Radiation-induced Defects in Nonradioactive Natural Minerals: Mineralogical and Environmental Significance

ABSTRACTNatural short-lived radionuclides generate electronic defects in minerals, such as trapped electrons and positive holes, often associated with element impurities, which act as final traps over geological periods. Two main examples will be illustrated. The first example will concern the point defects, which are observed in clay minerals. The high specific surface area makes clay minerals sensitive to the geochemical radiation background and provides a record of the past occurrence of radionuclides in geological systems. In kaolinite, three types of hole-centers are trapped by oxygen atoms linked to Si- or Al-sites. An experimental dosimetry gives the paleodose, which can be used either to assess mean past U-concentration or for kaolinite dating, depending on the available geochemical parameters. The detection of past migrations of radioelements in natural analogues may be used in the safety assessment of radioactive waste disposals. The second example will concern the role of mineral impurities in defect formation and stabilization. Natural fluorites (CaF2) exhibit hole-and electron-centers trapped on several rare earths and oxygen impurities, often present at the ppm level, which are responsible for the wide range of coloration observed in natural fluorites. Ca colloids may form under severe irradiation and give rise to a characteristic absorption. The thermal stability of radiation-induced defects gives constraints on the evolution of fluorites as a function of temperature and time. Other minerals, such as apatite, confirm the importance of impurities in stabilizing radiation-induced defects over geological periods.

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Xenon ion irradiation of superconducting YBa2Cu3O7 thin films

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100173595 ◽

1990 ◽

Vol 48 (4) ◽

pp. 92-93

Author(s):

H. Watanabe ◽

B. Kabius ◽

B. Roas ◽

K. Urban

Keyword(s):

Defect Formation ◽

Ion Irradiation ◽

High Resolution Electron Microscopy ◽

Structural Disorder ◽

Flux Lines ◽

Pinning Effect ◽

Magnetic Flux Lines ◽

Resolution Electron ◽

Radiation Induced ◽

Induced Defects

Recently it was reported that the critical current density(Jc) of YBa2Cu2O7, in the presence of magnetic field, is enhanced by ion irradiation. The enhancement is thought to be due to the pinning of the magnetic flux lines by radiation-induced defects or by structural disorder. The aim of the present study was to understand the fundamental mechanisms of the defect formation in association with the pinning effect in YBa2Cu3O7 by means of high-resolution electron microscopy(HRTEM).The YBa2Cu3O7 specimens were prepared by laser ablation in an insitu process. During deposition, a substrate temperature and oxygen atmosphere were kept at about 1073 K and 0.4 mbar, respectively. In this way high quality epitaxially films can be obtained with the caxis parallel to the <100 > SrTiO3 substrate normal. The specimens were irradiated at a temperature of 77 K with 173 MeV Xe ions up to a dose of 3.0 × 1016 m−2.

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An Alternative Model for the Kinetics of Light-Induced Defects in A-Si:H

MRS Proceedings ◽

10.1557/proc-219-15 ◽

1991 ◽

Vol 219 ◽

Cited By ~ 4

Author(s):

Paulo V. Santos ◽

W. B. Jackson ◽

R. A. Street

Keyword(s):

Time Dependence ◽

Valence Band ◽

Defect Formation ◽

Defect Density ◽

Generation Rate ◽

Band Tail ◽

Defect Generation ◽

Wide Range ◽

Induced Defects ◽

Kinetics Of

ABSTRACTThe kinetics of light-induced defect generation in a-Si:H was investigated over a wide range of illumination intensities and temperatures. The defect density around 1016cm-3 exhibits a power-law time dependence Ns ∼ G2εfε with ε = 0.2 to 0.3, where G is the photo-carrier generation rate. A model for the kinetics of defect generation is proposed based on the existence of an exponential distribution of defect formation energies in the amorphous network, associated with the valence band tail states. The model reproduces the observed time dependence of the defect density with an exponent e determined by the exponential width of the valence band tail. The temperature dependence of the defect generation rate is well-reproduced by the model, which provides a connection between the Stabler-Wronski effect and the weak-bond model.

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Electrophysical and Optical Properties of 4H-SiC Irradiated with Xe Ions

Materials Science Forum ◽

10.4028/www.scientific.net/msf.740-742.625 ◽

2013 ◽

Vol 740-742 ◽

pp. 625-628

Author(s):

N. Chuchvaga ◽

E. Bogdanova ◽

A. Strelchuk ◽

Evgenia V. Kalinina ◽

D.B. Shustov ◽

...

Keyword(s):

High Energy ◽

Partial Recovery ◽

Electrical Characteristics ◽

Stopping Distance ◽

Wide Range ◽

Order Of Magnitude ◽

Radiation Induced ◽

Temperature Radiation ◽

Induced Defects ◽

Partial Annealing

A comparative research of the cathodoluminescence and electrical characteristics of the samples 4H-SiC irradiated with high energy Xe ions (167 MeV) in wide range fluencies 4x109 –1x1011 cm-2 at temperatures 250C and 5000C are presented. After irradiation these samples were thermal annealed at 5000C for 30 min. Far-action effect at a depth of more than one order of magnitude of stopping distance was observed under Xe ions irradiation in 4H-SiC. An increase of the ion Xe fluencies increased the concentration of radiation-induced defects that resulted in rise of the compensation effect of conductivity in samples. Irradiation of 4H-SiC by Xe ions at 5000C was accompanied with "dynamic annealing" some low-temperature radiation-induced defects, which led to a partial recovery of the electrical characteristics of devices. The thermal annealing of irradiated samples led to additional partial annealing of radiation defects, which increases the radiation resource of devices based on 4H-SiC.

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Radiation-induced defects in clay minerals: A review

Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms ◽

10.1016/j.nimb.2011.12.044 ◽

2012 ◽

Vol 277 ◽

pp. 112-120 ◽

Cited By ~ 23

Author(s):

Th. Allard ◽

E. Balan ◽

G. Calas ◽

C. Fourdrin ◽

E. Morichon ◽

...

Keyword(s):

Clay Minerals ◽

Radiation Induced ◽

Induced Defects

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Radiation-Induced Defects in Si after High Dose Proton Irradiation

Defect and Diffusion Forum ◽

10.4028/www.scientific.net/ddf.373.209 ◽

2017 ◽

Vol 373 ◽

pp. 209-212 ◽

Cited By ~ 2

Author(s):

Yurii V. Funtikov ◽

Leonid Yu. Dubov ◽

Yurii V. Shtotsky ◽

Sergey V. Stepanov

Keyword(s):

Bragg Peak ◽

Proton Irradiation ◽

Defect Formation ◽

High Energy ◽

High Dose ◽

Number Density ◽

High Energy Proton ◽

Energy Proton ◽

Radiation Induced ◽

Induced Defects

Experiments on investigation of the radiation defects produced as a result of high energy proton irradiation of single crystal Si wafers are carried out. Parameters of the proton irradiation facility are presented. It is shown that the most efficient radiation defect formation correlates with the position of the Bragg peak of ionization losses. LT spectra were measured just after irradiation and then after keeping Si samples during 3 months of at room T. We did not observe any variation of the number density of the defects, except for the 7th wafer, where most part of protons was stopped. An efficient annealing of the vacancy-type defects starts at temperatures slightly lower than 100 °C (during 10 min). Annealing at about 700 °C leads to recovering of the monoexponrntial shape of the LT spectra.

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Tracing past migrations of uranium in Paleoproterozoic basins: New insights from radiation-induced defects in clay minerals

Geology ◽

10.1130/g31453.1 ◽

2010 ◽

Vol 38 (11) ◽

pp. 983-986 ◽

Cited By ~ 12

Author(s):

E. Morichon ◽

D. Beaufort ◽

T. Allard ◽

D. Quirt

Keyword(s):

Clay Minerals ◽

Radiation Induced ◽

Induced Defects

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EPR Study of Paramagnetic Defects in Clay Minerals

Mineralogia ◽

10.2478/v10002-007-0021-x ◽

2007 ◽

Vol 38 (2) ◽

pp. 125-138

Author(s):

Joanna Babińska ◽

Krystyna Dyrek ◽

Piotr Wyszomirski

Keyword(s):

Clay Minerals ◽

Metal Ion ◽

Electron Paramagnetic Resonance Spectroscopy ◽

Resonance Spectroscopy ◽

Radioactive Elements ◽

Paramagnetic Resonance ◽

Radiation Induced ◽

Epr Signal ◽

Induced Defects ◽

Electron Paramagnetic

EPR Study of Paramagnetic Defects in Clay MineralsRadiation induced defects (RID-s) and transition metal ion impurities were revealed by EPR (Electron Paramagnetic Resonance) spectroscopy in kaolinites from a number of Polish deposits. Arelationship between the intensity of the EPR signals of the RID-s and quantity of radioactive elements was defined in these minerals. In one of the deposits of kaolinites (Wyszonowice) the EPR signal intensity depends on grain size. Other clay minerals studied (illites, montmorillonites) only show weak signals of the RID type.

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Colloidal systems in soils

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100168050 ◽

1994 ◽

Vol 52 ◽

pp. 64-65

Author(s):

J. Thieme ◽

J. Niemeyer ◽

P. Guttman

Keyword(s):

Clay Minerals ◽

Polymeric Materials ◽

Spatial Arrangement ◽

High Specific Surface Area ◽

Turnover Rates ◽

Colloidal Systems ◽

Chemical Conditions ◽

Aggregation Phenomena ◽

Iron And Manganese ◽

Soil Colloids

In soil science the fraction of colloids in soils is understood as particles with diameters smaller than 2μm. Clay minerals, aquoxides of iron and manganese, humic substances, and other polymeric materials are found in this fraction. The spatial arrangement (microstructure) is controlled by the substantial structure of the colloids, by the chemical composition of the soil solution, and by thesoil biota. This microstructure determines among other things the diffusive mass flow within the soils and as a result the availability of substances for chemical and microbiological reactions. The turnover of nutrients, the adsorption of toxicants and the weathering of soil clay minerals are examples of these surface mediated reactions. Due to their high specific surface area, the soil colloids are the most reactive species in this respect. Under the chemical conditions in soils, these minerals are associated in larger aggregates. The accessibility of reactive sites for these reactions on the surface of the colloids is reduced by this aggregation. To determine the turnover rates of chemicals within these aggregates it is highly desirable to visualize directly these aggregation phenomena.

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