Filtered Cathodic Vacuum Arc Research Articles

Electrical properties of FCVA deposited nano-crystalline graphitic carbon thin films with in situ treatment techniques

In this report, detailed studies of the nano-crystalline graphitic (NCG) carbon thin films deposited by filtered cathodic vacuum arc (FCVA) following its first discovery and first electrical characterization have been performed. The microstructure of carbon thin film can be modified by applying in situ treatment techniques (such as altering the thermal and carbon ion deposition energy). It was found that highly electrical conductive carbon thin films with graphitic planes can also be deposited at a low deposition temperature instead of the previously reported high deposition temperature with a 20% improvement in electrical characteristic. The detailed electrical characterization comparison between amorphous carbon and NCG has been conducted. To conclude, NCG carbon can be fabricated at deposition temperature above 400 °C and exhibits increasing through film Ohmic electrical conductivity with increasing deposition temperature. At low temperatures, NCG carbon can be produced by increasing the negative substrate bias above 300 V (impinging carbon ion energy). Higher negative substrate bias leads to thinner amorphous interface layer hence better electrical conductivity.

Tribological performance of GLC, WC/GLC and TiN films on the carburized M50NiL steel

To improve the tribological performance of M50NiL aero-bearing steel, the TiN, GLC and WC/GLC films were deposited on the M50NiL steel treated by low pressure vacuum carburizing. GLC and WC/GLC films were prepared using unbalance magnetron sputtering system, and TiN films were deposited by magnetic filtered cathode vacuum arc system. The microstructures and mechanical properties of the films were evaluated. The tribological properties of the films were investigated in different environments including dry sliding and #4010 aviation lubricant. The results show that, in dry sliding, WC/GLC film exhibits better tribological performance than GLC film under the load ranging from 5 N to 15 N, while as the load increases to 20 N, the wear rate of WC/GLC film is about 10% higher than that of GLC film. In #4010 aviation lubricant, under the full load ranging from 5 N to 30 N, TiN film shows lower friction coefficient than GLC film, and WC/GLC film performs the best tribological performance. Moreover, the wear mechanisms of TiN, GLC and WC/GLC films were analyzed.

Effect of Ti Transition Layer Thickness on the Structure, Mechanical and Adhesion Properties of Ti-DLC Coatings on Aluminum Alloys.

Multilayers of Ti doped diamond-like carbon (Ti-DLC) coatings were deposited on aluminum alloys by filtered cathodic vacuum arc (FCVA) technology using C2H2 as a reactive gas. The effect of different Ti transition layer thicknesses on the structure, mechanical and adhesion properties of the coatings, was investigated by scanning electron microscopy (SEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), nanoindentation and a scratch tester. The results showed that the Ti transition layer could improve interfacial transition between the coating and the substrate, which was beneficial in obtaining excellent adhesion of the coatings. The Ti transition layer thickness had no significant influence on the composition and structure of the coatings, whereas it affected the distortion of the sp2-C bond angle and length. Nanoindentation and scratch test results indicated that the mechanical and adhesion properties of the Ti-DLC coatings depended on the Ti transition layer thickness. The Ti transition layer proved favorable in decreasing the residual compressive stress of the coating. As the Ti transition layer thickness increased, the hardness value of the coating gradually decreased. However, its elastic modulus and adhesion exhibited an initial decrease followed by an increasing fluctuation. Among them, the Ti-DLC coating with a Ti transition layer thickness of 1.1 μm exhibited superior mechanical properties.

Effective passivation of Ag nanowire network by transparent tetrahedral amorphous carbon film for flexible and transparent thin film heaters

We developed effective passivation method of flexible Ag nanowire (NW) network electrodes using transparent tetrahedral amorphous carbon (ta-C) film prepared by filtered cathode vacuum arc (FCVA) coating. Even at room temperature process of FCVA, the ta-C passivation layer effectively protect Ag NW network electrode and improved the ambient stability of Ag NW network without change of sheet resistance of Ag NW network. In addition, ta-C coated Ag NW electrode showed identical critical inner and outer bending radius to bare Ag NW due to the thin thickness of ta-C passivation layer. The time-temperature profiles demonstrate that the performance of the transparent and flexible thin film heater (TFH) with the ta-C/Ag NW network is better than that of a TFH with Ag NW electrodes due to thermal stability of FCVA grown ta-C layer. In addition, the transparent and flexible TFHs with ta-C/Ag NW showed robustness against external force due to its high hardness and wear resistance. This indicates that the FCVA coated ta-C is promising passivation and protective layer for chemically weak Ag NW network electrodes against sulfur in ambient.

Ultrathin amorphous carbon films synthesized by filtered cathodic vacuum arc used as protective overcoats of heat-assisted magnetic recording heads

Despite numerous investigations of amorphous carbon (a-C) films, a comprehensive study of the feasibility and optimization of sub-5-nm-thick a-C films deposited onto the write pole of heat-assisted magnetic recording (HAMR) heads is lacking. The main objective of this study was to identify the role of pulse substrate bias voltage and C+ ion incidence angle on the structure and thickness of 1–4-nm-thick a-C films deposited by a rather new thin-film deposition method, known as filtered cathodic vacuum arc (FCVA). The cross-sectional structure of a-C films synthesized under various FCVA conditions was examined by high-resolution transmission electron microscopy (HRTEM), scanning transmission electron microscopy (STEM), and electron energy loss spectroscopy (EELS). It was found that film growth under process conditions of low-to-intermediate substrate bias voltage (in the range of −25 to −100 V), low ion incidence angle (10°), very short deposition time (6 s), and fixed other deposition parameters (65% duty cycle of substrate pulse biasing and 1.48 × 1019 ions/m2·s ion flux) yields a-C films of thickness ≤4 nm characterized by a significant content (~50–60 at%) of tetrahedral (sp3) carbon atom hybridization. A threshold where sp3 hybridization is greatly reduced due to limited film growth was determined from the HRTEM/STEM and EELS measurements. The results of this study demonstrate the viability of FCVA to produce extremely thin and uniform protective a-C films with relatively high sp3 contents for HAMR heads.

Control of residual stress of tetrahedral amorphous carbon thin film deposited on dielectric material by filtered cathodic vacuum arc source by using mid-frequency pulse bias voltage

It was shown that the residual stress of the tetrahedral amorphous carbon (ta-C) thin film deposited on insulating material by filtered cathodic vacuum arc (FCVA) source can be controlled with mid-frequency pulse bias voltage. The residual stress of ta-C thin film decreased monotonically with the substrate pulse bias when the base material to be coated was insulating. There was not the apparent peak of residual stress about the substrate pulse bias which appeared for the electrically conducting base material. It was observed that the residual stress increased with the arc current and dielectric thickness at some pulse voltage range (100 V–1000 V). The sp3 contents calculated by using Raman spectra and the surface hardness values as a function of substrate pulse voltage showed the similar trend with the residual stress values. For ta-C thin film deposited on the polished alumina sample, it was shown that the critical load in the scratch test decreased with the residual stress. The residual stress of ta-C on the insulating base material was explained with the change of the sheath voltage in the equivalent circuit model.

The correlation between optical and mechanical properties of amorphous diamond-like carbon films prepared by pulsed filtered cathodic vacuum arc deposition

Diamond-like carbon (DLC) films were deposited by pulsed filtered cathodic vacuum arc (FCVA) deposition. The microstructure, mechanical and optical properties of DLC films have been investigated as functions of the variation in the substrate negative direct current bias voltage (Vbias) from 0.0 to 1.5 kV. Raman and X-ray photoelectron spectroscopy results show a correlation between the ID/IG ratio and the microstructure in terms of the sp3/sp2 ratio to Vbias. This fact shows that a significant change in the sp3 content, which is attributed to the transformation from graphite-like to diamond-like, is accompanied by a decreasing ID/IG ratio. The relatively high mass density of the films in the range of 2.51 to 2.79 g/cm3 can be obtained with biasing. The mechanical properties, i.e., the hardness and elastic modulus, were 13–25 and 114–145 GPa, respectively. The improvement of the mechanical properties is due to the formation of the compressive residual stress and the local density depending on Vbias. The relationship between the refractive index and the ID/IG ratio agree well with the microstructure and mechanical properties of DLC films. All of these results indicate a vital role of Vbias in determining the DLC properties.

The novel toxic free titanium-based amorphous alloy for biomedical application

Ti based amorphous alloy exhibits excellent properties for biomedical applications. In general, it has high strength, low elastic modulus, good corrosion resistance and satisfactory biocompatibility. This work reported on a systematic study of a novel Ti44Zr10Pd10Cu6Co23Ta7, Ti44Zr10Pd10Cu10Co19Ta7 and Ti44Zr10Pd10Cu14Co15Ta7 metallic glass. Cylindrical rod samples with diameter of 5mm and 20mm length were fabricated by induction melting and casting into copper mold. The cast rod was then used as plasma cathode in filtered cathodic vacuum arc (FCVA) deposition chamber. The Ti-based metallic glass (MG) thin film was produced and tested for subsequent cell culture investigation to understand the biocompatibility nature of the new alloy. X-ray photoelectron spectrometry (XPS) was employed to characterize the surface chemistry. The Ti–6Al–4V alloy was studied in parallel as a control material. This novel Ti-based MG composition has shown promising osteoblast biocompatible characteristics and no cytotoxicity on human osteoblast-like cells (SaOS-2). Moreover, cells on Ti-based MG thin film exhibited greater levels of calcium deposition using Alizarin red staining technique to those of the control. All results point out that the novel Ti-based amorphous alloy has potential for using as a new coating for biomedical application and deserve further study.

Ti(C, N, O) Nanocomposite Films Fabricated by Filtered Cathodic Vacuum Arc Using CO 2 and N 2 as Precursors

Ti(C,N,O) films were deposited on Si(100) and 304 stainless steel by Filtered Cathodic Vacuum Arc (FCVA) using CO 2 and N 2 (with ratio of 1:1) as precursors. The effect of gas flow rate on the composition, phase structure and properties of films was investigated by XPS, XRD, Raman, SEM, tribological test and electrochemical workstation. Results show that the contents of C and N increase obviously, while contents of O and Ti decrease slightly as the gas flow rate increases from 10 mL/min to 50 mL/min. The contents of C and N decrease, while content of Ti increases slightly and content of O increases dramatically as the gas flow rates from 50 mL/min to 80 mL/min. The phase structure of Ti(C, N, O) films transformes from nc-Ti(C, N, O) nanocrystal structure to nc-Ti(C,N,O)/a-CN x nanocomposite structure, a-TiO 2 /a-CN x and N-doped a-TiO 2 /a-C nanocomposite structure with gas flow rate increasing from 10 mL/min to 80 mL/min. The N-doped a-TiO 2 /a-C nanocomposite showed the lowest friction coefficient. Both nc-Ti(C, N, O)/a-CN x nanocomposite structure and N-doped a-TiO 2 /a-C nanocomposite structure show good anticorrosion ability in Hanks balance solution.

Effect of Coil Current on the Properties of Hydrogenated DLC Coatings Fabricated by Filtered Cathodic Vacuum Arc Technique

We successfully prepared hydrogenated DLC (a-C:H) with a thickness higher than 25 μm on stainless steel using a filtered cathode vacuum arc (FCVA) technique. The structural and mechanical properties of DLC were systematically analyzed using different methods such as x-ray photoelectron spectroscopy, Raman spectroscopy, scanning electron microscopy, Vickers hardness, nanohardness, and friction and wear tests. The effect of coil current on the arc voltage, ion current, and mechanical properties of resultant films was systematically investigated. The novelty of this study is the fabrication of DLC with Vickers hardness higher than 1500 HV, in the meanwhile with the thickness higher than 30 μm through varying the coil current with FCVA technique. The results indicated that the ion current, deposition rate, friction coefficient, and Vickers hardness of DLC were significantly affected by the magnetic field inside the filtered duct.

Hybrid Ti-MoS2 Coatings for Dry Machining of Aluminium Alloys

Combinatorial deposition, comprising filtered cathodic vacuum arc (FCVA) and physical vapor deposition (PVD) magnetron sputtering is employed to deposit molybdenum disulphide (MoS2) and titanium (Ti) thin films onto TiB2-coated tool inserts specifically designed for the dry machining of aluminium alloys. Titanium is deposited by FCVA while MoS2 is magnetron sputtered. The deposition set up allows several compositions of Ti-MoS2 to be deposited simultaneously, with Ti content ranging between 5 and 96 at. %, and their machining performances to be evaluated. Milling took place using a CNC Vertical Machining Center at a 877 mm/min feed rate. The effect of different coating compositional ratios on the degree of aluminium sticking when a milling insert is used to face mill an Al alloy (SAE 6061) was investigated using a combination of energy-dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS) analysis. XPS studies suggest that the greater degree of Al sticking on the rake face of the inserts is due to the formation of greater amounts of non-protective Ti-O phases. EDX mapping of the milling inserts after machining reveal that a Ti:MoS2 ratio of around 0.39 prevents Al from sticking to the tool edges. Since we prevent Al from sticking to the tool surface, the resultant machined surface finish is improved thus validating the machining performance of TiB2-coated tools using optimum compositions of Ti:MoS2 thin film coatings.

The effect of biased plates on transport of vacuum arc plasma through rectangular curved magnetic filter

Filtered cathode vacuum arc deposition can remove the macroparticles produced from the cathode. Positively biasing the whole filter or inserting a biased plate in the filter can increase the plasma transport efficiency. We developed a curved magnetic filter with rectangular cross-section to improve the coating efficiency. In this study, the effect of biased plates at outer-wall and inner-wall on the transport efficiency of vacuum arc plasma through rectangular curved magnetic filter was investigated. A Langmuir probe system is used to measure the distribution properties of the filtered plasma at 15 places in the outlet plane of the filter. The results showed that a positively biased plate at inner-wall would increase the output ion current density and make the plasma concentrate to the middle of the outlet plane.

Fast deposition of thick diamond-like carbon films by ion-beam technique

A diamond-like carbon film doped with TiC nanocrystallites (TiC–DLC) with a thickness of 35.8 μm was successfully prepared on a stainless steel substrate by employing a combination of metal vapor vacuum arc and filtered cathode vacuum arc techniques. A maximum deposition rate of 0.25 μm/min was achieved for TiC–DLC films. The structure and properties of the TiC–DLC films were systematically analyzed using different methods such as transmission electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, scanning electron microscopy, X-ray diffraction, and friction and wear tests. The results indicated that typical a-C:H films containing nano-sized TiC grains were deposited which exhibit improved mechanical properties such as high cohesive strength, Vickers hardness, and capacity against high temperature. Parameter windows for C2H2 flow rate and solenoid current were also provided for the deposition of TiC–DLC films to meet the requirements for using the material for specific commercial applications.

Effect of Filtering Duct Coil Current on the Bonding Structure of Tetrahedral Amorphous Carbon Film

Tetrahedral amorphous carbon (ta-C) films were deposited at 200V and 500V pulse substrate bias by adjusting the filtering duct coil current ranging from 5A to 13A in filtered cathodic vacuum arc (FCVA) system. The bonding structure of ta-C films is measured by visible Raman spectroscopy. The ratio of average ion current density to deposition rate decrease with the filtering duct coil current. Meanwhile the deposition rate increases with the increment of the filtering duct coil current. The intensity ratio ID/IG of the films increases with the increment of the filtering duct coil current, which indicates the graphitization of the films concurrently increase with the filtering duct coil current.

Effect of substrate bias on the tribological behavior of ta-C coating prepared by filtered cathodic vacuum arc

Tetrahedral amorphous carbon (ta-C) films were coated on the tungsten carbide cobalt by using filter cathodic vacuum arc (FCVA). All the specimens were coated at different bias voltage, such as 0 V, 40 V, 80 V, 120 V, and 160 V. The tribological behavior of all these specimens were evaluated by using a ball-on-disc type of tribo-test. Raman analysis was used in this research for investigating the bond structure in the coating films. From the experiment result shown the variation of the bias voltage of the ta-C coating do not bought to the change of the mechanical properties. As well as for the tribological aspect. Whereas, it only bought to the influence of the wear properties. The lowest wear rate result were found from the ta-C film that coated under 40V. This was due to the surface contact area and the surface roughness properties different at the different bias voltage.

Thermal stability of ultrathin amorphous carbon films synthesized by plasma-enhanced chemical vapor deposition and filtered cathodic vacuum arc

Ultrathin hydrogenated amorphous carbon (a-C:H) films deposited by plasma-enhanced chemical vapor deposition (PECVD) and hydrogen-free amorphous carbon (a-C) films of similar thickness deposited by filtered cathodic vacuum arc (FCVA) were subjected to rapid thermal annealing (RTA). Cross-sectional transmission electron microscopy (TEM) and electron energy loss spectroscopy (EELS) were used to study the structural stability of the films. While RTA increased the thickness of the intermixing layer and decreased the sp3 content of the a-C:H films, it did not affect the thickness or the sp3 content of the a-C films. The superior structural stability of the FCVA a-C films compared with PECVD a-C:H films, demonstrated by the TEM and EELS results of this study, illustrates the high potential of these films as protective overcoats in applications where rapid heating is critical to the device functionality and performance, such as heat-assisted magnetic recording.

Friction Durability of Extremely Thin Diamond-Like Carbon Films at High Temperature.

To clarify the friction durability, both during and after the high-temperature heating of nanometer-thick diamond-like carbon (DLC) films, deposited using filtered cathodic vacuum arc (FCVA) and plasma chemical vapor deposition (P-CVD) methods, the dependence of the friction coefficient on the load and sliding cycles of the DLC films, were evaluated. Cluster-I consisted of a low friction area in which the DLC film was effective, while cluster-II consisted of a high friction area in which the lubricating effect of the DLC film was lost. The friction durability of the films was evaluated by statistical cluster analysis. Extremely thin FCVA-DLC films exhibited an excellent wear resistance at room temperature, but their friction durability was decreased at high temperatures. In contrast, the durability of the P-CVD-DLC films was increased at high temperatures when compared with that observed at room temperature. This inverse dependence on temperature corresponded to the nano-friction results obtained by atomic force microscopy. The decrease in the friction durability of the FCVA-DLC films at high temperatures, was caused by a complex effect of temperature and friction. The tribochemical reaction produced by the P-CVD-DLC films reduced their friction coefficient, increasing their durability at high temperatures.

Surface characterisation of Ga+ ion implanted ta-C thin films

Samples of thin film (d∼40nm) tetrahedral amorphous carbon (ta-C), deposited by filtered cathodic vacuum arc (FCVA), have been implanted with Ga+ at ion energy E = 20 keV and ion doses D=3.1014÷3.1015 cm-2. The induced structural modification of the implanted material results in a considerable change of its optical properties, best manifested by a significant shift of the optical absorption edge to lower photon energies. This shift is accompanied by a considerable increase of the absorption coefficient (photo-darkening effect) in the measured photon energy range (0.5÷3.0 eV). These effects could be attributed both to additional defect introduction and increased graphitization, as well as due to Ga colloids formation, as confirmed by electron microscopy analysis. Further nano-scale structural and electronic properties characterisation of the Ga+ implanted films has been carried out here using conductive atomic force microscopy (C-AFM) measurements. The observed properties modification results from the high concentration of introduced Ga+ atoms, which is of the order of those for the host element. The obtained optical contrast (between implanted and unimplanted film material) could be made use of in the area of high-density optical data storage by using focused Ga+ ion beams.

The effect of substrate bias voltage on the adhesion strength of ta-C coated tools prepare by filtered cathode vacuum arc

ta-C coating have found application for cutting tools. In this study, the effect of bias voltage on the physical properties of the coating and cutting performance were experimentally investigated. A bias voltages were applied with 0, 75, 150, 300 V and thicknesses were 430 nm. The results showed that the regardless of the bias voltage, the adhesion strength indicates that all ta-C coatings were HF 1. However, increasing bias voltage will increase the C = C boning at the coating, especially 150 and 300 V. Moreover, hardness values also decreased with increased bias voltage. For the cutting test, the ta-C coating from the lowest I(D)/I(G) value (0.5) with 75 V is selected. After cutting test, the adhesive of Al debris and delamination on the ta-C coated surface was three times lower than commercial DLC. This phenomenon shows that heat resistance of ta-C coating is dominant with high portion of sp3 fraction.

The effect of substrate bias voltage on the adhesion strength of ta-C coated tools prepare by filtered cathode vacuum arc

The effect of substrate bias voltage on the adhesion strength of ta-C coated tools prepare by filtered cathode vacuum arc