Cathodoluminescence of nanocrystalline Y2O3:Eu3+ with various Eu3+ concentrations

© The Author(s) 2014. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 License (CC BY, http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse of the work in any medium, provided the original work is properly cited.This article has been made available through the Brunel Open Access Publishing Fund.Herein a study on the preparation and cathodoluminescence of monosized spherical nanoparticles of Y2O3:Eu3+ having a Eu3+ concentration that varies between 0.01 and 10% is described. The luminous efficiency and decay time have been determined at low a current density, whereas cathodoluminescence-microscopy has been carried out at high current density, the latter led to substantial saturation of certain spectral transitions. A novel theory is presented to evaluate the critical distance for energy transfer from Eu3+ ions in S6 to Eu3+ ions in C2 sites. It was found that Y2O3:Eu3+ with 1–2% Eu3+ has the highest luminous efficiency of 16lm/w at 15keV electron energy. Decay times of the emission from 5D0 (C2) and 5D1 (C2) and 5D0 (S6) levels were determined. The difference in decay time from the 5D0 (C2) and 5D1 (C2) levels largely explained the observed phenomena in the cathodoluminescence-micrographs recorded with our field emission scanning electron microscope

Effects of Acid Treatment on the SEM-EDX Characteristics of Kaolin Clay

Raw kaolin was refluxed by sulphuric acid in variable concentrations of 2 M, 4 M, 6 M and 8 M. The morphology and elemental compositions of the acid-leached kaolin were analyse by Field Scanning Electron Microscopy (FESEM) and Energy Dispersive X-ray analysis (EDX) respectively. The disintegration and leaching of Al3+ ions of the clay are determined by FESEM studies. The acid treatment increases the silicon content and decreases aluminium content as revealed by EDX analysis. The leaching of Al3+ ions increases with gradual increase in concentration of the acid. Therefore, kaolin reflux with acid at lower strength (2 M and 4 M) are more dispersed and more industrially useful than that which is treated at higher acid strength

Chromosome Centromeres: Structural and Analytical Investigations with High Resolution Scanning Electron Microscopy in Combination with Focused Ion Beam Milling

Whole mount mitotic metaphase chromosomes of different plants and animals were investigated with high resolution field emission scanning electron microscopy (FESEM) to study the ultrastructural organization of centromeres, including metacentric, acrocentric, telocentric, and holocentric chromosome variants. It could be shown that, in general, primary constrictions have distinctive ultrastructural features characterized by parallel matrix fibrils and fewer smaller chromomeres. Exposure of these structures depends on cell cycle synchronization prior to chromosome isolation, chromosome size, and chromosome isolation technique. Chromosomes without primary constrictions, small chromosomes, and holocentric chromosomes do not exhibit distinct ultrastructural elements that could be directly correlated to centromere function. Putative spindle structures, although rarely observed, spread over the primary constriction to the bordering pericentric regions. Analytical FESEM techniques, including specific DNA staining with Pt blue, staining of protein as a substance class with silver-colloid, and artificial loosening of fixed chromosomes with proteinase K, were applied, showing that centromere variants and ultrastructural elements in the centromere differ in DNA and protein distribution. Immunogold localization allowed high-resolution comparison between chromosomes with different centromere orientations of the distribution of centromere-related histone variants, phosphorylated histone H3 (ser10), and CENH3. A novel application of FESEM combined with focused ion beam milling (FIB) provided new insights into the spatial distribution of these histone variants in barley chromosomes. Copyright (C) 2009 S. Karger AG, Base

Nanostructured Ti thin films by magnetron sputtering at oblique angles

The growth of Ti thin films by the magnetron sputtering technique at oblique angles and at room temperature is analysed from both experimental and theoretical points of view. Unlike other materials deposited in similar conditions, the nanostructure development of the Ti layers exhibits an anomalous behaviour when varying both the angle of incidence of the deposition flux and the deposition pressure. At low pressures, a sharp transition from compact to isolated, vertically aligned, nanocolumns is obtained when the angle of incidence surpasses a critical threshold. Remarkably, this transition also occurs when solely increasing the deposition pressure under certain conditions. By the characterization of the Ti layers, the realization of fundamental experiments and the use of a simple growth model, we demonstrate that surface mobilization processes associated to a highly directed momentum distribution and the relatively high kinetic energy of sputtered atoms are responsible for this behaviourJunta de Andalucía P12-FQM- 2265Ministerio de Ciencia e Innovación CSD2008- 00023, MAT2013-42900-P, MAT2013-40852-R, MAT2014-59772-C2-1, MAT2011- 2908

Characterization of GaN Nanorods Fabricated Using Ni Nanomasking and Reactive Ion Etching: A Top-Down Approach

Large thermal mismatch between GaN surface and sapphire results in compressive stress in Gallium Nitride (GaN) layer which degrades the device performance. Nanostructuring the GaN can reduce this stress leading to reduction in Quantum Confined Stark Effect. Aligned GaN nanorods based nanodevices have potential applications in electronics and optoelectronics. This paper describes the fabrication of GaN nanorods using Ni nanomasking and reactive ion etching. The morphology of GaN nanorods was studied by field emission scanning electron microscopy. The optical properties of GaN nanorods were studied by Cathodoluminescence (CL) spectroscopy. CL results revealed the existence of characteristic band-edge luminescence and yellow band luminescence. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3099