摘要:

H+-implantation in Bi4Ge3O12(BGO) crystals causes some interesting effects, such as radiation damage, optical absorption and optical waveguide formation in the near-surface region of the crystals. There are similarities between the refractive index profiles of the H+and He+implanted waveguides in that the index is enhanced throughout the guiding layer. The maximum increase in index was ∼0.7% after an implant of 8 × 1016H+ions/cm2at 0.4 MeV. The colour of the BGO samples after H+-implantation changed to brown. Whilst it can be assumed that ion beam-induced decomposition may happen during ion implantation, this is probably only a small factor in the colouration and index change since it is only apparent for the H+implants. a4

ISSN:1042-0150    

DOI:10.1080/10420159308219892

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

ISSN:1042-0150    

DOI:10.1080/10420159308219893

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The phenomena occuring after keV ion bombardment of condensed gas targets are modelled with the help of the nonlinear Boltzmann equation. It is solved using Monte Carlo solution techniques adapted from gas phase studies. Sputtered particle energy distributions show an enhancement over the predictions of linear cascade theory at low emission energy. The sputter yield displays a quadratic dependence on the stopping power of the bombarding ion. It is concluded that while it is possible in principle to study the development of an elastic collision spike, and its thermalization, via the nonlinear Boltzmann equation, the exclusion of binding effects, and in particular of a realistic modelling of the surface barrier, limits its validity severely.

ISSN:1042-0150    

DOI:10.1080/10420159308219894

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Monte Carlo simulation is used to study defect production during ion bombardment. The systems of 300 keV Ni+→ Ni and 1 MeV H+→ Ni are studied as representatives of heavy-ion and light-ion bombardment, respectively. The number ofisolateddefects—vacancies and interstitials—is determined which have no recombination partner within a distance of one recombination radiusrrec. Our simulations predict a fraction of freely-migrating defects of 1.5% for 300 keV Ni+bombardment, and 20% for 1 MeV H+bombardment, if a common value ofrrec≌ 10 Å is employed. This is in good agreement with measured data.

ISSN:1042-0150    

DOI:10.1080/10420159308219895

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Structural degradation in calcium-A zeolites (Ca-A) subjected to electron beam irradiation was studied in a Transmission Electron Microscope. Several structural changes observed are reported and their possible nature, under the light of the electron beam-matter interaction, is discussed as well.

ISSN:1042-0150    

DOI:10.1080/10420159308219896

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

X-ray irradiation of germanosilicate optical fibres simultaneously produces signals from both the core and substrate and so the radioluminescence spectra record the defect structure of both regions. The data provide evidence for the presence of dopants and trace impurities, as well as intrinsic defects formed by thermal and radiation processing. Examples of the changes in spectra or luminescence sensitivity with radiation dose, the influence of fibre pulling conditions and post irradiation heating are noted. The temperature dependence of the radioluminescence is reported. Whilst most of the intrinsic defects produce broad emission bands, rare earth dopants show line features. However, line features have also been noted for Al doped fibres. Such studies of fibre luminescence offer a sensitive monitor of changes in the structure of the glass network.

ISSN:1042-0150    

DOI:10.1080/10420159308219897

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Thermoluminescence glow peaks and emission spectra data are reported for undoped and Al doped GeO2tetragonal crystals over the temperature range from 45 to 700 K. For the pure crystal the emission peaks near 475 nm below 150 K but at higher temperatures it is characterised by red emission near 720 nm. For samples irradiated at room temperature the Al:GeO2shows 575 nm emission below 75°C but primarily red signals at higher temperature. Separation and activation energies of component glow peaks are recorded. The thermoluminescence spectra alter after repeated irradiation and measurement. Further, comparisons are made between the thermoluminescence spectra and those obtained during X-ray or electron beam irradiation. The cathodoluminescence spectra differ at 300 K with a dominant 575 nm peak for the Al:GeO2and bands near 300, 400, 540, 575 and 720 nm for the pure sample. Below room temperature there are significant differences although both show extra bands near 75 to 100 K peaked at 310 and 370 nm. Models of the role of the Al impurity are discussed.

ISSN:1042-0150    

DOI:10.1080/10420159308219898

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

A simple model is proposed to explain the enhanced diffusion of antimony impurities implanted at high temperatures into silicon, as measured by Gamoet al. It turns out that the concentration profiles can be calculated using a system of reaction-diffusion equations describing the diffusion and decay of impurity-vacancy pairs created during the implantation process. A good agreement with experiment has been obtained.

ISSN:1042-0150    

DOI:10.1080/10420159308219899

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

In the present investigation the excitation and fluorescence spectra and lifetimes of Mn2+ions in calcium chloride, for various manganese concentrations and sample temperatures have been studied for the first time. The fluorescence spectrum consists of an asymmetric broad band, which upon lowering the sample temperature, shifts its maximum from 580 nm at 300 K to 596 nm at 11 K. This luminescence band was associated with the4Tlg(4G)→6Alg(6S) spin-forbidden transition in the manganese ions occupying Ca-sites in the lattice of CaCl2. The excitation spectrum of the Mn2+fluorescence revealed the features of manganese ions in octahedral coordination and consisted of nine excitation peaks which were associated with Mn2+-crystal-field-sensitive transitions. A crystal field analysis of the wavelength positions of these transitions by means of the model developed by Curieet al.allowed us to determine the magnitude of the cubic field splitting 10Dq, the reduced Racah parameterB', the Koide-Pryce covalency parameter ϵ and the spin transfer coefficientsf[sgrave]andfσ. From the measurement of the temperature dependence of the Mn2+fluorescence lifetime, we have also obtained information about the different mechanisms which are involved in the relaxation of excited Mn2+ions in this host crystal in the temperature range (11–300 K).

ISSN:1042-0150    

DOI:10.1080/10420159308219900

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Photodecomposition of pure and doped KI powders [KI:Cs, KI:Rb, KI:Na, KI:Cl, KI:Br, KI:RbCl, KI:RbBr, KI:NaCl, impurity concentration 500 ppm] to produce free I2molecules during gamma irradiation is studied quantitatively by findingGvalues with the help of absorption measurements and calibration plots. Absorption measurements are made on solutions of irradiated powders after being dissolved in distilled-water.G-value or radiation chemical yield is the fundamental quantitative characteristic of radiation induced chemical change and it is defined as number of ions, free radicals, atoms or molecules formed or destroyed when the system has absorbed 100eV of energy.G(I2) (rate of formation of free I2molecules) for anion doped KI powder [KI:Cl, KI:Br] is more compared to pure KI powder.G(I2) for cation doped KI powder [KI:Rb, KI:Cs, KI:Na] is less compared to pure KI powder. Comparatively,G(I2) values obtained are small in KI:RbCl, KI:RbBr and KI:NaCl where both cation and anion are different from the host. These results are explained on the basis of misfit between impurity ions and host ions (difference between ionic radii of impurity ions and host ions) As misfit increases,G(I2) increases in cation doped powders where as in anion doped powders,G(I2) increases with the decrease in misfit.

ISSN:1042-0150    

DOI:10.1080/10420159308219901

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor