Structural, microstructural, and transport properties of highly oriented LaNiO3 thin films deposited on SrTiO3(100) single crystal

Electrical conductive textured LaNiO3/SrTiO3 (100) thin films were successfully produced by the polymeric precursor method. A comparison between features of these films of LaNiO3 (LNO) when heat treated in a conventional furnace (CF) and in a domestic microwave (MW) oven is presented. The x-ray diffraction data indicated good crystallinity and a structural orientation along the (h00) direction for both films. The surface images obtained by atomic force microscopy revealed similar roughness values, whereas films LNO-MW present slightly smaller average grain size (similar to 80 nm) than those observed for LNO-CF (60-150 nm). These grain size values were in good agreement with those evaluated from the x-ray data. The transport properties have been studied by temperature dependence of the electrical resistivity rho(T) which revealed for both films a metallic behavior in the entire temperature range studied. The behavior of rho(T) was investigated, allowing to a discussion of the transport mechanisms in these films. (C) 2007 American Institute of Physics.

Structural and ferroelectric properties of Pb1-xSrxTiO3 thin films

Strontium-modified lead titanate (PST) thin films with composition Pb1-xSrxTiO3 (0.10 < x &LE; 0.60) were grown on Pt/Ti/SiO2/Si substrates using a soft chemical process. The crystallization of the PST thin films was achieved by heat treatment at 600&DEG;C. The structural and microstructural modifications in the films were studied using X-ray diffraction (XRD) and atomic force microscopy, respectively. The XRD study shows that the lattice parameters of polycrystalline PST thin films calculated from X-ray data indicate a decrease in lattice tetragonality with the increase in strontium content in these films. This indicates a gradual change from tetragonal to cubic structure. By atomic force microscopy analysis, the average grain size of the thin films was systematically reduced with the increase in Sr content. The dielectric property of the thin films was found to be strongly dependent on the Sr concentration. With 60 at.% Sr content, a ferroelectric to paraelectric phase transition was observed at room temperature.

Effect of temperature on the optical properties of GaAsSbN/GaAs single quantum wells grown by molecular-beam epitaxy

GaAsSbN/GaAs strained-layer single quantum wells grown on a GaAs substrate by molecular-beam epitaxy with different N concentrations were studied using the photoluminescence (PL) technique in the temperature range from 9 to 296 K. A strong redshift in optical transition energies induced by a small increase in N concentration has been observed in the PL spectra. This effect can be explained by the interaction between a narrow resonant band formed by the N-localized states and the conduction band of the host semiconductor. Excitonic transitions in the quantum wells show a successive red/blue/redshift with increasing temperature in the 2-100 K range. The activation energies of nonradiative channels responsible for a strong thermal quenching are deduced from an Arrhenius plot of the integrated PL intensity. (C) 2003 American Institute of Physics.

Effect of additives and powder preparation techniques on PTCR properties of barium titanate

PTCR barium titanate has been prepared following two different powder preparation techniques: the solid-state reaction route and co-precipitation route for the comparison of results. The co-precipitation route produces better PTCR characteristics with low room temperature resistivity and better reproducibility of prepared samples. The effects of different concentrations of additives like donors, acceptors and excess titanium have been optimized to get good quality PTCR samples. (C) 2002 Elsevier B.V. B.V. All rights reserved.

Non-Ohmic and dielectric properties of a Ca2Cu2Ti4O12 polycrystalline system

An investigation was made into the non-Ohmic and dielectric properties of a Ca2Cu2Ti4O12 perovskite-type system. Compared to the traditional CaCu3Ti4O12-based composition, the imbalance between the Ca and Cu atoms caused the formation of a polycrystalline system presenting similar to 33.3 mol % of CaCu3Ti4O12 (traditional composition) and similar to 66.7 mol % of CaTiO3. As for non-Ohmic properties, the effect of this Ca and Cu atom imbalance was that a nonlinear electric behavior of similar to 1500 was obtained. This high nonlinear electrical behavior emerged in detriment to the ultrahigh dielectric property frequently reported. The high non-Ohmic property was explained by the existence of Schottky-type barriers, whose formation mechanism may be similar to that proposed for traditional metal oxide non-Ohmic devices, according to similarities discussed herein. (c) 2006 American Institute of Physics.

The effect of N+ ion energy on the properties of ion bombarded plasma polymer films

This work describes the influence of the ion bombardment on the electrical, optical and mechanical properties of polymer films deposited from radio-frequency plasmas of benzene. Irradiations were conducted using N+ at 5 x 10(19) ions/m(2), varying the ion energy, E-0, from 0 to 150 keV. Film elemental composition was determined by Rutherford backscattering spectroscopy. Electrical resistivity and hardness were obtained by the two-point probe and nanoindentation technique, respectively. Ultraviolet-visible spectroscopy was employed to investigate the optical constants of the samples. Etching rate was determined by exposure of the films to reactive oxygen plasmas. Ion bombardment induced gradual loss of H and increase in C and O concentrations with Eo. As a consequence the electrical, optical and mechanical properties were drastically affected. Interpretation of these results is proposed in terms of chain cross-linking and unsaturation. (C) 2001 Elsevier B.V. B.V. All rights reserved.

The effect of Nb doping on ferroelectric properties of PZT thin films prepared from polymeric precursors

Pure and Nb doped PbZr0.4Ti0.603 thin films was prepared by the polymeric precursor method and deposited by spin coating on Pt/Ti/SiO2/Si (100) substrates and annealed at 700 degreesC. The films are oriented in (1 1 0) and (1 0 0) direction. The electric properties of PZT thin films show strong dependence of the crystallographic orientation. The P-E hysteresis loops for the thin film with composition PbZr0.39Ti0.6Nb0.103 showed good saturation, with values for coercive field (E-c) equal to 60 KV cm(-1) and for remanent polarization (P-r) equal to 20 muC cm(-2). The measured dielectric constant (epsilon) is 1084 for this film. These results show good potential for application in FERAM. (C) 2004 Elsevier B.V. All rights reserved.

Effect of La2O3 addition and O-2 atmosphere on the electric properties of SnO2TiO2

The electric properties of (Sn, Ti)O-2 doped with 1.00 mol% CoO, 0.05 mol% Nb2O5 and xmol% La2O3 (0.25 less than or equal to x less than or equal to 1.00) have been studied. Sn0.25Ti0.75Co0.01Nb0.005 doped with 0.50 mol% La2O3 has a nonlinearity coefficient of 6. An increase in the concentration of La2O3 raised its resistivity, thereby altering the electric properties of the material. A thermal treatment in oxygen atmosphere increased the nonlinearity coefficient to a value of 9. (C) 2003 Elsevier B.V. All rights reserved.

Influence of temperature on the dielectric and ferroelectric properties of bismuth titanate thin films obtained by the polymeric precursor method

The (1 1 7) and (0 0 1 0)-oriented Bi4Ti3O12 thin films were fabricated on Pt/Ti/SiO2/Si substrates by using a polymeric precursor solution under appropriate crystallization conditions. Atomic force microscopy and scanning electron microscopy showed relatively large grains, which is typical for this system. The capacitance dependence on voltage is strongly non-linear, confirming the ferroelectric properties of the films resulting from the domain switching. The (1 1 7)-oriented films exhibited a higher remanent polarization (23.7 μ C cm(-2)) than the (0 0 1 0)-oriented films (11.8 μ C cm(-2)). Fatigue tests revealed that the temperature of thermal treatment and degree of orientation affect the performance of the device. © 2005 Elsevier B.V. All rights reserved.

Temperature dependence on the electrical properties of Ba(Ti0.90Zr0.10)O-3:2V ceramics

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Influence of Ca concentration on the electric, morphological, and structural properties of (Pb,Ca)TiO3 thin films

Pb1-xCaxTiO3 (0.10less than or equal toxless than or equal to0.40) thin films on Pt/Ti/SiO2/Si(100) substrates were prepared by the soft solution process and their characteristics were investigated as a function of the calcium content (x). The structural modifications in the films were studied using x-ray diffraction and micro-Raman scattering techniques. Lattice parameters calculated from x-ray data indicate a decrease in lattice tetragonality with the increasing content of calcium in these films. Raman spectra exhibited characteristic features of pure PbTiO3 thin films. Variations in the phonon mode wave numbers, especially those of lower wave numbers, of Pb1-xCaxTiO3 thin films as a function of the composition corroborate the decrease in tetragonality caused by the calcium doping. As the Ca content (x) increases from 0.10 to 0.40, the dielectric constant at room temperature abnormally increased at 1 kHz from 148 to 430. Also calcium substitution decreased the remanent polarization and coercive field from 28.0 to 5.3 muC/cm(2) and 124 to 58 kV/cm, respectively. These properties can be explained in terms of variations of phase transition (ferroelectric-paraelectric), resulting from the substitution the lead site of PbTiO(3)for the nonvolatile calcium. (C) 2002 American Institute of Physics.

Structural refinement and photoluminescence properties of irregular cube-like (Ca-1_Cu-x(x))TiO3 microcrystals synthesized by the microwave-hydrothermal method

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Structure, microstructure and dielectric properties of 100-x(Bi0.5Na0.5)TiO3-x[SrTiO3] composites ceramics

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Er(3+) doped phosphoniobate glasses and planar waveguides: structural and optical properties

Phosphoniobate glasses with composition (mol%) (100-x) NaPO(3)-xNb(2)O(5) ( x varying from 11 to 33) were prepared and characterized by means of thermal analysis, Fourier transform infrared spectroscopy, Raman scattering and (31)P nuclear magnetic resonance. The addition of Nb(2)O(5) to the polyphosphate base glass leads to depolymerization of the metaphosphate structure. Different colors were observed and assigned as indicating the presence of Nb(4+) ions, as confirmed by electron paramagnetic resonance measurements. The color was observed to depend on the glass composition and melting temperature as well. Er(3+) containing samples were also prepared. Strong emission in the 1550 nm region was observed. The Er(3+4)I(15/2) emission quantum efficiency was observed to be 90% and the quenching concentration was observed to be 1.1 mol%( 1.45 x 10(20) ions cm(-3)). Planar waveguides were prepared by Na(+)-K(+)-Ag(+) ion exchange with Er(3+) containing samples. Optical parameters of the waveguides were measured at 632.8, 543.5 and 1550 nm by the prism coupling technique as a function of the ion exchange time and Ag(+) concentration. The optimized planar waveguides show a diffusion depth of 5.9 mu m and one propagating mode at 1550 nm.

Rietveld refinement, microstructure, conductivity and impedance properties of Ba[Zr0.25Ti0.75]O-3 ceramic

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)