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The ultrahigh vacuum technique of molecular-beam epitaxy (MBE) has been successfully employed in growing highly oriented polycrystal and single-crystal niobium oxide layers on z-cut LiNbO3 substrates. A new variant of the monoxide has been grown and characterized, and the potential advantages and limitations of MBE for growing the higher oxides, such as Nb2O5, are put forward. Niobium metal layers have also been grown on z-cut LiNbO3. The deposition of excellent quality niobium oxide on α-alumina (z-cut sapphire) has been demonstrated, providing an optical waveguiding structure of large differential refractive index. Crystallinity and compositional data are presented for all the above layers. The post-deposition oxidation of oxygen-deficient films to the pentoxide has been studied in detail, and system requirements for the in situ growth of Nb2O5 proposed.

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Superconducting thin films of the Bi-Sr-Ca-Cu-O system with and without lead doping were prepared by rf magnetron sputtering onto (100)MgO substrates. Although the superconducting properties of the thin films are very sensitive to the deposition and soak temperatures, reproducible results were obtained. Our in situ deposition process with processing temperatures not exceeding 600 °C yielded films with zero resistance at 82 K and Jc=7×105 A cm−2 measured at 4 K for the two-layer Bi phase. Our initial results with lead-doped Bi-Sr-Ca-Cu-O thin films will also be discussed.

We present new Raman scattering data on high-temperature superconducting materials with composition YBa2(Cui -"Al")307 q. In YBa2Cu307 q we observe new high-frequency peaks greater than 700 cm ' that we associate with two-phonon interactions of the erst-order Cu -0 Raman vibrations that occur at 337, (450 10), and 502 cm '. The intensity of these new 36 8315