Screening of the quantum-confined Stark effect in AlN/GaN nanowire superlattices by Germanium doping

We report on electrostatic screening of polarization-induced internal electric fields in AlN/GaN nanowire heterostructures with Germanium-doped GaN nanodiscs embedded between AlN barriers. The incorporation of Germanium at concentrations above $10^{20}\,\text{cm}^{-3}$ shifts the photoluminescence emission energy of GaN nanodiscs to higher energies accompanied by a decrease of the photoluminescence decay time. At the same time, the thickness-dependent shift in emission energy is significantly reduced. In spite of the high donor concentration a degradation of the photoluminescence properties is not observed.Comment: Manuscript including Supplemental material (15 pages, 5 figures

Distributions of Noble Metal Pd and Pt in Mesoporous Silica

Mesoporous silica nanostructures have been synthesized and loaded with Pd and Pt catalytic noble metals. It is found that Pd forms small nanoclusters (3–5 nm) on the surface of the mesoporous structure whereas Pt impregnation results in the inclusion of Pt nanostructures within the silica hexagonal pores (from nanoclusters to nanowires). It is observed that these materials have high catalytic properties for CO–CH4 combustion, even in a thick film form. In particular, results indicate that the Pt and Pd dispersed in mesoporous silica are catalytically active as a selective filter for gas sensors

Distributions of Nobel Metal Pd and Pt in Mesoporous Silica

Mesoporous silicananostructures have been synthesized and loaded with Pd and Pt catalytic noble metals. It is found that Pd forms small nanoclusters (3–5 nm) on the surface of the mesoporous structure whereas Pt impregnation results in the inclusion of Pt nanostructures within the silica hexagonal pores (from nanoclusters to nanowires). It is observed that these materials have high catalyticproperties for CO–CH4CO–CH4CO–CH4 combustion, even in a thick film form. In particular, results indicate that the Pt and Pd dispersed in mesoporous silica are catalytically active as a selective filter for gas sensors

Strain-driven elastic and orbital-ordering effects on thickness-dependent properties of manganite thin films

We report on the structural and magnetic characterization of (110) and (001) La2/3Ca1/3MnO3 (LCMO) epitaxial thin films simultaneously grown on (110) and (001)SrTiO3 substrates, with thicknesses t varying between 8 nm and 150 nm. It is found that while the in-plane interplanar distances of the (001) films are strongly clamped to those of the substrate and the films remain strained up to well above t=100 nm, the (110) films relax much earlier. Accurate determination of the in-plane and out-of-plane interplanar distances has allowed concluding that in all cases the unit cell volume of the manganite reduces gradually when increasing thickness, approaching the bulk value. It is observed that the magnetic properties (Curie temperature and saturation magnetization) of the (110) films are significantly improved compared to those of (001) films. These observations, combined with 55Mn-nuclear magnetic resonance data and X-ray photoemission spectroscopy, signal that the depression of the magnetic properties of the more strained (001)LCMO films is not caused by an elastic deformation of the perovskite lattice but rather due to the electronic and chemical phase separation caused by the substrate-induced strain. On the contrary, the thickness dependence of the magnetic properties of the less strained (110)LCMO films are simply described by the elastic deformation of the manganite lattice. We will argue that the different behavior of (001) and (110)LCMO films is a consequence of the dissimilar electronic structure of these interfaces.Comment: 16 pages, 15 figure

Selective Area Grown Semiconductor-Superconductor Hybrids: A Basis for Topological Networks

We introduce selective area grown hybrid InAs/Al nanowires based on molecular beam epitaxy, allowing arbitrary semiconductor-superconductor networks containing loops and branches. Transport reveals a hard induced gap and unpoisoned 2e-periodic Coulomb blockade, with temperature dependent 1e features in agreement with theory. Coulomb peak spacing in parallel magnetic field displays overshoot, indicating an oscillating discrete near-zero subgap state consistent with device length. Finally, we investigate a loop network, finding strong spin-orbit coupling and a coherence length of several microns. These results demonstrate the potential of this platform for scalable topological networks among other applications.Comment: NBI QDEV 201

Surface States in Template Synthesized Tin Oxide Nanoparticles

Tin–oxide nanoparticles with controlled narrow size distributions are synthesized while physically encapsulated inside silica mesoporous templates. By means of ultraviolet-visible spectroscopy, a redshift of the optical absorbance edge is observed. Photoluminescence measurements corroborate the existence of an optical transition at 3.2 eV. The associated band of states in the semiconductor gap is present even on template-synthesized nanopowders calcined at 800 °C, which contrasts with the evolution of the gap states measured on materials obtained by other methods. The gap states are thus considered to be surface localized, disappearing with surface faceting or being hidden by the surface-to-bulk ratio decrease

Electric field assisted dissolution of metal clusters in metal island films for photonic heterostructures

The dissolution of metal clusters in metal island films by the simultaneous application of electric field and temperature is reported. The consequent fading of surface plasmon resonance greatly modifies the optical properties of the samples. The dissolution process is verified in island films of different metals, obtained under different conditions and covered by different dielectric materials, as well as on multilayer dielectric stacks showing interferential properties. The tailoring possibilities of the optical behavior of metal island films combined with the inexpensive technical requirements of this approach open up the possibility to produce low-cost photonic heterostructures

De la casa a la ciudad: Criterios para comprender la relevancia de las asambleas paulinas en 1Cor

The frequency with which Paul has recourse to affective, family language as well as showing one of his typical configuration models for the evkklhsi,a, at the same time reveals a controversial context: the congregations that the apostle created had no family ties, but sought to be one single family and one single house, yet retaining other characteristics similar to a public organisation. This ambiguity is easily detected in the actual places of meeting, which had features that were both private and public. The present text seeks to shed light on this ambiguity, supported by criteria relating to domestic spaces and the difference between private and public. And we will see, in due course, how these criteria emerge in the Paul’s First Epistle to the Corinthians in both directions: reflecting the ambiguity and seeking a greater public and political dimension for the evkklhsi,a.A frequência e a intensidade com que Paulo recorre à linguagem afectiva mostram um dos seus modelos típicos de configuração da evkklhsi,a e revelam, ao mesmo tempo, um contexto polémico: aquelas assembleias que o apóstolo criou não tinham laços familiares, mas pretendiam ser uma só família e uma só casa, mantendo outras características semelhantes à de uma organização pública. Esta ambiguidade detecta-se bem nos próprios espaços de reunião, que tinham tanto traços privados como públicos. Procuraremos iluminar tal ambiguidade suportados por critérios referentes aos espaços domésticos e à diferenta entre privado e público. E veremos, por fim, como estes critérios emergem na Primeira Carta de Paulo aos Coríntios nos dois sentidos: reflectindo a ambiguidade e procurando uma maior dimensão pública e política para a evkklhsi,a

Synthesis of Tin Oxide Nanostructures with Controlled Particle Size Using Mesoporous Frameworks

Tin oxide nanostructures with controlled narrow particle size distribution were synthesized inside silica mesoporous templates. In this way, particle growth was blocked by physically corseting the tin compound inside the silica frameworks, the pore diameter of which determines the final tin oxide crystallite size distribution. Template structures were subsequently eliminated by chemical methods to collect the unsupported semiconductor nanoparticles. Thus obtained tin oxed nanopowders, with particle sizes in the range between 6 and 10 nm, were structurally, chemically, and electically characterized. The results are compared with those obtained from the characterization of larger crystallite materials