Dielectric properties of Ca(Zr0.05Ti0.95)O-3 thin films prepared by chemical solution deposition

Ca(Zr0.05Ti0.95)O-3 (CZT) thin films were grown on Pt(1 1 1)/Ti/SiO2/Si(1 0 0) substrates by the soft chemical method. The films were deposited from spin-coating technique and annealed at 928 K for 4 h under oxygen atmosphere. CZT films present orthorhombic structure with a crack free and granular microstructure. Atomic force microscopy and field-emission scanning electron microscopy showed that CZT present grains with about 47 nm and thickness about 450 nm. Dielectric constant and dielectric loss of the films was approximately 210 at 100 kHz and 0.032 at 1 MHz. The Au/CZT/Pt capacitor shows a hysteresis loop with remnant polarization of 2.5 mu C/cm(2), and coercive field of 18 kV/cm, at an applied voltage of 6 V. The leakage current density was about 4.6 x 10(-8) A/cm(2) at 3 V. Dielectric constant-voltage curve is located at zero bias field suggesting the absence of internal electric fields. (c) 2006 Elsevier B.V. All rights reserved.

Ferroelectric characteristics of SrBi4Ti4O15 thin films grown on Pt/Ti/SiO2/Si substrates by the soft chemical method

Ferroelectric SrBi4Ti4O15 thin films were successfully prepared on a Pt(111)/Ti/SiO2/Si(100) substrate for the first time by spin coating, using the polymeric precursor method. X-ray diffraction patterns of the films indicate that they are polycrystalline in nature. Atomic force microscopy (AFM) analyses showed that the surface of these films is smooth, dense and crack-free with low surface roughness (6.4 nm). At room temperature and at a frequency of 1 MHz, the dielectric constant and the dissipation factor were, respectively, 150 and 0.022. The C-V characteristics of perovskite thin film prepared at low temperature show normal ferrolectric behaviour. The remanent polarization and coercive field for the films deposited were 5.4 mu C/cm(2) and 8 5 kV/cm, respectively. All the capacitors showed good polarization fatigue characteristics at least up to 1 x 10(10) bipolar pulse cycles indicating that SrBi4Ti4O15 thin films can be a promising material for use in nonvolatile memories. (c) 2005 Elsevier B.V. All rights reserved.

Ferroelectric and dielectric properties of Ba0.5Sr0.5(Ti0.80Sn0.20)O-3 thin films grown by the soft chemical method

Polycrystalline Ba0.5Sr0.5(Ti0.80Sn0.20)O-3 (BST:Sn) thin films with a perovskite structure were prepared by the soft chemical method on a platinum-coated silicon substrate from spin-coating technique. The resulting thin films showed a dense structure with uniform grain size distribution. The dielectric constant of the films estimated from C-V curve is around 1134 and can be ascribed to a reduction in the oxygen vacancy concentration. The ferroelectric nature of the film indicated by butterfly-shaped C-V curves and confirmed by the hysteresis curve, showed remnant polarization of 14 mu C/cm(2) and coercive field of 74 kV/cm at frequency of 1 MHz. At the same frequency, the leakage current density at 1.0 V is equal to 1.5 x 10(-7) A/cm(2). This work clearly reveals the highly promising potential of BST:Sn for application in memory devices. (c) 2006 Elsevier B.V. All rights reserved.

Ferroelectric and dielectric behaviour of Bi0.92La0.08FeO3 multiferroic thin films prepared by soft chemistry route

Bi0.92La0.08FeO3 (BLFO) thin films were grown on platine substrates by the soft chemical route. Ferroelectric and dielectric behaviors of BLFO films deposited by spin-coating technique and annealed at 773 K for 2 h in air atmosphere were explained. BLFO thin films obtained presents a rhombohedral structure. The BLFO films present dielectric and ferroelectric behaviors with dielectric permittivity and dielectric loss of approximately 81 and 0.0144 at 1 kHz. The Au/BLFO/Pt capacitor shows a hysteresis loop with remnant polarization of 20.6 mu C/cm(2) and coercive field of 53.88 kV/cm. The polarization switching and the fatigue behavior of the BLFO films were significantly enhanced.

Characterization of lanthanum-doped bismuth titanate thin films prepared by polymeric precursor method

Lanthanum-modified bismuth titanate, Bi4-xLaxTi3O12 (BLT), with x ranging from 0 to 0.75 was grown on Pt/Ti/SiO2/Si substrates using a polymeric precursor solution and spin-coating method. The dielectric constant of highly doped bismuth titanate was equal to 148 while dielectric losses remained low (tan delta = 0.0018), and the films showed well-saturated polarization-electric field curves (2P(r) = 40.6 muC/cm(2) and V-c = 0.99 V). The leakage current densities improve for the lanthanum-doped system. For five-layered BLT films with x = 0.75, a charge storage density of 35 fC/mum(2) and a thickness of 320 nm were found. (C) 2004 Elsevier B.V. All rights reserved.

Filmes de titânio-silício preparados por spin e dip-coating

The conditions for the preparation of luminescent materials, consisting of Eu3+ ions entrapped in a titanium matrix, in the forma of a thin film, using the sol-gel process, are described. The films were obtained from sols prepared with TEOS and TEOT, in the presence of acetylacetone as the hidrolysis-retarding agent, using the dip-coating and spin-coating techniques. The influence of these techniques on the films based on titanium and silicon are presented. The Eu3+ was used as a luminescent probe. The films have been characterized by luminescence, reflection and transmittance. The thickness of the films could be related to the preparation procedure. Transparent thin films have been prepared by dip-coating technique.

Antioxidant Properties of Plant Extracts: an EPR and DFT Comparative Study of the Reaction with DPPH, TEMPOL and Spin Trap DMPO

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

Sobre o limiar para a produção de pares e localização de partículas sem spin

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

The Gerasimov-Drell-Hearn Sum Rule and the Spin Structure of the Proton

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

Spin-1 particle in the light-front approach

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

Asymmetrical penetration of microwave in a conducting media and determination of microwave conductivity for very thin samples using electron spin resonance

Dyson's theory of conduction electron spin resonance (CESR) has been used in the limit d less than or equal to delta (d being the thickness of the sample and delta the skin depth of the microwave field) to obtain the microwave conductivity from the (A/B) ratio of the CESR absorbed power derivative. In this work we calculate the CESR absorbed power derivative using Kaplan's approach and show that the (A/B) ratio can be enhanced if asymmetrical penetration of microwave is used, which means that the microwave field enters into the sample from one of the faces. Therefore, the determination of the microwave conductivity from the (A/B) ratio of the CESR line can be performed for thinner samples. Experimentally, asymmetrical penetration can be obtained if one of the sample's faces is covered with a thin gold layer. The determination of microwave conductivity in conducting polymers films is among the possible applications of this method. (C) 2001 Elsevier B.V. Ltd. All rights reserved.

Ferroelectric and microstructural characteristics of SrBi2Ta2O9 thin films crystallized by the rapid thermal annealing process

Ferroelectric SrBi2Ta2O9 thin films on Pt/Ti/SiO2/Si were successfully synthesized by the modified polymeric precursor method. The films were deposited by spin coating and crystallized by rapid thermal annealing in a halogen lamp furnace, followed by postannealing at temperatures ranging from 700 degreesC to 800 degreesC in an oxygen atmosphere. Microstructural and phase evaluations were followed by x-ray diffraction and atomic force microscopy. The films displayed spherical grain structures with a superficial roughness of approximately 3-6 nm. The dielectric constant values were 121 and 248 for films treated at 700 degreesC and 800 degreesC, respectively. The P-E curve showed a voltage shift toward the positive side, which was attributed to crystallization under the halogen illumination. The remanent polarization (2P(r)) and coercive field (E-c) were 7.1 muC/cm(2) and 113 kV/cm, and 18.8 muC/cm(2) and 93 kV/cm for the films treated at 700 degreesC and 800 degreesC, respectively. (C) 2001 American Institute of Physics.