Optical differential reflectance spectroscopy on thin molecular films

Optical spectroscopy is a powerful tool to study in depth manifold physical processes occurring in molecular solids, at interfaces between molecules and substrates, and at interfaces between different molecular species. Apart from probing the optical interactions themselves, also structural information can be deduced due to the sensitive dependence of the optical properties of molecular assemblies on the respective structure. In our contribution we review the method Differential Reflectance Spectroscopy (DRS), with special emphasis on the interpretation of the spectral data and the extraction of the material's properties, i.e., the complex dielectric function. We further elucidate which physical effects can be investigated. For this purpose we assess recent progress of DRS experiments and explain several selected results achieved with this technique.