Optical properties, electronic structure and London dispersion interactions for nanostructured interfacial and surficial films

Nanostructured amorphous films exhibit complex thermodynamic and kinetic behavior. To understand the structure and properties of nanostructured amorphous films in silicon based ceramics (Si3N4, SiC, Si) and in SrTiO3 ceramics, we have focused on experimental studies to determine the interband electronic structure and optical properties. We use vacuum ultraviolet spectroscopy for bulk materials, and valence electron energy loss spectroscopy (VEELS) in either transmission mode in the transmission electron microscope for interfacial films, and are developing VEELS in reflection mode for surficial films. These experimental data are quantitatively analyzed using Kramers–Kronig analysis to determine the complex optical properties of the constituent materials. This interband electronic structure information is the fundamental input to determine from Lifshitz theory the London dispersion interaction in these low-dimensional systems. We present interband transition strengths of AlPO4, SiO2 and rare-earth doped MgSiON glasses, and also of SiC and SrTiO3 and their grain boundaries. We use a new multilayer approach to produce graded interface models for the London dispersion interaction in complex nanostructured interfacial and surficial films.