A5003154231- Electrocatalysts for Energy Conversion
- Electronic and Structural Properties of Oxides
- Electrochemical Analysis and Applications
- Advanced Memory and Neural Computing
- Fuel Cells and Related Materials
- Magnetic and transport properties of perovskites and related materials
- Ferroelectric and Negative Capacitance Devices
- X-ray Diffraction in Crystallography
- Neuroscience and Neural Engineering
- Advancements in Solid Oxide Fuel Cells
- Semiconductor materials and devices
- Crystallization and Solubility Studies
- Advanced battery technologies research
- Transition Metal Oxide Nanomaterials
- Ferroelectric and Piezoelectric Materials
- Electron and X-Ray Spectroscopy Techniques
- Conducting polymers and applications
- Perovskite Materials and Applications
- Graphene research and applications
- Photoreceptor and optogenetics research
- Iron oxide chemistry and applications
- Advanced Condensed Matter Physics
- High Entropy Alloys Studies
- Surface and Thin Film Phenomena
- Multiferroics and related materials
Forschungszentrum Jülich
2016-2025
University of Twente
2021-2025
Institute of Nanotechnology
2025
Stanford University
2021-2022
SLAC National Accelerator Laboratory
2021-2022
RWTH Aachen University
2013-2022
Jülich Aachen Research Alliance
2018-2022
Chan Heart Rhythm Institute
2020
University of Illinois Urbana-Champaign
2013-2015
The control and rational design of redox-based memristive devices, which are highly attractive candidates for next-generation nonvolatile memory logic applications, is complicated by competing poorly understood switching mechanisms, can result in two coexisting resistance hystereses that have opposite voltage polarity. These processes be defined as regular anomalous resistive switching. Despite significant characterization efforts, the complex nanoscale redox drive their implications current...
High-entropy materials are an emerging pathway in the development of high-activity (electro)catalysts because inherent tunability and coexistence multiple potential active sites, which may lead to earth-abundant catalyst for energy-efficient electrochemical energy storage. In this report, we identify how multication composition high-entropy perovskite oxides (HEO) contributes high catalytic activity oxygen evolution reaction (OER), i.e., key kinetically limiting half-reaction several...
The next technological leap forward will be enabled by new materials and inventive means of manipulating them. Among the array candidate materials, graphene has garnered much attention; however, due to absence a semiconducting gap, realization graphene-based devices often requires complex processing design. Spatially controlled local potentials, for example, achieved through lithographically defined split-gate configurations, present possible route take advantage this exciting...
Abstract The demand for highly scalable, low-power devices data storage and logic operations is strongly stimulating research into resistive switching as a novel concept future non-volatile memory devices. To meet technological requirements, it imperative to have set of material design rules based on fundamental physics, but deriving such proving challenging. Here, we elucidate both mechanism failure in the valence-change model SrTiO 3 , this basis derive rule failure-resistant...
Bidirectional interdependency between graphene doping level and ferroelectric polarization is demonstrated in graphene/PbZr0.2Ti0.8O3 hybrid structures. The of the PbZr0.2Ti0.8O3 can be effectively switched with electrodes turn alter carrier type density graphene. A complete reversal current–voltage hysteresis direction observed when external environmental factors are minimized, converting p-type into n-type an estimated change as large ∼1013 cm–2. Nonvolatility reversibility also demonstrated.
A major obstacle for the implementation of redox-based memristive memory or logic technology is large cycle-to-cycle and device-to-device variability. Here, we use spectromicroscopic photoemission threshold analysis operando XAS to experimentally investigate microscopic origin We find that some devices exhibit variations in shape conductive filament oxygen vacancy distribution at around filament. In other cases, even location active changes from one cycle next. propose both effects originate...
Abstract The continuing revolutionary success of mobile computing and smart devices calls for the development novel, cost- energy-efficient memories. Resistive switching is attractive because of, inter alia, increased speed device density. On electrical stimulus, complex nanoscale redox processes are suspected to induce a resistance change in memristive devices. Quantitative information about these processes, which has been experimentally inaccessible so far, essential further advances. Here...
Redox-based memristive devices are one of the most attractive candidates for future nonvolatile memory applications and neuromorphic circuits, their performance is determined by redox processes corresponding oxygen-ion dynamics. In this regard, brownmillerite SrFeO2.5 has been recently introduced as a novel material platform due to its exceptional transport properties resistive-switching devices. However, underlying that give rise resistive switching remain poorly understood. By using X-ray...
The stability of perovskite oxide catalysts for the oxygen evolution reaction (OER) plays a critical role in their applicability water splitting concepts. Decomposition oxides under applied potential is typically linked to cation leaching and amorphization material. However, structural changes phase transformations at catalyst surface were also shown govern activity several electrocatalysts potential. Hence, it crucial rational design durable understand interplay between formation active...
Abstract Their suggested stability towards high‐voltage cathode materials makes halide‐based solid electrolytes currently an interesting class of ionic conductors for solid‐state batteries. Especially the LiMn 2 O 4 spinel active material is interest due to its slightly higher nominal voltage and more resilience overcharging compared LiCoO LiNi x Mn y Co z cathodes. Typically, a standard ratio electrolyte used in composites However, ideal transport properties, thus achieve balanced optimal...
Abstract Solid‐state dewetting is the heat‐induced agglomeration of thin metal films into defined nanoparticles (NPs). Dewetted Pt are investigated on F‐doped SnO 2 (FTO) substrates as model binder‐free electrodes for hydrogen evolution reaction (HER). Dewetting particles exposes FTO substrate and metal/support (Pt‐FTO) contact line. Despite decrease in electrochemical surface area (ECSA) upon dewetting, dewetted NPs show a >3‐fold increase ECSA‐normalized HER activity compared to...
To reach a long term viable green hydrogen economy, rational design of active oxygen evolution reaction (OER) catalysts is critical. An important hurdle in this originates from the fact that reactants are singlet molecules, whereas molecule has triplet ground state with parallel spin alignment, implying magnetic order catalyst essential. Accordingly, multiple experimentalists reported positive effect external fields on OER activity ferromagnetic catalysts. However, it remains challenge to...
Nanoscale redox reactions in transition metal oxides are believed to be the physical foundation of memristive devices, which present a highly scalable, low-power alternative for future non-volatile memory devices. The interface between noble top electrodes and Nb-doped SrTiO3 single crystals may serve as prominent but not yet well-understood example such In this report, we will experimental evidence that nanoscale associated valence change mechanism indeed responsible resistance...
Abstract Resistive switching based on transition metal oxide memristive devices is suspected to be caused by the electric‐field‐driven motion and internal redistribution of oxygen vacancies. Deriving detailed mechanistic picture process complicated, however, frequently observed influence surrounding atmosphere. Specifically, presence or absence water vapor in atmosphere has a strong impact properties, but redox reactions between active layer have yet clarified. To investigate role species...
The sustainable development of IT-systems requires a quest for novel concepts to address further miniaturization, performance improvement, and energy efficiency devices. realization these goals cannot be achieved without an appropriate functional material. Herein, we target the technologically important electron modification using single polyoxometalate (POM) molecules envisaged as smart successors materials that are implemented in today's complementary metal-oxide-semiconductor (CMOS)...
The Co-O covalency in perovskite oxide cobaltites such as La1-xSrxCoO3 is believed to impact the electrocatalytic activity during electrochemical water splitting at anode where oxygen evolution reaction (OER) takes place. Additionally, space charge layers through band bending interface electrolyte may affect electron transfer into electrode, complicating analysis and identification of true OER descriptors. Here, we separate influence hybrid epitaxial bilayer structures highly OER-active...
Using atomically flat SrIrO 3 as a model electrocatalyst for water oxidation, we study the interplay between Sr 2+ leaching and perovskite dissolution at nanometer scale through electrochemical atomic force microscopy.
Abstract Vapor deposition of halide perovskites presents high potential for scalability and industrial processing perovskite solar cells. It prevents the use toxic solvents, allows thickness control, yields conformal uniform coating over large areas. However, distinct volatility organic inorganic components currently requires multiple thermal sources or two‐step to achieve phase. In this work, single‐source, single‐step MA 1–x FA x PbI 3 thin film with tunable stoichiometry by pulsed laser...
Electrocatalysts are the cornerstone in transition to sustainable energy technologies and chemical processes. Surface transformations under operation conditions dictate activity stability. However, dependence of surface structure transformation on exposed crystallographic facet remains elusive, impeding rational catalyst design. We investigate (001), (110) (111) facets a LaNiO3-δ electrocatalyst for water oxidation using electrochemical measurements, X-ray spectroscopy, density functional...
In this study, we investigated the influence of oxygen non-stoichiometry on resistive switching performance tantalum oxide based memristive devices. Thin-films were deposited with varying sputter power and partial pressure. The electroforming voltage was found to decrease increasing density or decreased pressure, while endurance remained stable resistance window ROFF/RON increase. In-depth XPS analysis connects these observations a controllable sub-stoichiometry in sputter-deposited films....
We study the electrocatalytic oxygen evolution reaction using in situ X-ray absorption spectroscopy (XAS) to track dynamics of valence state and covalence metal ions LaFeO3 LaFeO3/LaNiO3 thin films. The active materials are 8 unit cells grown epitaxially on 100 nm conductive La0.67Sr0.33MnO3 layers pulsed laser deposition (PLD). perovskite supported monolayer Ca2Nb3O10 nanosheet-buffered SiNx membranes. Fe Ni K-edges XAS spectra were measured from backside membrane fluorescence yield...
Abstract The wide tunability of strongly correlated transition metal (TM) oxides stems from their complex electronic properties and the coupled degrees freedom. Among perovskite family, LaMO 3 (M = Ti-Ni) allows an M-dependent systematic study structure within same-structure-family motif. While most studies have been focusing on 3d TMs oxygen sites, role rare-earth site has far less explored. In this work, we use resonant inelastic X-ray scattering (RIXS) at lanthanum N 4,5 edges density...
Abstract Emerging electrical and magnetic properties of oxide interfaces are often dominated by the termination stoichiometry substrates thin films, which depend critically on growth conditions. Currently, these quantities have to be measured separately with different sophisticated techniques. This report will demonstrate that analysis angle dependent X-ray photoelectron intensity ratios provides a unique tool determine both simultaneously in straightforward experiment. Fitting experimental...
Abstract Among the novel materials for electronic applications and device concepts beyond classical Si‐based CMOS technology, SrTiO 3 represents a prototype role model functional oxide materials: It enables resistive switching, but can also form 2D electron gas at its interface thus tunable transistors. However, interplay between charge carriers defects in is still under debate. Infrared spectroscopy offers possibility to characterize structural properties of operando, hampered by...