Abstract
HREM Studies of the atomistic structure of idealized metal/ceramic interfaces are important for both fundamental and applied reasons. Epitaxial growth by molecular beams allows to produce such interfaces under controlled conditions. Nb/Al2O3 has been chosen as a model system because of the absence of any chemical reactions between the metallic overlayer and the ceramic substrate and since both components possess nearly the same thermal expansion coefficient. Results of x-ray diffraction studies indicate that a unique three-dimensional orientation relationship exists between niobium and sapphire which is established for different choices of surface plane of the sapphire substrate. Aim of the present investigations was to study the orientation relationships and the atomic arrangement at the interface by conventional TEM and HREM.During MBE growth the sapphire substrates were heated to 1123 K and a vacuum in the 10-7Pa range was maintained. Typical growth rates of 1 monolayer/sec were obtained. Cross-section TEM samples were prepared by a special technique involving cylindrical alumina holders with a diameter of 3mm. Shielding was applied during ion-milling to reduce the effect of the different milling rate of Nb and Al2O3.
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Schedule a callMore From: Proceedings, annual meeting, Electron Microscopy Society of America
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