Search results for "germani"
showing 10 items of 488 documents
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.
Comparison of &#x03B3; and &#x03B2;-ray irradiation effects in sol-gel Ge-doped SiO<inf>2</inf>
2009
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. 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, Germanium Lone Pair Center (GLPC) 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. In addition, it is found that both irradiations are able t…
Twofold coordinated Ge defects induced by gamma-ray irradiation in Ge-doped SiO2
2008
We report an experimental study by photoluminescence, optical absorption and Electron Paramagnetic Resonance measurements on the effects of exposure of Ge-doped amorphous SiO2 to gamma ray radiation at room temperature. We have evidenced that irradiation at doses of the order of 1 MGy is able to generate Ge-related defects, recognizable from their optical properties as twofold coordinated Ge centers. Until now, such centers, responsible for photosensitivity of Ge-doped SiO2, have been induced only in synthesis procedures of materials. The found result evidences a role played by gamma radiation in generating photosensitive defects and could furnish a novel basis for photosensitive pattern wr…
Study of the germanium luminescence in silica: from non-controlled impurity to germano-silicate core of telecommunication fiber preforms
2003
Abstract We have studed luminescence properties of doped silica with different concentrations of germanium. The basic luminescence parameters such as spectral dependencies, decay kinetics and polarization at different temperatures were measured. Three spectral ranges 3.5–5.5 eV(I), 5.5–7 eV(II), 7–8 eV(III) in the optical transparency range of silica could be chosen from these data. Range I possesses a weak variation of basic parameters of luminescence of the germanium related oxygen deficient center with the change of luminescence center concentration from extremely low in pure silica to the germano-silica core of optical telecommunication fiber preforms. The temperature dependence of lumi…
Lowering the radioactivity of the photomultiplier tubes for the XENON1T dark matter experiment
2015
The low-background, VUV-sensitive 3-inch diameter photomultiplier tube R11410 has been developed by Hamamatsu for dark matter direct detection experiments using liquid xenon as the target material. We present the results from the joint effort between the XENON collaboration and the Hamamatsu company to produce a highly radio-pure photosensor (version R11410-21) for the XENON1T dark matter experiment. After introducing the photosensor and its components, we show the methods and results of the radioactive contamination measurements of the individual materials employed in the photomultiplier production. We then discuss the adopted strategies to reduce the radioactivity of the various PMT versi…
Gamma Ray Spectrum from Thermal Neutron Capture on Gadolinium-157
2018
International audience; We have measured the |$\gamma$|-ray energy spectrum from the thermal neutron capture, |${}^{157}$|Gd|$(n,\gamma)$|, on an enriched |$^{157}$|Gd target (Gd|$_{2}$|O|$_{3}$|) in the energy range from 0.11 MeV up to about 8 MeV. The target was placed inside the germanium spectrometer of the ANNRI detector at J-PARC and exposed to a neutron beam from the Japan Spallation Neutron Source (JSNS). Radioactive sources (|$^{60}$|Co, |$^{137}$|Cs, and |$^{152}$|Eu) and the |$^{35}$|Cl(|$n$|,|$\gamma$|) reaction were used to determine the spectrometer‘s detection efficiency for |$\gamma$| rays at energies from 0.3 to 8.5 MeV. Using a Geant4-based Monte Carlo simulation of …