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The effect of oxygen and argon partial pressures (PO2, PAr) in a Zr vacuum arc on plasma ion current density Jp, arc voltage Varc, deposition rate vd, and selected coating properties was determined. A d.c. arc current of Iarc = 100 A was initiated between a Zr cathode and a grounded anode. Cathode spots produced a plasma jet, which entered a 1/8 torus macroparticle (MP) filter. The plasma was guided by a d.c. magnetic field through an aperture to a glass substrate or a flat disk probe, mounted on a rotatable holder. Jp was measured with the probe, negatively biased to Vb = − 60 V. Coating thickness was measured using a profilometer, and coating properties were investigated using optical microscopy, energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), nano-indentation and optical analysis. The discharge electrical characteristics and the coating deposition rate were found to be significantly influenced by PO2 and PAr. Jp and vd increased with PAr until a maximum at PAr = 0.27 Pa and decreased with PO2. Varc decreased with both PAr and PO2. The changes in Jp, Varc, and vd, with PAr were larger at larger PO2. The Jp, Varc, and vd dependencies suggest that addition of Argon increased the Zr ion emission from the cathode, possibly because Ar ion bombardment reduced Zr surface oxidation and improved plasma conductivity. Zirconium Oxide (ZrO2) coatings were transparent and had colored interference rings. Well adhered, MP-free ZrO2 coatings were deposited with PO2 ≥ 1.07 Pa. Coatings deposited with PO2 = 1.07 Pa + PAr = 0 were amorphous, whereas those deposited with PO2 = 1.07 Pa + PAr = 0.27 Pa had some degree of a monoclinic phase. Furthermore, the refractive index (n) and extinction coefficient (k) slightly decreased, from 2.22 to 2.17, and from 0.03 to 0.01, respectively and coating hardness (H) and Young's Modulus (E) decreased from ~ 12.9 to ~ 11.6 GPa and from ~ 153 to ~ 136 GPa respectively when PAr = 0.27 Pa was added to a PO2 = 1.07 Pa environment.

Al2O3–ZrO2 coatings were deposited using a vacuum arc deposition system equipped with two co-planar cathodes. The plasma was injected into a cylindrical magnetic duct through annular anode apertures toward a substrate or an electrostatic ion current probe positioned on the duct axis, in vacuum and in a low-pressure oxygen or argon + oxygen background. Ion current and arc voltage measurements and visual observation of the cathode spots were used to find stable arcing conditions, using a straight plasma duct configuration. The cathode spot operation and transport of the plasma beam in the duct were studied as a function of arc current (I arc = 25–200 A) and oxygen or oxygen + argon pressures (P = 0.1–1.5 Pa). Coatings were fabricated by exposing Si or WC–Co substrates simultaneously to Al and Zr plasmas using a 1/8 torus filter configuration in O2 + Ar pressures. The coating composition, structure, microhardness, adhesion, and wear behavior were studied as functions of the deposition parameters. Favorable conditions for stable arcing were obtained with I arc = 75 and 100 A for Al and Zr plasmas, respectively. The ion current decreased, and the arc voltage increased with the oxygen pressure. Behavior of the ion current and arc voltage suggested that cathode poisoning started at P = 0.5 Pa. Deposition rates were 0.3-0.6 μm/min, depending on the substrate position. All coatings were “Zr rich”, i.e., the Zr:Al ratio was in the range of 1.2–5.6 depending on the substrate position and deposition conditions. The coatings with higher ZrO2 concentration were harder and had better resistance to wear. The coating’s hardness reached a maximum of ~22–24 GPa at a deposition temperature of 500 °C or a negative bias voltage of 75–100 V.

Thin films of Zr–O/Al–O were deposited on SKD 11 tool steel substrate using Zr and Al cathodes in a cathodic arc plasma deposition system. The substrates were mounted on a rotating holder which alternatively exposed them to plasma from the two cathodes. The influence of the Zr and Al cathode arc currents and the substrate bias on the mechanical and the structural properties of the films were investigated. Films with a nano-layered structure of alternating Al-rich and Zr-rich layers were obtained. The Zr layers contained nano-crystallites of (101) oriented t-ZrO structure. Crystallites with α-Al 2 O 3 structure were observed only when the substrate was negatively biased in the 100–150 V range. The hardness of the film decreased with the increase of Zr cathode current from 60 to 80 A, increased when the Al cathode current increased from 25 to 30 A, and decreased when the Al cathode current increased from 30 to 35 A. The hardness of the film increased with the increase of bias voltage up to − 150 V and then decreased with further increase of the negative bias. The film structure was elucidated by HRTEM microscopy. Good correlation between the residual stress and the hardness enhancement of the films was observed.

Er plasma was produced by a vacuum arc source with a truncated cone-shaped Er cathode and an annular copper anode. The plasma beam propagated into a cylindrical duct through the annular anode aperture and flowed in vacuum or in a low-pressure oxygen background along an axial magnetic field toward a substrate or an electrostatic ion current probe positioned on the duct axis. The cathode spot location and motion, the cathode erosion, the transport of the plasma beam in the duct, and the coating deposition rate were studied as a function of arc current, axial magnetic field, and oxygen pressure. Favorable conditions for stable arcs were obtained with relatively low arc current (I arc = 30 - 50 A) and an axial magnetic field of 12 mT, which confined the spot motion on the cathode apex. Under such conditions, the rates of the cathode erosion and coating deposition were ~235 mug/C and 2-5 mum/min, respectively. With higher I arc (150-175 A), the cathode spots tended to move on the circumference of the large cone base, eroding a deep groove, which significantly decreased the cathode life.

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.

Transparent conducting ZnO:Al and ZnO films of 380-800 nm thickness were deposited on glass substrates by filtered vacuum arc deposition (FVAD), using a cylindrical Zn cathode doped with 5-6 at.% Al or a pure Zn cathode in oxygen background gas with pressure P = 0.4-0.93 Pa. The crystalline structure, composition and electrical and optical properties of the films were studied as functions of P. The films were stored under ambient air conditions and the variation of their resistance as function of storage time was monitored over a period of several months. The Al concentration in the film was found to be 0.006-0.008 at.%, i.e., a few orders of magnitude lower than that in the cathode material. However, this low Al content influenced the film resistivity, ?, and its stability. The resistivity of as-deposited ZnO:Al films, ? = (6-8) × 10- 3 ? cm, was independent of P and lower by a factor of 2 in comparison to that of the ZnO films deposited by the same FVAD system. The ? of ZnO films 60 days after deposition increased by a factor of ~ 7 with respect to as-deposited films. The ZnO:Al films deposited with P = 0.47-0.6 Pa were more stable, their ? first slowly increased during the storage time (1.1-1.4 times with respect to as-deposited films), and then stabilized after 30-45 days. © 2006 Elsevier B.V. All rights reserved.

The use of magnetic fields to control cathode spot location and motion and to collimate and direct the plasma flow in vacuum arc deposition apparatus is reviewed. Retrograde and acute angle motion are used to control the location and motion of cathode spots, in order to confine them to the cathode surface facing the substrates, to prevent local overheating, and to reduce macroparticle production. Axial fields are use to collimate cathode spot produced plasma jets and to bend them around macroparticle-occluding obstacles in filtered vacuum arc deposition. Advances have been made in understanding these phenomena, but theoretical models have not yet been formulated which can predict plasma behavior sufficiently well for apparatus design.

A rectangular filtered vacuum arc plasma deposition system was used to deposit SnO2 coatings on stationary or moving 400×420 mm substrates. The system consisted of a rectangular plasma gun, a rectangular macroparticle filter, a vacuum deposition chamber, a substrate carriage and a transport mechanism. An arc discharge was ignited in the plasma gun between a rectangular cathode and an anode with a rectangular aperture, both 66×440 mm. A Sn plasma jet produced by cathode spots passed through the anode aperture into the rectangular macroparticle filter, which had two 45° bends. A magnetic coil located in the vicinity of the cathode produced a magnetic field that confined the cathode spot motion to a defined trajectory on the cathode surface. Three magnetic coils, located around straight sections of the filter, produced a magnetic field, which guided the plasma through the filter to the substrate positioned on the substrate carriage in the deposition chamber. A stationary multi-element Langmuir probe situated opposite the filter outlet was used to measure the saturated ion current density distribution, as a function of the arc current, the magnetic field strength, and the oxygen pressure. The SnO2 coatings were fabricated by deposition of the Sn plasma in low-pressure (≤0.73 Pa) oxygen background gas, either on stationary substrates, to determine the coating thickness distribution, or on moving substrates to determine dynamic deposition rate (DDR). The ion current at first increased with the arc current, Iarc, in the range of 300–450 A and then saturated with further increasing of Iarc up to 700 A. For coatings deposited on stationary substrates at Iarc=400 A and oxygen pressure of 0.7 Pa, the coating thickness distribution could be fit by a parabolic function in the direction of the long aperture axis, and was almost triangular in the perpendicular direction, with a maximum deposition rate of 37 nm/s in the beam center. The coatings deposited on moving substrates with Iarc=350 A had a DDR of ∼100 nm-m/min, 250–450 nm thickness, a relative visual light transmission of 83% or larger, and a sheet resistivity of 100–170 Ω/□. Higher current experiments suggest that a DDR of 190 nm-m/min or larger could be achieved.

The transport of a vacuum-arc produced plasma beam along a magnetized cylindrical duct was studied experimentally. The plasma source consisted of a Sn or an Al cathode and a 17-mm internal diameter annular copper anode through which the plasma beam entered into the 160-mm diameter and 500-mm length cylindrical duct. The arc current I/sub arc/ was in the range of 30-100 A. Three magnetic coils positioned coaxially with the duct axis produced an approximately axial guiding magnetic field, B/sub g//spl les/20 mT in the duct. A 130-mm-diameter movable planar disk probe, positioned normal to the duct axis, was used to measure the ion saturation current I/sub probe/ along the duct. The ion current to the duct wall, I/sub duct/, and the probe and duct floating potentials, /spl phi//sub probe/ and /spl phi//sub duct/, respectively, were measured as functions of B/sub g/ and the axial distance of the probe from the anode, L. Generally, I/sub probe/ decreased while I/sub duct/ increased with L, and the sum I/sub probe/+I/sub duct/ was approximately independent of L. For an Al arc, I/sub probe/ and I/sub duct/ initially increased as a function of I/sub arc/, reached a maximum at I/sub arc/=40--45 A, and then decreased by a factor of 2-2.5 relative to their maximal values. Both /spl phi//sub probe/ and /spl phi//sub duct/ were negative relative to the grounded anode. /spl phi//sub probe/ became significantly more negative as L or B/sub g/ increased, while /spl phi//sub duct/ depended only weakly on L and B/sub g/.

The effect of an obstacle positioned normal to a plasma jet produced by a vacuum arc plasma source on the radial distribution of ion flux in the vicinity of the obstacle was studied. This study was motivated by interest in the mutual influence of tightly packed substrates on coatings in industrial vacuum arc deposition systems. The experimental system consisted of a vacuum arc plasma source, a straight plasma duct, and a multi-probe consisting of a removable disc obstacle and a set of ring probes for measuring the radial ion flux. A dc arc discharge was ignited in vacuum between a truncated cone-shaped Cu cathode and an annular anode. The plasma jet produced by cathode spots passed through the anode aperture into the straight plasma duct. An axial magnetic field guided the plasma jet in the duct. The multi-probe consisted of a removable disc obstacle and a set of five ring probes for measuring the radial plasma flux as a function of distance from the disc obstacle. The rings and the disc probes were coaxially arranged on the multi-probe assembly and positioned so that plasma from the source passed through the ring probes and then encountered the disc. The influence of the obstacle was determined by measuring the ring ion currents, both in the presence of the obstacle, and when the disc obstacle was removed. The difference between the measured ion currents with and without the obstacle was interpreted to be the contribution of reflected or sputtered particles from the obstacle to the radial ion flux. The ring probes were biased by ?60?V with respect to the grounded anode, to collect the saturated ion current. The multi-probe was connected to a movable stem, and positioned at different distances from the plasma source.A plasma density of ~6 ? 1017 m?3 was estimated in this study based on the ion current to the obstacle. The radial ion flux collected by the ring probes increased by 20?25% due to the presence of the obstacle. As the calculated mean free path for collisions between the plasma ions and sputtered or reflected particles is much larger than the plasma path length, the plasma jet should not be affected by returning particles. Hence, the increase of the radial flux is most probably due to ion reflection from the obstacle and ionized neutral atoms sputtered from the obstacle.

A vacuum arc carbon plasma source is described, in which an arc was ignited between a cathode and an anode having In aperture, by bringing the two electrodes into contact, and parting them while current was flowing. The inter-electrode gap length was varied. A focusing magnetic field was applied in the inter-electrode gap, and a toroidal magnetic field was applied to guide plasma through a toroidal duct. The influence of the arc current (I/sub arc/), gap length (L), and focusing magnetic field (B/sub f/) on the cathode spot motion, plasma behavior, and output ion current was studied. It was shown that with I/sub arc/=150-250 A and relatively weak B/sub f/, the spots moved on the cathode periphery, causing noisy arcing and fluctuation of the output ion current, while at a lower I/sub arc/ (50-100 A) and strong B/sub f/ (/spl ges/28 mT), there were fewer spots on the cathode surface, they tended to move toward the cathode center, the arc noise decreased and the average output ion current increased. With increasing L from 2 to 18 mm, the total ion current at first rapidly increased, and then saturated at L/spl ges/10 mm. Best performance of the carbon plasma source was obtained with an arc current chosen so that with a given field configuration, the cathode spots locate in the center of the cathode surface, and with strong magnetic fields in both the electrode and toroidal filter regions.

A novel thermal spray technology — an electro-thermal chemical spray (ETCS) for producing hard coatings is presented. The experimental coating apparatus consists of a machine gun barrel, a cartridge containing the coating material in powder form, a solid propellant, and a plasma ignition system. The plasma ignition system produces plasma in pulsed mode to ignite the solid propellant. On ignition, the drag force exerted by the combustion gases accelerates the powder particles towards the substrate. Using the ETCS technique, the process of single-shot WC–Co coating deposition on stainless steel substrate was studied. The influence of process parameters (plasma energy, mass of the solid propellant and the coated powder, distance between the gun muzzle and the substrate) on the coating structure and some of its properties were investigated. It was shown that ECTS technique effectively deposited the WC–Co coating with deposition thicknesses of 100–200 μm per shot, while deposition yield of ∼70% was attained. The WC–Co coatings consisted of carbide particles distributed in amorphous matrix. The powder particle velocity was found to depend on the solid propellant mass and was weakly dependent on the plasma energy, while the particle processing temperature was strongly dependent on the plasma energy and almost independent of the solid propellant mass. Whilst increasing the solid propellant mass from 5 to 7 g, the deposition rate and yield correspondingly increased. When increasing the plasma energy, the temperature of the powder particles increased, the average carbide particle size decreased and their shape became more rounded. The deposition yield and microhardness at first increased and then achieved saturation by increasing the plasma energy.

Ternary transition-metal nitride coatings of (Ti,Zr)N, (Ti,Nb)N and (Zr,Nb)N were deposited using a triple cathode vacuum arc deposition system by simultaneously operating two cathodes of the appropriate metals in a low-pressure nitrogen background. The magnetically collimated plasma flux distribution was measured using a 13-element ion saturation current probe. The microstructure, composition, and hardness of the coatings were determined using X-ray diffraction, Auger electron spectroscopy, and Vickers indentation, respectively. The plasma flux distribution had two peaks whose relative positions were related to the two cathodes. Coatings applied to extended substrates had a compositional gradient. In almost all cases, the ternary nitrides had a single-phase solid-solution microstructure, whose lattice constants had values intermediate between those of the parent binary nitrides. The ternary coatings were considerably harder than either of the parent binary nitrides. (Ti,Nb)N had the highest microhardness: ∼50 GPa.

The distribution of plasma beams produced by Ti, Nb and Zr cathodes in a triple-cathode vacuum arc deposition system was studied. The system consisted of a triple-cathode plasma gun, straight plasma duct, sample chamber, vacuum system and computerized control system. Three cathodes were located on a circle centred on the system axis. An arc was ignited between the cathodes and an anode with three apertures, each located opposite one of the cathodes. Each cathode had a separate trigger ignition system and the cathodes could be operated simultaneously or separately. The plasma produced by the cathode spots passed through the anode aperture to a 160 mm diameter straight duct. Four magnetic field coils coaxial with the duct axis produced a magnetic field to collimate the plasma flow, and two beam steering coils whose axes were normal to the duct axis produced a magnetic field that deflected the plasma beam in the x and y directions. The saturated ion current distribution in the plasma was measured by a 13-segment multi-probe which was positioned in the sample chamber at a distance of 560 mm from the cathode plane. The measurements were carried out for each cathode operated separately in vacuum and in a background nitrogen gas at pressures of 0.4-1.33 Pa. The ion currents collected by the individual elements of the multi-probe were fitted to a two-dimensional Gaussian function. It was shown that the beam steering coils displaced the plasma beam centres in a wide range in the substrate plane. Changing the current of the X or Y steering coils displaced the beam centre linearly in the x or y directions respectively, but had only a weak effect in the y or x (i.e. orthogonal) directions respectively. The background nitrogen pressure did not influence the displacements of the plasma beam centres; however increasing nitrogen pressure decreased the distribution width. The results show that the pair of beam steering coils may direct the plasma beams to any position in the substrate plane without affecting the other beam distribution parameters.

Vacuum arcs were established on a 90-mm-diameter Ti cathode in a deposition apparatus consisting of a spacer, 122 mm-diameter annular anode, quarter-torus magnetic macroparticle filter, and a deposition chamber. A toroidal magnetic field generally parallel to the torus walls of up to 20 mT was applied. The ion current in various cross-sections of the toroidal duct was measured using: 1) a disc probe of 130-mm diameter, oriented normal to the torus axis used to measure the transmitted ion current, and 2) a hollow cylindrical probe of 135-mm diameter and 25-mm height, whose axis coincided with the torus axis, used to measure ion current losses to the duct wall. The distribution of ion current loss was studied using an 8-segment hollow cylindrical multiprobe, where the individual probes were equally distributed on the circumference of a 130-mm-diameter circle. It was shown that: 1) the ratio of ion currents collected on the cylindrical and disc probes at first decreases with increasing the toroidal field, and then becomes approximately constant; 2) the presence of the large-diameter disc probe does not influence the value of the ion current on the cylindrical probe; and 3) the maximum ion current density near the torus walls is located in the +g direction and displaces in the -(B/spl times/g) direction with increasing the toroidal field, where g and B are the vectors of the centrifugal acceleration and the magnetic field, respectively.

A filtered vacuum arc deposition system consisted of a cathode, an annular anode, a quarter torus duct macroparticle filter, and a deposition chamber. Arcs were sustained on a Ti cathode in the presence of noble background gases helium and argon, and reactive gases nitrogen and oxygen. The gas pressure was continuously varied from 3 × 10 −5 Torr (4 mPa) to 0.1 Torr (13.3 Pa). A toroidal magnetic field of up to 20 mT, and a straight field in the deposition chamber of up to 10 mT were imposed for plasma guiding. The total saturation ion current was measured with a 130 mm diameter probe. The ion current density distribution was measured with a nine-segment multi-probe, and the individual probe element currents were fitted to a two-dimensional Gaussian distribution. It was shown that in the presence of a noble gas the total saturation ion current at first increases with increasing the background gas pressure, then achieves a maximum at a pressure of 10 mTorr (1.3 Pa) for He, and at 2 mTorr (0.26 Pa) for Ar, where its value is 1.4–2 times greater than in vacuum. With further increase in the pressure the ion current strongly decreases. In the presence of reactive gases this maximum is not observed, and the total ion current strongly decreases at pressures greater than 2–3 mTorr (0.26–0.4 Pa). In contrast to this, a maximum is observed in the ion current collected on small diameter individual probes of multi-probe, positioned towards the direction of the plasma beam displacement. With increasing gas pressure, the distribution width decreases, and a displacement of the beam center is observed both in the − g direction and in the ( B × g ) direction, where B and g are vectors of the toroidal field and centrifugal acceleration, respectively. The present results show that proper substrate positioning in the deposition chamber must take into account the beam displacement due to the background gas.

An analytical solution to the problem of plasma beam transport in a toroidal magnetic filter for unmagnetized ions is derived. A two-fluid model taking into account electromagnetic and pressure forces, electron-ion collisions, magnetic force line curvature, and radial dependence of centrifugal force is used. From comparison with experimental data it is shown that the obtained solution describes well the main properties of plasma beam behavior in the filter, e.g. (1) the relative value of the ion current along the torus decreases exponentially, (2) the deflection of the plasma beam from the center of the torus correlates with the centrifugal drift of the plasma beam across a magnetic field, and (3) experiment and theory agree well on the weak correlation between magnetic field strength and filter efficiency.

The ion current distribution produced by a filtered vacuum arc deposition system consisting of a 90-mm diameter cathode, 122-mm internal diameter anode, and a 240-mm major radius / 80-mm minor radius quarter-torus duct macroparticle filter was measured with a nine-element multi-probe, and the total ion current was measured with a 130-mm diameter probe. Arcs were sustained on Ti and Sn cathodes, with currents of 300–340 and 160–175 A, respectively. Radial magnetic fields of up to 3 mT were imposed on the cathode surface for cathode spot rotation, and fields of up to 20 mT generally parallel to the duct were imposed for plasma guiding. In general, the plasma distribution function exiting from the duct was approximately Gaussian, but with an offset from the center of the duct. At the torus exit, the Ti plasma beam was offset 12 mm towards the outside of the torus at B = 4 mT, while with increasing toroidal field the beam center moved towards the center of the duct, and reached the center at B = 8 mT. The beam was offset towards the inside of the torus for B > 8 mT, reaching a displacement of up to 5 mm for B = 12 mT. The Sn beam, by contrast, was shifted towards the inside of the torus, and the displacement from the center was as much as 15 mm. In addition, for both cases an offset in the (B × g ) direction was observed, where B is the duct magnetic field vector and g is a vector pointing outward from the toroidal center of curvature. The displacements from the center were stronger for Sn plasma (up to 16 mm) than for Ti plasma (up to 7 mm). The displacement from the center in both directions grew with the distance from the exit of the torus. A beam steering coil, whose axis was normal to the axis of plasma duct, was used to shift the plasma beam center towards the chamber axis.

Sn−O transparent, conductive thin films were produced in a filtered vacuum-arc deposition system, consisting of a 90 mm diameter cathode, 122 mm diameter annular anode, and a magnetic quarter torus macroparticle filter. Arc current was in the range 30–200 A and the toroidal magnetic field ( B T ) was in the range 0–25 mT. A radial magnetic field ( B r ) at the cathode surface was produced by a coil placed inside a cavity in the cathode. Cathode spot motion, plasma jet motion through the toroidal field, and the characteristics of the deposited Sn−O films were studied as a function of arc current, applied magnetic fields and oxygen pressure. Cathode spot motion on the cathode surface was controlled by B T . Random spot motion on the entire cathode surface was obtained in vacuum when Br was less than 2 mT. The spots were forced to move on a circular path with average radius of 25 mm when B r was larger than 2 mT. Cathode surface oxidation occurred when oxygen was introduced into the system, and its rate increased with the gas pressure. The extent of the oxidized area on the cathode surface was affected not only by gas pressure, but also by the magnitude of arc current and the magnetic fields B r and B T . With B r smaller than 2 mT, oxidized surface regions appear on the cathode, and cathode spot activity on them is disturbed. Random cathode spot motion continues undisturbed on non-contaminated regions of the cathode surface. Cathode spots were hardly observed on the oxidized regions, yet visual examination of the cathode surface used in the arc revealed the existence of cathode spots erosion tracks on them. Transparent and conductive tin oxide films were produced at oxygen pressures of 0.8 Pa when arc operation and the plasma jet in the filter were stable. The stability of the arc and the plasma jet were found to depend on the combination of gas pressure, arc current and magnetic fields. When the plasma jet was not stable poorly conductive films were produced, containing the non-conductive oxide SnO.

Arc discharges were established on a Ti cathode in vacuum in an arc deposition system with a toroidal macroparticle filter. A magnetic field with a radial component of up to 3 mT on the cathode surface at the distance of 20 mm from the cathode center was applied in order to drive the cathode spots in an azimuthal motion on the front surface of the cathode, and an axial component of the field of up to 30 mT was applied parallel to the walls of the plasma ducts leading from the cathode region to the substrate in order to collimate the plasma beam. Cathode spot motion was observed by means of a television camera and VCR via a window installed at the substrate holder flange and a mirror located in the quarter torus. Ion current convected by the plasma beam was measured with a negatively biased probe. It was shown that the magnetic field of the coils located on the plasma duct has a strong influence on cathode spot behavior. If they produce a field stronger than 4 mT at the cathode surface, the spots move off ...

Arcs were established on a Ti cathode in a filtered vacuum arc deposition system in vacuum and in a low pressure (0.1–0.67 Pa) nitrogen atmosphere. External magnetic fields of up to 25 mT were applied with a radical component in the vicinity of the arc cathode in order to drive the cathode spots in an azimuthal motion on the front surface of the cathode, and with an axial component parallel to the walls of the plasma ducts leading from the cathode region to the substrate in order to collimate the plasma beam. Cathode spot motion was observed by means of a television camera and VCR via a window installed at the substrate holder flange, and a mirror located in the quarter-torus. Ion current convected by the plasma beam was measured with a negatively biased probe. It was shown that the magnetic field coils located on the plasma ducts have a strong influence on cathode spot behaviour. If their field is stronger than 4 mT at the cathode, the spots move off the cathode surface, and the probability of their return is slight. The arc voltage increases, and the arc becomes unstable, and tends to extinguish. Location of the cathode spots on the side of the cathode, which becomes increasingly likely with increasing duct coil current, results in a decrease in the plasma flux through the plasma duct, leading to an optimal field current for optimizing the plasma output flux.

An Er plasma was produced by a vacuum arc source with a truncated cone-shaped Er cathode and an annular copper anode. The plasma beam was injected into a cylindrical magnetic duct through the annular anode aperture and flowed towards the substrate or an electrostatic ion current probe positioned on the duct axis, in vacuum or in a low-pressure oxygen background. The cathode spot operation, transport of the plasma beam in the duct, and coating deposition rate were studied as a function of arc current, axial magnetic field and oxygen pressure. Favorable conditions for arcing were obtained with relatively low arc current (Iarc=30-50 A) and an axial magnetic field of 12 mT, which confined the spot motion on the cathode apex. Under such conditions, the arc operated stably, and the cathode erosion (~235 mug/C) and coating deposition rates (2-5 mum/min) were very high. With higher Iarc (150-175 A), the cathode spots tended to move on the circumference of the large cone base, eroding a deep groove, which significantly decreased the cathode life.

Transparent and conducting SnO2 films of 57-200nm thickness were deposited on microscope glass slide substrates, using a rectangular filtered vacuum arc deposition system. The 40 glass slides were equally distributed on a 400 × 420mm substrate carriage, and were exposed to a Sn plasma beam, produced by a rectangular vacuum arc plasma gun with a Sn cathode, and passed through a rectangular magnetic macroparticle filter towards the substrates. The carriage with the substrates was transported past the 94 × 494mm filter outlet. The SnO2 films were fabricated on the glass substrates at room temperature by maintaining the chamber oxygen background pressure at 0.52Pa. The film composition, and electrical and optical properties were studied as a function of the film thickness. The films were stored under ambient air conditions, and their electrical resistance was measured as a function of storage time over a period of several months. The average resistivity of films was 10-17m? cm for films with thickness (t) less than 100nm, but that of t > 100nm it was 5-9m? cm. The resistivity of the films with t > 100nm did not change significantly after 8months of storage in ambient air. The optical transmittance of the films in the visible spectrum was in the range of 75-90%. The optical constants, i.e., the refractive index and the extinction coefficient of the films at wavelength ? = 550nm were in the range of 2.02-2.09 and 0.013-0.023, respectively, and the optical band gap energy was 4.15-4.21eV. Unlike the electrical resistivity, the optical parameters weakly depended on t. © 2008 Elsevier B.V. All rights reserved. Ministry of Education, Science and Technology The authors gratefully acknowledge financial support from the Israeli Ministry of Science and Technology, Mr. M. Govberg for his engineering assistance, Mr. D. Abunie and Mr. Y. Epstein for their assistance in conducting the experiments, Mr. O. Margulis for his assistance in figure preparation, Dr. L. Burshtein for XPS studies, and Dr. Y. Rosenberg for the XRD analysis.

The plasma beam produced by a vacuum arc plasma source was injected into a cylindrical duct through an annular anode aperture. The plasma source consisted of a frustum cone-shaped Cu cathode, and either a 20-mm-thick annular Cu anode with aperture diameter D of 10, 17, 30, 40, or 50 mm, or 35 mm thick and D=40 or 50 mm. Magnetic coils positioned coaxially with the duct axis produced an approximately axial magnetic field guiding the plasma in the duct. The arc current, I/sub arc/, was in the range of 30-100 A. A 130-mm-diameter negatively biased planar disk probe, positioned normal to the duct axis at a distance of 150 mm from the anode exit, was used to measure ion saturation current I/sub p/. I/sub p/, as well as the ion saturation current to the duct wall I/sub d/, the arc voltage V/sub arc/, and the probe and duct floating potentials with respect to the anode /spl phi//sub p/ and /spl phi//sub d/, were measured as functions of D, I/sub arc/, and the axial magnetic field B. Generally, I/sub p/ and I/sub d/ increased with D and I/sub arc/. For D=10 mm, I/sub p/ was /spl sim/0.4% of I/sub arc/, while with D=50 mm, I/sub p/ reached /spl sim/9.5% of I/sub arc/. However, with large D, the probability of the arc extinguishing increased. Both /spl phi//sub p/ and /spl phi//sub d/ were negative relative to the anode. /spl phi//sub p/ became increasingly negative with increasing D, and approximately linearly depended on D. With a small D, I/sub p/ and I/sub d/ increased almost linearly with B, while /spl phi//sub d/ was almost independent of B. However, for a large D, I/sub p/ and I/sub d/ were only slightly affected by B, and /spl phi//sub d/ became less negative with increasing B.

Arc operation was studied in a vacuum arc deposition apparatus consisting of a Ti cathode, spacer, annular anode, straight duct, quarter torus macroparticle magnetic filter, and a deposition chamber. Superposition of fields from different magnetic coils allowed the formation of different field configurations in the vicinity of the cathode and in the cathode-anode gap. The analytical study of these fields together with the observation of cathode spot motion, made it possible to demonstrate the action of two mechanisms causing unstable arcing: (1) cathode spot movement off of the cathode surface to the side in the direction of the opening of the acute angle formed by the intersection of the field lines with the cathode surface, and (2) cutoff from the anode of the magnetized electron flow by the field lines. With an optimal field configuration both of the above mechanisms were avoided. The field configuration included (1) an arched field on the cathode surface, which rotated the cathode spots on the cathode surface, and (2) connection of a sufficient portion of the cathode surface to the anode with magnetic field lines, so that the random electron current in the vicinity of the anode can supply the required arc current.

On the basis of self-consistent two fluid hydrodynamic model taking into account electromagnetic and pressure forces, electron-ion collisions, magnetic force line curvature and radial dependence of centrifugal force the analytical solution of the problem of vacuum arc plasma beam transport in a quarter-torus magnetic filter is obtained. From comparison with experimental data it is shown that the solution obtained describes well the main properties of plasma beam behavior in the filter, e.g., (1) the relative value of the ion current along the torus decreases exponentially, (2) the deflection of the plasma beam from the center of the torus correlates with the centrifugal drift of the plasma beam, and (3) experiment and theory agree well on the weak correlation between magnetic field strength and filter efficiency.

Two plasma beams of different materials were produced from Ti, Zr, or Nb cathodes in a triple-cathode vacuum arc deposition apparatus. The cathodes were arranged in a circle centered on the system axis. The plasma produced by the cathode spots was transported through a straight plasma duct with an axial magnetic field, into a sample chamber, in which a single Langmuir probe, an array of probes, or a substrate could be mounted 560 mm from the cathode plane. The saturation ion current produced by one cathode, or by the simultaneous operation of two different cathodes, was measured in vacuum and in a 0.13-2.7 Pa nitrogen background. The spatial distribution of the composition of coatings deposited during simultaneous operation of different cathodes in nitrogen was also studied. It was shown that the ion current produced by each single cathode decreased by a factor of 20-100, and by a factor of ten during simultaneous operation of two cathodes, when the nitrogen pressure was increased from vacuum to P=2.7 Pa. During simultaneous operation of two cathodes, the ion saturation current was less than the sum of the ion currents produced by each cathode individually when P

A vacuum arc carbon plasma source is described, in which an arc was ignited between a cathode and an anode having an aperture, by bringing the two electrodes into contact, and parting them while current was flowing. The inter-electrode gap length was varied. A focusing magnetic field was applied in the inter-electrode gap, and a toroidal magnetic field was applied to guide plasma through a toroidal duct. The influence of the arc current (I/sub arc/), gap length (L), and focusing magnetic field (B/sub f/) on the cathode spot motion, plasma behavior and output ion current was studied. It was shown that with I/sub arc/=150-250 A and relatively weak B/sub f/, the spots moved on the cathode periphery, causing noisy arcing and fluctuation of the output ion current, while at lower I/sub arc/=50-100 A and strong B/sub f//spl ges/28 mT the number of the spots on the cathode surface decreased, and they tended to move towards the cathode center, decreasing the arc noise and increasing the average output ion current. With increasing L from 2 to 18 mm, the total ion current at first rapidly increased, and then saturated at L/spl ges/10 mm.

The cathode spot vacuum arc produces a jet of highly ionized plasma plus a spray of liquid droplets, both consisting of cathode material. The droplets are filtered from the plasma by passing the plasma through a curved, magnetized duct. A radial magnetic field may be applied to the face of the cathode to rotate and distribute the cathode spots in order to obtain even erosion and avoid local overheating. The choice of axial magnetic field strength in the vicinity of the cathode is a compromise between a relatively high field desired to collimate a large fraction of the plasma flux, and the need to collect a substantial fraction of the plasma at the anode in order to reduce arc voltage and insure arc stability. The transmission of the filter duct increases with magnetic field strength until a saturation value is reached. Entrainment of the droplets in the plasma jet can decrease the effectiveness of the filter at high plasma flux. Semiconducting thin films of amorphous silicon were prepared using cathodes of heavily B-doped Si. Arcs of 35-A current produced a deposition rate of 10 /spl Aring//s. The electrical conductivity of the films was similar to conventional a-Si:H films deposited by conventional Silane based PACVD at high temperatures, but had a higher room-temperature conductivity. Transparent conducting films of Sn-O were deposited at rates of up to 100 /spl Aring//s using 160-A arcs on a Sn cathode while injecting O/sub 2/ gas in the vicinity of the substrate. Adjustment of the O content is critical for optimizing conductivity, and complicated by pumping effects of the arc. Optimal conductivity was achieved at an oxygen pressure of 6 mtorr. Conductivities equal to the best reported to date were achieved by subjecting the room-temperature deposited films to a 30-s rapid thermal annealing at 350/spl deg/C. Both the deposited and annealed films are amorphous. The deposition rates achieved by the filtered vacuum arc technique for these semiconductor films are an order of magnitude greater than achieved with conventional methods, while the conductivities are equivalent or better.

The vacuum arc is a high-current, low-voltage electrical discharge which produces a plasma consisting of vaporized and ionized electrode material. In the most common cathodic arc deposition systems, the arc concentrates at minute cathode spots on the cathode surface and the plasma is emitted as a hypersonic jet, with some degree of contamination by molten droplets [known as macroparticles (MPs)] of the cathode material. In vacuum arc deposition systems, the location and motion of the cathode spots are confined to desired surfaces by an applied magnetic field and shields around undesired surfaces. Substrates are mounted on a holder so that they intercept some portion of the plasma jet. The substrate often provides for negative bias to control the energy of depositing ions and heating or cooling to control the substrate temperature. In some systems, a magnetic field is used to guide the plasma around an obstacle which blocks the MPs. These elements are integrated with a deposition chamber, cooling, vacuum gauges and pumps, and power supplies to produce a vacuum arc deposition system.