Positron Implantation and Transmission Experiments on Free-Standing Nanometric Polymer Films

Abstract

Positron transmission experiments were performed on free-standing poly(methyl-methacrylate) (PMMA) and polystyrene (PS) films of nanometric thicknesses made by spin coating. The power_law equation z1/2(E) )=(α/ρ)En was determined from the measurements of the S-parameter as a function of the positron implantation energy. These transmission experiments indicate that n = 1.90(±0.08) and α = 1.33(±0.10) μg cm-2 which deviates from the values found by Algers et al. (n = 1.71(±0.05) and α = 2.8(±0.2) μg cm-2) and the commonly used parameters (n = 1.6 and α = 4.0 μg cm-2).