Synthesis, optical and ferroelectric properties of PZT thin films: experimental and theoretical investigation

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

An investigation on sliding wear behavior of PVD coatings

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Evaluation on fatigue strength of AISI 4340 steel aluminum coated by electroplating and IVD processes

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

Fatigue behavior of PVD coated Ti-6Al-4V alloy

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Photoinduced structural changes in antimony polyphosphate based glasses

A photocontraction effect in amorphous films of the binary glass system 0.20 [Sb(PO3)(3)](n)-0.80 Sb2O3 has been observed after UV irradiation using the 350.7 nm Kr+ ion laser line with 5.0 W/cm(2). Good optical quality films up to 4.0 mum were deposited on silica substrates at room temperature in vacuum by electron beam physical vapor deposition (EB-PVD) and characterized using WDX, XRD, optical absorption, infrared reflectance, profilometry and atomic force microscopy (AFM) techniques. Very stable glasses were prepared by the melt quenching technique and used as evaporation source for the production of films. The photoinduced structural change (PSC) was observed as a variation of about 6% in the film thickness and this effect is accompanied by a photobleaching of the irradiated area with a blue shift of the optical absorption edge. Otherwise this photoinduced change in the film thickness is very sensitive to the variations in the shape and intensity of the laser beam; therefore several possibilities in optical recording arise from these results. (C) 2003 Published by Elsevier B.V.

Improvement of the ferroelectric properties of ABO(3) (A= Pb, Ca, Ba; B=Ti, Zr) films

High-quality ABO(3)/LaNiO3 (A = Ph, Ca, Ba; B = Ti, Zr) hetero structures have been grown on LaAlO3 (1 0 0) substrate by the chemical solution deposition method and crystallized by a microwave oven technique. The structural, morphological and electric properties were characterized by means of X-ray diffraction (XRD), atomic force microscope (AFM), and dielectric and ferroelectric measurements. XRD patterns revealed single-phase polycrystalline and oriented thin films whose feature depends on the composition of the films. The AFM surface morphologies showed a smooth and crack-free surface with the average grain size ranging from 116 to 300 nm for both LaNiO3 electrode and the ferroelectric films. Dielectric measurements on these samples revealed dielectric constants as high as 1800 at frequency of 100 KHz. Such results showed that the combination of the chemical solution method with the microwave process provides a promising technique to grow high-quality thin films with good dielectric and ferroelectric properties. (c) 2005 Elsevier Ltd. All rights reserved.

Electron field emission from boron doped microcrystalline diamond

Field emission properties of hot filament chemical vapor deposited boron doped polycrystalline diamond have been studied. Doping level (N-B) of different samples has been varied by the B/C concentration in the gas feed during the growth process and doping saturation has been observed for high B/C ratios. Threshold field (E-th) for electron emission as function of B/C concentration has been measured, and the influences of grain boundaries, doping level and surface morphology on field emission properties have been investigated. Carrier transport through conductive grains and local emission properties of surface sites have been figured out to be two independent limiting effects in respect of field emission. Emitter current densities of 500 nA cm(-2) were obtained using electric fields less than 8 V/mu m. (c) 2007 Elsevier B.V. All rights reserved.

Retorno de nutrientes ao solo via deposição de serapilheira de quatro espécies leguminosas arbóreas na região de Botucatu - São Paulo, Brasil

The annual litter fall production and the concentrations of macronutrients of four leguminous tree species were evaluated. The experiment was installed in a distrophic red yellow latosol (Oxisol), derivative of the Bauru sandstone group. The studied species were: Leucaena leucocephala. Acacia melanoxylon, L. diversifolia and Mimosa scabrella. The experimental design was randomized blocks, with four treatments (species) and four replications. The litter fall was collected in boxes measuring 50×50×10 cm, two boxes by treatment in each block. The material was collected monthly and dried, weighed and chemically analyzed. The litter fall deposition occurred in the following order: M. scabrella (7,051 kg ha -1 ano -1), A. melanoxylon (2,789 kg ha -1 ano -1), L. diversifolia (1,576 kg ha -1 ano -1) and L. leucocephala (1,389 kg ha -1 ano -1). The content of nutrients obeyed the following order: N>Ca>K>Mg>P>S, with the exception of L. leucocephala that presented a bigger content of S in relation to the P.

Magnetic domain states in nano-sized Co nuclei electrodeposited onto monocrystalline silicon

In the present work, nano-sized magnetic nuclei of Co have been electrodeposited onto p-Si (111). The deposition follows a mechanism of progressive nucleation and growth controlled by diffusion. MFM studies showed that the transition between magnetic domain states is strongly dependent on the size and shape of the nuclei. A critical height h0 is defined below which the nuclei presented always a single-domain configuration. The limiting lower boundary for the single-domain state calculated from the theory is quantitatively coincident with the experimental results. © 2004 Elsevier B.V. All rights reserved.

Study of polypropylene surface modification by air dielectric barrier discharge operated at two different frequencies

In this work, air dielectric barrier discharge (DBD) operating at the line frequency (60 Hz) or at frequency of 17 kHz was used to improve the wetting properties of polypropylene (PP). The changes in the surface hydrophilicity were investigated by contact angle measurements. The plasma-induced chemical modifications of PP surface were studied by X-ray photoelectron spectroscopy (XPS) and Fourier-transformed infrared spectroscopy (FTIR). The polymer surface morphology and roughness before and after the DBD treatment were analyzed by atomic force microscopy (AFM). To compare the plasma treatment effect at different frequencies the variation of the contact angle is presented as a function of the deposited energy density. The results show that both DBD treatments leaded to formation of water-soluble low molecular weight oxidized material (LMWOM), which agglomerated into small mounts on the surface producing a complex globular structure. However, the 60 Hz DBD process produced higher amount of LMWOM on the PP surface comparing to the 17 kHz plasma treatment with the same energy dose. The hydrophilic LMWOM is weakly bounded to the surface and can be easily removed by polar solvents. After washing the DBD-treated samples in de-ionized water their surface roughness and oxygen content were reduced and the PP partially recovered its original wetting characteristics. This suggested that oxidation also occurred at deeper and more permanent levels of the PP samples. Comparing both DBD processes the 17 kHz treatment was found to be more efficient in introducing oxygen moieties on the surface and also in improving the PP wetting properties. © 2012 Elsevier B.V. All rights reserved.

Production and characterization of Tm3+/Yb3+ codoped waveguides based on PbO-GeO2 thin films

Fabrication and optical characterization of Tm3+/Yb3+ codoped PbO-GeO2 (PGO) pedestal-type waveguides are investigated in this work. It is important to mention that, to the best of authors' knowledge, the use of PGO pedestal-type waveguide has not been studied before. PGO thin films codoped with Tm3+ and Yb3+ were obtained through RF magnetron sputtering technique. The pedestal profile was obtained using conventional optical lithography procedures, followed by plasma etching and sputtering deposition. The profile of Tm3+/Yb3+ codoped PGO waveguides was observed by means of Scanning Electron Microscopy (SEM) measurements. Also the infrared and infrared-to-visible frequency upconversion luminescences of Tm3+ ions were measured exciting the samples with a cw 980 nm diode laser. Propagation losses around 11 dB/cm and 9 dB/cm were obtained at 630 and 1050 nm, respectively, for waveguides in the 20-100 μm width range. Single-mode propagation was observed for waveguides width up to 12 μm and 7 μm, at 1050 nm and 630 nm, respectively; larger waveguides width provided multi-mode propagation. The present results corroborate the possibility of using Tm3+/Yb3+ codoped PGO thin films as active waveguide for photonic applications. © 2013 Elsevier B.V. All rights reserved.

Ferroelectric and structural instability of (Pb,Ca)TiO3 thin films prepared in an oxygen atmosphere and deposited on LSCO thin films which act as a buffer layer

Structural, microstructural and ferroelectric properties of Pb0.90Ca0.10TiO3 (PCT10) thin films deposited using La0.50Sr0.50CoO3 (LSCO) thin films which serve only as a buffer layer were compared with properties of the thin films grown using a platinum-coated silicon substrate. LSCO and PCT10 thin films were grown using the chemical solution deposition method and heat-treated in an oxygen atmosphere at 700 °C and 650 °C in a tube oven, respectively. X-ray diffraction (XRD) and Raman spectroscopy results showed that PCT10 thin films deposited directly on a platinum-coated silicon substrate exhibit a strong tetragonal character while thin films with the LSCO buffer layer displayed a smaller tetragonal character. Surface morphology observations by atomic force microscopy (AFM) revealed that PCT10 thin films with a LSCO buffer layer had a smoother surface and smaller grain size compared with thin films grown on a platinum-coated silicon substrate. Additionally, the capacitance versus voltage curves and hysteresis loop measurement indicated that the degree of polarization decreased for PCT10 thin films on a LSCO buffer layer compared with PCT10 thin films deposited directly on a platinum-coated silicon substrate. This phenomenon can be described as the smaller shift off-center of Ti atoms along the c-direction 〈001〉 inside the TiO6 octahedron unit due to the reduction of lattice parameters. Remnant polarization (P r ) values are about 30 μC/cm2 and 12 μC/cm2 for PCT10/Pt and PCT10/LSCO thin films, respectively. Results showed that the LSCO buffer layer strongly influenced the structural, microstructural and ferroelectric properties of PCT10 thin films. © 2013 Elsevier Ltd and Techna Group S.r.l.

Construção e caracterização de células solares de filmes finos de CdS e CdTe

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Preparação e caracterização de semicondutores de PbS e 'B IND. I 'IND. 2' 'S IND. 3' obtidos pelo método de deposição em banho químico

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

Assistência de ar em pulverização no manejo fitossanitário na cultura da soja Glycine max (L.) Merrill

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)