Lukas Grünewald

Karlsruhe Institute of Technology | KIT · Laboratory for Electron Microscopy

Microplasmas can be used for a wide range of technological applications and to improve our understanding of fundamental physics. Scanning electron microscopy, on the other hand, provides insights into the sample morphology and chemistry of materials from the mm-down to the nm-scale. Combining both would provide direct insight into plasma-sample int...

The critical current density of superconducting rare-earth barium copper oxide (REBCO) thin films is enhanced by adding nanoparticles to generate artificial pinning centers. Barium-based perovskites are popular nanoparticle materials. Although typically considered chemically unreactive in the surrounding REBCO matrix, previous studies have shown ex...

High-entropy oxide (HEO) superconductors have been developed since very recently. Different superconductors can be produced in the form of a high-entropy compound, including REBa2Cu3O7−d (REBCO). However, until now, mainly bulk samples (mostly in polycrystalline form) have been reported. In this work, the first CSD-grown high-entropy (HE) REBCO nan...

In order to improve the electrical transport properties of REBa2Cu3O7−δ nanocomposite films, SmBa2Cu3O7-δ films with and without BaHfO3 nanoparticles were grown by chemical solution deposition (CSD), and their microstructural and transport properties were investigated in a detailed study using transmission electron microscopy and transport measurem...

Superconducting materials enable lossless current transport, bringing them into focus for technical applications. Particularly relevant are epitaxially grown thin films of high-temperature superconductors, like the Fe- and Cu-based materials Ba(Fe0.92Co0.08)2As2 (Ba122) and REBa2Cu3O7−δ (REBCO, with rare-earth elements, REs, such as Y, Sm, Gd, ...,...

Thin-film technology is used in many applications and often requires structural and chemical analyses on the nanoscale. (Scanning) transmission electron microscopy ((S)TEM) in a dedicated (S)TEM instrument is a powerful analysis tool for this purpose. However, the TEM sample preparation and consecutive (S)TEM measurement in different instruments li...

GdBa2Cu3O7−δ (GdBCO) is a promising high-temperature superconductor with potential application as coated conductor for power applications (e.g. transformers). However, further improvements in cost-effectiveness and superconducting properties are desired. The latter are influenced by O content, film texture, and film quality, where non-superconducti...

Thin films of Co-doped BaFe 2 As 2 of similar thickness (~40 nm) were grown with different growth rates (0.4 Å s ⁻¹ and 0.9 Å s ⁻¹ ) by pulsed laser deposition on CaF 2 (001) substrates. Analytical transmission electron microscopy (TEM) was applied to analyze the microstructure and secondary phases. The formation of BaF 2 and a high concentration o...

Zenodo repository containing supplementary information for the journal article 'Structural and chemical properties of superconducting Co‑doped BaFe2As2 thin films grown on CaF2'. The Jupyter notebooks (.ipynb) demonstrate data treatment for Fig. 4b (folder "HyperSpy EDXS Analysis") and Fig. 10a (folder "Atomap"). The notebooks can be run with the...

Quasi-multilayer films with perovskite nano-particles have already been investigated and reported in YBCO compounds. Here, we introduce this technique to iron based superconductors by preparing quasi-multilayer nanocomposite films of Co-doped BaFe2As2 with BaZrO3 and BaHfO3 perovskite nanoparticles by a pulsed laser deposition technique using a fre...

Nano-structured phase masks offer intriguing possibilities in electron-beam shaping. The fabrication of such phase masks is typically achieved by focused (Ga+-)ion beam milling of thin membranes. To overcome the problem of Ga implantation in the phase mask, we explore the fabrication of silicon-nitride phase masks using thermal scanning probe litho...

Electron microscopy of Ba(Fe,Co)2As2 thin films on LAO, MgO, and CaF2.

The competition between phase formation of BaF2 and Ba(Fe1-xCox)2As2 on CaF2 single crystals has been analysed. Ba(Fe0.92Co0.08)2As2 thin films have been deposited by pulsed laser deposition. X-ray diffraction, atomic force microscopy and scanning electron microscopy studies have revealed that the formation of secondary phases and misorientations a...

Background: Electron-beam shaping opens up the possibility for novel imaging techniques in scanning (transmission) electron microscopy (S(T)EM). Phase-modulating thin-film devices (phase masks) made of amorphous silicon nitride are commonly used to generate a wide range of different beam shapes. An additional conductive layer on such a device is re...

Electron-beam shaping opens up novel imaging possibilities in electron microscopy (EM). The implementation of a phase or amplitude mask in the condenser lens system allows the generation of electron beams with various shapes. Non-diffractive Bessel beams (BBs) are of interest for numerous applications due to their extraordinary large depth of focus...

The application of mixed ionic–electronic conducting (Ba0.5Sr0.5)(Co0.8Fe0.2)O3−δ (BSCF) as gas separation membrane is up to now hampered by secondary phase formation which impairs the excellent oxygen permeation properties of this material. In this work, we have studied the impact of grain size and A/B-cation ratio on secondary phase formation in...