Langmuir-Blodgett films were studied using a variable energy slow-positron
beam. We measured the energy spectra of positron annihilation radiation for
Cd and Mg eicosanoid films and obtained the V- and S-parameters as a funct
ion of the incident positron energy, E. In the V-E curves of Cd eicosanoid
films, there were dips at the positron energy whose mean implantation depth
corresponding to the first and second Cd2+ layers from the surface. These
dips are interpreted as the result of inhibition of Ps formation by the Cd2
+ ions. The S-parameter was found to be sensitive to chemical composition o
f the film and also to possible structural change due to heat treatment. Ou
r results suggest that positron beams provide valuable information about th
e microstructure of the Langmuir-Biodgett films. (C) 2000 Elsevier Science
Ltd. All rights reserved.