Cathodic Arc Source Research Articles

Enhancing the hardness of Al/W nanostructured coatings

Two-component multilayer thin films frequently show hardness enhancements atspecific repeat periods above that of the constituent layers. This study of hardnessenhancements in W/Al nanostructured coatings provides strong new evidence thathardness enhancements in this system arise not only from the presence of a layeredstructure, but also from the presence of defects introduced by changing the depositionconditions. Samples with well defined layers of W and Al were produced by sputteringto cover a wide range of periods from 10 to 200 nm. No evidence of enhancedhardness in these films was found by nanoindentation. On the other hand, samplesdeposited from cathodic arc sources showed strong hardness enhancement above thatof pure W. However, the samples of highest hardness did not contain Al layersfor much of their thickness. The hardening mechanism therefore could not beattributed to the presence of a multilayer structure. Examination of the microstructureshowed that the interruptions to the W deposition caused by operation of theAl source introduced defects which acted as pinning sites for dislocations. Thenanoindentation hardness data were well described using a modified Hall–Petch relation.

A flexible curvilinear electromagnetic filter for direct current cathodic arc source

Widespread applications of direct current (dc) cathodic arc deposition are hampered by macroparticle (MP) contamination, although a cathodic arc offers many unique merits such as high ionization rate, high deposition rate, etc. In this work, a flexible curvilinear electromagnetic filter is described to eliminate MPs from a dc cathodic arc source. The filter which has a relatively large size with a minor radius of about 85 mm is suitable for large cathodes. The filter is open and so the MPs do not rebound inside the filter. The flexible design allows the ions to be transported from the cathode to the sample surface optimally. Our measurements with a saturated ion current probe show that the efficiency of this flexible filter reaches about 2.0% (aluminum cathode) when the filter current is about 250 A. The MP density measured from TiN films deposited using this filter is two to three orders of magnitude less than that from films deposited with a 90 degrees duct magnetic filter and three to four orders of magnitude smaller than those deposited without a filter. Furthermore, our experiments reveal that the potential of the filter coil and the magnetic field on the surface of the cathode are two important factors affecting the efficacy of the filter. Different biasing potentials can enhance the efficiency to up to 12-fold, and a magnetic field at about 4.0 mT can improve it by a factor of 2 compared to 5.4 mT.

Fabrication of highly (1000) oriented textured zinc oxide films by metal cathodic arc and oxygen dual plasma deposition and their optical properties

Highly (1000) oriented ZnO films were successfully grown onto silicon substrates using a dual plasma deposition process incorporating a metal cathodic arc source and oxygen ambient. The optical properties of a series of ZnO films deposited on quartz using similar conditions were investigated using UV–visible spectrophotometry, and the effects on the band gap were investigated. The absorption of C-excitons resulting in a blue-shift of the band gap at room temperature is accentuated due to strong absorption at higher energy for light polarized ( E // c) in the highly (1000) oriented ZnO film.

Deposition of nanocomposite thin films by a hybrid cathodic arc and chemical vapour technique

A hybrid technique is described for the synthesis of nanocomposite Ti–Si–N thin films based on the reactive deposition of Ti produced from a cathodic arc source and silicon from a liquid tetramethylsilane (TMS), precursor. The influence of the TMS flow rate on the structure and mechanical properties has been investigated. The film structure was found to comprise TiN crystallites and amorphous Si 3N 4. The X-ray diffraction data showed that with increasing TMS flow there is a decrease in the TiN crystalline size from 33 nm to 4 nm. The hardness of the films was found to be strongly dependent on the Si content and reached a maximum value of 41 GPa at ∼ 5% Si content at a total pressure of nitrogen and TMS of 0.8 Pa. Hardness enhancement was found to arise from the nanostructural change induced due to the addition of an amorphous Si 3N 4 phase into the film. Transmission electron microscopy (TEM) analysis confirmed the structure of the Ti–Si–N composites.

Hall stratum filtered cathodic arc source for carbon plasma

A novel filtered cathodic vacuum arc source of carbon plasma, in which plasma ions are reflected from a Hall stratum formed in the inter-electrode gap, was studied. The plasma source consisted of a rectangular carbon cathode, positioned between the poles of a permanent magnet, a copper anode, and a triggering mechanism. An arc was operated with current pulses having a duration of 7 ms and a peak current of 200 A. It was shown that the cathode spot plasma jets were reflected from the Hall stratum formed in the arched magnetic field, and bent through 180° towards substrates positioned alongside of the cathode, while macroparticles flew from the cathode spots in straight trajectories. The calculated thickness of the Hall stratum ranged from less than 1 mm to ≥ 10 mm. The ratio of the substrate ion current to the arc current was ∼ 7.5%, which is much larger than that of most known filtered systems, and approaches the plasma transfer efficiency of unfiltered vacuum arc plasma sources.

Biocompatible Silver-containing a-C:H and a-C coatings: A Comparative Study

ABSTRACTHydrogenated diamond-like-carbon (a-C:H) and hydrogen-free amorphous carbon (a-C) coatings are known to be biocompatible and have good chemical inertness. For this reason, both of these materials are strong candidates to be used as a matrix that embeds metallic elements with antimicrobial effect. In this comparative study, we have incorporated silver into standard diamond-like carbon (DLC) coatings by plasma ion implantation and deposition (PIII&D) using methane (CH4) plasma and simultaneously depositing Ag from a pulsed cathodic arc source. In addition, we have grown amorphous carbon – silver composite coatings using a dual-cathode pulsed filtered cathodic-arc (FCA) source. The silver atomic content of the deposited samples was analyzed using glow discharge optical spectroscopy (GDOES). In both cases, the arc pulse frequency of the silver cathode was adjusted in order to obtain samples with approximately 5 at.% of Ag. Surface hardness of the deposited films was analyzed using the nanoindentation technique. Cell viability for both a-C:H/Ag and a-C:/Ag samples deposited on 24-well tissue culture plates has been evaluated.

TiN Coating on Magnesium Alloy by Arc-Aided Glow Discharge Plasma Penetrating Technique

Arc-aided glow discharge plasma penetrating technique is a new surface coating method. With the help of vacuum arc discharge, a cold cathode arc source continually emits ion beams of coating elements with high currency density and high ionizing ratio. As the ion bombard working on, nitrogen is let in the chamber simultaneously. Then the surface of the parts formed ceramic coatings. Under lab condition, a commercial magnesium alloy Az91 had been coated with TiN film layer with the aim of improving the corrosion resistance. This paper mainly summarizes the testing and analyzing of the coating layer. The composition and microstructure of the coating layer had been analyzed by means of X-ray diffraction (XRD) and glow discharge spectrum (GDS), and the surface appearance had been surveyed by scanning electronic microscope (SEM). The adhesion strength between film and matrix had been evaluated by experiments of sticking-tearing. The results indicated that the coated layer on magnesium alloy were homogeneous, dense and robustly adherent.

Deposition of nanocomposite TiN-Si3N4 thin films by hybrid cathodic arc and chemical vapor process

A hybrid technique is described for the synthesis of nanocomposite TiNSi3N4 thin films based on the reactive deposition of Ti produced from a cathodic arc source and Si from a liquid tetramethylsilane (TMS), precursor. The technique combines both the physical vapour of Ti and chemical vapour of silicon in a nitrogen background pressure in a single system. The influence of the TMS flow rate on the structure and mechanical properties has been investigated. The film structure was found to comprise of TiN crystallites and amorphous Si3N4. The X-ray diffraction data showed that with increasing TMS flow, there is a decrease in the TiN crystalline size from 33 nm to 4 nm. The hardness of the films was found to be strongly dependent on the Si content and reached a maximum value of 41 GPa at ∼5% Si content at a total pressure of nitrogen and TMS of 0.8 Pa. Hardness enhancement was found to arise from the nanostructural change induced due to the addition of an amorphous Si3N4 phase into the film. Transmission electron microscopy (TEM) analysis confirmed the structure of the ncTiN/aSi3N4 composites. Films with 4 at. % or more silicon were found to maintain the hardness after annealing at 500 °C in vacuum.

Carbon ion implantation of ultra-high molecular weight polyethylene using filtered cathodic vacuum arc with substrate pulse biasing

This paper discusses the results of an investigation that has been carried out to improve the nano-hardness and tribological properties of ultra-high molecular weight polyethylene (UHMWPE) using a filtered cathodic arc source with substrate pulse biasing. The filtered cathodic arc source generated highly ionized carbon plasma and ions were accelerated towards the substrate by the negative substrate pulse voltage. Graphitization, nano-hardness and wear rate of the modified surfaces were systematically studied as a function of pulse voltage (from − 3 kV to − 12 kV) and implantation time (from 1 min to 20 min). Graphitization of the modified surfaces was observed using Raman and X-ray photoelectron spectroscopes. The scanning electron microscopy images revealed heavy structural damage to the surface of the UHMWPE at increasing pulse voltages. The nano-hardness of the UHMWPE surface, measured at an applied load of 100 μN, was increased from 0.35 GPa to 1.6 GPa when implanted with carbon at a pulse voltage of − 10 kV for an implantation time of 12 min (ion dose about 1.73 × 10 17 atoms/cm 2). The wear test was carried out using a pin on disk tribometer with an applied load of 1 N for 1000 cycles, and showed a reduction in wear rate from 67.5 × 10 − 5 mm 3/Nm to 16.5 × 10 − 5 mm 3/Nm when a virgin UHMWPE was compared to a sample implanted with carbon at − 5 kV for 10 min. The mechanisms underlying the improved surface properties of the carbon-implanted UHMWPE were discussed.

Plasma-ion beam source enhanced deposition system

An advanced deposition system, plasma-ion beam source enhanced deposition system, is introduced. This equipment is composed of metal ion implantation source, gas ion implantation source, magnetron sputtering source, planar plasma source, hot filament plasma source and magnetic filtered cathode arc source. The metal implantation source and the gas implantation source are working with cathode arc and magnetron sputtering simultaneously. Many kinds of duplex technologies of plasma enhanced deposition can be realized in this system. The characteristics of plasma sources are described. Some duplex hard coatings are prepared, such as metal-doped diamond-like carbon (DLC) films, nitriding-TiN films and hard coatings on bearing steel at low temperature. The performances of these films were studied. The results show that the processes can be widely used in industry.

Surface composition and surface energy of Teflon treated by metal plasma immersion ion implantation

Plasma immersion ion implantation using a metal vacuum vapor arc (MEVVA) or cathodic arc source was used to modify the fluorine-based polymer, Teflon. Several transition metal ions such as Co, Ni, Cu were introduced into plasma and implanted into the Teflon surface. The chemical composition of the modified surface was determined by Rutherford backscattering spectrometry (RBS) and X-ray photoelectron spectroscopy (XPS). The metals were found to be distributed several nanometers from the surface and XPS results showed the formation of metallic carbides and fluorides on the surface. Contact angle measurement results demonstrate the favorable change in the wettability from being hydrophobic to hydrophilic. Our study shows that the increase of the surface energy is due to the change of the surface interaction properties after metal plasma implantation.

Asymmetric injection of cathodic arc plasma into a macroparticle filter

The cathodic arc plasmas produced by cathode spots usually include macroparticles, which is undesirable for many applications. A common way of removing macroparticles is to use curved solenoid filters that guide the plasma from the source to the substrate. In this work, an arc source with a relatively small cathode is used, limiting the possible locations of plasma production. The relative position of cathodic arc source and macroparticle filter was systematically varied and the filtered plasma current was recorded. It was found that axis-symmetric plasma injection lead to maximum throughput only if an anode aperture was used, which limited the plasma to near-axis flow by scraping off plasma at larger angles to the axis. When the anode aperture was removed, more plasma could enter the filter. In this case, maximum filtered ion current was achieved when the plasma was injected off-axis; namely, offset in the direction where the filter is curved. Such behavior was anticipated because the plasma column in the filter is known to be shifted by E×B and centrifugal drift as well as by non-axis-symmetric components of the magnetic field in the filter entrance and exit plane. The data have implications for plasma transport variations caused by different spot locations on cathodes that are not small compared to the filter cross section.

Carburising of steel AISI 1010 by using a cathode arc plasma process

The properties and processes of cathode arc plasma carburizing were studied in this paper. Graphite with high purity and high strength was selected as the cathode arc source to provide carbon atoms. The carbon steel AISI 1010 was used as the substrate. A surface concentration of 1.05 wt.%C and a carburised layer thickness of 780 μm was obtained at 950 °C in 30 min. The diffusion coefficient of carbon atoms in carburizing layer was estimated by using the Matano-Plane method. The exponential relationship of diffusion coefficient and the distance to surface are determined.

Results on intense beam focusing and neutralization from the neutralized beam experiment

Experimental techniques to provide active neutralization for space-charge-dominated beams as well as to prevent uncontrolled ion beam neutralization by stray electrons have been demonstrated. Neutralization is provided by a localized plasma injected from a cathode arc source. Unwanted secondary electrons produced at the wall by halo particle impact are suppressed using a radial mesh liner that is positively biased inside a beam drift tube. Measurements of current transmission, beam spot size as a function of axial position, beam energy, and plasma source conditions are presented along with detailed comparisons with theory.

Effect of Ion Mass and Charge State on Transport of Vacuum Arc Plasmas Through a Biased Magnetic Filter

The effect of ion mass and charge state on plasma transport through a 90/spl deg/-curved magnetic filter is experimentally investigated using a pulsed cathodic arc source. Graphite, copper, and tungsten were selected as test materials. The filter was a bent copper coil biased via the voltage drop across a low-ohm, "self-bias" resistor. Ion transport is accomplished via a guiding electric field, whose potential forms a "trough" shaped by the magnetic guiding field of the filter coil. Evaluation was done by measuring the filtered ion current and determination of the particle system coefficient, which can be defined as the ratio of filtered ion current, divided by the mean ion charge state, to the arc current. It was found that the ion current and particle system coefficient decreased as the mass-to-charge ratio of ions increased. This result can be qualitatively interpreted by a very simple model of ion transport that is based on compensation of the centrifugal force by the electric force associated with the guiding potential trough.

Synthesis of aluminum nitride films by plasma immersion ion implantation–deposition using hybrid gas–metal cathodic arc gun

Aluminum nitride (AlN) is of interest in the industry because of its excellent electronic, optical, acoustic, thermal, and mechanical properties. In this work, aluminum nitride films are deposited on silicon wafers (100) by metal plasma immersion ion implantation and deposition (PIIID) using a modified hybrid gas–metal cathodic arc plasma source and with no intentional heating to the substrate. The mixed metal and gaseous plasma is generated by feeding the gas into the arc discharge region. The deposition rate is found to mainly depend on the Al ion flux from the cathodic arc source and is only slightly affected by the N2 flow rate. The AlN films fabricated by this method exhibit a cubic crystalline microstructure with stable and low internal stress. The surface of the AlN films is quite smooth with the surface roughness on the order of 1/2 nm as determined by atomic force microscopy, homogeneous, and continuous, and the dense granular microstructures give rise to good adhesion with the substrate. The N to Al ratio increases with the bias voltage applied to the substrates. A fairly large amount of O originating from the residual vacuum is found in the samples with low N:Al ratios, but a high bias reduces the oxygen concentration. The compositions, microstructures and crystal states of the deposited films are quite stable and remain unchanged after annealing at 800 °C for 1 h. Our hybrid gas–metal source cathodic arc source delivers better AlN thin films than conventional PIIID employing dual plasmas.

Preparation of TiN film on the inner surface of a pipe by plasma-based ion implantation and deposition

Titanium nitride (TiN) films were prepared on the inner surface of a pipe with a diameter of 80 mm and a length of 150 mm using plasma-based ion implantation and deposition (PBII-D). A titanium cathodic arc discharge was generated at a nitrogen pressure of 8 Pa. Gold-colored TiN films were prepared. The film thickness decreases with increasing the distance from the cathodic arc source due to the spatial distribution of the plasma species. A grounded rod, which is placed in the center of the pipe, does not largely influence the film thickness, but enhances the microhardness of the prepared film. The center rod also makes the PBII-D process stable for applying a pulse voltage.

Effects of N ion energy on titanium nitride films deposited by ion assisted filtered cathodic vacuum arc

Titanium nitride (TiN) films were synthesized at ambient temperature on (1 0 0) silicon substrates by a filtered vacuum cathodic arc source and simultaneous bombardment from nitrogen ion beam. The effects of N ion energy on the film morphology, composition, microstructure, resistivity and mechanical properties were systematically investigated. With increasing N ion energy, the film was initially composed of many small spiky grains separated by deep boundaries, and then of many domed grains isolated by shallow boundaries, and finally of far smaller and much more spiky grains with the deepest boundaries. The chemical composition did not vary much with the ion energy. Increasing N ion energy also resulted in the change of the film phase composition and texture, where the competition between the strain energy and the stopping energy determined the film orientation. As the ion energy increased, the film resistivity increased while the film hardness decreased. The films possessed adhesion property independent of N ion energy and superior to that of the films deposited by magnetron sputtering. Some explanation will be given in detail.

Properties of Ti1−xSixNy films deposited by concurrent cathodic arc evaporation and magnetron sputtering

A new technique is described in the synthesis of thin films of Ti1−xSixNy based on the concurrent reactive deposition of Ti produced by a cathodic arc source and Si produced by a d.c. magnetron sputter source. The technique permits the controllable doping of TiN with silicon over the range of 1–16 at.%. The films were found to have a microhardness of 70 GPa with a compressive stress of 5.5 GPa when deposited with a magnetron power of 220 W and a bias voltage of −150 V, and a maximum hardness of 58 GPa and stress values of approximately 3.3 GPa when deposited using 280 W magnetron power and −50 V bias. The hardness and stress of TiN was found to be 26 and 3.5 GPa, respectively, when deposited in the absence of the magnetron.

Effects of plasma ion implantation from cathodic arc plasmas

Plasma ion implantations from cathodic arc plasmas of the Ti–Si–N and Ti–B–N systems are performed into hardened high speed steel with pulsed bias voltages of −5 to −20 kV at working gas pressures of 10 −2 and 4×10 −3 mbar as well as at substrate temperatures of 200 and 300°C. The samples are characterized by tribological investigations. Coatings deposited with substantially shuttered direct particle impact from the cathodic arc source show the highest wear resistance.