Homologous series are layered phases that can have a range of stoichiometries depending on an index n. Examples of perovskite-related homologous series include (ABO3)nAO Ruddlesden–Popper phases and (Bi2O2) (An−1BnO3n+1) Aurivillius phases. It is challenging to precisely control n because other members of the homologous series have similar stoichiometry and a phase with the desired n is degenerate in energy with syntactic intergrowths among similar n values; this challenge is amplified as n increases. To improve the ability to synthesize a targeted phase with precise control of the atomic layering, we apply the x-ray diffraction (XRD) approach developed for superlattices of III–V semiconductors to measure minute deviations from the ideal structure so that they can be quantitatively eradicated in subsequent films. We demonstrate the precision of this approach by improving the growth of known Ruddlesden–Popper phases and ultimately, by synthesizing an unprecedented n = 20 Ruddlesden–Popper phase, (ATiO3)20AO where the A-site occupancy is Ba0.6Sr0.4. We demonstrate the generality of this method by applying it to Aurivillius phases and the Bi2Sr2Can–1CunO2n+4 series of high-temperature superconducting phases.
Magnetostrictive materials transduce magnetic and mechanical energies and when combined with piezoelectric elements, evoke magnetoelectric transduction for high-sensitivity magnetic field sensors and energy-efficient beyond-CMOS technologies. The dearth of ductile, rare-earth-free materials with high magnetostrictive coefficients motivates the discovery of superior materials. Fe1−xGax alloys are amongst the highest performing rare-earth-free magnetostrictive materials; however, magnetostriction becomes sharply suppressed beyond x = 19% due to the formation of a parasitic ordered intermetallic phase. Here, we harness epitaxy to extend the stability of the BCC Fe1−xGax alloy to gallium compositions as high as x = 30% and in so doing dramatically boost the magnetostriction by as much as 10x relative to the bulk and 2x larger than canonical rare-earth based magnetostrictors. A Fe1−xGax − [Pb(Mg1/3Nb2/3)O3]0.7−[PbTiO3]0.3 (PMN-PT) composite magnetoelectric shows robust 90° electrical switching of magnetic anisotropy and a converse magnetoelectric coefficient of 2.0 × 10−5 s m−1. When optimally scaled, this high coefficient implies stable switching at ~80 aJ per bit.
The low dielectric loss underlying the record performance of strained (SrTiO 3) n SrO Ruddlesden-Popper films as tunable microwave dielectrics was postulated to arise from (SrO) 2 faults accommodating local non-stoichiometric defects. Here we explore the effect of non-stoichiometry on (SrTiO 3) n SrO using positron annihilation lifetime spectroscopy on a composition series of 300 nm thick n = 6 (Sr 1+δ TiO 3) n SrO thin films. These films show titaniumsite vacancies across the stoichiometry series, with evidence that TiO x vacancy complexes dominate. Little change in defect populations is observed across the series indicating the ability of Ruddlesden-Popper phases to accommodate ± 5% off-stoichiometry. This ability for defect accommodation is corroborated by scanning transmission electron microscopy with electron energy loss spectroscopy.
Unlike many superlattice structures, Ruddlesden–Popper phases have atomically abrupt interfaces useful for interrogating how periodic atomic layers affect thermal properties. Here, we measure the thermal conductivity in thin films of the n = 1–5 and 10 members of the (SrTiO3)nSrO Ruddlesden–Popper superlattices grown by molecular-beam epitaxy and compare the results to a single crystal of the n = 1 Ruddlesden–Popper SrLaAlO4. The thermal conductivity cross-plane to the superlattice layering (k33) is measured using time-domain thermoreflectance as a function of temperature and the results are compared to first-principles calculations. The thermal conductivity of this homologous series decreases with increasing interface density. Characterization by x-ray diffraction and scanning transmission electron microscopy confirms that these samples have a Ruddlesden–Popper superlattice structure.
The vertical growth of Si nanowires on non‐monocrystalline substrates is of significant interest for photovoltaics and other energy harvesting applications. In this paper, we present results on using poly‐Si layers formed by aluminum‐induced crystallization (AIC) on fused quartz wafers as an alternative substrate for the vapor‐liquid‐solid (VLS) growth of vertical Si nanowires. Oxidation of the Al surface to Al2O3 before the a‐Si deposition was shown to be a key requirement in the formation of the poly‐Si template since it promotes the crystallization of the a‐Si into Si(111) which is required for vertical silicon nanowire growth. The effect of Al deposition technique (DC sputtering versus thermal evaporation) on a‐Si crystallization and Si nanowire growth was investigated. The use of Al thermal evaporation yielded AIC poly‐Si layers with the highest fraction of 〈111〉 grains as measured by orientation imaging microscopy (OIM) which enabled the growth of vertical Si nanowires. Cross‐sectional transmission electron microscopy analysis confirmed that the 〈111〉 Si nanowires grew epitaxially off of {111}poly‐Si grains in the AIC layer. This study demonstrates the potential of using AIC poly‐Si as a template layer for the vertical growth of silicon nanowires on amorphous substrates.
The Ruddlesden–Popper (A n+1B n O3n+1) compounds are highly tunable materials whose functional properties can be dramatically impacted by their structural phase n. The negligible differences in formation energies for different n can produce local structural variations arising from small stoichiometric deviations. Here, we present a Python analysis platform to detect, measure, and quantify the presence of different n-phases based on atomic-resolution scanning transmission electron microscopy (STEM) images. We employ image phase analysis to identify horizontal Ruddlesden–Popper faults within the lattice images and quantify the local structure. Our semiautomated technique considers effects of finite projection thickness, limited fields of view, and lateral sampling rates. This method retains real-space distribution of layer variations allowing for spatial mapping of local n-phases to enable quantification of intergrowth occurrence and qualitative description of their distribution suitable for a wide range of layered materials.
a chalasia Presents as a Rare Disorder, affecting only 0.3-1.63 per 100,000 adults yearly, worldwide (Sadowski, ackah, Jiang, & Svenson, 2010). In the United States, it is estimated that 20,000-40,000 patients are affected by it, occurring equally amongst genders (Vaezi, Pandolfino, yadlapati, Greer, & Kavitt, 2020) with no racial correlation (Brindise, Khashab, & El abiad, 2021). Classic symptoms of achalasia include heartburn, dysphagia, regurgitation (Brindise et al., 2021), chest pain, and weight loss (Chadalavada, Thota, Raja, & Sanaka, 2020). achalasia is the leading indication for performance of peroral endoscopic myotomy to alleviate its symptoms, more frequently referred to by the acronym "POEM" (Chadalavada et al., 2020). POEMs are increasingly practiced worldwide since its original advent (Fajardo, Petrov, Bakhos, & abbas, 2020). Achalasia TypesThe Chicago classification divides achalasia into three subtypes (Pandolfino et al., 2008). achalasia Type I is characterized by aperistalsis with absence of panesophageal pressurization (Inoue et al., 2018), and it is the
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