ICMCTF2011 Session BP: Symposium B Poster Session

In vacuum vapor deposition techniques such as physical vapor deposition (PVD) and chemical vapor deposition (CVD), the film properties are strongly depending on the process conditions. It is customary and is considered to be reasonable that the deposition system be controlled by the ordered sequence with pre-determined parameters. The process conditions were fixed by the operator and the values are determined prior to deposition. After the coating, the film properties are evaluated and then the process conditions are changed to obtain optimum film properties. Generally, this optimization process is troublesome and it takes much time to have optimum process conditions, especially for complex films having multilayer or multistep structures with so many parameter values.

In this study, it has been tried to predict and obtain best coating quality by a numerical model. The model was based on the data obtained from the experimental values and interpolation and/or extrapolation method was employed. The synchronization of the system, i.e., the unification of the difference between one system and the other was fulfilled on a trial basis by diagnostic equipments such as Langmuir probe and/or Optical Emission Spectroscopy (OES).

The first preliminary trial was manifested with TiN coating on the stainless steel plate. The brightness was measured with two variables of nitrogen flow rate and substrate temperature. The numerical equation was derived from the measured data according to the variation of the two variables. The interpolation method was used to obtain the best curve fitted to derive the numerical equation. With this equation the system was operated by inputting the user-defined brightness value. The hit rate which signifies the accuracy of brightness prediction turned out to be more than 70%.

The effect of laser annealing on the crystal structure of alumina thin films has been investigated. The crystal structure of the films is basically determined by the deposition conditions during the process. Gibbs free energy stored in the various films is changed with an external thermal deposition. The thermal deposition is established using a cw Ar ion laser system. Within certain thermal limits, an exothermic process in the crystal planes is activated leading to partial release of the internal energy in the fabricated films. The crystal structure of the processed films is “healed” to the minimum energy status which will lead to the alpha phase. Three sets of alumina thin films have been prepared for this study using an inverted cylindrical magnetron sputtering system with an unbalanced magnetic field. All sets were laser annealed at different energy densities and annealing times. The crystal structure before and after annealing is investigated and the stoichiometry of the fabricated films are reported.

In a thermodynamically favored process, TiSiN ternary system segregates into the two binary compounds which are usually formed by nanocrystalline TiN embedded in a matrix of amorphous SiN_x. The influence of the Si content in the coatings on the

mechanical properties and tribological behaviors of the TiSiN coatings were systematically studied by several researches. Nanoindentation result shows that the hardness and Young's modulus of the TiSiN coatings increase with increasing Si content in the coatings. TiSiN coatings exhibit an increase in the friction coefficient with an increasing Si content in the coatings.

The advantage of TiSiN coating is feasible for machining applications owing to its dense, highly adhesive, high hardness properties. However, TiSiN coating, in general, shows poorer performance than TiN in the case of low sliding speed or interrupted cutting process due to its brittleness and high friction coefficient. Previous study shows that TiSiN/TiAlN were dependent on lamellae thicknesses in film structure, resulting in improved mechanical, wear and corrosion properties. The similar study presented that the mechanical and tribological property can be improved by the design of multilayered TiSiN/CrN coating. It showed the multilayered TiSiN/CrN coating possessed excellent resistance to plastic deformation as compared with the monolayered TiSiN. However, the effect of the deposition parameters on the properties of TiSiN/CrN coating was not studied in combination of bias voltage and multilayer structure.

In this study, a monolayered TiSiN and a multilayered TiSiN/CrN coatings deposited with different bias voltages were synthesized by a cathodic arc deposition process. TiSi (80/20 at.%) and chromium targets were used for the deposition of TiSiN and multilayered TiSiN/CrN coatings. The performance of the coating was evaluated by microstructure, ball-on-disc wear test and corrosion test.

Industrial application of carbon-based coatings has been paid attention owing to their excellent mechanical properties, such as high hardness, elastic module and low friction coefficient. In recent, exciting ongoing researches try to deposit carbon-based protective film on automobile engine parts, tools and molds taking into account not only high hardness, but also solid lubricating properties. On the other hand, it is well known that carbon-based coatings have a low adhesion to metal surface due to their high internal stress. It is a big problem to apply on automobile, tool and mold industrials. It is also difficult to increase a film thickness.

In this study, carbon-based coatings were prepared on injection mold steel and silicon wafer by plasma chemical vapor deposition after plasma nitriding in the same chamber as continues process. Plasma nitriding process was performed under 0.1 torr of pressure using N₂ and H₂ gases with a pulsed DC bias voltage of -400V at 400°C for 3 hours. Carbon-based coatings were fabricated under pressure of 0.05 and 0.1 torr with CH₄ gas, temperature of room temperature, 100°C and 150°C, and bias voltage of - 400V, -500V and -700V, respectively. In case of nitriding and PCVD hybrid process, the temperature of chamber was controlled to test condition after plasma nitriding process. Hardness was evaluated by nanoindentation and low load vickers hardness tests. Friction coefficients against a SUJ2 (JIS) steel ball were measured by tribometer (ball-on-disk) with load of 5 N under humidity of 56 to 76%. Chemical bonding states were investigated by X-ray photoelectron spectroscopy and Raman spectrometry. Surface morphology was observed by atomic force microscopy.

Several types of samples were prepared. The sample (#1) of plasma nitriding without carbon coating is showed above two times higher hardness than the sample without substrate (KP4). Hardness for the sample(#2) prepared by PCVD carbon coating shows 1224 Hv. The sample(#3) prepared by nitriding and PCVD hybrid process with carbon coating shows lower hardness than that of #2. It is considered that hardness is affected the nitrided substrate owing to overly thin film thickness. Friction coefficient of samples showed about 0.4 for sample #1, 0.3 for sample #2, 0.15 for sample #3. Friction coefficient for sample #2 shows the lowest in initial stage, but it is gradually increased to 0.3, and then stabilized to the end of the test. It is considered that coating delamination occured from substrate. This study will be discussed on the properties of carbon-based coatings injection mold steel prepared by hybrid process, and designing layers and complex materials.

The effect of argon bombardment in tetrahedral amorphous carbon (ta-C) deposited by the filtered cathodic vacuum arc (FCVA) technique is investigated. The films were prepared with 5 ms current pulses of 190 A at a frequency of 3 Hz. The deposition substrate was polarized in the 0 to - 500 V bias voltage range. The density of the films, also determined by RBS, was in the 2.5 to 3.0 g/cm³ range, depending on the substrate bias voltage. The stress of the films (up to about 10 GPa) was determined by the bending beam technique. Nanohardness measurements were performed indicating that the films prepared in the 100-200 bias voltage is about 50 GPa. Argon gas was incorporated in a series of films using an ion gun source to simultaneously bombard the films with a beam of argon ion with energy in the 0-180 eV range. Argon concentration in the films was determined by RBS measurements. A study of argon effusion, realized from room temperature up to 1000 ^oC, shows that the structure of the films depends on the bombardment energy of the argon ions. It was observed that the stress reduces significantly as a function of the effusion temperature. Raman measurements were used to investigate the structure of the films as a function of the bias voltage and annealing temperature.

V-Al-C thin films were deposited on Al₂O₃ (11-20) substrate at 500°C by DC magnetron sputtering using a hot-sintered multi-component target with 2:1:1 MAX phase-like composition. TEM and XRD data suggest that hexagonal Al-containing vanadium carbide solid solution was formed. The films exhibited a strong basal plane texture. The lattice parameter of the hexagonal solid solution was dependent on annealing time and temperature: the c lattice parameter of V₂(Al)C decreased by 3.5 % after annealing for 1 hour at 750°C as compared to the as deposited film. Meanwhile, the formation of V₂AlC MAX phase was observed at 650°C and a phase-pure V₂AlC thin film was obtained at 850°C. Previously, the formation of phase-pure V₂AlC thin films was reported at 750°C, suggesting that surface diffusion is affecting the structure evolution of V₂AlC thin films at low substrate temperatures.

Hard nitride coatings of the group VIB transition metals are increasingly used in a wide range of tribological applications to improve performance and to extend the life of metal cutting, drilling, and forming tools, as well as bearings and various machine parts. Among the nitrides of group VIB elements, binary CrN and MoN have been well studied. CrN has excellent corrosion resistance under severe environment conditions, superior oxidation resistance, and good wear resistance; MoN has been found to have many unique physical and mechanical properties such as high hardness, low solubility in non-ferrous alloys and low friction, etc. As a result, ternary Cr-Mo-N coatings could have superior properties tailored through appropriate combinations of CrN and MoN.

We have prepared ternary Cr-Mo-N coatings with different compositions on Si wafers by using a dual rf-magnetron sputtering system with Cr and Mo targets and nitrogen as reactive gas. The metal target bias voltages were varied from -500 V to -900 V which allowed to preparing the ternary layers with Cr/Mo ratios in the range from 1/3 to 3/1. Binary CrN and MoN coatings were also prepared under similar conditions for comparison. The resulting coatings had up to 1.8 micron thickness and were well adherent to the substrate. The hardness, surface morphology, microstructure, and composition were studied by nanoindentation, SEM, AFM, XRD, and XPS, respectively. All coatings were smooth and nanocrystalline with mean grain size 15-20 nm and showed single XRD-observable phase with the characteristic XRD peaks varying between those of CrN and MoN depending on the composition. The hardness and Young’s modulus were found in the range of 9.0 - 16 GPa and 120 - 215 GPa, respectively, with larger values observed for Mo-richer layers. To investigate the effect of thermal treatment on the microstructure and mechanical properties, the samples were annealed in air at temperatures up to 700 °C for 1 hour. The thermal stability of the coatings was found to increase with a larger amount of Cr in the ternary system. The MoN coating was completely oxidized after annealing in air at 600 °C for one hour, whereas the ternary Cr-Mo-N coatings with Cr content more than 75 at.% survived under up to 700 °C without cracking or delamination. The final result of the annealing was Cr₂O₃ as main crystalline phase. However, the hardness was increased at intermediate annealing temperatures while the coatings maintained their initial structure.

This work has been supported by the U.S. National Science Foundation Grant #DMR-0806521 and the Regional Council of Burgundy, France.

In the field of hard coatings, oxidation resistance and high hardness of the coatings are among the main concerns. Incorporation of yttrium into ceramics has become an attractive method to impart improved mechanical and chemical properties to the ceramics. Multilayered structure of the coatings has also attracted much attention as an effective approach to obtaining improved properties. We have reported superior oxidation resistance of (Cr,Al,Y)N compared to (Cr,Al)N and improved mechanical and chemical properties of (Ti,Al,Si)N/(Cr,Al)N multilayered films.

In this study, we synthesized nano-multilayered (Ti,Al,Si)N/(Cr,Al,Y)N films and investigated their oxidation resistance and microhardness. The films were deposited on Si or WC-Co substrates by cathodic arc ion plating (AIP) method using TiAlSi and CrAlY alloy targets. The two nitrides, (Ti,Al,Si)N and (Cr,Al,Y)N, were deposited alternately on the substrates and the multilayer period was controlled by varying the rotation speed of the substrates from 2.5 to 5.0 rpm. Microstructure of the films was investigated under scanning electron microscope (SEM) and transmission electron microscope (TEM). The microhardness was measured using a conventional micro-Vickers hardness tester. For the evaluation of the oxidation resistance, X-ray diffraction (XRD) and glow discharge optical emission spectrometry (GDOES) were performed to identify oxide layers of the films before and after annealing at 900ºC and 1000ºC for 1 hour.

MAX phases received great interest the last years due to a combination of metallic and ceramic properties: they are very good thermal and electrical conductors and are easily machinable. They exhibit a great interest for electrical contacts and also for machining tools.

Compared to PVD techniques (such as magneton sputtering or PLD) which are largely adopted for MAX phases thin films deposition, it seems to be more difficult to obtain single –phase Ti₃SiC₂ by CVD techniques. Few studies on the direct deposition of Ti₃SiC₂ coating by CVD using TiCl₄ –SiCl₄-CCl₄ (or CH₄)-H₂ system are reported. Ti₃SiC₂/SiC multi layer coatings were fabricated by reactive CVD (RVCD) using the reaction between a gas mixture (TiCl₄/H₂) and solid SiC.

In this paper we present the first study on the fabrication of the Ti₃SiC₂ MAX phase coatings by High Temperature Chemical Vapor Deposition (HTCVD). Experiments have been conducted (using Methylchlorosilane (MTCS) and Titanium Tetrachloride (TiCl₄) as reactants (with hydrogen as carrier gas) from 1200°C to 1350°C, with different values of TiCl₄ to MTCS ratio and of the dilution coefficient α = Q(H₂)/(Q(MTCS) + Q(TiCl₄)

Thermodynamic calculations performed on this system in the temperature range are compared to the experimental results.

The composition of the deposited films was analysed using X-ray diffraction technique and WDS (Castaing microprobe). SEM (Scanning Electron Microscopy) and TEM (Transmission Electron Microscopy) were used to observe the coatings microstructure. It was found that nearly pure Ti₃SiC₂ was deposited at 1300°C with a high dilution coefficient of the reactants in hydrogen.

The preferred orientation (texture) and magnetic properties of electrodeposited FePd films were investigated using electron back-scatter diffraction (EBSD) and vibrating sample magnetometer (VSM). Fe-Pd films were electrodeposited on brass and Cu (001) substrates using an alkaline electrolyte which was composed of Fe sulfate, Pd chloride and 5-sulfosalicylic acid and ammonium sulfate. The potential for the electrodeposition process was varied from -0.9V to -1.1V. The chemical compositions of the deposited films were analyzed using EDS, and the crystallographic structures of deposited films were characterized using XRD, TEM and EBSD.

In this paper, we present the results from a study in which Ta was sputter deposited on the inner surface of tubes of carbon steels using various cylindrical magnetron sputtering processes. The inner surface of cylinders often requires protection from erosion and corrosion from high temperature chemicals. Currently electroplated Cr is applied for protection. To reduce and eventually eliminate electroplating for this application, cylindrical magnetron sputtering (CMS) driven by a DC power supply has been pursued for a number of years. Pulsed DC power supplies that promise to deliver extremely high peak power have been used in conventional planar magnetron sputtering, and the resultant films are proven to be significantly better in microstructural characteristics and tribological performance than those produced using standard DC power supply. In the current study, three sputtering methods were used to deposit Ta on the inner surface of cylinders (100 mm in diameter by 300 mm long) made of carbon steels 1018 and A723. These three sputtering methods include DC magnetron sputtering (DCMS), high power impulse magnetron sputtering (HIPIMS) and modulated pulsed power magnetrons sputtering (MPPMS). Carbon steel 1018 was used for the initial study; then thick Ta coatings were deposited on A723 steel. After the deposition, SEM, XRD, AFM, microhardness, Rc indentation, and scratch test were performed to understand the coating microstructure including the phase formation and transformation, and mechanical properties including the coating adhesion and internal stress. It has been observed that all coatings produced by these three techniques are dense with fairly good adhesion. The coating internal stress is similar for both DCMS and HIPIMS and increases with the coating thickness. Under the same average power, the HIPIMS process resulted in a similar deposition rate as the DCMS, in contradiction with the results obtained in the planar magnetron sputtering. This paper will present the detailed microstructural and mechanical characterization results.

Ru/TiN_xO_y/Ru structures were prepared by dc magnetron sputtering. The resistive switching characteristics of Ru/TiN_xO_y/Ru structures were investigated as a function of nitrogen partial pressure during TiN_xO_y deposition. Reproducible resistive switching characteristics were observed in TiN_xO_y thin films deposited at N₂/O₂ ratios of 2.0, 2.5, and 3.0. The conduction mechanisms in high and low resistance states are dominated by space-charge-limited conduction and ohmic behavior respectively, which suggests that resistive switching behaviors in such structures are related to filament formation and rupture. It is also found that the reset current decreased as nitrogen partial pressure increased, due to the variation of oxygen vacancy concentration in the TiN_xO_y thin films.

This study utilized two surface techniques consisting of electroless nickel (EN) and arc ion plating (AIP) to treat the ductile iron substrates. That is, EN was first used as an interlayer, and then TiAlZrN film was coated on superficial by using the AIP method. Coating morphology, structure, and adhesion were analyzed, as well as polarization and immersion tests were also performed for understanding the effect of the duplex coatings on corrosion behavior of ductile iron. The results showed that EN is an amorphous structure, while the TiAlZrN film is a multilayer type. Ductile iron after the monolithic EN or TiAlZrN coating has better corrosion resistance as compared with uncoated one. In particular, a combination of EN/TiAlZrN duplex coatings not only increases the adhesion, but also evidently improves the corrosion resistance of ductile iron in 3.5 wt% NaCl and 10 vol.% H₂SO₄, respectively.

Since several years CFRPs are getting more and more important as construction material in the aircraft industry. Their unique combination of light weight and high performance predestine these materials for airplanes of the newest generation and open up new perspectives in various other applications. One of the dominating problems in all these applications is the machining of the extreme abrasive CFRP materials, where diamond coatings demonstrated already their suitability for an economic and reliable production process. For mastering the future machining of the ongoing material improvement, the CemeCon AG developed new multilayer diamond coatings on cemented carbide tools, which combine the excellent performance and fracture toughness of micro-crystalline diamond films and the smooth component part surface, achieved by nano-crystalline, smooth diamond films. On the one hand these multilayer diamond films already proofed their excellent performance in the machining of CFRPs and are commonly used in the run production process. On the other hand they are under continuous further development for future challenges in working with CFRPs. Various results of the multilayer diamond films in the development and in the run production will be presented and compared to other coatings and uncoated tools.

The Ti­-Si-N system is attractive for its superhardening, for use as e.g. coatings on cutting tools. The increased hardness upon Si addition to TiN has qualitatively been ascribed to the nanometer dimension of the TiN grains together with the prevention of grain boundary sliding by the so called SiN_x tissue phase. However, a quantitative understanding of the hardness enhancement is still not present. The structure of the tissue phase is an important issue and is discussed in the literature.

We study the dynamical and thermodynamic stability of a single monolayer of SiN_x embedded isostructurally between B1­TiN (001) and (111) oriented slabs. Phonon calculations show that upon distortion of the Si­N bond the (001) interface is almost stabilized dynamically while the (111) interface is dynamically stable. Moreover, the stoichiometric degree of freedom was relaxed by allowing for Si vacancies in the lattice. Calculations show that the ideal 1:1 SiN stoichiometry in both interfaces are thermodynamically unstable with respect to Si vacancy formation. Thus, the real structure of TiN/SiN_x should have another stoichiometry than the ideal B1 interfaces.

Cu-Ag thin films are known to have better mechanical and electrical properties than Cu or Ag alone. In this study, Cu-Ag thin films with various compositions were prepared using co-sputtering technique followed by rapid thermal annealing at various temperatures. The films’ mechanical and electrical properties were then characterized using XRD, AFM, FESEM, and TEM, as functions of compositions and annealing conditions. The results show that the as-deposited films would transform from one-phase structures to two-phase ones without annealing. The hardness would reach the maximum and 50/50 alloy compositions, and the resistivity would follow Nordheim’s rule prior to the formation of separated phases. After being annealed, the films’ resistivity would follow the mixture rule roughly, mainly due to the formation of Ag-rich and Cu-rich phases. The surface morphology and structure would vary as a function of annealing temperature. From the results, it is found that grain growth varied depending on Ag-Cu compositions.

Niobium and vanadium carbide coatings provide a surface modification layer on steel surface with high hardness and adequate wear resistance. In this study, AISI H11 tool steel was immersed in a molten bath consisting of borax, boric acid, and ferro-niobium and ferro-vanadium to form a carbide coating mixture on the surface.

Surface and cross-sectional morphologies of carbide layers were studied with a scanning electron microscope (SEM) and Energy dispersive spectrometer (EDS). The hardness and elastic modulus of carbide layer was evaluated by nanoindentation. The wear resistance of steels was investigated by pin-on-disk wear tests. Daimler-Benz Rockwell-C adhesion and scratch tests were further conducted to explore the adhesion properties of carbide layers. Carbide layer around 10 um thick with an outer V₈C₇ and inner (Nb)₆C₅ phases were observed. The adhesion strength quality of carbide layers was related to HF1 indicating good adhesion properties. It is concluded that the hardness and tribological properties of AISI H11 tool steel were improved effectively by the vanadium and niobium carbide coating.

The industries of microelectronic devices have been searching for materials capable to operate at aggressive environment. For this, the SiC thin films is a great candidate for this application due some properties as, for example, high operate temperature, good thermal conductivity and high breakdown electric field. However, to improve the electric conductivity is necessary to add nitrogen to the film.

Studies about the effect of nitrogen content in SiC_xN_y thin films deposited by magnetron co-sputtering technique without substrate heating are presented. This consists of two magnetrons targets arranged in parallel and angled at approximately 20º of the central axis. The magnetron targets are made of 100 mm diameter and 90 W, respectively. The working pressure was fixed at 5 mTorr and the N₂/Ar flow ratio was adjusted by varying the N₂ flow rate and maintaining the Ar flow rate at 10 sccm. Moreover, SiC_xN_y films were deposited on p-type (100) silicon substrate that was placed at a substrate-to-target distance of 160 mm. Fourier Transformed Infra Red (FTIR), Composition, chemical bonds and thickness of as-deposited Si_xC_y films were investigated by Rutherford Back Scattering (RBS), Raman spectroscopy and profilometry, respectively. The RBS results indicate that the condition of applied power in magnetron targets allows obtaining approximately stoichiometric SiC films at pure Ar plasma. With the addition of N₂ in plasma, the carbon concentration increases for N₂ flow > 5 sccm due to the effect of chemical sputtering of carbon target by N₂ gas. Raman spectra clearly reveal that the deposited SiC_xN_y films are amorphous and exhibited C-C bonds corresponding to D and G bands.

In this work, the p-type zinc oxinitride films were fabricated by thermal annealing in air ambience. The Zinc nitride films were deposited onto glass substrate in N₂–Ar mixtures by reactive RF magnetron sputtering. The as-grown zinc nitride thin film is a n-type material. It is found that the film treated at 300^oC for 3 hours can be changed to a p-type material. The zinc oxinitride films reveal a very low resistance (2.2×10^-2 Ω-cm) and high carrier concentration (3.88×10¹⁹ cm^-3) after the heat treatment. The optical band gap of zinc nitride was determined as a direct band gap varying from 1.1 eV to 1.6 eV according to the temperature of heat treatment. The zinc oxinitride can be prepared with various electrical characteristics and the band gaps modulation by controlling the temperature of heat treatment.

As par survey, we have not found any literature reporting on tungsten zirconium nitride (W-Zr-N) nano-ceramic coating so far. Thus W-Zr-N coating represent a new class of materials which exhibit improved mechanical properties including high hardness and high fracture toughness.

In this study, the nanocrystalline TiZrN thin films were deposited on Si(100) wafer and AISI 304 stainless steel substrate respectively using unbalanced magnetron sputtering. Specimens were later annealed in flowing nitrogen at different temperature ranging from 500°C to 1100°C for two hours. The process of heat treatment affected its microstructure and properties. The texture of the TiZrN films was characterized by X-ray diffraction (XRD); grain sizes were both calculated according to the result of θ/2θ scans. The FWHMs of specimens are decreased with increased temperature. The thickness of the TiZrN thin films was further observed and measured using field-emission gun scanning electron microscope (FE-SEM), measuring about 500 nm. The composition and packing factor of the TiZrN thin films were determined by the Rutherford Backscattering Spectroscopy (RBS). The hardness of the TiZrN films was measured using nanoindenter, which was then observed obviously varying with annealing temperature. The compositional depth profiles were characterized using Auger electron spectroscopy (AES). The electrical resistivity of the TiZrN films was measured using a four-point probe. The corrosion resistance of the TiZrN thin films was obtained from potentiodynamic scanning conducted from -600 to 800 mV in 5%NaCl and 1M H2SO4 + 0.05M KSCN solutions respectively.

Silicon carbide layers were grown on a Si substrate by liquid phase epitaxy assisted chemical vapor deposition (LPECVD) at a temperature below 1100^oC and pressure of 1 atmosphere without SiC seeding. The liquid phase epitaxy assisted chemical vapor deposition was carried out in a tube furnace through cyclic heating process using methane as a carbon source and Sm-Co mixed powder as a solvent for carbon and silicon. The growth of SiC from rare earth Sm-based solvent is an innovative approach, and Co can promote the formation of solvent during the process. X-ray diffraction (XRD), micro-Raman spectroscopy, Electron probe micro-analyzer (EPMA), Scanning electron microscopy (SEM) and Transmission electron microscopy (TEM) were used to characterize the properties of SiC. The growth mechanism of SiC deposited by LPECVD was also discussed in this study. Results indicated that β-SiC was successfully fabricated on (111) Si substrate without SiC seeding by LPECVD. The heterogeneous nucleation of β-SiC was found to be observed initially at the edge of triangle-shaped sites on (111) Si surface, which was formed due to the existence of Co, and then grew and expanded to form β-SiC film.

Recently we reported on a novel form of hard graphite-like hydrogenated amorphous carbon deposited by an expanding thermal remote plasma in an Ar – C₂H₂ environment [1, 2]. The graphite-like films deposited on Si and steel substrates are dense (~2.0 g/cm³) and very smooth, with RMS roughness below 4 nm for film thicknesses above 1µm, which makes them ideal candidates for tribological applications.

However, dense a-C:H material commonly leads to high compressive stress, which in turn causes poor adhesion on metallic substrates. The influence of a Ti metallic interlayer in between M2 steel substrates and the hard graphite-like films is investigated by monitoring adhesion with the Rockwell C test and the scratch test as a function of carbon film thickness, interlayer thickness and deposition temperature. It is shown that a sputtered Ti interlayer deposited at substrate temperatures of 200 – 250°C and with an adjusted thickness dependant on the carbon film thickness improves the adhesion drastically. This can be explained by a more densely packed film structure at higher temperatures and by a roughening effect of the top Ti surface with increasing thickness, due to grain coarsening. The wear rates of the a-C:H/Ti/M2 steel stack against a 100Cr6 ball counterpart in a ball-on-disk test were found to be very competitive, in the order of 2.5 × 10^-17 m³/Nm.

[1] S.V. Singh et al., Appl. Phys. Lett. 92 (2008) 221502.

[2] S.V. Singh et al., J. Appl. Phys. 107 (2010) 013305.

TaN-(soft metal) nanocomposite thin films have been shown to have good mechanical properties. This study aims at comparing the antimicrobial behaviors of TaN–Cu, TaN-Ag, and TaN-(Ag,Cu) nanocomposite films. These films were deposited by reactive co-sputtering on Si. They were then annealed using RTA (Rapid Thermal Annealing) at 400°C to induce the nucleation and growth of metal particles in TaN matrix and on film surface. After being characterized using XRD, FESEM, and TEM, the samples were tested for their anti-bacterial behaviors against Gram-negative and Gram-positive bacteria. It is found that TaN-Ag is more effective against E. Coli (Gram-negative), while Cu ion or TaN-Cu is more effective against Staphylococcus aureus (Gram-positive). For TaN-(Ag,Cu), a synergistic effect is observed. This film is effective against both types of bacteria. The wider application is expected.