This project is concerned with the use of artificial nanostructures as a tool to study the growth, interface structure and stability of amorphous and crystalline semiconductors. The research will address structure, structural relaxation, atomic diffusion and crystallization of tetrahedrally-based amorphous semiconductor materials (amorphous silicon and related materials). In addition the growth and properties of amorphous silicon and related thin films with particular emphasis on the relationship between structure and electronic properties. The techniques to be utilized include: 1) Raman scattering (useful for the study of local bonding and order); 2) x-ray reflectivity (useful for the study of density, interface roughness and interdiffusion); 3) optical absorption and photoconductivity (sensitive to the electronic charge in the layers and interfaces). The analysis of the data from these different techniques requires different sets of assumptions about materials and their structure. Nanostructured semiconductor-based materials are important technologically for photoelectronic detectors and arrays, field effect display drivers, photovoltaic devices, optical modulation and non-linear optical devices as well as catalysts and catalyst supports for commercial reactions.