gabriel soares - Academia.edu (original) (raw)
Papers by gabriel soares
Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, 2006
Thermal oxidation of 6H-SiC was investigated by ion beam analysis techniques. The mechanisms of o... more Thermal oxidation of 6H-SiC was investigated by ion beam analysis techniques. The mechanisms of oxygen transport and incorporation were accessed by sequential oxidations in dry O 2 enriched or not in the 18 O isotope and subsequent determinations of the 18 O profiles. After sequential 16 O 2 / 18 O 2 or 18 O 2 / 16 O 2 oxidations of SiC, the 18 O profiles were seen to be markedly different from those observed in Si oxidation, which led to the identification of different mechanisms of oxygen incorporation and transport. The gradual nature of the SiO 2 /SiC interface was also evidenced by the 18 O depth distributions in samples oxidized in a single step in 18 O-enriched O 2 . A probable explanation for this gradual SiO 2 /SiC interface is the formation of C clusters during oxidation.
Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms
The incorporation of water vapor in SiO2 films thermally grown on 6H-SiC(0001) and on Si (001) wa... more The incorporation of water vapor in SiO2 films thermally grown on 6H-SiC(0001) and on Si (001) was investigated using nuclear reaction analyses. Water isotopically enriched in deuterium (2H or D) and in 18O was used. The dependence of incorporated D with the water annealing temperature and initial oxide thickness were inspected. The D amount in SiO2/SiC structures increases continuously with
Materials Science Forum, 2010
Consequences of NO thermal treatments in the properties of dielectric films / SiC structures FCSt... more Consequences of NO thermal treatments in the properties of dielectric films / SiC structures FCStedile 1, a , SA Corrêa 2 , C. Radtke 1 , L. Miotti 3, 4 , IJR Baumvol 3, 4 , ... 162 (1997), p. 321 [2] SA Corrêa, C. Radtke, GV Soares, IJR Baumvol, C. Krug, and FC Stedile: Electrochem. ...
Electrochemical and Solid State Letters, 2008
Presence and Resistance to Wet Etching of Silicon Oxycarbides at the SiO/SiC Interface. [Electroc... more Presence and Resistance to Wet Etching of Silicon Oxycarbides at the SiO/SiC Interface. [Electrochemical and Solid-State Letters 11, H258 (2008)]. Silma A. Corrêa, Cláudio Radtke, Gabriel V. Soares, Israel JR Baumvol, Cristiano Krug, Fernanda C. Stedile. Abstract. ...
Surface & Coatings Technology, 2011
The nanoscale friction of partially oxidized silicon nitride thin films deposited by reactive mag... more The nanoscale friction of partially oxidized silicon nitride thin films deposited by reactive magnetron sputtering was investigated. Post deposition thermal annealing in O 2 , trying to simulate the oxidation by atmospheric oxygen in working conditions, formed a partially oxidized layer at the surface with maximum thickness around 10 nm. Unidirectional sliding tests showed a decrease of the low-load friction coefficients of the sliding pair for the samples annealed in oxygen as compared to the non-annealed ones. The results are discussed on the lights of our extension of the crystal chemistry model, which establishes a relationship between ionic potential and friction coefficient.
Thin Solid Films, 2009
Vanadium carbide thin films were deposited on Si substrates by direct current reactive magnetron ... more Vanadium carbide thin films were deposited on Si substrates by direct current reactive magnetron sputtering from a V target in Ar/CH4 plasma, varying the Ar/CH4 partial pressure ratio and substrate temperature. The films were characterized by glancing angle X-ray diffraction and Rutherford backscattering spectrometry. Well defined crystalline structures were obtained for CH4 content higher than 13%. The increase of substrate
Electrochemical and Solid State Letters, 2009
ABSTRACT
Materials Letters, 2011
Deposition of CN-based films by a novel version of active screen plasma nitriding, aiming at surf... more Deposition of CN-based films by a novel version of active screen plasma nitriding, aiming at surface modification of polymers, is reported. The approach relies on the use of pure graphite as the grid material, which was found to act both as an active screen and as a dry source of carbon atoms for the synthesis of thin films consisting mainly of a stoichiometric CN layer with columnar-type structure and dome-like nanostructured morphology.
Journal of Materials Research, 2009
ABSTRACT High temperature plasma nitriding of yttria-partially-stabilized zirconia in atmospheric... more ABSTRACT High temperature plasma nitriding of yttria-partially-stabilized zirconia in atmospheric pressure microwave plasma was investigated. The morphological, mechanical, and physicochemical characteristics of the resulting nitrided layer were characterized by different methods, such as optical and scanning electron microscopy, microindentation, x-ray diffraction, narrow resonant nuclear reaction profiling, secondary neutral mass spectrometry, and x-ray photoelectron spectroscopy, aiming at investigating the applicability of this highly efficient process for nitriding of ceramics. The structure of the plasma nitrided layer was found to be complex, composed of tetragonal and cubic zirconia, as well as zirconium nitride and oxynitride. The growth rate of the nitrided layer, 4 µm/min, is much higher than that obtained by any other previous nitriding process, whereas a typical 50% increase in Vickers hardness over that of yttria-partially-stabilized zirconia was observed.
Journal of Vacuum Science & Technology A, 2003
We report here on the thermodynamical stability of ultrathin, hafnium-based dielectric films, nam... more We report here on the thermodynamical stability of ultrathin, hafnium-based dielectric films, namely hafnium oxide (HfO 2 ), silicate (HfSi x O y ), and aluminum silicate (AlHf x Si y O z ), deposited on silicon. These materials are promising candidates to replace the well established silicon oxide and oxynitride as gate dielectric materials in advanced Si-based complementary metal-oxidesemiconductor technology. Since there are mandatory requirements on the gate dielectric material, hafnium oxide is currently being modified, by adding silicon and aluminum into the matrix, increasing its thermal stability, and improving its electrical properties. Diffusion-reaction during thermal processing was investigated using isotopic substitution together with ion beam techniques such as Rutherford backscattering spectrometry, narrow nuclear resonance profiling, and nuclear reaction analysis. The chemical changes in the films were accessed by x-ray photoelectron spectroscopy.
Surface & Coatings Technology, 2011
TiN-MoS 2 composite thin films deposited by dc magnetron sputtering with MoS 2 concentrations fro... more TiN-MoS 2 composite thin films deposited by dc magnetron sputtering with MoS 2 concentrations from 3 to 40 at.% were investigated. The elementary composition and the formed compounds were determined before and after wear. The crystalline structure of the composite thin films was accessed and the nature and concentration of the precipitates in the TiN matrix were imaged by transmission electron microscopy. The hardness and elastic moduli of the films were measured by nanoindentation and the elastic strain to failure calculated on the basis of these two magnitudes. The MoS 2 formed in the composite coatings during thin film co-deposition are nanoscopic in size, homogeneously distributed, and mostly amorphous, although part of them are crystalline. The present study does not confirm MoS 2 formation at grain boundaries or TiS formation by substitution of S for N in the TiN matrix. The hardness and elastic strain to failure are appreciably high for the present TiN-MoS 2 thin film composite coatings with MoS 2 concentrations up to 4%. The potential applications are discussed on the basis of these findings.
Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms
Al2O3 films were deposited on Ge substrates by reactive sputtering. Resulting samples were submit... more Al2O3 films were deposited on Ge substrates by reactive sputtering. Resulting samples were submitted to different post-deposition annealings (PDAs) in order to probe composition modifications induced by such treatments. Nuclear reaction profiling (NRP) revealed that O incorporation depends on PDA temperature and on the employed atmosphere (water or oxygen). We also found that O from the gas phase strongly interacts
Journal of Materials Science, 2010
Cereal Chem. 79(3):458-464
Chemistry-a European Journal, 2004
The controlled decomposition of an Ru(0) organometallic precursor dispersed in 1-n-butyl-3-methyl... more The controlled decomposition of an Ru(0) organometallic precursor dispersed in 1-n-butyl-3-methylimidazolium hexafluorophosphate (BMI.PF(6)), tetrafluoroborate (BMI.BF(4)) or trifluoromethane sulfonate (BMI.CF(3)SO(3)) ionic liquids with H(2) represents a simple and efficient method for the generation of Ru(0) nanoparticles. TEM analysis of these nanoparticles shows the formation of superstructures with diameters of approximately 57 nm that contain dispersed Ru(0) nanoparticles with diameters of 2.6+/-0.4 nm. These nanoparticles dispersed in the ionic liquids are efficient multiphase catalysts for the hydrogenation of alkenes and benzene under mild reaction conditions (4 atm, 75 degrees C). The ternary diagram (benzene/cyclohexene/BMI.PF(6)) indicated a maximum of 1 % cyclohexene concentration in BMI.PF(6), which is attained with 4 % benzene in the ionic phase. This solubility difference in the ionic liquid can be used for the extraction of cyclohexene during benzene hydrogenation by Ru catalysts suspended in BMI.PF(6). Selectivities of up to 39 % in cyclohexene can be attained at very low benzene conversion. Although the maximum yield of 2 % in cyclohexene is too low for technical applications, it represents a rare example of partial hydrogenation of benzene by soluble transition-metal nanoparticles.
Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms
Low energy ion scattering (LEIS) and X-ray photoelectron spectroscopy (XPS) were used to access t... more Low energy ion scattering (LEIS) and X-ray photoelectron spectroscopy (XPS) were used to access the elemental composition and chemical bonding characteristics of polystyrene (PS) surfaces sequentially treated by corona and glow discharge (plasma) processing in N 2 /H 2 ambient. The latter has shown activity as suppressor of pathogenic Staphylococcus epidermidis biofilms. LEIS indicated that oxygen from the corona discharge process is progressively replaced by nitrogen at the PS surface. XPS shows C@N and NAC@O chemical groups as significant inhibitors of bacterial adhesion, suggesting application in medical devices.
Materials Science and Engineering B-advanced Functional Solid-state Materials, 2004
HfSiON and HfSiO films deposited on Si(100) by reactive sputtering followed by UV/ozone oxidation... more HfSiON and HfSiO films deposited on Si(100) by reactive sputtering followed by UV/ozone oxidation were submitted to different sequential rapid thermal annealings in N2 and/or O2 atmospheres. The thermal stability of the system was addressed by determining the atomic transport and exchange of the involved chemical species using nuclear reaction analysis, nuclear resonance profiling and X-ray photoelectron spectroscopy. We investigated
Journal of The Electrochemical Society, 2004
ABSTRACT
Scripta Materialia, 2010
The effect of hydrogen on plasma post-oxidation following plasma nitriding of a ferrous alloy was... more The effect of hydrogen on plasma post-oxidation following plasma nitriding of a ferrous alloy was investigated. The increase in the hydrogen concentration in the plasma progressively reduces the hematite/magnetite concentration ratio in the outermost oxide layer down to zero at 25% H 2 concentration. Atomic hydrogen originating from scission of hydrogen molecules in the plasma leads to reduction of Fe(III) in hematite into Fe(II) in magnetite by controlling the gas mixture reduction potential.
Materials Science and Engineering: C, 2009
Here we describe the use of low energy plasma immersion with active screen as a convenient approa... more Here we describe the use of low energy plasma immersion with active screen as a convenient approach for polypropylene (PP) surface modification. Employing a stainless steel cathodic cage coated with carbon in order to prevent the sputtering of iron from the grid and its deposition onto the polymer sample, the physical chemical properties of PP surface could be effectively modified through the plasma-induced incorporation/ formation of nitrogen-and oxygen-containing species. The areal densities of these elements depended on the plasma excitation source, as determined by Rutherford backscattering spectrometry (RBS). Newly formed C-O, C-N, and CfO/OfC-O/N-CfO bonds along with C-C linkages from the PP backbone were identified at the near surface region of the specimens by X-ray photoelectron spectroscopy (XPS). The insertion of such polar reactive functionalities was further confirmed by a substantial decrease in the water contact angle upon plasma treatment. Scanning electron microscopy (SEM) analysis revealed that while no major changes in the morphology occur upon DC plasma treatments as compared to untreated samples, the use of pulsed plasma consistently leads to the formation of cracks at the surface. The herein reported approach is an attractive tool for environmental friendly low-cost surface engineering of novel materials.
Electrochemical and Solid State Letters, 2010
Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, 2006
Thermal oxidation of 6H-SiC was investigated by ion beam analysis techniques. The mechanisms of o... more Thermal oxidation of 6H-SiC was investigated by ion beam analysis techniques. The mechanisms of oxygen transport and incorporation were accessed by sequential oxidations in dry O 2 enriched or not in the 18 O isotope and subsequent determinations of the 18 O profiles. After sequential 16 O 2 / 18 O 2 or 18 O 2 / 16 O 2 oxidations of SiC, the 18 O profiles were seen to be markedly different from those observed in Si oxidation, which led to the identification of different mechanisms of oxygen incorporation and transport. The gradual nature of the SiO 2 /SiC interface was also evidenced by the 18 O depth distributions in samples oxidized in a single step in 18 O-enriched O 2 . A probable explanation for this gradual SiO 2 /SiC interface is the formation of C clusters during oxidation.
Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms
The incorporation of water vapor in SiO2 films thermally grown on 6H-SiC(0001) and on Si (001) wa... more The incorporation of water vapor in SiO2 films thermally grown on 6H-SiC(0001) and on Si (001) was investigated using nuclear reaction analyses. Water isotopically enriched in deuterium (2H or D) and in 18O was used. The dependence of incorporated D with the water annealing temperature and initial oxide thickness were inspected. The D amount in SiO2/SiC structures increases continuously with
Materials Science Forum, 2010
Consequences of NO thermal treatments in the properties of dielectric films / SiC structures FCSt... more Consequences of NO thermal treatments in the properties of dielectric films / SiC structures FCStedile 1, a , SA Corrêa 2 , C. Radtke 1 , L. Miotti 3, 4 , IJR Baumvol 3, 4 , ... 162 (1997), p. 321 [2] SA Corrêa, C. Radtke, GV Soares, IJR Baumvol, C. Krug, and FC Stedile: Electrochem. ...
Electrochemical and Solid State Letters, 2008
Presence and Resistance to Wet Etching of Silicon Oxycarbides at the SiO/SiC Interface. [Electroc... more Presence and Resistance to Wet Etching of Silicon Oxycarbides at the SiO/SiC Interface. [Electrochemical and Solid-State Letters 11, H258 (2008)]. Silma A. Corrêa, Cláudio Radtke, Gabriel V. Soares, Israel JR Baumvol, Cristiano Krug, Fernanda C. Stedile. Abstract. ...
Surface & Coatings Technology, 2011
The nanoscale friction of partially oxidized silicon nitride thin films deposited by reactive mag... more The nanoscale friction of partially oxidized silicon nitride thin films deposited by reactive magnetron sputtering was investigated. Post deposition thermal annealing in O 2 , trying to simulate the oxidation by atmospheric oxygen in working conditions, formed a partially oxidized layer at the surface with maximum thickness around 10 nm. Unidirectional sliding tests showed a decrease of the low-load friction coefficients of the sliding pair for the samples annealed in oxygen as compared to the non-annealed ones. The results are discussed on the lights of our extension of the crystal chemistry model, which establishes a relationship between ionic potential and friction coefficient.
Thin Solid Films, 2009
Vanadium carbide thin films were deposited on Si substrates by direct current reactive magnetron ... more Vanadium carbide thin films were deposited on Si substrates by direct current reactive magnetron sputtering from a V target in Ar/CH4 plasma, varying the Ar/CH4 partial pressure ratio and substrate temperature. The films were characterized by glancing angle X-ray diffraction and Rutherford backscattering spectrometry. Well defined crystalline structures were obtained for CH4 content higher than 13%. The increase of substrate
Electrochemical and Solid State Letters, 2009
ABSTRACT
Materials Letters, 2011
Deposition of CN-based films by a novel version of active screen plasma nitriding, aiming at surf... more Deposition of CN-based films by a novel version of active screen plasma nitriding, aiming at surface modification of polymers, is reported. The approach relies on the use of pure graphite as the grid material, which was found to act both as an active screen and as a dry source of carbon atoms for the synthesis of thin films consisting mainly of a stoichiometric CN layer with columnar-type structure and dome-like nanostructured morphology.
Journal of Materials Research, 2009
ABSTRACT High temperature plasma nitriding of yttria-partially-stabilized zirconia in atmospheric... more ABSTRACT High temperature plasma nitriding of yttria-partially-stabilized zirconia in atmospheric pressure microwave plasma was investigated. The morphological, mechanical, and physicochemical characteristics of the resulting nitrided layer were characterized by different methods, such as optical and scanning electron microscopy, microindentation, x-ray diffraction, narrow resonant nuclear reaction profiling, secondary neutral mass spectrometry, and x-ray photoelectron spectroscopy, aiming at investigating the applicability of this highly efficient process for nitriding of ceramics. The structure of the plasma nitrided layer was found to be complex, composed of tetragonal and cubic zirconia, as well as zirconium nitride and oxynitride. The growth rate of the nitrided layer, 4 µm/min, is much higher than that obtained by any other previous nitriding process, whereas a typical 50% increase in Vickers hardness over that of yttria-partially-stabilized zirconia was observed.
Journal of Vacuum Science & Technology A, 2003
We report here on the thermodynamical stability of ultrathin, hafnium-based dielectric films, nam... more We report here on the thermodynamical stability of ultrathin, hafnium-based dielectric films, namely hafnium oxide (HfO 2 ), silicate (HfSi x O y ), and aluminum silicate (AlHf x Si y O z ), deposited on silicon. These materials are promising candidates to replace the well established silicon oxide and oxynitride as gate dielectric materials in advanced Si-based complementary metal-oxidesemiconductor technology. Since there are mandatory requirements on the gate dielectric material, hafnium oxide is currently being modified, by adding silicon and aluminum into the matrix, increasing its thermal stability, and improving its electrical properties. Diffusion-reaction during thermal processing was investigated using isotopic substitution together with ion beam techniques such as Rutherford backscattering spectrometry, narrow nuclear resonance profiling, and nuclear reaction analysis. The chemical changes in the films were accessed by x-ray photoelectron spectroscopy.
Surface & Coatings Technology, 2011
TiN-MoS 2 composite thin films deposited by dc magnetron sputtering with MoS 2 concentrations fro... more TiN-MoS 2 composite thin films deposited by dc magnetron sputtering with MoS 2 concentrations from 3 to 40 at.% were investigated. The elementary composition and the formed compounds were determined before and after wear. The crystalline structure of the composite thin films was accessed and the nature and concentration of the precipitates in the TiN matrix were imaged by transmission electron microscopy. The hardness and elastic moduli of the films were measured by nanoindentation and the elastic strain to failure calculated on the basis of these two magnitudes. The MoS 2 formed in the composite coatings during thin film co-deposition are nanoscopic in size, homogeneously distributed, and mostly amorphous, although part of them are crystalline. The present study does not confirm MoS 2 formation at grain boundaries or TiS formation by substitution of S for N in the TiN matrix. The hardness and elastic strain to failure are appreciably high for the present TiN-MoS 2 thin film composite coatings with MoS 2 concentrations up to 4%. The potential applications are discussed on the basis of these findings.
Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms
Al2O3 films were deposited on Ge substrates by reactive sputtering. Resulting samples were submit... more Al2O3 films were deposited on Ge substrates by reactive sputtering. Resulting samples were submitted to different post-deposition annealings (PDAs) in order to probe composition modifications induced by such treatments. Nuclear reaction profiling (NRP) revealed that O incorporation depends on PDA temperature and on the employed atmosphere (water or oxygen). We also found that O from the gas phase strongly interacts
Journal of Materials Science, 2010
Cereal Chem. 79(3):458-464
Chemistry-a European Journal, 2004
The controlled decomposition of an Ru(0) organometallic precursor dispersed in 1-n-butyl-3-methyl... more The controlled decomposition of an Ru(0) organometallic precursor dispersed in 1-n-butyl-3-methylimidazolium hexafluorophosphate (BMI.PF(6)), tetrafluoroborate (BMI.BF(4)) or trifluoromethane sulfonate (BMI.CF(3)SO(3)) ionic liquids with H(2) represents a simple and efficient method for the generation of Ru(0) nanoparticles. TEM analysis of these nanoparticles shows the formation of superstructures with diameters of approximately 57 nm that contain dispersed Ru(0) nanoparticles with diameters of 2.6+/-0.4 nm. These nanoparticles dispersed in the ionic liquids are efficient multiphase catalysts for the hydrogenation of alkenes and benzene under mild reaction conditions (4 atm, 75 degrees C). The ternary diagram (benzene/cyclohexene/BMI.PF(6)) indicated a maximum of 1 % cyclohexene concentration in BMI.PF(6), which is attained with 4 % benzene in the ionic phase. This solubility difference in the ionic liquid can be used for the extraction of cyclohexene during benzene hydrogenation by Ru catalysts suspended in BMI.PF(6). Selectivities of up to 39 % in cyclohexene can be attained at very low benzene conversion. Although the maximum yield of 2 % in cyclohexene is too low for technical applications, it represents a rare example of partial hydrogenation of benzene by soluble transition-metal nanoparticles.
Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms
Low energy ion scattering (LEIS) and X-ray photoelectron spectroscopy (XPS) were used to access t... more Low energy ion scattering (LEIS) and X-ray photoelectron spectroscopy (XPS) were used to access the elemental composition and chemical bonding characteristics of polystyrene (PS) surfaces sequentially treated by corona and glow discharge (plasma) processing in N 2 /H 2 ambient. The latter has shown activity as suppressor of pathogenic Staphylococcus epidermidis biofilms. LEIS indicated that oxygen from the corona discharge process is progressively replaced by nitrogen at the PS surface. XPS shows C@N and NAC@O chemical groups as significant inhibitors of bacterial adhesion, suggesting application in medical devices.
Materials Science and Engineering B-advanced Functional Solid-state Materials, 2004
HfSiON and HfSiO films deposited on Si(100) by reactive sputtering followed by UV/ozone oxidation... more HfSiON and HfSiO films deposited on Si(100) by reactive sputtering followed by UV/ozone oxidation were submitted to different sequential rapid thermal annealings in N2 and/or O2 atmospheres. The thermal stability of the system was addressed by determining the atomic transport and exchange of the involved chemical species using nuclear reaction analysis, nuclear resonance profiling and X-ray photoelectron spectroscopy. We investigated
Journal of The Electrochemical Society, 2004
ABSTRACT
Scripta Materialia, 2010
The effect of hydrogen on plasma post-oxidation following plasma nitriding of a ferrous alloy was... more The effect of hydrogen on plasma post-oxidation following plasma nitriding of a ferrous alloy was investigated. The increase in the hydrogen concentration in the plasma progressively reduces the hematite/magnetite concentration ratio in the outermost oxide layer down to zero at 25% H 2 concentration. Atomic hydrogen originating from scission of hydrogen molecules in the plasma leads to reduction of Fe(III) in hematite into Fe(II) in magnetite by controlling the gas mixture reduction potential.
Materials Science and Engineering: C, 2009
Here we describe the use of low energy plasma immersion with active screen as a convenient approa... more Here we describe the use of low energy plasma immersion with active screen as a convenient approach for polypropylene (PP) surface modification. Employing a stainless steel cathodic cage coated with carbon in order to prevent the sputtering of iron from the grid and its deposition onto the polymer sample, the physical chemical properties of PP surface could be effectively modified through the plasma-induced incorporation/ formation of nitrogen-and oxygen-containing species. The areal densities of these elements depended on the plasma excitation source, as determined by Rutherford backscattering spectrometry (RBS). Newly formed C-O, C-N, and CfO/OfC-O/N-CfO bonds along with C-C linkages from the PP backbone were identified at the near surface region of the specimens by X-ray photoelectron spectroscopy (XPS). The insertion of such polar reactive functionalities was further confirmed by a substantial decrease in the water contact angle upon plasma treatment. Scanning electron microscopy (SEM) analysis revealed that while no major changes in the morphology occur upon DC plasma treatments as compared to untreated samples, the use of pulsed plasma consistently leads to the formation of cracks at the surface. The herein reported approach is an attractive tool for environmental friendly low-cost surface engineering of novel materials.
Electrochemical and Solid State Letters, 2010