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Microwave dielectric properties of BiFeO3 multiferoic films deposited on conductive layers

Sobiestianskas R., Vengalis B., Banys J., Devenson J., Oginskis A. K., Lisauskas V., Dapkus L.

Materials Science Poland

2011

Vol. 29, No. 1

41--46

Nondoped BiFeO3 (BFO) and doped Bi0.9La0.1Fe0.9Mn0.1O3 (BLFMO) thin films (d = 200-350 nm) were grown at 650- 750 °C by RF sputtering on Si and SrTiO3(100), coated by conductive LaNiO3 films and La2/3Ca1/3MnO3/SrRuO3 bilayers. The complex dielectric permittivity of the films was measured at room temperature in the frequency range from 10 MHz to 10 GHz using parallel plate capacitor structures. Dielectric properties of the polycrystalline BFO films were compared with those of the epitaxial quality BLFMO films, and it was seen that the latter has better microwave performance than the former. The dielectric losses were below 0.05 at 1 GHz frequency, which may be acceptable for microwave applications.

Investigation of the aging of epitaxial LaNiO3-x films by X-ray photoelectron spectroscopy

Mickevicius S., Grebinskij S., Bondarenka V., Tvardauskas H., Vengalis B., Sliuziene K., Orłowski B. A., Drube W.

Optica Applicata

2006

Vol. 36, nr 2-3

235-243

The X-ray photoelectron spectroscopy (XPS) was performed to study surface and volume composition, valence states and the concentration of hydroxyl groups in epitaxial LaNiO3?x thin films after aging in air. The existence of at least few different forms of oxygen as lattice oxide, hydroxyl groups and adsorbed water in the samples is shown by XPS characterization. The lanthanum and nickel exist in oxide and hydroxide chemical states. The concentration of hydroxyl groups increases at the surface but it is distributed through the volume as well. It was found that the surface Ni/La concentration ratio is close to the stoichiometric bulk value.