# Zweitveröffentlichungen (grüner Weg)

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### Auflistung Zweitveröffentlichungen (grüner Weg) nach Auflistung nach Fachbereich/Einrichtung "FB 07 - Mathematik und Informatik, Physik, Geographie"

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Item 3D Impedance Modelling of Metal Anodes in Solid-State Batteries − Incompatibility of Pore Formation and Constriction Effect in Physical-Based 1D Circuit Models(2022-09-08) Eckhardt, Janis K.; Fuchs, Till; Burkhardt, Simon; Klar, Peter J.; Janek, Jürgen; Heiliger, ChristianA non-ideal contact at the electrode/solid electrolyte interface of a solid-state battery arising due to pores (voids) or inclusions results in a constriction effect that severely deteriorates the electric transport properties of the battery cell. The lack of understanding of this phenomenon hinders the optimization process of novel components, such as reversible and high-rate metal anodes. Deeper insight into the constriction phenomenon is necessary to correctly monitor interface degradation and to accelerate the successful use of metal anodes in solid-state batteries. Here, we use a 3D electric network model to study the fundamentals of the constriction effect. Our findings suggest that dynamic constriction as a non-local effect cannot be captured by conventional 1D equivalent circuit models and that its electric behavior is not ad hoc predictable. It strongly depends on the interplay of the geometry of the interface causing the constriction and the microscopic transport processes in the adjacent phases. In the presence of constriction, the contribution from the non-ideal (porous) electrode/solid electrolyte interface to the impedance spectrum may exhibit two signals that cannot be explained when the porous interface is described by a physical-based (effective medium theory) 1D equivalent circuit model. In consequence, the widespread assumption of a single interface contribution to the experimental impedance spectrum may be entirely misleading and can cause serious misinterpretation.Item A differential delay equation with a planar attractor(1991) Walther, Hans-OttoItem A theorem on the amplitudes of periodic solutions of delay equations, with an application to bifurcation(1978) Walther, Hans-OttoItem A uniqueness problem for a nonlinear differential delay equation(1985) Walther, Hans-OttoItem Algebraic-delay differential systems, state-dependent delay, and temporal order of reactions(2008) Walther, Hans-OttoInitial value problems for differential equations with delay.Item An invariant manifold of slowly oscillating solutions for xpunkt(t) = - müx(t) + f(x(t-1))(1991) Walther, Hans-OttoItem Asymptotic stability for some functional differential equations(1991) Walther, Hans-OttoItem Auger recombination rates in ZnMgO from first principles(2011) Heinemann, Markus; Heiliger, ChristianWe investigate direct electron-electron-hole interband Auger recombination for wurtzite Zn(1-x)Mg(x)O alloys in the range 0 <= x <= 1. Recombination rates are computed by interpolating the band structure and transition matrix elements from ab initio calculations of bulk ZnO, Zn(0.5)Mg(n0.5)O, and MgO primitive cells. We find that interband Auger recombination is most probable for Mg concentrations around 50%, where ZnMgO does not exist in a stable wurtzite phase. Since, for low Mg concentrations, the calculated Auger coefficients are far below 10(-32) cm(6)/s, we do not expect significant nonradiative loss through direct interband recombination in wurtzite ZnMgO.Item The band alignment of Cu2O/ZnO and Cu2O/GaN heterostructures(2012) Kramm, B.; Laufer, A.; Reppin, D.; Kronenberger, A.; Hering, P.; Polity, A.; Meyer, B. K.Using photoelectron spectroscopy, we investigate the band alignments of the Cu2O/ZnO heterointerface and compare the findings with the corresponding values for Cu2O/GaN. While for Cu2O/ZnO, we find a valence band offset (VBO) of 2.17 eV and a conduction band offset (CBO) of 0.97 eV, both values are considerably reduced for Cu2O/GaN where the numbers are 1.47 eV (VBO) and 0.24 eV (CBO), respectively. The large CBO between ZnO and Cu2O will very likely result in low photovoltaic power conversion efficiencies as is the current status of Cu2O/ZnO solar cells.Item Bifurcation from a heteroclinic solution in differential delay equations(1985) Walther, Hans-OttoItem Item Bifurcation from homoclinic to periodic solutions by an inclination lemma with pointwise estimate(1987) Walther, Hans-OttoItem Bifurcation from periodic solutions in functional differential equations(1983) Walther, Hans-OttoItem Delay equations : Instability and the trivial fixed points index(1981) Walther, Hans-OttoItem Density of slowly oscillating solutions of xPunkt(t) = -f(x(t-1))(1981) Walther, Hans-OttoItem Determination of secondary ion mass spectrometry relative sensitivity factors for polar and non-polar ZnO(2011) Laufer, Andreas; Volbers, Niklas; Eisermann, Sebastian; Potzger, Kay; Geburt, Sebastian; Ronning, Carsten; Meyer, Bruno K.Zinc oxide (ZnO) is regarded as a promising material for optoelectronic devices, due to its electronic properties. Solely, the difficulty in obtaining p-type ZnO impedes further progress. In this connection, the identification and quantification of impurities is a major demand. For quantitative information using secondary ion mass spectrometry (SIMS), so-called relative sensitivity factors (RSF) are mandatory. Such conversion factors did not yet exist for ZnO. In this work, we present the determined RSF values for ZnO using primary (ion implanted) as well as secondary (bulk doped) standards. These RSFs have been applied to commercially available ZnO substrates of different surface termination (a-plane, Zn-face, and O-face) to quantify the contained impurities. Although these ZnO substrates originate from the same single-crystal, we observe discrepancies in the impurity concentrations. These results cannot be attributed to surface termination dependent RSF values for ZnO.Item Diamondoid coating enables disruptive approach for chemical and magnetic imaging with 10nm spatial resolution(2012) Ishiwata, Hitoshi; Acremann, Yves; Scholl, Andreas; Rotenberg, Eli; Hellwig, Olav; Dobisz, Elizabeth; Doran, Andrew; Tkachenko, Boryslav A.; Fokin, Andrey A.; Schreiner, Peter R.; Dahl, Jeremy E. P.; Carlson, Robert M. K.; Melosh, Nick; Shen, Zhi-Xun; Ohldag, HendrikDiamondoids are unique molecular nano-materials with diamond structure and fascinating properties such as negative electron affinity and short electron mean free paths. A thin layer of diamondoids deposited on a cathode is able to act as an electron monochromator, reducing the energy spread of photo-emitted electrons from a surface. This property can be applied effectively to improve the spatial resolution in x-ray photoemission electron microscopy (X-PEEM), which is limited by chromatic aberration of the electron optics. In this paper, we present X-PEEM measurements reaching the technological relevant spatial resolution of 10?nm without the need of expensive and complex corrective optics. Our results provide a simple approach to image surface chemical and magnetic information at nanometer scales by employing diamondoids.Item Dynamics of feedback systems with time lag(1985) Walther, Hans-OttoItem Electron paramagnetic resonance and photo-electron paramagnetic resonance investigation on the recharging of the substitutional nitrogen acceptor in ZnO(2012) Stehr, J. E.; Hofmann, D. M.; Meyer, B. K.We investigated the substitutional nitrogen center in ZnO single crystals by electron paramagnetic resonance (EPR) and photo-EPR spectroscopy. Aside the three principle hyperfine lines due to the interaction of the N0 (2p5) electron spin with the nitrogen nucleus (I=1, natural abundance 99.6%), we identify additional satellite lines which arise from delta mS=±1 and delta mI=±1, ±2 transitions becoming allowed due to quadrupole interaction. The quadrupole coupling constant e2qQ/h is determined to -5.9MHz with an asymmetry parameter of eta=0.05. These values are somewhat different from those obtained for the nitrogen center in ZnO powders, but are closer to the theoretical calculations of Gallino et al. We further carefully investigated the photon induced recharging of the N centers. We determine the energy hu required for the process NO-+hu -> NO0+ecb- to 2.1±0.05eV, the dependence of the EPR signal intensity on the illumination time shows a mono-exponential behavior which gives evidence that a direct ionization process is monitored.

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