Do Interfacial Layers in Thin Films Act as an Independent Layer within Thin Films?

Abstract

The thermodynamic behavior of thin Poly(vinyl methyl ether) (PVME) films including the irreversible adsorbed layer on the substrate is investigated. In the first step, the growth kinetics of the adsorbed layer was studied combining a leaching technique and atomic force microscopy. Furthermore, it was shown that there is a critical initial film thickness for the formation of a surface-filling adsorbed layer. Additionally, spectroscopic ellipsometry measurements were carried out to investigate the influence of the adsorbed layer on the glass transition temperature of the thin films. For 30 nm films and films with lower thicknesses, the influence of the adsorbed layer percolates strongly to the bulk-like layer of the film. Finally, the molecular dynamics of the adsorbed layer was studied by broadband dielectric spectroscopy, employing a nanostructured-electrode system. One process was revealed, which was assigned either to molecular fluctuations taking place in the loosely bounded part of the adsorbed layer or to the desorption/adsorption of segments at the substrate.