Search results for "ELECTRON"
showing 10 items of 24810 documents
Neutron diffraction study of microstructural and magnetic effects in fine particle NiO powders
2016
Nickel oxide powders with grain sizes ranging from 100 to 1500 nm have been studied by high-resolution neutron diffraction. We have found that the atomic structure, the antiferromagnetic ordering, and the value of the nickel magnetic moments inherent in the bulk material of NiO are still preserved and are nearly independent of the average size of the grains. The sizes of the coherently scattering atomic and magnetic domains were estimated independently owing to a complete separation of the nuclear and magnetic peaks in the neutron diffraction patterns. It is shown that the finite-size and surface disorder effects in particles at the submicron scale have a more pronounced influence on the ma…
FTIR Analysis of Electron Irradiated Single and Multilayer Si<sub>3</sub>N<sub>4</sub> Coatings
2018
Silicon nitride (Si3N4) due to its good mechanical and electrical properties is a promising material for wide range of applications, including exploitation under action of ionizing radiation. For estimating the changes of chemical bonds in silicon nitride nanolayers under action of ionizing radiation single and multi-layer silicon nitride nanolayered coatings on prepared Si subtrate were investigated by means of Fourier transform infrared spectrometry. Three main groups of signals were identified in both types of nanolayers, at 510 and 820 cm-1 and group of broad signals at 1000-1200 cm-1. Irradiation with accelerated electrons up to absorbed doses 36 MGy causes minor changes of signal inte…
Investigation of mechanical and electrical properties of Li doped sodium niobate ceramic system
2016
ABSTRACTThe Na0.96Li0.04NbO3 ceramic solid solution was prepared by means of a two-stage hot-pressing technology. The X-ray diffraction analysis showed the formation of a single perovskite phase with an orthorhombic symmetry in the investigated composition. The microstructure and EDS measurements were performed. They confirmed the high purity and the expected qualitative composition. A good homogeneity of the microstructures and a small degree of porosity were observed. The elastic modulus (the Young's modulus E, shear modulus G, and Poisson's ratio ν) of Na0.96Li0.04NbO3 were determined with the use of an ultrasonic method. The electrical properties of Na0.96Li0.04NbO3 ceramics were invest…
Molecular dynamics simulations of nanometric metallic multilayers: Reactivity of the Ni-Al system
2011
The reactivity of a layered Ni-Al-Ni system is studied by means of molecular dynamics simulations, using an embedded-atom method type potential. The system, made of an fcc-Al layer embedded in fcc-Ni, is initially thermalized at the fixed temperature of 600 K. The early interdiffusion of Ni and Al at interfaces is followed by the massive diffusion of Ni in the Al layer and by the spontaneous phase formation of $B2$-NiAl. The solid-state reaction is associated with a rapid system heating, which further enhances the diffusion processes. For longer times, the system may partly lose some its $B2$-NiAl microstructure in favor of the formation of $L{1}_{2}$-${\mathrm{Ni}}_{3}\mathrm{Al}$. This st…
How Gettering Affects the Temperature Sensitivity of the Implied Open Circuit Voltage of Multicrystalline Silicon Wafers
2019
The temperature sensitivity of the open circuit voltage of a solar cell is mainly driven by changes in the intrinsic carrier concentration, but also by the temperature dependence of the limiting recombination mechanisms in the cell. This paper investigates the influence of recombination through metallic impurities on the temperature sensitivity of multicrystalline silicon wafers. Spatially resolved temperature dependent analysis is performed to evaluate the temperature sensitivity of wafers from different brick positions before and after being subjected to phosphorus diffusion gettering. Local spatial analysis is performed on intra-grain areas, dislocation clusters and grain boundaries. Lar…
Luminescence properties of chlorine molecules in glassy SiO 2 and optical fibre waveguides
2017
The support from Latvian Research Program IMIS 2, project “Photonics and materials for photonics” is acknowledged. K.K. was partially supported by the Collaborative Research Project of Materials and Structures Laboratory, Tokyo Institute of Technology. The publication costs of this article were covered by the Estonian Academy of Sciences and the University of Tartu.
Time-resolved pulsed OSL of ceramic YAP:Mn phosphors
2019
The paper deals with the results of comparative study on time-resolved pulsed optically stimulated luminescence (TR-OSL) response of ceramic YAP:Mn materials prepared by different methods. In parti...
Study of the P3HT/PCBM interface using photoemission yield spectroscopy
2016
Photogeneration efficiency and charge carrier extraction from active layer are the parameters that determine the efficiency of organic photovoltaics (OPVs). Devices made of organic materials often consist of thin (up to 100nm) layers. At this thickness different interface effects become more pronounced. The electron affinity and ionization energy shift can affect the charge carrier transport across metal-organic interface which can affect the performance of the entire device. In the case of multilayer OPVs, energy level compatibility at the organic-organic interface is as important. Photoemission yield spectroscopy was used for organic-organic interface study by ionization energy measuremen…
Static and dynamic structure of $ZnWO_4$ nanoparticles
2011
Abstract Static and dynamic structure of ZnWO 4 nanoparticles, synthesized by co-precipitation technique, has been studied by temperature dependent x-ray absorption spectroscopy at the Zn K-edge and W L 3 -edge. Complementary experimental techniques, such as x-ray powder diffraction, Raman and photoluminescence spectroscopies, have been used to understand the variation of vibrational, optical, and structural properties of nanoparticles, compared to microcrystalline ZnWO 4 . Our results indicate that the structure of nanoparticles experiences strong relaxation leading to the significant distortions of the WO 6 and ZnO 6 octahedra, being responsible for the changes in optical and vibrational …
Outstanding nonlinear optical properties of methylammonium- and Cs-PbX3 (X = Br, I, and Br–I) perovskites: Polycrystalline thin films and nanoparticl…
2019
Metal Halide Perovskites (MHPs) have arisen as promising materials to construct cost-effective photovoltaic and light emission devices. The study of nonlinear optical properties of MHPs is necessary to get similar success in nonlinear photonic devices, which is practically absent in the literature. The determination of the third order nonlinear coefficients is typically done by the Z-scan technique, which is limited by the scattering of polycrystalline thin films. In this work, we have studied nonlinear optical properties of polycrystalline CH3NH3PbX3 (MAPbX3) thin films and colloidal CsPbX3 nanoparticles with three different bandgaps (X3 = I3, Br3, and Br1.5I1.5). Their bright generation o…