Preparation, properties and structure of metal/oxide interfaces

Bicrystal specimens of accurately controlled orientation and interface purity are critical for research into the structure and properties of interfaces. An apparatus is described which allows single crystals of a metal and an oxide to be bonded in exact, predetermined azimuthal orientation in an ultra high vacuum after sputter cleaning. Provisions for the monitoring of surface cleanliness by Auger spectroscopy and for controlled deposition of impurities on the mating surfaces are described. Interfacial bond strength is assessed by measuring the work of propagation of a crack along the interface, and the fracture mechanical background of such measurements is discussed. The structure of the interfaces is studied by conventional and high resolution TEM. Such studies have been performed on interfaces created by diffusion bonding and by in-situ growth of oxide particles in metal matrices. Systems studied include Nb/A12O3, Cu/A12O3, Pd/A12O3, Pd/ZnO, Ag/ZnO, and Ag/CdO. All interfaces were found to be atomically sharp and to have densely packed planes and directions of the metal parallel to those of the oxygen sublattice; residual misorientation is accommodated by dislocations. For Ag/CdO and Pd/ZnO, HREM and hydrogen trapping experiments show that the outermost plane of the oxide consists either of oxygen or metal ions, depending on the relative activities of the two components in the matrix