Radio Frequency Glow Discharge Research Articles

Diminished fracture initiation sites in ceramic layers bonded to glow-discharge treated substructure

A mechanically retentive structure and meticulous surface cleanliness are critical factors in providing fracture resistance and clinical success of metal ceramic restorations. This investigation compared the porcelain/metal interfaces of deliberate compressive fractures of ceramic crowns between conventional preparation and application of the Radio Frequency Glow Discharge Treatment (RFGDT) before each bonding step. It evaluated RFGDT’s capacity to improve wetting effectiveness and minimize porosity. Twelve metal ceramic crowns were fabricated identically. RFGDT was applied to the metal substructures of half the specimens before the ceramic layering process. All specimens were fractured in the same manner by an applied compressive force to simulate dental occlusive failure. Fracture surfaces were inspected by light and scanning electron microscopy. Quantitative analyses of images were performed to identify numbers, locations of cracks, porosity patterns, and other morphological correlates of the fracture zones. There were significantly fewer voids per millimeter at the interfaces in the RFGDT group than in the non-RFGDT group (t = 2.377, df = 9, p = 0.021). There was a significant difference in the number of horizontal cracks per millimeter between the groups (t = 2.132, df = 7, p = 0.035), with more cracks occurring in the non-RFGDT group. RFGDT can improve the integrity of metal ceramic crowns by increasing the substratum surface energy, improving porcelain wetting and spreading and thereby diminishing the numbers of interfacial voids available for initiation of fracture. Routine application of RFGDT should result in fewer cracks along metal/ceramic interfaces in all restorative preparations.

Certified reference materials for quantification of vanadate species in anodic alumina Rf-GDOES depth profiles

Certified reference materials (CRM) for quantification of Radiofrequency Glow Discharge Optical Emission Spectrometry (Rf-GDOES) depth profiles of anodic oxide films are very limited. This paper demonstrates that CRM's for quantification of electrolyte-derived species can be more reliably obtained for inwardly mobile species (phosphorus) than for outwardly mobile species (vanadium) when anodising superpure aluminium in their respective solutions at several current densities. Superpure aluminium specimens were anodised to 150 V, in sodium metavanadate solution, at current densities 5, 10, 15, 20, 25 and 50 mA cm−2. Sufficiently different concentrations were obtained by RBS for the outwardly mobile vanadate species (0.68, 0.75, 0.13, 0.06, 0.09 and 0.13 at%) compared with 1.19, 1.42, 1.48, 1.49, 2.08 and 2.37 at% for the inwardly mobile phosphorus species. Evidently greater concentrations of phosphorus species are incorporated into the oxide film. Significant reduction in vanadium concentrations with current density correspond to a large destabilisation of the V2O7− ion by the anodising electric field. Quantitative depth profiles are determined by means of calibration plots for vanadium and phosphorus. Excellent quantification accuracy of <±0.06 at% is obtained for inwardly mobile phosphorus species by comparing the concentration determined by Rutherford Backscattering Spectroscopy (RBS) with concentration obtained directly from the quantified Rf-GDOES depth profile whereas significantly less accurate quantification accuracies are obtained for the outwardly mobile vanadium species. Quantification accuracy for depth is excellent at ±1 nm as validated by Transmission Electron Microscopy (TEM). CRM's of inwardly mobile impurity species obtained by anodising at different current densities are therefore more reliable and accurate than those of outwardly mobile species.

Surface Modification of the Polyethersulfone Membrane by Low Pressure Argon Plasma Treatment

In this study, low pressure Ar plasma is used to improve the surface hydrophilicity of the polyethersulfone (PES) membrane. The low pressure Ar plasma generated by radio frequency (RF) glow discharge was acted on the PES membrane surface to observe the change of the hydrophilic nature. This paper discusses the different plasma power, treatment time and plasma fluxes conditions on PES membrane modified influence. Experimental results show that with the plasma power and plasma fluxes increase and treatment time prolonged, the surface hydrophilicity of the PES membrane continues to increase and no more changes were observed when it reached to a certain value. The best condition was carried out at 60W, 120s, 20sccm, in this condition, the hydrophilic nature of the PES membrane is remarkably improved.

Studies on the Physical Characteristics of the Radio-Frequency Atmospheric-Pressure Glow Discharge Plasmas for the Genome Mutation of Methylosinus trichosporium

In this paper, both simulations and experiments are conducted to investigate the physical characteristics of the radio-frequency atmospheric-pressure glow discharges (RF APGDs) first. The experimental and modeling results show that there are abundant chemically reactive species, e.g., electrons, helium metastables and ions, with high number densities in the discharge region. The corresponding plasma jet temperatures are in the range of 27°C - 39°C with the power input lower than 120 W, which is suitable for the treatment of the biomolecules or cells. Then, a prototype, which is the so-called atmospheric and room-temperature plasma mutation system, is designed with the RF APGD plasma generator as the core component. As an example, it is used for the mutation breeding of Methylosinus trichosporium OB3b. The experimental results show that the RF APGD plasma source is an environmentally friendly and efficient tool for the genome mutation of microorganisms to construct mutant library with large diversity.

The 7th international conference on instrumental methods of analysis: modern trends and applications (IMA 2011)

The 7th international conference “IMA 2011, Instrumental methods of analysis: modern trends and applications” was held from 18–22 September, 2011, in Chania (west Crete), which presents an excellent combination of cultural life, natural beauty (numerous beaches, gorges such as the renowned Samaria gorge, high mountains, biodiversity, etc.), a Venetian old town and many archaeological sites. The conference was held at the Conference Centre of theMediterraneanAgronomic Institute of Chania/Centre International de Hautes Etudes Agronomiques Mediterraneennes (MAICh/CIHEAM). This is a conference centre conceived with respect for the environment, situated 3 km from the centre of Chania on the campus of the institute. IMA 2011 is the seventh conference in this series, which started in 1999 in Chalkidiki, Macedonia, Greece, under the chairmanship of Professor M. Ochsenkuhn-Petropoulou and there has been a conference every 2 years since then organized by different other Hellenic academic institutions. IMA 2011 provided an excellent framework for the presentation of new concepts, instruments, methods, systems and applications in the area of modern chemical analysis. Researchers and scientists from universities, research institutions, state organizations and industry were in attendance and presented their experiences in the current state of the art in the area of instrumental methods of analysis. Furthermore, IMA 2011 provided grounds for graduate and postgraduate students to disclose their projects, discuss scientific collaborations with other groups, as well as to explore employment opportunities. IMA 2011 was organized with the cooperation of two of the most important Cretan institutes: the Technical University of Crete (Analytical and Environmental Chemistry Laboratory) and the MAICh/CIHEAM. Co-organizers were other Hellenic academic analytical chemistry institutions actively involved in former IMA conferences. The conference was opened by Professor Y. Phillis, Rector of the Technical University of Crete. Honorary prizes were awarded to Professor Elo Hansen, Denmark, and Professor Antonius Kettrup, Germany, for their top contributions in the field of analytical chemistry. Presentations were given in the fields of bioanalytics, speciation, sensors, materials science and nanomaterials, mass spectrometry, environmental analysis, chromatography, X-ray analysis and atomic absorption spectrometry over the 5 days of the conference. The scientific framework consisted of 14 sessions, 2 of which were held in parallel. Each session was introduced by a plenary lecture conducted bywell-known invited scientists experienced in the respective fields from all over the world, for example, A. Sanz-Medel (Pulsed radiofrequency glow discharge time-of-flight mass spectrometry for isotopes, elements, molecules and nanostructured materials), R. Lobinski (High-resolution molecular mass spectrometry in the analysis of heteroatom-containing molecules), B.Michalke (Element speciation in neurodegenerative disease investigation—focus on manganese), G. Hieftje (New instruments for mass spectrometry),W. Lindner (Potential of chiral ion exchanger for chromatographic resolution of stereoisomers), and chaired by experts in instrumental methods of analysis. Published in the special paper collection Instrumental Methods of Analysis (IMA 2011) with guest editors Maria OchsenkuehnPetropoulou, Nikos Kallithrakas and Panagiotis Kefalas

Depth-profile analysis of thermoelectric layers on Si wafers by pulsed r.f. glow discharge time-of-flight mass spectrometry

In this work the depth-profile analysis of thermoelectric layers deposited on Au and Cr covered Si wafers with the aid of pulsed radiofrequency glow discharge time-of-flight mass spectrometry (pulsed RF-GD-TOFMS also called plasma profiling TOFMS (PP-TOFMS™)) is described. For thermoelectric materials the depth resolutions obtained with both PP-TOFMS and secondary ion mass spectrometry (SIMS) are shown to be well comparable and in the order of the roughness of the corresponding layers (between 20 and 3700nm). With both methods a direct solid analysis without any preparation steps is possible. In addition, the analysis of the samples with PP-TOFMS proved to be faster by a factor of 26 compared to SIMS, as sputtering rates were found to be 80nms−1 and 3nms−1, respectively.For the analyzed samples the results of PP-TOFMS and SIMS show that a homogeneous deposition was obtained. Quantitative results for all samples could also be obtained directly by PP-TOFMS when the stoichiometry of one sample was determined beforehand for instance by inductively coupled plasma optical emission spectrometry (ICP-OES) and scanning electron microscopy energy dispersive X-ray fluorescence spectrometry (SEM-EDX). For Bi2Te3 the standard deviation for the main component concentrations within one sample then is found to be between 1.1% and 1.9% and it is 3.6% from sample to sample. For Sb2Te3 the values within one sample are from 1.7% to 4.2% and from sample to sample 5.3%, respectively.

A hybrid heterojunction with reverse rectifying characteristics fabricated by magnetron sputtered TiOx and plasma polymerized aniline structure

A TiOx film produced by direct current reactive magnetron sputtering without substrate heating or post-deposition annealing and a plasma polymerized aniline (PPA) structure deposited in the same reactor by a radio-frequency glow discharge without the assistance of a carrier gas are used for the fabrication of a heterojunction. The gas phase discharge is investigated by a Langmuir probe and optical emission spectroscopy. The individual layers and the heterojunction are characterized for structural and optoelectronic properties. PPA has polymer-like structure and texture and is characterized by saturated–unsaturated, branched and crosslinked networks. X-ray photoelectron spectroscopy reveals a slightly reduced TiOx surface, which exhibits near band edge luminescence. The free radicals trapped in PPA readily react with oxygen when exposed to atmosphere. The heterojunction shows reverse rectifying characteristics under dark and ultraviolet (UV) irradiation. The energy levels of TiOx and PPA might exhibit reverse band bending and electrons and holes are accumulated on both sides of the heterojunction. The charge accumulation phenomena at the interface may play a key role in the device performance of a hybrid heterojunction. The current–voltage characteristic of the heterojunction is sensitive to UV light, so the structure may be used for photo-sensing applications.

Effect of Nitrogen-Rich Cell Culture Surfaces on TGF BETA and MAPK Signaling in Intervertebral Disk Cells

IntroductionLow back pain, often due to intervertebral disk (IVD) degeneration, is an age-associated disorder that afflicts more than half of the population, above age 70. Discs are composite struc...

Effect of Nitrogen-Rich Cell Culture Surfaces on TGF BETA and MAPK Signaling in Intervertebral Disk Cells

Effect of Nitrogen-Rich Cell Culture Surfaces on TGF BETA and MAPK Signaling in Intervertebral Disk Cells

Inhomogeneous nanostructured honeycomb optical media for enhanced cathodo- and under-x-ray luminescence

Photo-, radio-, and pulse cathodoluminescence spectra from sol-gel derived titania, doped with strontium and terbium, deposited on porous anodic alumina (PAA) films are reported. The morphology and qualitative elemental depth distributions have been examined by transmission electron microscopy, scanning electron microscopy, and radio-frequency glow discharge optical emission spectroscopy. PAA films with pore and cell sizes ranging from 170 to 190 and 240 to 270 nm, respectively, have been generated on aluminum and monocrystalline silicon substrates followed by spin-on sol-gel derived coating with the subsequent thermal treatment. The resultant PAA surface is not coated with a continuous xerogel film; the xerogel is mainly distributed near the pore bases, leaving much of the pore volume unfilled. The xerogel/PAA structures reveal terbium-related luminescence under x-ray excitation and cathodoluminescence. The same xerogels generated on monocrystalline silicon revealed no cathode- or under-x-ray luminescence. Thus, PAA enhances strongly the cathode- and under x-ray luminescence from terbium and strontium-doped titania xerogels confined in the porous matrix. The fabricated structures are considered as a type of low-cost, thin-film convertor of x-rays, and cathode ray irradiation into visible light, with an average cell size of the convertor of about 250 nm.

One-Dimensional Modeling on the Asymmetric Features of a Radio-Frequency Atmospheric Helium Glow Discharge Produced Using a Co-Axial-Type Plasma Generator

In this paper, a one-dimensional transient fluid model is used to investigate the asymmetric characteristics of the radio-frequency atmospheric-pressure helium glow discharges produced using a co-axial-type plasma generator. Based on the analysis of the particle and energy balance processes in the discharge region, the modeling results show that the asymmetric features of the time-averaged plasma parameters, e.g., the species number densities, electron energy and the electric field, become significant resulting from the increase in the discrepancy between the surface areas of the inner and outer electrodes. And the influence of the inner electrode radius on the asymmetric features of the discharges becomes more significant compared with the electrode gap spacing for the cases with smaller inner electrode radius. The calculated asymmetric features of the discharges are also validated by the experimental analysis on the discharge images using the visible image processing technique qualitatively.

Films thickness effect on structural and optoelectronic properties of hydrogenated amorphous germanium (a-Ge:H)

Thin films of hydrogenated amorphous germanium (a-Ge:H) deposited at high growth rate by radiofrequency (RF) glow discharge with 1sccm GeH4 diluted in 40sccm H2 have been studied. The effect of the films thicknesses on the defect density and on the structural parameters was carefully investigated by means of infrared spectroscopy, optical transmission measurements, and the photothermal deflection spectroscopy (PDS) technique. The results of this investigation show that when the films thicknesses increase, the total hydrogen content (CH) decreases and the hydrogen-bonding configuration changes. The results of these changes appear clearly on the defects density and on the microstructure parameter of the films, while the disorder parameter EOV and the optical gap ET remain practically constant (EOV≈45±2meV,ET=1.08±0.02eV). The improvement of these parameters is mainly due to the incorporation of the hydrogen in the bulk of the material as the monohydride groups (Ge-H) rather than the polyhydride groups (Ge-H2 and Ge-H2n) when the films thicknesses increase.

Analytical glow discharge mass spectrometry

Various types of glow discharge mass spectrometric systems as well as their applications are considered. Special attention is paid to radiofrequency and pulsed glow discharges combined with time-of-flight mass spectrometers. Along with typical application fields of glow discharge mass spectrometry, analysis of semiconductors, polymers, and dielectrics, as well as isotope analysis and depth profiling are also reviewed. Some methods of standard-free mass spectrometric analysis of solids are considered. Prospects for combining glow discharge mass spectrometry with preliminary chromatographic separation are discussed.

Energy dispersive spectroscopy study of surface modified PEEK

PEEK (polyether etherketone) polymer, is increasingly used in many industrial applications as a replacement for metal components. In this investigation, attention is given to understand the chemical changes that have been introduced on the surface of PEEK, when surface of the PEEK is modified by low pressure plasma under RF (radio frequency) glow discharge. The contact angle measurements show that the contact angle decreases after the plasma treatment which results in the increase in surface energy. This paper also discusses the common surface characterisation technique like Energy Dispersive Spectroscopy (EDS) analysis to determine the chemical changes that have been introduced on the surface.

Immobilized carbonic anhydrase on hollow fiber membranes accelerates CO2 removal from blood

Current artificial lungs and respiratory assist devices designed for carbon dioxide removal (CO(2)R) are limited in their efficiency due to the relatively small partial pressure difference across gas exchange membranes. To offset this underlying diffusional challenge, bioactive hollow fiber membranes (HFMs) increase the carbon dioxide diffusional gradient through the immobilized enzyme carbonic anhydrase (CA), which converts bicarbonate to CO(2) directly at the HFM surface. In this study, we tested the impact of CA-immobilization on HFM CO(2) removal efficiency and thromboresistance in blood. Fiber surface modification with radio frequency glow discharge (RFGD) introduced hydroxyl groups, which were activated by 1M CNBr while 1.5M TEA was added drop wise over the activation time course, then incubation with a CA solution covalently linked the enzyme to the surface. The bioactive HFMs were then potted in a model gas exchange device (0.0084 m(2)) and tested in a recirculation loop with a CO(2) inlet of 50mmHg under steady blood flow. Using an esterase activity assay, CNBr chemistry with TEA resulted in 0.99U of enzyme activity, a 3.3 fold increase in immobilized CA activity compared to our previous method. These bioactive HFMs demonstrated 108 ml/min/m(2) CO(2) removal rate, marking a 36% increase compared to unmodified HFMs (p < 0.001). Thromboresistance of CA-modified HFMs was assessed in terms of adherent platelets on surfaces by using lactate dehydrogenase (LDH) assay as well as scanning electron microscopy (SEM) analysis. Results indicated HFMs with CA modification had 95% less platelet deposition compared to unmodified HFM (p < 0.01). Overall these findings revealed increased CO(2) removal can be realized through bioactive HFMs, enabling a next generation of more efficient CO(2) removal intravascular and paracorporeal respiratory assist devices.

Spatial emission distribution of a pulsed radiofrequency glow discharge: Influence of the pulse frequency

A pulsed radiofrequency Glow Discharge (pulsed rf GD) plasma has been spectroscopically characterized by performing side-on measurements of the emitted radiation. The effect of varying the pulse frequency (e.g. between 100 and 10,000Hz), while keeping the duty cycle constant at 25%, has been investigated on different argon and analyte (i.e. copper) emission lines, at different plasma locations. In particular, it is observed that an intermediate frequency of 2.5kHz favors the excitation of the argon atoms, while the argon ions are preferably excited by lower frequencies (e.g. longer pulse widths). Moreover, the excitation of copper atoms has a strong dependence on the upper energy level, and it has been noticed that the emission from higher levels is favored by the use of lower pulsed-rf frequencies. On the other hand, it has been found that the spatial distribution of the gas species and the analyte species (i.e. Ar and Cu, respectively) differ from each other: the atomic argon emission extends longer along the plasma plume than the atomic copper emission. Furthermore, ionic species have their maximum emission signal in the region close to the anode; however, their emission signal decay quite fast at increasing distances to the anode. Nevertheless, it should be highlighted that it is possible to detect ionic emission at distances far away from the negative glow; in regions where usually the sampler cone interface is placed in GD-MS instruments.

Oxidation Resistance and Self Hardening of CrAlN/BN Nanocomposite Coatings

CrAlN/BN nanocomposite coatings were deposited on mirror-polished silicon wafer and high-speed steel (HSS) substrates using reactive cosputtering, i.e., pulsed dc and rf sputtering of CrAl and h-BN targets, respectively. Further, the oxidation resistance of the obtained coatings was investigated. The CrAlN/BN coating exhibited superior oxidation resistance properties when compared with those of the CrAlN coatings; after annealing the sample at 800 °C in air for 1 h, the plastic hardness value of the CrAlN coatings decreased to 50% of the as-deposited hardness value; in contrast, the CrAlN/BN coatings exhibited self-hardening phenomena from 700 to 800 °C in the range of 5 to 30%. In particular, the CrAlN/18 vol% BN coatings showed an increase of approximately 30% in hardness values, and a maximum hardness value of approximately 50 GPa was reached after annealing the sample at 800 °C in air. The plastic hardness value hardly changed when the sample was annealed up to 800 °C in nitrogen and argon; this result was contrary to the result obtained for the sample that was annealed in air. The radiofrequency glow discharge optical emission spectroscopy (rf-GD-OES) analysis of the CrAlN/18 vol% BN coating annealed in air revealed that the coating has an oxide layer deposited on the surface to a depth of ~200 nm. Conventional transmission electron microscopy (TEM) observations of the same coating indicate that the columnar structure was disrupted by a thin layer (30–40 nm) of the coating annealed in air. The indentation hardness value of the annealed coating was measured using Ar ion sputtering before and after etching of the annealed surface. Subsequently, when the oxide layer was etched to a depth of 200 nm from the surface, the hardness value decreased from approximately 48 GPa to 43 GPa; this result was similar to the results obtained for the as-deposited coating.

Modeling and Experimental Study of SiH4/GeH4/H2 Gas Discharge for Hydrogenated Silicon Germanium Deposition by RF PECVD

ABSTRACTA one-dimensional model has been developed for radio frequency (RF) glow discharge of SiH4/GeH4/H2 3-gases mixture at a high pressure regime based on the fluid model. The behavior of electrons, neutrals, radicals and ions with corresponding rate constants is described by driftdiffusion equations that are coupled with the Poisson’s equation and solved with an explicit central-difference discretization scheme. The germanium (Ge) content in the deposited film and germane (GeH4) radical fraction in the gas phase are found to decrease as total gas pressure increases in contrast to the increased deposition rate, which are explained by the fact that GeHx-group species are more thoroughly depleted and less promoted by the denser plasma at high pressure compared to SiHx-group species. The multiplied population of electrons and hydrogen atoms in the quadratically denser plasma also boosts secondary reactions which are favorable for SiH3 and GeH3 and consume SiH2 and GeH2for high order radicals.

Numerical Study on Collision-Less Plasma Sheaths of RF-Glow Discharge

Abstract A self-consistent mathematic model for radio frequency (RF) glow discharge was proposed to investigate the spatiotemporal evolvement of collision-less plasma sheaths at different plasma characteristics, in which the influences of ion motion by instantaneous sheath electric field were considered and the present model would be suitable for describing the spatiotemporal characteristics plasma sheaths with wide RF-frequency ranges. The instantaneous relationship between the voltage on the RFbias electrode and the sheath thickness was determined by an equivalent circuit model coupled with a fluid model. The periodic distributions of voltage on RF-bias electrode, sheath thickness, sheath electric field, density of ion and electron in sheath were obtained by numerical methods based on the present model. It was found that the distribution of electrode voltage presents nonsinusoidal waveform which is different from the sinusoidal waveform assumptions of other researches. The numerical computation results show that β, the ratio of RF frequency and ion plasma frequency, is an important parameter that affects RF plasma sheath's features: the motion and density distribution of ion are mostly controlled by instantaneous sheath electric field if β 1, the ion motion could be determined by the average field intensity of plasma sheath, and the ion density could almost not be changed.

Low Temperature Plasma Synthesis of Nanocrystals and their Application to the Growth of Crystalline Silicon and Germanium Thin Films

ABSTRACTWe summarize our research studies on the synthesis of silicon and germanium nanocrystals and their application to the growth of a variety of thin films, spanning the range from fully disordered amorphous up to fully ordered crystalline. All these films are deposited in a standard radio-frequency glow discharge system at low temperature (~200 °C). We show how the plasma synthesis of silicon nanocrystals, initially a side effect of powder formation, has become over the years an exciting field of research which has opened the way to new opportunities in the field of materials deposition and their application to optoelectronic devices. Our results suggest that epitaxy requires the melting/amorphization of the nanocrystals upon impact on the substrate, the subsequent epitaxial growth being favored on (100) c-Si substrates. As a consequence, the control of the impact energy is a critical aspect of the growth which will require new strategies such as the use of tailored voltage waveforms.