Novel Insights into Enhanced Stability of Li-Rich Layered and High-Voltage Olivine Phosphate Cathodes for Advanced Batteries through Surface Modification and Electron Structure Design.

The design of cathode/electrolyte interfaces in high-energy density Li-ion batteries is critical to protect the surface against undesirable oxygen release from the cathodes when batteries are charged to high voltage. However, the involvement of the engineered interface in the cationic and anionic redox reactions associated with (de-)lithiation is often ignored, mostly due to the difficulty to separate these processes from chemical/catalytic reactions at the cathode/electrolyte interface. Here, a new electron energy band diagrams concept is developed that includes the examination of the electrochemical- and ionization- potentials evolution upon batteries cycling.

Weld-free mounting of lamellae for electrical biasing operando TEM.

Recent advances in microelectromechanical systems (MEMS)-based substrates and sample holders for in situ transmission electron microscopy (TEM) are currently enabling exciting new opportunities for the nanoscale investigation of materials and devices. The ability to perform electrical testing while simultaneously capturing the wide spectrum of signals detectable in a TEM, including structural, chemical, and even electronic contrast, represents a significant milestone in the realm of nanoelectronics. In situ studies hold particular promise for the development of Metal-Insulator-Metal (MIM) devices for use in next-generation computing.

Texture Transfer in Dielectric Layers via Nanocrystalline Networks: Insights from in Situ 4D-STEM.

Transition metal oxide dielectric layers have emerged as promising candidates for various relevant applications, such as supercapacitors or memory applications. However, the performance and reliability of these devices can critically depend on their microstructure, which can be strongly influenced by thermal processing and substrate-induced strain. To gain a more in-depth understanding of the microstructural changes, we conducted in situ transmission electron microscopy (TEM) studies of amorphous HfO dielectric layers grown on highly textured (111) substrates.

Element-Specific Study of Magnetic Anisotropy and Hardening in SmCoCu Thin Films.

This work investigates the effect of copper substitution on the magnetic properties of SmCo thin films synthesized by molecular beam epitaxy. A series of thin films with varying concentrations of Cu were grown under otherwise identical conditions to disentangle structural and compositional effects on the magnetic behavior. The combined experimental and theoretical studies show that Cu substitution at the Co sites not only stabilizes the formation of the SmCo structure but also enhances magnetic anisotropy and coercivity.

Impact of Strain Engineering on Antiferroelectricity in NaNbO Thin Films.

Thin films of NaNbO were grown on various substrates to investigate the effect of epitaxial strain on their structural and electrical properties. Reciprocal space maps confirmed the presence of epitaxial strain from +0.8% to -1.

Recent Advances and Future Prospects for Memristive Materials, Devices, and Systems.

Memristive technology has been rapidly emerging as a potential alternative to traditional CMOS technology, which is facing fundamental limitations in its development. Since oxide-based resistive switches were demonstrated as memristors in 2008, memristive devices have garnered significant attention due to their biomimetic memory properties, which promise to significantly improve power consumption in computing applications. Here, we provide a comprehensive overview of recent advances in memristive technology, including memristive devices, theory, algorithms, architectures, and systems.

Fast Fitting of the Dynamic Memdiode Model to the Conduction Characteristics of RRAM Devices Using Convolutional Neural Networks.

In this paper, the use of Artificial Neural Networks (ANNs) in the form of Convolutional Neural Networks (AlexNET) for the fast and energy-efficient fitting of the Dynamic Memdiode Model (DMM) to the conduction characteristics of bipolar-type resistive switching (RS) devices is investigated. Despite an initial computationally intensive training phase the ANNs allow obtaining a mapping between the experimental Current-Voltage () curve and the corresponding DMM parameters without incurring a costly iterative process as typically considered in error minimization-based optimization algorithms. In order to demonstrate the fitting capabilities of the proposed approach, a complete set of s obtained from YO-based RRAM devices, fabricated with different oxidation conditions and measured with different current compliances, is considered.

Tailoring Optical Properties in Transparent Highly Conducting Perovskites by Cationic Substitution.

SrMoO , SrNbO , and SrVO are remarkable highly conducting d (V, Nb) or d (Mo) perovskite metals with an intrinsically high transparency in the visible. A key scientific question is how the optical properties of these materials can be manipulated to make them suitable for applications as transparent electrodes and in plasmonics. Here, it is shown how 3d/4d cationic substitution in perovskites tailors the relevant materials parameters, i.

Structural and Electrical Response of Emerging Memories Exposed to Heavy Ion Radiation.

Hafnium oxide- and GeSbTe-based functional layers are promising candidates in material systems for emerging memory technologies. They are also discussed as contenders for radiation-harsh environment applications. Testing the resilience against ion radiation is of high importance to identify materials that are feasible for future applications of emerging memory technologies like oxide-based, ferroelectric, and phase-change random-access memory.

Controlling the Formation of Conductive Pathways in Memristive Devices.

Resistive random-access memories are promising candidates for novel computer architectures such as in-memory computing, multilevel data storage, and neuromorphics. Their working principle is based on electrically stimulated materials changes that allow access to two (digital), multiple (multilevel), or quasi-continuous (analog) resistive states. However, the stochastic nature of forming and switching the conductive pathway involves complex atomistic defect configurations resulting in considerable variability.

Enhanced Conductivity and Microstructure in Highly Textured TiN /-AlO Thin Films.

Titanium nitride thin films are used as an electrode material in superconducting (SC) applications and in oxide electronics. By controlling the defect density in the TiN thin film, the electrical properties of the film can achieve low resistivities and a high critical temperature ( ) close to bulk values. Generally, low defect densities are achieved by stoichiometric growth and a low grain boundary density.

Defect-Stabilized Substoichiometric Polymorphs of Hafnium Oxide with Semiconducting Properties.

Hafnium oxide plays an important role as a dielectric material in various thin-film electronic devices such as transistors and resistive or ferroelectric memory. The crystallographic and electronic structure of the hafnia layer often depends critically on its composition and defect structure. Here, we report two novel defect-stabilized polymorphs of substoichiometric HfO with semiconducting properties that are of particular interest for resistive switching digital or analog memory devices.

Energy Level Alignment at the Cobalt Phosphate/Electrolyte Interface: Intrinsic Stability vs Interfacial Chemical Reactions in 5 V Lithium Ion Batteries.

The intrinsic stability of the 5 V LiCoPO-LiCoPO thin-film (carbon-free) cathode material coated with MoO thin layer is studied using a comprehensive synchrotron electron spectroscopy in situ approach combined with first-principle calculations. The atomic-molecular level study demonstrates fully reversible electronic properties of the cathode after the first electrochemical cycle. The polyanionic oxide is not involved in chemical reactions with the fluoroethylene-containing liquid electrolyte even when charged to 5.

Structural and Magnetic Properties of BaFeO Synthesized by Oxidizing BaFeO Obtained via Nebulized Spray Pyrolysis.

A vacancy-ordered perovskite-type compound BaFeO (BaFeO) was prepared by oxidizing BaFeO (2/) with the latter compound obtained by a spray pyrolysis technique. The structure of BaFeO was found to be isotypic to BaFeOF (2/) and can be written as BaFeFeO. Mössbauer spectroscopy and calculations were used to confirm mixed iron oxidation states, showing allocation of the tetravalent iron species on the tetrahedral site, and octahedral as well as square pyramidal coordination for the trivalent species within a G-type antiferromagnetic ordering.

Epitaxy Induced Highly Ordered SmCo-SmCo Nanoscale Thin-Film Magnets.

Utilizing the molecular beam epitaxy technique, a nanoscale thin-film magnet of -axis-oriented SmCo and SmCo phases is stabilized. While typically in the prototype Sm(Co, Fe, Cu, Zr) pinning-type magnets, an ordered nanocomposite is formed by complex thermal treatments, here, a one-step approach to induce controlled phase separation in a binary Sm-Co system is shown. A detailed analysis of the extended X-ray absorption fine structure confirmed the coexistence of SmCo and SmCo phases with 65% SmCo and 35% SmCo.

All-Oxide Varactor Electromechanical Properties Extracted by Highly Accurate Modeling Over a Broad Frequency and Electric Bias Range.

Since the dielectric permittivity of ferroelectric materials depends on the electric field, they allow designing switchable and continuously tunable devices for adaptive microwave front ends. Part of the ongoing research is the field of all-oxide devices, where epitaxial oxide conductors are used instead of polycrystalline metal electrodes, leading to epitaxial ferroelectric layers and resulting in high device performance. In particular, they allow engineering the acoustic properties separated from the electric ones due to the structural similarity between the dielectric and conducting oxide films.

High Voltage Electrodes for Li-Ion Batteries and Efficient Water Electrolysis: An Oxymoron?

We demonstrate that key parameters for efficient electrocatalytic oxidation of water are the energetics of the redox complexes associated with their ionization and electrochemical potentials coupled to the change of metal-oxygen band hybridization. We investigate the catalytic activity of the LiCoPO-LiCoPO tailored compound, which is a 5 V cathode material for Li-ion batteries. The reason for the weak catalytic activity of the lithiated compound toward the oxygen evolution reaction is a large energy difference between the electronic states involved in the electrochemical reaction.

Synthesis and characterisation of fluorinated epitaxial films of BaFeOF: tailoring magnetic anisotropy a lowering of tetragonal distortion.

In this article, we report on the synthesis and characterisation of fluorinated epitaxial films of BaFeOF low-temperature fluorination of thin films of BaFeO grown by pulsed laser deposition. Diffraction measurements show that fluoride incorporation only results in a contraction of the film perpendicular to the film surface, where clamping by the substrate is prohibitive for strong in-plane changes. The fluorinated films were found to be homogenous regarding the fluorine content over the whole film thickness, and can be considered as single crystal equivalents to the bulk phase BaFeOF.

BaCoO: a new highly oxygen deficient perovskite-related phase with unusual Co coordination obtained by high temperature reaction with short reaction times.

A new highly oxygen deficient metastable modification of perovskite-related BaCoO2+δ (δ ∼ 0.01-0.02) has been prepared using high temperature reactions with short heating times.

In-operando photoelectron spectroscopy for batteries: Set-up using pristine thin film cathode and first results on NaCoO.

A model all-solid-state battery cell with a thin film NaCoO cathode was assembled under ultra-high vacuum conditions and cycled inside the vacuum chamber, using a dedicated sample holder. We present in-operando x-ray photoelectron spectroscopy measurements of a NaCoO cathode at different charging states. During battery operation, the change in sodium content, the change in cobalt oxidation state, and the evolution of the O1s and VB emissions could be monitored.

Geometric conductive filament confinement by nanotips for resistive switching of HfO2-RRAM devices with high performance.

Filament-type HfO2-based RRAM has been considered as one of the most promising candidates for future non-volatile memories. Further improvement of the stability, particularly at the "OFF" state, of such devices is mainly hindered by resistance variation induced by the uncontrolled oxygen vacancies distribution and filament growth in HfO2 films. We report highly stable endurance of TiN/Ti/HfO2/Si-tip RRAM devices using a CMOS compatible nanotip method.

Femtosecond laser ablation-based mass spectrometry: An ideal tool for stoichiometric analysis of thin films.

An accurate and routinely available method for stoichiometric analysis of thin films is a desideratum of modern materials science where a material's properties depend sensitively on elemental composition. We thoroughly investigated femtosecond laser ablation-inductively coupled plasma-mass spectrometry (fs-LA-ICP-MS) as an analytical technique for determination of the stoichiometry of thin films down to the nanometer scale. The use of femtosecond laser ablation allows for precise removal of material with high spatial and depth resolution that can be coupled to an ICP-MS to obtain elemental and isotopic information.

Oxygen vacancy induced room temperature ferromagnetism in Pr-doped CeO2 thin films on silicon.

Integration of functional oxides on Si substrates could open a pathway to integrate diverse devices on Si-based technology. Oxygen vacancies (Vo(··)) can strongly affect solid state properties of oxides, including the room temperature ferromagnetism (RTFM) in diluted magnetic oxides. Here, we report a systematical study on the RTFM of oxygen vacancy engineered (by Pr(3+) doping) CeO2 epitaxial thin films on Si substrates.

High-temperature stability and saturation magnetization of superparamagnetic nickel nanoparticles in microporous polysilazane-derived ceramics and their gas permeation properties.

Superparamagnetic Ni nanoparticles with diameters of about 3 nm are formed in situ at room temperature in a polysilazane matrix, forming Ni/polysilazane nanocomposite, in the reaction between a polysilazane and trans-bis(aceto-kO)bis(2-aminoethanol-k(2)N,O)nickel(II). The thermolysis of the Ni/polysilazane nanocomposite at 700 °C in an argon atmosphere results in a microporous superparamagnetic Ni/silicon oxycarbonitride (Ni/SiCNO) ceramic nanocomposite. The growth of Ni nanoparticles in Ni/SiCNO ceramic nanocomposite is totally suppressed even after thermolysis at 700 °C, as confirmed by HRTEM and SQUID characterizations.