摘要:

First results from a series of experiments aimed at the study of the interaction of slow very highly charged ions with conductor and insulator surfaces are reported. Charge state dependences of secondary electron, x-ray and secondary ion emission are measured. In addition, microscopic studies are performed using an ‘Atomic Force Microscope’ to investigate surface defects, produced through the stored electrostatic potential of the incident ion. The ions that have been used for these studies range from O7+to Th80+, with low kinetic energies (generally 1–3 keV/amu). Overall, enhancement of the low energy secondary electron, sputter ion and photon emission are observed with increasing charge states. Saturation in the electron emission yield at very low velocities confirm present models for image charge acceleration effects. X-ray emission spectra are found to be consistent with the formation of so called ‘hollow’ atoms near the surface during the neutralization processes. The microscopic studies reveal interesting nano-size surface defects caused by the incidence of individual highly charged ions.

ISSN:1042-0150    

DOI:10.1080/10420159308220308

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The effect of keV ion irradiation on the electronic structure of highly oriented pyrolytic graphite has been investigated by means of electronic spectroscopies. Samples were irradiated by a 0.5 keV Ar+beam with fluences from 3 × 1014up to 3 × 1015ions/cm2. In order to investigate the relationship between initial (crystalline) and final (amorphous) structure in ion beam processing, we have compared the electronic states of graphite with those of damaged diamond and polystyrene. Results indicate that the process of amorphization by ion beam is very fast and it stabilizes after a dose corresponding to about one atomic monolayer, producing the same type of amorphous carbon regardless of the virgin material.

ISSN:1042-0150    

DOI:10.1080/10420159308220309

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

X-ray energy spectra induced by 1 MeV protons and the energy spectra of the backscattered protons have been examined in the <100> and <110> directions of Ni crystals containing 1 at.% Si. The channeling method was used to investigate interactions between the radiation-induced defects and the silicon atoms. From the measured minimum yields and from the shape of the angular scans the fraction of silicon atoms is determined, which are displaced into the <100> and <110> channels due to proton or helium irradiations and subsequent annealing treatments. In undamaged crystals about 98 % of the silicon atoms are on normal lattice sites. After irradiation a dose dependent fraction of the silicon atoms is displaced 0.05 nm away from the substitutional position indicating the formation of a mixed dumbbell consisting of one selfinterstitial atom and one silicon atom. However, the experimental data can also be interpreted by the assumption of a NiSi2complex, in which the silicon atoms are displaced 0.08 nm from the lattice site. Subsequent annealing from 50 K to 160 K does not change the configuration and the concentration of the silicon complexes. At room temperature the silicon atoms in the complex are positioned 0.04 nm from the lattice position. The silicon complexes were totally am ihilated at 400 K.

ISSN:1042-0150    

DOI:10.1080/10420159308220310

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Chromatographic analyses of solvent extracts from graphite bombarded with 130MeV/amu161Dy22+ions, and polyimide (kapton) bombarded with 5 MeV6Li1+ions, give clear evidence for the in situ synthesis of buckminsterfullerene -C60. The role played by the production of highly confined, dense assemblies of energetic electrons in this phase change is discussed.

ISSN:1042-0150    

DOI:10.1080/10420159308220311

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Three grades of Talc, Mg3[Si4O10](OH)2, collected from Kurnool district of Andhra Pradesh, India have been investigated by spectrochemical analysis, Optical and EPR spectroscopy. All these samples contain iron as major impurity and trace amounts of Al, Ca, Cr, Cu, Mn and Ni. The Optical absorption spectrum of the high grade Talc sample exhibit six bands at 29403, 26308, 24993, 22720, 20613 and 17090 cm−1, ascribed to Fe3+impurity, substituted for Mg ion. Low grade Talcs show edge absorption at 27500 and 22750 cm−1, due to higher content of iron. The crystal field parameters evaluated areB= 700,C= 2800 andDq= 700cm−1. In addition, the presence of Fe3+and Mn2+impurities have been confirmed by EPR spectroscopy. Heating the samples to 850°C in steps yielded spectra corresponding to stabilization of iron centres only, at the expense of Mn2+ones.

ISSN:1042-0150    

DOI:10.1080/10420159308220312

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

LiNaSO4: Eu is a recently discovered thermoluminescence dosimetry (TLD) phosphor which is more sensitive than the widely used CaSO4:Dy. In this paper results are reported on TL glow curves, TL emission spectra and PL photoluminescence. These measurements help to understand the role of impurity and the mechanism of thermoluminescence in this phosphor.

ISSN:1042-0150    

DOI:10.1080/10420159308220313

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Thermodynamical stability of defect drops (clusters) in semiconductors is shown. Composition and temperature effects upon the equilibrium size of the drops are studied. A possibility of point defects clusterization in radiation fields is shown. The proposed model is applied to describe the limit parameters of electron-irradiated A3B5semiconductors.

ISSN:1042-0150    

DOI:10.1080/10420159308220314

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:CI, KI:Br, KI:RbCl, KI:RbBr, KI:NaCl, impurity concentration 500 p.p.m.] to produce free I2molecules during gamma irradiation is studied quantitatively by finding G values 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 100 eV of energy. G(I2) {Rate of formation of free I2molecules} for anion doped KI powder [KI:CI, 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:10.1080/10420159308220315

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The effect of thermal neutron on the high temperature phase in nonstoichiometric (Li1−xLx)2SO4system was studied in the temperature range 600 up to 900 K. The critical parameter for the excess of specific heat is estimated and is found in the range 0.08–0.17. It was found that the critical parameter depends on both stoichiometric ratio and the neutron integrated fluences.

ISSN:1042-0150    

DOI:10.1080/10420159308220316

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Zirconia was cold-pressed into pellets. Ten groups of pellets were sintered respectively at 10 different maximum sintering temperatures. Thermoluminescent (TL) responses of these pellets after ultraviolet (u.v.) irradiation were tested. Surface morphologies and crystalline structures of these pellets were investigated by a scanning electron microscope and an X-ray diffractometer respectively. Combining the results of TL response, surface morphology and crystalline structure of these pellets, we conclude that the TL response of ZrO2is closely related to the degree of crystallization of the monoclinic ZrO2, and the charge trapping center corresponding to the 235°C TL peak could be constructed from the complex crystal plane of 2 monoclinic crystal planes of (122) and (220).

ISSN:1042-0150    

DOI:10.1080/10420159308220317

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor