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Pathogenic microbes, such as bacteria and viruses, can spread quickly via contaminated surfaces. Most of these pathogenic microorganisms can survive on surfaces for a long time. Touching these surfaces can lead to the transmission of the microorganisms to the human body and cause serious illnesses. ZrN-Cu coatings containing different amounts of Cu were deposited using an industrial PVD system, and their ability to inhibit bacteria and inactivate the SARS-CoV-2 virus was tested. Microstructural studies showed the formation of two distinct ZrN and Cu phases when Cu content was sufficiently high. Hardness and elastic modulus were inversely proportional to the Cu content. The coatings showed outstanding bactericidal properties against Escherichia coli and Pseudomonas aeruginosa, especially when Cu content was more than 12 at.% and exposure time was longer than 40 min. The coatings, however, did not exhibit any significant virucidal properties. Good mechanical properties, along with excellent antibacterial effects, make these coatings suitable for use as self-sanitizing surfaces on objects that people regularly touch and that are prone to bacterial contamination. Their use would thus allow for only minimal transmission or multiplication of bacteria, and the treated surface would not serve as another source of infection.

Coated components used in industry are often exposed to repetitive dynamic impact load. The dynamic impact test is a suitable method for the study of thin protective coatings under such conditions. Aim of this paper is to describe the method of dynamic impact testing and the novel concepts of evaluation of the impact test results, such as the impact resistance and the impact deformation rate. All of the presented results were obtained by testing two W-B-C coatings with different C/W ratio. Different impact test results are discussed with respect to the coatings microstructure, the chemical and phase composition, and the mechanical properties. It is shown that coating adhesion to the HSS substrate played a crucial role in the coatings’ impact lifetime.

AlCrN coatings, which are characterized by high hardness and good wear resistance, are often used for drilling, milling, and punching tools. Therefore, the study of the behaviour of these coatings under cyclic impact loading is essential for their optimization. Our previous work has focused on the study of the composition and microstructure of AlCrN coatings prepared using a cathodic arc deposition system with a SCIL® controller that controls the average ion energy per deposited atom (Ed). Two sets of coatings were prepared in two different modes, with a metal target and with a poisoned target. The chemical compositions of the coatings were very similar regardless of their deposition conditions, but the structure and mechanical properties of the coatings depended strongly on Ed. The present work focused on the scratch adhesion and impact wear of these two sets of AlCrN coatings. The lifetimes of both sets of samples under repeated dynamic impacts were tested using a dynamic impact tester with a WC-Co ball. It was shown that the impact behaviour of the coatings prepared in the metallic regime does not depend on the deposition conditions. However, the impact behaviour of the coatings deposited in poisoned mode was improved by increasing Ed.

In this paper the overview of the most important approximate methods for the optical characterization of inhomogeneous thin films is presented. The following approximate methods are introduced: Wentzel–Kramers–Brillouin–Jeffreys approximation, method based on substituting inhomogeneous thin films by multilayer systems, method based on modifying recursive approach and method utilizing multiple-beam interference model. Principles and mathematical formulations of these methods are described. A comparison of these methods is carried out from the practical point of view, ie advantages and disadvantages of individual methods are discussed. Examples of the optical characterization of three inhomogeneous thin films consisting of non-stoichiometric silicon nitride are introduced in order to illustrate efficiency and practical meaning of the presented approximate methods.

In this study mid-frequency pulsed-DC magnetron sputtering was used to deposit W-B-C coatings. The effect of coating composition and the deposition parameters on the structure, mechanical and tribological properties of the coatings was investigated. The broad diffraction peaks in the X-ray diffractogram indicated the amorphous to nanocrystalline nature of the coatings. The hardness of the coatings ranged from 22.6 to 26.2 GPa. The coatings prepared at the elevated temperature of 500 degrees C exhibited greater hardness compared to the coatings prepared at the ambient temperature. The amount of W in the coatings was the main parameter influencing the friction coefficient with a higher W content leading to a higher friction coefficient. The coatings prepared at 500 degrees C showed lower wear in tribological measurements due to their higher hardness compared to the coatings prepared at ambient temperature. The friction coefficient decreased as the testing temperature increased beyond 500 degrees C. XRD analyses after the high temperature tests have shown that this decrease was due to the formation of W-O Magneli phases, which acted as a solid-state lubricant.

Low ductility and brittle deformation behaviors are major drawbacks of currently used commercial hard ceramic-based protective coatings. Recent ab-initio calculations revealed that the coexistence of metallic, boride and carbide bonds in a nanolaminate structure of crystalline W2BC system provides a combination of high hardness together with moderate ductility. The present paper deals with coatings containing W, B and C with different compositions and investigates the effect of the boron to tungsten ratio (B/W) on the structural and mechanical properties of W-B-C coatings prepared by pulsed-DC magnetron sputtering at a moderate temperature. Coatings with low B/W were deposited in a nanocomposite structure, whereas coatings with high B/W ratios were near-amorphous. The structure of the coatings was not a decisive factor in determining their mechanical properties. These were, however, directly correlated with the chemical bonds present. All the coatings exhibited high fracture resistance. These properties together with good adhesion to cemented tungsten carbides make W-B-C coatings promising candidates for the future protective coatings of tools which undergo large deformation in their working cycle.

Understanding mechanisms behind the formation and propagation of ionisation zones, so-called spokes, have been highly important since the first observations in high power impulse magnetron sputtering discharges. To this day, however, a complete description is still lacking. This contribution gives an insight into the spokes in reactive Ar–N2 atmosphere using titanium target. The aim of this study is to describe not only global parameters of spokes such as their shape, length and propagation velocity but also provide a description of parameters evolving over the spoke, such as floating potential and spectral emission. The measurements of the latter clearly showed which species emission is most prominent and how it changes with transition from non-reactive argon discharge towards the discharge driven in a pure nitrogen atmosphere. Implications on the gas dynamics and discharge transitions are discussed.

Ta&ndash, B&ndash, C coatings were non-reactively sputter-deposited in an industrial batch coater from a single segmented rotating cylindrical cathode employing a combinatorial approach. The chemical composition, morphology, microstructure, mechanical properties, and fracture resistance of the coatings were investigated. Their mechanical properties were linked to their microstructure and phase composition. Coatings placed stationary in front of the racetrack of the target and those performing a 1-axis rotation around the substrate carousel are compared. Utilization of the substrate rotation has no significant effect on the chemical composition of the coatings deposited at the same position compared to the cathode. Whereas the morphology of coatings with corresponding chemical composition is similar for stationary as well as rotating samples, the rotating coatings exhibit a distinct multilayered structure with a repetition period in the range of nanometers despite utilizing a non-reactive process and a single sputter source. All the coatings are either amorphous, nanocomposite or nanocrystalline depending on their chemical composition. The presence of TaC, TaB, and/or TaB2 phases is identified. The crystallite size is typically less than 5 nm. The highest hardness of the coatings is associated with the presence of larger grains in a nanocomposite structure or formation of polycrystalline coatings. The number, density, and length of cracks observed after high-load indentation is on par with current optimized commercially available protective coatings.

This research was devoted to studying the influence of the taper angle on the micro-compression of micro-pillars fabricated from near-amorphous and nanocrystalline Mo-B-C coatings. A series of micro-pillars with a taper angle between 4–14° was fabricated by focused ion beam technique. The deformation mechanism was found to be dependent on the taper and, also, on the crystallinity of the coating. In order to obtain correct values of yield strength and Young’s modulus, three empirical models of stress correction were experimentally tested, and the results were compared with nanoindentation measurements. It was shown that the average stress correction model provided comparable results with nanoindentation for the yield strength for taper angles up to ~10°. On the other hand, the average radius or area model gave the most precise results for Young’s modulus if the taper angle was

Publisher's version (útgefin grein), The self-organised plasma patterns, known as spokes or ionisation zones in magnetron sputtering discharges, were observed in a wide range of power densities, from low power direct current magnetron sputtering (dcMS) discharge to high power impulse magnetron sputtering (HiPIMS) discharge. For some target materials and non-reactive gases, it was observed that at very high power densities (>3 kW cm-2) the plasma exhibits a transition from a regime where spokes are observed to a homogeneous plasma regime. In this contribution, we present a comparison of plasma properties: plasma emission (optical emission spectroscopy) and flux of argon and chromium ions (mass spectrometry), measured both in the spoke regime and in the homogeneous plasma regime, aimed to expand the understanding of the plasma transition between the two modes. A simple biased flat probe was used to distinguish between the spoke regime and the homogeneous plasma regime. It was found that the flux of multiply charged ions (Ar2+, Cr2+, Cr3+, Cr4+) increases abruptly at the transition between the spoke regime and the homogeneous plasma regime. Similarly, the emission from Cr+ ions exhibits a strong increase of about 50% when the plasma torus becomes homogeneous. These observations are interpreted as an increase in electron temperature and a change in the electron heating mode, from a combination of secondary electron heating and Ohmic heating towards pure Ohmic heating. The transition to the homogeneous plasma regime and pure Ohmic heating is only observed in non-reactive HiPIMS discharges for target atoms with the second ionisation potential higher than the first ionisation potential of Ar (15.76 eV), and a self-sputter yield larger than 1., This research has been supported by project LM2018097 funded by the Ministry of Education, Youth and Sports of the Czech Republic and project GA19-00579S funded by the Czech Science Foundation. This work has been supported by the German Science Foundation (DFG) within the frame of the collaborative research centre SFB-TR 87

Commercial ceramic protective coatings usually exhibit high hardness, but low ductility impairs their performance and application-oriented properties. Accordingly, a state-of-the-art magnetron sputtered W-B-C coating can be a promising coating for the tooling industry due to its hard yet tough characteristics. In the present study, we have employed substrate biasing to enhance the delivered energy to the growing film and have investigated the effect of bias voltage on the structural and mechanical behavior of W-B-C coatings. The investigations revealed that increasing the substrate bias voltage enhanced the re-sputtering of B and C atoms and subsequently varied the chemical composition of the coatings and significantly decreased the growth rate. It also enhanced the crystallinity of the coatings. We demonstrate how the bias voltage led to an unusual transition from a featureless to a columnar microstructure. Furthermore, it was observed that as the substrate bias voltage increased from 0 V to −125 V, the compositional and structural changes resulted in a slight decrease of the hardness, while a further increase in the bias voltage to −200 V enhanced the hardness. This increase was attributed to the suppression of dislocation movement and grain boundary deformation processes by solute segregation and by lattice defects.

The plasma potential at a typical substrate position is studied during the positive pulse of a bipolar high-power impulse magnetron sputtering (bipolar HiPIMS) discharge with a Cu target. The goal of the study is to identify suitable conditions for achieving ion acceleration independent on substrate grounding. We find that the time-evolution of the plasma potential during the positive pulse can be separated into several distinct phases, which are highly dependent on the discharge conditions. This includes exploring the influence of the working gas pressure (0.3-2 Pa), HiPIMS peak current (10-70 A corresponding to 0.5-3.5 A cm(-2)), HiPIMS pulse length (5-60 mu s) and the amplitude of the positive voltage U (+) applied during the positive pulse (0-150 V). At low enough pressure, high enough HiPIMS peak current and long enough HiPIMS pulse length, the plasma potential at a typical substrate position is seen to be close to 0 V for a certain time interval (denoted phase B) during the positive pulse. At the same time, spatial mapping of the plasma potential inside the magnetic trap region revealed an elevated value of the plasma potential during phase B. These two plasma potential characteristics are identified as suitable for achieving ion acceleration in the target region. Moreover, by investigating the target current and ion saturation current at the chamber walls, we describe a simple theory linking the value of the plasma potential profile to the ratio of the available target electron current and ion saturation current at the wall. Funding Agencies|Swedish Research CouncilSwedish Research CouncilEuropean Commission [VR 2018-04139]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University (Faculty Grant SFOMat-LiU) [2009-00971]; Eurostars program (IonDrive) [E!114277]; Ministry of Education Youth and Sports of Czech RepublicMinistry of Education, Youth & Sports - Czech Republic [LM2018097]; Czech Science FoundationGrant Agency of the Czech Republic [GA19-00579S]; National Natural Science Foundation of ChinaNational Natural Science Foundation of China (NSFC) [51805102, 52165021]

A new approach to calculation of optical quantities of inhomogeneous layers is presented. In this approach, the Richardson extrapolation is used to improve the accuracy of the method, in which the inhomogeneous layer is approximated by a stack of thin homogeneous layers. The results presented in this paper are based on the assumption that the media are isotropic and the inhomogeneity is along the axis normal to the boundary. The results obtained by the new method are compared with those obtained without the Richardson extrapolation. The Richardson extrapolation brings significant improvement in accuracy, especially if the number of approximating layers is large. Moreover, the method using the Richardson extrapolation proceeds in steps with an error estimate available in each step; thus, the calculation can be stopped when the desired accuracy is reached. The use of the method is illustrated by means of the optical characterization of strongly inhomogeneous film of non-stoichiometric silicon nitride.

Preparation of coatings simultaneously exhibiting high hardness and enhanced fracture resistance is a hot topic, as nowadays used ceramic protective coatings show difficulties to cope with increased demands due to their inherent brittleness. Material exhibiting seemingly contradictory combination of mechanical properties like high hardness and moderate ductility enhancing the fracture resistance - was recently predicted by ab initio calculations in the crystalline X2BC system. The presented study is focused on the study of the influence of the C/W ratio on the microstructure, the content of different chemical bonds and the mechanical properties of WBC coatings prepared by magnetron sputtering at moderate temperature.

State-of-the-art protective coatings often suffer from brittleness. Therefore, the coatings are intensively sought which would simultaneously exhibit high hardness and stiffness with moderate ductility and fracture resistance. In this paper, we report on the nanostructure designing of coatings containing metal, boron, and carbon enabling the simultaneous presence of stiff boridic and carbidic bonds together with weaker metallic bonds to provide coatings with these desirable properties. Three designs are presented with different relative amounts of nanocrystalline and amorphous phases, ranging from near-amorphous to prevalently crystalline microstructure. All presented coatings exhibit an unusual combination of high fracture resistance and high hardness that cannot be achieved with state-of-the-art protective coatings. Indentation tests at high loads revealed that no cracks are present at the surface of the investigated coatings while state-of-the-art ceramic protective coatings already exhibit significant cracking. Cracks in the bulk of the presented coating are detected only when the deformation is so severe that the substrate itself fails.

Temporal evolutions of the ground state number densities of titanium atoms and ions and the ionised density fraction during pulse on-time are experimentally investigated for the high-power impulse magnetron sputtering process in an Ar and Ar/N2 atmosphere. For the study, two distinct pulses with the same pulse length at a constant average power but different pulse off-times were selected. In both conditions, four representative points within the hysteresis curve were chosen, and the time evolutions of sputtered species densities were investigated in both the target and the substrate regions. At the pulse beginning, a high density of residual particles sputtered during the previous pulse is present in both studied regions. In the target region, in conditions of longer pulse off-time and thus higher peak discharge current, 95% of sputtered particles are ionised in metallic, transition and compound regimes. With shorter pulse off-time conditions, and thus a lower peak discharge current, the ionised density fraction is the lowest in the metallic regime; in the transition and compound regimes, it exceeds 80%. In the substrate region, the temporal evolution of sputtered species densities differs from that obtained in the target region. After the pulse ignition, titanium atoms and ions remaining near the substrate from the previous pulse are pushed away. In the metallic regime, the sputtered atoms refill the substrate region already during the pulse on-time in both the low- and high-current conditions. In the high-current conditions, the titanium ions arrive at the substrate together with the sputtered atoms; however, in the low-current conditions, the titanium ion density decreases during the pulse on-time, and the titanium ions arrive later during the pulse off-time. In the transition and compound regimes, both densities steadily decrease during the pulse on-time and the titanium atoms and ions arrive at the substrate during the pulse off-time.

The deposition rate, as well as the structure of a coating for a given magnetron sputtered material are determined by the plasma properties which are significantly dependent on the type of plasma generation. Single-pulse high power impulse magnetron sputtering (s-HiPIMS), multipulse HiPIMS (m-HiPIMS) with the same energy per pulse sequence and conventional direct current magnetron sputtering (DC-MS) were employed to deposit metallic Ti coatings. Varying the number of pulses in one pulse sequence in multipulse HiPIMS operation enables us to influence the ion fluxes on the substrate and the ionisation of the sputtered titanium. The grain size for the HiPIMS-deposited coatings was in the range of 5 to 25 nm depending on the number of pulses in the pulse sequence, whereas it was 15 nm for the coating prepared by the DC-MS. By the use of multipulse HiPIMS, it was also possible to achieve coatings with a smoother surface morphology and lower roughness as well rougher coatings with larger asperities and higher roughness compared to DC-MS. The texture and the deposition rate were significantly affected by the number of pulses, too.

The average ion energy per deposited atom (Ed) is defined as the product of the ion energy (Ei) and ion-deposition flux ratio (Ji/Jd) in magnetron sputtering deposition. Ed captures both the geometrical, and plasma characteristics of the deposition system and hence is regarded as a fundamental parameter for describing the energy dependency of coating structure and properties. Nevertheless, Ed is not a universal parameter since an independent variation of its components, i.e., Ei and Ji/Jd, may result in the same Ed but different coating structures and properties. While the controlling of Ji/Jd is not possible in most conventional magnetron sputtering systems, this study employed an industrially developed SCIL® (sputter coatings induced by lateral glow discharge) technology to independently control the ion flux (Ji) and investigate the dependence of structure, mechanical properties, and cutting performance of the AlCrN coatings on the Ed and its components. The results revealed that the structure of the AlCrN coatings was mainly dependent on the Ji/Jd component of Ed, where a transition from a cubic structure into a hexagonal structure took place beyond a critical level of Ji/Jd. The elastic modulus showed no Ed dependency and was only affected by coating structure. However, the hardness was strongly dependent on the Ed. Whether in Ei or Ji/Jd, an increase led to a hardness enhancement through the synergic effect of the residual stress hardening, coating densification, and grain refining mechanisms. The cutting performance of deposited tools under real working conditions was also found to be dependent on the Ed and, in particular, on Ji/Jd. Increasing Ed from ~860 to ~1170 eV/atom led to a ~55% increase in tool lifetime, reaching 90% performance of the benchmark arc-deposited coating.

Titanium carbide/carbon coatings were deposited by hybrid PVD-PECVD process of titanium sputtering in an atmosphere containing acetylene. Samples were placed above the titanium target centre and above the target racetrack in the same vertical distance to the target to examine the effect of the relative substrate to target position on the properties of the deposited coatings. The different positions of the samples led to significantly different levels of the energy influx onto the growing coating. These differing conditions at the substrate led to altering of the coating's chemical as well as phase composition. Also, the grain size, lattice parameter and the mean grain separation were affected by the energy flux change. Coatings deposited above the racetrack with carbon content ≲ 60% exhibited smaller grains, higher amount of the a-C phase and higher mean grain separation. This microstructure refinement yielded 20–30% higher hardness of the coatings deposited above the target racetrack than corresponding coatings deposited above the target centre. Thus, the sample positioning in the chamber proved to be an important parameter for resulting properties of the deposited coatings.

The importance of the often omitted running-in phase of tribological testing was studied on hard nc-TiC/a-C:H coating system selected as a representative of protective tribological coatings. The tribological measurements were periodically interrupted and the counterpart ball was replaced by a new one after every interrupted test to simulate machining applications, where the coatings are repeatedly in contact with a new material. The changes in the coefficient of friction and the wear rate of the counterpart ball were found to be dependent mainly on the roughness of the coating at any stage. It was found out that after substantial smoothening of the wear track of the measured coating, the coefficient of friction stabilized at the steady-state value attained in an uninterrupted long tribotest. This steady state value was reached at the very beginning of the test and initial instabilities in the coefficient of friction were no longer observed. It was also concluded that only after the nc-TiC/a-C:H coating gets smoothened enough within the wear track, the steady-state coefficient of friction can describe even applications where the counterpart is being periodically replaced by a new one.

In the present work, nanocomposite Mo-B-C coatings were deposited on high speed steel and hard metal substrates by magnetron sputtering of three targets. These coatings were subjected to annealing to final temperatures in the range from 500 °C to 1000 °C. It was found that the as deposited Mo-B-C coatings exhibited hardness of ∼20 GPa, nanocomposite microstructure with very fine grains (∼2 nm) and low degree of crystallinity. The X-ray diffraction and transmission electron microscopy together with selective area electron diffraction were used to study the temperature induced changes of the microstructure of the coating and its crystallinity. The annealing process significantly improved the hardness (from ∼20 GPa to ∼30 GPa) and effective elastic modulus (from initial 330 GPa–500 GPa) of coatings while their resistance to fracture was kept sufficiently high.

Nanocomposite coatings consisting of titanium carbide crystallites embedded in amorphous carbon matrix were deposited utilizing direct current magnetron sputtering (DCMS) and high power impulse magnetron sputtering (HiPIMS) of titanium target in argon/acetylene atmosphere. DC driven depositions of coatings with high amount of carbon were accompanied by significant arcing during the deposition. HiPIMS utilization made reliable arc-free deposition of coatings with high carbon content possible. Analyses of the coating structure revealed that utilization of HiPIMS favours carbon incorporation into the TiCx grains rather than to the matrix. HiPIMS deposited coatings exhibited stoichiometry of the TiCx grains closer to unity with grains exhibiting lower lattice parameter and a lower fraction of the a-C matrix. This led to a smaller mean TiCx grain separation by the a-C:H matrix. Also the surface structure of the HiPIMS deposited coatings was much finer. The structure refinement resulted in overall higher hardness of HiPIMS deposited coatings with the hardest coatings reaching the superhard region of > 40 GPa and in 40% increase of H/E ratio and nearly threefold increase of H3/E2 ratio.

Nanocomposite nc-TiC/a-C:H thin films exhibit unique combination of mechanical properties, high hardness, low friction, and wear. Selective doping by weak-carbide forming element can be used in order to specifically design the physical and chemical properties of nc-TiC/a-C:H coatings. In this paper we report on an effect of nickel addition on structure and hardness of the nc-TiC/a-C:H coatings. The effect of Ni alloying on the coating structure under conditions of DCMS and HiPIMS depositions was studied. The coating structure was correlated with the coating hardness. The grain size, the grain carbon vacancy concentration, and the mean grain separation were found to be the key parameters determining the coating hardness. Ni doping proved to have a significant effect on the coating microstructure which resulted in changes of the hardness of the deposited coatings.

The study was devoted to optical characterization of non-stoichiometric silicon nitride films prepared by reactive magnetron sputtering in argon-nitrogen atmosphere onto cold (unheated) substrates. It was found that these films exhibit the combination of three defects: optical inhomogeneity (refractive index profile across the films), uniaxial anisotropy with the optical axis perpendicular to the boundaries and random roughness of the upper boundaries. The influence of the uniaxial anisotropy was included into the corresponding formulae of the optical quantities using the matrix formalism and the approximation of the inhomogeneous layer by a multilayer system consisting of large number thin homogeneous layers. The random roughness was described using the scalar diffraction theory. The processing of the experimental data was performed using the multi-sample modification of the least-squares method, in which experimental data of several samples differing in thickness were processed simultaneously. The dielectric response of the silicon nitride films was modeled using the modification of the universal dispersion model, which takes into account absorption processes corresponding to valence-to-conduction band electron transitions, excitonic effects and Urbach tail. The spectroscopic reflectometric and ellipsometric measurements were supplemented by measuring the uniformity of the samples using imaging spectroscopic reflectometry of the samples using imaging spectroscopic reflectometry. Je studována optická charakterizace nestechiometrických vrstev nitridu křemíku připravených reaktivním magnetronovým naprašováním na chladné (nezahřívané) podložky v argonové – dusíkově atmosféře. Bylo zjištěno, že tyto vrstvy vykazují kombinaci tří defektů: optické nehomogenity (profil indexu lomu napříč vrstvami), jednoosé anizotropie s optickou osou kolmou k rozhraním a náhodné drsnosti horních rozhraní. Vliv jednoosé anizotropie byl zahrnut do odpovídajících vzorců pro optické veličiny užitím maticového formalizmu a aproximací nehomogenní vrstvy mnohavrstevným systémem velkého počtu tenkých homogenních vrstev. Náhodná drsnost byla popsána v rámci skalární teorie difrakce. Zpracování experimentálních dat bylo provedeno užitím mnohavzorkové modifikace metody nejmenších čtverců, ve které byla experimentální data několika vzorků lišících se v tloušťce zpracovávána současně. Dielektrická odezva studovaných vrstev byla modelována pomocí modifikace univerzálního disperzního modelu, který bere v úvahu absorpční procesy odpovídající elektronovým přechodům mezi valenčním a vodivostním pásem, exitačním procesům a Urbachovu konci. Spektroskopická reflektometrická a elipsometrická měření byla doplněna měřením uniformity vzorků pomocí zobrazovací spektroskopické reflektometrie.

Plasma in high-power impulse magnetron sputtering discharge, similarly to other discharges utilising E × B field (Hall thrusters, homopolar devices), undergoes self-organisation into the ionisation zones predominantly rotating in the E × B direction, called spokes. Many studies were conducted focussing on the characterisation of their appearance, mode number, rotational velocity, merging and splitting events in different experimental conditions. Nevertheless, only very little research has been conducted in the case of reactive sputtering, where only the general spoke characteristics were evaluated. A dual-image fast camera screening was utilised to capture plasma emission on 3'' Nb target in a reactive mixture of nitrogen and argon. Spoke characteristics were evaluated while overall pressure and supplied power was kept constant and the content of nitrogen in N2/Ar mixture was varied. The shape, velocity and spoke mode number were significantly affected by the higher content of N2 in the mixture. To distinguish between the effects of the modified target surface state and reactive gas present in the plasma volume on spokes experiments with compound NbN target were also performed. Surprisingly, no real differences of spoke behaviour between Nb and NbN targets were observed.

The aim of the present work was to study the mechanical properties of thin nanocomposite Mo-B-C coatings consisting of nanocrystalline Mo2BC embedded in amorphous Mo-B-C matrix. Magnetron sputtering of three targets, B4C, C and Mo, was used for coatings preparation. The Mo-B-C coatings were deposited on high speed steel substrates. The fracture resistance of Mo-B-C coatings was studied by both indentation and dynamic impact tests. The impact tests enabled us to predict the load limit causing the coating destruction.

A study of a hybrid PVD-PECVD process of sputtering a titanium target in an argon/acetylene gas mixture was performed. This process was used for the deposition of nanocomposite coatings consisting of titanium carbide grains embedded in an amorphous hydrogenated carbon matrix (nc-TiC/a-C:H). The study was performed under industrial conditions employing a large-scale deposition device with a cylindrical sputtering cathode. When the acetylene supply was gradually increased, a discharge voltage drop and total pressure saturation simultaneously occurred at a certain acetylene supply. The hardest coatings were found always to be deposited at the acetylene supply corresponding to these deposition conditions. However, the acetylene supply to detect the voltage drop and pressure saturation was determined to be dependent on the cathode thickness. A fully automatic procedure suitable for the preparation of hard nc-TiC/a-C:H coatings by the hybrid PVD-PECVD process was proposed in this paper. This approach ensured that the optimal deposition setting was consistently found for the deposition process independent of the cathode thickness. The procedure was thoroughly tested, and it was demonstrated to be reliable and robust. Furthermore, the algorithm ensured the deposition of coatings with the same composition and the same high hardness throughout the cathode lifetime.

X-B-C (X=Mo, Ta) layers prepared by magnetron sputtering were tested. Mechanical properties were characterized by means of nanoindentation experiments in both the static and the dynamic loading regime. The results were correlated with observations of the microstructure under indentation prints by means of scanning and transmission electron microscopy on cross sections prepared using a focussed ion beam. An excellent fracture resistance of prepared nanostructured coatings was found.

Nanostructure coatings based on boroncarbide were prepared using magnetron sputtering technique. The mechanical properties of the coatings were tested using quasi-static and dynamic nanoindentation tests with Berkovich and cube-corner indenters. The fracture resistance of the coatings and the coating/substrate interface was studied. Moreover, the dynamic wear and scratch resistance of the coatings was evaluated by means of impact and scratch tests.

A detailed experimental study of high power impulse magnetron sputtering discharges is performed using time-resolved ground state density mapping of the sputtered neutrals and ions. This Paper deals with the effects related to the plasma-on phase and can be considered as an extension of Paper I being published simultaneously. The influence of plasma pulse duration, pulse energy, gas pressure as well as molecular oxygen admixture on the spatial and temporal particle density evolution is examined. Special attention is given to the temporal evolution of the ionization fraction distribution of the sputtered atoms. In addition, the 2D vector maps reflecting particle propagation, sputtering, and ionization in the discharge volume are also presented and discussed, similarly to the first part of this study [J. Appl. Phys. 128, 043303 (2020)].

A detailed experimental study of high power impulse magnetron sputtering processes is performed by time-resolved imaging of the ground state sputtered particles. New details related to the behavior of both neutral and singly ionized atoms are shown, as a result of separate treatment of the plasma-on and plasma-off time phases. In Paper I, the ion/neutral density redistribution in the ionization zone during sputtering is analyzed; the role of main discharge parameters, such as pulse repetition rate, pulse energy, etc., is discussed systematically. The time-resolved evolution of the ground state levels population for both sputtered neutrals and ions is also considered. In addition, propagation of the sputtered particles is analyzed using 2D density gradient diagrams calculated based on the measured particle density distributions. The results of this work are compared, when possible, to the data obtained previously [Britun et al., J. Appl. Phys. 117, 163302 (2015)].

In this paper, the ground state number densities of titanium atom and ion, ionised density fraction and ionised flux fraction were determined in a high power impulse magnetron sputtering process. Three regions of interest within the deposition chamber were studied; the magnetised plasma region, middle region, and substrate region. Pulse length and applied power were kept constant and working pressure and duty cycle were varied. The effective branching fractions method was utilised to evaluate the number densities of sputtered species from a measured optical emission signal. A biasable quartz crystal microbalance system was used to evaluate the ionised flux fraction and deposition rate. The highest ionised density fraction of 90% was reached in the target region for 1.2% duty cycle and it was mostly independent on working pressure. Moving from the target, the ionised density fraction was observed to decrease. In the substrate region for a duty cycle below 2% and the whole studied working pressure range, the ionised density fraction always reached at least 50%.

This study explores the microstructural tuning of the AZ91 magnesium alloy subjecting to different heat-treatment procedures to produce the superhydrophobic surface with different adhesive properties. In this regard, a two-step chemical etching process was used to form hierarchical nano/microstructure, during which various phases were corroded with different rates. The surface morphology of samples was characterized using field-emission scanning electron microscopy (FE-SEM) equipped with energy dispersive spectroscopy (EDS) and confocal laser microscopy (CLSM). In addition, the power spectral density (PSD) analysis was employed to evaluate the nano-scale and micro-scale components of the surfaces. The results revealed that the preferential dissolution of the matrix in favor of primary precipitates during etching treatment formed a hierarchical nano/microstructure on the surface of as-cast AZ91 sample and provided petal-type superhydrophobicity. Employing a combination of annealing and aging treatments resulted in a transition from petal to lotus-type superhydrophobicity by redistributing of the β-precipitates in the α-Mg matrix. The mechanism of this transition was discussed in detail, and a direct correlation between the microstructure and the wettability behaviors of AZ91 Mg alloy was established.

In this paper, the hysteresis behaviour of a reactive magnetron sputtering process with oxygen admixture is studied by both experiment and model. The ground state number densities of titanium atoms and ions, and the deposition rates in high power impulse magnetron sputtering discharge were determined for a constant average applied power and pulse duration, while the repetition frequency and reactive gas supply were varied. The hysteresis curve reduced in width and shifted towards the lower oxygen supply with a decrease in the repetition frequency. These experimentally observed trends were well reproduced by a modified Berg model. The presented model utilised measured ionisation fraction of sputtered species and considered the back-attraction of the ionised sputtered species to the target. Significance of the back-attraction process was observed as large fraction of ionised sputtered particles was found to be lost back to the target. This drastically decreased the number of particles deposited onto the substrate, which reduced not only the deposition rate, but also the gettering of the reactive gas. Consequently, the simulated hysteresis curve was shifted and reduced in width as it was observed experimentally.

Nanocomposite nc-TiC/a-C:H coatings exhibit a unique combination of mechanical properties such as high hardness, and low friction and wear. These physical and mechanical properties make those coatings attractive for application in industry. However, the properties of the whole coating/substrate system such as adhesion of the coating to substrate and its response on repeated impact loading known such as dynamic impact wear are also important for industrial applications. Thus, this paper is focused on the adhesion and the dynamic impact wear of nc-TiC/a-C:H coatings prepared by the hybrid PVD-PECVD process. Two series of nc-TiC/a-C:H coatings with a different amount of carbon were deposited onto commonly used industrial cemented tungsten carbide substrates using DC magnetron sputtering (DCMS) and the high power impulse magnetron sputtering (HiPIMS) of a titanium target in argon and acetylene mixture atmosphere. Both series of coatings were analysed using a scratch test and dynamic impact tester with an impact load of 600 N. The HiPIMS prepared coatings exhibited lower thickness and lower thicknesses of the Ti adhesive interlayers between the substrates and coatings than the DCMS prepared coatings. Thus, the adhesion and the impact wear of both series were discussed separately. These properties were discussed with respect to the coating microstructure, phase composition and mechanical properties such as the hardness H, the effective elastic modulus E, and the H/E and H-3/E-2 ratios. The scratch adhesion of coatings depended on the H-3/E-2 ratio and coating microstructure, hardness and surface roughness. The impact wear of the nc-TiC/a-C:H coatings depended on the H/E ratio and coating microstructure.

The aim of this paper is to study the temporal evolutions of sputtered species number densities during a preceding (P) and a subsequent (S) pulse in a multi-pulse HiPIMS. The Ti atom number density does not reach the maximum at the time of the maximal discharge current. It is shown that the residual particles from the P pulse are presented at the beginning of the S pulse even for the longest studied delay between the P and the S pulse. The ionization fractions of sputtered species attained at the end of the S pulses are always lower compared to the P pulse. The coatings produced by multi-pulse HiPIMS exhibited decreased roughness and increased hardness in comparison with standard HiPIMS and DC magnetron sputtered coating.

To gain more information on the temporal and spatial behaviour of self-organized spoke structures in HiPIMS plasmas, a correlation between the broadband optical image of an individual spoke (taken over 200 ns) and the current it delivers to the target has been made for a range of magnetron operating conditions. As a spoke passes over a set of embedded probes in the niobium cathode target, a distinct modulation in the local current density is observed, (typically up to twice the average value), matching very well the radially integrated optical emission intensities (obtained remotely with an ICCD camera). The dual diagnostic system allows the merging and splitting of a set of spokes to be studied as they rotate. It is observed that in the merger of two spokes, the trailing spoke maintains its velocity while the leading spoke either decreases its velocity or increases its azimuthal length. In the spoke splitting process, the total charge collected by an embedded probe is conserved. A simple phenomenological model is developed that relates the spoke mode number m to the spoke dimensions, spoke velocity and gas atom velocity. The results are discussed in the context of the observations of spoke dynamics made by Hecimovic et al (2015 Plasma Sources Sci. Technol. 24 045005).

Nanocomposite coatings consisting of nanocrystallites embedded in an amorphous matrix can be tailored to exhibit unusual combination of properties such as high hardness and modulus combined with low friction and wear. The properties of the coatings are governed by parameters of the deposition plasma, which are a nontrivial function of the deposition process parameters. Energy flux onto the growing films provided by ionized species is one of the key parameters influencing the properties of coatings. This study is focused on the influence of ion flux on the properties of the growing nc-TiC/a-C:H thin film in order to achieve enhanced mechanical properties. Two different magnetic field configurations were used. The saturated ion current on the substrate was found to be seven times higher in the strongly unbalanced magnetic configuration as compared to well-balanced configuration. The deposition temperature was constant at ~ 320 °C, which is higher than the usual temperature for similar depositions of nc-TiC/a-C(:H) coatings. The structure and mechanical properties of the coatings prepared at low or high ion flux were studied and compared. It is concluded that the level of the impinging ion flux in DC magnetron sputtering is not a significant factor influencing the mechanical properties of the coatings in the presented setup.

Titanium–carbon hard coatings were deposited by sputtering using a rotating cylindrical titanium target in an argon/acetylene gas mixture on cemented tungsten-carbide substrates which were placed on a DC-biasable holder to perform a complex rotation around the central rotating cylindrical Ti cathode. While the optimal deposition process parameters to grow the coating of the highest possible hardness and low friction coefficient were sought, the plasma parameters were monitored and correlated with the properties of the deposited coatings. The Ti/Ar line intensity and the cathode voltage exhibited a sudden drop at the conditions for which the maximal hardness was reached. EDX analyses also showed a sudden drop in the atomic concentration of titanium and a sudden increase in that of carbon at the same moment. The maximal hardness of the coating was always achieved at the conditions that preceded these sudden changes, so this phenomenon was used to set the optimal deposition parameters to produce hard, well-adherent and sufficiently thick titanium–carbon coatings using the industrially attractive concept of a rotating cylindrical magnetron.