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AbstractAbstract
[en] For the first time one has paid attention to the fact, that ion electron polarizability represents and important microscopic parameter which determines the properties of normal and superconducting states of the oxide high-temperature superconductors. It determines nonstoichiometry by oxygen and hole concentration in high-temperature oxides. The obtained results agree well with available experimental data
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Novyj mikroskopicheskij parametr vysokotemperaturnykh sverkhprovodnikov
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Sverkhprovodimost': Fizika, Khimiya, Tekhnika; ISSN 0131-5366; ; CODEN SFKTE6; v. 5(10); p. 1802-1810
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AbstractAbstract
[en] La2-xSrxCuO4 is a paradigmatic example to understand the physics of strongly correlated systems. The experimental results mainly from high energy electron spectroscopies have been utilized to pin point the electronic change that occurs when the system undergoes from an anti-ferromagnetic insulator to a metallic phase with a superconducting phase in between. (orig.)
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HRP-8: 8. international conference on hopping and related phenomena; Murcia (Spain); 7-10 Sep 1999; 12 refs.
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[en] We have investigated the effects of high energy nitrogen ion (N+) irradiated n-GaAs Schottky barrier diodes using deep level transient spectroscopy. The diodes have been irradiated (fluences of 1 x 1012 and 1 x 1013 cm-2) at 77 K. Three electron trap levels (labeled as En1, En2 and En3) are observed for the diodes irradiated with the fluence of 1 x 1012 cm2. Activation energies and capture cross-sections of the levels are calculated. The electron trap level En2 (691 meV) is attributed to NGa defects produced by the irradiation. Trap level and shallow level concentrations of the irradiated diodes are found to be decreased. It is due to trapping of charge carriers by the irradiation induced defects. Photo carrier life times of the control and irradiated samples have been measured using time resolved photoluminescence spectroscopy. After the irradiation, a decrease in the PL decay time of the sample has been observed
Source
ICACS20: 20. international conference on atomic collisions in solids; Orissa (India); 19-24 Jan 2003; S0168583X03017464; Copyright (c) 2003 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: Belarus
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Journal Article
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Nuclear Instruments and Methods in Physics Research. Section B, Beam Interactions with Materials and Atoms; ISSN 0168-583X; ; CODEN NIMBEU; v. 212(4); p. 496-500
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AbstractAbstract
[en] A systematic investigation has been carried out using core level X-ray photoelectron spectroscopy (XPS) in the Fe- and Ni-doped YBa2Cu3O7-y (YBCO) system by varying the concentration of Cu. The experimental spectra of Ba-3d, Ba-4d and Y-3d have been utilized to probe the dopant sites. This study indicates that Fe goes to Cu(1) site and Ni to both Cu(1) and Cu(2) sites. It appears that each metal substituent has a preference for a specific Cu site or combination of sites, which is consistent with the reports available in literature. The present work emphasizes that XPS can be a suitable tool to probe the dopant sites in two inequivalent local sites. (orig.)
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ICSSS '99: International conference on solid state spectroscopy; Schwaebisch Gmuend (Germany); 5-7 Sep 1999; 9 refs.
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[en] The films of polymethyl methacrylate/ polyvinyl chloride blends of different compositions have been prepared. They have been irradiated with a 28Si ion beam of 120 MeV in the fluence range of 1011-1013 ions/cm2. The infrared spectra of these samples have been recorded before and after irradiation and based on the spectral information, some structural changes in the films have been found
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S0168583X9900258X; Copyright (c) 1999 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
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Journal Article
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Nuclear Instruments and Methods in Physics Research. Section B, Beam Interactions with Materials and Atoms; ISSN 0168-583X; ; CODEN NIMBEU; v. 156(1-4); p. 195-200
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Chandra, Usha; Jan, J.C.; Chiou, J.W.; Asokan, K.; Pong, W.F., E-mail: chandrausha@hotmail.com2003
AbstractAbstract
[en] We report X-ray absorption near edge structure (XANES) spectra of La0.7-xCsxCa0.3MnO3 (x=0, 0.01, 0.05, 0.1) at the Mn, O K- and Mn L3,2-edges. In a stoichiometric compound, the substitution of Cs for La-site could drive a fraction of Mn ions to 5+ valency state. The experimental XANES spectra at Mn K-edge do not support such a proposal. To account this result, one needs to consider the effect of ionic radius of Cs. It is likely that both ionic radius of Cs and valency of Mn act in opposite directions. The XANES spectra both at O K-, and Mn L3,2-edges exhibit prominent changes due to Cs doping, such observed changes are explained by considering Mn 3d-O 2p hybridization and the crystal field effects of Mn ions
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S0168583X02014234; Copyright (c) 2002 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
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Nuclear Instruments and Methods in Physics Research. Section B, Beam Interactions with Materials and Atoms; ISSN 0168-583X; ; CODEN NIMBEU; v. 199(1-4); p. 185-189
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Asokan, K., E-mail: asokan@iuac.res.in
Proceedings of the international conference on swift heavy ions in materials engineering and characterization: book of abstracts2014
Proceedings of the international conference on swift heavy ions in materials engineering and characterization: book of abstracts2014
AbstractAbstract
[en] Inter-University Accelerator Centre serves as a user facility for Indian universities and institutes. It has been contributing significantly in planning and carrying out novel experiments using this centre. A selected number of exciting results obtained from ion beam experiments focussing on morphological, electronic, superconducting and magnetic properties of some novel materials are presented. First example is from the morphological studies on ZnO nanorods, wherein ion beam irradiation has been used as a tool to modify the hydrophobic surface to superhydrophobic surface. Large numbers of investigations are being carried out in the area of magnetic and superconducting materials. One example each was presented and showed that ion irradiation modifies the magnetically anisotropic system to isotropic system in cobalt ferrite and by careful and selective implantation of C ions in MgB_2, improves the superconducting properties especially J_C to almost 4 times. To understand the changes that are brought out by ion beams in the electronic structures of NiAl films, X-ray absorption and photoemission spectroscopy techniques have been used to establish that ion beam induces charge transfer
Source
Inter University Accelerator Centre, New Delhi (India); 208 p; 2014; p. 40; SHIMEC 2014: international conference on swift heavy ions in materials engineering and characterization; New Delhi (India); 14-17 Oct 2014
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Book
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AbstractAbstract
[en] Experimental results on the isotope effect in oxide superconductors may be understood based on the electronic structure of these materials. The La(M)-Cu-O (M=Sr or Ba) system has been considered as a typical example and an empirical explanation supported by high energy spectroscopic data is presented. (author). 18 refs., 4 figs
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ABSORPTION SPECTROSCOPY, BARIUM OXIDES, BINDING ENERGY, COPPER OXIDES, CUPRATES, DOPED MATERIALS, ELECTRONIC STRUCTURE, ENERGY-LOSS SPECTROSCOPY, FERMI LEVEL, HIGH-TC SUPERCONDUCTORS, ISOTOPE EFFECTS, LANTHANUM OXIDES, PHOTOELECTRON SPECTROSCOPY, STRONTIUM OXIDES, SUPERCONDUCTIVITY, TRANSITION TEMPERATURE
ALKALINE EARTH METAL COMPOUNDS, BARIUM COMPOUNDS, CHALCOGENIDES, COPPER COMPOUNDS, ELECTRIC CONDUCTIVITY, ELECTRICAL PROPERTIES, ELECTRON SPECTROSCOPY, ENERGY, ENERGY LEVELS, LANTHANUM COMPOUNDS, MATERIALS, OXIDES, OXYGEN COMPOUNDS, PHYSICAL PROPERTIES, RARE EARTH COMPOUNDS, SPECTROSCOPY, STRONTIUM COMPOUNDS, SUPERCONDUCTORS, THERMODYNAMIC PROPERTIES, TRANSITION ELEMENT COMPOUNDS
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Deepthy, A.; Rao, K. S. R. K.; Bhat, H. L.; Kumar, Ravi; Asokan, K.
Funding organisation: (United States)2001
Funding organisation: (United States)2001
AbstractAbstract
[en] Potassium titanyl phosphate single crystals were irradiated with 48 MeV lithium ions at fluences varying from 5 x 1012 to 1016ions/cm2. The defects created in the crystal have been characterized using x-ray rocking curve measurements, optical transmittance, and photoluminescence spectroscopy. From x-ray rocking curve studies, the full width at half maximum for the irradiated samples was observed to increase, indicating lattice strain caused by the energetic ions. Optical transparency of these samples was found to decrease upon irradiation. The irradiated samples exhibited a broadband luminescence in the 700 - 900 nm region, for fluences above 5x1013ions/cm2. The results indicate that ion-beam-induced optical effects in KTiOPO4 single crystals are very similar to the ones obtained for crystals with 'gray tracks, which are attributed to the electronic transitions in the Ti3+ levels. [copyright] 2001 American Institute of Physics
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Othernumber: JAPIAU000089000011006560000001; 050106JAP; The American Physical Society
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Journal Article
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Journal of Applied Physics; ISSN 0021-8979; ; v. 89(11); p. 6560-6562
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Jayavel, P.; Udhayasankar, M.; Kumar, J.; Asokan, K.; Kanjilal, D., E-mail: marsjk@hotmail.com1999
AbstractAbstract
[en] Au/n-GaAs Schottky Barrier Diodes (SBDs) have been fabricated on LEC grown silicon doped <1 0 0> GaAs single crystals. The SBDs were irradiated by 70 MeV high energy carbon ions with various ion fluences of 1x1011, 1x1012 and 1x1013 ions cm-2. Current-voltage (I-V) and capacitance-voltage (C-V) characteristics of unirradiated and irradiated diodes were analysed. The change in reverse leakage current increases with increasing ion fluence. This is due to the irradiation induced defects at the interface and its increase with the fluence. The diodes were annealed at different temperatures (473, 573 and 673 K) to study the effect of annealing. The rectifying behavior of the irradiated SBDs improves as the annealing temperature increases. But at 673 K, the diode behavior has been deteriorated irrespective of the fluences. Better enhancement in barrier height and also improvement in the ideality factor has been observed at the annealing temperature of 573 K. A decrease in the capacitance has been observed with increasing fluence. For the irradiated and annealed SBDs, the increase in capacitance has been observed. Scanning Electron Microscopic analysis was carried on the irradiated samples to delineate the projected range and to observe defects induced by high energy carbon irradiation
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S0168583X99002827; Copyright (c) 1999 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
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Nuclear Instruments and Methods in Physics Research. Section B, Beam Interactions with Materials and Atoms; ISSN 0168-583X; ; CODEN NIMBEU; v. 156(1-4); p. 110-115
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