© 2024, Escola de Minas. All rights reserved.A Hollow Cathode Plasma Enhanced Chemical Vapor Deposition (HC-PECVD) reactor was used to deposit silver doped Diamond-Like Carbon (Ag-DLC) films on Ti6Al4V alloy employing two methodologies: i) producing a silicon interlayer, using tetramethylsilane (TMS) as silicon precursor, varying the argon flow of the hollow cathode; and ii) carbonitriding the substrate. Profilometry, Raman, and Secondary Ion Mass Spectrometry (SIMS), as well as nanohardness, micro-scratch, scratch, and VDI 3198 indentation tests were used to evaluate the characteristics of the films and their adhesion on the substrates. The results demonstrated that the argon flow can be used for tuning the Ag-DLC film’s hardness, toughness, and adherence on silicon interlayers. The carbonitriding process, in turn, provided an improvement in the film toughness compared with non-carbonitrided samples. Considering the lower cost and easier handling of N2 compared to the silicon precursors commonly available (TMS, HDMSO, SiH4, etc.), the carbonitriding process proved more appropriate to improve the adhesion of the Ag-DLC films on the Ti6Al4V alloy.

© 2023 by the authors.In the presented study, a novel approach for thermal atomic layer deposition (ALD) of Al2O3 thin films using plasma-activated water (PAW) as a co-reactant, replacing traditionally employed deionized (DI) water, is introduced. Utilizing ex situ PAW achieves up to a 16.4% increase in the growth per cycle (GPC) of Al2O3 films, consistent with results from plasma-enhanced atomic layer deposition (PEALD). Time-resolved mass spectrometry (TRMS) revealed disparities in CH4 partial pressures between TMA reactions with DI water and PAW, with PAW demonstrating enhanced reactivity. Reactive oxygen species (ROS), namely H2O2 and O3, are posited to activate Si(100) substrate sites, thereby improving GPC and film quality. Specifically, Al2O3 films grown with PAW pH = 3.1 displayed optimal stoichiometry, reduced carbon content, and an expanded bandgap. This study thus establishes “PAW-ALD” as a descriptor for this ALD variation and highlights the significance of comprehensive assessments of PAW in ALD processes.

© 2023 Elsevier LtdSurface acoustic wave (SAW) sensors enhanced by a graphenic sensitive layer offer improved electrical response uniformity, and recent research has explored their potential for use in point-of-care platforms. These devices offer a unique combination of cost effectiveness, ease of handling, manufacturability, and remarkable sensor performance. This article summarizes the latest advancements in SAW sensors with graphenic-based nanomaterials, including their fabrication, operation mechanisms, and properties. Several recent studies are reviewed and compared to conventional SAW sensors. Furthermore, the challenges and prospects of using graphenic-based structures to enhance SAW devices and produce rapid actionable results are discussed.

© 2023AlGaN thin films with different Al content were grown via reactive magnetron sputtering onto glass substrates using independent Al and Ga targets. The quality of the films was analyzed using X-ray diffraction, Raman spectroscopy, energy dispersive spectroscopy, and UV-Vis spectrophotometry. The results show that the Al content can be effectively controlled by tuning the power ratio applied to the independent targets in different absolute situations. Moreover, all produced samples presented only wurtzite structure without indication of other phases on both X-ray diffraction and Raman spectroscopy analyses. Overall, the properties of the films had a strong correlation with the composition, such as the expected blue shift of the optical bandgap and the Raman phonon modes, and the lattice cell expansion with increasing Al content. In addition, a higher c-orientation texture together with a sharper diffraction peak were observed for samples with more Al.

© 2023 by the authors.In this study, we report the use of a radiofrequency plasma-assisted chemical vapor deposition (RF-CVD) system with a hollow cathode geometry to hydrogenate anatase TiO2 thin films. The goal was to create black TiO2 films with improved light absorption capabilities. The initial TiO2 was developed through magnetron sputtering, and this study specifically investigated the impact of hollow cathode hydrogen plasma (HCHP) treatment duration on the crucial characteristics of the resulting black TiO2 films. The HCHP treatment effectively created in-bandgap states in the TiO2 structure, leading to enhanced light absorption and improved conductivity. Morphological analysis showed a 24% surface area increase after 15 min of treatment. Wettability and surface energy results displayed nonlinear behavior, highlighting the influence of morphology on hydrophilicity improvement. The anatase TiO2 phase remained consistent, as confirmed by diffractograms. Raman analysis revealed structural alterations and induced lattice defects. Treated samples exhibited outstanding photodegradation performance, removing over 45% of methylene blue dye compared to ~25% by the pristine TiO2 film. The study emphasized the significant impact of 15-min hydrogenation on the HCHP treatment. The research provided valuable insights into the role of hydrogenation time using the HCHP treatment route on anatase TiO2 thin films and demonstrated the potential of the produced black TiO2 thin films for photocatalytic applications.

© 2023 The Author(s)We report a joint experimental and theoretical study of the structural and vibrational properties of C-type bulk Y2O3 under hydrostatic compression. The combination of high-pressure X-ray diffraction and Raman scattering experimental measurements with ab initio theoretical calculations on bulk Y2O3 allows us to confirm the cubic (C-type) – monoclinic (B-type) – trigonal (A-type) phase transition sequence on the upstroke and the trigonal-monoclinic phase transition on the downstroke. This result reconciles with the results already found in related rare-earth sesquioxides of cations with similar ionic radii as Y, such as Ho2O3 and Dy2O3, and ends with the controversy regarding the existence of the intermediate monoclinic phase between the cubic and trigonal phases in pure bulk Y2O3 on the upstroke. As a byproduct, the good agreement between experimental and calculated results allows us to use extensive theoretical data to discuss the structural and vibrational behavior of the three phases of Y2O3 under compression, thus allowing a more detailed understanding of the effect of pressure on rare-earth sesquioxides than previous studies.

© 2023, The Author(s), under exclusive licence to the Korean Fiber Society.This work presents permethrin (15%)-based monomers polymerisation in polyamide fabrics using hybrid corona–dielectric barrier discharge (DBD) to potentiate insect–parasite repellency functionalities in polyamide fabrics. First of all, the electric characterisation of the discharge was made using the Lissajous figure method for determining the plasma dosage (2841 W min m−2). Before the polymerisation process, the polyamide fabric was activated by DBD discharge, operating at 23 kHz and voltage amplitude of 12.5 kV in atmospheric pressure. After that, the polymerisation process is initiated by injecting permethrin into the system, maintaining the operational parameters used in the activation process. The non-activated and activated polyamide fabrics measured the static and dynamic contact angle, showing a variation from 120° (non-activated) to 34° (immediately after plasma activation). The chemical structure of synthesised permethrin was evaluated by Fourier transformed infrared (FTIR) spectroscopy to confirm the polymerisation (deposition) of permethrin on the fabric surface; it is possible to observe the 648 cm−1 bands that are associated with asymmetric vibration of the C–Cl bonds, but most evident change occurs at 1045 cm−1, which is associated with cyclopropyl group vibrations. Field emission scanning electron microscopy (FESEM) analysis was used to evaluate the possible degradation of the fabric surface when exposed to plasma activation and the homogeneity of the permethrin coating in the fibres after the polymerisation. The energy dispersive spectrometer (EDS) was used to confirm the polymerisation and the distribution of the permethrin in the fabric.

© 2023 Universidade Federal de Sao Carlos. All rights reserved.This work reports on the properties of GaN films grown by reactive magnetron sputtering onto glass substrate kept at relatively low temperature (400°C), using different RF power applied to the Ga target. Their structural, morphological, vibrational and optical properties were characterized by X-ray diffraction, atomic force and scanning electron microscopies, Raman spectroscopy and UV-vis spectrophotometry. The films have wurtzite phase with strong preferential orientation in the c-axis direction. Moreover, two clear contributions to the (0002) diffraction peak could be found, indicating the presence of two different morphologies, which were discussed in terms of the formation of an intermediate layer between the substrate and a dominating columnar-like microstructured film.

© 2023 Universidade Federal de Sao Carlos. All rights reserved.In this work, a thermal plasma-based ablation test system was used to evaluate the ablative performance of the EPDM composite. The system produces a high enthalpy plasma jet generated by a plasma (DC) torch, operating at atmospheric pressure using compressed air as working gas, enabling the variation of the thermal flux concerned with the studied EPDM composites. The samples were characterized using Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), Fourier-Transform Infrared spectroscopy (FTIR), and Thermogravimetric Analysis (TGA) to investigate the morphology, mass-loss rate, the reaction layer (char formation), and chemical changes of the samples for each thermal flux. For a complete evaluation, the thermal fluxes were varied in 0.30, 0.45, 0.60, 0.75, and 0.90 MW/m2 and for each thermal flux, disk-shape samples remained exposed to the plasma jet for 10s. During the plasma jet exposure time, the temperatures of the surface and the back of the samples were collected to verify the formed char layer’s insulator capacity and the samples’ thermal diffusivity for each experimental condition. The mass loss is continuous under the thermal fluxes of 0.30 and 0.45 MW/m2, stabilizing at 60% until 0.75 MW/m2. The formed char layer begins to lose its protective capacity, evidenced by the size decrease (from 800 µm to 700 µm), due to the ablation process of the reaction layer from the thermal flux of 0.90 MW/m2

© 2022, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.Thermal plasma-assisted processing is an effective process for the synthesis of gas (CO and H2) and carbonaceous materials production from industrial waste. In this paper, a DC plasma torch designed with two vortices chambers has been developed, and its characteristics have been experimentally tested. The plasma torch operates with different plasma working gases, including steam. The results of coal tar pitch (CTP) processing will be presented as a possible ecological application. CTP is a waste from the steel industry mainly composed of polycyclic aromatic hydrocarbons. The experimental results will be discussed with thermodynamic calculations and numerical simulation of the heat and mass transfer in the DC plasma torch and the chemical reaction chamber. The simulations were carried out to clarify the regions of gas flow and temperatures for producing synthesis gas and carbon nanomaterial. The results enable one to predict the produced gas composition and carbon nanomaterial properties. The physicochemical properties of carbon nanomaterial and synthesis gas show high efficiency in converting CTP into high-value-added products.

© 2022 Society.This is an experimental study on the decolorization efficiency and the degradation of organic compounds from textile wastewater by the ozonation process in a batch system. The effects of different sample volumes of textile wastewater over time were investigated. The experiments were performed in a 1 L glass reactor with a magnetic stirrer and a bubble diffuser at the bottom to feed the ozone. The applied cumulative ozone dosage varied at 120 gO3 L−1, 60 gO3 L−1, and 30 gO3 L−1, and the total interaction time for each test was 1 h. To investigate the physicochemical properties of the textile wastewater (solid and liquid phases) before and after the treatment, multiple analytical characterization methods were used: Thermal Gravimetric Analysis, Scanning Electron Microscopy coupled with Energy-Dispersive X-ray Spectroscopy, X-ray diffraction, Fourier Transform Infrared spectroscopy, and Spectrophotometer. The most perceptive change was observed in the color of the liquid medium, which turned from black to transparent, and a visual color number indicator known as DurchsichtFarbZahl (DFZ) was used for the evaluation of this process. Absorbance values decreased about 3.5 times after 5 min of treatment with a 0.15 L sample volume, and these values differed for tests with larger sample volumes. FTIR spectroscopy demonstrated that the bands’ intensities associated with the C − H, C − N, and C − O decrease during treatment. On the other hand, it was possible to conclude that combining treatment methods to improve the degradation of persistent compounds after the ozonation process is necessary. Finally, the ozonation of the textile wastewater proved to be effective at removing color due to its high reaction capacity.

© 2021 Informa UK Limited, trading as Taylor & Francis Group.The processing of coal tar pitch (CTP) to produce clean fuel gas and carbon black (CB) is studied in a plasma reactor equipped with a direct-current plasma torch. The composition of the gas produced and energy costs were estimated theoretically for the CTP pyrolysis and gasification processes by two oxidants, namely oxygen and water vapor. We have found that the main gaseous compounds obtained in the pyrolysis and gasification processes are hydrogen (H2), carbon monoxide (CO), and very often carbon dioxide (CO2). For the pyrolysis case, the mean value of the synthesis gas concentration reaches a major value of 98 vol.% (H2–81 vol.%, CO–17. vol.%). However, only 23% of the initial CTP is transformed into gas phase at 1100 K and its content increases up to 37.4% at a temperature of 3000 K. For oxygen gasification, the syngas quantity is little less compared to the pyrolysis case and attains 96.6 vol.% (H2–26.5 vol.%, CO–70.1 vol.%) for T > 1100 K. An intermediate syngas content for the water steam gasification is 97.8 vol.% (with H2–55.8 vol.% and CO–42.0 vol.%). The CB produced was composed of well-defined spherical particles of 30-nm size. Furthermore, it is composed of carbon (98.2%), and followed by oxygen (1.8%) with a surface area of 97 m2 g−1. The thermal plasma system shows high efficiency in conversion of CTP into high-value-added products.

© 2022 Elsevier LtdThe corrosion behaviour of laser and plasma nitrided β-Ti12Mo6Zr2Fe biomaterial was evaluated. Polarisation curves and electrochemical impedance spectroscopy were performed in simulated body fluid (SBF) at 37 °C. Both treatments formed titanium-nitride at the alloy's surface, and significantly improved the corrosion performance of the alloy. At anodic potentials of the order of 1.0 V, the titanium-nitride layer seems to oxidise, independent of the nitriding process. Nanometric fissures formed on the plasma titanium-nitride layer seems to govern the impedance response at low frequencies, exposing the substrate to the electrolyte. Laser titanium-nitride layer is thicker and lead to a better corrosion performance.

© 2022 Elsevier B.V.Patients with skin diseases may have their quality of life affected. Many of them have chronic skin lesions or some form of complication during the healing process. Ozone therapy is a low-cost method with efficient results, including the easy application of ozonized oil to the skin. However, studies report divergent times for the ozonation process of vegetable oil. This work aims to characterize, using the Fourier transform infrared (FT-IR) spectroscopy technique, sunflower oil ozonized at different exposure times. Nine samples of oil were treated up to 90 min with ozone (maximum applied ozone dosage of 117.0 g L−1) and, together with the control sample, were analyzed by FT-IR and the spectra deconvoluted in relation to the main bands observed by the second derivative. Two spectral regions were investigated: 1800 – 800 cm−1 and 3050 – 2800 cm−1. The results indicated a statistically significant difference between the spectra, especially after 20 min of the ozonation process. A decrease in oil temperature was observed 30 min after the beginning of the ozonation process, with a decrease in the intensity of the –CH stretching band of the fragment –C[dbnd]C–H above 3000 cm−1, an increase of the intensity of the C–H stretching bands of the CH3 groups, decrease of intensity of the stretching bands of –C[dbnd]C– chemical bond, and constant intensity of the –C[dbnd]O stretching band.

© 2022 by the authors.The growing need for increasingly miniaturized devices has placed high importance and demands on nanofabrication technologies with high-quality, low temperatures, and low-cost techniques. In the past few years, the development and recent advances in atomic layer deposition (ALD) processes boosted interest in their use in advanced electronic and nano/microelectromechanical systems (NEMS/MEMS) device manufacturing. In this context, non-thermal plasma (NTP) technology has been highlighted because it allowed the ALD technique to expand its process window and the fabrication of several nanomaterials at reduced temperatures, allowing thermosensitive substrates to be covered with good formability and uniformity. In this review article, we comprehensively describe how the NTP changed the ALD universe and expanded it in device fabrication for different applications. We also present an overview of the efforts and developed strategies to gather the NTP and ALD technologies with the consecutive formation of plasma-assisted ALD (PA-ALD) technique, which has been successfully applied in nanofabrication and surface modification. The advantages and limitations currently faced by this technique are presented and discussed. We conclude this review by showing the atomic layer etching (ALE) technique, another development of NTP and ALD junction that has gained more and more attention by allowing significant advancements in plasma-assisted nanofabrication.

© 2022 by the authors.This work reports on the (zero-dimensional) global model study of argon plasma chemistry for a cylindrical thruster based on inductively coupled plasma (ICP) whose output has a system of two grids polarized with each other with direct current potential. The global model developed is based on particle and energy balance equations, where the latter considers both charged and neutral species. Thus, the model allows the determination of the neutral gas temperature. Finally, this study also investigated the role of excited species in plasma chemistry especially in the ions production and its implications for propulsion parameters, such as thrust. For this, the study was carried out in two different scenarios: (1) one taking into account the metastable species Arr and Arp (multi-step ionization), and (2) the other without these species (single-step ionization). Results indicates a distinct behavior of electron temperature with radiofrequency (RF) power for the investigated cases. On the other hand, the gas temperature is almost the same for investigated power range of up to 900 W. Concern propulsion analysis, a thrust of 40 mN at 450 W was verified for case (1), which represents a remarkable thrust value for electric thrusters.

© 2022 Elsevier LtdThe management of radioactive waste is a worldwide activity based on the guidelines of the International Atomic Energy Agency (IAEA), and all stages of management require scientifically proven methods for possible deployment. The management of radioactive waste is a huge challenge due to the high risk in the collection, gathering, transport, handling, and storage. In this study, a thermal plasma treatment process was evaluated for its efficiency to process solid radioactive waste. Experiments were carried out with the application of stable isotopes of Lead, Iodine, Cobalt, and Cesium. After the thermal plasma treatments, the slag and the residual gas were analyzed to verify the influence of process time and discharge power on the efficiency of the process. The treatment for 25 min and 10 kW was sufficient to reduce the mass by 50% of the slag. When the applied power was increased to 15 kW, an expressive reduction in the treatment time (10 min) was able to promote the same mass reduction. The results indicated that the treatment of radioactive waste by thermal plasma is a promising method to manage and reduce the mass and volume for the final disposal.

© 2023 Elsevier Inc. All rights reserved.Solar cells and photovoltaic devices are based overall on metal oxides and heterostructures. This is a technology in advance, with remarkable interest due to its low impact on the environment in comparison to the most used forms of energy conversion. Additionally, the oxides are most abundant, easy, and less expensive to obtain compared to other materials for such applications. Although the metal oxide–based photovoltaic devices show, usually, low conversion efficiency, some studies have shown capable of obtaining PCE higher than 10% or 20% using enhanced heterostructures. This chapter presented a review of the state of the art of metal oxide heterostructures applied mainly in photovoltaic devices and solar cells. A special focus is given to studies related to some of the most applied materials, such as ZnO, ZnO:Al, (AZO), and TiO2, and to heterostructures based on metallic oxides of copper, zinc, magnesium, vanadium, etc.

© 2022 The Author(s).Background. New surface treatments have been proposed to expand the clinical indications of zirconia prostheses. This study aimed to evaluate the effect of silica and fluorine nanofilms on zirconia ceramic on the resin cement bond strength. Methods. Zirconia blocks and discs underwent different surface treatments: untreated zirconia (CON), sandblasted, silica-coated alumina particles (30 µm) (SC), silica nanofilm (SN), and fluorine nanofilm (FN). Nanofilm deposition was performed through plasma enhanced chemical vapor deposition (PECVD). Zirconia surfaces were characterized on disks by morphology (atomic force microscopy, AFM), chemical analysis (x-ray photoelectron spectroscopy, XPS), and contact angle analysis. A silane coupling agent was applied on each treated surface, and a cylinder of resin cement was built up. Half of the specimens in each group were submitted to 6000 thermal cycles (TC). Bond strength was analyzed using the shear test, and the fractographic analysis was performed with stereomicroscopy and SEM/EDS. Statistical analysis was performed through one-way ANOVA and Tukey test in the non-aged and aged specimens. Results. Nanofilms modified the zirconia surface, which became more hydrophilic and chemically reactive. Chemical bonding between Si-O was found in SN, and FN promoted a fluorination process on the ceramic surface, converting zirconia into zirconium oxyfluoride. Specimens of the SN (TC) group failed on pre-testing. FN (TC) bond strength (3.8 MPa) was lower than SC (TC) and CON (TC) after shearing. Adhesive failure predominated in the experimental groups. Silica nanofilm failure occurred after aging. Conclusion. Silica and fluorine nanofilms deposited by PECVD did not promote effective bonding between zirconia and resin cement.

© 2022 Universidade Federal de Sao Carlos. All rights reserved.This work reports the properties of GaN films grown onto c-Si (100) at relatively low substrate temperature (400°C) by reactive magnetron sputtering. The study depicts the effect of working pressure and RF power on the GaN film structural, vibrational and optical properties characterized by X-ray diffraction, atomic force and scanning electron microscopies, Raman spectroscopy and spectroscopic ellipsometry. Unusual low pressure deposition condition (0.40 Pa) was achieved by using a separated argon inlet directed to the Ga target surface, resulting in improved crystalline quality of the films. In this condition, the preferential crystalline orientation, the surface morphology and the optical gap of the GaN films show a strong dependence on the RF power applied to the Ga target, where low RF power (30-60 W) was responsible for increasing the c-axis orientation and the optical gap, while higher RF power (75-90 W) decreased the overall crystal quality and increased the surface roughness.

© 2021 Wiley-VCH GmbHThis study applies a proof of concept for future applications in controlling the microbiota in tubes and tracheal appliances used in the respiratory tract. Therefore, the physical–chemical parameters of the plasma-activated and nebulized water (NPAW) are measured in a nebulizer tube with different lengths between 0.1 and 3.0 m. The pH values and oxidation–reduction potential (ORP) do not change during nebulization of PAW over a 1.0 m tube. However, for longer lengths, there is an increase in pH and a decrease in ORP. At 3.0 m, the pH increases approximately 16% compared with the 1.0 m position with a 20% decrease in the ORP values. Hydrogen peroxide (H2O2) measured quantitatively using test strips presents values between 0.5 and 2.0 mg/L for condensed NPAW in different tube lengths between 0.1 and 3.0 m, and maintains the approximate value of 2.0 mg/L in tubes up to 1.0 m, with a reduction proportional to the increase in the length of the tube. The antimicrobial efficacy of NPAW applied for 15 min shows the inactivation of Staphylococcus aureus and Escherichia coli but without significant inactivation of Candida albicans.

© 2021, Associação Brasileira de Engenharia Química.Mercury and its compounds are very dangerous to environmental and human health. Methods to contain and/or limit its emission through the filters, gas cleaning systems, and alternative processes for purification of industrial residues are necessary. This study focused on mercury removal from diatomite sorbent samples–used as a filter in chemical industries–using an oxygen low-pressure hollow cathode discharge (HCD). The effects of the exposure time and temperature were investigated. Thermal desorption (at 500 and 650 °C) and plasma oxidation were performed at low pressures (between 36 and 80 Pa). The results show a considerable acceleration of the diatomite decontamination to a temperature of 650 °C, bringing the concentration of mercury below 100 µg/kg after 10 min and 39 µg/kg after 110 min of HCD exposure time. A comparative analysis of the virgin diatomite characteristics used in the filter press and after treatment show the possibility of recycling this material. Additionally, the mercury extracted by condensation in the vacuum line (by using a dry ice trap) can be purified for reuse and returned to the industrial process.

© 2021 by the authors. Licensee MDPI, Basel, Switzerland.In this study, the potential antimicrobial activity of plasma-activated tap water (PAW) was evaluated against Staphylococcus aureus, Escherichia coli, and Candida albicans. For this, PAW was prepared in a gliding arc plasma system using two treatment conditions: stagnant water and water stirring by a magnetic stirrer, called moving water. Subsequently, their oxidation-reduction potential (ORP), pH, electrical conductivity (σ), and total dissolved solids (TDS) were monitored in different areas of the sample divided according to the depth of the beaker. It was observed that PAW obtained in dynamic conditions showed a more uniform acidity among the evaluated areas with pH 3.53 and ORP of 215 mV. Finally, standardized suspensions of Staphylococcus aureus (ATCC 6538), Escherichia coli (ATCC 10799), and Candida albicans (SC 5314) were treated with PAW, and the reduction of viable cells determined the antimicrobial effect. Our results indicate that the tap water, activated by plasma treatment using gliding arc, is an excellent inactivation agent in the case of Staphylococcus aureus and Escherichia coli. On the other hand, no significant antimicrobial activity was achieved for Candida albicans.

© 2020The increase in the biointegration speed of titanium alloys is an important factor in the recovery and quality of life after an implant. The coating of these materials with thin films using plasma technologies is a viable alternative that can change the surface properties without changing the bulk properties. In this work, Diamond-like Carbon films doped with silver nanoparticles were deposited on the surface of Ti6Al4V alloys using a conjugate reactor, which uses Plasma Enhanced Chemical Vapor Deposition technique associated with a silver hollow cathode. The flow of argon was varied (from 20 to 80 sccm) to evaluate its influence on surface roughness and biointegration. Secondary Ion Mass Spectrometry depth profile showed the effectiveness of the hollow cathode to form a silver concentration gradient from the substrate up to the film surface, which is desirable in biomedical applications. Atomic Force Microscopy detected that increasing argon flow from 20 to 80 sccm produced a more acicular relief and promoted an increase in sp3 hybridization, which characterizes films with better adhesion and mechanical resistance, as well as biomedical applications in which the material is subjected to load-bearing and wear. These results indicated the possibility of tuning the film roughness according to its biomedical application. The results of in vivo tests suggested that silver doping in Diamond-like Carbon films promoted faster biointegration than non-doped Diamond-like Carbon films and indicated the potential for their applicability in medical prosthetic materials.

© 2021 Universidade Federal de Sao Carlos. All rights reserved.Every year, billions of dollars are invested in research and development for space applications, including new systems, new technologies, and new materials. DLC (Diamond-Like Carbon) is a promising material for use in these applications, but its use faces a technological barrier, since it is severely etched by atomic oxygen and ozone. In this study, SiOx-DLC thin films were deposited as a top layer of diamond-like carbon (DLC) films on Ti-6Al-4V substrates to increase resistance against corrosion by atomic oxygen and ozone as well as meet the requirements for use in Low Earth Orbit (LEO) satellites. The corrosion resistance of the films was evaluated using oxygen plasma, and the tribological and mechanical properties were investigated. The SiOx-DLC top layer reduced the corrosion rate two orders of magnitude and increased the critical load from 16.2 ± 1.5 N to 18.4 ± 0.4 N.

© 2021 by the authors. Licensee MDPI, Basel, Switzerland.The chemical, structural, morphological, and optical properties of Al-doped TiO2 thin films, called TiO2/Al2O3 nanolaminates, grown by plasma-enhanced atomic layer deposition (PEALD) on p-type Si <100> and commercial SLG glass were discussed. High-quality PEALD TiO2/Al2O3 nanolam-inates were produced in the amorphous and crystalline phases. All crystalline nanolaminates have an overabundance of oxygen, while amorphous ones lack oxygen. The superabundance of oxygen on the crystalline film surface was illustrated by a schematic representation that described this phenomenon observed for PEALD TiO2/Al2O3 nanolaminates. The transition from crystalline to amorphous phase increased the surface hardness and the optical gap and decreased the refractive index. Therefore, the doping effect of TiO2 by the insertion of Al2O3 monolayers showed that it is possible to adjust different parameters of the thin-film material and to control, for example, the mobility of the hole-electron pair in the metal-insulator-devices semiconductors, corrosion protection, and optical properties, which are crucial for application in a wide range of technological areas, such as those used to manufacture fluorescence biosensors, photodetectors, and solar cells, among other devices.

© 2020 International Ozone Association.The purpose of the current study was to investigate the effect of ozone exposure on the process of water uptake and germination of lentil (Lens culinaris) seeds. For this, a commercial ozone generator that provides a concentration of 1 g/m3 generated from atmospheric air was used. In the experiments 10 lentil seeds were used per treatment carried out at different times of exposure to ozone: 2, 3, 5, 10 and 15 min. Imbibition curves were performed following the seed mass for 180 min. For germination tests, wet neutral pH germination paper was used where, every 24 h, the mass, root size and stem size of the plant were measured over 7 days. Furthermore, contact angle analysis and Fourier transform infrared spectroscopy (FT-IR) were performed on the seeds. The maximum water uptake in the seeds as a function of the imbibition time was optimum for the samples treated with 3 and 5 min. This fact was reflected in the growth rates of the stem, root and mass that were significantly higher than the control sample, after 7 days of germination. The FT-IR analysis indicated the formation of bands in 1345 cm−1 (NO3−) related to ethylene ozonolysis. Also, it was observed a reduction of the N-H band (amide II) at 1551–1550 cm−1 and increase of the C-H bond at 1543 cm−1, evidencing a possible action of ozone on lentil proteins. This fact is probably related to the enhancement of the seed germination process, allowing the germination rates to be 90% for samples treated with ozone for 3 and 10 min.

© 2020 The Author(s). published on behalf of Materials Research Society by Cambridge University Press.Austenitic stainless steel is used in several industrial branches due to its mechanical and thermal properties, and to its good corrosion resistance. With low cost and biocompatibility, it is used to manufacture prostheses and devices for bone fixation. However, direct contact with body fluids may cause corrosion. Thin films of FeAlCr intermetallic alloy can be used to increase service life of prostheses and avoid replacement surgeries. The aim of this work was to cover the austenitic stainless steel to study the effect of target-substrate distance on the film characteristics. Coatings were performed using the magnetron sputtering technique with the substrate positioned at different distances from the target. The influence on film thickness, morphology, roughness, and adhesion to the substrate was investigated. The thin films of FeAlCr (160 nm thick deposited at 100 mm far from the substrate) were formed by smaller particles (11.2 nm long), densely packed (551,000 particles/mm2), with flat and regular appearance, and greater adherence to the substrate.

© 2020 Universidade Federal de Sao Carlos. All rights reserved.This work reports how the solar conversion efficiency of dye-sensitized solar cells (DSSCs) depends on the crystalline structure of both the compact TiO2 blocking layer (BL) and homoepitaxially grown porous TiO2 mesoporous structure. The films were grown by simultaneous sputtering of titanium targets by DC magnetron and by high-power impulse magnetron systems (HiPIMS). The deposition conditions were managed to produce in situ dense BLs and porous TiO2 films. The only variable was the polarization of the BLs (0 to -200V). The polarization caused phase transformations from pure anatase phase through rutile-anatase mixed phases to rutile phase. The polarization results in decreasing intensity of the anatase (101) peak of the porous layers. The latter promptly decreased linearly the value of the short-current Isc and exponentially the open-circuit voltage Voc of the cells. Another inference is the surface energy of the BLs, which follows an exponential decay as a function of the film polarization. XPS study of the Ti 2p3/2 – Ti 2p1/2 doublet reveals an appearance of a shake-up satellite, whose area exponentially decreases as the polarization potential rises. This phenomenon is discussed and related with other physical aspects of the homo-epitaxially grown films with different texture. The anatase phase content and its purity predefined by the experimental conditions determine the quality of the DSSC, as well as other components such as the dye type, the electrolyte, and the electrode materials.

© 2020 by the authors.This work proposes the use of a dielectric barrier discharge (DBD) reactor operating at atmospheric pressure (AP) using air and sub-atmospheric pressure (SAP) using air or argon to treat polyamide 6.6 (PA6.6) fabrics. Here, plasma dosages corresponding to 37.5 kW·min·m-2 for AP and 7.5 kW·min·m-2 for SAP in air or argon were used. The hydrophilicity aging effect property of untreated and DBD-treated PA6.6 samples was evaluated from the apparent contact angle. The surface changes in physical microstructure were studied by field emission scanning electron microscopy (FE-SEM). To prove the changes in chemical functional groups in the fibers, Fourier transform infrared spectroscopy (FTIR) was used, and the change in surface bonds was evaluated by energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). In addition, the whiteness effect was investigated by the color spectrophotometry (Datacolor) technique. The results showed that the increase in surface roughness by the SAP DBD treatment contributed to a decrease in and maintenance of the hydrophilicity of PA6.6 fabrics for longer. The SAP DBD in air treatment promoted an enhancement of the aging effect with a low plasma dosage (5-fold reduction compared with AP DBD treatment). Finally, the SAP DBD treatment using argon functionalizes the fabric surface more efficiently than DBD treatments in air.

© 2020 by the authors. Licensee MDPI, Basel, Switzerland.Black TiO2 materials have been quite widely explored due to their large solar absorption and superior photocatalytic activity. In this paper, the blackening process of titanium dioxide (TiO2) thin film using the hollow cathode hydrogen plasma (HCHP) technique is reported. First, pristine anatase TiO2 films were grown by magnetron sputtering onto silicon and cover glass substrates and then annealed at 450◦C for 2 h. Then, the as-grown TiO2 films were treated with HCHP for 15 min. The physical, chemical and morphological properties of the films were analyzed by profilometry, X-ray diffraction (XRD), UV-Vis spectrophotometry, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) techniques. Electrical and photocatalytic measurements were performed by four-point probe and methylene blue UV degradation assays, respectively. The results showed that the black TiO2 film is highly absorbent in the UV-visible region, has low electrical resistance and greater surface area compared to the non-treated TiO2 film. These properties of black TiO2 film, as well as its performance as a photocatalytic agent, were investigated, indicating the superior quality of this material in thin film form and the promising potential of the HCHP treatment to produce hydrogenated TiO2 in short process time.

© 2020 Elsevier Ltd. All rights reserved.An experimental study on the degradation of organic compounds from radioactive oil sludge by the ozonation process is presented. The effects of different concentrations of ozone in the oil sludge degradation over time were investigated. The experiments were performed in a 0.125 L glass reactor with magnetic stirring and a diffuser plate at the bottom to feed the ozone. The ozone concentration varied from 13 to 53 mg L-1 and the total interaction time was 1 h. To investigate the physicochemical properties of the oil sludge (solid and liquid components) prior to and after the treatment, multiple analytical characterization methods were used: Thermal Gravimetric Analysis, X-ray diffraction, Scanning Electron Microscopy coupled with Energy-Dispersive X-ray Spectroscopy, Fourier Transform Infrared spectroscopy, Spectrophotometer, and Residual Gas Analyzer. The most perceptive change is in the color of the liquid medium turned from dark brown to light yellow, especially under ozone concentrations higher than 33 mg L-1. Absorbance values decreased about 3.5 times after 30 min of treatment with [O3] =53 mg L-1. FTIR spectroscopy showed that the bands associated with the CH3 and CeH in CH2 disappeared during treatment. On the other hand, a greater presence of C]C aromatics was observed. By residual gas analysis, various organic and inorganic gases were identified during the treatment, such as CH4, H2, CO2, and H2S. Finally, the ozonation of the oil sludge proved to be effective, due to its high reaction capacity.

� 2019, Associacao Brasileira de Divulgacao Cientifica. All rights reserved.Diamond-like carbon (DLC) film is a biocompatible hard coating material that can prevent the leaching of metal ions. This study evaluates the structural characteristics of DLC, with and without silver nanoparticles, deposited by plasma (PECVD) on titanium alloy (Ti-6Al-4V) and bone formation in contact with DLC films. Sixty Ti-6Al-4V samples were used divided in: Uncoated, coated with DLC and coated with DLC-Ag. After structural characterization, samples were fixed bilaterally at the rabbit's mandible. After 15 and 90 days, samples were characterized again and bone formation in the area was analyzed by histomorphometry. Statistical analysis was performed by two-way ANOVA. Both the DLC and DLC-Ag films were firmly adhered and showed a high electrical resistance without significant changes in the Raman spectrum after in vivo integration. After 15 days, there were immature bone trabeculae in the interface and partially covering the surface. After 90 days, mature bone filled the interface and coved the surface. There was no statistically significant difference among the three groups in both periods. In conclusion, osseointegration with DLC, DLC-Ag and uncoated Ti-6Al-4V is similar. However, DLC and DLC-Ag coverings have the advantage of electrical insulation and can presumably control bacterial activity and ion leaching.

© 2019 John Wiley & Sons Australia, Ltd.AIM: To analyze the effect of a silicon (Si)-based film deposited on yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) on the topography and bond strength of resin cement. METHODS: Specimens of zirconia were obtained and randomly divided into 4 groups, according to surface treatment: polished group (PG) zirconia; sandblasted group (SG) zirconia with aluminum oxide (100 µm); after polished, zirconia was coated with Si-based film group (SiFG); and after sandblasted, zirconia was coated with Si-based film group (SiFSG). The Si-based films were obtained through plasma-enhanced chemical vapor deposition. Surface roughness and contact angle analysis were performed. Resin cement cylinders were built up on the treated surface of blocks, after applying Monobond-S. The specimens were submitted to thermocycling aging and shear bond strength testing. The Kruskal-Wallis and Mann-Whitney U-tests were performed. RESULTS: There were significant differences between the surface treatments for each roughness parameter measured. Si-based film increased roughness and decreased the contact angle. Si-based film groups also demonstrated significantly lower bond strength values. CONCLUSION: Si-based film produced using plasma deposition provided lower bond strength to resin cement compared with conventional treatment; however, the film deposition reduced the contact angle and improved roughness, favorable properties in the long way to prepare an optimum material.

© 2019Increasingly more young patients have been submitted to reconstruction of the Temporomandibular Joint (TMJ), so, the prostheses must to present more functional longevity. Objective: To evaluate the effect of diamond-like carbon film (DLC)over titanium alloy (Ti6Al4V)and polyethylene (UHWPE)samples, their mechanical and chemical properties and cellular cytotoxicity. Methods: Titanium and UHWPE specimens, with 2.5 cm in diameter and 2 mm thickness were coated through plasma enhanced chemical vapor deposition (PECVD)with DLC or DLC doped with silver (DLC-Ag). Scanning electron microscopy (SEM)morphological analysis, Energy-dispersive spectroscopy (EDS)chemical analysis, scratching test, mechanical fatigue test, surface roughness analysis, and cellular cytotoxicity were performed. Data were statistically analyzed using one-way ANOVA (p < 0.05)or two-way ANOVA and multiple comparison Tukey test. Results: In the SEM analysis, morphological differences were observed on substrates after DLC deposition. The film chemically modified the substrate surfaces, according to the EDS analysis. The initial critical load failure occurred at 6.1 N for DLC and 9.7 N for the DLC-Ag film. The DLC film deposition over the polyethylene promoted a decrease in the polymer's damaged area after mechanical fatigue cycling. The cytotoxicity analysis demonstrated less biocompatibility in experimental groups, when compared to control, however, increased biocompatibility was observed, at 10 days, in all groups. Conclusion: The diamond-like carbon coating enhanced the chemical and mechanical properties from substrates, however modified biological interaction course of the titanium alloy (Ti6Al4V)and polyethylene (UHWPE)samples. Parameters for film deposition remain to be improved in order to obtain best biocompatibility.

© 2019 by the authors. The Ti-6Al-4V alloy is widely used in the manufacture of components that must have low density and high corrosion resistance and fatigue strength. The fatigue strength can be improved by surface modification. The aim of this study was to determine the influence of plasma nitriding on the fatigue behavior of a Ti-6Al-4V alloy with a lamellar microstructure (Widmanstätten type). Nitriding was executed at 720 °C for 4 h in an atmosphere with N 2 , Ar, and H 2 . Microstructure characterization of the samples was carried out by X-ray diffraction analysis, optical microscopy, and scanning electron microscopy. The average roughness of the specimens was determined, and fatigue tests were executed in a bending-rotating machine with reverse tension cycles (R = -1). X-ray diffraction analysis of the nitrided alloy revealed the following matrix phases: α,β, ε-Ti 2 N, and δ-TiN. A nitrogen diffusion layer was formed between the substrate and the titanium nitrides. Plasma nitriding resulted in an increase in low-cycle fatigue strength, whereas at high cycles of 200 MPa, both conditions exhibited similar behaviors. The fracture surface of the fatigue-tested specimens clearly revealed the lamellar microstructure. The fracture mechanism in the non-nitrided specimens appears to be due to cracking at the interface of the α and β phases of the lamellar microstructure.

© 2019 Trans Tech Publications Ltd, Switzerland.Ti alloys have been intensely used for human implants due to its excellent characteristics, like bio-inertness, low density, and corrosion resistance. However, some alloying elements were found to be toxic for the human body, which restricts the use of some alloys. Furthermore, there are two additional and essential aspects to be considered. The first relates to the young modulus that, despite being lower than other alloys commonly used for this purpose, it is still far over from the human bone modulus. Such high modulus can result in the stress shield phenomena and the consequent implant losing. The second aspect relates to the fact that bio-inertness does not guarantee a complete tissue integration to the implant and, consequently, the expected implant performance. In this context, new low modulus β-Ti alloys containing nontoxic elements have been developed in recent years, and several surface modification processes have been proposed to promote better implant/tissue integration. In the present work, the new β-type Ti-Mo-Zr-Fe alloy has been submitted to a plasma enhanced chemical vapor deposition (PECVD) process in order to form a superficial titanium nitride layer, aiming to produce a satisfactory substrate for the tissue cells growing. In a first step, microstructural characterization and corrosion performance of the modified alloy surface has been evaluated by Electrochemical Impedance Spectrometry and Potentiodynamic testing, and the results compared to the unmodified alloy. It was found that during the plasma nitriding process, that runs at 550oC for 1h, the metastable β microstructure is partially converted into α’ and possibly α” phases, which can impact the young modulus. The 500nm thick TiN layer formed over the alloy surface improved the corrosion behavior of the alloy. These results encourage the continuity of the research, with the future in vitro bio-activity testing of the nitrided surface.

© 2018 Elsevier B.V.Amorphous carbon thin films were grown by magnetron sputtering on crystalline Si and fluorine-doped tin oxide (FTO) substrates and annealed at 600 °C in vacuum. Subsequently, the films were subjected to SF6 plasma nanotexturing processes using different secondary gases such as H2, O2, and Ar. The samples were characterized by profilometry, atomic force microscopy, Raman spectroscopy, FTIR spectroscopy, and contact angle measurement. The samples have shown nanostructured surface patterns that strongly depended on the secondary plasma gas used (H2, O2, or Ar); the films subjected to the SF6 + Ar plasma nanotexturing presented the highest surface roughness. Investigation of the atomic structure indicated that the annealing process is responsible for a significant increase in sp2 hybridization of C. The contact angle measurement results have revealed the hydrophilic to hydrophobic transition owing to the annealing process. In contrast, super hydrophilic behavior was observed after the plasma nanotexturing processes. The increase in both the surface roughness and hydrophilicity of these nanotextured carbon thin films are highly desirable characteristics for their application as counter-electrodes in dye-sensitized solar cells and batteries.

© 2018, Springer-Verlag GmbH Germany, part of Springer Nature.The authors regret an error in the Experimental section of the published article:

© 2018 by the authors. Licensee MDPI, Basel, Switzerland.This work aimed to enhance the creep resistance of Ti-6Al-4V alloy treated by plasma nitriding. The nitriding was performed on specimens with a Widmanstätten microstructure for four hours at 690°C under a gas atmosphere containing Ar:N2:H2 (0.455:0.455:0.090). X-ray diffraction analysis showed that the ε-Ti2N and δ-TiN formed on the nitrided sample, in addition to the α-Ti and β-Ti matrix phases. The layer thickness of this sample was about 1 µm. Hot tensile tests were performed in the temperature range of 500 to 700°C on nitrided and non-nitrided samples, which indicated an increased strength of the nitrided samples. The same temperature range was used for the creep tests in a stress range of 125 to 319 MPa. The plasma-nitrided samples exhibited better creep resistance when compared to the untreated samples. This result was demonstrated by the decreased secondary creep rate and the increased final creep time. This improvement in the creep resistance appeared to be associated with the formation of the nitrided layer, which worked as a barrier to oxygen diffusion into the material and due to the formation of a surface residual compressive stress.

© 2017, Springer-Verlag GmbH Germany.Plasma-treated carbon thin films are investigated as counter electrodes for dye-sensitized solar cells. The films were grown onto fluorine-doped tin oxide (FTO) substrates by magnetron sputtering using pure graphite target and argon atmosphere and subsequently annealed at 600 °C for 30 min in vacuum. These films were then submitted to a plasma texturing process in a reactive ion etching reactor using three different gas combinations: sulfur hexafluoride/argon (SF6 + Ar), sulfur hexafluoride/hydrogen (SF6 + H2), and sulfur hexafluoride/oxygen (SF6 + O2). The morphology and structure of the obtained films were characterized by scanning electron microscopy and Raman spectroscopy. Cyclic voltammetry technique allowed accessing the improvements in their catalytic properties, while the photocurrent-voltage curves under simulated solar illumination AM 1.5G (100 mW/cm2) evaluated the performance of the respective assembled solar cells. The results show that photovoltaic performance is significantly affected by the different plasma texturing conditions used. The carbon counter electrode obtained after SF6 + O2 plasma texturing achieved the best power conversion efficiency of 2.23%, which is comparable to the 2.31% obtained using the commercial platinum counter electrode.

© 2017 IEEE.Zinc oxide thin films have high resistivity, plus thermal and chemical stability. Such properties make this material suitable for fabrication of piezo-electric sensors and surface acoustic wave devices that are used in Microelectromechanical systems (MEMS). The addition of metallic nanoparticles into the film matrix can reduce the value of resistivity, and, thus, qualify the material to be used in piezoresistive devices. In this work, a dc magnetron co-sputtering was used to grow Al doped ZnO (AZO) films with different applied voltages in the Al target, deposited on Si (100) p-type substrates with a layer of 1 micron of SiO2 by thermal oxidation. The microstructure and chemical composition of the films were characterized by X-ray diffraction and Rutterford-Backscattering techniques, respectively. The RBS results indicate the presence of aluminum, zinc, and oxygen in the films, which was confirmed by the XRD peaks of ZnO (002) at 2θ=34.4° Four probe technique confirmed a gradual reduction of resistivity up to 8.10-3 Ω.cm as the applied power on the Al-target increased.

© 2017, Springer Science+Business Media New York.Abstract: A promising strategy to reduce nosocomial infections related to prosthetic meshes is the prevention of microbial colonization. To this aim, prosthetic meshes coated with antimicrobial thin films are proposed. Commercial polypropylene meshes were coated with metal-containing diamond-like carbon (Me-DLC) thin films by the magnetron sputtering technique. Several dissimilar metals (silver, cobalt, indium, tungsten, tin, aluminum, chromium, zinc, manganese, tantalum, and titanium) were tested and compositional analyses of each Me-DLC were performed by Rutherford backscattering spectrometry. Antimicrobial activities of the films against five microbial species (Candida albicans, Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Enterococcus faecalis) were also investigated by a modified Kirby-Bauer test. Results showed that films containing silver and cobalt have inhibited the growth of all microbial species. Tungsten-DLC, tin-DLC, aluminum-DLC, zinc-DLC, manganese-DLC, and tantalum-DLC inhibited the growth of some strains, while chromium- and titanium-DLC weakly inhibited the growth of only one tested strain. In-DLC film showed no antimicrobial activity. The effects of tungsten-DLC and cobalt-DLC on Pseudomonas aeruginosa biofilm formation were also assessed. Tungsten-DLC was able to significantly reduce biofilm formation. Overall, the experimental results in the present study have shown new approaches to coating polymeric biomaterials aiming antimicrobial effect. Graphical Abstract: [InlineMediaObject not available: see fulltext.].

© 2016 Elsevier B.V.This paper presents a study about creep behavior of SiC thin films with Cr interlayer deposited by High Power Impulse Magnetron Sputtering (HiPIMS) on Ti-6Al-4V alloys with Widmanstätten microstructure. After SiC/Cr film depositions, a microstructural characterization was performed using Scratching Test, Scanning Electron Microscopy (SEM), Scanning and Transmission Electron Microscopy (STEM), and Energy Dispersive Spectroscopy (EDS) techniques. Scratching tests showed that the film was well adhered to the substrate, which proves that the Cr interlayer is closely related to the strength of adhesion between SiC film and the substrate. The SiC film surface morphology has columnar shape according to STEM images. Creep test results were compared with earlier Ti-6Al-4V Widmanstätten microstructure studies, and they showed an increased lifetime for the Ti-6Al-4V Widmanstätten microstructure with SiC/Cr film, which indicates a higher creep resistance than the specimen without the SiC/Cr film. The SiC/Cr film deposited by HiPIMS improved the creep behavior of the Ti-6Al-4V Widmanstätten microstructure.

© 2017 Elsevier B.V.The development of more efficient photoelectrochemical solar cells has been, over the years, the subject of many scientific researches. In this paper a methodology was established to carry out the sintering process of nanoporous TiO2 layer by using plasma, which was compared with sintered layers made by the conventional sintering process in a furnace. The TiO2 commercial paste was spread by doctor-blading technique and subjected to different sintering processes. Porous layer samples were subjected to structural and morphological analyses. Then photoelectrodes dye-loading was measured by optical spectrophotometry. The quality of the layers under plasma sintering process in terms of weight loss and removal of organic compounds was evaluated by thermogravimetric analysis, mass spectrometry and FT-IR. The results showed that the plasma sintering process favors the adsorption of dye on the layer surface due to the creation of active states caused by O2 reactive plasma. Furthermore the O2 plasma process provides enough energy for removing organic compounds arising from the TiO2 paste and for providing nanoparticle sintering. Solar cells assembled with the plasma-sintered layers had a power conversion efficiency 20.1% higher than the obtained in solar cells sintered in a conventional furnace, proving the efficiency of the plasma sintering process.

© 2016 American Chemical Society.In this study, the authors have presented a numeric model (NM) for application to naphthalene (C10H8) conversion via ionization reaction in a microwave air plasma torch. The NM has included a pressure-independent enhanced electron energy distribution function (EEDF) and cross-section calculation, enhanced by a new formula of phase shift determination. Based on the validated NM, electron density ne and O2+, O-, C10H8, N2, and O2 particles densities were calculated, as well as the conversion rate of C10H8 molecules was predicted. The predicted results showed that the ionization impact on C10H8 molecules conversion has not exceeded 0.81 × 10-10%. Based on the calculated collision cross-section of each species (O2, N2, and C10H8) of carrier gas, the authors suggested using cubic polynomial approximations of the cross-section curves with R-Square (COD) parameter R2 = 99%. MW power increasing in the range 1.75-20 kW has raised the electron density in the range (0.5-4.5) × 1012 m-3. The maximal effect of electron density decreasing with pressure increasing was simulated at values of MW power greater than 7.5 kW. Herewith, pressure increasing and MW power increasing have not had any significant effect on the average electron energy.

© 2016 Elsevier Ltd. All rights reserved.In the last few years, the concentrating solar power (CSP) systems have been studied and growing surprisingly in several countries. The science and technology involved to manufacture the special materials for these devices has been a determining factor for the system performance. Among these special materials, ceramic-metal composite (cermet) is an important class largely used as a main absorber in the selective surfaces of evacuated tube collectors. This work aims to manufacture Mo-AlNxOy thin films by magnetron sputtering technique. The parameter studied was the effect of annealing temperature (600C-1100 °C) on the optical properties and surface morphology of the films. The results showed that the annealing (800-1100 °C) increase the absorptance, produces an oxidation in the bulk of the films and a breakage in the AlN surface bonds, reducing the initial quantity of nitrogen. It is noteworthy that the annealing at 600 °C did not alter the optical and morphology properties of the films, suggesting that the films of Mo-AlNxOy produced can be applied in selective surfaces in the future.

© 2016 Elsevier B.V. All rights reserved.The limitations of stainless steel as prosthesis material should be overcome in order to better satisfy the required specifications in bone replacements. One strategy to improve the corrosion and wear resistance and diminish the ion release is the surface modification of the implants by protective coatings. In this work, thin films of FeAlCr alloy were grown on ASTM F138 stainless steel by using DC magnetron sputtering technique. The films were produced by varying the sputtering power (from 50 to 200 W) and the substrate temperature (room temperature, 150 °C and 300 °C). The films obtained in all processing conditions were crystalline and presented the same chemical composition of the target material. It was found that the deposition rate of the films and their adhesion to the substrate increased with both the sputtering power and the substrate temperature. The best result was obtained for depositions carried out at 100 W and substrate heated at 300 °C.

© 2016 Published by Elsevier Ltd.Two kinds of reactively sputtered titanium dioxide films with columnar and fine-grained structures were investigated as diffusion barriers, preventing the silicon diffusion. The only differences in the deposition conditions were the oxygen percentage concentration (OC) in the discharge, kept for 10% and 30% of the total working pressure. The resulting films were found to have different thicknesses being 800 and 240 nm for 10% and 30% OC, respectively. The films were studied by X-Ray diffraction spectrometry (XRD) and their composition by Rutherford Backscattering Spectrometry (RBS). In order to describe the diffusion processes, the two batches were annealed up to temperature of 800°C. The diffusivity from 300°to 800°C is D(m2/s)=2.43.10-18exp[-(15kJ/mol)/(RT)] and D(m2/s)=2.36.10-18exp[-(18.4kJ/mol)/(RT)] for (10% OC) and TiO2 (30% OC), respectively. The physical meaning of the derived diffusion parameters are discussed in view of the crystalline peculiarities of the obtained films. Arrhenius plots show clearly that higher activation energy is characteristics for films with better-packed crystallites. These results are compared with known diffusion barrier layer such as TiN.

© 2016 Elsevier B.V. All rights reserved.Since Grätzel and O'Regan started in 1991, dye-sensitized solar cells (DSSC) have been extensively studied around the world. In addition to increasing efficiency, their characteristics such as low cost materials and inexpensive manufacturing processes are attractive for organic solar cells. Several parts of DSSC devices are being researched such as semiconductor engineering, low cost counter electrodes, electrolytes, and dyes. In this work, platinum (Pt) thin films were deposited by sputtering technique to produce counter electrodes for DSSC. The films were characterized by profilometry, elipsometry, four-point probe sheet resistance, spectrophotometry, and electrochemical impedance spectroscopy. The electrode response was also compared to that built from a commercial platinum solution. The results allow us to determine the minimum Pt film thickness necessary to achieve a relevant reduction of the sheet resistance and charge transfer resistance, which preserve a significant electrode transparency. The 22 nm and 24.8 nm thick films combined low charge transfer resistance and good transparency. The 122 nm Pt film presented the lowest charge transfer resistance.

© 2016 American Chemical Society.In this paper, a naphthalene (C10H8) thermal cracking model is presented. The model is based on a simple model that takes into account the microwave (MW) plasma thermal influence on naphthalene cracking, accompanying its steam reforming reactions. The temperature level of 1573 K was established for complete C10H8 cracking at 1.75 kW plasma power. High conversion efficiency of C10H8 is achieved varying the air flow rate in the range of 0.6-1.2 m3/h. The model approximates the characteristics of the considered MW plasma to thermal plasma in local thermodynamic equilibrium (LTE). Experimental data have good agreement with calculated data at the cited region of the air flow rate and power. Conversion efficiency up to 99.36% was obtained.

Background: The influence of diamond-like carbon (DLC) films on bacterial leakage through the interface between abutments and dental implants of external hexagon (EH) and internal hexagon (IH) designs was evaluated. Methods: Film deposition was performed by plasmaenhanced chemical vapor deposition. Sets of implants and abutments (n = 30 per group, sets of 180 implants) were divided according to connection design and treatment of the abutment base: 1) no treatment (control); 2) DLC film deposition; and 3) Ag-DLC film deposition. Under sterile conditions, 1 mL Enterococcus faecalis was inoculated inside the implants, and abutments were tightened. The sets were tested for immediate external contamination, suspended in test tubes containing sterile culture broth, and followed for 5 days. Turbidity of the broth indicated bacterial leakage. At the end of the period, the abutments were removed and the internal content of the implants was collected with paper points and plated in Petri dishes. After 24-hour incubation, they were assessed for bacterial viability and colony-forming unit counting. Bacterial leakage was analyzed by X2and Fisher exact tests (a = 5%). Results: The percentage of bacterial leakage was 16.09% for EH implants and 80.71% for IH implants (P <0.0001). The bacterial load was higher inside IH implants (P = 0.000). The type of implant significantly influenced the results (P = 0.000), whereas the films did not (P = 0.487). Conclusion: IH implants show a higher frequency of bacterial leakage; and DLC and Ag-DLC films do not significantly reduce the frequency of bacterial leakage and bacteria load inside the implants.

© 2015 Elsevier B.V.This paper presents a study about deposition parameters with tribological and mechanical properties of a-SiC:H films deposited by PECVD on titanium alloy (Ti-6Al-4V). HMDSO and TMS were used as silicon, carbon, and hydrogen precursors. The deposition temperature and pressure ranged from 400 to 600. °C and from 0.5 to 3.0. Torr, respectively. The chemical composition and structural properties of the contained samples were analyzed by XRD, FT-IR, and Raman spectroscopy. The mechanical and tribological properties were evaluated by scratching, nanohardness, friction, and wear tests. The results showed that the films presented amorphous structures, and those obtained with 500. °C and 3.0. Torr presented high adhesion and tribological performance. The films grown by using only HMDSO as precursor at 500. °C showed the highest deposition rate, higher hardness, good adhesion, and less friction coefficient values.

© 2015 IEEE.There is a great interest in understanding the properties of sputtered DLC films in order to enable their wide application in electronic devices and sensors. In present study, metal-containing diamond-like carbon (Me-DLC) thin films were deposited on Si (100) substrates by DC magnetron co-sputtering using a carbon target under a fixed power (150 W) and a metal target (tin or tungsten) under varying power (10-30 W), while the other parameters were kept constant. The growth rate, chemical composition, structure and electrical resistivity of the Sn-DLC and W-DLC thin films were studied by mechanical profilometer, RBS, SEM, Raman spectroscopy and four points probe, respectively. The results showed that the growth rate of Sn-DLC thin film is higher than the W-DLC. Furthermore, the Sn incorporation in DLC films is higher than W-DLC for the same power applied to the metal target. Relationship between the electrical resistivity of both film types and the power applied was also observed.

© 2015.In this paper, chrome (Cr) thin films were deposited and used as interlayer between SiC films and Ti-6Al-4V substrates. Films and interlayers were obtained by using HiPIMS (High Power Impulse Magnetron Sputtering) technique. Interlayers were growth for 5, 30, and 60 minutes. The films were analyzed with respect to morphology, stoichiometry, thickness, roughness, and adhesion. The results showed that the HiPIMS technique was efficient to produce dense thin films and that the adhesion increased with Cr thickness.

© 2015 by Quintessence Publishing Co Inc.Purpose: To determine the effect of maintaining torque after mechanical cycling of abutment screws that are coated with diamondlike carbon and coated with diamondlike carbon doped with diamond nanoparticles, with external and internal hex connections. Materials and Methods: Sixty implants were divided into six groups according to the type of connection (external or internal hex) and the type of abutment screw (uncoated, coated with diamondlike carbon, and coated with diamondlike carbon doped with diamond nanoparticles). The implants were inserted into polyurethane resin and crowns of nickel chrome were cemented on the implants. The crowns had a hole for access to the screw. The initial torque and the torque after mechanical cycling were measured. The torque values maintained (in percentages) were evaluated. Statistical analysis was performed using one-way analysis of variance and the Tukey test, with a significance level of 5%. Results: The largest torque value was maintained in uncoated screws with external hex connections, a finding that was statistically significant (P = .0001). No statistically significant differences were seen between the groups with and without coating in maintaining torque for screws with internal hex connections (P = .5476). Conclusion: After mechanical cycling, the diamondlike carbon with and without diamond doping on the abutment screws showed no improvement in maintaining torque in external and internal hex connections.

© 2014, The Minerals, Metals & Materials Society.In this work, the current–voltage characteristics of titanium oxynitride thin films were measured and the charge carrier transport mechanisms established as a function of film composition. The films were deposited by magnetron sputtering, where the oxygen/nitrogen ratio was varied via a pulsing technique to enable the achievement of desired concentrations. Thus, the obtained films showed metallic titanium nitrate (TiN) or semiconductor titanium dioxide (TiO2) character and were used to fabricate metal–insulator–metal structures. An ohmic conduction mechanism was identified in the films with higher nitrogen incorporation or presenting TiN-rich phase. Decrease in the nitrogen content resulted in films with TiO2-rich phase. In this case, Poole–Frenkel and space-charge-limited current conduction mechanisms were observed. The dielectric constants were calculated from the high-frequency capacitance–voltage dependences, with a reduction from 10 to 3 being observed due to the stoichiometric changes and probable incorporation of defects into the film structure. Finally, the film composition and structural characteristics of the films were revealed by Rutherford backscattering and x-ray diffraction techniques, respectively.

© 2014 Published by Elsevier Ltd.Sn-DLC thin films were deposited by a dual magnetron sputtering system using a fixed DC power applied to a C target and a variable DC or HiPIMS power supply applied to a Sn target. Scanning electron microscopy (SEM) images showed the presence of larger Sn clusters on films deposited using HiPIMS compared with those deposited using DC power supply. The small resistivity of HiPIMS films can be related with the large Sn cluster and the elevated number of sp2 type bonding.

Zinc oxide (ZnO) thin films were deposited by RF reactive magnetron sputtering on silicon (100) substrates under different experimental conditions. ZnO films were studied before and after annealing treatment at 600 °C. The crystallinity, electrical resistivity, stoichiometry, thickness, and elastic modulus of the films were investigated. ZnO piezoresistors were produced using microelectronics processes, such as photolithography, lift-off, and reactive ion etching (RIE). Cantilever method was used to determine the gauge factor, and measurements of Temperature Coefficient of Resistance (TCR) were performed on a hotplate. The optimization of the deposition conditions produced ZnO thin films with controlled stoichiometry (ZnO), crystalline microstructure (phase wurzite, 002), high elastic modulus (156 GPa), and low electrical resistivity (0.072 ohm.cm), which are good properties for application as piezoresistive pressure microsensor. In addition, the ZnO piezoresistors had a GF of 2.6 on the deformation in the plane (100) and TCR of -1610 ppm/K up to 250 °C.

In this work, the effect of microwave power and gas flow on formation of atomic oxygen (O) was investigated by actinometry method in the two different regions of Ar/O2 microwave plasma: the glow and afterglow regions. The experiments were performed keeping constant the Ar/O2 gas flow ratio at proportion of 3/2 and varying the microwave power from 200 to 1100 W and the total gas flow from 50 to 300 sccm. The results showed that the production of O depends on both discharge parameters investigated and that the microwave power has the greater influence in the production of O. At afterglow region the production of O tends to be uniform and not dependent on the gas flow and microwave power. This may be due to homogenization of the processes of recombination and loss in the gas phase and to the walls along the afterglow region.

In this work thin films of silicon carbide (SiC) were deposited on silicon wafers by High Power Impulse Magnetron Sputtering (HiPIMS) technique varying the average power of the discharge on a stoichiometric SiC target. X-ray diffraction, Raman spectroscopy, scanning electron microscopy and profilometry were used to analyze the films. It was observed that high values of the average electric power favors the formation of C-C bonds, while low values of the power promote the formation of Si-C bonds. At high power, we have also observed higher deposition rates, but the samples present surface imperfections, causing increase in the roughness and decrease in the film uniformity.

In this paper, nitrogen-doped TiO2 thin films were deposited by DC reactive sputtering at different doping levels for the development of dye-sensitized solar cells. The mechanism of film growth during the sputtering process and the effect of the nitrogen doping on the structural, optical, morphological, chemical, and electronic properties of the TiO2 were investigated by numerical modeling and experimental methods. The influence of the nitrogen doping on the working principle of the prototypes was investigated by current-voltage relations measured under illuminated and dark conditions. The results indicate that, during the film deposition, the control of the oxidation processes of the nitride layers plays a fundamental role for an effective incorporation of substitutional nitrogen in the film structure and cells built with nitrogen-doped TiO2 have higher short-circuit photocurrent in relation to that obtained with conventional DSSCs. On the other hand, DSSCs built with nondoped TiO2 have higher open-circuit voltage. These experimental observations indicate that the incorporation of nitrogen in the TiO2 lattice increases simultaneously the processes of generation and destruction of electric current. © 2014 D. A. Duarte et al.

This paper investigates the effect of the reactive gas mixture (N 2 + O2 + Ar) and oxidation of the nitride layers on the system stability during the reactive sputter deposition of TiOxN y thin films. The present research is an extension of previous investigations conducted by Severin et al. (Appl. Phys. Lett., 88 (2006) 161504) and Duarte et al. (Appl. Surf. Sci., 269 (2013) 55-59) in which the Berg's model was used to study reactive deposition of oxynitrides. The results show that the addition of N2 to the process avoids the formation of a hysteresis loop and facilitates the deposition of films with fractions of TiO2 at any value. These achievements are not possible without this procedure. In contrast, despite eliminating plasma instabilities, the addition of N2 decreases the mass deposition rate due to the modifications in the sputtering yield. Other results show that the oxidation of TiN also plays a key role in the mass deposition rate and in the hysteresis loop. © 2013 Elsevier Ltd. All rights reserved.

The ethylene propylene diene monomer (EPDM) rubber possesses excellent physical/chemical bulk properties, is cost-effective, and has been used in the mechanical and aerospace industry. However, it has an inert surface and needs a surface treatment in order to improve its adhesion properties. Plasma modification is the most accepted technique for surface modification of polymers without affecting the properties of the bulk. In this study, an afterglow microwave plasma reactor was used to generate the plasma species responsible for the EPDM surface modification. The plasma modified surfaces were analyzed by means of contact angle measurement, adhesion tests, attenuated total reflection-infrared spectroscopy, X-ray photoelectron spectroscopy and scanning electron microscopy. Two experimental variables were analyzed: type of the plasma gases and exposure time were considered. The predominant failure mode was adhesive, for long treatment times a mixture of adhesive and cohesive failure can be observed and the best conditions tested there was an increase of the rupture strength of about 27%, that can be associated mainly with the creation of oxygen containing functional groups on the rubber surface (CO, COC and CO) identified by spectroscopic methods. The predominant failure mode was adhesive, for long treatment times a mixture of adhesive and cohesive failure can be observed. In various conditions tested the contact angles easily decreased more than 500%. What can be concluded that high wettability is a necessary condition to obtain good adhesion, but this is not a sufficient condition. © 2013 Elsevier B.V. All rights reserved.

This study evaluated the influence of deposition parameters for Si-based thin films using magnetron sputtering for coating zirconia and subsequent adhesion of resin cement. Zirconia ceramic blocks were randomly divided into 8 groups and specimens were either ground finished and polished or conditioned using air-abrasion with alumina particles coated with silica. In the remaining groups, the polished specimens were coated with Si-based film coating with argon/oxygen magnetron discharge at 8:1 or 20:1 flux. In one group, Si-based film coating was performed on air-abraded surfaces. After application of bonding agent, resin cement was bonded. Profilometry, goniometry, Energy Dispersive X-ray Spectroscopy and Rutherford Backscattering Spectroscopy analysis were performed on the conditioned zirconia surfaces. Adhesion of resin cement to zirconia was tested using shear bond test and debonded surfaces were examined using Scanning Electron Microscopy. Si-based film coating applied on air-abraded rough zirconia surfaces increased the adhesion of the resin cement (22.78 ± 5.2 MPa) compared to those of other methods (0-14.62 MPa) (p = 0.05). Mixed type of failures were more frequent in Si film coated groups on either polished or air-abraded groups. Si-based thin films increased wettability compared to the control group but did not change the roughness, considering the parameters evaluated. Deposition parameters of Si-based thin film and after application of air-abrasion influenced the initial adhesion of resin cement to zirconia. © 2013 Elsevier B.V. All rights reserved.

Purpose: The purpose of this study was to evaluate the effect of diamond-like carbon thin films doped and undoped with silver nanoparticles coating poly(methyl methacrylate) (PMMA) on Candida albicans biofilm formation. The control of biofilm formation is important to prevent oral diseases in denture users. Materials and Methods: Forty-five PMMA disks were obtained, finished, cleaned in an ultrasonic bath, and divided into three groups: Gc, no surface coating (control group); Gdlc, coated with diamond-like carbon film; and Gag, coated with diamond-like carbon film doped with silver nanoparticles. The films were deposited using a reactive magnetron sputtering system (physical vapor deposition process). The specimens were characterized by optical profilometry, atomic force microscopy, and Rutherford backscattering spectroscopy analyses that determined differences in chemical composition and morphological structure. Following sterilization of the specimens by γ-ray irradiation, C. albicans (ATCC 18804) biofilms were formed by immersion in 2 ml of Sabouraud dextrose broth inoculated with a standardized fungal suspension. After 24 hours, the number of colony forming units (cfu) per specimen was counted. Data concerning biofilm formation were analyzed using ANOVA and the Tukey test (p < 0.05). Results: C. albicans biofilm formation was significantly influenced by the films (p < 0.00001), reducing the number of cfu, while not affecting the roughness parameters (p > 0.05). The Tukey test showed no significant difference between Gdlc and Gag. Films deposited were extremely thin (∼50 nm). The silver particles presented a diameter between 60 and 120 nm and regular distribution throughout the film surface (to Gag). Conclusion: Diamond-like carbon films, doped or undoped with silver nanoparticles, coating the base of PMMA-based dentures could be an alternative procedure for preventing candidosis in denture users. © 2013 by the American College of Prosthodontists.

Because of the scarcity of nonrenewable natural resources, such as petroleum and natural gas, the use of biofuel is needed. Gasification is a major process used to obtain renewable fuels from biomass; however, the gas cleaning system is a constraint for its broad utilization. During the pyrolysis process, a mixture of organic compounds in the gas phase is produced and must be removed from the gases before it is used in the most practical applications. In order to remove such organic compounds, which are known as tar, large, sophisticated, problematic, and expensive gas cleaning systems are added to the gasifier gas exit. Previous papers have shown that the plasma torch has the potential to destroy produced tar, being a simpler and less-expensive system than traditional gas cleaners. This work presents a qualitative and quantitative evaluation of a microwave plasma system running on tar destruction and its reforming. In order to evaluate a 1 kW microwave plasma system performance, an apparatus was developed and installed at ITA Laboratory of Plasmas and Processes (LPP-ITA). The system runs at atmospheric pressure with nitrogen and argon as carrier gas under a large range of flow rates. Experiments were performed using a gas mixture of N2, H2O, ethanol, and tar at controlled concentration in order to simulate the gases produced by a gasifier. The injected tar was obtained from pine pyrolysis and characterized for energy purposes. In order to reduce tar viscosity, it was diluted in commercial ethanol (92.5% ethanol and 7.5% water) and its concentration varied from 0.8 g tar/Nmgas3 to 4.2 gtar/Nm gas3. Species formed in the microwave plasma torch were identified using an optical spectrometer. The reactor exit gases had their composition evaluated on tar content as well as for noncondensable gases. As a result, this paper shows that no tar content was detected at the reactor outlet, indicating that all supplied tar was destroyed in the plasma reactor. The main detected products were CO and solid carbon (C(s)). Furthermore, neither NO nor CO2 were detected, and an indication of H2 formation was obtained. This paper concludes that the microwave plasma system is capable of destroying and reforming tar efficiently and produces mainly H 2, CO, O2, and C(s) as byproducts. © 2012 American Chemical Society.

Nowadays much efforts have been done with the aim to increase the global efficiency of the dye-sensitized solar cells so that the doping of the TiO 2 structure have been suggested as one of the most interesting solutions. In this paper the effect of the nitrogen incorporation in the TiO2 structure and studies about the effect of the doped films on the general properties of the solar cells are conducted. © 2013 IEEE.

Titanium dioxide (TiO2) thin films were deposited on silicon p type (100) substrates by reactive magnetron sputtering technique at different oxygen partial pressures. The film structure was studied by X-Ray Diffraction (XRD), while the film composition was examined by Rutherford Backscattering Spectroscopy (RBS). Finally, Metal-Oxide Semiconductor (MOS) capacitors were manufactured and some important physical constants were analyzed as function of the oxygen content in the films. It was found that the films deposited at lower oxygen partial pressure exhibited better crystalline structure and higher dielectric constant. © 2013 IEEE.

Purpose: To compare the effect of silica (Si)-based nano-coating deposited by reactive magnetron sputtering (RMP) with that of conventional surface conditioning using metal/zirconia primer alone or after air-particle abrasion on the adhesion of resin cements to zirconia ceramic. Materials and Methods: Two hundred forty zirconia ceramic blocks (Cercon) were sintered, finished with 1200-grit SiC paper under water cooling, and cleaned ultrasonically in distilled water for 10 min. The blocks (4.5 mm x 3.5 mm x 4.5 mm) were randomly divided into 24 groups (n = 10) according to 3 testing parameters: a) resin cements (Multilink, Panavia F, RelyX U100), b) surface conditioning (no conditioning as control group; Metal/Zirconia Primer; air abrasion + Metal/Zirconia Primer; Si-based nanofilm + Monobond s); c) aging (no aging vs thermo cycling at 5°C to 55°C, 6000 cycles). The nanofilm was deposited by direct current using argon/oxygen plasma (8: 1 in flux) on the zirconia surface. Resin cements were bonded to zirconia surfaces using polyethylene molds. The shear bond strength (SBS) test was performed using a universal testing machine (1 mm/min), and after debonding, the substrate and adherent surfaces were analyzed using optical and scanning electron microscopes to categorize the failure types. The data were statistically evaluated using 3-way ANOVA and Tukey’s test (5%). Results: Resin cement type (p < 0.05), surface conditioning method (p < 0.05), and aging condition (p < 0.05) had a significant effect on the bond strength results. Interactions were also significant (p < 0.05). In the nonaged condition, while control groups presented the lowest results with all cements (0 to 5.2 MPa), the airabraded group in combination with RelyX U100 resulted in the highest SBS (21.8 ± 6.7 MPa). After aging, the SBS results decreased in the air-abraded groups for all cements (4.54 to 9.44 MPa) and showed no statistical significance compared to the Si-based nanocoated groups (4.24 to 6.44 MPa). After air-abrasion and primer application, only Panavia F and RelyX U100 cements showed exclusively mixed failures, but after nanofilm coating and silanization, all cements showed exclusively mixed failures with and without aging. Conclusion: Chemical adhesion of the resin cements tested to zirconia was similar after silica-based nanofilm deposition and air abrasion followed by primer application. © 2013 by Quintessence Publishing Co Inc.

In this paper an original numerical model, based on the standard Berg model, was used to simulate the growth mechanism of N-doped TiO 2 deposited at different O 2 concentrations in the reactive gas mixture. For evaluation of the numerical model, films were deposited in the same conditions as those used in the numerical approach. Films were analyzed by profilometry, optical spectrophotometry, Rutherford back-scattering spectroscopy (RBS) and X-ray photoelectron spectroscopy (XPS). Results show that oxidation of TiN plays a fundamental role for incorporation of substitutional N in the TiO 2 lattice and the overall structure of the films, as well as, the chemical composition obtained from numerical model is in agreement to experimental data. © 2012 Elsevier B.V.

The influence of negative substrate bias on the chemical, electrical and mechanical properties of silicon carbide (SiC) thin films deposited onto (100) silicon substrate by dc magnetron cosputtering without external substrate heating is reported. These studies were performed by using the following techniques: Rutherford backscattering spectroscopy (RBS), profilometry, Raman spectroscopy, four-point probe method and nanoindentation. The results indicate that there is a good correlation between the substrate bias voltage and the argon incorporation into SiC film, namely, the SiC films deposited under substrate bias of -200 V and -300 V have higher argon content and higher elastic modulus and hardness than those deposited at 0 V. An opposite behavior was found for electrical resistivity: the SiC deposited at -300 V has resistivity of 0.45 Ω.cm whereas the deposited at 0 V has 7.0 Ω.cm. © 2012 Materials Research Society.

In this work, the effect of deposition pressure and total power applied to Si and C targets on the a-SiC film characteristics was investigated by profilometry, X-ray diffraction (XRD), Raman spectroscopy, and Rutherford-Backscattering Spectrometry (RBS). Profilometry results indicate an increase in the film thickness by increasing both the deposition pressure and total power. Both Crich and Si-rich a-SiC films were grown only by varying the deposition pressure or total power. Raman spectra suggest that the films contain amorphous phases because a-SiC clusters together with a-Si and a-C clusters were observed. The XRD analysis confirmed the amorphous structure of these films. © The Electrochemical Society.

In this work is proposed the automation of a gas injection (mass flow) system in order to generate timemultiplex SF6/CH4 radiofrequency plasma applied for silicon (Si) etching process. The control of the gas injection system is important in order to better control the process anisotropy, i.e., the high-aspect-ratio of mask pattern transfer to substrate surface. In other words, this control allows the attainment of deep Si etching process. Here, the automation of the gas injection system was realized through the interface between a computer and a data acquisition board. The automation software developed allows controlling the gas flow rate switching it on and off during whole process through the use of a square waveform routine, intermittent flow, beyond the conventional condition of a fixed value for gas flow rate, continuous flow. In order to investigate the time-multiplex SF6/CH4 plasma etching of Si, the residual gas analysis was performed. The investigations were made keeping the following process parameters: flow of SF6: 10 sccm, flow of CH4: 6 sccm, 100 W rf power, wave period: 20 sec. It were monitored the partial pressure of SF+ 5 (parent neutral specie: SF6), CH+4 (CH4) and SiF+ 3 (SiF4) species as a function of time for different gas flow switching and duty cycle. The results showed that with the generation of plasma occurs a drastic change in behavior of partial pressures of SF+ 5 and CH+4 species. Moreover, it is evidenced that the interactions between the SF6 and CH4 fragments promotes a high production rate of HF molecule and consequently a decrease of atomic fluorine, mainly when plasma is on. Finally, the behavior of partial pressure of SiF+ 3 specie for alternatively intermittent SF6 and CH4 flow operation shows us that both the etching processes and the deposition of a polymer passivation layer are occurring alternatively, a desirable feature for multi-step etching process. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A DC dual magnetron sputtering system with graphite (C) and silicon (Si) targets was used to grow stoichiometric and non-stoichiometric silicon carbide (SixCy) thin films at low temperature. Two independently DC power sources were used to enable the total discharge power be shared, under certain proportions, between the Si and C magnetron cathodes. The motivation was to control the sputtering rate of each target so as to vary the stoichiometric ratio x/y of the deposited films. The species content, thickness and chemical bonds of as-deposited SixCy films were studied by Rutherford backscattering spectroscopy (RBS), profilometry analysis and Fourier transform infrared absorption (FTIR), respectively. Overall, the present work reveals a new reliable plasma sputtering technique for low temperature growth of amorphous SixCy thin films with the capability of tuning the degree of formation of a-SiC, a-Si and a-C bonds in the film bulk. © (2012) Trans Tech Publications.

Amorphous silicon oxycarbonitride (SiCxNyOz) films have been deposited on Si substrates by low temperature reactive magnetron co-sputtering of silicon and graphite targets in mixed Ar/N2 atmosphere. Our studies are focused on the influence of nitrogen incorporation on deposition rate, film composition, film structure, chemical bonds, and electrical resistivity of SiCxNyOz films investigated by profilometry, Rutherford Backscattering Spectrometry (RBS), X-ray diffraction (XRD), Raman spectroscopy, X-ray Photoelectron Spectroscopy (XPS), and four-point probe method. RBS results show that all samples contain significant amounts of oxygen (up to 16at.%) which led to the formation of SiCxNyOz. Further, XPS results show that most of this oxygen is located in the film surface. With the addition of N2 gas in the plasma, the carbon, and nitrogen contents in the films increase. The increased carbon content is due to the contribution of chemically driven sputtering of the graphite target and the reduction of the sputtering rate of the silicon target owing to poisoning by nitrogen. Raman spectra suggest that the films contain amorphous phases and that the a-C clusters suffer a graphitization with increased N2 gas flow rate. The XRD analysis confirmed the amorphous structure of these films. According to the XPS analysis, the increase in nitrogen content leads to an increase in SiN and CN bonds, decreasing the SiC, SiSi, and CC bonds. Finally, the films electrical resistivity depends mainly on the nitrogen content, which makes it possible to obtain semiconductor or insulator SiCxNyOz films only by adjusting the N2 concentration in the gas phase during the deposition process. © 2011 Elsevier B.V.

This paper reports the deposition of titanium dioxide thin films on p-type Si(100) substrates using two techniques called conventional magnetron sputtering (CMS) and hollow cathode magnetron sputtering (HCMS). The influence of the plasma parameters on the film characteristics (topography, morphology and crystallinity) was investigated. Films were deposited at different oxygen concentrations (in the Ar + O2 gas mixture) and axial distances for fixed values of working pressure (5.0 mTorr) and DC power (55 W). They were analyzed by profilometry, AFM and XRD. The gas discharge was diagnosed by single Langmuir probe and OES. Under experimental conditions used in this work, results show that HCMS favors the growing of rutile phase due to the increase of the energy on the film surface caused by the hollow cathode effect. On the other hand, films deposited by CMS present preferentially anatase phase due to the low energy transferred to the growing film. Further studies regarding the influence of plasma properties on the films formation were done in order to understand the plasma-surface correlation. © EDP Sciences, 2011.

The bombardment of ions and electrons at the substrate has been studied by varying the magnetic field distribution and the grid-target distance in a triode magnetron sputtering system. The substrate temperature was correlated with the substrate current density and with the type of species bombarding the substrate. The results indicate a possibility to modify and control the bombardment at the substrate surface from predominantly electronic to predominantly ionic, which increases the substrate temperature from 383 K to 473 K, respectively. © 2010 EDP Sciences.

In the present work, a microwave excited plasma (2·45 GHz, 1 kW) was used to modify the surface characteristics of the ethylene propylene diene monomer rubber. The samples were treated with a mixture of nitrogen, hydrogen and argon plasmas. The operating gas pressure was in the 0·2-1 Torr range, the gas flowrate between 5 and 100 sccm and the treatment time varied from 10 to 600 s. The influence of the plasma treatment on the superficial characteristics of the samples was analysed by contact angle measurements and atomic force microscopy. The results show that the plasma treatment can promote an important decrease in the contact angle from 101° for untreated sample to 34° for samples treated in a mixture of H2/N2/Ar for 2 min, which corresponds an increase on the rubber surface adhesion work from 59 to 133 mJ m-2. © 2010 Institute of Materials, Minerals and Mining.

This work reports the influence of the nitrogen concentration (in the gas discharge) on the hydrophilicity properties of N-TiO2 min films, deposited at low temperature using DC magnetron sputtering on p-Si [100] substrates at different nitrogen flow rates for a fixed electrical power and working pressure. The photoinduced hydrophilicity effect was evaluated by the surface wettability measured through the contact angle between de-ionized water drop and the film surface. Results show that the photoinduced hydrophilicity effect occurs preferentially in min films with surfaces more irregular and predominantly anatase [101] crystalline orientation. Moreover, further observed phenomena were analyzed, investigated and discussed. © The Electrochemical Society.

Cylindrical hollow cathode magnetron sputtering (HCMS) system was used to deposit crystalline titanium dioxide thin films on p-Si (100) substrates. For a fixed pressure of 0.6 Pa total gas flow rate of 20 sccm and power of 55 W, the influence of the oxygen percentage in the Ar+O2 gas mixture on the structural and surface properties of the films was studied by profilometry, XRD and AFM. The substrates were placed inside the hollow cathode at different positions along its symmetrical axis. Numerical simulations of cathode ion collection probability (CICP) were done in order to compare calculated data with the deposition process characteristics. The results indicate that the deposition rate and the surface roughness gradually decrease with the distance from the bottom of the cathode, due to the decrease of the CICP. The increase of the oxygen percentage in the gas discharge influences directly the deposition rate and decrease the surface roughness. The XRD analyses show that all the films are crystalline with predominant anatase (101) and rutile (110) orientations. © 2009 EDP Sciences.

The aim of this work is to study the influence of electronegative gas (oxygen at different percentages) on the electrical characteristics of two configurations of magnetron sputtering systems, namely Hollow Cathode Magnetron Sputtering (HCMS) and Conventional Magnetron Sputtering (CMS). A comparison of the plasma impedances and magnetron efficiency of these two systems was carried out through the measurements of current-voltage (IxV) characteristics of the discharges operating at the same pressure and different oxygen percentage in O2/Ar mixtures. The results showed distinct behavior of IxV characteristics of the sputtering systems, indicating that, in general, HCMS presents better electrical performance than CMS system, i.e., the former has lower plasma impedance and higher magnetron efficiency. For both cases the magnetron efficiency is improved as the percentage of oxygen in the gas discharge is increased. HCMS shows to be a very interesting technique to be used as deposition system in micro and nanoelectronic processes. © The Electrochemical Society.

This paper describes the effect of the SF 6 gas residence time on the morphology of silicon (1 0 0) samples etched in a reactive ion etching system. Profilometry and atomic force microscopy techniques were used to characterize the etching process focusing attention on the evolution of the surface morphology. Under the condition of variable pressure and gas flow rate, the decrease of the residence time leads to an increase of the silicon etch rate concomitantly with an increase of the surface roughness. Contrary fact is observed when the gas flow is fixed and the pressure is varied. Here, the increasing of residence time leads to a constant increase of silicon etch rate with small variations in final surface roughness. To better understanding this resident time effect, mass spectrometry analyses were realized during the discharge for both gas flow conditions. © 2008 Elsevier B.V. All rights reserved.

Interactions between a late Ar-O 2 post-discharge and the hexatriacontane (HTC), a long-chain alkane, are shown to depend on the thermal flux released by surface reactions that makes the temperatures of the sample and the gas phase drift in an uncontrolled manner as a function of time. Since the transformations of the hexatriacontane depend on these temperatures, the initial value of the temperature and that of the oxygen concentration are key parameters that control the whole transformation process. A thorough description of the different steps of the transformation undergone by the hexatriacontane is given, explaining the origins of the limitation of the material etching. Pulsing the plasma shows that optimizing the etching process requires to work at low temperature, a too strong heating of the sample leading to functionalization and reticulation that limit the etching of the HTC. © 2008 Springer Science+Business Media, LLC.

Characterization of the interaction between an argon-oxygen post-discharge and hexatriacontane (C36H74) is carried out. Optical emission spectroscopy using the atmospheric band O2 (b 1σg+, v=0 → X3σ g-, v'=0) at 760 nm gives simultaneously the evolution of the O(3P) concentration above the surface and the gas temperature by simulation of the rotational spectrum of the transition. Surface reactions contribute to the heating in the sample and to a substantial increase in the gas temperature. Finally, a strong correlation between the time evolutions of the transition intensity and the sample temperature is observed, suggesting that O(3P) is the main reactive species that produces the heating and the chemical changes in the HTC.

The surface of ethylene-propylene-diene monomer (EPDM) rubber was treated in N2/Ar and N2/H2/Ar RF plasmas in order to achieve similar or better adhesion properties than NBR (acrylonitrile-butadiene) rubber, nowadays used as thermal protection of rocket chambers. The surface properties were studied by contact angle measurements and by x-ray photoelectron spectroscopy (XPS). The treated surfaces of the EPDM samples show a significant reduction in the contact angle measurement, indicating an increase in the surface energy. XPS analyses show the incorporation of polar nitrogen- and oxygen-containing groups on the rubber surface. After plasma treatment the presence of oxygen is observed due to surface oxidation which occurs when the samples are exposed to the air. Atomic force microscopy and scanning electron microscopy analyses indicate a decrease in the EPDM rubber surface roughness, promoted by surface etching during the plasma treatment. Strength tests indicate improvement of about 30% and 110% in the adhesion strength for the plasma treated EPDM/polyurethane liner interface and for the EPDM/epoxy adhesive interface, respectively. The adhesion strength of the EPDM/liner is similar to that obtained for the NBR/liner, which indicates that EPDM rubber can safely be used as thermal protection of the solid propellant rocket chamber. © 2007 IOP Publishing Ltd.

The actual technology of solid propellant rocket of the Brazilian Space Program uses NBR (acrylonitrile-butadiene) rubber as thermal protection of the rocket chamber. However, the NBR has high density, is very expensive, and liberates toxic byproducts during the propellant burning. One interesting alternative to the NBR is the EPDM (ethylene-propylene-diene monomer) rubber, which possesses excellent mechanical and thermal properties, low density; low process cost and is environment friendly. Nevertheless, it has non-polar surface and consequently low adhesion properties. In order to improve the adhesion of the propellant to the rubber surface, the later must be activated. Cold plasma is a technology that offers a more economical, rapid, and environmental friendly rubber surface treatment, once the treatment is done using non-toxic gases. This technique also allows us to treat the rubber surface without affect the rubber bulk properties. In this work we present the results on the plasma surface treatment of EPDM performed in RF glow discharge using gas mixtures of O2/Ar, N2/H2/Ar and N2/Ar. The treated and non-treated rubber surfaces were analyzed by contact angle measurements. The adhesion strength test indicates that plasma treated EPDM rubber is a strong candidate to be used as thermal protection of rocket chambers. Copyright IAF/IAA. All rights reserved.

This article reports on the effect of the increase of substrate temperature due to the plasma discharge on the crystalline structure of the TiO2 thin films deposited on silicon by the magnetron sputtering technique. The influence on the film crystallinity was evaluated as a function of process parameters, such as, substrate-to-target distance and reactive gas concentration. The substrate holder was equipped with two thermocouples in order to measure simultaneously the substrate temperature Ts and the substrate surface temperature Tsurf during the deposition. The films were analyzed by X-ray diffractometry (XRD) and profilometry. Results show that the critical temperature to obtain crystalline films depends upon the gas composition and it varies from 170°C - 210°C for oxygen concentration in the gas mixture varying from 20 to 100%. © The Electrochemical Society.

Due to the excellent thermal and mechanical properties, the EPDM rubber is used as protective film in the aerospace industry. However, its chemical composition and structure do not allow good adhesive properties, making necessary a surface treatment to improve adhesion properties. Most of the conventional chemical methods make use pollutant solvents. Cold plasma is a clean technology that becomes an important alternative for treating these material surfaces. In this work we present a study of the EPDM rubber surface treatment by plasma. The process was conducted in a RIE plasma system excited by r.f. power using N 2 and Ar gas mixtures. A significant improvement of the surface properties regarding to the adhesion properties was obtained. An optimization of the plasma parameters, such as gas ratio mixture, rf power, total gas pressure and treatment time is presented. The rubber surface properties were analyzed by goniometry and AFM. © 2007 WILEY-VCH Verlag GmbH & Co. KGaA.

Amorphous and crystalline AlN thin films were deposited on Si (100) substrates by off-axis hollow cathode magnetron technique. The evolution of the crystalline orientation and the morphology of AlN thin films have been investigated depending on the nitrogen concentration. It has been demonstrated by using a combination of mass spectrometry, X-ray diffraction and atomic force microscopy techniques, that the film crystallinity and surface roughness are related with the nitrogen concentration. The results show that the monitoring of Al+ and AlN+ species by mass spectrometry proved to be an important new method to prescribe the plasma conditions for growing amorphous or crystalline films. © 2006 Elsevier B.V. All rights reserved.

This work presents the adhesion properties of plasma treated EPDM (ethylene propylene diene monomer) vulcanized rubber used in missile and rocket manufacturing. The EPDM rubber surface was treated in a RIE (reactive ion etching) plasma reactor using two different gas mixtures, oxygen/argon and nitrogen/argon. Contact angle measurements were used to obtain the dispersive and polar components of the surface tension of the treated samples, and FT-IR was used to characterize the surface. Both plasma treatments promote an enhancement of the adhesive properties of the EPDM rubber. However, the improvement factor depends on the gas mixture used. For treatment with an oxygen/argon mixture, functional groups such as C-O, C=O, O-C=O, C-O-O and CO3 are formed in the rubber surface. In the case of a nitrogen/argon mixture, the functional groups formed on the surface are C-N, C=N and C=N, beyond the functional groups C-O, due to the rubber oxidation. Therefore, the higher polarity of nitrogen containing groups makes the treatment with the nitrogen/argon mixture more efficient.

Mass spectrometry (MS) and optical spectroscopy have been used to study the residual gas formed during hydrogen plasma debinding of polypropylene from powder injection moulded parts. Mass spectra show that the residual gas formed during the debinding process presents a large number of aliphatic compounds and a certain difficulty in their identification. However, it was possible to identify the presence of propylene, methane, acetylene and ethane. Optical spectroscopy also shows the presence of CH radicals. The end point of the debinding process can easily be monitored by following the temporal evolution of the CH radical and the different ions by optical spectroscopy and MS, respectively.

Growing demands for increased shelf-life of food products and chemical inertia of the contact surfaces have stimulated development of polymers with improved high-barrier properties. Our objectives in this article are (1) to describe experimental results on Plasma-enhanced chemical vapor deposition (PECVD) and its importance to produce thin layers of inorganic glassy barrier materials for food, pharmaceutical, and organic display applications; (2) despite the thereby greatly enhanced quality of film or rigid packaging material, some residual coating defects result in less-than-perfect gas, moisture and aroma barriers: an innovative technique based on reactive ion etching (RIE) in oxygen plasma is also presented, along with a staining method, which render even sub-μm coating defects visible. Data are shown for oxygen transmission rate on virgin and defective coatings, and the industrial context and applications are presented.

Ultra-thin layers of SiO2 and SiN prepared, for example, by plasma-enhanced chemical vapor deposition (PECVD) are increasingly used as gas barriers on flexible polymeric materials and of plastic containers. Despite the excellent barrier properties provided by these materials, all published data show some residual permeation, even when the barrier coatings are relatively thick (≥70 nm). This residual permeation is attributed to the presence of microscopic defects in the coatings. In this article we present new techniques, based mainly on reactive ion etching in oxygen plasma, to render visible micrometeror sub-micrometer-sized defects in transparent ceramic films on polymers. These techniques can be used to visualize and better understand the origins of defects in these coatings on a microscopic scale, as well as for mapping and counting defect density on a macroscopic scale (tens of cm2 or more).Ultra-thin layers of SiO2 and SiN prepared, for example, by plasma-enhanced chemical vapor deposition (PECVD) are increasingly used as gas barriers on flexible polymeric materials and of plastic containers. Despite the excellent barrier properties provided by these materials, all published data show some residual permeation, even when the barrier coatings are relatively thick (≥70 nm). This residual permeation is attributed to the presence of microscopic defects in the coatings. In this article we present new techniques, based mainly on reactive ion etching in oxygen plasma, to render visible micrometer-or sub-micrometer-sized defects in transparent ceramic films on polymers. These techniques can be used to visualize and better understand the origins of defects in these coatings on a microscopic scale, as well as for mapping and counting defect density on a macroscopic scale (tens of cm2 or more).

We describe new techniques, based mainly on reactive ion etching (RIE) in oxygen plasma, to render visible micrometer- or sub-micrometer-sized defects in transparent barrier films on transparent polymers. These techniques can be used to characterize and better understand the origins of defects in these coatings on a microscopic scale, as well as for mapping and counting defect density on a macroscopic scale (tens of cm2 or more). © Springer-Verlag 1999.

A method has been developed to visualize defects in the coatings, which allows to analyze (and to map) the surface of samples up to hundreds of cm2 in size or more. The method, based on oxygen plasma etching, renders defects visible by optical microscopy. The method can also provide information about defect patterns on a macroscopic scale, thus facilitating diagnostics and improvement of fabrication procedures.

A model for gas permeation through defects in barrier coatings is described. The model allows to evaluate permeation through a single- or through multiple circular defects in the coating, also in special cases of size distributions and non-cylindrical symmetry.

The "interphase" region between the deposited layer [e.g., plasma-enhanced chemically vapor deposited (PECVD) SiO2 or SiN] and the polyethylene terephthalate) (PET) substrate has been investigated and compared to physical vapor deposited (PVD) (electron beam evaporated) SiO2. Composition profiles determined by time-of-flight elastic recoil detection, electron microprobe analysis, and x-ray photoelectron spectroscopy all show an extended interphase region more than 50 nm in width, while the profile of the PVD SiO2 is narrower. However, since these analytical techniques are invasive and prone to artifacts, we have also examined ultrathin (about 10 and 20 nm) SiO2 and SiN PECVD layers on 50 nm spin-coated PET substrates by nondestructive infrared (IR) techniques. The IR spectra confirm that the thin PECVD deposits also comprise an organosilicon phase with Si-CHx bonds. We explain these observations in terms of a fragmentation/redeposition mechanism: During the earliest stage of PECVD, interaction between the plasma and the polymer surface produces volatile organic species, which intermix with the reagent gas feed, thus giving rise to the observed organosilicon-like deposit with gradually decreasing carbon content. © 1998 American Vacuum Society.

Transparent barrier coatings on polymers are receiving much attention in industry, for pharmaceutical, food and beverage packaging applications. Plasma-enhanced chemical vapor deposition (PECVD) is among several competing techniques which can produce thin layers of inorganic glassy barrier materials. In this article we describe the performance of silicon compounds (SiO2 and Si3N4) on 13 μm polyethylene terephthalate (PET) substrates, the barrier coatings being deposited in a dual-frequency (microwave/radio frequency) pilot-scale PECVD reactor for continuously moving flexible webs up to 30 cm in width. The volatile silicon compound used for SiO2 deposition is HMDSO (C6H18Si2O), while SiH4 serves to deposit Si3N4. Coating thicknesses, d, in the range 8 nm≤d≤200 nm, are measured using a variety of techniques, namely stylus profilometry, continuous wavelength optical interferometry, x-ray fluorescence, variable angle spectroscopic ellipsometry, and transmission electron microscopy, while film compositions are determined by x-ray photoelectron spectroscopy. Oxygen transmission (OTR) and water vapor transmission (WVTR) measurements are carried out with MOCON "Oxtran" and "Permatran-W" instruments, respectively. As also reported by other workers, we typically find OTR values of about 0.5 scc/m day and WVTR about 0.3 g/m day, for barrier thicknesses exceeding a "critical" value (dc, about 15 nm), but the minimum permeation values depend upon the concentration of defect sites in the coating (mostly related to substrate microroughness). In order to confirm this correlation, we have developed a technique combining reactive ion etching through the PET, followed by optical and transmission electron microscopies, to characterize the types and number densities of coating defects. On the basis of these, we find good agreement between measured and calculated values of OTR. © 1998 American Vacuum Society.

Thin, transparent ceramic coatings on polymers are effective barriers against gas and vapor transmission. However, they always display some residual permeation, which can be attributed to defects. The main sources of these defects are dust particles on the polymer surface before deposition, and roughness of the polymer surface due to the presence of so-called antiblock particles. The transparency and extreme thinness of the films (d≈50 nm) render the detection of defects virtually impossible by optical and even by electron microscopies. However, by using a technique based on reactive ion etching (RIE) in oxygen plasma, we are able to render defects visible, even by optical microscopy at relatively low magnification (100×). In the present article we present a confocal microscopy study, which has helped to better understand the effect of RIE at defect sites, as well as the origins of the defects in these coatings.

Plasma-enhanced chemical vapor deposition (PECVD) is among several competing techniques which can produce thin layers of inorganic glassy barrier materials for packaging and related applications. In this paper we describe the performance of SiO2 on 13 μm PET substrates, the barrier coatings being deposited from organosilicon (HMDSO) precursor. Microwave (MW), radiofrequency (RF), or dual-frequency plasmas are generated in a pilot-scale PECVD reactor for continuously-moving webs up to 30 cm in width. Coating thicknesses, d, in the range 8 nm≤d≤200 nm, have been examined, where d is measured by a variety of techniques, including spectroscopic ellipsometry, x-ray fluorescence, and transmission electron microscopy (TEM), while film compositions are determined by x-ray photoelectron spectroscopy (XPS). As also reported by other workers, typical values of oxygen permeation (OTR) are about 0.4 scc/m2-day, provided d exceeds a certain `critical' value, dc. The residual permeation has been correlated with the existence of coating defects, mostly resulting from substrate microroughness. We have developed a technique based on reactive ion etching (RIE) and undercutting under defect sites, which render these readily detectable by optical microscopy. This, in turn, has allowed us to characterize the types and number densities of coating defects, and to correlate these with OTR measurements.

Thin films of silicon nitride or -oxide (SiN and SiO2) on flexible or rigid polymeric substrates are receiving much attention in numerous application areas, since they are excellent barriers against the permeation of gases (e.g. O2) or vapors (e.g. H2O), are hard, optically transparent, and chemically resistant. In this laboratory SiN and SiO2 films are deposited onto polyethylene terephthalate (PET) using `dual'-frequency (microwave-radiofrequency) plasma-enhanced CVD (PECVD). Such films adhere very well to the polymer substrates, a likely reason for this being found in an extended `interphase' region. In this paper we report results obtained by probing the interphase by various complementary destructive and non-destructive techniques (ERD, XPS, ATR-FTIR, IRRAS, and spectroscopic ellipsometry). The measured thickness of the interphase is found to range from a few tens to about 80 nm, and all the above-mentioned techniques identify it to be an `organosilicon' layer of varying composition. We propose a fragmentation/redeposition mechanism at the earliest stage of the coating process, during which the plasma-surface interaction leads to a mobilization of volatile organic fragments from the polymer surface into the plasma; these fragments intermix with the feed-gas, and then re-deposit in the form of the observed organosilicon interphase region.