Crystallographically textured superconducting YBa2Cu3O7−δ thin films 2–10 μm in thickness have been grown on (100) MgO substrates by a spray pyrolysis method. The structure, morphology, and composition of the films have been demonstrated by x-ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy, respectively, to show strong texturing and a composition close to that expected for the bulk ceramic. The onset of the superconducting transition is at 82 K and zero resistance is achieved at 76 K with a critical current density of 3700 A/cm2 at 30 K.

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Sodium overlayers on the ͑100͒ and ͑110͒ facets of a tungsten field emitter in the range of coverage from 0 to 1.2 monolayers have been studied by means of field-and photofield-emission spectroscopy. On the ͑100͒ facet, the adatom configuration is strongly influenced by the applied electric field. On the ͑110͒ facet, a planar island of sodium grows on top of the first monolayer. The observed energy dependencies of the surface densities of states of Na/W͑100͒ and Na/W͑110͒ show similar features that are related to the valence electronic levels of sodium weakly perturbed by interaction with the substrate. The data provide evidence that a sodium monolayer strongly enhances field emission from below the Fermi level on W͑100͒ but not on W͑110͒.