We present a straightforward and fast positron annihilation spectroscopy (PAS) technique for measuring the 2 to 3 photon annihilation ratio of Ps (electron-positron) atoms (3γ PAS), utilized here for the nondestructive characterization of mesoporous (pore size >1 nm) dielectric films. Examples are given for ∼1-μm-thick foamed methyl-silsesquioxane (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 and to determine the threshold for pore interconnectivity to the film surface. A classical treatment of Ps diffusion is used to calculate the open and closed porosity fractions as a function of the initial porogen load.

Topics
Positron annihilation spectroscopy, Surfactants, Thin films, Electron positron interactions
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