Copyright © (2001) American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics
We present a straightforward and fast positron annihilation spectroscopy (PAS)
technique for measuring the two-to-three photon annihilation ratio of Ps (electronpositron)
atoms (3 lambda PAS), utilized here for the non-destructive characterization of
mesoporous (pore size > 1 nm) dielectric films. Examples are given for ~1 mu m-thick
foamed MSSQ films, produced by mixing MSSQ (0-90 wt. % fraction) with a sacrificial
foaming agent (porogen). Probing these films as a function of depth allows one to
monitor Ps escape from interconnected pores. This Ps escape data is, subsequently, used
to determine the threshold for pore interconnectivity to the film surface, which occurs
prior to critical percolation. A classical treatment of Ps diffusion is used to calculate the
open and closed porosity fractions as a function of the initial porogen load.
By: Mihail P. Petkov, Marc H. Weber, Kelvin G. Lynn, Kenneth P. Rodbell
Published in: Applied Physics Letters, volume 79, (no 23), pages 3884-6 in 2001
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