Interfacial charge transfer and its impact on transport properties of LaNiO/LaFeO superlattices.

Charge transfer or redistribution at oxide heterointerfaces is a critical phenomenon, often leading to remarkable properties such as two-dimensional electron gas and interfacial ferromagnetism. Despite studies on LaNiO/LaFeO superlattices and heterostructures, the direction and magnitude of the charge transfer remain debated, with some suggesting no charge transfer due to the high stability of Fe (3d). Here, we synthesized a series of epitaxial LaNiO/LaFeO superlattices and demonstrated partial (up to ~0.

Guided anisotropic oxygen transport in vacancy ordered oxides.

Anisotropic and efficient transport of ions under external stimuli governs the operation and failure mechanisms of energy-conversion systems and microelectronics devices. However, fundamental understanding of ion hopping processes is impeded by the lack of atomically precise materials and probes that allow for the monitoring and control at the appropriate time- and length- scales. In this work, using in-situ transmission electron microscopy, we directly show that oxygen ion migration in vacancy ordered, semiconducting SrFeO epitaxial thin films can be guided to proceed through two distinctly different diffusion pathways, each resulting in different polymorphs of SrFeO with different ground electronic properties before reaching a fully oxidized, metallic SrFeO phase.

Multi-campaign ship and aircraft observations of marine cloud condensation nuclei and droplet concentrations.

In-situ marine cloud droplet number concentrations (CDNCs), cloud condensation nuclei (CCN), and CCN proxies, based on particle sizes and optical properties, are accumulated from seven field campaigns: ACTIVATE; NAAMES; CAMPEX; ORACLES; SOCRATES; MARCUS; and CAPRICORN2. Each campaign involves aircraft measurements, ship-based measurements, or both. Measurements collected over the North and Central Atlantic, Indo-Pacific, and Southern Oceans, represent a range of clean to polluted conditions in various climate regimes.

Evolution of traceable radon emanation sources from MBq to few Bq.

In the framework of the EMPIR project traceRadon, stable atmospheres with low-level radon activity concentrations have to be produced for calibrating radon detectors designed to measure outdoor air activity concentrations. The traceable calibration of these detectors at very low activity concentrations is of special interest to the radiation protection, climate observation, and atmospheric research communities. Radiation protection networks (such as the EUropean Radiological Data Exchange Platform (EURDEP)) and atmospheric monitoring networks (such as the Integrated Carbon Observation System (ICOS)) need reliable and accurate radon activity concentration measurements for a variety of reasons, including: the identification of Radon Priority Areas (RPA); improving the sensitivity and reliability of radiological emergency early warning systems (Melintescu et al.

Investigating the vertical and spatial extent of radon-based classification of the atmospheric mixing state and impacts on seasonal urban air quality.

A recently-developed radon-based method for combined classification of both diurnal and synoptic timescale changes in the atmospheric mixing state is applied to 1-year of observations in Ljubljana (capital of Slovenia). Five diurnal-timescale mixing classes (#1 to #5) were defined for each season along with an additional mixing class (#6) in non-summer months, representative of synoptic-timescale changes of the atmospheric mixing state associated with "persistent temperature inversion" (PTI) events. Seasonal composite radiosonde profiles and mean sea level pressure charts within each mixing class are used to demonstrate the link between prevailing synoptic conditions and the local mixing state, which drives changes in urban air quality.

Correlation between oxygen evolution reaction activity and surface compositional evolution in epitaxial LaSrNiFeO thin films.

Water electrolysis can use renewable electricity to produce green hydrogen, a portable fuel and sustainable chemical precursor. Improving electrolyzer efficiency hinges on the activity of the oxygen evolution reaction (OER) catalyst. Earth-abundant, ABO-type perovskite oxides offer great compositional, structural, and electronic tunability, with previous studies showing compositional substitution can increase the OER activity drastically.

Freestanding epitaxial SrTiO nanomembranes via remote epitaxy using hybrid molecular beam epitaxy.

The epitaxial growth of functional oxides using a substrate with a graphene layer is a highly desirable method for improving structural quality and obtaining freestanding epitaxial nanomembranes for scientific study, applications, and economical reuse of substrates. However, the aggressive oxidizing conditions typically used in growing epitaxial oxides can damage graphene. Here, we demonstrate the successful use of hybrid molecular beam epitaxy for SrTiO growth that does not require an independent oxygen source, thus avoiding graphene damage.

Atmospheric concentrations and sources of black carbon over tropical Australian waters.

Black carbon (BC) aerosols significantly contribute to radiative budgets globally, however their actual contributions remain poorly constrained in many under-sampled ocean regions. The tropical waters north of Australia are a part of the Indo-Pacific warm pool, regarded as a heat engine of global climate, and are in proximity to large terrestrial sources of BC aerosols such as fossil fuel emissions, and biomass burning emissions from northern Australia. Despite this, measurements of marine aerosols, especially BC remain elusive, leading to large uncertainties and discrepancies in current chemistry-climate models for this region.

Ultra-flat and long-lived plasmons in a strongly correlated oxide.

Plasmons in strongly correlated systems are attracting considerable attention due to their unconventional behavior caused by electronic correlation effects. Recently, flat plasmons with nearly dispersionless frequency-wave vector relations have drawn significant interest because of their intriguing physical origin and promising applications. However, these flat plasmons exist primarily in low-dimensional materials with limited wave vector magnitudes (q < ~0.

Spontaneous Lithiation of Binary Oxides during Epitaxial Growth on LiCoO.

Epitaxial growth is a powerful tool for synthesizing heterostructures and integrating multiple functionalities. However, interfacial mixing can readily occur and significantly modify the properties of layered structures, particularly for those containing energy storage materials with smaller cations. Here, we show a two-step sequence involving the growth of an epitaxial LiCoO cathode layer followed by the deposition of a binary transition metal oxide.

Spironolactone Ameliorates Cochlear Implant Induced Endolymphatic Hydrops.

Background: Endolymphatic hydrops (EH) has been observed in both animal and human cochleae following cochlear implant (CI) surgery. We tested whether EH could be eliminated by administration of mineralocorticoid steroid antagonist spironolactone and explored the electrophysiological consequences of this.

Methods: Sixty-four adult guinea pigs underwent cochlear implantation with a dummy electrode.

Epitaxial SrTiO films with dielectric constants exceeding 25,000.

SignificanceSemiconductor interfaces are among the most important in use in modern technology. The properties they exhibit can either enable or disable the characteristics of the materials they connect for functional performance. While much is known about important junctions involving conventional semiconductors such as Si and GaAs, there are several unsolved mysteries surrounding interfaces between oxide semiconductors.

Room-Temperature Ferromagnetism at an Oxide-Nitride Interface.

Heterointerfaces have led to the discovery of novel electronic and magnetic states because of their strongly entangled electronic degrees of freedom. Single-phase chromium compounds always exhibit antiferromagnetism following the prediction of the Goodenough-Kanamori rules. So far, exchange coupling between chromium ions via heteroanions has not been explored and the associated quantum states are unknown.

Understanding the Electronic Structure Evolution of Epitaxial LaNiFeO Thin Films for Water Oxidation.

Rare earth nickelates including LaNiO are promising catalysts for water electrolysis to produce oxygen gas. Recent studies report that Fe substitution for Ni can significantly enhance the oxygen evolution reaction (OER) activity of LaNiO. However, the role of Fe in increasing the activity remains ambiguous, with potential origins that are both structural and electronic in nature.

The Effect of Different Round Window Sealants on Cochlear Mechanics Over Time.

Background: This project investigated the effects of round window membrane (RWM) sealants after surgical incision, with a focus on audiological thresholds, ossicular mechanics, and the impact upon cochlear function and pathology.

Methods: Twenty-eight guinea pigs were randomly allocated to one of three sealant groups (muscle, n = 7; fascia, n = 7, Tisseel, n = 8) or an unsealed control group (n = 6). Preoperative hearing was measured using auditory brainstem responses (ABRs).

Incorporation of Ti in epitaxial FeTiOthin films.

The titanomagnetites (FeTiO,⩽ 1) are a family of reducible spinel-structure oxides of interest for their favorable magnetic, catalytic, and electrical transport properties. To understand the stability of the system during low temperature deposition, epitaxial thin films of FeTiOwere deposited by molecular beam epitaxy (MBE) on MgO(001) at 250-375 °C. The homogeneous incorporation of Ti, Fe valence state, and film morphology were all found to be strongly dependent on the oxidation conditions at the low substrate temperatures employed.

Spontaneous phase segregation of SrNiO and SrNiO during SrNiO heteroepitaxy.

Recent discovery of superconductivity in NdSrNiO motivates the synthesis of other nickelates for providing insights into the origin of high-temperature superconductivity. However, the synthesis of stoichiometric Sr NiO thin films over a range of has proven challenging. Moreover, little is known about the structures and properties of the end member SrNiO Here, we show that spontaneous phase segregation occurs while depositing SrNiO thin films on perovskite oxide substrates by molecular beam epitaxy.

Temperate mire fluctuations from carbon sink to carbon source following changes in water table.

The generally-accepted paradigm of wetland response to climate change is that water table drawdown and higher temperatures will cause wetlands to switch from a sink to a source of atmospheric carbon. However, it is hard to find a multi-year, ecosystem scale dataset representative of an undisturbed wetland that clearly demonstrates this paradigm on an annual total basis. Here we provide strong empirical confirmation of the above scenario based on six years of continuous eddy-covariance CO and CH flux measurements in Biebrza Valley, north-eastern Poland.

Identifying Ionic and Electronic Charge Transfer at Oxide Heterointerfaces.

The ability to tailor oxide heterointerfaces has led to novel properties in low-dimensional oxide systems. A fundamental understanding of these properties is based on the concept of electronic charge transfer. However, the electronic properties of oxide heterointerfaces crucially depend on their ionic constitution and defect structure: ionic charges contribute to charge transfer and screening at oxide interfaces, triggering a thermodynamic balance of ionic and electronic structures.

Hole-Trapping-Induced Stabilization of Ni in SrNiO /LaFeO Superlattices.

Creating new functionality in materials containing transition metals is predicated on the ability to control the associated charge states. For a given transition metal, there is an upper limit on valence that is not exceeded under normal conditions. Here, it is demonstrated that this limit of 3+ for Ni and Fe can be exceeded via synthesis of (SrNiO ) /(LaFeO ) superlattices by tuning n and m.

Extracting band edge profiles at semiconductor heterostructures from hard-x-ray core-level photoelectron spectra.

Internal electric fields that underpin functioning of multi-component materials systems and devices are coupled to structural and compositional inhomogeneities associated with interfaces in these systems. Hard-x-ray photoelectron spectroscopy is a valuable source of information on band-edge profiles, governed by the distribution of internal fields, deep inside semiconductor thin films and heterojunctions. However, extracting this information requires robust and physically meaningful decomposition of spectra into contributions from individual atomic planes.

Observation of Quantum Anomalous Hall Effect and Exchange Interaction in Topological Insulator/Antiferromagnet Heterostructure.

Integration of a quantum anomalous Hall insulator with a magnetically ordered material provides an additional degree of freedom through which the resulting exotic quantum states can be controlled. Here, an experimental observation is reported of the quantum anomalous Hall effect in a magnetically-doped topological insulator grown on the antiferromagnetic insulator Cr O . The exchange coupling between the two materials is investigated using field-cooling-dependent magnetometry and polarized neutron reflectometry.

Reversible Oxidation Quantified by Optical Properties in Epitaxial FeCrO Films on (001) MgAlO.

We report on the structural and optical properties of FeCrO epitaxial films grown by molecular beam epitaxy on MgAlO (001) as a function of δ (average cation valence). The average Fe valence is linked to the out-of-plane lattice parameter and the extent of light absorption in the infrared spectral region. Over-oxidized films (0 < δ < 0.

Tuning the Electronic Structure of LaNiO through Alloying with Strontium to Enhance Oxygen Evolution Activity.

The perovskite oxide LaNiO is a promising oxygen electrocatalyst for renewable energy storage and conversion technologies. Here, it is shown that strontium substitution for lanthanum in coherently strained, epitaxial LaNiO films (La Sr NiO) significantly enhances the oxygen evolution reaction (OER) activity, resulting in performance at = 0.5 comparable to the state-of-the-art catalyst BaSrCoFeO .