Ortho-Positronium Reemission Yield and Energy in Surfactant-Templated Mesoporous Silica Films

Abstract:

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Positron annihilation gamma energy distribution, lifetime spectroscopy and time-of-flight method were used to study surfactant-templated mesoporous silica films deposited on glass. The lifetime depth profiling was correlated to Doppler broadening and 3γ annihilation fraction measurements to determine the annihilation characteristics inside the films. A set of consistent fingerprints for positronium annihilation, o-Ps reemission into vacuum, and pore size was directly determined. The lifetime measurements were performed in reflection mode with a specially designed lifetime spectrometer mounted on a slow positron beam system. The intensity of the 142 ns vacuum lifetime component was recorded as a function of the energy of the positron beam. In a film with high porosity a reemission efficiency of as high as 40 % was found at low positron energy. Positron lifetime in samples capped by a thin silica layer was used to determine the pore size. The energy of the reemitted o-Ps fraction was measured by a time-of-flight detector, mounted on the same system, allowing determination of both o-Ps re-emission efficiency and energy in the same sample. We demonstrate the potential of the simultaneous use of different positron annihilation techniques in the study of thin porous films.

Info:

Periodical:

Edited by:

S. J. Wang, Z. Q. Chen, B. Wang and Y. C. Jean

Pages:

30-33

DOI:

10.4028/www.scientific.net/MSF.607.30

Citation:

L. Lizkay et al., "Ortho-Positronium Reemission Yield and Energy in Surfactant-Templated Mesoporous Silica Films", Materials Science Forum, Vol. 607, pp. 30-33, 2009

Online since:

November 2008

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$35.00

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