Epitaxial Grain Growth in Metallic Thin Films

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9408201 Thompson The goal of this study is quantitative understanding of the origins and evolution of texture during grain growth in thin films, and the ability to accurately predict grain size and orientation distributions as a function of thermal and process history of different film/substrate combinations. Experimental and theoretical research on grain growth and texture evolution in polycrystalline films is focused towards the competitive effects on minimization of the film/substrate interface energy and minimization of strain energy densities. The research includes the polycrystalline-silver/single-crystal-nickel system, silver/copper, and a number of polycrystalline metallic films on a variety of silica-coated substrates with different thermal expansion coefficients. Strain energy is controlled through the choice of substrates and through modifications in thermal history. Known strains are imposed using 4-point and 3-point bending. Texture evolution is characterized using thin film X-ray diffraction and several electron diffraction techniques. Grain sizes are characterized using electron and focused ion beam microscopy and film stresses are monitored by measurements of wafer curvature, both during and after heating and grain growth. A computer program for simulation of grain growth in thin films will be improved to account for orientation-dependent strain-energy-density differences, in both elastically strained and plastically deformed films. %%% This research should improve technology for creating thin films used in a variety of industrial applications. ***