High Target Utilisation Sputtering Research Articles

Exceptional Performance of Room Temperature Sputtered Flexible Thermoelectric Thin Film Using High Target Utilisation Sputtering Technique

AbstractThe High Target Utilisation Sputtering technique (HiTUS) is of interest for industrial processes, including in roll‐to‐roll manufacturing. This study marks the first application of HiTUS to thermoelectric materials, exemplified by bismuth telluride. The HiTUS technique separates the sputtering power into the plasma power and the target power, with additional kinetic energy in the sputtering particles from the applied electrical field, thus enabling a much wider sputter parameter space to modify the film performance. This study investigates how plasma power, target power, and substrate bias in HiTUS intricately influence crystal orientation/size, elemental composition, surface morphology, and other film properties. These factors subsequently affect carrier density/mobility, and consequently the thermoelectric performance of the bismuth telluride film. These deposited films reach a power factor of 6.5 × 10−4 W m−1 K−2 with a figure of merit ≈0.14 at room temperature, the highest value for room‐temperature sputtered un‐doped bismuth telluride. Subsequent post‐deposition annealing significantly enhances the crystallinity of the film (highly polycrystalline), further improving the power factor to 23.5 × 10−4 W m−1 K‐2, with a figure of merit ≈0.45 at room temperature. The excellent performance of the HiTUS fabricated thermoelectric film opens opportunities for the large‐area manufacture of thin‐film thermoelectric materials and devices.

Structure, mechanical and tribological properties of Ta-xN coatings deposited by reactive HiTUS

This work investigates the structure, mechanical, and tribological properties of Ta-xN coatings deposited using reactive High Target Utilization Sputtering (HiTUS) with a focus on the role of tribological layers formed in the sliding contacts. The scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, and Raman spectroscopy observations revealed that the gradual increase of nitrogen flow results in the transition from textured fcc Ta structure (without nitrogen) toward mixed sub-stoichiometric Ta-Ny/Ta2N/amorphous structures up to near-stoichiometric fcc TaN coatings. The highest hardness HIT ∼37 GPa and indentation modulus EIT ∼375 GPa as well as the lowest coefficients of friction (COF) in the range 0.16–0.36 and wear rates around 3 × 10−7 mm2/N·m were obtained in the layer with Ta2N structure. The unique combination of low COF and high wear resistance combined with high hardness and stiffness were attributed to the shear sliding between Ta2O5-based transfer film in the wear track and pure alumina ball.

Structural and mechanical properties of multi-component TiVTaNbZrHf and (TiVTaNbZrHf)N coatings for biomedical applications

Multicomponent TiVTaNbZrHf alloy and (TiVTaNbZrHf)N coatings were deposited on Ti6Al4V alloy by High Target Utilization Sputtering. Sputtering was carried out by reactive sputtering from a TiVTaNbZrHf target with a different nitrogen addition. The microstructures, mechanical properties, and cytotoxicity tests were studied. It was found that the (TiVTaNbZrHf)N coatings showed a dense columnar structure with a face-centered-cubic solid solution phase. The (ZrTaNbVHfTi)N with 4 sccm nitrogen addition exhibited the highest hardness of 34 ± 0.33 GPa and high Indentation modulus of 408.47 ± 24.97 GPa. The mechanical properties greatly depended on the amount of added nitrogen in reactive plasma Physical vapor deposition sputtering. Cytotoxicity tests proved that a very high percentage of live cells were observed after 7 days of incubation time on (TiVTaNbZrHf)N coating.

Reactive HiTUS TiNbVTaZrHf-Nx Coatings: Structure, Composition and Mechanical Properties.

High entropy metal sub-lattice stabilized nitride coatings based on multicomponent refractory transition metals (TM = Ti, Nb, V, Ta, Zr, Hf) are promising candidates for extreme conditions due to their high thermal, mechanical, and corrosion properties. The aims of the current work included the investigations of the possibilities of the novel High Target Utilization Sputtering (HiTUS) technique applied to reactive sputtering of TiNbVTaZrHf-xN coatings from the viewpoints of hysteresis behavior during reactive sputtering as well as the structure, composition, stoichiometry, and mechanical properties of the resulting coatings. With increasing nitrogen content, coating structures varied from amorphous in metallic alloy coatings to textured nano-columnar fcc structures. Despite certain deviations of TM from equiatomic concentrations, homogeneous solid solutions corresponding to single-phase multicomponent nitride analogous to high entropy stabilized compounds were obtained. Mechanical properties were found to be proportional to nitrogen content. The highest hardness HIT ~ 33 GPa and indentation modulus EIT ~ 400 GPa were found in a slightly sub-stoichiometric (~42 at% nitrogen) composition. HIT/EIT and limited pillar split measurements suggested that these coatings exhibit low fracture toughness (around 1 MPa.m1/2). The work confirmed that reactive HiTUS is suitable for the preparation of multicomponent nitrides with the control of their stoichiometry and mechanical properties only via nitrogen additions.

Structure and chemical composition of thin-film nanocomposites based on silver in organosilicon amorphous matrix prepared by High Target Utilization Sputtering

Thin films based on Ag nanoclusters embedded in an organosilicon polymer matrix were deposited using the High Target Utilization Sputtering technique (HiTUS) by simultaneous sputtering of the Ag target and polymerization of hexamethyldisiloxane (HMDSO) vapors in radiofrequency plasma. The influence of deposition parameters on chemical composition and structure of the deposited nanocomposite films was studied using scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy, and X-ray diffraction analytical techniques. The films under investigation exhibit a dense uniform structure with the metallic nanocrystalline silver present in the form of spherical-shaped nanoclusters with dimensions below 10 nm embedded in an amorphous organosilicon plasma polymer. The average size of Ag nanoclusters is increased from 1.8 to 4.4 nm with Ag content increasing from 16 to 57%at. while concentration of nanoclusters is reduced. Incorporation of the metallic silver into the plasma polymerized HMDSO leads to a decrease of carbon and oxygen content as well as a decrease of organosilicon polymer matrix density.

Micromechanical Properties of Reactive HiTUS TiNbVTaZrHf–N Coatings on Different Substrates

Abstract High entropy ceramic coatings, including multicomponent transition metal nitrides called also high entropy nitrides (HEN), are usually deposited using reactive arc and/or DC magnetron (co)sputtering. High Target Utilization Sputtering (HiTUS) was not applied in HEN systems up to now. Subsequently, the mechanical properties of HEN coatings prepared by HiTUS are also not known. The transition metals from the 4th and 5th group of the periodic table (Ti, Zr, Hf, Nb, V, and Ta) are strong nitride formers which would be the most suitable for HEN coating systems and therefore, investigation of their properties would be of significant interest. However, the nanoindentation measurements on thin coatings always produce „composite“ values involving the contribution from the substrate. The separation of the coating properties from composite values requires upgraded analytical approaches different from standard Oliver & Pharr analysis. Thus, the aim work is to investigate the structure, hardness, and elastic modulus of TiZrHfNbVTa–xN coatings with different nitrogen stoichiometry deposited by reactive HiTUS using both CSM for bulk and CSM for thin films methods and to compare the results obtained on 4 different substrates (Si wafer, sapphire, 100Cr6 steel, and Ti6Al4V alloy). The subsequent results showed systematic differences in the calculated mechanical properties depending on the substrate properties both in CSM and CSMTF modes. Stiffer substrates always resulted in the overestimations of the calculated hardness and indentation modulus compared to softer substrates with lower Young’s modulus and the differences were in the range of around 10 %. Obviously, better theoretical models for the calculations of true coating properties are required.

Energy level matching between transparent conducting electrodes and the electronic transport layer to enhance performance of all-inorganic CsPbBr3 solar cells

Perovskite solar cells (PSCs) have become a promising research direction in photovoltaic field, where the evolution of the transparent conductive oxides (TCOs) electrodes, a vital part of photovoltaic devices, has played a distinctive role in their development. To date, the indium tin oxide (ITO) and fluorine-doped tin oxide (FTO) have been widely used as TCOs in state-of-the-art PSCs. However, the energy level matching between the TCO electrodes and the electron transport layers (ETLs) are usually ignored. Herein, Ta doped SnO2 (TTO) films have been prepared by the high target utilisation sputtering (HiTUS) technology, which exhibited the lowest resistivity of 7.8 × 10−4 Ω cm and the average transmittance in the visible light region over 85%. A maximum power conversion efficiency (PCE) with 6.48% was achieved when the TTO films as the bottom electrodes in CsPbBr3 PSCs, higher than that of PSCs based on FTO (5.36%). Especially, the open-circuit voltage (Voc), short-circuit current (Jsc) and fill factor (FF) were all enhanced, which were attributed to the suitable energy level matching between the TCOs and ETLs layers and their low interface roughness. This work demonstrates the band structure of the TCOs and ETL layers and the roughness of TCOs have more important influence on the PCE of PSCs under the similar optical and electrical properties of TCOs condition.

Significant performance enhancement of all‐inorganic CsPbBr3 perovskite solar cells enabled by Nb‐doped SnO2 as effective electron transport layer

All‐inorganic CsPbBr3‐based perovskite solar cells (PSCs) have attracted great attention because of their high chemical and thermal stabilities in ambient air. However, the short‐circuit current density (Jsc) of CsPbBr3‐based PSCs is inadequate under solar illumination because of the wide bandgap, inefficient charge extraction and recombination loss, leading to lower power‐conversion efficiencies (PCEs). It is envisaged that in addition to narrowing the bandgap by alloying, Jsc of the PSCs could be enhanced by effective improvement of electron transportation, suppression of charge recombination at the interface between the perovskite and electron transporting layer (ETL), and tuning of the space charge field in the device. In this work, Nb‐doped SnO2 films as ETLs in the CsPbBr3‐based PSCs have been deposited at room temperature by high target utilization sputtering (HiTUS). Through optimizing the Nb doping level alone, the Jsc was increased by nearly 19%, from 7.51 to 8.92 mA·cm−2 and the PCE was enhanced by 27% from 6.73% to 8.54%. The overall benefit by replacing the spin‐coated SnO2 with sputtered SnO2 with Nb doping was up to 39% increase in Jsc and 62% increase in PCE. Moreover, the PCE of the optimized device showed negligible degradation over exposure to ambient environment (T ˜ 25 °C, RH˜45%), with 95.4% of the original PCE being maintained after storing the device for 1200 h.

Titanium doped MoSe2 coatings – Synthesis, structure, mechanical and tribological properties investigation

In this work, we doped sputtered MoSe2 coatings with Ti to improve their mechanical and tribological properties. Mo-Se-Ti coatings were prepared onto steel discs by High Target Utilisation Sputtering (HiTUS). The Ti was in the range 7–31 at.%, which led to Se/Mo ratios of 1.7–2.7. The Mo-Se-Ti coatings possessed a polycrystalline structure for the lower Ti contents and became amorphous when Ti content was above approx. 18 at.%. The hardness of the initially soft (0.3 GPa) pure MoSe2 coatings was dramatically improved with Ti additions (up to 7.5 GPa). Sliding experiments confirmed excellent tribological properties: coefficient of friction values from 0.02 to 0.08 and very low wear rates (8×10-8mm3N-1m−1) of the Ti-containing coatings tested in the humid air at the loads in the range of 2–45 N. The outstanding self-lubricant properties of Mo-Se-Ti coatings were attributed to the transformation of the topmost amorphous part of the coating into crystalline MoSe2 tribofilm while preserving inner parts of the coating in as-deposited state ensuring good load-bearing capacity. There is strong experimental evidence that Ti has a gettering effect in the tribological contact, which protects MoSe2 tribofilm against oxidation.

Structural and mechanical properties of W-C: H coatings prepared by HiTUS

The structure and mechanical properties of hydrogenated tungsten-carbon (W-C: H) coatings have been studied as a function of the composition and structure. These coatings were prepared by the High Target Utilization Sputtering (HiTUS), the first time used for this type of coatings. W-C: H coatings were deposited from tungsten–carbide target in argon, argon–acetylene (C2H2), and argon–methane (CH4) atmosphere on bearing steel 100Cr6 substrate, Al substrate, Si wafer a, and WC-Co substrate. W-C: H coatings obtained at different acetylene and methane flow were characterized by Elastic Recoil Detection Analysis (ERDA) and Rutherford Backscattering (RBS), X-ray diffraction, Transmission electron microscopy (TEM), and nanoindentation. Mechanical properties of these coatings are controlled within a range through a change in mutual concentration of crystalline phase and amorphous hydrogenated carbon matrix. The higher hardness (Hit = 29.5 ± 4.5 GPa) was measured for coating with 3 sccm methane addition. W-C: H coatings with more than 4 sccm of C2H2 and CH4 addition had fully amorphous structure and worse off mechanical properties.

Tribological behaviour of Mo-S-N solid lubricant coatings in vacuum, nitrogen gas and elevated temperatures

Molybdenum disulphide (MoS2) is well known for the exceptional tribological properties in inert and high vacuum environments. On the other hand, these properties rapidly degrade in humid and higher temperature (>300 °C) environments which cause increase of the friction coefficient and substantial increase of the wear. Apart from this, MoS2 films also suffers of porous structure, very low hardness and low load-bearing capacity which limits its applications in terrestrial atmosphere and more demanding conditions. Mo-S-N coatings published in previous studies revealed greatly improved mechanical and tribological properties in humid environment – low coefficient of friction, very low wear rates and one order of magnitude higher hardness. However, to this date, knowledge about sliding response of these Mo-S-N coating is mainly limited to humid air. In this work, we tested Mo-S-N coatings with different nitrogen contents from 0 to 40 at.% of N in vacuum (10−2 Pa), nitrogen atmosphere and elevated temperatures. The coatings were deposited by High Target Utilisation Sputtering method. All tribological tests were performed using ball-on-disc testing rig. A maximum hardness of 8 GPa was measured for the 19 and 31 atomic % N-doped coatings. In all testing conditions, the pure MoS2 films had COFs in the range of 0.02–0.15 and wear rates of 1.2–22×10−6 mm3N−1 m−1. The COF and specific wear rates decreased with N additions. Mo-S-N films had COFs between superlubric 0.007 and 0.13 and wear rates of 0.08–3×10−6 mm3N−1 m−1. The best overall tribological performance was shown to be for the Mo-S-N films containing 31 at.% of N. This study concluded that Mo-S-N coatings performed better than MoS2 in all testing conditions.

Structure, mechanical and tribological properties of MoSe2 and Mo-Se-N solid lubricant coatings

Mo-Se-N films were prepared by pulsed direct current (DC) High Target Utilisation Sputtering (HiTUS) in reactive Ar + N2 atmosphere. Here, the effect of nitrogen doping was studied. MoSex film with Se/Mo atomic ratio ~ 2 exhibited polycrystalline structure and the lowest coefficients of friction (COFs) in humid air from 0.025 to 0.1 for loads in the range 2–45 N. Mo-Se-N coatings were deposited with N concentrations ranging from 1 to 40 at.%, whereas Se/Mo ratio varied from 0.6 to 2. Mo-Se-N coatings formed amorphous structures for the N contents above 7 at.% and increased hardness proportional with the N content up to 9 GPa. The addition of nitrogen also resulted in a general decrease in wear rate of two orders of magnitude when compared to pristine films while retaining a reasonably low coefficient of friction. Mo-Se-N films showed notable COF values in humid environment ranging from 0.22 to 0.015 when tested using loads from 2 to 45 N. The excellent friction properties of Mo-Se-N films were associated to the crystallisation of a MoSe2 tribofilm in the wear scar. Moreover, we showed that modern pulsed DC HiTUS technology represents a suitable way of producing thin films with a variety of elemental compositions and desired mechanical and tribological properties, even from sensitive, semi-conducting and extremely low thermally conductive MoSe2 targets.

The Effect of Plasma Pretreatment on the Morphology and Properties of Hitus Coatings

Abstract WC coatings prepared by High Target Utilization Sputtering (HITUS), a relatively new technology, were deposited on three types of substrates. These were silicon (111), steel (100Cr6), and ceramic (WC-Co). The influence of RF plasma power pretreatment on final properties of WC coatings was investigated with two interlayer materials for bonding. The morphology, roughness, and mechanical properties of coatings were studied. The relation between plasma RF power and roughness was found. No significant change in mechanical properties was detected with change in plasma RF power. The dependence of nanohardness and scratch behavior on HITUS WC coatings was investigated.

Control of grain orientation and its impact on carrier mobility in reactively sputtered Cu2O thin films

Grain orientation can be particularly important in devices such as thin film transistors (TFTs) where grain boundaries present a barrier to lateral carrier transport. This paper demonstrates that thin films of nanocrystalline cuprous oxide (Cu2O) can be grown with control of the grain orientation in the direction of either [111] or [100] perpendicular to the substrate surface using a high target utilization sputtering system. This allows a systematic study of the effect of grain orientation on the carrier mobility in Cu2O films. It is shown that the carrier mobility in as-deposited films is similar for both grain orientations while [100]-oriented thin films exhibit a higher carrier mobility for lateral conduction than films with a [111] orientation after annealing, which is discussed from the viewpoint of the Urbach energy, crystallinity and surface morphology. This experimental finding suggests that Cu2O thin films with a [100] surface grain orientation are favorable for device applications such as p-type TFTs where a high in-plane carrier mobility is desired.

Structure evolution and mechanical properties of hard tantalum diboride films

Tantalum diboride (TaB2) belonging to the ultrahigh temperature ceramics family is proving to be a promising material for hard protective films, thanks to its high thermal stability and excellent mechanical properties. However, growth of TaB2 ± x films prepared using physical vapor deposition techniques is strongly affected by Ar neutrals reflected from a stoichiometric TaB2 target due to a significant mass difference of heavy Ta and light B atoms leading to substantial changes in the final chemical composition and structure of films. In this work, TaB2 ± x films are experimentally prepared using high target utilization sputtering. Stopping and range of ions in matter simulations are used to investigate the behavior of Ar neutrals during deposition processes. A wide range of analytical methods is used to completely characterize the chemical composition, structure, and mechanical properties of TaB2 ± x films, and the explanation of the obtained results is supported by density functional theory calculations. TaB2 ± x films grow in a broad compositional range from TaB1.36 to TaB3.84 depending on the kinetic energy of Ar neutrals. The structure of overstoichiometric TaB2 + x films consists of 0001 preferentially oriented α-TaB2 nanocolumns surrounded by a boron-tissue phase. In the case of highly understoichiometric TaB2 − x films, the boron-tissue phase disappears and the structure consisting of 0001 and 101¯1 oriented α-TaB2 nanocolumns is formed. All TaB2 ± x films exhibit excellent mechanical properties with high hardness, ranging from 27 to 43 GPa and relatively low values of Young's modulus in the range of 304–488 GPa.

The effects of deposition conditions on hydrogenation, hardness and elastic modulus of W-C:H coatings

The additions of C2H2, CH4 and H2 in hybrid PVD-PECVD of W-C:H coatings deposited using High Power Impulse Magnetron Sputtering (HiPIMS) and High Target Utilization Sputtering (HiTUS) were investigated to determine their effects on the content and chemical composition of the amorphous carbon-based boundary phase and mechanical properties of the coatings. Substantial differences were observed: CH4 always produced higher concentrations of hydrogen and lower concentrations of carbon than C2H2 and HiPIMS resulted in higher contents of amorphous carbon-based boundary phase and higher levels of its hydrogenation than HiTUS. The detrimental effects of higher carbon and hydrogen contents in the boundary phase on hardness and indentation modulus were attributed to the consumption of CC bonds by CH bonds during hydrogenation and reduction of cross-linking of the polymeric network in the boundary phase. The HiPIMS W-C:H coatings deposited with acetylene and hydrogen exhibited medium (∼20 GPa) hardness and elastic modulus (200–220 GPa) with HIT/EIT > 0.1 suggesting improved toughness and wear resistance. These properties were attributed to the optimum combination of hydrogenation, hybridization and cross linking in the carbon-based boundary phase.

Hybrid PVD-PECVD W-C:H coatings prepared by different sputtering techniques: The comparison of deposition processes, composition and properties

The plasma polymerization processes during hybrid PVD-PECVD deposition, structure, hydrogenation, hybridization, hardness and coefficients of friction in W-C:H coatings prepared by direct current magnetron sputtering (DCMS), High Power Impulse Magnetron Sputtering (HiPIMS) and High Target Utilization Sputtering (HiTUS) were reviewed as a function of acetylene (0–12 sccm C2H2) and hydrogen (0–20 sccm H2) additions into Ar atmosphere. The addition of acetylene resulted in the increase of carbon and hydrogen contents in the matrix via incorporation of CxHy fragments with the C2H, 2C and CH radicals being the “primary” source for growth. The level of hydrogenation in the carbon matrix was found to be related to the level of sp3 hybridization and cross-linking as well. Hardness and coefficient of friction of the studied W-C:H coatings were found to be affected not only by hydrogenation and hybridization, but also by the sputtering technique. HiPIMS provided the best combination of hybridization, hydrogenation and cross-linking in the carbon structure resulting in W-C:H coatings with reasonably high (~20 GPa) hardness and simultaneously sufficiently low (≤0.1) coefficients of friction. Thus, HiPIMS applied to hybrid PVD-PECVD W-C:H coatings expands the range of their mechanical and tribological properties compared to DCMS and HiTUS.

Structure, mechanical and tribological properties of Mo-S-N solid lubricant coatings

Solid lubricant coatings deposited by plasma-assisted deposition techniques represent modern way to reduce the coefficient of friction in lubricant-free sliding contacts. Molybdenum disulphide (MoS2) is perhaps the most known and applied solid lubricant coating; however, its use is strictly limited by low hardness and environmental sensitivity. To improve mechanical and tribological properties, we doped MoS2 coating with nitrogen.Mo-S-N self-lubricant films were deposited by pulsed d. c. High Target Utilisation Sputtering (HiTUS) in reactive atmosphere. The effect of deposition conditions on chemical composition, structure and mechanical properties of MoSx and Mo-S-N coatings was studied; films with the most promising properties have been selected for tribological testing. MoSx film with the elemental composition sulphur to molybdenum (S/Mo ratio) 1.6 exhibited the coefficients of friction (COFs) in humid air 0.17 and 0.07 for loads 2 and 15 N, respectively. Mo-S-N films were prepared with nitrogen content in a range of 11 to 50 at., whereas S/Mo ratio varied from 1.35 to 0.4. Mo-S-N films were amorphous or nanostructured with nanograins of molybdenum disulphide. Hardness increased with N content up to 14 GPa for film with the highest content of nitrogen. Friction behaviour in humid air was evaluated using a ball-on-disk tribometer. Globally, the doping with N resulted in hardness in Mo–S–N films one order of magnitude higher and wear rate two orders of magnitude lower than in an undoped one, keeping the friction coefficient at the same level or even lower. These coatings showed remarkable friction coefficients in humid air from 0.28 to 0.05 with loads from 2 to 15 N, respectively. The excellent friction properties were attributed to the formation of a thin molybdenum disulphide tribofilm at the sliding interface. HiTUS represents a very promising way of producing thin films on the thermally sensitive substrates (e.g. bearing steel) with desired properties.

Large exchange bias induced by polycrystalline Mn3Ga antiferromagnetic films with controlled layer thickness

Polycrystalline Mn3Ga layers with thickness in the range from 6–20 nm were deposited at room temperature by a high target utilisation sputtering. To investigate the onset of exchange-bias, a ferromagnetic Co0.6Fe0.4 layer (3.3–9 nm thick) capped with 5 nm Ta, were subsequently deposited. X-ray diffraction measurements confirm the presence of Mn3Ga (0 0 0 2) and (0 0 0 4) peaks characteristic of the D019 antiferromagnetic structure. The 6 nm thick Mn3Ga film shows the largest exchange bias of 430 Oe at 120 K with a blocking temperature of 225 K. The blocking temperature is found to decrease with increasing Mn3Ga thickness. These results in combination with x-ray reflectivity measurements confirm that the quality of the Mn3Ga/Co0.6Fe0.4 interface controls the exchange bias, with the sharp interface with the 6-nm-thick Mn3Ga inducing the largest exchange bias. The magneto-crystalline anisotropy for 6 nm thick Mn3Ga thin film sample is calculated to be . Such a binary antiferromagnetic Heusler alloy is compatible with the current memory fabrication process and hence has a great potential for antiferromagnetic spintronics.

Mechanical and tribological properties of the High Target Utilization Sputtering W-C coatings on different substrates

The effects of three types of substrates (Si, bearing steel, and WC-Co) and acetylene addition (0–3.2vol.% in Ar atmosphere) on the topography, structure, composition, nanohardness and tribological behavior of the High Target Utilization Sputtering W-C coatings were investigated. The results showed that the substrates affected mostly the coating topography, roughness and nanohardness whereas the composition, indentation moduli and coefficients of friction were influenced only by the increase of free carbon content from acetylene addition. Up to ~5GPa difference in the hardness of the W-C coatings on Si substrates compared to that on steel was obtained. Simultaneously, methodological problems with the hardness measurements were identified on WC-Co substrate which has the hardness close to that of the coatings. The average values of the coefficient of friction were around 0.3 and slightly decreased at higher carbon contents but the influence of the substrates was small.