Boundary Influence on Permittivity in Molecular Films

A microscopic theory of optical properties of thin molecular films, i.e. quasi 2D systems bounded by two surfaces parallel to XY planes was formulated. Harmonic exciton states were calculated using the method of two-time, retarded, temperature dependent Green's functions. It was shown that two types of excitations can occur: bulk and surface exciton states. Analysis of the optical properties (i.e. dielectrical permittivity) of these crystalline systems for low exciton concentration shows that the permittivity strongly depends on boundary parameters and the thickness of the film. Influences of boundary conditions on optical characteristics of these nanostructures were especially analyzed.