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Papers by Mauricio Pilleux

Journal of Applied Physics, 1993

Insulating barium titanate films were successfully grown on Ti-deposited silicon substrates using... more Insulating barium titanate films were successfully grown on Ti-deposited silicon substrates using the hydrothermal method. The film thickness was 35 and 49 nm for films treated at 200 and 250 "C!, respectively, in a 0.25 M Ba(OH)z solution for 8 h. The BaTiO, films did not reach the Ti/Si interface. X-ray photoelectron spectroscopy revealed OH-free and nearly carbon-free films, which was corroborated using Auger electron spectroscopy (AES) depth analysis. AES revealed that the oxygen and barium concentrations are correlated throughout the film, and the existence of a diffuse BaTi03/Ti interface. A discussion on the film growth mechanism is made using existing information on the subject.

MRS Proceedings, 2001

Polycrystalline copper films thicker than 100 nm were evaporated on silicon wafers with their nat... more Polycrystalline copper films thicker than 100 nm were evaporated on silicon wafers with their native oxide under ultrahigh vacuum conditions leading to an rms roughness of ~2 nm of the copper film. X-ray photoelectron spectroscopy (XPS) revealed a clean copper surface with only traces of oxygen. The samples were exposed to air, leading to an oxide film consisting of CuO. TiO films were subsequently deposited onto the oxidized copper films from a resistively heated tungsten boat with the substrate at room temperature. The TiO films exhibited good adherence and were amorphous. XPS measurements revealed that the TiO films were contamination-free and that the first layers of TiO reduced the thin native oxide of the copper substrate from Cu(II) into Cu(I) or Cu(0) and transformed the TiO into TiO2 at the interface.

Vacuum, 1999

We have investigated the time dependence of water adsorption on polycrystalline barium titanate "... more We have investigated the time dependence of water adsorption on polycrystalline barium titanate "lms fabricated on silicon under hydrothermal conditions. X-ray photoelectron spectroscopy showed surface OH groups on the "lms but no molecular H O. The time dependent behavior of water adsorption was investigated by measuring the work function changes with a Kelvin probe. The "lm response time for both increasing and decreasing humidity is less than one minute. The typical amplitude change was about 0.05 eV for a 50% humidity variation, with higher variations at lower humidity.

Rapid Prototyping Journal, 2002

Three-dimensional photonic bandgap (PBG) structures using alumina (Al 2 O 3 ) as the high permitt... more Three-dimensional photonic bandgap (PBG) structures using alumina (Al 2 O 3 ) as the high permittivity material were modeled and then the structures were fabricated by Fused Deposition of Multi-materials (FDMM) technology. A nite element method and a real-time electromagnetic wave propagation software were used to simulate and design the layered PBG structures for applications in the microwave frequency range. The modeling predicted a 3-D photonic bandgap in the 16.5 -23.5 GHz range. FDMM provides a computer-controlled process to generate 3-D structures, allowing high fabrication exibility and ef ciency. Electromagnetic measurements displayed the presence of a bandgap between 17.1 -23.3 GHz, showing a good agreement with the predicted values. These PBG structures are potential candidates for applications in advanced communication systems.

Microwave and Optical Technology Letters, 2001

... Cond Matt 8 1996 , 10851108. 12. MA Jafari, W. Han, F. Mohammadi, A. Safari, SC Danforth, and... more ... Cond Matt 8 1996 , 10851108. 12. MA Jafari, W. Han, F. Mohammadi, A. Safari, SC Danforth, and N. Langrana, A novel system for fused deposition of ad- . vanced multiple ceramics, Rapid Prototyping J 6 2000 , 161174. 13. ...

Materials Letters, 1993

A model describing the roles of initial vacancy concentration and effective vacancy migration ene... more A model describing the roles of initial vacancy concentration and effective vacancy migration energy is proposed in order to predict the short-range-order kinetics of quenched binary alloys during linear heating experiments. The model has been applied to the differential scanning calorimetry thermogram of a-Cu-Al quenched from different temperatures.

Journal of the American Ceramic Society, 1994

Journal of Materials Research, 1995

Journal of Applied Polymer Science, 2006

Copper-embedded low-density polyethylene (LDPE) composites were fabricated using different copper... more Copper-embedded low-density polyethylene (LDPE) composites were fabricated using different copper concentrations in the polymer matrix. The copper particles were spherical with a mean particle size between 200 and 300 nm. All the samples were compacted under pressure and melted. The LDPE matrix was analyzed using gel permeation chromatography (GPC) and it did not evidence degradation of the LDPE matrix. The microstructure of the composites was examined with scanning electron microscopy. The electrical conductivity was measured as a function of the copper content, and the composite fabricated with a 10 vol % copper presented a conductivity 15 orders of magnitude higher than that of pure LDPE. The enhancement in conductivity can be explained by means of segregated percolation path theory and the experimental results are in agreement with the theoretical law.

Corrosion Engineering, Science and Technology, 2005

It is known that lead anodes used in the industrial extraction of copper by electrolysis (electro... more It is known that lead anodes used in the industrial extraction of copper by electrolysis (electrowinning) suffer corrosion as a result of accidental or intended current interruptions. In order to improve understanding of the corrosion and protection of such anodes, the effects of the concentrations of copper, sulphuric acid, cobalt, iron, manganese, chloride and an organic additive (guar) on the corrosion of lead have been studied by means of weight loss tests and surface analysis techniques (X-ray photoelectron spectroscopy, X-ray diffraction, and wavelength dispersive spectroscopy). The rate of corrosion of lead during current interruptions increases with increasing concentration of sulphuric acid and copper, whereas it decreases markedly in the presence of cobalt and iron and, to a lesser extent, in the presence of chloride and the organic additive. Manganese is the only impurity whose presence does not reduce the rate of corrosion; it is also the only element which precipitates in significant amounts on the lead anode surface under the conditions studied. A method is proposed to establish the optimum anodic protection current density during current interruptions in electrowinning cells. Three current density ranges have been found, of which the 'high' protection range could be caused by the degree of compactness acquired by the PbO 2 layer at applied anodic current densities in excess of 60 A m 22 .

Applied Surface Science, 1993