Search results for "Germanium"
showing 10 items of 249 documents
X-ray irradiation effects on a multistep Ge-doped silica fiber produced using different drawing conditions
2011
International audience; We report an experimental study based on confocal microscopy luminescence (CML) and electron paramagnetic resonance (EPR) measurements to investigate the effects of the X-ray (from 50 krad to 200 Mrad) on three specific multistep Ge doped fibers obtained from the same preform by changing some of the drawing conditions (tension and speed). CML data show that, both before and after the irradiation, Germanium Lone Pair Center (GLPC) concentrations are similarly distributed along the diameters of the three fibers and they are partially reduced by irradiation. The irradiation induces also the Non Bridging Oxygen Hole Center (NBOHC) investigated by CML and other paramagnet…
Evolution of Photo-induced defects in Ge-doped fiber/preform: influence of the drawing
2011
International audience; We have studied the generation mechanisms of two different radiation-induced point defects, the Ge(1) and Ge(2) centers, in a germanosilicate fiber and in its original preform. The samples have been investigated before and after X-ray irradiation using the confocal microscopy luminescence and the electron paramagnetic resonance techniques. Our experimental results show the higher radiation sensitivity of the fiber as compared to the perform and suggest a relation between Ge(1) and Ge(2) generation. To explain our data we have used different models, finding that the destruction probability of the Ge(1) and Ge(2) defects is larger in fiber than in preform, whereas the …
Synthesis and structural characterisation of germanium(II) halide complexes with neutral N-donor ligands.
2010
The Ge(II) complexes [GeX(2)(L-L)] (L-L = 1,10-phen (X = Cl, Br); L-L = Me(2)N(CH(2))(2)NMe(2), 2,2'-bipy (X = Cl)), [GeX(L-L)][GeX(3)] (L-L = 2,2'-bipy (X = Br); L-L = pmdta (MeN(CH(2)CH(2)NMe(2))(2)) (X = Cl, Br)) have been prepared and their crystal structures determined. The crystal structure of [GeCl(2){Me(2)N(CH(2))(2)NMe(2)}] shows a weakly associated centrosymmetric dimer based upon distorted square-pyramidal coordination at Ge(II) and containing asymmetrically chelating diamine ligands. The structure of [GeCl(2)(2,2'-bipy)] contains a chelating 2,2'-bipy ligand and forms a zig-zag chain polymer via long-range intermolecular Ge...Cl bridging interactions, leading to a very distorted…
Improved limits on the lepton-flavor violating decays tau(-) -> l(-)l(+)l(-)
2007
A search for the neutrinoless, lepton-flavor violating decay of the tau lepton into three charged leptons has been performed using 376fb-1 of data collected at an e+e- center-of-mass energy around 10.58 GeV with the BABAR detector at the SLAC PEP-II storage rings. In all six decay modes considered, the numbers of events found in data are compatible with the background expectations. Upper limits on the branching fractions are set in the range (4-8)×10-8 at 90% confidence level. © 2007 The American Physical Society.
Germanium modified BaTiO3as a promising electroceramics
2016
ABSTRACTThe polycrystalline sample of BaTi0.95Ge0.05O3 was prepared by solid-phase reaction using a conventional method. The morphology of investigated sample was characterised by scanning electron microscopy (SEM). The results allowed to determining the stoichiometry of the material and evaluate their microstructure. High quality samples were investigated, the grains are well shaped without of a glassy phase. The dielectric properties of the BaTi0.95Ge0.05O3 ceramics were determined. The results were compared with these ones obtained for pure BaTiO3. The obtained data indicated that the substitution of Ge+4 ions had an influence on the values of the real (ϵ′) and imaginary (ϵ″) parts of el…
Photoconductivity of Germanium Nanowire Arrays Incorporated in Anodic Aluminum Oxide
2007
Photoconductivity of germanium nanowire arrays of 50 and 100 nm diameter incorporated into Anodic Aluminum Oxide (AAO) membranes illuminated with visible light is investigated. Photocurrent response to excitation radiation with time constants faster than 10−4 s were governed by absorption of incident light by nanowires, while photokinetics with time constants of the order of 10−3 s originates from the photoluminescence of the AAO matrix. Possible applications of nanowire arrays inside AAO as photoresistors are discussed.
Formation of optically active oxygen deficient centers in Ge-doped SiO2 by γ- and β-ray irradiation
2010
Abstract We report an experimental study on the comparison between the γ- or β-ray induced Ge related point defects in Ge-doped silica. Silica samples doped with ∼2.2 1017 Ge atoms/cm3 produced with the sol–gel technique have been irradiated with γ-ray or with β-ray. The effects of the irradiation have been investigated by optical absorption, photoluminescence and electron paramagnetic resonance spectroscopy in order to evaluate the generation and the dependence on dose of the Ge(1), E’Ge, GLPC (Germanium lone pair center) and H(II) point defects. No relevant differences between the concentrations of γ- or β-ray induced Ge(1) and E’Ge point defects have been observed and, in addition, it ha…
Concentration growth and thermal stability of gamma-ray induced germanium lone pair center in Ge-doped sol–gel a-SiO2
2009
Abstract We report an experimental study of the concentration growth by γ-ray irradiation of germanium lone pair center (GLPC) in 10 4 part per million molar Ge-doped sol–gel silica. The data show that γ-ray induced GLPC concentration increases linearly up to ∼5 MGy and then it seems to reach a limit value. In addition to the dose dependence, we have studied the thermal stability of the radiation induced GLPC in ambient atmosphere up to 415 °C. We found that the concentration of this latter GLPC starts to decrease at ∼300 °C, at variance to native GLPC, suggesting that the annealing is related to irradiation products. After the thermal treatments the photoluminescence (PL) activity of the γ…
Photosensitivity of silica glass with germanium studied by photoinduced of thermally stimulated luminescence with vacuum ultraviolet radiation
2003
Photosensitivity of the germanium-doped silica was studied through kinetics of recombination of the created defects in isothermal and thermally stimulated luminescence (TSL) regimes. The main observed luminescence contains bands mainly due to Ge oxygen deficient center. The maximum of photosensitivity corresponds to the high-energy part of the 7.6 eV band. The growth of TSL intensity is almost linear for the case of excitation through monochromatic light and growth with saturation in the case of excitation with white light. The efficiency of formation of TSL peaks increases with an increase of the temperature. The result was explained as multi-step process of photochemical dissociation and …
Luminescence of polymorph crystalline and glassy SiO2, GeO2: A short review
2009
Studies of SiO 2 and GeO 2 crystals with α-quartz and rutile structures were performed during last two decades. The goal of such studies was comparison of properties with those of glassy modifications of these crystals. Luminescence of oxygen deficient centers in these glassy materials was found to resemble the luminescence of the rutile-type modification rather than α-quartz modification. In α-quartz, similar luminescence centers appear after damaging irradiation by electron beam at low temperatures (<60 K) or at ambient temperatures after gamma or neutron irradiation.