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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

Utilizing the molecular beam epitaxy technique, a nanoscale thin-film magnet of c-axis-oriented Sm2Co17 and SmCo5 phases is stabilized. While typically in the prototype Sm(Co, Fe, Cu, Zr)7.5-8 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 Sm2Co17 and SmCo5 phases with 65% Sm2Co17 and 35% SmCo5. The SmCo5 phase is stabilized directly on an Al2O3 substrate up to a thickness of 4 nm followed by a matrix of Sm2Co17 intermixed with SmCo5. This structural transition takes place through coherent atomic layers, as revealed by scanning transmission electron microscopy. Highly crystalline growth of well-aligned Sm2Co17 and SmCo5 phases with coherent interfaces result in strong exchange interaction, leading to enhanced magnetization and magnetic coupling. The arrangement of Sm2Co17 and SmCo5 phases at the nanoscale is reflected in the observed magnetocrystalline anisotropy and coercivity. As next-generation permanent magnets require designing of materials at an atomic level, this work enhances our understanding of self-assembling and functioning of nanophased magnets and contributes to establishing new concepts to engineer the microstructure for beyond state-of-the-art magnets.

Reversible antiferroelectric-ferroelectric phase transitions were recently observed in a series of SrSnO3-modified NaNbO3 lead-free antiferroelectric materials, exhibiting well-defined double polarization hysteresis loops at ambient conditions. Here, transmission electron microscopy was employed to investigate the crystallographyand domain configuration of this newly designed system via electron diffraction and centered dark-field imaging. It was confirmed that antiferroelectricity is maintained in all compositions, manifested by the characteristic ¼ superlattice reflections in the electron-diffraction patterns. By investigating the antiferroelectric domains and domain boundaries in NaNbO3, we demonstrate that antiphase boundaries are present and their irregular periodicity is responsible for the streaking features along the ¼ superlattice reflections in the electron-diffraction patterns. The signature domain blocks observed in pure NaNbO3 are maintained in the SrSnO3-modified ceramics, but disappear when the amount of SrSnO3 reaches 7 mol.%. In particular, a well-defined and distinct domain configuration is observed in the NaNbO3 sample modified with 5 mol.% SrSnO3, which presents a parallelogram domain morphology.

Electric-field-induced phase transitions are the most important characteristics of antiferroelectric materials. However, in several prototype antiferroelectrics, these transitions are irreversible and the origin of this behavior is poorly understood. This prevents their widespread use, for example, in energy storage and memory applications. Here, we investigated the antiferroelectric-ferroelectric phase transitions in polycrystalline NaNbO3, a material recently suggested as the basis for lead-free antiferroelectrics with high energy storage densities. An irreversible transition from the antiferroelectric state to a new state showing macroscopic piezoelectricity (d33=35 pC/N) was induced at 11.6 kV/mm (room temperature, 1 Hz), accompanied by a 33% drop in permittivity. Microscopically, a change from a translational antiferroelectric domain structure to a wedge-shaped ferroelectric domain structure was observed using transmission electron microscopy. 23Na solid-state nuclear magnetic resonance allowed for a detailed study of the local structure and revealed pure antiferroelectric and coexisting antiferroelectric/ferroelectric nature of the samples before and after the application of an electric field, respectively. Interestingly, despite the large electric fields applied, only 50±5% of the material underwent the antiferroelectric-ferroelectric phase transition, which was related to the material´s microstructure. The temperature- and frequency-dependence of the phase transition was studied and compared to the behavior observed in lead-based antiferroelectric systems.

Ferromagnetic Fe3Sn, Fe5Sn3 and Fe3Sn2 single crystals were synthesized using the reactive flux technique. Derived from single crystal x-ray diffraction and Transmission Electron Microscopy (TEM), a new structural model is proposed for the Fe5Sn3 crystals - the threefold twinning of an orthorhombic unit cell with (3 + 1) dimensional space group Pbcm(α00)0s0. The spontaneous magnetization (Ms) and the anisotropy constants K1 and K2 of Fe3Sn, Fe5Sn3 and Fe3Sn2 single crystals were determined in a wide temperature range using M(H) dependencies and a modified Sucksmith-Thompson technique. Ms and K1 were also evaluated in the framework of Density Functional Theory (DFT) and an overall good agreement was observed between the calculated and experimental results. Furthermore, a critical evaluation of different analytical models for the assessment of magnetocrystalline anisotropy was performed, which are restricted to the analysis of uniaxial magnetic domain patterns, and it is shown that such high-throughput techniques can lead to unrealistic results. Finally, a DFT high-throughput screening of the Fe-Sn phase diagram was used to identify Fe-Sn based phases with potential to be stabilized upon alloying, and their magnetization and magnetocrystalline anisotropy were evaluated. The results show that a similar strong anisotropy as observed in Fe3Sn may also be found in other Fe-Sn based phases, having higher potential to be used as hard magnetic material.

The potential of thermoelectric thin films lies in wide range of applications from micro-energy harvesting to the sensors. For this, it is essential to have high power factor and ultra-low thermal conductivity which have been reported in thin films produced by expensive vacuum techniques. However, for practical applications, it is essential to use inexpensive technique to grow thin film in large area. In this direction, we report the use of mist-chemical vapor deposition (CVD) technique to develop oxide thin films for thermoelectric application. We grow c-axis oriented nano-porous thin films of 2% Al-doped ZnO (AZO). These nano-porous films have enhance phonon scattering which results in the depression of thermal conductivity (κ) while maintaining similar order of magnitude of power factor as reported in dense films prepared by vacuum techniques. For example, κ300K decreases from 6.5 W/m.K for dense thin film (porosity = 7.9%) grown by pulsed laser deposition to 5.54 W/m.K for porous film (porosity = 24.2%) grown by mist-CVD while maintaining the power factor of similar order of magnitude for AZO film deposited on SrTiO3. The depression of thermal conductivity in porous films may lead to higher figure of merit which is promising for practical applications of thermoelectric oxide films.

Ni-Mn-based metamagnetic shape-memory alloys exhibit a giant thermal response to magnetic fields and uniaxial stress which can be utilized in single caloric or multicaloric cooling concepts for energy-efficient and sustainable refrigeration. However, during cyclic operation these alloys suffer from structural and functional fatigue as a result of their high intrinsic brittleness. Here, we present based on Fe-doping of Ni-Mn-In a microstructure design strategy which simultaneously improves cyclic stability and maintains the excellent magnetocaloric and elastocaloric properties. Our results reveal that precipitation of a strongly Fe-enriched and In-depleted coherent secondary gamma-phase at grain boundaries can ensure excellent mechanical stability by hindering intergranular fracture during cyclic loading. In this way, a large elastocaloric effect of -4.5 K was achieved for more than 16000 cycles without structural or functional degradation, which corresponds to an increase of the cyclic stability by more than three orders of magnitude as compared to single-phase Ni-Mn-In-(Fe). In addition, we demonstrate that the large magnetocaloric effect of single-phase Ni-Mn-In-(Fe) can be preserved in the dual-phase material when the secondary gamma-phase is exclusively formed at grain boundaries as the martensitic transformation within the Heusler matrix is barely affected. This way, an adiabatic temperature change of -3 K and an isothermal entropy change of 15 $Jkg^{-1}K^{-1}$ was obtained in 2 T for dual-phase Ni-Mn-In-Fe. We expect that this concept can be applied to other single caloric and mutlicaloric materials, therewith paving the way for solid-state caloric cooling applications.

Low-frequency noise in Y2O3-based resistive random-access memory devices with analog switching is studied at intermediate resistive states and as a function of dc cycling. A universal 1/f(alpha)-type behavior is found, with a frequency exponent of alpha approximate to 1.2 that is independent of the applied reset voltage or the device resistance and is attributed to the intrinsic abundance of oxygen vacancies unique to the structure of yttria. Remarkably, the noise magnitude in the high resistive state systematically decreases through dc training. This effect is attributed to the stabilization of the conductive filament via the consumption of oxygen vacancies, thus reducing the number of active fluctuators in the vicinity of the filament.

In this study, molecular beam epitaxy is utilized to stabilize a nanostructured thin-film magnet consisting of a soft magnetic Y2Co17 exchange coupled to hard magnetic YCo5. While, typically, a phase decomposition can be obtained in rare-earth cobalt systems only by the addition of further elements like Cu, Fe, and Zr and complex heat treatments, here we directly induce phase separation by growth kinetics. The resulting nanoscale architecture, as revealed by cross-sectional transmission electron microscopy, is composed of a network of coherently interlinked and aligned Y2Co17 and YCo5 building blocks. The formation of coherent precipitations is facilitated by the perfectly matching lattice constants, atomic species, and crystal symmetry of the two phases with vastly different magnetocrystalline anisotropies. The hard magnetic phase induces an aligned uniaxial anisotropy in Y2Co17, resulting in substantial coercivity associated with enhanced energy products. This work highlights the importance of thin-film epitaxy in understanding magnetic hardening mechanisms and suggests strategies for a rational design of future sustainable magnetic systems.

Any dielectric material under a strain gradient presents flexoelectricity. Here, we synthesized 0.75 sodium bismuth titanate −0.25 strontium titanate (NBT-25ST) core–shell nanoparticles via a solid-state chemical reaction directly inside a transmission electron microscope (TEM) and observed domain-like nanoregions (DLNRs) up to an extreme temperature of 800 °C. We attribute this abnormal phenomenon to a chemically induced lattice strain gradient present in the core–shell nanoparticle. The strain gradient was generated by controlling the diffusion of strontium cations. By combining electrical biasing and temperature-dependent in situ TEM with phase field simulations, we analyzed the resulting strain gradient and local polarization distribution within a single nanoparticle. The analysis confirms that a local symmetry breaking, occurring due to a strain gradient (i.e. flexoelectricity), accounts for switchable polarization beyond the conventional temperature range of existing polar materials. We demonstrate that polar nanomaterials can be obtained through flexoelectricity at extreme temperature by tuning the cation diffusion., The limited number of materials with a switchable electrical polarization available for applications can be increased by exploiting the flexoelectric effect. Here, switchable polarization in nanoparticles induced by an elemental distribution dependent strain gradient up to 800 °C is demonstrated.

A plethora of magnetic ground states along with intriguing magnetic properties have been reported in thin films of Mn-containing MAX phases. However, fewer results and therefore less knowledge in the area of bulk magnetic MAX phases exist resulting in many open research questions that still remain unanswered. Synthesis of high quality materials is key and is here achieved for bulk V2AlC and its Mn-doped analogs by means of microwave heating and spark plasma sintering. The obtained materials are carefully characterized by structural and microstructural investigations resulting in an average Mn-content of 2% corresponding to the mean chemical composition of (V0.96±0.02Mn0.04±0.02)2AlC in the Mn-doped V2AlC samples. While the parent MAX phase as well as the sample with the nominally lowest Mn-content are obtained essentially single-phase, samples with higher Mn-levels exhibit Mn-rich side phases. These are most likely responsible for the ferromagnetic behavior of the corresponding bulk materials. Besides, we show Pauli paramagnetism of the parent compound V2AlC and a combination of Pauli and Langevin paramagnetism in (V0.96±0.02Mn0.04±0.02)2AlC. For the latter, a magnetic moment of μM = 0.2(2) μB per M atom can be extracted.

Point defects largely determine the properties of functional oxides. So far, limited knowledge exists on the impact of cation vacancies on electroceramics, especially in (Na1/2Bi1/2)TiO3 (NBT)-based materials. Here, we report on the drastic effect of A-site non-stoichiometry on the cation diffusion and functional properties in the representative ferroelectric (Na1/2Bi1/2)TiO3–SrTiO3 (NBT–ST). Experiments on NBT/ST bilayers and NBT–ST with Bi non-stoichiometry reveal that Sr2+-diffusion is enhanced by up to six orders of magnitude along the grain boundaries in Bi-deficient material as compared to Bi-excess material with values of grain boundary diffusion ∼10−8 cm2 s−1 and ∼10−13 cm2 s−1 in the bulk. This also means a nine orders of magnitude higher diffusion coefficient compared to reports from other Sr-diffusion coefficients in ceramics. Bi-excess leads to the formation of a material with a core–shell microstructure. This results in 38% higher strain and one order of magnitude lower remanent polarization. In contrast, Bi-deficiency leads to a ceramic with a grain size six times larger than in the Bi-excess material and homogeneous distribution of compounds. Thus, the work sheds light on the rich opportunities that A-site stoichiometry offers to tailor NBT-based materials microstructure, transport properties, and electromechanical properties.

Recent advances in microelectromechanical systems (MEMS) based chips for in situ transmission electron microscopy are opening exciting new avenues in nanoscale research. The capability to perform current-voltage measurements while simultaneously analyzing the corresponding structural, chemical or even electronic structure changes during device operation would be a major breakthrough in the field of nanoelectronics. In this work we demonstrate for the first time how to electrically contact and operate a lamella cut from a resistive random access memory (RRAM) device based on a Pt/HfO2/TiN metal-insulator-metal (MIM) structure. The device was fabricated using a focused ion beam (FIB) instrument and an in situ lift-out system. The electrical switching characteristics of the electron-transparent lamella were comparable to a conventional reference device. The lamella structure was initially found to be in a low resistance state and could be reset progressively to higher resistance states by increasing the positive bias applied to the Pt anode. This could be followed up with unipolar set/reset operations where the current compliance during set was limited to 400 µA. FIB structures allowing to operate and at the same time characterize electronic devices will be an important tool to improve RRAM device performance based on a microstructural understanding of the switching mechanism.

A higher saturation magnetization obtained by an increased iron content is essential for yielding larger energy products in rare-earth Sm2Co17-type pinning-controlled permanent magnets. These are of importance for high-temperature industrial applications due to their intrinsic corrosion resistance and temperature stability. Here we present model magnets with an increased iron content based on a unique nanostructure and -chemical modification route using Fe, Cu, and Zr as dopants. The iron content controls the formation of a diamond-shaped cellular structure that dominates the density and strength of the domain wall pinning sites and thus the coercivity. Using ultra-high-resolution experimental and theoretical methods, we revealed the atomic structure of the single phases present and established a direct correlation to the macroscopic magnetic properties. With further development, this knowledge can be applied to produce samarium cobalt permanent magnets with improved magnetic performance., Understanding the factors that determine the properties of permanent magnets, which play a central role in many industrial applications, can help in improving their performance. Here, the authors study how changes in the iron content affect the microstructure of samarium cobalt magnets.

In this study lead-free 2-2 and 0-3 ceramic/ceramic composites comprised of the non-ergodic relaxor 0.93(Bi1/2Na1/2)TiO3–0.07BaTiO3 and ergodic relaxor 0.94Bi0.5(Na0.75K0.25)0.5TiO3–0.06BiAlO3 were investigated. The macroscopic electromechanical behavior was characterized as a function of continuent content,revealing an enhancement in the unipolar strain from the multilayer composite structure. Systematic evaluation of the effects of co-sintering on microstructural properties, such as grain size and porosity, revealed potential mechanisms by which the increase in unipolar strain was achieved. In addition, interdiffusion between the constituents was observed, providing evidence for the formation of a functionally graded ceramic by co-sintering. These data are contrasted with highresolution energy dispersive X-ray microanalysis for measurement of chemical composition across the interface of 2-2 ceramics. These findings provide insight into how synthesis routes can be optimized for tailoring the enhancement of electromechanical properties of lead-free electroceramic composite systems.

In this work, analysis and simulation of all experimentally observed switching modes in hafnium oxide based resistive random access memories are carried out using a simplified electrical conduction model. To achieve switching mode variation, two metal-insulator-metal cells with identical stack combination, but varying oxygen stoichiometry of the hafnia layer, namely, stoichiometric vs highly deficient, are considered. To access the individual switching modes, the devices were subjected to a variety of cycling conditions comprising different voltage and current ranges. For modeling the device behavior, a single or two antiserially connected memdiodes (diode with memory) were utilized. In this way, successful compact simulation of unipolar, bipolar, threshold, and complementary resistive switching modes is accomplished confirming the coexistence of two switching mechanisms of opposite polarity as the basis for all observable switching phenomena in this material. We show that only calibration of the outer current-voltage loops with the memdiode model is necessary for predicting the device behavior in the defined region revealing additional information on the switching process. The correspondence of each memdiode device with the conduction characteristics of the individual top and bottom metal-oxide contacts allows one to assess the role played by each interface in the switching process separately. This identification paves the path for a future improvement of the device performance and functionality by means of appropriate interface engineering.

The aim of this work is to investigate the effect of very fine grain sizes on the spinodal decomposition in the Alnico system. Commercial Alnico 5 was melted and melt-spun with varying copper wheel speeds, which led to a grain size of 1–2 µm. This value was further reduced to sub-micrometer size by a small addition of Boron (1 at%). The spinodal decomposition was induced through a two-step annealing treatment under magnetic field in the range of 600–900 °C. It was found that the size of the spinodal structures is not influenced much by increased wheel speeds but becomes smaller with the addition of Boron. However, the difference in coercivity between the samples with and without Boron is only 50 Oe (4 kA/m). To study the influence of the annealing treatment two sets of samples are compared, one with the highest coercivity (366 Oe/29 kA/m) and the other one with lower coercivity (180 Oe/14.5 kA/m). We found with Scanning transmission electron microscopy Energy-dispersive X-ray spectroscopy (STEM EDX) a much sharper chemical interface between the α1 and α2 precipitates in the former sample, which we attribute to be the main reason for the higher coercivity.

The Bi1/2Na1/2TiO3-based materials exhibit the largest electric-field-induced strains among lead-free piezoceramics and are considered as promising candidates for actuation applications. A typical representative of this group is (1-x)Bi1/2Na1/2TiO3-xSrTiO3, where its excellent electromechanical properties were recently related to the existence of a core–shell microstructure. Although the latter was also reported in other Bi1/2Na1/2TiO3-based ceramics, the formation mechanism remains unknown. In the present work we therefore first investigated the solid-state reaction occurring during calcination using simultaneous thermogravimetric analysis, X-ray diffraction, scanning and transmission electron microscopy. The reaction occurred in two steps, whereby the cores and shells had different formation reaction temperatures, which resulted in a metastable heterogeneous microstructure. Furthermore, a series of sintered samples with different relative densities, grain sizes, and core densities was prepared. Modifications of these microstructural parameters resulted in variation of the maximal strain by 17% and in the electric-field required to trigger the phase transitions by 38%.

This work investigates the transition from digital to gradual or analog resistive switching in yttrium oxide-based resistive random-access memory devices. It is shown that this transition is determined by the amount of oxygen in the functional layer. A homogeneous reduction of the oxygen content not only reduces the electroforming voltage, allowing for forming-free devices, but also decreases the voltage operation window of switching, thereby reducing intra-device variability. The most important effect as the dielectric becomes substoichiometric by oxygen engineering is that more intermediate (quantized) conduction states are accessible. A key factor for this reproducibly controllable behavior is the reduced local heat dissipation in the filament region due to the increased thermal conductivity of the oxygen depleted layer. The improved accessibility of quantized resistance states results in a semi-gradual switching both for the set and reset processes, as strongly desired for multi-bit storage and for an accurate definition of the synaptic weights in neuromorphic systems. A theoretical model based on the physics of mesoscopic structures describing current transport through a nano-constriction including asymmetric potential drops at the electrodes and non-linear conductance quantization is provided. The results contribute to a deeper understanding on how to tailor materials properties for novel memristive functionalities.

International audience; (K,Na)NbO 3 -based ferroelectric single crystals have recently undergone a substantial development, resulting in improved crystal quality and large piezoelectric coefficients, exceeding 700 pC/N, over a broad temperature range. However, further development necessitates a detailed understanding of the mechanisms defining the domain structure and its temperature evolution. This paper presents the investigation into the crystallographic structure and domain configurations of a (K,Na,Li)(Ta,Nb)O 3 single crystal over a broad temperature range. The crystal was grown by the submerged-seed solution growth technique and investigated using in situ transmission electron microscopy, X-ray diffraction, dielectric measurements, and polarized light microscopy. The lattice distortion, structural phase transitions, and domain configurations are reported. A transition from the lamellar orthorhombic to the rectangular tetragonal domain structure is observed upon heating. Moreover, the milky optical appearance of the crystal was investigated and found to result from the presence of regions with different domain configurations and domain sizes. The formation of these regions is related to the growth defects, which govern the domain formation when cooling below the Curie temperature.

We present the development of a MEMS-based sample carrier to be used for in-situ studies inside the Transmission Electron Microscope (TEM). This MEMS device, referred to as the Nano-Chip, acts as a multifunctional sample carrier and micro-sized laboratory for simultaneous heating and biasing experiments. Each Nano-Chip consists of eight contacts, which enable four-point-probe measurements for both heating and biasing purposes. The microheater enables temperatures up to 800°C. Similarly, the system allows to apply up to 100V, which can result in electric fields as high as 200kV/cm. Samples are placed directly onto the electron transparent windows which allow for the electron beam to pass through for in-situ imaging. This system represents a cost-effective add-on to the TEM, which acts as the ideal tool for failure analysis of semiconductor materials, characterization of batteries, fuel cells and studies of structure responses to electric fields.

Typical synthesis of α″-Fe16N2 nanoparticles involves reduction of iron oxides by hydrogen at elevated temperatures which is disadvantageous due to the particle coalescence. Here we report on a process for reduction of iron oxides at elevated pressures and show that by increasing hydrogen pressure from atmospheric to 53 MPa, it is possible to reduce the reaction temperature from 663 K down to 483 K, resulting in phase-pure α-Fe nanoparticles without noticeable particle growth. By subsequent nitrogenation in an ammonia flow, fine, 99% phase-pure α″-Fe16N2 nanoparticles could be synthesized. The reduction temperature and the respective particle size has a significant influence on the nitrogenation step. α″-Fe16N2 nanoparticles exhibit semi-hard magnetic properties with Ms(0) = 215 Am2 kg−1, μ0Hc = 0.22 T, TC = 634 K and exchange stiffness Ac = 6.84 pJ m−1, Aa,b = 7.53 pJ m−1. Synthesis conditions, microstructure, chemical composition and thermal stability of the nanoparticles are systematically studied and correlated with the observed magnetic properties.

In the field of oxide electronics, there has been tremendous progress in the recent years in atomic engineering of functional oxide thin films with controlled interfaces at the unit cell level. However, some relevant devices such as tunable ferroelectric microwave capacitors (varactors) based on BaxSr1−xTiO3 are stymied by the absence of suited compatible, very low resistive oxide electrode materials on the micrometer scale. Therefore, we start with the epitaxial growth of the exceptionally highly conducting isostructural perovskite SrMoO3 having a higher room-temperature conductivity than Pt. In high-frequency applications such as tunable filters and antennas, the desired electrode thickness is determined by the electromagnetic skin depth, which is of the order of several micrometers in the frequency range of a few gigahertz. Here, we report the pulsed laser deposition of a fully layer-by-layer grown epitaxial device stack, combining a several micrometers thick electrode of SrMoO3 with atomically engineered sharp interfaces to the substrate and to the subsequently grown functional dielectric layer. The difficult to achieve epitaxial thick film growth makes use of the extraordinary ability of perovskites to accommodate strain well beyond the critical thickness limit by adjusting their lattice constant with small shifts in the cation ratio, tuned by deposition parameters. We show that our approach, encompassing several orders of magnitude in film thickness scale whilst maintaining atomic layer control, enables the fabrication of metal-insulator-metal (MIM) varactors based on 50–100 nm thin BaxSr1−xTiO3 layers with high tunability above three at the Li-ion battery voltage level (3.7 V).

Hafnium oxide (HfOx)-based memristive devices have tremendous potential as nonvolatile resistive random access memory (RRAM) and in neuromorphic electronics. Despite its seemingly simple two-terminal structure, a myriad of RRAM devices reported in the rapidly growing literature exhibit rather complex resistive switching behaviors. Using Pt/HfOx/TiN-based metal–insulator–metal structures as model systems, it is shown that a well-controlled oxygen stoichiometry governs the filament formation and the occurrence of multiple switching modes. The oxygen vacancy concentration is found to be the key factor in manipulating the balance between electric field and Joule heating during formation, rupture (reset), and reformation (set) of the conductive filaments in the dielectric. In addition, the engineering of oxygen vacancies stabilizes atomic size filament constrictions exhibiting integer and half-integer conductance quantization at room temperature during set and reset. Identifying the materials conditions of different switching modes and conductance quantization contributes to a unified switching model correlating structural and functional properties of RRAM materials. The possibility to engineer the oxygen stoichiometry in HfOx will allow creating quantum point contacts with multiple conductance quanta as a first step toward multilevel memristive quantum devices.

The functionality of YBa2Cu3O7 (YBCO)-coated conductor technology depends on the reliability and microstructural properties of a given tape or wire architecture. Particularly, the interface to the metal tape is of interest since it determines the adhesion, mechanical stability of the film and thermal contact of the film to the substrate. A trifluoroacetate (TFA)—metal organic deposition (MOD) prepared YBCO film deposited on a chemical solution-derived buffer layer architecture based on CeO2=La2Zr2O7 and grown on a flexible Ni5 at.%W substrate with af100gh001i biaxial texture was investigated. The YBCO film had a thickness was 440 nm and a jc of 1:02 MA cm 2 was determined at 77 K and zero external field. We present a sub-nanoscale analysis of a fully processed solution-derived YBCO-coated conductor by aberration-corrected scanning transmission electron microscopy (STEM) combined with electron energy-loss spectroscopy (EELS). For the first time, structural and chemical analysis of the valence has been carried out on the sub-nm scale. Intermixing of Ni, La, Ce, O and Ba takes place at these interfaces and gives rise to nanometer-sized interlayers which are a by-product of the sequential annealing process. Two distinct interfacial regions were analyzed in detail: (i) the YBCO=CeO2=La2Zr2O7 region (10 nm interlayer) and (ii) the La2Zr2O7=Ni‐5 at.%W substrate interface region (20 nm NiO). This is of particular significance for the functionality of these YBCO-coated conductor architectures grown by chemical solution deposition. (Some figures may appear in colour only in the online journal)