Influence of ambient gas on the growth and properties of porous tin-doped indium oxide thin films made by pulsed laser deposition

The laser ablation method was used for depositing porous nanocrystalline indium-tin oxide thin films for gas sensing applications. Samples were prepared at different pressures using three gases (O-2, 0.8N(2):0.2O(2), N-2) and heat-treated in the same atmosphere used for the ablation process. X-ray diffraction results show that the films are not oriented and the grain sizes are in the range between 15 and 40 nm. The grains are round shaped for all samples and the porosity of the films increases with the deposition pressure. The degree of sintering after heat treatment increases for lower oxygen concentrations, generating fractures on the surface of the samples. Film thicknesses are in the range of I pm for all gases as determined from scanning electron microscopy cross-sections. Electrical resistance varies between 36.3 ohm for the film made at 10 Pa pressure in N-2 until 9.35 x 10(7) ohm for the film made at 100 Pa in O-2. (C) 2007 Elsevier B.V. All rights reserved.

Low-temperature, self-nucleated growth of indium-tin oxide nanostructures by pulsed laser deposition on amorphous substrates

Indium-tin oxide nanostructures were deposited by excimer laser ablation in a nitrogen atmosphere using catalyst-free oxidized silicon substrates at 500 degrees C. Up to 1 mbar, nanowires grew by the vapor-liquid-solid (VLS) mechanism, with the amount of liquid material decreasing as the deposition pressure increased. The nanowires present the single-crystalline cubic bixbyite structure, oriented < 100 >. For the highest pressure used, pyramids were formed and no sign of liquid material could be observed, indicating that these structures grew by a vapor-solid mechanism. (c) 2006 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Influence of strains and defects on ferroelectric and dielectric properties of thin-film barium-strontium titanates

Pristine, W and Mn 1% doped Ba(0.6)Sr(0.4)TiO(3) epitaxial thin films grown on the LaAlO(3) substrate were deposited by pulsed laser deposition (PLD). Dielectric and ferroelectric properties were determined by the capacitance measurements and X-ray diffraction was used to determine both residual elastic strains and defect-related inhomogeneous strains-by analyzing diffraction line shifts and line broadening, respectively. We found that both elastic and inhomogeneous strains are affected by doping. This strain correlates with the change in Curie-Weiss temperature and can qualitatively explain changes in dielectric loss. To explain the experimental findings, we model the dielectric and ferroelectric properties of interest in the framework of the Landau-Ginzburg-Devonshire thermodynamic theory. As expected, an, elastic-strain contribution due to the epilayer-substrate misfit has an important influence on the free-energy. However, additional terms that correspond to the defect-related inhomogeneous strain had to be introduced to fully explain the measurements.

Dye-sensitized solar cell architecture based on indium-tin oxide nanowires coated with titanium dioxide

A new architecture for dye-sensitized solar cells is employed, based on a nanostructured transparent conducting oxide protruding from the substrate, covered with a separate active oxide layer. The objective is to decrease electron-hole recombination. The concept was tested by growing branched indium-tin oxide nanowires on glass using pulsed laser deposition followed by deposition of a sputtered titanium dioxide layer covering the wires. The separation of charge generation and charge transport functions opens many possibilities for dye-sensitized solar cell optimization. (c) 2007 Acta Materialia. Inc. Published by Elsevier Ltd. All rights reserved.

Ferroelectric SBN thin films grown by an SBN/Bi2O3 PLD sequential process

Ferroelectric SrBi2Nb2O9 (SBN) thin films were prepared by pulsed laser deposition (PLD) on Pt/Ti/SiO2/Si(100) using a sequential deposition process from two SBN and Bi2O3 targets. This route allows for bismuth enrichment of the film composition in order to improve the ferroelectric characteristics. Structural and microstructural characterizations were performed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The composition of films and targets was determined by energy dispersive X-ray spectrometry (EDX). The deposition temperature, which provided well-crystallized layered perovskite SBN phase films in situ, was found to be 700°C. The results were compared with those obtained for SBN films deposited at 400°C and then crystallized ex situ. For an ex situ annealing temperature of 750°C, a remanent polarization value (Pr) of 23.2 μc/cm2 and a coercive field (Ec) of 112 kV/cm were measured. © 2001 Elsevier Science Ltd. All rights reserved.

Properties of individual YBCO layers in a two-layered design for energy-efficient digital data cables

We are developing two-layered Yttrium Barium Copper Oxide (YBCO) thin film structures for energy efficient data links for superconducting electronics and present the results of their property measurements. High temperature superconductors (HTS) are advantageous for the implementation of energy-efficient cables interconnecting low temperature superconductor-based circuits and other cryogenic electronics circuits at higher temperature stages. The advantages of the HTS cables come from their low loss and low dispersion properties, allowing ballistic transfer of low power signals with very high bandwidth, low heat conduction and negligible inter-line crosstalk. The microstrip line cable geometry for typical materials is a two-layered film, in which the two superconducting layers are separated by an insulation layer with a minimized permittivity. We have made a proof of concept design of two YBCO films grown by pulsed laser deposition and then assembled into a sandwich with uniform insulating interlayer of tens of micrometers thick. We report on results obtained from such systems assembled in different ways. Structural and electromagnetic properties have been examined on individual films and on the corresponding sandwich composite. © 2013 IEEE.

Propriedades de transporte eletrônico em filmes finos policristalinos de diboreto de magnésio (MGB IND.2') analisados pelo modelo de Bloch-Grüneisen

Pós-graduação em Ciência e Tecnologia de Materiais - FC

Hydroxyapatite deposition study through polymeric process on commercially pure Ti surfaces modified by laser beam irradiation

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Morphology changes induced by laser irradiation on disperse red 13 films prepared by physical vapor deposition

Surface morphology changes induced by argon laser irradiation (514 nm) on disperse red 13 (DR13) films prepared by physical vapor deposition (PVD) were investigated. Atomic force microscopy was used to characterize the irradiated sample for different periods of irradiation. Needle-shape structures are observed which are attributed to the symmetry of DR13 molecules. The film becomes increasingly closely packed with the irradiation, with lower root mean square roughness for long exposure times. This is due to photoisomerization of DR13 molecules and probably heating of the sample, which can provide the required mobility for the molecular rearrangement. The rearrangement is such that voids in the film are filled in upon irradiating the sample, thus decreasing the film roughness and increasing the packing.

Comparative in vivo study of commercially pure Ti implants with surfaces modified by laser with and without silicate deposition: Biomechanical and scanning electron microscopy analysis

The purpose of this study was to evaluate commercially pure titanium implant surfaces modified by laser beam (LS) and LS associated with sodium silicate (SS) deposition, and compare them with machined surface (MS) and dual acid-etching surfaces (AS) modified. Topographic characterization was performed by scanning electron microscopy-X-ray energy dispersive spectroscopy (SEM-EDX), and by mean roughness measurement before surgery. Thirty rabbits received 60 implants in their right and left tibias. One implant of each surface in each tibia. The implants were removed by reverse torque for vivo biomechanical analysis at 30, 60, and 90 days postoperative. In addition, the surface of the implants removed at 30 days postoperative was analyzed by SEM-EDX. The topographic characterization showed differences between the analyzed surfaces, and the mean roughness values of LS and SS were statistically higher than AS and MS. At 30 days, values removal torque LS and SS groups showed a statistically significant difference (p < 0.05) when compared with MS and AS. At 60 days, groups LS and SS showed statistically significant difference (p < 0.05) when compared with MS. At 90 days, only group SS presented statistically higher (p < 0.05) in comparison with MS. The authors can conclude that physical chemistry properties and topographical of LS and SS implants increases bone-implant interaction and provides higher degree of osseointegration when compared with MS and AS. © 2012 Wiley Periodicals, Inc.

Commercially pure titanium implants with surfaces modified by laser beam with and without chemical deposition of apatite. Biomechanical and topographical analysis in rabbits

Objectives: The purpose of this study was to evaluate the surfaces of commercially pure titanium (cp Ti) implants modified by laser beam (LS), without and with hydroxyapatite deposition by the biomimetic method (HAB), without (HAB) and with thermal treatment (HABT), and compare them with implants with surfaces modified by acid treatment (AS) and with machined surfaces (MS), employing topographical and biomechanics analysis. Methods: Forty-five rabbits received 75 implants. After 30, 60, and 90 days, the implants were removed by reverse torque and the surfaces were topographically analyzed. Results: At 30 days, statistically significant difference (P < 0.05) was observed among all the surfaces and the MS, between HAB/HABT and AS and between HAB and LS. At 60 days, the reverse torque of LS, HAB, HABT, and AS differed significantly from MS. At 90 days, difference was observed between HAB and MS. The microtopographic analysis revealed statistical difference between the roughness of LS, HAB, and HABT when compared with AS and MS. Conclusions: It was concluded that the implants LS, HAB, and HABT presented physicochemical and topographical properties superior to those of AS and MS and favored the osseointegration process in the shorter periods. In addition, HAB showed the best results when compared with other surfaces. © 2012 John Wiley & Sons A/S.

Histometric analysis and topographic characterization of cp Ti implants with surfaces modified by laser with and without silica deposition

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

Analysis of implants with laser irradiated surface and silicate deposition

Objectives: the purpose of this study was to evaluate the surfaces of commercially pure titanium (cpTi) implants surface modified by laser beam (LS), by laser beam associated with sodium silicate deposition (SS) and compare them with surfaces modified by dual-acid etched (AS) and with machined surface (MS). Methods: thirty rabbits received two implants each (one for each tibia). After 30, 60 and 90 days postoperative, the implants were removed by reverse torque for biomechanical analysis and surfaces were analyzed by scanning electron microscopy (SEM) and X-ray energy dispersive spectroscopy (EDS). Results: the mean values of reverse torque at 30, 60 and 90 days postoperative were respectively 24.60, 43.60 e 60.40 N.cm to MS, 43.00, 68.20 e 63.80 N.cm to AS group, 59.80, 76.60 e 78.00 N.cm to LS group and 63.00, 75.40 e 76.60 N.cm to SS group. At 30 days, LS and SS groups showed statistically significant difference (p<0.05) compared to the other groups. At 60 days, LS and SS groups showed statistically significant difference (p<0.05) when compared to MS. Conclusions: it was concluded that SL and SS implants' biomechanical and topographical properties increased bone-implant interaction when compared to the AS and MS implants.

Analyse titanium surface irradiated with laser, with and without deposited of durapatite

OBJETIVO: Estudar a superfície de implantes osseointegráveis utilizando discos de titânio irradiados com feixe de laser. MÉTODOS: A amostra foi irradiada com feixes de laser de alta intensidade (Nd-YAG), posteriormente depositado hidróxiapatita e submetido a tratamento térmico. Foi analisada sob MEV (Microscópio Eletrônico de Varredura) e realizada análise morfológica qualitativa com microfotografias em vários aumentos. RESULTADOS: A superfície irradiada com laser apresentou deformidade superficial e característica isomórfica; a aplicação de hidroxiapatita pelo método de biomimético aumentou quantitativamente a área da superfície de titânio. CONCLUSÃO: A deposição de hidroxiapatita apresentou melhor característica isomórfica e aumento quantitativo da área superficial estudada, a amostra demonstrou características não encontradas nos implantes disposto no mercado.

Laser ablation in titanium implants followed by biomimetic hydroxyapatite coating: Histomorphometric study in rabbits

Titanium surface texture and chemistry modification successfully improves the host response and consequently the bone-to-implant contact surrounding dental implants. The aim of the present study was to investigate, using histomorphometrical-analysis, the effects of titanium surface modification by laser-ablation (Nd:YAG) followed by thin chemical deposition of HA. Forty-eight rabbits received one implant by tibiae of AS-machined (MS), laser-modified (LMS), or biomimetic hydroxyapatite-coated (HA) surface. Bone-to-implant contact (BIC) and bone area (BBT) were evaluated after 4, 8, and 12 weeks, at cortical and cancellous regions. Average BIC in the cortical region was higher (P < 0.001) on the LMS and HA implants for all periods, with no differences between LMS and HA. For the cancellous area, the LMS and HA implants showed higher (P < 0.01) BIC than MS at the initial periods. The LMS and HA showed similar values in the cortical region, but a tendency of higher values for HA in the cancellous region was observed in all periods. For the BBT, the differences were found only between HA and MS after 4 weeks in the cortical region (P < 0.05), and after 12 weeks in the cancellous area (P < 0.05). Our results showed that HA biomimetic coating preceded by laser treatment induced the contact osteogenesis and allowed the formation of a more stable boneimplant interface, even in earlier periods. Microsc. Res. Tech., 2012. (C) 2012 Wiley Periodicals, Inc.