Determination of pore-size distribution in low-dielectric thin films

Positronium annihilation lifetime spectroscopy is used to determine the por e-size distribution in low-dielectric thin films of mesoporous methylsilses quioxane. A physical model of positronium trapping and annihilating in isol ated pores is presented. The systematic dependence of the deduced pore-size distribution on pore shape/dimensionality and sample temperature is predic ted using a simple quantum mechanical calculation of positronium annihilati on in a rectangular pore. A comparison with an electron microscope image is presented. (C) 2000 American Institute of Physics. [S0003-6951(00)03810-9] .