Ultrathin Film Amorphous and Nanocrystalline Semiconductors - Structure, Stability and Electronic Properties

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They will investigate structure, structural relaxation, atomic interdiffusion and crystallization of ultrathin (1-20nm) amorphous silicon and germanium semiconductor films by applying vibrational and optical spectroscopies to amorphous superlattice structures. They will also investigate size and interface effects in nanocrystalline (20nm crystallites) materials formed by annealing or otherwise treating amorphous superlattice structures. Research efforts will include: 1) Development and application of vibrational Raman scattering as a probe of amorphous network strain (i.e. - bond distortions) and compositional mixing at and near amorphous interfaces. 2) Application and analysis of optical techniques including optical absorption, electromodulation (absorption, reflection, luminescence) and Raman scattering to study the formation and growth of crystallites in ultrathin films. 3) Application of Raman and optical techniques to study atomic diffusion in amorphous and nanocrystalline solids. 4) Development and application of optical and optical modulation techniques to study quantum size effects, interface effects and the breakdown of crystal momentum selection rules in nanocrystals with well defined dimensions from 2nm to 20nm. Nanostructured thin film materials will have a direct impact on the ability to develop amorphous thin films for large area applications such as photo- electronic detectors and arrays, field-effect display drivers and photovoltaic devices. Increased understanding of microscopic relaxation, diffusion and crystallization processes will have implications for the development of low temperature processing technologies for three-dimensional integrated circuits, high temperature semiconductors and non-linear optical components.