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Controlling the oxide ion (O2−) concentration in oxides is essential to develop advanced ionic devices, i.e. solid oxide fuel cells, smart windows, memory devices, energy storage devices, and so on. Among many oxides several transition metal (TM)-based perovskite oxides show high oxide ion conductivity, and their physical properties show high sensitivity to the change of the oxide ion concentration. Here, the change in the oxide ion concentration is shown through the overlayer deposition on the SrFe0.5Co0.5O2.5 (SFCO) oxygen sponge film. We grew SFCO films followed by the deposition of two kinds of complex oxide films under exactly the same growth conditions, and observed the changes in the crystal structure, valence states, and magnetic ground states. As the NSMO overlayer grows, strong evidence of oxidation at the O K edge is shown. In addition, the Fe4+ feature is revealed, and the electron valence state of Co increased from 3 to 3.25. The oxide ion concentration of SFCO changes during layer growth due to oxidation or reduction due to differences in chemical potential. The present results might be useful to develop advanced ionic devices using TM-based perovskite oxides.

The use of medical 3D printing has expanded dramatically for breast diseases. A writing group composed of the Radiological Society of North America (RSNA) Special Interest Group on 3D Printing (SIG) provides updated appropriateness criteria for breast 3D printing in various clinical scenarios. Evidence-based appropriateness criteria are provided for the following clinical scenarios: benign breast lesions and high-risk breast lesions, breast cancer, breast reconstruction, and breast radiation (treatment planning and radiation delivery).

Nitridated iron is a promising material for potential applications in permanent magnets. Recent work on stabilization of nitridated iron in a foil form through nitrogen ion implantation and annealing motivates to study effect of thermal annealing on the surface of nitrogen-implanted iron. In this work, we show effect of annealing on chemical state and magnetism of nitrogen implanted epitaxial iron films. It is observed that nitrogen in the lattices only stays at the lower temperatures than 450 °C. In addition, significant reduction and lattice modification are taken placed, when the film is annealed at 450 °C. The increases of saturation magnetization and coercivity, where it is annealed at 450 °C, are likely to be triggered by reduction of oxygen contents at the surface and thinning of Fe2O3.

Strontium cobalt oxide (SrCoO2.5) has recently attracted increasing attention as its optoelectronic and magnetic properties can be widely controlled using electrochemical oxidation/protonation at r...

Understanding cellular contributions to hemodynamic activity is essential for interpreting blood-based brain mapping signals. Optogenetic studies examining cell-specific influences on local hemodynamics have reported that excitatory activity results in cerebral perfusion and blood volume increase, while inhibitory activity contributes to both vasodilation and vasoconstriction. How specific subpopulations of interneurons regulate the brain’s blood supply is less examined. Parvalbumin interneurons are the largest subpopulation of GABAergic neurons in the brain, critical for brain development, plasticity, and long-distance excitatory neurotransmission. Despite their essential role in brain function, the contribution of parvalbumin neurons to neurovascular coupling has been relatively unexamined. Using optical intrinsic signal imaging and laser speckle contrast imaging, we photostimulated awake and anesthetized transgenic mice expressing channelrhodopsin under a parvalbumin promoter. Increased parvalbumin activity reduced local oxygenation, cerebral blood volume, and cerebral blood flow. These “negative” hemodynamic responses were consistent within and across mice and reproducible across a broad range of photostimulus parameters. However, the sign and magnitude of the hemodynamic response resulting from increased parvalbumin activity depended on the type and level of anesthesia used. Opposed hemodynamic responses following increased excitation or parvalbumin-based inhibition suggest unique contributions from different cell populations to neurovascular coupling.

Nitrogen ion implantation is a useful technique to put nitrogen ions into lattices. In this work, nitrogen ion implantation into epitaxial Mo films is performed to create a buried superconducting γ-Mo2N. Atomically flat epitaxial (110) Mo films are grown on (0001) Al2O3. By impinging nitrogen ions, where the beam energy is fixed to 20 keV, we observe (111) γ-Mo2N diffraction and the formation of a γ-Mo2N layer from X-ray reflectivity. Magnetization and transport measurements clearly support a superconducting layer in the implanted film. Our strategy shows that formation of a buried superconducting layer can be achieved through ion implantation and self-annealing.

Reduction of MoO3 in extreme reducing condition is a way to achieve Mo metal. However, effect of less extreme reductive-annealing, where it allows to keep the crystal structure, on physical and chemical properties of MoO3 has not been well-studied. In this work, we studied the evolution of Mo valence state during reductive annealing and its effect on high temperature transport. We found the formation of oxygen vacancies on surface of MoO3 single crystals at the low temperature, which is evidenced by increase of Mo5+ and color change. In addition, formation of Mo4+ was at the elevated temperature. For understanding the relation between bulk conductivity and Mo valence state, real-time impedance spectroscopy is employed. Use of two different gases makes it possible to distinguish impedance responses of MoO3 from those of reduced MoO3-x. Also, from time-dependent impedance measurements, we observed the evolution of transport behaviour by evolution of Mo valence state.

Controlling the oxide ion (O

We demonstrate the effect of the crystallinity of ceramic targets on the electronic properties of LaNiO3 (001) thin films epitaxially grown by pulsed laser deposition (PLD). We prepared two kinds of LaNiO3 targets with different crystallinity by manipulating calcination temperature (i.e., 300 and 1000 °C) in the solid state reaction for ceramic synthesis. X-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM), and X-ray photoelectron spectroscopy (XPS) experiments of the as-sintered LaNiO3 ceramic targets clearly show that the LaNiO3 target sintered after high-temperature (1000 °C, high crystallinity) calcination is more oxidized to Ni3+ with better crystallinity than the LaNiO3 target sintered after low-temperature (300 °C, poor crystallinity) calcination. Using these two LaNiO3 ceramics as PLD targets, we fabricated epitaxial LaNiO3/LaAlO3 (001) thin-film heterostructures to examine how target crystallinity affects the physical properties of LaNiO3 films. Intriguingly, the electri...

Nitrogen ion implantation is a useful technique to put nitrogen ions into lattices. In this work, nitrogen ion implantation into epitaxial Mo films is performed to create a buried superconducting γ-Mo

Supplemental material, sj-pdf-1-jcb-10.1177_0271678X20930831 for Opposed hemodynamic responses following increased excitation and parvalbumin-based inhibition by Joonhyuk Lee, Chloe L Stile, Annie R Bice, Zachary P Rosenthal, Ping Yan, Abraham Z Snyder, Jin-Moo Lee and Adam Q Bauer in Journal of Cerebral Blood Flow & Metabolism

We will review our lab’s work using optogenetics and wide field optical imaging for examining excitatory and inhibitory contributions to neurovascular coupling, and how these cell populations are connected across the cortex.

Due to success of desired doping, ion implantation has been widely used for semiconductor processing. In this work, we used nitrogen ion implantation to enhance magnetism in CeFe12 epitaxial thin films. To optimize nitrogen contents in CeFe12 and minimize the damage caused by the high-energy ion beam, we varied the thickness of the capping Mo layer. The saturation magnetization increased nearly 25% by nitrogen ion implantation into CeFe12 thin film. This phenomenon is explained by density functional theory calculations and confirmed by the magnetic resonance technique. The ion implantation and design strategy can be used for light-ion implantation into lattices to modulate magnetic, optical, and electrical properties.

In transition metal oxides (TMOs), lots of physical phenomena such as metal–insulator transitions (MIT), magnetism, and ferroelectricity are closely related to the amounts of oxygen contents. Thus, understanding surface oxidation process in TMOs and its effect are important for enhancing performances of modern electronic and electrochemical devices due to miniaturization of those devices. In this regard, MoO2+x (0 ≤ x ≤ 1) is an interesting TMO, which shows MIT driven by the change of its oxygen content, i.e. metallic MoO2 and insulating MoO3. Hence, understanding thermally driven oxygen intercalation into MoO2 is very important. In this work, we conducted in situ postannealing of as-grown epitaxial MoO2 thin films at different temperatures in oxidative condition to investigate the thermal effect on oxygen ion intercalation and resultant MIT in MoO2+x. Through the spectroscopic techniques such as spectroscopic ellipsometry and X-ray absorption spectroscopy, we observed that oxygen ions can intercalate int...

Optogenetic photostimulation of excitatory or inhibitory circuits differentially regulated local cerebral blood volume and flow in awake, transgenic mice. Each neural subclass also uniquely influenced distant cortical hemodynamic activity.

Tuning the properties of transition-metal oxides by controlling oxygen content has value in many applications. $T\phantom{\rule{0}{0ex}}o\phantom{\rule{0}{0ex}}p\phantom{\rule{0}{0ex}}o\phantom{\rule{0}{0ex}}t\phantom{\rule{0}{0ex}}a\phantom{\rule{0}{0ex}}c\phantom{\rule{0}{0ex}}t\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}c$ oxides, which can vary their crystal structure as oxygen content changes, are promising materials for reversible manipulation, since they do not create defects in random fashion. Real-time x-ray scattering is used to monitor the topotactic phase transition and its reversibility in SrFe${}_{0.8}$Co${}_{0.2}$O${}_{3\ensuremath{-}x}$. Reversible, redox-driven topotactic transformations at low temperature and atmospheric pressure indicate that these materials may be of use in electrochemical devices, such as solid oxide fuel cells.

Transparent oxide semiconductors (TOSs) showing both high visible transparency and high electron mobility have attracted great attention towards the realization of advanced optoelectronic devices. La-doped BaSnO3 (LBSO) is one of the most promising TOSs because its single crystal exhibits a high electron mobility. However, in the LBSO films, it is very hard to obtain high mobility due to the threading dislocations, which are originated from the lattice mismatch between the film and the substrate. Therefore, many researchers have tried to improve the mobility by inserting a buffer layer. While the buffer layers increased the electron mobilities, this approach leaves much to be desired since it involves a two-step film fabrication process and the enhanced mobility values are still significantly lower than single crystal values. We show herein that the electron mobility of LBSO films can be improved without inserting any buffer layers if the films are grown under highly oxidative ozone (O3) atmospheres. The O3 environments relaxed the LBSO lattice and reduced the formation of Sn2+ states, which are known to suppress the electron mobility in LBSO. The resultant O3-LBSO films showed improved mobility values up to 115 cm2 V-1 s-1, which is among the highest in LBSO films on SrTiO3 substrates and comparable to LBSO films with buffer layers., Comment: 16 pages including 5 figures

Growth conditions for the epitaxial Fe0.5Ni0.5 (FeNi) thin films were optimized in order to enhance crystallinity and magnetism. Epitaxial thin films of FeNi (111) were successfully grown on (0001) Al2O3 substrates at substrate temperature of 400 °C. In addition, thickness dependence on structural and magnetic behavior of epitaxial FeNi thin films has been investigated using x-ray diffraction, x-ray reflectometry and vibrating sample magnetometer. The change in magnetization and coercivity are explained as a result of various anisotropic effects (stress, magneto-crystalline and shape anisotropies) as well as domain size in the FeNi film with a thickness range 195 A to 703 A. It is observed that, the magnetism is strongly dependent upon the microstructure and the thickness of the magnetic layer.

We report herein that the carrier mobility of the 2%-La-doped BaSnO3 (LBSO) films on (001) SrTiO3 and (001) MgO substrates strongly depends on the thickness whereas it is unrelated to the lattice mismatch (+5.4% for SrTiO3, -2.3% for MgO). Although we observed large differences in the lattice parameters, the lateral grain size (~85 nm for SrTiO3, ~20 nm for MgO), the surface morphology and the density of misfit dislocations, the mobility increased almost simultaneously with the thickness in both cases and saturated at ~100 cm2 V-1 s-1, together with the approaching to the nominal carrier concentration (=[2% La3+]), clearly indicating that the behavior of mobility depends on the film thickness. The present results would be beneficial to understand the behavior of mobility and fruitful to further enhance the mobility of LBSO films., Comment: 15 pages, including 4 figures

Nd1-xSrxMnO3 is a well-known manganite due to close connection among structure, transport, magnetism, and chemistry. Thus, it would be an ideal system to study the modification of physical properties by external stimuli including control of stoichiometry in growth. In this work, we show that an abrupt change of electronic and magnetic properties can be achieved by a subtle change of oxygen partial pressure in pulsed laser deposition. Interestingly, the pressure indeed modulates cation stoichiometry. We clearly observed that the films grown at 140 mTorr and higher showed clear insulator to metal transition and stronger magnetism, commonly found in less hole doping, while the films grown at 130 mTorr and lower showed insulating behavior and weak magnetism. From soft x-ray spectroscopic methods, we clearly observed the compositional difference in those thin films. This result is further supported by scattering of lighter elements in high oxygen partial pressure but not by anion deficiency in growth.

In this work, we propose a structural modification to the 3-dimensional vertical gate NAND flash memory that will reduce the charge interference caused by stored charge on the opposite facing cell. In the barrier oxide structure (BOS), an oxide layer was inserted into the center of the body to physically block the conduction electrons moving to and from the channel regions influenced by the charge stored on either of the Oxide-Nitride-Oxide (ONO) trap layers. In the virtual ground structure (VGS), a highly p-type doped poly silicon layer was inserted to act as a virtual ground to reduce the electric-field changes caused by the stored change on the ONO trap layers. We investigated the I-V characteristics of the different structures using 3-D TCAD simulation tool, depending on the body type (crystalline or poly silicon) at double programming and single programming. We confirmed that the charge interference problem was reduced significantly by the BOS and VGS modifications in the crystalline silicon and high quality poly silicon body structures.