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Since the initial reported outbreak of coronavirus disease 2019 (COVID-19), many unique case reports have been published in the medical literature. Here we report a complicated clinical course of a young patient with COVID-19 who presented initially with recurrent autoimmune hemolytic anemia (AIHA). He subsequently developed bilateral pulmonary emboli, and ultimately succumbed to encephalitis and cryptococcemia in the context of being treated with high dose immunosuppression for the AIHA. Combining immunosuppression with active COVID-19 infection presents some truly challenging diagnostic and management scenarios which this case summarizes and highlights very well. Based on this case, we propose some strategies on how to approach these difficult decisions while also recognizing the significant gaps that exist in such an evolving topic. Lastly, this case also represents a potentially novel presentation of secondary fungal infection of the central nervous system (CNS) related to COVID-19.

Nanocomposites formed by metal nanoparticles self-assembled in an insulator matrix are of great technological importance. Applications include surface enhanced Raman spectroscopy based biosensors, optical devices, photovoltaic cells, and more. Self-assembling of nanocomposites using low energy ion implantation offers a fast and low cost process. We report here on our work on nanocomposites formed by very low energy ion implantation of gold and platinum nanoparticles into Poly(methyl methacrylate) (PMMA), with description of the nanoparticle evolution as a function of implantation dose. The Au-PMMA and Pt-PMMA nanocomposites were characterized by transmission electron microscopy, thus determining the nanoparticle density, their size distribution, and the distance between particles as a function of implantation dose. A comparison between Au-PMMA and Pt-PMMA reveals substantial differences in the formation processes of the nanoparticles. The results provide insight into basic nanoparticle formation processes, as well as crucial information important for design applications. In addition, the tunneling decay length ξ and the electron affinity e of the implantation-modified PMMA were obtained using a new and simple approach.

We have explored the suitability and characteristics of interface tailoring as a tool for enhancing the adhesion of hydrogen-free diamond-like carbon (DLC) thin films to silicon substrates. DLC films were deposited on silicon with and without application of an initial high energy carbon ion bombardment phase that formed a broad Si–C interface of gradually changing Si:C composition. The interface depth profile was calculated using the TRIDYN simulation program, revealing a gradient of carbon concentration including a region with the stoichiometry of silicon carbide. DLC films on silicon, with and without interface tailoring, were characterized using Raman spectroscopy, scanning electron microscopy, atomic force microscopy and scratch tests. The Raman spectroscopy results indicated sp3 -type carbon bonding content of up to 80%. Formation of a broadened Si:C interface as formed here significantly enhances the adhesion of DLC films to the underlying silicon substrate.

We have explored the effects of atmospheric environment on Kelvin force microscopy (KFM) measurements of potential difference between different regions of test polycrystalline diamond surfaces. The diamond films were deposited by microwave plasma-assisted chemical vapor deposition, which naturally produces hydrogen terminations on the surface of the films formed. Selected regions were patterned by electron-beam lithography and chemical terminations of oxygen or fluorine were created by exposure to an oxygen or fluorine plasma source. For KFM imaging, the samples were mounted in a hood with a constant flow of helium gas. Successive images were taken over a 5-h period showing the effect of the environment on KFM imaging. We conclude that the helium flow removes water molecules adsorbed on the surface of the samples, resulting in differences in surface potential between adjacent regions. The degree of water removal is different for surfaces with different terminations. The results highlight the importance of taking into account the atmospheric environment when carrying out KFM analysis. © 2012 Wiley Periodicals, Inc.

WOS: 000301521200008, Biodegradable polymers are widely used in biomedical and tissue engineering applications due to their biocompatibility and hydrolysis properties in the body. However, their low surface energy and lack of functional groups to interact with the cellular environment have limited their applications for in vivo studies. Ion beam modification is a convenient method for improving the surface properties of polymeric materials for functional biomedical applications. In the work described here, vacuum arc metal ion implantation was used to modify the composition of the near-surface region of three kinds of polymers-poly(L-lactide), poly(D, L-lactide-co-glycolide), and poly(L-lactide/caprolactone)-chosen as representative of biodegradable polymers. X-ray photoelectron spectroscopy analysis was used to characterize the chemical effects of these polymers after implantation with C and with Au, and the results were compared with untreated control samples. We find that oxidation behavior is brought about for certain implantation fluences, resulting in improved surface hydrophilicity.

The authors present here a summary of their investigations of ultrathin films formed by gold nanoclusters embedded in polymethylmethacrylate polymer. The clusters are formed from the self-organization of subplantated gold ions in the polymer. The source of the low energy ion stream used for the subplantation is a unidirectionally drifting gold plasma created by a magnetically filtered vacuum arc plasma gun. The material properties change according to subplantation dose, including nanocluster sizes and agglomeration state and, consequently also the material electrical behavior and optical activity. They have investigated the composite experimentally and by computer simulation in order to better understand the self-organization and the properties of the material. They present here the results of conductivity measurements and percolation behavior, dynamic TRIM simulations, surface plasmon resonance activity, transmission electron microscopy, small angle x-ray scattering, atomic force microscopy, and scanning...

Objectives: Nano and micro sized textures on surfaces are generally useful biomaterials. Although the importance of roughness degree has been reported for cell morphology, texture morphology can be more determining for cell adhesion and proliferation. Biodegradable polymers are extensively used as scaffolds as well as implant materials in the human body. The aim of this study was to investigate the effect of ion beam bombardment on cell morphology. Methods: Gold and carbon ion implantation was made on biodegradable polymers polyglycolic acid, polycaprolactone and polylactic-co-glycolic-acid. Roughness data were obtained from atomic force microscopy. After surface modification with ion beam, B35 neural cells were evaluated on surfaces for cell compatibility. Morphology and cell surface interaction were analyzed with scanning electron microscopy. Results: We observed improved cell adhesion after ion beam surface modification. Cell adhesion was greater on gold implanted surfaces compared to the carbon implanted. Neural cells attached to lamellar wrinkles, spread by taking the shape of the pattern and exhibited high aspect ratios and axon extension. In contrast, cells that attached on the untreated surfaces remained rounded with low spreading. Conclusion: The findings of this study are important for development of ion beam modified cell cultures and scaffold systems to understand texture-based cell adhesion mechanisms. Keywords: cell culture; ion implantation; polylactic-co-glycolic acid; surface treatment; topography; wettability

We review some novel developments of the electrostatic plasma lens and some new plasma devices based on the plasma-optical idea of magnetic insulation of electrons and equipotentialization along magnetic field lines. The plasma lens configuration of crossed electric and magnetic fields provides an attractive and simple method in establishing a stable plasma discharge at low pressure and has been used to develop some cost-effective low-maintenance plasma devices for ion cleaning, surface activation, and polishing of substrates prior to film deposition. Recent embodiments of these devices use permanent magnets and possess considerable flexibility with respect to spatial configuration.

We describe a concept for spacecraft propulsion by means of an energetic ion beam, with the ion source fixed at the spacecraft starting point (e.g., a lunar-based ion beam generator) and not onboard the vessel. This approach avoids the substantial mass penalty associated with the onboard ion source and power supply hardware, and vastly more energetic ion beam systems can be entertained. We estimate the ion beam parameters required for various scenarios, and consider some of the constraints limiting the concept. We find that the "ion beam sail' approach can be viable and attractive for journey distances not too great, for example within the Earth-Moon system, and could potentially provide support for journeys to the inner planets.

Platinum thin films with thickness in the range of 0.4–12nm were formed by filtered vacuum arc plasma deposition on a substrate with anisotropic roughness. The electrical resistivity was measured in directions parallel and perpendicular to the surface modulation as a function of film thickness, and the resistivity was found to be anisotropic with the degree of anisotropy increasing with decreasing film thickness. The very small thickness of the films calls for a quantum model for film resistivity, and it is shown that the measured resistivity can be interpreted as due to quantum electron scattering by the thin film anisotropic surface roughness.

Made available in DSpace on 2018-12-11T16:41:43Z (GMT). No. of bitstreams: 0 Previous issue date: 2016-06-01 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Chinese Hamster Ovary (CHO) cell cultures were grown on surfaces lithographed with periodic 3D hexagonal microcavity array morphology. The range of microcavity size (inscribed circle diameter) was from 12 μm to 560 μm. CHO cells were grown also on flat surfaces. The characterization was performed with respect to cell growth density (number of nuclei per unit area) by fluorescence optical microscopy and evaluated by correlation function analysis. We found that optimum microcavity radius was 80 μm, concerning to the maximum cell growth density, being even greater than the growth density on a flat (unstructured) substrate of the same material. This finding can be important for optimization of biotechnological processes and devices. Institute of Physics University of São Paulo, C.P. 66318 Pharmacy School UFOP Federal University of Ouro Preto Botucatu Medical School UNESP São Paulo State University Lawrence Berkeley National Laboratory, 1 Cyclotron Road Botucatu Medical School UNESP São Paulo State University CNPq: CNPq-157021/2011-4

The formation of a new phase of composition Mg 54 Al 28 Ag 18 was observed as a result of plasma immersion ion implantation of Ag into the compound Mg 17 Al 12 . The new structure was characterized using a micro-beam diffraction technique. It was found that the implantation-induced phase transition occurs when the retained dose of the implanted ions is within the range of about 10 15 –10 16 ions/cm 2 . The implanted system has been studied theoretically by means of density-functional electronic structure calculations and a new ab initio approach has been developed to evaluate the specific concentrations of the implanted ions that might cause the phase transition effect in the implanted matrix. The theoretically estimated values of concentrations are in good agreement with experimental observations.

The vacuum arc ion source has evolved over the past 20 years into a standard laboratory tool for the production of high current beams of metal ions, and is now used in a number of different embodiments at many laboratories around the world. The primary application of this kind of source has evolved to be ion implantation for material surface modification. Another important use is for injection of high current beams of heavy metal ions into the front ends of particle accelerators, and much excellent work has been carried out in recent years in optimizing the source for reliable accelerator application. The source also provides a valuable tool for the investigation of the fundamental plasma physics of vacuum arc plasma discharges. As the use of the source has grown and diversified, at the same time, the ion source performance and operational characteristics have been improved in a variety of different ways also. Here we review the growth and status of vacuum arc ion sources around the world and summarize some of the applications for which the sources have been used.

We have fabricated diamond microstructures using silicon molds into which microcrystalline diamond was deposited by plasma assisted chemical vapor deposition. Prior to diamond deposition the silicon molds were seeded with the diamond powder of two different grain sizes, 14 and 1μm. Scanning electron microscopy and atomic force microscopy were used to view and characterize the resultant diamond microstructures. Analysis of the diamond replicas indicates better reproduction fidelity for the 14μm diamond powder, and a surface roughness of 20 nm.

Formation of intermetallic compounds within the Mg matrix as a result of implantation of Ag by plasma immersion ion implantation technology was investigated. Transmission electron-microscopy studies of the implanted samples revealed the appearance of nanoparticles of binary phase Mg-Ag. A model based on the classical mechanisms of propagation of accelerated ions through the metal matrix was suggested for the explanation of the experimental observations. Ab initio calculations of the electronic sub-systems proved to be helpful in providing theoretical prediction of the structural changes, which may be induced in the implanted system.

Summary form only given, as follows. There is a need for an alternative to traditional vacuum ion optic systems for the case of high-current beams, particularly for moderate energy (10-100 keV) heavy ion beam manipulation, when space charge forces are large. The axially-symmetric electrostatic plasma lens provides an attractive and unique alternative. Use of a plasma lens in this way was successful demonstrated by a series of experiments. Here we briefly review the plasma lens fundamentals, peculiarities of focusing heavy ion beams, and summarize some recent developments (experiments, computer simulations, theory). We show that there is a very narrow range of low magnetic field for which the optical properties of the lens improve markedly. This opens up possibilities for creation of a new-generation compact lens based on permanent magnets. The first experimental results obtained at Kiev and Berkeley about the operation of a permanent magnet plasma lens for manipulating wide aperture high-current heavy ion beams will be presented and summarized.

The authors describe a method for the measurement of secondary electron emission coefficients and demonstrate the use of this approach for the measurement of secondary electron yields for titanium, copper, and carbon ions incident upon an aluminum target. The method is time-resolved in that a series of measurements can be obtained within a single ion beam pulse of several hundred microseconds duration. The metal ion beams were produced with a vacuum arc ion source, and the ratio of secondary electron current to incident ion current was determined using a Faraday cup with fast control of the electron suppressor voltage. The method is relatively simple and readily applied and is suitable for measurements over a wide parameter range. The secondary yields obtained in the present work are of relevance to the measurement of ion current and implantation dose in plasma immersion ion implantation.

Carbon and titanium plasmas are used to investigate the effects of duct bias on the plasma transport through the magnetic duct of a cathodic-arc plasma source as a function of the magnetic-field strength and arc current so as to determine the optimal duct bias, at which the magnetic duct produces the maximum efficiency for plasma transport. The influence of the guiding magnetic field and arc current on the optimal duct bias is investigated. The optimal duct bias increases with the plasma density for carbon plasma, while the relationship is the opposite for the titanium plasma. The carbon-plasma behavior can be explained by a plasma-diffusion model presented in this paper, since the electron-ion collision frequency /spl nu//sub ei/ is less than the electron-cyclotron frequency /spl nu//sub c,e/. On the other hand, in a titanium plasma, /spl nu//sub ei/ is larger than /spl nu//sub c,e/, so this model is inaccurate. Our result shows that different kinds of plasmas have different transport behavior through the magnetic duct and thus, the duct parameters must be carefully chosen in order to achieve the optimal transport efficiency.

Characteristics of plasmas formed by repetitively-pulsed electrical discharges in sodium chloride and barium chloride saline solutions are reported. Spectroscopic observations in conjunction with an analysis of the voltage and current behavior of the discharge lead to a model in which the liquid is vaporized and ionized to form a plasma containing excited water fragments H* and OH* as well as ions and neutrals from the salt. For typical conditions under which plasma is formed, the plasma density is estimated to be of order 10/sup 12/ cm/sup -3/ and the electron temperature about 4 eV.

The resonance frequency of AFM cantilevers depends on the elastic modulus and on the dimensions of the cantilever. As for coated cantilevers, the resonance frequency will be determined not only by the properties of the cantilever, but also by the properties of the coating (elastic modulus and thickness). We have carried out a systematic investigation of cantilevers coated with several thicknesses of the DLC films. Measurements of the resonance frequency of the cantilevers, before and after the DLC coating, were used with a model to determine the elastic modulus of the DLC. The elastic modulus obtained for the DLC, with this model, was E 2 =616 GPa. The AFM tip radii were also measured after coating and were found to increase with the DLC film thickness.

Optical emission spectroscopy in the range 200-800 nm was applied for investigation of the copper plasma produced by a metal vapour vacuum arc plasma source. The experiments were conducted for the cases when the plasma was guided by straight and Ω-shaped curved solenoids as well as without solenoids, and also for different vacuum conditions. It was found that, besides singly- and doubly-charged ions, a relatively high concentration of excited neutral copper atoms was present in the plasma. The relative fraction of excited atoms was much higher in the region close to the cathode surface than in the plasma column inside the solenoid. The concentration of excited neutral, singly- and doubly-ionized atoms increased proportionally when the arc current was increased to 400 A. Some weak lines were attributed to more highly ionized copper species and impurities in the cathode material.

Mo and S ions were simultaneously implanted into 9Cr18 stainless steel samples. The frictional properties of the implanted samples were assessed using a pin-on-disk tester and the elemental depth profiles were measured by Auger electron spectroscopy. The hardness of the samples was also measured. We find that this dual-element implantation process reduces the coefficient of friction by a factor of 2 and increases the low-friction lifetime by a factor of 4 compared to the 9Cr18 surface with Mo or S implantation alone. This enhancement is related to the synergistic coexistence of the implanted elements at the same place. We have also investigated the process using computer simulation. The simulation results help disclose the characteristics of the modified layer and explain the effects of dual-element ion implantation.

We report on our observation of visible photoluminescence and cathodoluminescence of Pr-implanted GaN. The implanted samples were subjected to isochronal thermal annealing treatments at a temperature of 1100 °C in N 2 at atmospheric pressure to recover from implantation damage and activate the rare earth ions. The sharp characteristic emission lines corresponding to Pr 3+ intra- 4f n -shell transitions are resolved in the spectral range from 400 to 1000 nm and observed over the temperature range from 12 to 335 K. We have developed an energy level diagram for Pr 3+ ions in GaN using recorded spectra. The photoluminescence decay kinetics measurements of 3 P 1 , 3 P 0 , and 1 D 2 levels and quenching mechanism analysis allow us to conclude that the dominant de-excitation process is of electric dipole–electric quadrupole type. We found also that the 1 D 2 level separated from the upper 3 P 0 level by 3755 cm−1 energy gap can be populated in several ways, by direct energy transfer processes, cross relaxation | 3 P 0 , 3 H 4 〉→| 1 D 2 , 3 H 6 〉 and cascade processes from the 3 P 0 or higher levels. The full width at half maximum of the strongest photoluminescence line at 653 nm, the 3 P 0 level, is 2.9 meV at 13 K, with a 1.86 meV blue peak shift in going from 13 to 330 K temperature, while the line at 670 nm, 3 P 1 level, has a full width at half maximum of 4 meV at 13 K and a 1.6 meV red peak shift. The thermal stability of GaN:Pr 3+ epilayers indicates the suitability of this material for visible optoelectronic devices.

We introduce in this article a novel geometry that can be used in the manufacturing of field-emission displays. The geometry proposed combines superior vacuum conductance and a good field-enhancement factor. A theoretical model is developed for the calculation of the upper limit to the electrostatic field at the emitting regions, and these values are compared to those calculated for the actual geometry. The vacuum conductance of the proposed geometry is also calculated, and we show that conductances up to an order of magnitude higher than other schemes are readily achievable. Finally, we present field-emission results obtained from a prototype, and compare them with other emission schemes.

We consider the case of energetic ion beam formation when the ion streaming velocity within the source plasma is substantial, i.e., when the ions have a drift speed (in the positive downstream direction) that is on the order of or greater than the ion acoustic speed in the plasma. Some interesting consequences can follow, including the capability of a negatively biased substrate located in the plasma stream to maintain high bias voltage, and of an ion source with no extractor or “conventionally poor” extractor providing a kind of plasma immersion ion implantation mode of operation. Here we summarize the kind of plasma geometry in which this situation can occur, and describe some experimental observations we’ve made of these effects, with reference to a simple theoretical basis for the mechanism.

Vacuum arc or cathodic arc metal plasma sources are attractive and convenient for depositing high-quality thin metal films and metallurgical coatings. It is a common practice to use a curved magnetic filter duct to eliminate macroparticle contamination and to bias the duct wall with a positive voltage to enhance the throughput of the metal plasma. The metal plasma usually consists of several charge states and time-of-flight (TOF) experiments show that the mean charge state of the metal ions decreases with increasing bias and magnetic field applied to the filter duct. We also derive the throughput of ions with different charge states at different bias voltage and magnetic field by the particle-in-cell (PIC) method. The ion trajectory is simulated neglecting the influence of electron charge. Our results show that the simulated mean charge state displays a similar decreasing trend as the bias voltage and magnetic field strength are increased. Phenomena such as reduction of the mean charge state at high magnetic field strength and bias can be explained in terms of standalone multiply charged metal ions under the influences of magnetic and electric forces inside the filter duct.

We describe some experimental investigations of the manipulation of high-current, large-area beams of heavy metal ions using a high-current electrostatic plasma lens. Beams of carbon, copper, zinc, and tantalum ions (separately) were formed by a repetitively pulsed vacuum arc ion source, with energy in the range about 10-140 keV, beam current up to 0.5 A, initial beam diameter 10 cm, and pulse length 250 ms. The plasma lens was of 10-cm internal diameter and 20-cm length and had nine electrostatic ring electrodes with potential applied to the central electrode of up to 7 kV, in the presence of a pulsed magnetic field of up to 800 Gauss. The current density profile of the focused beam was measured with a radially moveable, magnetically suppressed Faraday cup. The results show that the focal length of the lens and the profile of the transported beam can be controlled by variation of the lens magnetic field and electrode potential distribution. Under optimum operating conditions the ion beam current density at the focus was compressed by a factor of up to 30. We also carried out some preliminary observations of the effect of the plasma lens on the ion charge state distribution of the beam. Here we outline the principles underlying plasma lens operation and summarize the experimental observations we have made of the lens performance in this large-area. high-current regime.

WCCo cutting tool inserts were coated with diamond films using microwave plasma assisted chemical vapor deposition. Several pretreatment processes and combinations were used to enhance the diamond nucleation and growth: mechanical treatments with diamond powder seeding, acid etching of the cobalt using an electrolytic acid bath, and formation of a TiC or DLC interlayer using metal plasma immersion ion implantation and deposition (MePIIID). Scanning electron microscopy (SEM) was used to view the diamond film morphology, and microanalysis was used to examine for cobalt removal after acid etching. The diamond quality was characterized by Raman spectroscopy, and the adhesion between the film and the cutting tool inserts was estimated by indentation tests. The present work compares the different treatments of the WCCo insert surface, with particular reference to the adhesion between the diamond film and the cutting tool insert.

The performance and characteristics of a cathodic arc deposition apparatus consisting of a titanium cathode, an anode with and without a tungsten mesh, and a coil producing a focusing magnetic field between the anode and cathode arc investigated. The arc voltage V/sub a/ is measured with a fixed arc current for an anode diameter of 40 mm. The relationship between V/sub a/ and the magnetic field B with and without a mesh is obtained. In addition, the relationship between the arc current I/sub a/ and V/sub c/, the voltage to which the artificial transmission line was charged, is measured with and without the mesh to determine the minimum ignition voltage for the arc when the anode hole diameter is 40 mm. The arc resistance increases with the focusing magnetic strength B and decreases when using the mesh. Our results indicate that the high transparency and large area of the mesh allows a high plasma flux to penetrate the anode from the cathodic arc. The mesh also stabilizes the cathodic arc and gives better performance when used in concert with a focusing magnetic field.

A hydrodynamic model of free-boundary vacuum arc plasma jet flow through a curved magnetic field has been developed. The plasma flow was modeled by sourceless steady-state equations, and the free boundary of the plasma was determined as a part of the solution of the gas-dynamic equations. It was found that the maximum plasma density shifts with respect to the centerline. The shift is maximum at the 90/spl deg/ guide exit plane and for the case of low magnetic field. The maximum increase in longitudinal plasma velocity along the duct was shown to be a factor of three. The plasma distribution within the duct was analyzed experimentally using a deposition probe technique. The plasma jet expansion predicted by the model was compared with the experiment and a good qualitative agreement was found.

Ion implantation techniques were used to improve the hardness and wear resistance of sputtered hydrogenated amorphous carbon films and cathodic-arc non-hydrogenated amorphous carbon films. Conventional ion implantation and plasma immersion ion implantation and deposition techniques were used to implant the films with Si, Ti, Hf and W ions of mean energies in the ranges of 28–72 and 3–6 keV, respectively, and doses between 1×1015 and 1×1017 cm−2. Nanohardness measurements demonstrated an increase in the apparent film hardness, depending on the type, kinetic energy, and dose of implanted ions. The effect of the ion dose on the microstructure characteristics of implanted carbon films was studied by Raman spectroscopy. Continuous sliding tests and non-contact profilometry revealed an appreciable increase in the wear resistance of the ion implanted films. Differences in the hardness of implanted films are interpreted in terms of microstructural changes caused by competing mechanisms responsible for film densification, irradiation damage and increase of tetrahedral (sp3) bond configurations. It is shown that, under certain conditions, ion implantation post-processing techniques may significantly improve the nanohardness and sliding wear resistance of amorphous carbon films.

In this paper we report the effects of transmission through a 90/spl deg/ solenoidal magnetic filter on the ion charge state distribution of a vacuum arc plasma as a function of the magnetic field strength and the injection distance between the cathode and filter entrance. The mean ion charge state, measured using the time of flight technique, increased compared with the unfiltered value at low magnetic fields and then steadily decreased as the filter field was increased. At high fields, it was significantly lower than the unfiltered value.

The cathodic vacuum are is a simple means of creating a highly ionized metal or carbon plasma, which can be used to produce a wide variety of metal and metal compound thin films. In order to produce smooth, defect-free films suitable for optical and electronic applications, the plasma needs to be filtered of micrometer-sized molten and solid cathode debris known as macroparticles. To date, most of the research effort on plasma filtering has been focused on development and optimization of magnetic filter designs based on curved solenoids. Ryabchikov et al. (1998) proposed and employed novel filter designs for a combined plasma and ion beam source. The new designs are based on a nested set of conical plates in one version and a set of angled plates ("venetian blind") in another. We report on a detailed characterization of the operation of a filter employing a linear venetian blind geometry. The effects of parameters such as plate and arc currents, as well as plate bias on the throughput and deposition profile are reported.

Areal density in magnetic storage is increasing at a blistering pace of 60% annually. Recently IBM announced its mobile product with the industry highest areal density of 2.64 Gb/In{sup 2}. The areal density demonstrations have shown up to 5 Gb/In{sup 2} possible. Reaching higher areal density targets dictate that magnetic spacing between heads and disks be reduced. For the example of a 10 Gb/In{sup 2} areal density goal, the magnetic spacing should be {approx}25 nm. In budgeting this magnetic spacing, it is required that disk and slider air bearing surface overcoats thickness be reduced to 5 nm range. Present choice of carbon overcoat in the magnetic storage hard disk drive industry is sputter deposited, hydrogenated carbon (CH{sub x}) with thickness in the range of 12-15 nm on heads and disks. Novel overcoats such as nitrogenated carbon (CN{sub x}) and cathodic arc carbon films are being developed for future applications. Cathodic arc deposition forms ultra-thin amorphous hard carbon films of high sp{sup 3} content, high hardness, and low coefficient of friction. These properties make it of great interest for head/disk interface application, in particular for contact recording. In many cases, the tribological properties of the head disk interface could be improved by factors up to ten applying cathodic arc overcoats to the slider or disk surface. This paper reviews the results of cathodic arc ultra-thin (2-10 nm) carbon overcoats for head/disk interface tribological applications.

We point out that energetic ion beams can be produced from a plasma-based ion source using a conventional multi-electrode extractor system to form the ion beam, or by using a less conventional approach in which a single grid (wire mesh) is used and the beam is formed across the high voltage sheath formed there. There are requirements on the mesh size with respect to the plasma density (the sheath must be large compared to the mesh dimension) in order for energetic ion beam to be formed. When this condition is not met it is possible for the configuration to behave in a "plasma-immersion mode," and although the system does not then form an energetic ion beam, ion implantation can, under some circumstances, nevertheless be brought about by another coincidental mechanism.

We describe experiments demonstrating the formation of a high current electron beam from a vacuum arc plasma. A preexisting vacuum arc ion source was used, with the extraction voltage reversed in polarity so as to form an electron beam rather than an ion beam; no other changes were required. The beam formed was of energy up to 33 keV, beam current up to 70 A, beam diameter about 10 cm, pulse width 500 /spl mu/s, and energy density up to 25 J/cm/sup 2/. This kind of source can be used for material surface modification.

Ion bombardment of plant and bacterial cellular material has recently been used as a tool for the transfer of exogenous DNA macromolecules into the cell interior region. The precise mechanism that leads to the transfer of macromolecules through the cell envelope is not yet clear, however it has been observed that the ion bombardment is accompanied by the formation of “microcraters” on the cell wall, and it is possible that these features provide channels for the macromolecule transfer. Thus the nature and origin of the microcraters is of importance to understanding the DNA transfer phenomenon as well as being of fundamental interest. We report here on some scanning electron microscope observations we have made of onion skin cells that have been subjected to electron beam bombardment of sufficiently high power density to damage the cell wall. The damage seen is much less than and different from the microcraters formed subsequent to ion bombardment. We speculate that the microcraters may originate from the explosive release of gas generated in the biomaterial by ion bombardment.

Nitrogen fertilizer unabsorbed by crops eventually discharges into the environment through runoff, leaching and volatilization, resulting in three-dimensional (3D) pollution spanning from underground into space. Here we describe an approach for controlling nitrogen loss, developed using loss control fertilizer (LCF) prepared by adding modified natural nanoclay (attapulgite) to traditional fertilizer. In the aqueous phase, LCF self-assembles to form 3D micro/nano networks via hydrogen bonds and other weak interactions, obtaining a higher nitrogen spatial scale so that it is retained by a soil filtering layer. Thus nitrogen loss is reduced and sufficient nutrition for crops is supplied, while the pollution risk of the fertilizer is substantially lowered. As such, self-fabrication of nano-material was used to manipulate the nitrogen spatial scale, which provides a novel and promising approach for the research and control of the migration of other micro-scaled pollutants in environmental medium.

We describe an approach to ion implantation in which the plasma and its electronics are held at ground potential and the ion beam is injected into a space held at high negative potential, allowing considerable savings both economically and technologically. We used an "inverted ion implanter" of this kind to carry out implantation of gold into alumina, with Au ion energy 40 keV and dose (3-9) × 10(16) cm(-2). Resistivity was measured in situ as a function of dose and compared with predictions of a model based on percolation theory, in which electron transport in the composite is explained by conduction through a random resistor network formed by Au nanoparticles. Excellent agreement is found between the experimental results and the theory.

The vacuum arc ion source has evolved into a more or less standard laboratory tool for the production of high-current beams of metal ions, and is now used in a number of different embodiments at many laboratories around the world. Applications include primarily ion implantation for material surface modification research, and good performance has been obtained for the injection of high-current beams of heavy-metal ions, in particular uranium, into particle accelerators. As the use of the source has grown, so also have the operational characteristics been improved in a variety of different ways. Here we review the principles, design, and performance of vacuum arc ion sources., Comment: 19 pages, contribution to the CAS-CERN Accelerator School: Ion Sources, Senec, Slovakia, 29 May - 8 June 2012, edited by R. Bailey, CERN-2013-007

Amorphous hard carbon films of varying sp{sup 2}/sp{sup 3} fractions have been deposited on Si using filtered cathodic are deposition with pulsed biasing. The films were heat treated in air up to 550 C. Raman investigation and nanoindentation were performed to study the modification of the films caused by the heat treatment. It was found that films containing a high sp{sup 3} fraction sustain their hardness for temperatures at least up to 400 C, their structure for temperatures up to 500 C, and show a low thickness loss during heat treatment. Films containing at low sp{sup 3} fraction graphitize during the heat treatment, show changes in structure and hardness, and a considerable thickness loss.

The production of energetic metal ion beams by vacuum arc ion sources is a subfield of ion beam science and technology that has experienced rapid growth and a great deal of research activity in the last decade or so. Interest in this kind of ion source derives from the high current of metal ions that can be produced-these are the defining and key properties of the source, and they open up areas of application that have not previously been readily accessible. We present a concise history of this field of activity. The background, history, and recent research and development are discussed.

The plasma-generating parts of ion sources including their power supplies are usually floated to high potential (ion extraction voltage), thus requiring great insulation efforts and causing high costs for high-energy ion beams. A new concept for pulsed ion sources is presented in which a single power supply is used to simultaneously produce the plasma and high extractor voltage via a modified Marx generator. Proof-of-principle experiments have been performed with high-current spark discharges in vacuum where multiply charged ions are produced with this Marx-generator-based ion source ("Magis"). Using "Magis", it has been demonstrated that pulsed ion beams of very high energies can be obtained with relatively low voltage. For copper, ions of charge states up to 7+ have been found whose energy was 112 keV for a charging voltage of only 10 kV.

Whereas energetic ion beams are conventionally produced by extracting ions (say, positive ions) from a plasma that is held at high (positive) potential, with ion energy determined by the potential drop through which the ions fall in the beam formation electrode system, in the device described here the plasma and its electronics are held at ground potential and the ion beam is formed and injected energetically into a space maintained at high (negative) potential. We refer to this configuration as an “inverted ion source.” This approach allows considerable savings both technologically and economically, rendering feasible some ion beam applications, in particular small-scale ion implantation, that might otherwise not be possible for many researchers and laboratories. We have developed a device of this kind utilizing a metal vapor vacuum arc plasma source, and explored its operation and beam characteristics over a range of parameter variation. The downstream beam current has been measured as a function of extraction voltage (5–35 kV), arc current (50–230 A), metal ion species (Ti, Nb, Au), and extractor grid spacing and beamlet aperture size (3, 4, and 5 mm). The downstream ion beam current as measured by a magnetically-suppressed Faraday cup was up to as high as 600 mA, and with parametric variation quite similar to that found for the more conventional metal vapor vacuum arc ion source.

Microwave plasma assisted chemical vapour deposition was used to produce silicon nitride films on silicon substrates from mixtures of methane and nitrogen. Deposition temperatures varied from 800 to 1000°C and pressure varied from 53.2 to 79.8×102Pa. Gas mixtures with low methane content resulted in no reaction. Gas mixtures with high methane content produced an amorphous carbon film on the silicon wafer surface. At intermediate methane contents, the process produces a mixture of α and β silicon nitride. A mechanism is proposed according to which the silicon surface is chemically etched by the activated methyl radicals forming Si(CH3)4, which then reacts with nitrogen atoms (or ions) to form the silicon nitride. The morphology of the individual crystals evolves from platelets to needle-like depending on the deposition conditions, and on the surface coverage of the silicon surface.

Nickel hydroxide is the electrochemically active material in the positive electrode of several important rechargeable alkaline-electrolyte batteries. It is believed that divalent Ni(OH){sub 2} is converted to trivalent NiOOH as the electrode is electrochemically oxidized during the battery charging process, and the reverse reaction (electrochemical reduction) occurs during battery discharge, however the details of this process are not completely understood. Because these electrochemical reactions involve surface charge-transfer processes, it is anticipated that surface modification may result in improved battery performance. We used broad-beam metal ion implantation and Metal Plasma Immersion Ion Implantation and Deposition to add cobalt and other species to the nickel electrode surface. The principle of the latter technique is explained in detail. It is shown that implanted and deposited cobalt ions act as a dopant of Ni(OH){sub 2}, and thereby alter its electronic conductivity. This electronic effect promotes lateral growth of NiOOH nodules and more-complete conversion of Ni(OH){sub 2} to NiOOH, which can be interpreted in terms of the nodule growth model. Other dopants such as Au, W, Pb, Ta and Ti{sub 4}O{sub 7} were also tested for suppressing the parasitic oxygen evolution reaction in rechargeable nickel cells.

A three-step process for enhancing the nucleation density of diamond on unscratched silicon substrates using microwave-plasma-enhanced chemical vapor deposition is described. Hard diamond-like carbon (dlc) films with thickness in the range 5–100 nm were first formed on smooth (100) silicon surfaces using a vacuum-arc plasma deposition technique at room temperature. The dlc-coated silicon substrates were subsequently subjected to a low-temperature pretreatment with a methane-rich plasma for an hour before switching to the diamond nucleation conditions. To investigate the effect of the dlc film structure on diamond nucleation, experiments with silicon substrates coated with evaporated carbon films approximately 50–100 nm thick were also performed under similar pretreatment and diamond nucleation conditions. Diamond films with nucleation density about 2 × 108 cm−2 were obtained with pretreated dlc films, depending on the film thickness and the pretreatment time, whereas in the absence of the pretreatment and/or with evaporated carbon films the diamond nucleation density was less than 104 cm−2. The significant enhancement in diamond nucleation density obtained with pretreated dlc films is attributed to the inherently high etching resistance of the films resulting from the high fraction of sp3 bonds. The actual nucleation sites might be very fine carbon or, possibly, SiC particles produced by etching back the dlc film.

We have investigated the charge state distributions of metal ions produced in a high current vacuum arc plasma located in a strong magnetic field. The arc current was varied over the range 200 A to 4 kA and the magnetic field was from zero up to 10 kG. In general, the effect of both high arc current and high magnetic field is to push the distribution to higher charge states-the mean ion charge state is increased and new high charge states are formed. These effects are explained in terms of increased power input (higher plasma temperature) and delayed freezing of the charge state distribution during the plasma expansion process.

The plasma distribution using a cathodic arc plasma source with and without magnetic macroparticle filter has been determined by depositing on a transparent plastic substrate and measuring the film absorption. It was found that the width of the distribution depends on the arc current, and it also depends on the cathode material which leads to a spatial separation of the elements when an alloy cathode is used. By applying a magnetic multicusp field near the exit of the magnetic filter, it was possible to modify the plasma distribution and obtain a flat plasma profile with a constant and homogeneous elemental distribution which was demonstrated by depositing FeNd thin films.