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S. Tanigawa - One of the best experts on this subject based on the ideXlab platform.

  • Positron Annihilation in Vitreous Silica Glasses
    Japanese Journal of Applied Physics, 1993
    Co-Authors: Akira Uedono, S. Tanigawa
    Abstract:

    The Annihilation characteristics of Positrons in vitreous silica glasses (v-SiO2) were studied by measurements of two-dimensional angular correlation of Positron Annihilation radiations and Positron lifetime spectra. From the measurements, it was found that Positrons and Positronium (Ps) atoms mainly annihilate from trapped states by vacancy-type defects in v-SiO2. For v-SiO2 specimens with cylindrical porous structures, Annihilations of Ps with anisotropic momentum distributions were observed. This fact was attributed to the momentum uncertainty due to localization of Ps in a finite dimension of pores. This investigation showed possibilities for the detection of microstructures in v-SiO2 by the Positron Annihilation technique.

  • Defects in semiconductors observed by Positron Annihilation
    Hyperfine Interactions, 1993
    Co-Authors: S. Tanigawa
    Abstract:

    The origin of the effect of defects on Positron Annihilation in semiconductors has been studied. The electron-Positron momentum densities in elemental semiconductors (Si and Ge), III-V compound semiconductors (GaAs, InP and GaSb), diamond and the proton irradiated Si were investigated by a full-scale use of the two-dimensional angular correlation of Positron Annihilation radiations (2D-ACAR). The obtained results showed, as a whole, good agreement with the electron momentum distribution of the fully occupied Jones zone with a small exception for the fact that the low density channels are running along the three principal axes. This anisotropy was strong in elemental semiconductors, while it was weakened in compound semiconductors. This anisotropy and its dependence on the material were found to be generally understood by the incorporation of crystal symmetry. The anisotropy will be discussed by group theory in conjunction to the effect of defects on Positron Annihilation.

  • Defects in vitreous SiO2 probed by Positron Annihilation
    Journal de Physique IV Colloque, 1993
    Co-Authors: A. Uedono, L. Wei, S. Tanigawa
    Abstract:

    Annihilation characteristics of Positrons in a single quartz crystal and vitreous silica glasses (v-SiO2) were studied by measurements of two-dimensional angular correlation of Positron Annihilation radiations. From the measurements, it was found that Positrons and Positronium (Ps) atoms mainly annihilate from trapped states by vacancy-type defects in the v-SiO2 specimen. For the v-SiO2 specimen with a cylindrical porous structure, the Annihilation of Ps with anisotropic momentum distributions was observed. This was attributed to the momentum uncertainty due to a localization of Ps in a finite dimension of pores. The present investigation showed possibilities for the detection of microstructures in v-SiO2 by the Positron Annihilation technique.

Kelvin G. Lynn - One of the best experts on this subject based on the ideXlab platform.

  • Applications of Positron Annihilation Spectroscopy
    Journal De Physique Iv, 1995
    Co-Authors: P. Asoka-kumar, Kelvin G. Lynn
    Abstract:

    We describe the application of Positron Annihilation Spectroscopy (PAS) to some selected technologically important systems. The method involves a nondestructive probe to detect low levels of open-volume defects. The discussion shows the application of PAS to a wide range of advanced material systems

  • Positron Annihilation at the Si/SiO2 interface
    Journal of Applied Physics, 1992
    Co-Authors: T. C. Leung, P. Asoka-kumar, Z. A. Weinberg, B. Nielsen, Gary W. Rubloff, Kelvin G. Lynn
    Abstract:

    Variable‐energy Positron Annihilation depth‐profiling has been applied to the study of the Si/SiO2 interface in Al‐gate metal‐oxide‐semiconductor (MOS) structures. For both n‐ and p‐type silicon under conditions of negative gate bias, the Positron Annihilation S‐factor characteristic of the interface (Sint) is substantially modified. Temperature and annealing behavior, combined with known MOS physics, suggest strongly that Sint depends directly on holes at interface states or traps at the Si/SiO2 interface.

  • Depth-profiled Positron Annihilation Spectroscopy of Thin Insulation Films
    New Directions in Antimatter Chemistry and Physics, 1
    Co-Authors: David W. Gidley, Kelvin G. Lynn, M. P. Petkov, M. H. Weber, J. N. Sun, A. F. Yee
    Abstract:

    The various techniques of Positron Annihilation spectroscopy (PAS) may be among the best for characterizing pore size, pore distribution and interconnectivity in amorphous thin films. In particular, PAS is becoming recognized as a practical characterization method for low-k dielectric films in microelectronic materials research. We expect this area of PAS research to experience a significant increase in activity in the next decade. Many obstacles to using low energy Positron beams to depth profile thin film insulators with Positron Annihilation spectroscopies (PAS) have recently been overcome.

D. C. Huang - One of the best experts on this subject based on the ideXlab platform.

A. Uedono - One of the best experts on this subject based on the ideXlab platform.

  • Positron Annihilation in electron irradiated Cz-Si
    Hyperfine Interactions, 1993
    Co-Authors: A. Uedono, Y. Ujihira, A. Ikari, H. Haga, O. Yoda
    Abstract:

    Defects in electron irradiated Cz-Si were studied by the Positron Annihilation technique. In order to know effects of the thermal history of crystals on the introduction of defects, the specimen was quenched from 1390°C to room temperature before irradiation. A clear correlation between results obtained by the Positron Annihilation experiments and those by infrared spectroscopy was established. From the isochronal annealing experiment, it was found that oxygen clusters were introduced by quenching treatments.

  • Defects in vitreous SiO2 probed by Positron Annihilation
    Journal de Physique IV Colloque, 1993
    Co-Authors: A. Uedono, L. Wei, S. Tanigawa
    Abstract:

    Annihilation characteristics of Positrons in a single quartz crystal and vitreous silica glasses (v-SiO2) were studied by measurements of two-dimensional angular correlation of Positron Annihilation radiations. From the measurements, it was found that Positrons and Positronium (Ps) atoms mainly annihilate from trapped states by vacancy-type defects in the v-SiO2 specimen. For the v-SiO2 specimen with a cylindrical porous structure, the Annihilation of Ps with anisotropic momentum distributions was observed. This was attributed to the momentum uncertainty due to a localization of Ps in a finite dimension of pores. The present investigation showed possibilities for the detection of microstructures in v-SiO2 by the Positron Annihilation technique.

A Sarkar - One of the best experts on this subject based on the ideXlab platform.

  • Probing Materials by Positron Annihilation Technique and Mossbauer Spectroscopy - Review
    Materials Science Forum, 2011
    Co-Authors: Mahuya Chakrabarti, S Chattopadhyay, A Sarkar, Dirtha Sanyal, Debnarayan Jana
    Abstract:

    Positron Annihilation technique is a well known technique to characterize the defects in a material. These defects can be identified by Positron Annihilation lifetime and coincidence Doppler broadening of Positron Annihilation radiation measurement. In this chapter we report the room temperature Positron Annihilation lifetime for single crystalline ZnO. From our study it is confirmed that the present crystal contains VZn–hydrogen complexes with low open volumes. Another important nuclear solid technique is the Mossbauer Spectroscopic technique which has been used to probe the local magnetic properties of a solid. Here we have summarized Mossbauer spectroscopic studies on ferrites.

  • defect dynamics in annealed zno by Positron Annihilation spectroscopy
    Journal of Applied Physics, 2005
    Co-Authors: Sreetama Dutta, Mahuya Chakrabarti, S Chattopadhyay, Debnarayan Jana, D Sanyal, A Sarkar
    Abstract:

    As-supplied polycrystalline ZnO samples (purity 99.9% from Sigma-Aldrich, Germany) have been annealed at different temperatures and subsequently characterized by Positron Annihilation spectroscopy, x-ray-diffraction (XRD) analysis, thermogravimetric analysis (TGA), and resistivity measurements. Positron Annihilation lifetime analysis and coincidence Doppler-broadened electron-Positron Annihilation γ-radiation (CDBEPAR) line-shape measurements have been employed at a time to identify the nature of defects in differently annealed ZnO materials. Annealing up to 300°C, an increase of defect lifetime (τ2) as well as shape parameter (S parameter) has been observed. Further annealing causes a large decrease of τ2 and S parameter. TGA study shows considerable mass loss from ZnO as the annealing temperature is increased above 300°C. This is possibly due to oxygen evaporation from the sample. The c-axis lattice parameter, extracted from the XRD spectra, shows an increase due to annealing above 600°C, which is a sig...