Study of diffusion in films on planar substrates by ellipsometry

Abstract

A theory of diffusion in films of variable thickness is developed. Approximations for the short-time and long-time dependences of solvent concentration in the film are derived. Diffusion in thin films has been investigated by ellipsometry. The diffusion coefficients for different temperatures were calculated using asymptotic formulae and the time dependences of solvent concentration in the polymer films. The apparent activation energies of diffusion were estimated.