Nikolas Oehl

Carl von Ossietzky Universität Oldenburg · Department of Physics

Europe remains dependent on international cooperation to secure the supply of metals for batteries. Against the background of rising international tensions, resilient supply chains are thus becoming more important. It is therefore tremendously important for companies in the European battery ecosystem to diversify their supply chains. Influence on t...

For the first time, sub 10nm sized intermetallic Ag4Sn particles are prepared via an aqueous synthesis route in order to improve the electrochemical performance of pure Sn nanoparticles. High-resolution transmission electron microscopy, X-ray diffraction and thermogravimetric analysis were used to investigate the morphology, crystal structure and p...

In situ X-ray diffraction (XRD) was performed to study the formation of the $alpha$-Sn structure in nanocrystalline Sn-based electrodes during electrochemical lithium insertion and extraction at room temperature. Therefore, pure ß-Sn nanoparticles were synthesised and further processed to electrodes. The lithiation and de-lithiation process of the...

In this study, the crystallographic structure of orthorhombic $epsilon$-phase Ag3Sn nanoparticles with different sizes between 7 nm and 120 nm was studied by X-ray diffraction, and the influence of the size and the composition of the nanocrystals on the lattice parameters were investigated. Rietveld refinement was used to confirm the orthorhombic (...

Tin nanoparticles can be transformed from the metallic ß-Sn structure to the semiconducting $alpha$-Sn structure after electrochemical lithiation and delithiation at room temperature. Here, we studied the influence of the size of the crystallites on the ß- to $alpha$-transformation in Sn nanoparticles. Differently sized Sn/SnOx nanoparticles were s...

The lattice constants of metallic nanoparticles shrink with respect to that of a bulk material. This behavior affects the properties of nano-scaled crystallites and can influence their application potential. In this work, we investigate the size dependent lattice parameters of core-shell Sn/SnOx nanoparticles, synthesized via a simple chemical redu...

Tin is able to lithiate and delithiate reversibly with a high theoretical specific capacity, which makes it a promising candidate to supersede graphite as the state-of-the-art negative electrode material in lithium ion battery technology. Nevertheless, it still suffers from poor cycling stability and high irreversible capacities. In this contributi...

In this paper we report about the realization of high gain QD lasers for 1.55 µm optical fiber communication. Using a recently developed growth recipe, InAs/InAlGaAs/InP QD material with reduced inhomogeneous linewidth broadening of less than 30 meV was obtained [1]. QD ensembles with narrow spectral linewidths are very promising for high-speed low...

InP diode lasers with InAs quantum dot (QD) like active regions emitting at 1.55 μm have been fabricated. The QDs were grown in an As2 mode, which reduces the degree of elongation of the nanospecies yielding nearly circular shapes. Lasers with four to six dot layers show low absorption αi<10 cm−1 and high modal gain Γg0 of 10 cm−1 per QD layer (QDL...