography of electron-beam-sensitive specimens and real-time dynamic electron tomography of nanoscale objects with sub-ms temporal resolution.

The electron transport and elastic properties of InAs nanowires grown by chemical vapor deposition on InAs (001) substrate were studied experimentally, in-situ in a transmission electron microscope (TEM). A TEM holder allowing the measurement of a nanoforce while simultaneous imaging nanowire bending was used. Diffraction images from local areas of the wire were recorded to correlate elastic properties with the atomic structure of the nanowires. Another TEM holder allowing the application of electrical bias between the nanowire and an apex of a metallic needle while simultaneous imaging the nanowire in TEM or performing electron holography was used to detect mechanical vibrations in mechanical study or holographical observation of the nanowire inner potential in the electron transport studies. The combination of the scanning probe methods with TEM allows to correlate the measured electric and elastic properties of the nanowires with direct identification of their atomic structure. It was found that the nanowires have different atomic structures and different stacking fault defect densities that impacts critically on the elastic properties and electric transport. The unique methods, that were applied in this work, allowed to obtain dependencies of resistivity and Young’s modulus of -oriented InAs nanowires on defect density and diameter. It was found that the higher is the defect density the higher are the resistivity and the Young’s modulus. Regarding the resistivity, it was deduced that the stacking faults increase the scattering of the electrons in the nanowire. These findings are consistent with the literature, however, the effect described by the other groups is not so pronounced. This difference can be attributed to the significant incompleteness of the physical models used for the data analysis. Regarding the elastic modulus, there are several mechanisms affecting the elasticity of the nanowires discussed in the thesis. It was found that the lattice distortion due to stacking fault does not affect the Young’s modulus significantly. The effect of electron density redistribution is suggested as the main aspect which is responsible for an enhancement of the Young’s modulus by up to 200%. This study suggests that both electrical and elastic properties of the InAs nanowires can be tuned by changing the defect density. Der Elektronentransport und die elastischen Eigenschaften von InAs Nanodrähten, die durch chemische Gasphasenabscheidung auf einem InAs (001) Substrat gewachsen worden sind, wurden experimentell, in-situ in einem Transmissionselektronenmikroskop (TEM) untersucht. Ein TEM-Probenhalter ermöglicht die Messung einer Nanokraft während der gleichzeitigem Abbildung der Biegung eines Nanodrahts. Beugungsbilder aus lokalen Bereichen eines Drahtes wurden aufgezeichnet, um elastische Eigenschaften mit der atomaren Struktur der Nanodrähte zu korrelieren. Ein anderer TEM-Halter erlaubt das Anlegen einer elektrischen Spannung, bei gleichzeitiger Abbildung des Nanodrahts im TEM bzw. der Durchführung von Elektronenholographie. Mit diesem TEM-Halter wurden echanische Schwingungen sowie in einer Elektronentransportuntersuchung mittels Holographie das innere Potential des Nanodrahts beobachtet. Diese Kombination der Rastersondenmethoden mit einem TEM ermöglicht es, die gemessenen elektrischen und elastischen Eigenschaften der Nanodrähte mit der direkten Identifizierung ihrer atomaren Struktur zu korrelieren. Es wurde festgestellt, dass die Nanodrähte verschiedene atomare Strukturen und verschiedene Stapelfehlerdefektdichten haben, die sich kritisch auf die elastischen und elektrischen Eigenschaften auswirken. Die Methoden, die in dieser Arbeit angewendet wurden, ermöglichen es, Abhängigkeiten des elektrischenWiderstandes und des Elastizitätsmoduls von Defektdichte und Durchmesser von -orientierten InAs-Nanodrähten zu erhalten. Es stellte sich heraus, dass je höher die Defektdichte ist, umso höher sind der Widerstand und der Young-Modulus. Hinsichtlich des Widerstandes wurde gefolgert, dass die Stapelfehler die Streuung der Elektronen im Nanodraht erhöhen. Diese Ergebnisse stimmen mit der Literatur überein, jedoch wird der Effekt durch die anderen Gruppen nicht so ausgeprägt beschrieben. Dieser Unterschied kann auf die nicht hinreichende Kombination und Korrelation der physikalischen Modelle, die für die Datenanalyse verwendet wurden, zurückgeführt werden. Hinsichtlich des Elastizitätsmoduls gibt es verschiedene Mechanismen, die die Elastizität der Nanodrähte beeinflussen und in dieser Dissertation diskutiert werden. Es wurde herausgefunden, dass Gitterverzerrungen aufgrund von Stapelfehlern den Elastizitätsmodul nicht entscheidend beeinflussen. Der Effekt der Umverteilung der Elektronendichte wird als Hauptaspekt vorgeschlagen, der für eine Verstärkung des Young-Moduls von bis zu 200 % verantwortlich ist. Diese Arbeit zeigt, dass sowohl elektrische als auch elastische Eigenschaften der Nanodrähte durch Ändern der Defektdichte eingestellt werden können.