Ti Cathode Research Articles

Lateral homogeneity variation in metal plasma immersion ion implantation and deposition

Using a cathodic arc, with a shield to reduce the droplet rate, it is possible to obtain homogeneous AlN films across substrates with diameters up to 10 cm by metal plasma immersion ion implantation and deposition (MePIIID). The film thickness varies by less than 5%, as measured by spectroscopic ellipsometry. For a sample with a diameter of 10 cm no major influence of the voltage on the thickness homogeneity was observed. However, for a sample with a diameter of 6 cm and the same deposition conditions the thickness at the edge decreased by more than 33 and 50% for pulse voltages of 5 and 10 kV, respectively. Thus, the geometry of the shield and the sample holder can have a strong influence on the direction of the plasma stream emanating from the cathodic arc. Additionally, the working pressure and plasma composition plays a major role in determining the homogeneity, as was observed using Al and Ti cathodes without background gas or with nitrogen.

Influence of high power densities on the composition of pulsed magnetron plasmas

The application of high power pulses with peak voltage of −2 kV and peak power density of 3 kW cm −2 to magnetron plasma sources is a new development in sputtering technology. The high power is applied to ordinary magnetron cathodes in pulses with short duration of typically some tens of microseconds in order to avoid a glow-to-arc transition. High plasma densities are obtained which have been predicted to initiate self-sputtering. This study concerns Cr and Ti cathodes and presents evidence of multiply charged metal ions as well as of Ar ions in the dense plasma region of the high power pulsed magnetron discharge and a substantially increased metal ion production compared to continuous magnetron sputtering. The average degree of ionisation of the Cr metal deposition flux generated in the plasma source was 30% at a distance of 50 cm. Deposition rates were maintained comparable to conventional magnetron sputtering due to the low pressure of operation of the pulsed discharge—typically 0.4 Pa (3 mTorr) of Ar pressure was used. Observations of the current–voltage characteristics of the discharge confirmed two modes of operation of the plasma source representing conventional pulsed sputtering at low powers (0.2 kW cm −2) and pulsed self-sputtering at higher powers (3 kW cm −2). The optical emission from the various species in the plasma showed an increase in metal ion-to-neutral ratio with increasing power. The time evolution within a pulse of the optical emission from Ar 0, Cr 0, Cr 1+, and Cr 2+ showed that at low powers Cr and Ar excitation develops simultaneously. However, at higher powers a distinct transition from Ar to Cr plasma within the duration of the pulse was observed. The time evolution of the discharge at higher powers is discussed.

Electrochemical oxidation of tannery wastewater

AbstractTannery wastewater was treated by an electrochemical oxidation method using Ti/Pt, Ti/PbO2 and Ti/MnO2 anodes and a Ti cathode in a two‐electrode stirred batch reactor. The changes in colour concentration, chemical oxygen demand (COD), ammonia (NH4+), sulfide and total chromium have been determined as a function of treatment time and applied current density. Gas chromatography–mass spectrometry (GC–MS) analysis, performed on the wastewater samples before and after treatment, as well as on foam samples, is reported. Anode efficiency, rate constants and energy consumption were estimated and discussed. The efficiency of Ti/Pt was 0.802 kgCOD h−1 A−1m−2 and 0.270 kgNH4+ h−1 A−1m−2, and the energy consumption was 5.77 kWh kg−1 COD and 16.63 kWh kg−1 of NH4+. The order of efficiency of anodes was found to be Ti/Pt ≫ Ti/PbO2 > Ti/MnO2. The results indicate that the electro‐oxidation method could be used for effective oxidation of tannery wastewater and a final effluent with substantially reduced pollution load can be obtained.© 2001 Society of Chemical Industry

Spatial charge effects in retarding field analyzer ion measurements in a cathodic vacuum arc

The ion energy distribution generated in a pulsed vacuum arc operated with a Ti cathode and N2 filling gas is reported. A retarding field analyzer system is employed, for which the usual derivation of the ion energy spectrum has been modified to take into account spatial charge effects in the grid-collector region of the analyzer. It allows one to interpret the decrease in the collector current at collector bias voltages unusually low (even negatives) observed in this experiment, as well as in others. It is found that spatial charge effects are more marked when the arc operates with gas filling because of the creation (by charge-exchange processes) of low energy gaseous ions which are easily stopped by the potential hump created by the positive charge in the grid-collector region of the analyzer.

Arc discharges with gas-impregnated cathodes in vacuum

Cathode material and surface conditions control parameters of the cathode spot (CS), and thus have an influence on properties of the vacuum arc discharge as a whole. A great number of various alloys and compositions have been developed to provide for improvement of operating characteristics of electrodes and arc properties due to selection of CS parameters. Some metals can be impregnated by hydrogen (H) up to an impregnation degree /spl alpha//spl sim/1 (H atom per metal atom) which corresponds to a very high concentration of H in metal matrix (up to C/spl sim/10/sup 23//spl middot/m/sup -3/). The impregnation of the cathode of the vacuum arc by H opens up new opportunities for influence upon CS parameters. The paper reflects the present state of research into vacuum are with H-impregnated cathodes. The introductory sections discuss the basic characteristics of the Me-H system and techniques of impregnation of different metals with H. The subsequent sections present the results of investigations of CS parameters and arc characteristics at various Ti cathode impregnation degrees. A comparison with characteristics of degassed cathodes demonstrated marked differences: using impregnation of a cathode with H, the velocity of CS motion grows, the current per spot falls off, erosion diminishes and droplet size decreases. A high-current arc burns steadily and at a lower voltage. The critical current for anode spot formation grows significantly. The use of H-impregnated cathodes is promising for various applications including switching apparatus, coating technique, plasma accelerators, and so on.

On a thermodynamic description of Se(IV) electroreduction and CdSe electrolytic formation on Ni, Ti and Pt cathodes in acidic aqueous solution

A discussion on tetravalent Se electroreduction and CdSe cathodic electrodeposition in terms of thermodynamics, in association with an investigation on the voltammetric behavior of Pt, Ni and Ti working electrodes in a high temperature (85 °C) acidic aqueous bath, is presented. The underpotential co-deposition of Cd with Se is described within the frame of a known electrochemical model of compound formation. The data presented serve as an effective basis for studying the electroreduction of Se(IV) as well as for determining the relevance of theoretical predictions to experimental findings on a binary compound electrodeposition process.

Experimental investigation of ion parameters in a cathodic arc plasma operated with nitrogen gas

The ion kinetic energy and ion density was determined for the plasma generated in the outer region of the arc channel in a pulsed low-pressure cathodic arc. The device was operated with N/sub 2/ gas and with a Ti cathode within the pressure range 10/sup -2/-150 Pa, with a peak current of 520 A. A retarding field analyzer, a spherical Langmuir probe, and a calorimetric system were employed. The resulting kinetic energy for both Ti/sup +/ and Ti/sup ++/ ions was 40/spl plusmn/3 eV at the cathode spots. The obtained values for the ion density are in agreement with those predicted by hydrodynamic models with spherical symmetry if the ion current penetrating into the outer region is taken as 10% of the total discharge current. It was also found that the ion density increases (and the ion kinetic energy decreases) with the filling pressure, a fact that can be attributed to an ion slowing by elastic collisions with neutrals. This behavior cannot be explained with the presence of a shock wave separating a plasma region from an unperturbed neutral gas region.

Vacuum arc deposition of TiN, NbN and TiN/NbN multi-layer coatings

Abstract Single-layer coatings of TiN and NbN, and multi-layer coatings of TiN/NbN, were deposited onto WC–Co substrates using a triple-cathode vacuum arc plasma gun connected to a cylindrical plasma duct onto which an axial magnetic field was imposed. Additional magnetic fields were applied by two beam steering coils orientated normal to the duct axis. The magnetic field produced by the steering coils directed the plasma beam onto a substrate placed on the system axis, increasing the plasma flux to the sample. The single-layer coatings were produced by generating Ti or Nb plasmas in a nitrogen background at a pressure P in the range of 0.67 to 2.67 Pa. Multi-layer coatings with 20, 50 and 100 layers were deposited by alternately switching the arcs on Ti and Nb cathodes. Coating structure and composition were studied by means of scanning electron microscopy (SEM) and X-ray diffraction (XRD). Microhardness and adhesion to the substrate were studied by Vickers' micro-indentation and scratch tests, respectively. It was shown that the phase composition of the NbN coatings depended on the deposition rate and P . The coatings deposited at low deposition rate (i.e. without the beam steering field) exhibited a single-phase cubic δ-NbN structure at P ≥0.67 Pa, whereas the coatings deposited with application of the beam steering field, at P =0.67 and 1.33 Pa, were composed of a mixture of cubic δ-NbN and hexagonal NbN 0.95 , while at P =2 and 2.67 Pa, the hexagonal phase was not found. The phase composition of the TiN coatings was independent of the deposition rate and P in the range 0.67–2.67 Pa. The highest microhardness (up to 38 GPa) and scratch critical load (80–95 N) were obtained for single-phase δ-NbN coatings deposited at P =0.67–1.33 Pa and at low deposition rate. The microhardness of multi-layer TiN/NbN coatings of 3.2–3.6 μm total thickness increased with increasing number of alternating layers, but did not exceed that of the pure δ-NbN observed in this study.

Influence of an electrical field on the macroparticle size distribution in a vacuum arc

The results of experimental study of macroparticle distribution in a vacuum arc presented for Cu, Ti, Zr, and Cr cathodes. We have studied the macroparticle contamination of the films deposited on the substrate having floating potential and biased up to −1000 V with respect to the anode. It has been found that the macroparticle number significantly decreases (by a factor of 3–4) with substrate biasing for all examined cathode materials. A model of macroparticle motion in the quasineutral plasma and near-substrate sheath was proposed. The model bases on analyses of the macroparticle charging and motion in the quasineutral plasma and near substrate sheath. The model can qualitatively explain the macroparticle reduction in the coating due to negatively charged macroparticle reflection in an electric field.

Synthesis of anatase TiO2 film by reactive vacuum arc deposition method

TiO2 in anatase crystalline structure has strong photocatalysis. In this paper, TiO2 films are deposited on soda-glass substrate using a Ti cathode vacuum arc with O2 flow. Experimental conditions are as follows: arc current, 50 A; pressure, 0.3 and 1.0 Pa; O2 flow rate, 20 ml/min; cathode–substrate distance, 250 mm; bias dc voltage to the substrate, none and –300 V. As-deposited films are annealed for 60 min under atmosphere and vacuum. The following results were obtained. (1) Deposition rate is 0.07 μm/min. (2) As-deposited films are amorphous. (3) Films annealed at 250 to 500 °C have an anatase crystalline structure. These results are independent of pressure, bias, and annealing environment. In another process, the films are deposited for 30 min when the substrate holding table is connected to the anode chamber. Experimental conditions are as follows: arc current, 50 A; pressure, 1.0 Pa; O2 flow rate, 20 ml/min; cathode–substrate distance, 250 mm. Almost 30% of the arc current was observed to flow through the substrate table, and the surface temperature of the table increased up to 450 °C. The reason for this is considered to be that Joule heating occurs when the current flows through the film deposited on the table. The film deposited in this process is dominantly anatase. The above experiments show that anatase TiO2 film can be deposited on soda-glass by the reactive vacuum arc method. © 1999 Scripta Technica, Electr Eng Jpn, 126(4): 12–20, 1999

Ti陰極N2ガス導入真空アークプラズマの質量スペクトルおよびイオンエネルギー分布計測

Ti陰極N2ガス導入真空アークプラズマの質量スペクトルおよびイオンエネルギー分布計測

Plasma distribution in a triple-cathode vacuum arc depositionapparatus

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.

Superposition of two plasma beams produced in a vacuum arc deposition apparatus

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<0.4 Pa, while the simultaneous ion current was larger than the sum of the individual ion currents when P/spl ges/0.4 Pa.

Electrode erosion and coating properties in pulsed air arc deosition of WC-based hard alloys

WC-based hard alloys were deposited from a slab source anode on to low carbon steel and pure Ti substrates using a pulsed air arc. The depositions were conducted with a series of pulses with current amplitudes of 75 A, 300 A, and 500 A, a pulse duration of 150 μs, and a pulse repetition rate of 100 Hz. The influence of the electrode material, discharge energy and deposition time on the electrode erosion rate, mass transfer direction, and the wear resistance and friction coefficient of the coatings was investigated. Anodic and cathodic mass change characteristics depended on both the anode and cathode materials. Using a steel cathode and a WC anode, depositions of the anode material always formed on the cathode. For the same WC anode but a Ti cathode, coatings only formed locally in the craters of the eroded cathode. The anodic mass loss when using the steel cathodes was about a factor of 3 larger than when using the Ti cathodes. The microhardness of the coated substrates was larger by factors of 5–12 than the uncoated Ti and low carbon steel substrates. The coatings increased the wear resistance of the steel and Ti substrates by factors of 4.3 and 1.4, respectively. The poorer performance of the coated Ti substrates is attributed to the intensive erosion of the Ti cathodes (compared to the steel cathodes) and the discontinuous nature of the coatings (i.e. only in the erosion caters).

TiN/Ti film formation by vacuum arc deposition with droplet shield plate

Ti film was deposited on an Mo substrate, a TiN film was then deposited on it, using a reactive vacuum arc deposition with a droplet shield plate located between the Ti cathode and the substrate. Substrate temperature during the process was decreased as the shield plate was moved closer to the substrate. Deposition rates of Ti and TiN/Ti films with the shield plate were less than half to a quarter of those without the shield plate. The crystalline structure of the film prepared with the shield plate did not significantly differ from that prepared without the shield plate and was independent of the plate position. The number of droplets on the film was drastically reduced when the shield plate was located farther from the substrate, but an unacceptable number of droplets remained on the film when the shield plate was located closer to the substrate.

Macroparticle distribution in a quarter-torus plasma duct of a filtered vacuum arc deposition system

The macroparticle (MP) flux distribution in a quarter-torus filtered vacuum arc deposition system was experimentally investigated and compared with theoretical predictions based on a previously developed model. The average MP flux was measured by collecting the MPs generated from a Ti cathode on substrates located at different radial positions on the entrance and the exit planes of the quarter-torus filter, and measuring the MP size distribution function using an automated microscopic image analysis system. The average MP flux along the torus centre line decreased by a factor of 50 from the entrance to the exit, while the average MP flux decrease near the outer wall of the torus was more moderate. The flux near the outer wall was greater by a factor of three than the centreline flux. Increasing the toroidal magnetic field from 4 to 10 mT resulted in no substantial change in the MP flux on the centreline, while near the outer wall it decreased by a factor of two. The experimental results on the MP flux in the near outer wall region are consistent with electrostatic reflection of the charged MPs by the charged wall.

Ion current distribution within a toroidal duct of a filtered vacuum arc deposition system

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.

ION-GAS INTERACTION IN A VACUUM ARC AT INTERMEDIATE PRESSURES

Measurements of the ion flux as a function of the pressure in a plasma arc are presented. We report data on Ti and Pt cathodes using N2 and Ar as the filling gases. Values of an effective collision cross section derived from the attenuation measurements are inferred.

反応性真空アーク蒸着法によるアナターゼ型TiO&lt;sub&gt;2&lt;/sub&gt;膜の生成

TiO2 in anatase crystalline structure has strong photocatalysis. In this paper, TiO2 films are deposited on soda-glass substrate using a Ti cathode vacuum arc with O2 flow. Experimental conditions are as follows: arc current, 50 A; pressure, 0.3 and 1.0 Pa; O2 flow rate, 20 ml/min; cathode–substrate distance, 250 mm; bias dc voltage to the substrate, none and –300 V. As-deposited films are annealed for 60 min under atmosphere and vacuum. The following results were obtained. (1) Deposition rate is 0.07 μm/min. (2) As-deposited films are amorphous. (3) Films annealed at 250 to 500 °C have an anatase crystalline structure. These results are independent of pressure, bias, and annealing environment. In another process, the films are deposited for 30 min when the substrate holding table is connected to the anode chamber. Experimental conditions are as follows: arc current, 50 A; pressure, 1.0 Pa; O2 flow rate, 20 ml/min; cathode–substrate distance, 250 mm. Almost 30% of the arc current was observed to flow through the substrate table, and the surface temperature of the table increased up to 450 °C. The reason for this is considered to be that Joule heating occurs when the current flows through the film deposited on the table. The film deposited in this process is dominantly anatase. The above experiments show that anatase TiO2 film can be deposited on soda-glass by the reactive vacuum arc method. © 1999 Scripta Technica, Electr Eng Jpn, 126(4): 12–20, 1999

Influence of gas pressure on the ion current and its distribution in a filtered vacuum arc deposition system

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.