Role of Grain Structure and Grain Boundary Diffusion in Thin Film Reactions

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9308651 Barmak This project examines grain structure and grain boundary diffusion in thin film niobium aluminide polycrystalline films of different thicknesses and microstructures. The kinetics of Nb3Al formation are studied with calorimetry and transmission electron microscopy. A model for the Nb3Al formation will be modified based on the measurements of shape, growth rate, and nucleation density. Nucleation sites will be linked to microstructural features of the reactant layers. Direct measurements of the composition of Nb3-xAl phase will be made by analytical electron microscopy. An increase in the Al concentration of the Nb3-xAl phase with an increase in the total boundary area of the Nb3Al layer should provide direct evidence for the role of grain boundary diffusion in the reaction. %%% This research has relevance to thin film devices used in the microelectronic and magnetic thin film industries. ***