Cathodic Vacuum Arc Research Articles

Performance of amorphization AlCrTiZrMo high entropy alloy barrier for copper metallization

A reliable ultra-thin diffusion barrier is required for Cu interconnection. High entropy alloy (HEA) films have received attention in the development of diffusion barrier materials due to their remarkable properties. Here, the dense and smooth 17 nm AlCrTiZrMo high entropy alloy amorphous film (HEAAF) is obtained by the cofilter cathode vacuum arc deposition. After annealing at 700 °C for 1 h, no Cu-silicide compounds are formed and the sheet resistance is 0.27 Ω/□, which indicated that AlCrTiZrMo HEAAF has excellent diffusion barrier performance. Such barrier temperature is comparable to some ceramic barriers. The excellent diffusion barrier performance of AlCrTiZrMo HEAAF is due to its good stability of amorphous structure and chemical stability at high temperature.

Study on the microspot splitting characteristics of pulsed cathodic vacuum arc

The intense pulsed current superimposed on direct current arc discharges can promote arc spot splitting and reduce macroparticle ejection. In this study, the effects of different arc parameters including peak current, magnetic fields, pulse frequency and duty cycle on spot splitting characteristics for the pulsed cathodic arc discharge, as well as mechanisms involved in microspot formation, are investigated. The results show that under the effect of periodic micro-explosive emissions, the micro-spot splitting at the peak of the pulse displays a multi-stage annular expansion phenomenon, and its expansion radius increases with the increaseing peak current; the increasing transverse component of the arc source magnetic field gradually changes the microspot splitting pattern from annular expansion to arc-shaped expansion; the plasma motion after the micro-explosion requires a period of time to “accumulate force.” In addition, an increase in pulse frequency leads to a gradual reduction in the range of the microspot splitting, in which the microspots are in a relative aggregation state; an increase in duty cycle, leads to an instability in the continuous motion of the microspots after the splitting in the peak period. This causes some of the microspots to merge, exhibiting a trend similar to the direct current arc.

Mechanical and corrosion properties of hydrogen-free DLC coatings prepared on degradable as-extruded WE43 alloy using FCVA technology

Magnesium alloys have great potential for medical applications. However, their rapid degradation has limited their development. Hydrogen-free DLC coatings were deposited on WE43 using filtered cathodic vacuum arc (FCVA) technology. The influence of different negative bias voltages on the microstructure and mechanical and corrosion properties of the coatings was systematically analyzed. The research demonstrated that application of a negative bias voltage altered the surface morphology of hydrogen-free DLC coatings with amorphous structures. In addition, the coatings exhibited a decrease in hardness and elastic modulus until the negative bias voltage reached −75 V, indicating that the increase may be attributed to the rise in sp2 cluster size and the fall in sp3 content. Furthermore, electrochemical experiments demonstrated that the coated samples exhibited superior anti-corrosion properties. The coatings deposited at −75 V displayed the highest corrosion resistance, as evidenced by their minimal corrosion current (4.53 μA·cm−2), maximal film resistance (2576 Ω·cm2), and charge transfer resistance (3171 Ω·cm2). Hydrogen evolution experiments indicated that the hydrogen-free DLC coatings effectively reduced WE43 corrosion and hydrogen gas production.

Cathodic Vacuum ARC Multilayer Coatings (TiZrSiY)N/NbN: Structure and Properties Depending on The Deposition Interval of Alternate Layers

Two series of multilayer coatings with different numbers of bilayers (268 and 536, respectively) were synthesised using the cathodic vacuum-arc deposition (CVAD) with the simultaneous sputtering of two different cathodes. The first cathode was made of the multicomponent TiZrSiY material, and the second one was made of technical niobium. The coatings were condensed in a nitrogen atmosphere at a constant negative bias potential applied to the substrate. The resulting coatings have a distinct periodic structure composed of individual layers of (TiZrSiY)N and NbN with the thicknesses determined by the deposition interval (10 or 20 s, respectively). The total thicknesses of the coatings determined by the number of bilayers were 11 and 9 microns, respectively. The formation of polycrystalline TiN and NbN phases with grain size comparable to the size of the layers has been identified for both series of coatings. The layers exhibit a columnar structure growth with a predominant orientation (111). The hardness of the experimental coatings depends on the thickness of the layers and reaches 39.7 GPa for the coating with the smallest layer thickness. The friction coefficient of the obtained coatings varies from 0.512 to 0.498 and also depends on the thickness of the layers. A relatively large value of the friction coefficient is due to high roughness and the presence of a droplet fraction on the surface as well as in the volume of the coatings.

Controlling adhesion and thermal stability of tetrahedral amorphous carbon coatings with intermediate sp3C fraction

Tetrahedral amorphous carbon (ta-C) coatings with an intermediate sp3C fraction were deposited on single-crystal silicon wafer substrates via intermittent filtered cathode vacuum arc (FCVA) deposition. The ta-C layer thickness and sp3C fraction in the coatings were adjusted using the deposition duration and bias voltage applied to the substrate, respectively. Some of the coated specimens were annealed at 300 and 600 °C for 4 h in a 5-Pa vacuum. The morphologies and microstructures of the specimens were characterized using scanning electron microscopy and transmission electron microscopy. The hybridization of carbon atoms was analyzed using X-ray photoelectron spectroscopy and micro-Raman spectroscopy. The mechanical characteristics of the coatings, including the critical adhesion load between the coatings and substrates, residual stress in the coatings, and hardness, were characterized. For the specimens deposited by the same bias voltage, even their top ta-C layer thickness ranged from approximately 500 nm to 1500 nm, their residual compressive stress in the coatings was maintained at a low value by the intermittent deposition of FCVA, which varied slightly with the coating thickness. The adhesion strength was improved by increasing the thickness of the as-deposited coating from approximately 12 to 40 N. The residual compressive stress of the post-annealing specimens with sp3C fraction of 45–53.8 % exhibited monotonously increasing or V-shaped variation with increasing annealing temperature. Herein, the underlying mechanisms are discussed in detail.

Nitrogen-containing diamond-like carbon deposited on glass substrate via filtered cathodic vacuum arc with high-frequency pulsed DC substrate bias

This research investigates the properties of nitrogen-containing diamond-like carbon (N-DLC) coatings deposited on glass substrate using a high-frequency pulsed-DC substrate bias. The study involved comprehensive investigations to understand how variations in carbon bonding affect the properties of N-DLC coatings. By adjusting the voltage, frequency and duty ratio of the pulsed bias, it was possible to deposit an optical coating with a transmittance of up to 52 % at range of 800–2500 nm while effectively preventing the peeling of the DLC coating on the glass. With increasing the clustered graphite structure in the DLC coating, the sheet resistance was lowered from 2370 kΩ/□ to 36 kΩ/□, and the electrical properties were also improved. The findings provide valuable insights for optimizing N-DLC coatings for non-conductors, e.g., glass, rubber, polymer, and engineering ceramic.

Smooth diamond-like carbon films prepared by cathodic vacuum arc deposition with large glancing angles

Diamond-like carbon (DLC) films were prepared by cathodic vacuum arc (CVA) deposition with different glancing angles (the angle between the normal reverse direction of the arc target and the normal direction of the substrate surface) in range of 0 to 135°. The effects of the glancing angle on the morphology, carbon structure, mechanical property and tribological behavior of the DLC films were investigated. The results show that the surface quality of the DLC films is significantly improved by increasing the glancing angle. The macroparticles in the surface as well as the surface roughness of the DLC films decrease sharply as the glancing angle increases. The sp3/sp2 of the DLC films decreases at first and then increases as the glancing angle increases. The normal incidence energy of the Cn+ species becomes suitable to the formation of sp3-C when the glancing angle is 45°. The variation in the film hardness and compress stress at different glancing angles are similar in profile to the sp3 bond fractions. However, the compressive stress of the films could be reduced effectively by avoiding the bombardment of the Cn+ species with excessively high energy through increasing glancing angle. The tribological behaviors of the films could be also improved by changing the glancing angle. It is supposed that the CVA with appropriate glancing angle might be one way to prepare the DLC films with smooth surface, high hardness, low compressive stress and good tribological performance.

Preparation and performance of Ti/Ti-DLC composite coatings for precision glass molding

Precision glass molding (PGM) is an efficient process used for batch manufacturing of high-precision glass optical elements. In this process, nickel phosphide (Ni–P) alloy is commonly utilized as a mold material due to its superior turning properties. However, the Ni–P mold suffers from issues such as diffusion of phosphorus elements, poor wear resistance, and easy peeling of the DLC coating during molding. To address these problems, the current study proposes enhancing the molding performance of mold by depositing a composite coating layer of Ti/Ti-DLC onto the surface of Ni–P using the filtered cathodic vacuum arc technology (FCVA). The effects of different flow rates of C2H2 on Ti-DLC coatings were analyzed in terms of composition, microstructure, mechanical, tribological, and molding properties. The results revealed that as the C2H2 flow rate increased, the Ti content of coatings decreased from 13.56 to 2.17 at.%. Additionally, the film microstructure transformed from TiC polycrystalline composite films to nanocrystalline amorphous composite films and finally to amorphous films. The Ti-DLC coatings with a nanocrystalline composite structure exhibited excellent overall performance when Ti content is 7.75 at.%. These coatings are suitable as protective coatings for microstructured array mold and demonstrate good stability at a molding temperature of 500 °C.

Effect of PEO interlayer on oxidation behavior of PEO/Cr composite coating on Zr–1 Nb alloy in 1200 °C steam

The PEO/Cr composite coating on Zr–1 Nb alloy prepared by plasma electrolytic oxidation (PEO) and filtered cathodic vacuum arc deposition (FCVAD) technologies exhibited good oxidation resistance in 1200 °C steam. The PEO interlayer was gradually dissolved by Zr substrate, and M-ZrO2 to Zr3O phase transformation occurred, but it still moderated the inward oxygen diffusion and the inter-diffusion of Cr and Zr to some extent. Moreover, the PEO interlayer suppressed the formation of ZrCr2 in Zr substrate and ZrCr2O5 secondary phases in its steam oxide layer. The PEO layer and steam oxide layer could prevent from hydrogen permeation into the Zr substrate.

Microstructure and tribological behavior in ta-C films prepared by laser-induced filtered cathodic vacuum arc technique: Effect of charge voltage

As an important power supply parameter, charge voltage has a significant influence on the properties of deposited films. In this work, the ta-C films were fabricated by the laser-induced filtered cathodic vacuum arc technique (LI-FCVA). The effect of charge voltage on microstructure, mechanical and tribological properties of ta-C films was investigated. Although macro-particles with various sizes were clearly visible on surfaces of films, the surface roughness was declined with increase of charge voltage. The sp3-C bond ratio in films was closely dependent on the charge voltage. At 160 V charge voltage, the sp3-C bond ratio was 54.1 %, then reaching to 61.2 % at the charge voltage of 190 V. With further increasing to 250 V, the sp3-C ratio slowly down to 57.1 %. This is ascribed to the change in energy for incident carbon ions which governed by the charge voltage. The highest hardness value, 54.5 ± 2.1 GPa, was obtained at the 190 V charge voltage, which was due to the high sp3-C content and relatively high residual stress. Similarly, the film deposited at 190 V possessed both low coefficient of friction (COF) and wear rate under various load, indicating that the excellent tribological performance of film could be achieved at 190 V. In addition, the COFs for all films decreased with an increase of load. The present work revealed that the moderate charge voltage value is beneficial for the enhanced wear property of film.

High temperature oxidation of CrAl-coated Zr–1 Nb alloy in 1000 – 1300 °C steam

The CrAl coating of 13 µm thick on Zr–1 Nb alloy prepared by filtered cathodic vacuum arc deposition with Cr70Al30 target exhibited excellent steam oxidation resistance below 1200 °C, but its protective properties were obviously weakened at 1300 °C. The mass gain of CrAl-coated alloy was 7.8%, 6.5%, 16.6% and 66.0% of that of bare alloy after 3600 s oxidation at 1000 °C, 1100 °C, 1200 °C and 1300 °C, respectively. The addition of a little Al in CrAl coating was beneficial to further suppress oxygen diffusion into alloy substrate due to the hindering effect of Al2O3 against oxygen atoms.

(AlCrMoTiNi)1-XNX high entropy ceramic with high hardness and toughness prepared by co-filtered cathodic vacuum arc deposition

High entropy ceramic (HEC) coatings have become candidates for new protective coating due to their high strength. However, the hardness - toughness balance of the ceramic coatings is still a difficult problem to solve. The strong nitride forming elements Al, Ti, Cr, Mo, and the non-nitride forming element Ni were selected as the components of the (AlCrMoTiNi)1-XNX HEC coatings to regulate the hardness and toughness. When x = 0 and 0.29, the composite structure of amorphous and metallic Ni phase is observed in these coatings. When x = 0.37, 0.40, and 0.45, the phase structure changes to the composite structure of nanoscale face-centered cubic (FCC) phase, metallic Ni, and amorphous phase. When x = 0.45, the maximum hardness of the HEC coating is 31.25 GPa, and it also has high toughness with a KIC value of 3.25 MPa m1/2. The HEC coating with high hardness and toughness also presents excellent wear resistance and corrosion resistance. Therefore, the (AlCrMoTiNi)0.55N0.45 HEC coating has potential as a protective coating applied in various areas.

Deposition of nanometer-thick amorphous carbon films by filtered cathodic vacuum arc under oblique ion incidence conditions

Filtered cathodic vacuum arc (FCVA) is a promising technique for synthesizing extremely thin carbon films exhibiting highly tetrahedral (sp3) carbon atom hybridization. However, most FCVA studies are for incident ions impinging perpendicular to the substrate surface. In this study, the effects of the ion incidence angle on the thickness, structure, and surface roughness of amorphous carbon (a-C) films deposited under different substrate bias voltages were examined in the light of computational and experimental results. Dynamic simulations and film thickness measurements showed a decrease in film thickness with increasing ion incidence angle, attributed to the decrease in carbon ion fluence on the film surface. Carbon atom hybridization analysis revealed a critical ion incidence angle for a given substrate bias voltage. Simulation and experimental results demonstrated that the enhancement of sp3 hybridization resulted from carbon-carbon collision cascades on the growing film surface and densification induced by direct and recoil implantation processes controlled by the ion incidence angle and substrate bias voltage. The strong dependence of a-C film growth on the carbon ion incidence angle exemplified by the results of this study has direct implications in the oblique deposition of ultrathin a-C films with predominant tetrahedral carbon atom hybridization. The present study provides a framework for optimizing the ion incidence angle to achieve the deposition of a-C ultrathin films with high sp3 contents.

Atomic insights on nanoindentation-induced plastic-deformation behavior of tetrahedral amorphous carbon film

The nanoindentation-induced deformation behavior of the Cr-doped diamond-like carbon (DLC) films was clarified with Cr concentration varying from 0 to 16.5 at.% by experiment and molecular dynamics simulation. The Cr-DLC films were fabricated by a direct cathode vacuum arc technique and Cr dopants existed in the form of stripes owing to the deposition features. Results showed the addition of Cr facilitated the transformation of sp3-C bonds to sp2-C bonds, resulting in a decrease of the hardness and elastic modulus. Especially, the sp2 nano-crystallites with the lamellar structure were found in the Cr (16.5 at.%)-DLC film. During nanoindentation, the ring-like cracking on the surface and lateral crack at the interface are exhibited in the Cr-free DLC film, while the introduction of Cr makes the DLC film alleviate the cracking trend. According to the atomic-scale analysis, Cr can significantly improve the plasticity of the DLC film because the Cr-rich cluster with a high free volume can facilitate the shear transformation zones percolation and the shear bands (SBs) nucleation by collective coordinated vortex-like movements of atoms. The Cr-free DLC film can hardly accommodate high plastic strain with very few fine SBs and blockage of the SBs.

Improved deposition quality of calcium-phosphate coating on the surface of WE43 magnesium alloy via FCVA sputtering pretreatment

Calcium-phosphate (CaP) coatings have been widely used in the field of biodegradable magnesium alloys. This paper provides a novel pretreatment method before depositing CaP coatings on the surface of WE43 biomedical magnesium alloys. The surface morphology, phase composition, corrosion resistance and in vitro biological properties of coated samples were investigated. The results showed that a uniform and dense CaP coating formed on the surface of WE43 magnesium alloy pretreated by FCVA (Filtered Cathode Vacuum Arc Technology) possessed better corrosion resistance. Compared with WE43 substrate, Icorr of FCVA/CaP sample decreased by 85.56%. The ALP activity, OD value of COL secretion and mineralization of FCVA/CaP sample reached nearly 2 times higher than that of bare WE43.

Lithiophilic Zn3N2-Modified Cu Current Collectors by a Novel FCVA Technology for Stable Anode-Free Lithium Metal Batteries.

Anode-free lithium metal batteries (AFLMBs) offer high-energy-density battery systems, but their commercial viability is hindered by irregular lithium dendrite growth and "dead Li" formation caused by current collector defects. This study employed filtered cathode vacuum arc (FCVA) technology to fabricate Cu current collectors (CCs) with a lithiophilic Zn3N2 film. This advanced preparation process ensures an evenly distributed film that reduces the nucleation overpotential, homogenizes the interfacial electric field during plating/stripping processes, inhibits lithium dendrite growth, and forms a stable solid-electrolyte interphase (SEI). Our results show that the advanced Zn3N2@Cu CCs exhibit superior performance with a high CE of above 99.3% after 230 cycles at a current density of 0.5 mA cm-2 and an area capacity of 1 mAh cm-2. Additionally, Li-Zn3N2@Cu||Li-Zn3N2@Cu symmetrical cells had a longer stable cycle time of over 1000 h than that of Li||Li and Li-Cu||Li-Cu symmetrical cells at a current density of 1 mA cm-2 and an area capacity of 2 mAh cm-2. Compared with bare Cu CCs, the capacity retention rate is increased from 14.9 to 63.1% after 100 cycles with a 0.5C rate in the AFLMBs with LFP as the cathode. This work provides a pioneering, eco-friendly, and effective solution for the fabrication of anode CCs in AFLMBs, addressing a significant challenge in their commercial application.

Dry wear behavior of identical tetrahedral amorphous carbon nanofilms on sintered composites and metal substrate with varying load bearing capacities

Diamond-Like Carbon (DLC) coating is an effective surface treatment method for improving the tribological properties of machine elements and tool materials. Among them, the tetrahedral amorphous carbon (ta-C) coating has recently received much attention due to its high hardness and good heat resistance. When characterizing friction and wear patterns related to the lifetime and cost, the thickness of the ta-C coating and the type of substrates play an important role. In this paper, ta-C coatings of two thicknesses are deposited on 304 stainless steel (SS) and cemented carbide (WC–Co), which have significant differences in mechanical properties, through filtered cathodic vacuum arc (FCVA) equipment. After ta-C coating on substrates, the tribological properties of each sample are investigated. As a result, compared to bare materials, ta-C-coated materials have a reduced coefficient of friction and improved wear resistance. However, as the base material is softer, tearing occurs in a thin coating so that a thicker ta-C coating might improves the tribological properties. Since thicker ta-C coatings do not always improve tribological properties, the efficiency can be increased by customizing the ta-C coating thickness according to the substrate layer material.

Effect of Thermal Shock on Properties of a Strongly Amorphous AlCrTiZrMo High-Entropy Alloy Film.

AlCrTiZrMo high-entropy alloy (HEA) films with strong amorphization were obtained by co-filter cathode vacuum arc deposition, and the effect of thermal shock on the films was investigated in order to explore the protection mechanism of HEA films against mechanical components in extreme service environments. The results show that after annealing at 800 °C for 1 h, the formation of a dense ZrTiO4 composite oxide layer on the surface actively prevents the oxidation from continuing, so that the AlCrTiZrMo HEA film exhibits excellent oxidation resistance at 800 °C in air. In the friction-corrosion coupling environment, the AlCrTiZrMo HEA film annealed at 800 °C for 1 h shows the best tribocorrosion resistance due to the stable dense microstructure and excellent mechanical properties, and its ΔOCP, COF and wear rate possess the smallest values of 0.055, 0.04 and 1.34 × 10-6 mm-3·N-1·m-1.

Comparative study of the microspot splitting characteristics of direct-current and pulsed cathodic vacuum arc

Ejection of macroparticles is an inherent and unavoidable characteristic of cold cathode arc discharges. The size of the cathode arc spot's melt pool is closely related to the emitted particle size, and existing studies mostly indicate that motion velocity of arc spots can be heightened primarily by magnetic fields, thereby reducing the ejection of macroparticles. However, scant consideration has been given to avoid the fundamental nature of arc spot current concentration discharge by exploring the phenomenon of arc spot splitting. In this paper, microspot splitting characteristics of direct current and pulsed cathodic vacuum arc were compared and analyzed to investigate the effect of pulsed discharges on the arc spot's internal structure, splitting, and kinematic characteristics. The results showed that pulsed arc discharges emit a dense, highly ionized plasma flow which impacts the relatively thin positive charge layer instantaneously during the peak pulsed period. This then produces a highly ionized plasma region, while also promoting an effect by which the arc spot is split into multiple microspots. Additionally, the degree of dispersion resulting from microspot splitting is positively correlated with the ratio of the plasma flow density to the concentration of the positive charge layer at the moment of microexplosion. Therefore, the microspot splitting effect of a second-order pulsed arc is weaker than that of a first-order pulsed arc. Moreover, the splitting characteristics indicated a trend toward the progressive splitting state of the direct current cathode arc. When the peak current of the single-order pulsed arc was increased from 100 to 400 A, the particle refinement effect on the surface of the CrN coating became much more evident compared to the effect of a 200 A arc in the direct current mode. And upon reaching a peak current of 500 A (and up to 600 A), the number of splits did not increase linearly due to the continuous increase in the discrete degree of microspot splitting and concurrent decrease in microspot stability. This resulted in relatively high individual microspot currents, while some relative macroparticles still appeared on the coating surface.

Co(OH)2 nanoneedles grown on Cu/NF current collector with high areal capacitance for supercapacitors

Despite the demand for high energy-density supercapacitors has been realized when transition metal hydroxides are used as electrode materials, the ion diffusion dynamics are still limited by its high impedance. In this work, Cu is deposited on nickel foam (NF) by filtered cathodic vacuum arc (FCVA) technology to serve as an ion-diffusion-favored surface state. Co(OH)2 synthesized hydrothermally on this Cu/NF exhibits remarkably enhanced electrochemical properties compared with Co(OH)2 grown on pristine NF. The resultant electrode can deliver a large area capacity of 0.772 C cm−2 at 1 mA cm−2 and retain 80.92% of initial capacitance after 4000 cycles. Moreover, an assembled asymmetric supercapacitor shows a high energy density of 0.086 mW cm−2 at 0.4 mWh cm−2 with a long lifespan (80.67% retention after 3000 cycles). Our strategy may provide a new insight to prepare electrodes for assembling high areal capacitance supercapacitors.