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A one-dimensional, kinetic model of inverted sheath formation in a plasma system bounded by two infinitely large planar electrodes (the source and the collector) has been developed for the first time. It is assumed that ions and electrons are injected into the system from the source with half-Maxwellian distributions, and emitted electrons are also injected from the collector with a half-Maxwellian distribution. It is assumed that the potential increases monotonically from the source to the collector. Consequently, the distribution functions of ions, electrons, and emitted electrons anywhere in the system can be written as functions of the potential. Zero and first moments of the distribution functions give particle densities and fluxes. From these, the floating condition for the collector is derived and the Poisson equation is written. The first integrals of the Poisson equation give the conditions for the electric field at the source and at the collector. The model consists of five basic equations: (1) collector floating condition, (2) neutrality condition at the inflection point of the potential, (3) source electric field condition, (4) collector electric field condition, and (5) Poisson equation. The model contains nine parameters. Five of them are plasma parameters: (1) ion mass μ, (2) ion temperature τ, (3) ion source strength α, (4) temperature of emitted electrons σ, and (5) emission coefficient ε. Then there are two potentials, (1) floating potential of the collector Ψ C and potential at the inflection point Ψ P and (2) electric fields, (1) electric field at the collector ηC and (2) electric field at the source ηS. If five of them are selected, the other four can be found from the system of equations (1)–(4). Numerical solutions of the Poisson equation give axial profiles of the potential, electric field, and space charge density. The model can be used for parametric analysis of the inverted sheath formation. Usually μ, τ, α, ε, and σ are selected and then Ψ C , Ψ P , ηC, and ηS are found from the system of equations (1)–(4). This means that the particle densities are selected independently, but the potentials and electric fields are then calculated in a self-consistent way with the selected parameters. [ABSTRACT FROM AUTHOR]

Scientific aspects of technologies based on application of non-equilibrium oxygen plasma are presented. Oxygen plasma is sustained by an electrodeless discharge to facilitate a high concentration of neutral reactive species, in particular O atoms. The species interact with solid materials causing surface functionalization, removal or organic impurities, nanostructuring of polymers, selective etching of polymer composites or synthesis of metal-oxide nanoparticles. The flux of O atoms onto the surface-facing plasma is often between 1020 and 1023 m-2 s-1. While the physical interaction with solid materials (i.e. heterogeneous surface recombination) does not depend much on the sample temperature, the chemical interactions (functionalization, etching, oxidation) increase significantly with increasing temperature. The key treatment parameters are therefore the fluence of O atoms onto the sample surface and its temperature. The recommended ranges of parameters for various technologies are shown in the graphical abstract. [ABSTRACT FROM AUTHOR]

Nanometer-sized structures, surfaces and sub-surface phenomena have played an enormous role in science and technological applications and represent a driving-force of current interdisciplinary science. Recent developments include the atomic-scale characterization of nanoparticles, molecular reactions at surfaces, magnetism at the atomic scale, photoelectric characterization of nanostructures as well as two-dimensional solids. Research and development of smart nanostructured materials governed by their surface properties is a rapidly growing field. The main challenge is to develop an accurate and robust electronic structure description. The density of surface-related trap states is analyzed by transient UV photoconductivity and temperature-dependent admittance spectroscopy. An advanced application of thin films on shaped substrates is the deposition of catalytic layers on hollow glass microspheres for hydrogen storage controlled exothermal hydrolytic release. Surface properties of thin films including dissolution and corrosion, fouling resistance, and hydrophilicity/hydrophobicity are explored to improve materials response in biological environments and medicine. Trends in surface biofunctionalization routes based on vacuum techniques, together with advances in surface analysis of biomaterials, are discussed. Pioneering advances in the application of X-ray nanodiffraction of thin film cross-sections for characterizing nanostructure and local strain including in-situ experiments during nanoindentation are described. Precise measurements and control of plasma properties are important for fundamental investigations and the development of next generation plasma-based technologies. Critical control parameters are the flux and energy distribution of incident ions at reactive surfaces; it is also crucial to control the dynamics of electrons initiating non-equilibrium chemical reactions. The most promising approach involves the exploitation of complementary advantages in direct measurements combined with specifically designed numerical simulations. Exciting new developments in vacuum science and technology have focused on forward-looking and next generation standards and sensors that take advantage of photonics based measurements. These measurements are inherently fast, frequency based, easily transferrable to sensors based on photonics and hold promise of being disruptive and transformative. Realization of Pascal, the SI unit for pressure, a cold-atom trap based ultra-high and extreme high vacuum (UHV and XHV) standard, dynamic pressure measurements and a photonic based thermometer are three key examples that are presented. [ABSTRACT FROM AUTHOR]

The factor limiting the application of low-density polyethylene (LDPE) in healthcare is its high susceptibility to bacterial growth. For this reason, we here investigated antibacterial treatments of LDPE foils using appropriate antibacterial agents. Benzalkonium chloride and bronopol were selected because of their satisfactory antibacterial effect, which has been confirmed by their application in the medical and cosmetic industries. The aforementioned substances were immobilized by a multistep approach via the grafting of polyacrylic acid (PAA) brushes onto LDPE surfaces pre-treated with low-temperature plasma. Measurements of the surface energy, peel strength of the adhesive joints, X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy with attenuated total reflectance (FTIR-ATR), and atomic force micro scopy (AFM) were used to investigate the surface and adhesive properties of the antibacterial-treated LDPE. Moreover, the antibacterial effect was determined via measurements of the inhibition zone of the Staphylococcus aureus (S. aureus) bacterial strain. The antibacterial activity of benzalkonium chloride was observed to be more pronounced than that of bronopol. Inhibition- zone measurements of Escherichia coli (E. coli) were also conducted, but an antibacterial effect was not observed. [ABSTRACT FROM AUTHOR]

Recent advances in vacuum sciences and applications are reviewed. Novel optical interferometer cavity devices enable pressure measurements with ppm accuracy. The innovative dynamic vacuum standard allows for pressure measurements with temporal resolution of 2 ms. Vacuum issues in the construction of huge ultra-high vacuum devices worldwide are reviewed. Recent advances in surface science and thin films include new phenomena observed in electron transport near solid surfaces as well as novel results on the properties of carbon nanomaterials. Precise techniques for surface and thin-film characterization have been applied in the conservation technology of cultural heritage objects and recent advances in the characterization of biointerfaces are presented. The combination of various vacuum and atmospheric-pressure techniques enables an insight into the complex phenomena of protein and other biomolecule conformations on solid surfaces. Studying these phenomena at solid–liquid interfaces is regarded as the main issue in the development of alternative techniques for drug delivery, tissue engineering and thus the development of innovative techniques for curing cancer and cardiovascular diseases. A review on recent advances in plasma medicine is presented as well as novel hypotheses on cell apoptosis upon treatment with gaseous plasma. Finally, recent advances in plasma nanoscience are illustrated with several examples and a roadmap for future activities is presented. [ABSTRACT FROM AUTHOR]

In this paper we used the available data for the electron impact scattering cross sections BF3 to calculate the transport coefficients for electrons. Monte Carlo simulation was used to perform calculations of the transport coefficients as well as the rate coefficients in DC electric fields, crossed electric and magnetic DC and RF fields. [ABSTRACT FROM AUTHOR]

Abstract: The removal rate of carbon from amorphous graphite–tungsten composite during cleaning in oxygen plasma was studied. The composite was prepared by sputter deposition from C and WC-targets in Ar atmosphere. A total thickness of deposited layer was about 1μm. The samples were treated in a weakly ionized highly dissociated oxygen plasma created in a microwave discharge at a power of 1kW. The gas flow was 13slh and the pressure was 200Pa. The temperature of the samples during treatment was about 580°C. After plasma treatment the samples were analyzed by AES (Auger electron spectroscopy) depth profiling, XPS (X-ray photoelectron spectroscopy), SEM (Scanning electron microscopy) and AFM (Atomic force microscopy). It was found that during the plasma treatment selective etching of the composite occurred. Carbon was preferentially removed from the composite. XPS results have shown that during the plasma treatment a layer of WO3 was growing on the surface. After about 15min, carbon was completely removed from the deposited composite layer. [Copyright &y& Elsevier]

Abstract: The most important parameter in reactive hydrogen plasma is the density of neutral hydrogen atoms. The density can be measured by different means including a variety of optical emission and absorption spectroscopy methods, titration and catalytic probes. Recently, it was shown that catalytic probes have some advantages over the other methods. The main advantage is the ability for real time measurement of the atom density. A catalytic probe was used to measure the H density in an afterglow of a plasma reactor. Plasma was created in a mixture of argon and hydrogen. At a constant H2 and Ar flow rates, the H density was found to increase with increasing power. At a low concentration of hydrogen in the gas mixture, saturation in the H density was observed. The lower the hydrogen concentration the lower the power at which the saturation was observed. At high hydrogen concentrations, no H saturation was observed. The results were explained with collision phenomena in ionized gases and heterogeneous recombination of H atoms on surfaces. [Copyright &y& Elsevier]

The technology of selective plasma etching was applied in order to study particle distribution in powder coatings. Etching was performed in pure oxygen plasma. Plasma parameters were measured with a double Langmuir probe and a catalytic probe. At the neutral gas temperature of approximately 50 °C, the electron temperature was approximately 60 000 °C, the density of positive ions approximately 1×1016 m-3, and the density of neutral oxygen atoms 2×1021 m-3. In order to prevent sample overheating, plasma was applied in time intervals of 20 s. The removal of the polymer matrix was accomplished within 2–4 min. After plasma treatment, the samples were analyzed with a scanning electron microscope. All the pigment and filler particles were left intact thus enabling the determination of the original distribution of the particles in the coating. [Copyright &y& Elsevier]

In this paper, we report a comparison between the most commonly used single harmonics (sine voltage waveform) and the original multiple harmonics AC-driven atmospheric-pressure plasma jet. The designed multiple harmonics source was applied to a single-electrode plasma jet. In this research, we characterized and studied the advantages of a single-electrode jet which was powered with multiple harmonics voltage waves, fundamental frequency was varied between 5 and 60 kHz. Optical emission spectroscopy, electric probes and plasma jet visible length measurements lead to the conclusion that the optical emission intensity of emitting plasma species correlates with the discharge current RMS (Root Mean Square), whereas the jet visible length correlates with the electrode discharge voltage amplitude. These properties of the plasma jet cannot be obtained with single harmonics AC-driven plasma jets. [ABSTRACT FROM AUTHOR]

Abstract: Amorphous hydrogenated carbon deposits are a present problem in fusion devices with carbon walls. They act as an unpredictable source of hydrogen retention and thus have to be regularly removed. In our experiment we studied removal of hard carbon deposits in an atmosphere of partially dissociated room temperature oxygen. The source of oxygen atoms was a radiofrequency glow discharge in oxygen at pressures in the vicinity of 100Pa. The etching efficiency was observed as surface emissivity variations. Etchings rates are compared to those measured in the discharge region in presence of charged particles. Etching rates in the discharge region are of the order of 1nm/s, etching rates in a neutral oxygen atmosphere were found to be strongly temperature dependent and reached the value of 10nm/s at 300°C. [Copyright &y& Elsevier]