Presented are the physics and chemistry of an important class of grain boundary types in oxide ceramics, which is characterized by a depletion of the major charge carrier in an area around the grain ...boundary core. Experimental results obtained in the time domain and in the frequency domain are shown for acceptor-doped titanates as the model material. The space charge layer width as well as the electronic and ionic charge transport across the grain boundary barrier, as a function of all relevant parameters, are taken from the results of the impedance analysis. A comprehensive and quantitative model is established which explains the experimental findings on the basis of the point defect structure and the Poisson equation. Depending on the height of the potential barrier at the grain boundary, inversion layers close to the grain boundary occur. Under long-term d.c. voltage stress, a macroscopic de-mixing of ionic defects takes place in these materials which lead to resistance degradation effects. The impact of grain boundaries on these phenomena and on the chemical diffusion processes is described.
Tantalum oxide (TaO x ) is an advantageous material system to realize complementary resistive switches, but the ON-window starts to shrink after a few cycles in the voltage sweep mode. A power ...analysis reveals the presence of power boosts during conventional voltage sweeps in the nonswitching part cell. This power stress is significantly reduced by the use of current sweeps with voltage compliance, leading to very reproducible switching. The endurance is raised to >; 30000 cycles.
Pr0.2Ba0.8CoO3-δ (PBCO) and Ba0.5Sr0.5Co0.5Fe0.5O3-δ (BSCF) perovskite thin film electrodes were used as model systems for testing degradation and stability during oxygen evolution reaction (OER) in ...alkaline water electrolysis. The catalyst films were prepared by chemical solution deposition (CSD) and are binder-free. Stepwise aging experiments illustrate a systematical approach to different degrees of degradation of the perovskites after defined testing cycles of cyclic voltammetry in application-near conditions. XPS and EDX characterization at each aging step enables a monitoring of the change in chemical composition during degradation. XPS analysis points to a change in the defect chemistry of PBCO during degradation. The influence of all monitored parameters on the overall electrode service lifetime is shown in a novel end of service life test (ESLT) at thin film perovskite electrodes of 100nm thickness.
Lateral electrochemical metallization (ECM) cells are fabricated with a combined spacer/damascene process. The process allows the realization of nanoscale geometrical distances between the two ...electrodes independent of lithography. Such lateral ECM cells are an essential part in a reconfigurable interconnect system that may yield a strongly increased connectivity in artificial neural networks. The lateral cells show memristive properties comparable to vertical cells with switching voltages in the range of -1.5 V to 2.5 V. The influence of electrode line edge roughness on SET kinetics of such lateral cells is investigated via kinetic Monte Carlo simulations, finding a minor influence on SET time variability.
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