Search results for "RAI"
showing 10 items of 15372 documents
Reversed polarized emission in highly strained a-plane GaN/AlN multiple quantum wells
2010
The polarization of the emission from a set of highly strained $a$-plane GaN/AlN multiple quantum wells of varying well widths has been studied. A single photoluminescence peak is observed that shifts to higher energies as the quantum well thickness decreases due to quantum confinement. The emitted light is linearly polarized. For the thinnest samples the preferential polarization direction is perpendicular to the wurtzite $c$ axis with a degree of polarization that decreases with increasing well width. However, for the thickest well the preferred polarization direction is parallel to the $c$ axis. Raman scattering, x-ray diffraction, and transmission electron microscopy studies have been p…
Transport properties of Bi2Sr2Ca2Cu3O10+δ Bicrystal Grain Boundary Josephson Junctions and SQUIDs
1996
Josephson junctions and SQUIDs on 36.8° SrTiO 3 bicrystal substrates were prepared from epitaxial Bi 2 Sr 2 Ca 2 Cu 3 O 10+δ thin films with critical temperatures around 95K. The current-voltage characteristics are well described by the resistively and capacitively shunted junction model. I c R n products of 50μV at 77K and 0.7mV at 4.2K have been reached. The I c (B) dependence is symmetric to B = 0 with an I c suppression of 90% in the first minimum. Nevertheless it turns out, that the junctions are inhomogeneous on a μm scale. SQUID modulations observed at 78K indicate a flux-voltage transfer function of 2.7μV/Φ 0 at this temperature.
Analytic $JV$ -Characteristics of Ideal Intermediate Band Solar Cells and Solar Cells With Up and Downconverters
2017
The ideal diode equation is regularly used to describe the $\textit {JV}$ -characteristic of single junction solar cells. The connection between the diode equation and fundamental physics is the application of the Boltzmann approximation to describe the fluxes of photons emitted by the cell. In this paper, this approximation is used to derive analytic $\textit {JV}$ -characteristics for three photovoltaic high-efficiency concepts, intermediate band solar cells, and solar cells optically coupled to up and downconverters. These three concepts share the common feature that they allow excitation of electrons between at least three energy levels, which assures a better utilization of the solar s…
Luminescence characteristics of magnesium aluminate spinel crystals of different stoichiometry
2019
We are grateful to Drs E. Vasil’chenko and A. Maaroos for the help with experiments and useful discussions. This work has been carried out within the framework of the EUROfusion Consortium and has received funding from the Euratom research and training programme 2014-2018 under grant agreement No 633053. The views and opinions expressed herein do not necessarily reflect those of the European Commission. In addition, the research leading to these results has received funding from the Estonian Research Council Institutional Research Funding IUT02-26.
Effect of surface disorder on the domain structure of PLZT ceramics
2017
ABSTRACTPb1-xLax(Zr0.65Ti0.35)1-x/4O3 (PLZT x/65/35) ceramics were studied by Piezoresponse Force Microscopy in order to understand the origin of domain structure as a function of La content. We show that the domain topology is mainly determined by the composition and grain size. The characteristic correlation length decreases with increasing La content, being sensitive also to the synthesis method. The behavior of the correlation length is linked to the macroscopic properties, showing a strong increase of disorder with La doping. The roughness exponent for the domain wall in PLZT 9/65/35 is close to 2/3 indicating 1D character of domain walls in relaxors.
ZnMgO-based UV photodiodes: a comparison of films grown by spray pyrolysis and MBE
2016
Detecting the UV part of the spectrum is fundamental for a wide range of applications where ZnMgO has the potential to play a central role. The shortest achievable wavelength is a function of the Mg content in the films, which in turn is dependent on the growth technique. Moreover, increasing Mg contents lead to an electrical compensation of the films, which directly affects the responsivity of the photodetectors. In addition, the metal-semiconductor interface and the presence of grain boundaries have a direct impact on the responsivity through different gain mechanisms. In this work, we review the development of ZnMgO UV Schottky photodiodes using molecular beam epitaxy and spray pyrolysis…
Production of dense nanostructured materials using FAPAS and SPS techniques
2011
International audience
A rare polymeric azido-bridged copper(II) chain with a pentameric repeating unit: Synthesis, structure and magnetic properties
2013
International audience; The novel polymeric chain copper(II) complex [Cu4(μ-Mesalpn)2(μ1,1,1-N3)2(μ1,1-N3)2Cu]n (1) was prepared by the reaction of Cu(NO3)2·3H2O with Mesalpn in the presence of an excess of NaN3. A single-crystal X-ray diffraction study showed an unusual 1D polymeric chain based on pentanuclear Cu5 units with both μ1,1,1-N3 and μ1,1-N3 bridges, and with three independent Cu(II) ions presenting three different coordination numbers (4, 5 and 6). The magnetic susceptibility data show the presence of dominant anti-ferromagnetic interactions.
The C–I···–O–N+ Halogen Bonds with Tetraiodoethylene and Aromatic N-Oxides
2020
The nature of C–I⋯⁻O–N⁺ interactions, first of its kind, between non-fluorinated tetraiodoethylene XB-donor and pyridine N-oxides (PyNO) are studied by single-crystal X-ray diffraction (SCXRD) and ...