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Calcium fluoride thin films grown on silicon substrates by sublimation under ultra high vacuum are well known to be highly efficient hosts for rare earth luminescence properties. For this reason we incorporate erbium by ion implantation in order to form optoelectronic integrated devices. Here we describe the incorporation conditions of erbium in CaF2/Si structures and their luminescence characteristics. The properties of the material have been investigated for implantation doses varying from 4×1014 to 1×1017 at.cm−2. The role of oxygen in the charge compensation mechanisms is investigated and it is shown that the maximum emission in erbium at 1.53μm occurs for an implanted dose of 2×1016 at.cm−2. This corresponds to an Er concentration three orders of magnitude greater than for the case of classical-erbium-doped semiconductors. At this high concentration (up to 15 at.%) the light emission mechanisms are of great theoretical interest. They involve strong Er-Er coupling effects: energy transfer, cross-relaxation phenomena and high conversion efficiencies.These properties make erbium-implanted CaF2/Si structures excellent candidates for the production of optically active waveguides. The guiding structure can be formed by high energy implantation to build a buried active region of high refractive index within the CaF2 thin film.

An evaluation of the use of intermediate layers for promoting adhesion between diamond and Fe and Ni base alloys is presented. The lack of adhesion between diamond and such alloys has prevented its use as a protective coating in applications at intermediate temperatures. In this study we use a combination of plasma assisted deposition techniques together with controlled bias of the substrate in order to deposit intermediate layers, and simultaneously achieve a thorough intermixing of the elements at the interface, in order to increase the adhesion between the layers. We have compared the performance of different carbide forming metals, as well as other materials. Properties considered in the selection of the appropriate intermediate layers are: chemical affinity with carbon, thermal expansion coefficient, mechanical properties, and adhesion to diamond and to the base metal as well. In the case of multiple layers, adhesion strength was measured after every new layer was deposited, in order to identify any weak links of the composite structure. Transmission electron microscopy was used to determine the microstructure and phases. An analysis is provided of the resulting performance on the basis of the microstructure.

We describe an approach to ion implantation in which the plasma and its electronics are held at ground potential and the ion beam is formed and injected energetically into a space held at high negative potential. The technique allows considerable savings both economically and technologically, rendering feasible ion implantation applications that might otherwise not be possible for many researchers and laboratories. Here, we describe the device and the results of tests demonstrating Nb implantation at 90 keV ion energy and dose about 2 × 1016 cm−2.

We describe work in which gold nanoparticles were formed in diamond-like carbon (DLC), thereby generating a Au-DLC nanocomposite. A high-quality, hydrogen-free DLC thin film was formed by filtered vacuum arc plasma deposition, into which gold nanoparticles were introduced using two different methods. The first method was gold ion implantation into the DLC film at a number of decreasing ion energies, distributing the gold over a controllable depth range within the DLC. The second method was co-deposition of gold and carbon, using two separate vacuum arc plasma guns with suitably interleaved repetitive pulsing. Transmission electron microscope images show that the size of the gold nanoparticles obtained by ion implantation is 3–5 nm. For the Au-DLC composite obtained by co-deposition, there were two different nanoparticle sizes, most about 2 nm with some 6–7 nm. Raman spectroscopy indicates that the implanted sample contains a smaller fraction of sp3 bonding for the DLC, demonstrating that some sp3 bonds ar...

Ion implantation of metal species into insulators provides a tool for the formation of thin, electrically conducting, surface layers with experimenter-controlled resistivity. High energy implantation of Pt and Ti into alumina accelerator components has been successfully employed to control high voltage surface breakdown in a number of cases. In the work described here we have carried out some basic investigations related to the origin of this phenomenon. By comparison of the results of alumina implanted with Ti at 75 keV with the results of prior investigations of polymers implanted with Pt at 49 eV and Au at 67 eV, we describe a physical model of the effect based on percolation theory and estimate the percolation parameters for the Ti-alumina composite. We estimate that the percolation dose threshold is about 4 × 1016 cm−2 and the maximum dose for which the system remains an insulator-conductor composite is about 10 × 1016 cm−2. The saturation electrical conductivity is estimated to be about 50 S/m. We conclude that the observed electrical conductivity properties of Ti-implanted alumina can be satisfactorily described by percolation theory.

In this work, the possibility to increase the surface conductivity of ceramic insulators through their treatment with accelerated metal ion beams produced by a MevvaV.Ru vacuum arc source is demonstrated. The increase in surface conductivity is made possible due to experimental conditions in which an insulated collector is charged by beam ions to a potential many times lower than the accelerating voltage, and hence, than the average beam ion energy. The observed effect of charge neutralization of the accelerated ion beam is presumably associated with electrons knocked out of the electrodes of the accelerating system of the source and of the walls of the vacuum chamber by the accelerated ions.

The retained dose of ions can be increased by Plasma Immersion Ion Implantation and Deposition (PIIID). A substrate is immersed in a metal or carbon plasma and a negative repetitively pulsed bias voltage is applied. During the pulses, an electric sheath is formed around the substrate and ions are accelerated through the sheath and implanted into the substrate. Direct and recoil ion implantation and sputtering take place during the pulses whereas low-energy deposition occurs between the pulses. The condensable plasma can be produced using a cathodic arc plasma source combined with a magnetic macroparticle filter. PIIID can be applied to perform fast high-dose implantations or to deposit thin films with broad intermixing at the film-substrate interface. The bias voltage duty cycle can be tuned to sputter away the film deposited during pulse off-time (similar to the method of sacrificial layer). We have simulated the PIIID process using the Monte Carlo code T-DYN 4.0. This code allows a calculation of the dose-dependent depth profile for a process with deposition and implantation phases, taking sputtering into account. Predicted retained doses and experimentally obtained retained doses measured by Rutherford backscattering spectrometry are compared.

Micron-size macroparticles can be removed from vacuum arc plasmas using magnetic filters, permitting the deposition of high-quality thin films of the cathode material. The principle of magnetic filtering is explained, and ways of improving filter efficiency using additional electric and magnetic fields are explored. Under optimum conditions, about 25% of all ions entering the filter can be used for deposition. Other problems such as down or upscaling of deposition facilities are briefly discussed.

Single crystal samples of (100) oriented yttria stabilized cubic zirconia are implanted with Pt ions to doses up to 6x1017 /cm2. Our previous studies showed that the retained Pt dose was too small due to the sputter limit. To overcome this problem, a C film was deposited on the surface of some samples before implantation. The implanted samples were annealed isothermally in air at 400°-1200°C, and were analysed with RBS-C and TEM. The C-layer has been found to be very effective for protecting the sample surface from sputtering and thus increasing the Pt concentration by a factor of two, up to 33 mol.% Pt. The as-implanted Pt was non-substitutional. After annealing at 1200°C for 1 h, Pt diffused to large depths, and showed a substitutional fraction of about 23%. The detailed TEM measurements on the microstructure and damage of the implanted layer show that after annealing at these temperatures the recovery of ion damage is incomplete. Pt atoms undergo substantial migration concurrently. The Pt at first dissolves in the matrix (though not substitutionally), diffuses and precipitates again at high temperature.

Detailed experimental and theoretical studies of the electroluminescence excitation mechanism of Yb3+ in InP are presented. The electroluminescence spectra and the kinetics of Yb implanted InP were investigated under pulsed and dc excitations at temperatures over the range 9 - 70 K. The electroluminescence spectrum of the 4f transitions 2F5/2 - 2F7/2,, at 9 K, consists of a peak at 1001 nm and broader peaks in the spectral range between 1003 nm and 1010 nm. The intensity and current versus voltage characteristics have been recorded. The emission intensity increased linearly with current and started to saturate at high currents. The plot of the natural logarithm of intensity versus V−1/2 shows a straight line characteristic over three orders of emission intensity, showing that the direct impact excitation mechanism is a dominant process. At low temperature, the rise and decay times of the 1001 nm emission line were 9.63 µs and 10.50 µs, respectively. The thermal quenching energy, EA, was found to be 100 meV for both the electroluminescence intensity and the decay time.

Platinum/polymethylmethacrylate (Pt/PMMA) nanocomposite material was formed by low energy ion implantation of Pt into PMMA, and the transition from insulating to conducting phase was explored. In situ resistivity measurements were performed as the implantation proceeded, and transmission electron microscopy was used for direct visualization of Pt nanoparticles. Numerical simulation was carried out using the TRIDYN computer code to calculate the expected depth profiles of the implanted platinum. The maximum dose for which the Pt/PMMA system remains an insulator/conductor composite was found to be ϕ0 = 1.6 × 1016 cm−2, the percolation dose was 0.5 × 1016 cm−2, and the critical exponent was t = 1.46, indicating that the conductivity is due only to percolation. The results are compared with previously reported results for a Au/PMMA composite.

A vacuum arc ion source provides high current beams of metal ions that have been used both for accelerator injection and for ion implantation, and in both of these applications the degree of space charge neutralization of the beam is important. In accelerator injection application, the beam from the ion source may be accelerated further (post-acceleration), redirected by a bending magnet(s), or focused with magnetic or electrostatic lenses, and knowledge of the beam space charge is needed for optimal design of the optical elements. In ion implantation application, any build-up of positive charge in the insulating targets must be compensated by a simultaneous flux of cold electrons so as to provide overall charge neutrality of the target. We show that in line-of-sight ion implantation using a vacuum arc ion source, the high current ion beam carries along its own background sea of cold electrons, and this copious source of electrons provides a “self-neutralizing” feature to the beam. Here we describe experi...

The photoluminescence (PL) and time resolved spectra of Nd- and Yb-implanted CdS samples are studied under pulsed and CW excitations using Ar+ ion laser for different excitation intensities and temperature (9 - 300 K). The samples were annealed under different conditions using the thermal-pulse method. For CdS:Nd, the PL spectra was recorded in the range 890-930 nm (transitions 4F3/2→4I9/2) and for CdS:Yb it was recorded in the range 985 - 1010 nm (transitions 2F5/2 →2F7/2). The Rise time and decay time were studied for both CdS:Nd and CdS:Yb at different emission lines as a function of temperature and excitation power.

Summary form only given. A very broad beam version of a vacuum arc ion source has been used to carry out high-energy metal ion implantation of a particularly large substrate. A multiple-cathode vacuum arc plasma source was coupled to a 50-cm-diameter beam extractor (multiple aperture, accel-decel configuration) operated at a net extraction voltage of up to 50 kV. The metal ion species chosen were Ni and Ta. The ion source was operated in a repetitively pulsed mode with pulse length 250 /spl mu/s and repetition rate several pulses per second. The extracted beam had a Gaussian profile with FWHM of about 35 cm, giving a nominal beam area of about 100 cm/sup 2/. The current of Ni or Ta metal ions in the beam was up to several amperes. The targets for the ion implantation were a number of 24-inch long, highly polished Cu rails from an electromagnetic rail gun. The rails were located about 80 cm away from the ion source extractor grids, and were moved across a diameter of the vessel in such a way as to maximize the uniformity of the implant along the rail.

The photoluminescence, time resolved spectra and kinetics of Yb implanted InP samples are studied under pulsed and CW excitations (above and below band-gap) at different temperatures and excitation intensity. The photoluminescence intensity and decay time as a function of temperature is explained by a proposed new quenching mechanism involving Fe ion. The rise and decay times depend on excitation intensity. The above experimental facts was explained using the kinetics model developed by H.J. Lozykowski [2]. The numerically simulated luminescence rise and decay times show a good quantitative agreement with experiment, over a wide range of generation rates. The electric field InP:Yb photoluminescence quenching was investigated and reported for the first time.

Adhesion of metal films to carbon-carbon composite materials is a problem when using conventional techniques such as sputter deposition. Metal plasma immersion ion implantation is a novel technique which in combination with metal plasma deposition can produce metal-tocomposite bonding with very good adhesion characteristics. The substrate is immersed in a metal plasma which is produced by a pulsed vacuum arc. When the substrate is biased to high negative voltage the metal ions are accelerated toward and implanted into the substrate. A repetitively pulsed bias (Its pulses) is used to avoid arcing and other deleterious effects. Between high voltage pulses, metal plasma is deposited onto the surface with an energy typical of vacuum arcs, about 50–100 eV. The underlying idea of this mixed implantation-deposition technique is the formation of an extended substrate-film intermixed layer. We have demonstrated the technique for nickel films on carbon-carbon composite materials.

Copper and aluminum used for rail and armature materials in electromagnetic railgun systems undergo severe degradation during the EM gun operation. The extent of this degradation is especially severe in guns operated at high energy levels or designed for repeated firings. In an effort to improve surface properties of the copper rail, armature, and sabot materials, the technique of metal ion implantation using a vacuum arc ion source has been employed. Preliminary tests have been conducted to identify the best implant species to improve spark erosion resistance, scratch resistance and hardness. The implanted species included Al, Ti, Cr, Ni, Ta, Ag, and W. The implantation energy range and dose varied between 100–180 KeV and 0.4 to 2 × 1017 cm-2, respectively . Several analytical techniques were also used to assess the effect of implanted species. These included Rutherford Back Scattering (RBS), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Microhardness Measurements, Spark Erosion and Scratch Testing. It has been tentatively concluded that Ta and Ni implantation of the copper rail substantially improve wear and inhibit arc erosion. There is also sufficient evidence to indicate that implantation of the aluminum armature with Cr and Ta, involving two stages of implantation, will also improve its mechanical and wear properties.

Analysis of fired rails from electromagnetic railgun indicates gross surface melting near the breach end of the rails. This effect is most likely caused by joule heating and arc erosion. To improve the mechanical behavior of the rail material, alloys of copper, such as Cu-0.6 Nb, has been used in the past with moderate success. More recently another alloy of copper, Cu-18 Nb, has become available. Preliminary metallurgical research in the thermomechanical properties of this latter alloy indicates it could be a candidate for application in EM gun systems. In this effort we have attempted to study the influence of ion implantation on the thermomechanical properties of Cu-12Nb alloy. In a series of experiments, Ta ions have been implanted at an energy range of 100–180 KeV and a dose of 5 × 1016 cm-2. Several analytical techniques such as Rutherford Back Scattering (RBS), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), arc erosion, and microhardness measurements have been done. It has been shown that although there is an improvement in the microhardness of the implanted materials, the ion implantation saturation dose cannot exceed 5 × 1016 cm-2. Furthermore, the RBS data indicate that the implanted Ta resides mostly at a depth of about 200–300 Å from the surface. Results from the SEM analysis of unimplanted Cu-12Nb indicate the Nb has an acicular morphology and is randomly distributed. Results from microhardness measurements of the implanted materials indicate that implantation enhances the microhardness. In another experiment, such as implantation of Ta in an already TiN coated surface, we observed a similar increase in the microhardness value. We speculate that the microhardness improvement of Cu-18Nb or the Ta implanted TiN surface is due to induce compressional stresses near the lenticular (filament) Nb fibers in the Cu-18Nb composite.

We describe a novel means for the production of atomically-bonded thin films of a wide range of materials. The technique is a plasma and ion beam method involving synthesis of the desired surface film by plasma deposition and the simultaneous atomic mixing of the film into the substrate by low energy ion implantation from the surrounding plasma. Vacuum-arc-produced metal plasma is used for the metallic component of the film and gases can be added to form compound films. Multiple plasma generators can be used, and films of single metals, alloys, ceramics and multilayers can be formed. By repetitively pulse biasing the substrate during plasma deposition, the growing film is subjected to energetic ion bombardment, and direct and recoil ion implantation is induced. The depositing film is thereby atomically mixed to the substrate as it is formed. The films are atomically smooth, can be anywhere from a few monolayers to microns in thickness, and the interface or mixed transition zone can be tailored. Here we outline the basic plasma physics of the method and describe a number of novel surfaces which have been formed with excellent properties.

Some metal plasma techniques have been developed that provide a convenient means for the doping of semiconductor hosts with rare-earths. These plasma and ion beam tools are based on the application of vacuum arc discharges for the formation of dense rare-earth plasmas which then can be used in a number of ways for doping and otherwise introducing the rare-earths into substrate materials. At the low energy end of the spectrum, the streaming metal plasma can be used for the deposition of thin films, and if more than one plasma source is used then of multilayer structures also. Or by building the vacuum-arc rare-earth plasma generator into an ion source configuration, high current ion beams can be produced for doing high energy ion implantation; alternatively the substrate can be immersed in the streaming rare-earth plasma and by using appropriately phased high voltage substrate pulsing and pulsed plasma generation, plasma immersion ion implantation can be done. Between these two limiting techniques – low energy plasma deposition and high energy ion implantation – a spectrum of hybrid methods can be utilized for rare earth doping. We've made a number of plasma and ion sources of this kind, and we've doped a wide range of substrates with a wide range of rare-earths. For example we've implanted species including Sc, Y, La, Ce, Pr, Nd, Sm, Gd, Dy, Ho, Er and Yb into host materials including Si, GaAs, InP and more. The implantation dose can range from a low of about 1013 cm−2 up to as high as about 1017 cm−2, and the ion energy can be varied from a few tens of eV up to about 200 keV. Here we review these vacuum-arc-based plasma methods for rare-earth doping, describing both the tools and techniques that are available and the applications to which we've put the methods in our laboratory.

The performance and characteristics of a cathodic arc plasma source, 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, are investigated. The high transparency and large area of the mesh allow a high plasma flux to penetrate the anode from the cathodic arc. The mesh helps to decrease the arc resistance and the ignition voltage of the cathodic arc in the focusing magnetic field, and to increase the life of the source, which means that the source makes the cathodic arc easily and greatly stabilized during the operation when a focusing magnetic field exists in the source.

We have investigated the structure of disordered gold-polymer thin films using small angle x-ray scattering and compared the results with the predictions of a theoretical model based on two approaches—a structure form factor approach and the generalized Porod law. The films are formed of polymer-embedded gold nanoclusters and were fabricated by very low energy gold ion implantation into polymethylmethacrylate (PMMA). The composite films span (with dose variation) the transition from electrically insulating to electrically conducting regimes, a range of interest fundamentally and technologically. We find excellent agreement with theory and show that the PMMA-Au films have monodispersive or polydispersive characteristics depending on the implanted ion dose.

We have modeled, fabricated, and characterized superhydrophobic surfaces with a morphology formed of periodic microstructures which are cavities. This surface morphology is the inverse of that generally reported in the literature when the surface is formed of pillars or protrusions, and has the advantage that when immersed in water the confined air inside the cavities tends to expel the invading water. This differs from the case of a surface morphology formed of pillars or protrusions, for which water can penetrate irreversibly among the microstructures, necessitating complete drying of the surface in order to again recover its superhydrophobic character. We have developed a theoretical model that allows calculation of the microcavity dimensions needed to obtain superhydrophobic surfaces composed of patterns of such microcavities, and that provides estimates of the advancing and receding contact angle as a function of microcavity parameters. The model predicts that the cavity aspect ratio (depth-to-diameter ratio) can be much less than unity, indicating that the microcavities do not need to be deep in order to obtain a surface with enhanced superhydrophobic character. Specific microcavity patterns have been fabricated in polydimethylsiloxane and characterized by scanning electron microscopy, atomic force microscopy, and contact angle measurements. The measured advancing and receding contact angles are in good agreement with the predictions of the model.

We have developed a theoretical model for superhydrophobic surfaces that are formed from an extended array of microcavities, and have fabricated specific microcavity patterns to form superhydrophobic surfaces of the kind modeled. The model shows that the cavity aspect ratio can be significantly less than unity, indicating that the microcavities do not need to be deep in order to enhance the superhydrophobic character of the surface. We have fabricated surfaces of this kind and measured advancing contact angle as high as 153°, in agreement with predictions of the model.

We have investigated the fundamental structural properties of conducting thin films formed by implanting gold ions into polymethylmethacrylate (PMMA) polymer at 49 eV using a repetitively pulsed cathodic arc plasma gun. Transmission electron microscopy images of these composites show that the implanted ions form gold clusters of diameter ∼2–12 nm distributed throughout a shallow, buried layer of average thickness 7 nm, and small angle x-ray scattering (SAXS) reveals the structural properties of the PMMA-gold buried layer. The SAXS data have been interpreted using a theoretical model that accounts for peculiarities of disordered systems.

PMMA (polymethylmethacrylate) was ion implanted with gold at very low energy and over a range of different doses using a filtered cathodic arc metal plasma system. A nanometer scale conducting layer was formed, fully buried below the polymer surface at low implantation dose, and evolving to include a gold surface layer as the dose was increased. Depth profiles of the implanted material were calculated using the Dynamic TRIM computer simulation program. The electrical conductivity of the gold-implanted PMMA was measured in situ as a function of dose. Samples formed at a number of different doses were subsequently characterized by Rutherford backscattering spectrometry, and test patterns were formed on the polymer by electron beam lithography. Lithographic patterns were imaged by atomic force microscopy and demonstrated that the contrast properties of the lithography were well maintained in the surface-modified PMMA.

Shallow subsurface layers of gold nanoclusters were formed in polymethylmethacrylate (PMMA) polymer by very low energy (49 eV) gold ion implantation. The ion implantation process was modeled by computer simulation and accurately predicted the layer depth and width. Transmission electron microscopy (TEM) was used to image the buried layer and individual nanoclusters; the layer width was ∼6–8 nm and the cluster diameter was ∼5–6 nm. Surface plasmon resonance (SPR) absorption effects were observed by UV-visible spectroscopy. The TEM and SPR results were related to prior measurements of electrical conductivity of Au-doped PMMA, and excellent consistency was found with a model of electrical conductivity in which either at low implantation dose the individual nanoclusters are separated and do not physically touch each other, or at higher implantation dose the nanoclusters touch each other to form a random resistor network (percolation model).

The MEVVA (metal vapor vacuum arc) ion source provides high current beams of multiply charged metal ions suitable for use in heavy ion synchrotrons as well as for metallurgical ion implantation. Pulsed beam currents of up to several amperes can be produced at ion energies of up to several hundred kiloelectronvolts. Operation has been demonstrated for 48 metallic ion species. The authors review the source performance when used for synchrotron injection. >

We have synthesized single crystal Si1−xGex alloy layers in Si crystals by high dose Ge ion implantation and solid phase epitaxy. The implantation was performed using the metal vapor vacuum arc (Mevva) ion source. Ge ions at mean energies of 70 and 100 keV and with doses ranging from 1×1016 to to 7×1016 ions/cm2 were implanted into Si crystals at room temperature, resulting in the formation of Si1−xGex alloy layers with peak Ge concentrations of 4 to 13 atomic %. Epitaxial regrowth of the amorphous layers was initiated by thermal annealing at temperatures higher than 500°C. The solid phase epitaxy process, the crystal quality, microstructures, interface morphology and defect structures were characterized by ion channeling and transmission electron microscopy. Compositionally graded single crystal Si1−xGex layers with full width at half maximum ∼100nm were formed under a ∼30nm Si layer after annealing at 600°C for 15 min. A high density of defects was found in the layers as well as in the substrate Si just below the original amorphous/crystalline interface. The concentration of these defects was significantly reduced after annealing at 900°C. The kinetics of the regrowth process, the crystalline quality of the alloy layers, the annealing characteristics of the defects, and the strains due to the lattice mismatch between the alloy and the substrate are discussed.

A buried conducting layer of metal/polymer nanocomposite was formed by very low energy gold ion implantation into polymethylmethacrylate. The conducting layer is ∼3 nm deep and of width ∼1 nm. In situ resistivity measurements were performed as the implantation proceeded, and the conductivity thus obtained as a function of buried gold concentration. The measured conductivity obeys the behavior well established for composites in the percolation regime. The critical concentration, below which the polymer remains an insulator, is attained at a dose ∼1.0×1016 atoms/cm2 of implanted gold ions.

The authors describe a novel approach to the measurement of nanofriction, and demonstrate the application of the method by measurement of the coefficient of friction for diamondlike carbon (DLC) on DLC, Si on DLC, and Si on Si surfaces. The technique employs an atomic force microscope in a mode in which the tip moves only in the z (vertical) direction and the sample surface is sloped. As the tip moves vertically on the sloped surface, lateral tip slipping occurs, allowing the cantilever vertical deflection and the frictional (lateral) force to be monitored as a function of tip vertical deflection. The advantage of the approach is that cantilever calibration to obtain its spring constants is not necessary. Using this method, the authors have measured friction coefficients, for load range 0

A series of experiments was carried out in which both a magnetic analyzer (mass separator) and a time-of-flight (TOF) spectrometer were used for ion charge/mass spectral analysis of the ion beam formed by a dc Bernas ion source made for semiconductor implantation. The TOF analyzer was a detachable device that provides rapid analysis of charge-to-mass composition of moderate energy ion beams. The magnetic analyzer was a massive device using a 90 degrees -sector bending magnet with radius of the central orbit of 35 cm. Comparison of these two methods for measuring ion beam composition shows good agreement.

We describe a method for applying metal ions to the near‐surface region of solid materials. The added species can be energetically implanted below the surface or built up as a surface film with an atomically mixed interface with the substrate; the metal ion species can be the same as the substrate species or different from it, and more than one kind of metal species can be applied, either simultaneously or sequentially. Surface structures can be fabricated, including coatings and thin films of single metals, tailored alloys, or metallic multilayers, and they can be implanted or added onto the surface and ion beam mixed. We report two simple demonstrations of the method: implantation of yttrium into a silicon substrate at a mean energy of 70 keV and a dose of 1×1016 atoms/cm2, and the formation of a titanium‐yttrium multilayer structure with ion beam mixing to the substrate.

This report summarizes the research and development that has been carried out at Lawrence Berkeley Laboratory to develop a novel kind of high current metal ion source for metallurgical surface modification application. In ion implantation, an energetic ion beam is injected into a solid surface with the result that the surface composition is changed. For the case when the surface is a metal, the tribological properties of the new metallurgical surface can be significantly improved over the unimplanted surface. Previously, however, very intense metal ion beams have not been available, and this has been an impedance to the development of the field. With the MEVVA (Metal Vapor Vacuum Arc) ion source, metal ion beam currents of very high intensity have become available. In this report we outline the progress made under the funded program in the four areas addressed: development of the MEVVA ion source for ion implantation application; research on the ion beam characteristics and behavior; development of our ion implantation facility; metallurgical ion implantation research that we have carried out.

Studies of amorphous hydrogenated carbon (a-C:H) film deposition revealed that methyl radicals are the precursor species responsible for the bulk mass deposition of the films, while the ions act to improve the mechanical properties. The films were deposited on Si(100) substrates both on the powered (negatively self-biased) and on the grounded electrodes from a methane rf plasma (13.56 MHz) at 68 to 70 mTorr and 300 to 370 K. The films produced on the powered electrode exhibited superior mechanical properties, such as high hardness. A mass spectrometer was used to identify neutral species and positive ions incident on the electrodes from the plasma, and also to measure ion energies. Methyl radicals were incident on the electrode surface with an estimated flux of ${10}^{16}$ ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}2}$ ${\mathrm{s}}^{\mathrm{\ensuremath{-}}1}$, for a rf power of 50 W. Methyl radicals appear to be the dominant intermediates in the growth of the soft carbon polymer, and there is a remarkable decrease in deposition rate due to the introduction of NO, a radical scavenger. A novel pulsed biasing technique was used so that the role of ions in the plasma could be studied separately. It was found that the hardness of the films depends on the power supplied by the ions to the growing film surface (the time averaged difference between the plasma potential and the electrode potential), but not on the energy of individual ions. The pulsed biasing technique offers an efficient method to adjust the film hardness by independent control of the neutral radical and ion fluxes to the surface.

Metallic coatings can be fabricated using the intense plasma generated by the metal vapor vacuum arc. We have made and tested an embodiment of vacuum arc plasma source that operates in a pulsed mode, thereby acquiring precise control over the plasma flux and so also over the deposition rate, and that is in the form of a miniature plasma gun, thereby allowing deposition of metallic thin films to be carried out in confined spaces and also allowing a number of such guns to be clustered together. The plasma is created at the cathode spots on the metallic cathode surface, and is highly ionized and of directed energy a few tens of electron volts. Adhesion of the film to the substrate is thus good. Virtually all of the solid metals of the Periodic Table can be used, including highly refractory metals like tantalum and tungsten. Films, including multilayer thin films, can be fabricated of thickness from Angstroms to microns. We have carried out preliminary experiments using several different versions of miniature, pulsed, metal vapor vacuum arc plasma guns to fabricate metallic thin films and multilayers. Here we describe the plasma guns and their operation in this application, and present examples of some of the thin film structures we have fabricated, including yttrium and platinum films of thicknesses from a few hundred Angstroms up to 1 micron and an yttrium-cobalt multilayer structure of layer thickness about 100 Angstroms.

We describe a nanolithography process for a polymethylmethacrylate (PMMA) surface using scanning contact atomic force microscopy. Parallel furrows were scribed with a pyramidal silicon tip using the same scan mechanism as used to image samples. The PMMA was first electron beam irradiated using a scanning electron microscope and developed. The topography formed is reproducible and predictable. Material from the region where the tip scribes is moved to nearby regions, and aligned, elongated PMMA fragments are seen to decorate the valleys between furrows.

The thickness dependence of the thermoelectric power of Pt films of variable thickness on a reference Au film has been determined for the case when the Pt film thickness, t, is not large compared to the charge carrier mean free path, {ell}, that is, t/{ell}. Pt film thicknesses down to 2.2 nm were investigated. We find that {Delta}S{sub F} = S{sub B}-S{sub F} (where S{sub B} and S{sub F} are the thermopowers of the Pt bulk and film, respectively) does not vary linearly as 1/t as is the case for thin film thermocouples when the film thickness is large compared to the charge carrier mean free path.

We describe the results of investigations of the suitability of the electrostatic plasma lens as a focusing element in the low-energy injection beam lines of particle accelerators. We have explored the focusing of high-current, wide-aperture, heavy-ion beams by a plasma lens. The results indicate that for optimal focusing conditions the lens does not increase the beam emittance nor the beam noise. The ion current density was increased by a factor of 30, up to 250mA∕cm2 in the work described here. We project that with an optimized ion extraction system, the plasma lens can provide an ion-beam current density of up to 400mA∕cm2 or more.

The thermoelectric power SF of thin film thermocouples is related to the bulk thermopower Sbulk by ΔSF(t)=Sbulk−SF as a linear function of 1∕t when t⪢l, where l is the electron mean free path and t the film thickness. For these conditions quantum size effects (QSEs) are negligible. However, when t

We describe a method for treating the surface of stainless steel screws to avoid their cold welding in an ultra high vacuum environment. The method involves exposing the screws to an energetic flux of silver plasma produced by a vacuum arc discharge. We find that plasma deposition of about 100 A or more of silver in this way provides a superior surface.

We describe a simple scratch tester for use in the evaluation of the scratch/adhesion characteristics of material surfaces. Its simple design makes it very inexpensive and easy to assemble and operate. We have used the device for investigating improvements in the hardness of ion implanted copper and in the adhesion of alumina films ion stitched onto a steel substrate.

Objective: To report the successful treatment of Strongyloides stercoralis hyperinfection, which is usually lethal but in this case was diagnosed in its early stages.

We report here on some preliminary investigations of the characteristics of a metal vapor vacuum arc ion source operating in a low voltage mode so as to produce high current beams of metal ions at low energy. The 10‐cm diameter, multiaperture beam formation electrodes were configured to an almost‐symmetric accel–decel potential arrangement, and in this preliminary work the accel voltage was limited to just 4 kV. We produced a pulsed titanium ion beam with current up to 100 mA at 1.5 kV net extractor voltage.

Vacuum arc ion sources have been developed and used in a growing number of laboratories around the world. Beams have been produced from most of the solid metals of the periodic table as well as alloys and mixtures, with ion energy up to several hundred keV and beam current up to several A. Typically the source is repetitively pulsed with a pulse length on the order of a millisecond and duty cycle of 1%, and dc operation has been demonstrated also. The main application has evolved for ion implantation, primarily for metallurgical, ceramic, and polymer surface modification (i.e., nonsemiconductor applications), but also for semiconductor implantation in some special cases; the source is also used for heavy ion injection into particle accelerators. This kind of high-current metal ion source has provided a valuable addition to the spectrum of ion sources available to the experimenter. Here the source fundamentals are briefly reviewed and the source performance and beam characteristics summarized. We survey so...

Erosion rates of metal-vapor vacuum-arc cathode materials have been measured for a number of different cathode elements. The measured rates are compared with the rates predicted by a simple estimate based on the known ion generation rates. The agreement is good for the more refractory metals. For the low boiling-point metals there is evidence for an additional mass loss, as, for example, might be associated with an intense macroparticle generation. >

A model is proposed for the sheath expansion into a nonuniform plasma with substantial drift velocity. We refer in particular to the streaming metal plasma produced by a vacuum arc discharge; this kind of plasma is characterized by its spatial nonuniformity and high ion drift velocity. It is shown that for a nonuniform plasma and high substrate bias voltage (>10 kV), the sheath thickness is significantly smaller than in a uniform plasma. High drift velocity also leads to a decrease in sheath thickness. For plasma immersion ion implantation carried out in a nonuniform plasma, the increase in ion implantation current with increasing voltage is different from that of a uniform plasma where the ion current is constant with voltage. This effect was found to be quantitative agreement with experiment. The decrease in sheath thickness with increasing plasma drift velocity can explain qualitatively the experimentally observed existence of a stable high-voltage sheath for a relatively long time.

Vacuum‐arc‐produced metal plasma can be used as the ion feedstock material in an ion source for doing conventional metal ion implantation, or as the immersing plasma for doing plasma immersion ion implantation. The basic plasma production method is the same in both cases; it is simple and efficient and can be used with a wide range of metals. Vacuum arc ion sources of different kinds have been developed by the authors and others and their suitability as a metal ion implantation tool has been well established. Metal plasma immersion surface processing is an emerging tool whose characteristics and applications are the subject of present research. There are a number of differences between the two techniques, both in the procedures used and in the modified surfaces created. For example, the condensibility of metal plasma results in thin film formation and subsequent energetic implantation is thus done through the deposited layer; in the usual scenario, this recoil implantation and the intermixing it produces ...