Reconstruction of Angstrom resolution exit-waves by the application of drift-corrected phase-shifting off-axis electron holography.

Phase-shifting electron holography is an excellent method to reveal electron wave phase information with very high phase sensitivity over a large range of spatial frequencies. It circumvents the limiting trade-off between fringe spacing and visibility of standard off-axis holography. Previous implementations have been limited by the independent drift of biprism and sample.

Advancements in Liquid Jet Technology and X-ray Spectroscopy for Understanding Energy Conversion Materials during Operation.

ConspectusWater splitting is intensively studied for sustainable and effective energy storage in green/alternative energy harvesting-storage-release cycles. In this work, we present our recent developments for combining liquid jet microtechnology with different types of soft X-ray spectroscopy at high-flux X-ray sources, in particular developed for studying the oxygen evolution reaction (OER). We are particularly interested in the development of photon-in/photon-out techniques, such as in situ resonant inelastic X-ray scattering (RIXS) techniques at high-repetition-frequency X-ray sources, pointing toward capabilities.

Langmuir analysis of electron beam induced plasma in environmental TEM.

The characterisation of the gas state under electron impact is of high importance for the understanding of materials in-situ environmental transmission electron microscopy (ETEM) experiments. We report on the formation of a dilute plasma state of Ar and He based on the development of a Langmuir probe as a plasma diagnostic tool for the differentially pumped volume at the TEM sample position in the octagon. In order to keep stray magnetic field influences of the objective lens small, and thus the results readily interpretable within existing theory, the experiments are performed in Lorentz mode.

Atomistic Insights into Activation and Degradation of LaSrCoO Electrocatalysts under Oxygen Evolution Conditions.

The stability of perovskite oxide catalysts for the oxygen evolution reaction (OER) plays a critical role in their applicability in water splitting concepts. Decomposition of perovskite oxides under applied potential is typically linked to cation leaching and amorphization of the material. However, structural changes and phase transformations at the catalyst surface were also shown to govern the activity of several perovskite electrocatalysts under applied potential.

Phase Transitions in a Perovskite Thin Film Studied by Environmental In Situ Heating Nano-Beam Electron Diffraction.

The rich phase diagram of bulk Pr Ca MnO resulting in a high tunability of physical properties gives rise to various studies related to fundamental research as well as prospective applications of the material. Importantly, as a consequence of strong correlation effects, electronic and lattice degrees of freedom are vigorously coupled. Hence, it is debatable whether such bulk phase diagrams can be transferred to inherently strained epitaxial thin films.

Reusable Manganese Catalyst for Site-Selective Pyridine C-H Arylations and Alkylations.

Herein, we disclose a recyclable, hybrid manganese catalyst for site-selective azine C-H activation by weak amide assistance. The novel, reusable catalyst enabled C3-H arylation and C3-H alkylation with ample scope, and was characterized by detailed transmission electron microscopy analysis.

Site-specific plan-view TEM lamella preparation of pristine surfaces with a large field of view.

Transmission electron microscopy has become a major characterization tool with an ever increasing variety of methods being applied in a wide range of scientific fields. However, the probably most famous pitfall in related workflows is the preparation of high-quality electron-transparent lamellae enabling for extraction of valuable information. Particularly in the field of solid state physics and materials science, it often required to study the surface of a macroscopic specimen with plan-view orientation.

Polaronic Contributions to Friction in a Manganite Thin Film.

Despite the huge importance of friction in regulating movement in all natural and technological processes, the mechanisms underlying dissipation at a sliding contact are still a matter of debate. Attempts to explain the dependence of measured frictional losses at nanoscale contacts on the electronic degrees of freedom of the surrounding materials have so far been controversial. Here, it is proposed that friction can be explained by considering the damping of stick-slip pulses in a sliding contact.

A dinuclear rhenium complex in the electrochemically driven homogeneous and heterogeneous H/CO-reduction.

A dinculear Re(CO)3 complex with a proton responsive phenol unit and a pyrene anchor in the ligand backbone was investigated in the electrochemical CO2/H+ conversion in solution and adsorbed on multi walled carbon nanotubes (MWCNT) on an GC electrode surface. The pyrene group unit is introduced at the end of the ligand synthesis via a coupling reaction, which allows for a versatile ligand modification in order to tune the electronic properties or to introduce various anchor groups for heterogenisation at a late stage. The redox chemistry of the pyrene-α-diimine-Re(CO)3 complex, 1, was investigated in N,N-dimethylformamide (dmf), including IR-spectroelectrochemical (IR-SEC) characterisation of the short lived, reduced species.

Photoinduced Heterogeneous C-H Arylation by a Reusable Hybrid Copper Catalyst.

Heterogeneous copper catalysis enabled photoinduced C-H arylations under exceedingly mild conditions at room temperature. The versatile hybrid copper catalyst provided step-economical access to arylated heteroarenes, terpenes and alkaloid natural products with various aryl halides. The hybrid copper catalyst could be reused without significant loss of catalytic efficacy.

A zone-plate-based two-color spectrometer for indirect X-ray absorption spectroscopy.

X-ray absorption spectroscopy (XAS) is a powerful element-specific technique that allows the study of structural and chemical properties of matter. Often an indirect method is used to access the X-ray absorption (XA). This work demonstrates a new XAS implementation that is based on off-axis transmission Fresnel zone plates to obtain the XA spectrum of LaSrMnO by analysis of three emission lines simultaneously at the detector, namely the O 2p-1s, Mn 3s-2p and Mn 3d-2p transitions.

Developing an in situ environmental TEM set up for investigations of resistive switching mechanisms in Pt-PrCaMnO-Pt sandwich structures.

Non-volatile resistance change under electric stimulation in many metal-oxides is a promising path to next generation memory devices. However, the underlying mechanisms are still not fully understood. In situ transmission electron microscopy experiments provide a powerful tool to elucidate these mechanisms.

Oxygen Evolution at Manganite Perovskite Ruddlesden-Popper Type Particles: Trends of Activity on Structure, Valence and Covalence.

An improved understanding of the correlation between the electronic properties of Mn-O bonds, activity and stability of electro-catalysts for the oxygen evolution reaction (OER) is of great importance for an improved catalyst design. Here, an in-depth study of the relation between lattice structure, electronic properties and catalyst performance of the perovskite CaPrMnO₃ and the first-order RP-system CaPrMnO₄ at doping levels of x = 0, 0.25 and 0.

Charge attachment induced transport - bulk and grain boundary diffusion of potassium in PrMnO.

The transport of potassium through praseodymium-manganese oxide (PrMnO; PMO) has been investigated by means of the charge attachment induced transport (CAIT) technique. To this end, potassium ions have been attached to the front side of a 250 nm thick sample of PMO. The majority of the potassium ions become neutralized at the surface of the PMO, while some of the potassium ions diffuse through.

meta-C-H Bromination on Purine Bases by Heterogeneous Ruthenium Catalysis.

Methods for positionally selective remote C-H functionalizations are in high demand. Herein, we disclose the first heterogeneous ruthenium catalyst for meta-selective C-H functionalizations, which enabled remote halogenations with excellent site selectivity and ample scope. The versatile heterogeneous Ru@SiO catalyst was broadly applicable and could be easily recovered and reused, which set the stage for the direct fluorescent labeling of purines.

An endstation for resonant inelastic X-ray scattering studies of solid and liquid samples.

A novel experimental setup is presented for resonant inelastic X-ray scattering investigations of solid and liquid samples in the soft X-ray region for studying the complex electronic configuration of (bio)chemical systems. The uniqueness of the apparatus is its high flexibility combined with optimal energy resolution and energy range ratio. The apparatus enables investigation of chemical analyses, which reflects the chemical imprints.

Current-voltage characteristics of manganite-titanite perovskite junctions.

After a general introduction into the Shockley theory of current voltage (J-V) characteristics of inorganic and organic semiconductor junctions of different bandwidth, we apply the Shockley theory-based, one diode model to a new type of perovskite junctions with polaronic charge carriers. In particular, we studied manganite-titanate p-n heterojunctions made of n-doped SrTi1- y Nb y O3, y = 0.002 and p-doped Pr1- x Ca x MnO3, x = 0.

In situ TEM analysis of resistive switching in manganite based thin-film heterostructures.

The mechanism of the electric-pulse induced resistance change effect in Au/Pr0.65Ca0.35MnO3/SrTi0.

Time-resolved near-edge x-ray absorption fine structure spectroscopy on photo-induced phase transitions using a tabletop soft-x-ray spectrometer.

We present a table-top soft-x-ray spectrometer for the wavelength range λ = 1-5 nm based on a stable laser-driven x-ray source, making use of a gas-puff target. With this setup, optical light-pump/soft-x-ray probe near-edge x-ray absorption fine structure (NEXAFS) experiments with a temporal resolution of about 230 ps are feasible. Pump-probe NEXAFS measurements were carried out in the "water-window" region (2.

Polaron melting and ordering as key mechanisms for colossal resistance effects in manganites.

Polarons, the combined motion of electrons in a cloth of their lattice distortions, are a key transport feature in doped manganites. To develop a profound understanding of the colossal resistance effects induced by external fields, the study of polaron correlations and the resulting collective polaron behavior, i.e.

Enhanced current transport at grain boundaries in high-T(c) superconductors.

Large-scale applications of high-transition-temperature (high-T(c)) superconductors, such as their use in superconducting cables, are impeded by the fact that polycrystalline materials (the only practical option) support significantly lower current densities than single crystals. The superconducting critical current density (J(c)) across a grain boundary drops exponentially if the misorientation angle exceeds 2 degrees -7 degrees. Grain texturing reduces the average misorientation angle, but problems persist.

Direct evidence for negative grain boundary potential in Ca-doped and undoped YBa2Cu3O7-x.

Using electron holography in a transmission electron microscope, we obtained direct evidence for the reduction of negative charge at grain boundary dislocations in Ca-doped YBa2Cu3O7 (YBCO) when compared to undoped YBCO. Because of the finite width of the valence band in the superconducting CuO2 planes, the negative grain boundary charge can lead to a depletion of electron holes available for superconductivity. A significant reduction in the size of the perturbed region in the Ca-doped samples appears to be the principal mechanism for the improved interfacial superconductivity.