Potassium niobate (KNbO3) thin films and potassium niobate/tantalate (KNbO3/KTaO3) superlattices have been grown on KTaO3 (001) substrates by pulsed laser deposition. The thin-film structures were analyzed by Rutherford backscattering/ion-channeling techniques, x-ray θ–2θ and Φ scans, and both conventional and Z-contrast scanning transmission electron microscopy. Excellent film flatness and crystallinity are evidenced by these techniques. At room temperature, the KNbO3 films are characterized by an orthorhombic structure which differs from that of bulk KNbO3. The interfaces between the layers in the KNbO3/KTaO3 superlattice structures were found to be compositionally sharp on an atomic scale.

Coherent precipitates of vanadium dioxide have been formed in the near-surface region of sapphire by the stoichiometric coimplantation of vanadium and oxygen combined with subsequent thermal processing at temperatures ranging from 700 to 1000 °C. The embedded VO2 precipitates, which are three-dimensionally oriented with respect to the Al2O3 host lattice, undergo a first-order monoclinic-to-tetragonal (and also semiconducting-to-metallic) phase transition at ∼77 °C. This transformation is accompanied by a significant variation in the optical transmission of the implanted region and results in the formation of an optically active, thermally ‘‘switchable’’ surface region on Al2O3.

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Synthesis of the perovskite solid solution that forms between metallic SrRuO3 and insulating SrSnO3 is reported. This material is proposed as a conducting thin-film electrode/epitaxial-substrate material. While the bulk solid solution could not be formed, thin films of single-phase SrRu0.5Sn0.5O3 were grown on (001) KTaO3 single-crystal substrates by pulsed laser deposition. These films exhibit a commensurate in-plane lattice match with KTaO3 (a=3.989 Å); accordingly, the lattice constant of SrRu0.5Sn0.5O3 is larger than that of commonly used conducting-oxide thin-film electrodes (e.g., SrRuO3, LaNiO3, and YBa2Cu3O7−δ). The SrRu0.5Sn0.5O3 films were analyzed using x-ray diffraction, Rutherford backscattering, atomic force microscopy, Z-contrast transmission electron microscopy, and Hall effect measurements. The results revealed excellent atomic-scale structural properties, flat surfaces (13 Å rms roughness), and p-type conduction with a room-temperature resistivity of 16 mΩ cm.

Crystallographically coherent precipitates of vanadium dioxide (VO2) have been formed in the near-surface region of single crystals of sapphire (Al2O3) using a combination of ion implantation and thermal treatments. As in the case of either bulk VO2 single crystals or thin films of VO2, the thermally induced semiconductor-to-metal phase transition of the embedded VO2 precipitates is accompanied by a large hysteretic change in the infrared optical transmission. The VO2 precipitate transition temperature (Tc = 72 to 85 °C) is higher than that of bulk VO2 (Tc = 68 °C) and is sensitive to the implantation conditions. The present results show that the damage resulting from the coimplantation of vanadium and oxygen into an Al2O3 host lattice dictates the final microstructure of the VO2 precipitates and, consequently, affects the transition temperature, as well as the optical quality of the VO2/Al2O3 surface-nanocomposite precipitate system.