Epitaxial Growth of Uniaxially and Biaxially Mismatched Silicide Films on Silicon

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The goal of this project is greater understanding of epitaxial growth of strained layers when the mismatch between overlayer and substrate is anisotropic. Focus is on the epitaxial growth of rare earth silicides on the silicon (001) surface. Rare earth silicides are ideal test systems, since they provide a wide range of both anisotropic and isotropic mismatches with respect to the Si(001) substrate. The structural and compositional similarity between the silicide phases formed, and the ability to vary the silicide lattice constants by judicious choice of rare earth metal, provide a unique opportunity to study growth behavior as a function of both biaxial and uniaxial lattice mismatch in epitaxially grown films, with other parameters such as surface energy held constant. Another feature in these systems is the fact that silicide nanowires form in the initial stages of growth. Therefore, the research will also test the relative importance of different mechanisms that have been proposed for nanowire formation in diverse materials systems. These issues have rele-vance to the general understanding of strained layer epitaxy, and the specific extension of this understanding to cases where the strain is anisotropic. The results of this research may also help develop ways of growing both better quality nanowires, and better quality metal silicide films in general. %%% This project addresses basic research issues in a topical area of materials science with significant technological relevance. An important feature of the project is the training of graduate students as researchers with skills in several different atomic resolution characterization techniques. Much of the data produced will be visual in nature, which makes it particularly suitable for presentation to a wide range of age groups with a general interest in science and engineering. Material will be developed and integrated into outreach and educational activities in a variety of venues, with the goal of informing the widest possible public about basic research in materials and its relevance to both scientific knowledge and future technological applications.***