LaNiO3 Electrode Research Articles

Fabrication and electrical properties of sol-gel derived BaTiO3 films with metallic LaNiO3 electrode

Metallic LaNiO3 (LNO) films were prepared on LaAlO3 (LAO) by metalorganic decomposition (MOD) and their application as the bottom electrode in sol-gel derived BaTiO3 (BTO) thin film was studied by means of x-ray diffraction, Raman spectroscopy, and scanning electron microscopy. BTO film on LNO-coated LAO exhibited preferred (100) orientation and smooth surface with fine grains (∼50 nm). Electrical measurements on BTO film capacitor showed good ferroelectric hysteresis, lower loss tangent and good insulating properties. These results indicated the BTO/LNO heterostructure fabricated by sol-gel and MOD technique to be a promising combination for microelectronic device applications.

Electrical properties and crystal structure of (Ba,Sr)TiO3 films prepared at low temperatures on a LaNiO3 electrode by radio-frequency magnetron sputtering

(Ba,Sr)TiO3 films on a LaNiO3 underlayer were prepared by radio-frequency magnetron sputter deposition. The onset of crystallization of the films occurred at a deposition temperature (Td) as low as 200 °C. Good crystallinity was observed at Td⩾350 °C. A moderate high dielectric constant (εr∼170–250) of the films was obtained at relatively low Td∼200–300 °C. The value of εr showed a much slower increase with Td⩾350 °C than that expected from the progress of crystallinity. The deviation was attributed to an interdiffusion layer formed between the film and underlayer, which also caused an abnormal contact potential barrier and a decline of the εr value of the samples postannealed at 350 °C. Annealing at 300 °C under O2 atmosphere lessened the oxygen deficiency in the film and enhanced the dielectric constant without forming an interfacial layer.

Electrocatalysis of oxygen evolution/reductionon LaNiO3 prepared by a novel malic acid-aided method

A kinetic study of the electroformation and electroreduction of oxygen in KOH solutions has been carried out on a LaNiO3 electrode obtained through a malic acid precursor route. The new electrocatalyst was found to show greatly enhanced activity for both oxygen evolution and reduction. The apparent electrocatalytic activity of this electrode for oxygen reduction was more than 10 times higher than those reported for similar electrodes obtained by other methods. It was, however, observed to be less active electrocatalytically for oxygen evolution as compared to the active LaNiO3 electrode obtained by the Bockris–Otagawa coprecipitation method. The electrochemical reaction order with respect to OH− concentration was found to be approximately 1 in the case of oxygen evolution while that for oxygen reduction, was approximately −1. The Tafel slope values for the reactions were ∼2.3RT/F and ∼2×2.3RT/3F, respectively.

Epitaxial Pb(Zr0.53Ti0.47)O3/LaNiO3 heterostructures on single crystal substrates

Epitaxial near-stoichiometric ferroelectric Pb(Zr0.53Ti0.47)O3 thin films were fabricated on epitaxial metallic LaNiO3 electrodes deposited on (001) SrTiO3 and (001) LaAlO3 single crystal substrates by pulsed laser ablation. The P–E hysteresis loop of PZT in the trilayer of Ag/PZT/LNO/STO was measured using the Sawyer–Tower circuit. The remnant polarization Pr and coercive field Ec at room temperature were 30 μC/cm2 and 69.3 kV/cm (peak-to-peak voltage=30 V, 50 Hz), respectively.

Effect of textured LaNiO3 electrode on the fatigue improvement of Pb(Zr0.53Ti0.47)O3 thin films

By changing the electrode combination of Pt and LaNiO3 (LNO), four capacitor types of Pt/PZT/Pt/Si, Pt/LNO/PZT/Pt/Si, Pt/LNO/PZT/LNO/Pt/Si, and Pt/PZT/LNO/Pt/Si, were prepared to investigate the fatigue and hysteresis characteristics of the sol-gel-derived Pb(Zr0.53Ti0.47)O3 (PZT) ferroelectric thin films. Among them, the (100)- and (001)-oriented PZT films were grown on the (100)-textured LNO electrode, but randomly oriented films were obtained on the Pt electrode. It was found that the use of LNO bottom electrode would improve the fatigue property quite significantly, but only the capacitor with LNO as both top and bottom electrodes is shown to be fatigue-free up to 1011 cycles, and the shapes of the hysteresis loop almost unchanged after the fatigue test.

Effects of Sputter-Deposited LaNiO3 Electrode on the Deposition and Properties of Ferroelectric Thin Films

AbstractHighly (100)-textured thin film of metallic LaNiO3 (LNO) was grown on the Pt/Ti/SiO2/Si substrates by rf magnetron sputtering at ˜300°C, which was used as a bottom electrode to prepare highly (100)-textured ferroelectric films. Examples on the deposition of PbTiO3, (Pbl−xLax)TiO3, Pb(Zr0.53Ti0.47)O3, Pb[(Mg1/3Nb2/3)1−xTix]O3, and (Ba1−xSrx)TiO3 thin films by rf magnetron sputtering or sol-gel method are shown. A reduction of temperature for perovskite phase formation can be achieved, especially for those difficult to crystallize. The surface roughness of the ferroelectric films is also improved as compared to that of films deposited on conventional Pt electrode. Although the electrical properties of the ferroelectric films are affected by the out-diffusion of LNO when a higher temperature was used in the preparation of the films, under an appropriate processing condition, the highly (100)-textured films can have satisfactory electrical characteristics for application. Moreover, the polarization-fatigue property can be also improved by the use of LNO electrode.

Effects of (100)-Textured LaNiO3 Electrode on Crystallization and Properties of Sol-Gel-Derived Pb(Zr0.53Ti0.47)O3 Thin Films

Sol-gel-derived thin films of Pb(Zr0.53Ti0.47)O3 (PZT) were spin-coated onto the (100)-textured LaNiO3 (LNO) electrode which was deposited on a Pt/Ti/SiO2/Si substrate by rf magnetron sputtering at 350° C. The annealing temperature for obtaining a perovskite PZT film on LNO was reduced by about 50° C compared with that direct deposition on Pt. Highly a- and c-axis-oriented PZT films were obtained by annealing at temperatures above 500° C, while randomly oriented films were formed on Pt electrode. Moreover, the grain size of PZT films grown on LNO was smaller than that of films on Pt. The dielectric constant, ε r, remanent polarization, P r, and coercive field, E c, of PZT films on LNO changed markedly with the annealing conditions. ε r increased and both P r and E c markedly decreased with increasing annealing temperature or time, which was attributed to the out-diffusion of LaNiO3 into PZT films during annealing. Use of the LNO layer as a bottom electrode was also found to greatly improve the fatigue property of PZT films.

Highly (100)-Oriented Thin Films of Sol-Gel Derived Pb[(Mg1/3Nb2/3)0.675Ti0.325]O3 Prepared on Textured LaNiO3 Electrode

Highly (100)-oriented thin films of Pb[(Mg1/3Nb2/3)0.675Ti0.325]O3 (PMNT) were fabricated by sol-gel method on (100)-textured LaNiO3 (LNO) metallic oxide electrode. The textured LaNiO3 layer was prepared by rf magnetron sputtering at 250° C on Si, SiO2/Si or Pt/Ti/SiO2/Si substrates. A well orientation match was found between the PMNT and LNO layers. The annealing temperature for obtaining a pure perovskite PMNT film was reduced for about 50° C by using the LNO-coated substrates comparing to that without. A well-developed grain structure was also formed for the former. Satisfactory dielectric and ferroelectric characteristics were observed from the (100)-oriented PMNT thin films prepared at 700° C on LNO, as compared to the randomly oriented one on Pt electrode. However, an increase of annealing temperature would cause a more serious out-diffusion of LNO which gradually deteriorated the property of PMNT films deposited on LNO.

Properties of highly (100)-oriented thin films of sol-gel derived on (100)-textured LaNiO3 electrode

The sol-gel derived Pb[(Mg13Nb23)xTi1−x]O3 (PMNT) thin films of x = 0.5–1.0 were prepared on (111)-textured Pt and (100)-textured LaNiO3 electrodes. Randomly oriented PMNT films were obtained by deposition on the Pt electrode. However, highly (100)-oriented PMNT films were formed on the LNO electrode, and a reduction of the perovskite phase formation temperature was also achieved. The (100)-oriented PMNT films showed a change of crystallographic anisotropy of dielectric and ferroelectric properties with respect to the change of composition. The compositions of cubic or rhombohedral phase had a lower permittivity and a less steep P-E hysteresis behavior compared to the films on Pt of the same composition, but that of tetragonal phase had a higher permittivity and a steeper P-E hysteresis loop. In general, the films on LNO exhibited a relatively higher dielectric loss and a broader hysteresis loop.

Preparation and characterization of thin films of LaNiO3 for anode application in alkaline water electrolysis

LaNiO3 electrodes were prepared, in the form of thin films on platinum by the methods of spray pyrolysis and sequential coating of mixed metal nitrate solutions followed by thermal decomposition. The films were adherent and of p-type semiconducting. Cyclic voltammetric studies indicated the formation of a quasireversible surface redox couple, Ni(iii)/Ni(ii), on these films before the onset of oxygen evolution in 1 m KOH. The anodic Tafel slopes were ∼40 and ∼65 mV decade−1, on the sprayed LaNiO3 film and on the film obtained by a layer method, respectively. The reaction order with respect to OH− was found to be 2.2 on the sprayed oxide film and 1.2 on the layer film. The sprayed oxide film was found to be electrocatalytically more active. It is suggested that the oxygen evolution reaction proceeds on both the film electrodes via the formation of the physisorbed H2O2 as an intermediate in the rate determining step.

Microstructural Studies of Ferroelectric Bi2VO5.5 Thin Films With LaNiO3 Electrodes

AbstractThin films of Bi2VO5.5 (BVO), a vanadium analog of the n = I member of the Aurivillius family, have been prepared by pulsed laser deposition. The BVO films grow along the [001] direction on LaNiO3(LNO) and YBa2Cu3O7 (YBCO) electrode buffer layers on LaA- IO3(LAO) substrates as obtained from X-ray diffraction studies. The microstructure of the films and of the interfaces within the film and between the film and the substrate were characterized using transmission electron microscopy. The in-plane epitaxial relationship of the rhombohedral LNO on perovskite LAO was [100] LNO // [100] LAO and [001] LNO // [001] LAO. High resolution lattice images showed a sharp interface between LNO and LAO. However, the LNO film is twinned with a preferred orientation along the growth direction. The BVO layer is single crystalline on both LNO/LAO and YBCO/LAO with the caxis parallel to the growth direction except for a thin layer of about 400 Å at the interface which is polycrystalline.

Growth and ferroelectric properties of Bi2VO5.5 thin films with metallic LaNiO3 electrodes

Novel ferroelectric bismuth vanadate, Bi2VO5.5 (BVO), thin films have been grown between lattice matched metallic LaNiO3 (LNO) layers deposited on SrTiO3 (STO) by the pulsed laser deposition technique. LNO/BVO/LNO/STO and Au/BVO/LNO/STO trilayer structures exhibited c-oriented (001) growth of BVO. LNO has been found to be a good metallic electrode with sheet resistance ∼20 Ω in addition to aiding c-axis oriented BVO growth. The dielectric constant, εr of LNO/BVO/LNO/STO, at 300 K was about 12. However, when an Au electrode was used on top of BVO/LNO/STO film, it showed a significant improvement in the dielectric constant (εr=123). The ferroelectric properties of BVO thin films have been confirmed by hysteresis behavior with a remnant polarization, Pr=4.6×10−8 C/cm2 and coercive field, Ec=23 kV/cm at 300 K.

The Mechanism of Oxygen Reduction at a LaNiO3 Electrode

Abstract The reaction mechanism of the O2 reduction at LaNiO3 was studied by using a rotating ring-disc electrode, which consists of a LaNiO3 disc and Pt ring electrodes. It was found that the O2 was completely reduced to OH− on the Hoare path. Oxygen vacancies seem to be required in the oxide surface for reduction of adsorbed O2H− to OH−.