Dynamics of Interface Instabilities and Nanostructure Formation on Si and SiGe Alloys

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This project addresses dynamics of film growth and surface and interface reactions on Si and SiGe; the approach encompasses interface chemistry, strain effects and surface and interface energetics. The primary objective of the research is to develop a fundamental understanding of the dynamics of interface instabilities for nanostructure formation on Si and SiGe alloys. In situ measurements will employ photo-electron emission microscopy (PEEM) with UV excitation from a free electron laser (UV-FEL). The research goals include: (1) Development of specific approaches to use the FEL PEEM system for in situ, real time measurements of the dynamics at Si and SiGe surfaces. The major advantage of the LTV-FEL PEEM system is that the high intensity FEL light can be wavelength tuned to the appropriate photo threshold to obtain image contrast of the desired surface. (2) Development of methods to prepare nanoscale silicide islands on Si, and the characterization of the electrical properties of the nanoscale islands using scanning probe techniques. The research will relate coalescence and ripening processes and shape transitions of the epitaxial islands. (3) Dynamics of liquid metal-Si (M-Si) micro-droplets on Si surfaces. The metals of Pd, Pt, Ni and Au all exhibit a deep eutectic in the M-Si binary phase diagram. Research will explore how interface chemical equilibrium affects the evolution of the surface microstructure under various conditions of metal deposition or evaporation, or Si deposition. (4) Dynamics and stability of metallic interfaces on SiGe. This research will involve in situ PEEM measurements of the dynamics of these instabilities. New approaches to avoid segregation effects are based on models of the processes. (5) Dynamics of strain relaxation and nanostructure formation in SiGe epitaxial layers on uniquely oriented Si. For epitaxial SiGe layers on Si, strain is relaxed through the formation of misfit dislocations and through the development of surface corrugations. This project will explore whether the strain relaxation processes are affected by the presence of substrate surfaces with different step and terrace structures. The research will also explore the use of surface morphology for nanostructure organization. %%% The project addresses basic research issues in a topical area of materials science with high technological relevance. An important feature of the program is the integration of research and education through the training of students in a fundamentally and technologically significant area. An integrated educational program has been developed that includes scientific research techniques, interdisciplinary research approaches, and laboratory safety, and involves graduate and undergraduate students from diverse backgrounds.***