Pulsed Magnetron Sputtering Research Articles

First Approach to Doping Silver into CrB2 Thin Films Deposited by DC/HiPIMS Technology in Terms of Mechanical and Tribological Properties

Doping of transition metal diborides (TMB2) films with soft metals (Ag, Au, Pt) can extend their application potential to tribological and biomedical fields. Here, a combination of direct current unbalanced magnetron sputtering (DC-UBMS) with high-power pulsed magnetron sputtering (HiPIMS) was used to synthesize silver-doped CrB2+x thin films on unheated substrates. All Ag–CrB2+x thin films were over-stoichiometric with a B/Cr ratio ranging from 2.05 to 2.30 and silver content varying from 3 at.% to 29 at.%. X-ray diffraction demonstrates the amorphous character of the structure in the case of films with silver content ranging from 0 at.% to 8 at.%. A nanocrystalline structure containing a cubic Ag phase is formed in the films with higher silver content. The highest hardness of 26.6 GPa accompanied by the highest value of elastic modulus of 362 GPa was measured in undoped CrB2.3 films. As the silver content in the Ag–CrB2+x thin films increases, the hardness and elastic modulus values gradually decrease to 7.8 GPa and 187 GPa, respectively. The friction properties of CrB2.3 films, expressed by the coefficient of friction against a steel ball of 0.72, are insufficient and limit their use in demanding industrial applications. However, silver doping significantly reduces the friction coefficient when the lowest value of 0.39 is measured in moderately hard Ag–CrB2+x films with an Ag content of 17 at.%. The scratch test shows satisfactory adhesion of films to substrates even without additional heating during deposition.

Influence of the etching process on the coating performance in dry tribological contacts

Physical vapor deposition (PVD) coatings are utilized for wear protection of gears. The use of PVD coatings in unlubricated contacts is also the subject of several research efforts. A promising approach to reduce wear in dry tribological contacts is the combination of MoS2 and WS2 embedded in CrAlN. One possible way to deposit these coatings is the application of High Power Pulse Magnetron Sputtering (HPPMS) process combined with direct current Magnetron Sputtering (dcMS). A challenge by depositing these coatings with an HPPMS/dcMS process is a sufficient adhesion between the coating and the substrate. The present study focuses on the influence of the etching process on the performance of CrAlN + Mo:W:Sg coatings in dry tribological contacts. Before coating deposition, the substrates were pretreated inside the vacuum chamber by different etching processes. During booster etching, which increases the Ar ionization, the substrate bias UB was varied between UB = −150 and UB = −250 V with steps of ΔUB = −50 V. Furthermore, an HPPMS metal ion etching process was used after booster etching at UB = −150 V for these processes. For HPPMS metal ion etching, the number of HPPMS cathodes was varied between one and two. With respect to the etching process, the morphology, surface roughness, compound adhesion by means of the scratch test as well as the coefficient of friction, and the wear volume of the subsequently deposited coatings were investigated. When increasing the substrate bias UB during booster etching, a reduced compound adhesion was found. Moreover, an increased wear volume was observed after pin-on-disk (PoD) tests. For metal ion etching with one activated HPPMS cathode, the wear volume after the PoD test was decreased compared to the pure booster etching processes. When increasing the number of HPPMS cathodes during metal ion etching, the compound adhesion decreased slightly. The wear volume after PoD tests, in contrast, increased. When only using one HPPMS cathode, the lowest wear volume of all investigated coatings was achieved. The present investigations show the potential of tailoring the etching process in order to increase the performance of PVD coatings. A customized HPPMS metal ion etching process can be used to improve the properties of well-established hard PVD coatings.

Effect of technological parameters of the process of pulsed magnetron sputtering on the structure and phase composition on TiN-based coatings

Subject of research: coatings based on TiN deposited by pulsed magnetron sputtering have been studied.
 Purpose of research: is to establish the effect of technological parameters of the process of pulsed magnetron sputtering: the discharge current and the N2 content in the vacuum chamber on the structure and phase composition of coatings based on TiN.
 Methods and objects of research: the phase composition and structural characteristics of the TiN-based coating were studied in the course of X-ray diffraction and X-ray phase analysis of coatings. The microstructure of the formed coatings based on TiN was studied using scanning electron microscopy. The object of the study were samples of VK6 hard alloy with TiN coatings.
 Main results of research: it has been established that the magnitude of the discharge current has the greatest influence on the formed structure of the TiN coating. An increase in the content of N2 and the discharge current leads to a change in the phase composition and the formation of a single-phase coating based on the (111) c-TiN cubic phase with an increase in the degree of texture of the coating. The optimal values ​​of technological parameters are determined at which a coating based on the c-TiN phase is formed, with a minimum level of internal stresses, the smallest grain size, and a dense, columnar structure.

Formation of pure anatase TiO2 using the reactive pulsed dc magnetron sputtering method for controlling the target poisoning state

AbstractThe use of pulsed dc‐sputtering sources for reactive magnetron sputtering with oxygen offers a possibility to suppress the negative effects of target poisoning (such as arcing). This results in a wide process range for the selection of a desired operating point. The control of target poisoning plays a major role in maintaining constant coating properties and affects the stoichiometry of the reactive coating, as well as the coating rate and the economic impact of the coating process. In a hysteresis, the target poisoning during the reactive sputtering of titanium under oxygen addition proceeds nonlinearly. Without the use of a suitable target poisoning control technique, the sputtering process can abruptly change to an unstable state. As a result, variations of stoichiometry can occur during the deposition process. A proven method for maintaining a stable reactive sputtering process is the control of oxygen flow with the input variable target voltage. By determining the typical oxygen hysteresis at constant target power and constant argon flow, an operating point for the control loop is derived. The desired target voltage then serves as the input variable for the control loop of the target poisoning. The controlling technique for target poisoning is a basic requirement for the production of the photolytic active anatase phase of titanium dioxide (TiO2) using reactive magnetron sputtering. The photocatalytic equipment of surfaces with a titanium dioxide coating in the anatase phase can be realized with the reactive pulsed dc magnetron sputter ion plating process (DC‐MSIP). The pulsed DC‐MSIP process facilitates coating a variety of surfaces at temperatures below 200°C in an environmentally friendly manner.

A Comparative Investigation on the Microstructure and Thermal Resistance of W-Film Sensor Using dc Magnetron Sputtering and High-Power Pulsed Magnetron Sputtering

Traditional dc magnetron sputtering has a low ionization rate when preparing metallic thin films. With the development of thin film science and the market demand for thin film material applications, it is necessary to improve the density of magnetron-sputtered films. High-power pulsed magnetron sputtering (HiPIMS) technology is a physical vapor deposition technology with a high ionization rate and high energy. Therefore, in this work, HiPIMS was applied to prepare metallic tungsten films and compare the surface morphology and microstructure of metallic tungsten films deposited using HiPIMS and dc magnetron sputtering (dcMS) technology under different pulse lengths, as well as related thermal resistance performance, followed by annealing treatment for comparative analysis. We used AFM, SEM, XRD, and plasma characterization testing to comprehensively analyze the changes in the TCR value, stability, repeatability and other related performance of the metallic tungsten thin-film sensor deposited by the HiPIMS technology. It was determined that the thin film prepared by the HiPIMS method is denser, with fewer defects, and the film sensor was stable. The 400 °C annealed sample prepared using HiPIMS with a 100 μs pulse length reaches the largest recorded TCR values of 1.05 × 10−3 K−1. In addition, it shows better stability in repeated tests.

Ion kinetic energy- and ion flux-dependent mechanical properties and thermal stability of (Ti,Al)N thin films

Ion-irradiation-induced changes in structure, elastic properties, and thermal stability of metastable c-(Ti,Al)N thin films synthesized by high-power pulsed magnetron sputtering (HPPMS) and cathodic arc deposition (CAD) are systematically investigated by experiments and density functional theory (DFT) simulations. While films deposited by HPPMS show a random orientation at ion kinetic energies (Ek)>105 eV, an evolution towards (111) orientation is observed in CAD films for Ek>144 eV. The measured ion energy flux at the growing film surface is 3.3 times larger for CAD compared to HPPMS. Hence, it is inferred that formation of the strong (111) texture in CAD films is caused by the ion flux- and ion energy-induced strain energy minimization in defective c-(Ti,Al)N. The ion energy-dependent elastic modulus can be rationalized by considering the ion energy- and orientation-dependent formation of point defects from DFT predictions: The balancing effects of bombardment-induced Frenkel defects formation and the concurrent evolution of compressive intrinsic stress result in the apparent independence of the elastic modulus from Ek for HPPMS films without preferential orientation. However, an ion energy-dependent elastic modulus reduction of ∼18% for the CAD films can be understood by considering the 34% higher Frenkel pair concentration formed at Ek=182 eV upon irradiation of the experimentally observed (111)-oriented (Ti,Al)N in comparison to the (200)-configuration at similar Ek. Moreover, the effect of Frenkel pair concentration on the thermal stability of metastable c-(Ti,Al)N is investigated by differential scanning calorimetry: Ion-irradiation-induced increase in Frenkel pairs concentration retards the wurtzite formation temperature by up to 206 °C.

Studies of Electrical Parameters and Thermal Stability of HiPIMS Hafnium Oxynitride (HfOxNy) Thin Films

This work demonstrated the optimization of HiPIMS reactive magnetron sputtering of hafnium oxynitride (HfOxNy) thin films. During the optimization procedure, employing Taguchi orthogonal tables, the parameters of examined dielectric films were explored, utilizing optical methods (spectroscopic ellipsometry and refractometry), electrical characterization (C-V, I-V measurements of MOS structures), and structural investigation (AFM, XRD, XPS). The thermal stability of fabricated HfOxNy layers, up to 800 °C, was also investigated. The presented results demonstrated the correctness of the optimization methodology. The results also demonstrated the significant stability of hafnia-based layers at up to 800 °C. No electrical parameters or surface morphology deteriorations were demonstrated. The structural analysis revealed comparable electrical properties and significantly greater immunity to high-temperature treatment in HfOxNy layers formed using HiPIMS, as compared to those formed using the standard pulsed magnetron sputtering technique. The results presented in this study confirmed that the investigated hafnium oxynitride films, fabricated through the HiPIMS process, could potentially be used as a thermally-stable gate dielectric in self-aligned MOS structures and devices.

Effects of gradient structure and modulation period of Ta/TaN/Ta(C,N)/Ta-DLC multilayer coatings prepared by HiPIMS

Hard coatings, such as nitride, carbide and diamond-like carbon (DLC), have been applied to improve the tribological resistance by forming multilayer or gradient structures. In this study, Ta/TaN/Ta(C,N)/Ta-DLC coatings in gradient content and multilayer structure with different modulation periods were prepared by high-power pulsed magnetron sputtering (HiPIMS). The effect of the modulation period on the microstructure, mechanical and tribological properties was evaluated. The average grain size of the coatings first increased from 15.2 to 17.1 nm and then decreased to 9.9 nm with decreasing modulation period from 1220 to 153 nm. Ta-DLC layer is homogeneously composed of TaC crystals and amorphous carbon. The design of the gradient structure makes the multilayer interface unclear, and the interlayer interdiffusion is obvious. The reduction of the modulation period effectively improved the adhesion strength of the multilayer coating on the substrate. The multilayer coating with a modulation period of 305 nm obtained the highest hardness of 24.5 ± 0.8 GPa and Young's modulus of 263.2 ± 16.6 GPa. Compared with single-layer TaN, Ta/TaN/Ta(C,N)/Ta-DLC multilayer gradient coating had dramatically improved tribological properties, exhibiting the lowest friction coefficient of 0.15 and the lowest wear rate of 2.47 × 10−12 m3N−1 m−1 when the modulation period is 305 nm. By combining a Ta-doped DLC layer with a low friction coefficient and a TaN layer with high hardness, the multilayer gradient coating achieved excellent mechanical and tribological properties.

Super effective antimicrobial silver-sputtered coatings on poly(lactic acid) against bacteria and omicron SARS-CoV-2

Poly(lactic acid) (PLA) is a biopolymer with properties potentially suitable for fabricating packaging, medical devices, and healthcare products in a more friendly environmental way because this polymer presents biodegradability, compostability, low carbon footprint, and recyclability. However, PLA does not present intrinsic antimicrobial properties. Antimicrobial materials are highly desirable for manufacturing smart packaging and personal protective equipment to secure food and health professionals against pathogenic microorganisms. In this work, we evaluated the antimicrobial performance of (Ag)-coated PLA against Escherichia coli, Bacillus subtilis, and Omicron severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). PLA was rapidly coated with metallic Ag by pulsed direct current magnetron sputtering (pDCMS) for 5, 10, and 20 s. Atomic force microscopy indicates that the Ag coating grows predominantly on the PLA surface via a bulk diffusion mechanism. According to bactericidal and quantitative reverse transcription polymerase chain reaction assays, Ag-coated PLA was capable of inhibiting bacterial biofilm formation and disrupting the genetic material of the Omicron SARS-CoV-2. X-ray high-resolution photoelectron and nuclear magnetic resonance results suggest no polymer chain scission in the PLA bulk due to plasma thermal stress effects during Ag sputtering.

Bilayer molybdenum contact prepared via high-power pulsed magnetron sputtering: Effects of substrate bias

Molybdenum (Mo) is widely used to fabricate the back contact of compound semiconductor thin film solar cells. Most of those contacts are deposited using direct current (DC) or radio frequency (RF) sputtering; however, those processes are ill-suited to achieving low resistance with good adhesion. In this study, we sought to overcome this issue using high-power pulsed magnetron sputtering (HiPIMS) with a focus on the effects of substrate bias on adhesion and resistance. When used with a HiPIMS power source, substrate bias was shown to promote the (110) preferred orientation of the top Mo contact, while reducing the (211) preferred orientation of the bottom Mo contact. This resulted in the lowest recorded resistivity (9.7 μΩ cm) when the bottom was deposited without bias and the top Mo contact was biased at −40 V.

Reactive pulsed direct current magnetron sputtering deposition of semiconducting yttrium oxide thin film in ultralow oxygen atmosphere: A spectroscopic and structural investigation of growth dynamics

An experimental investigation was conducted to explore spectroscopic and structural characterization of semiconducting yttrium oxide thin film deposited at 623 K (±5K) utilizing reactive pulsed direct current magnetron sputtering. Based on the results obtained from both x-ray diffraction and transmission electron microscope measurements, yttrium monoxide is very likely formed in the transition region between β-Y2O3 and α-Y2O3, and accompanied by the crystalline Y2O3. Resulting from either the low energy separation between 4d and 5s orbitals and/or different spin states of the corresponding orbitals’ sublevels, the stability of monoxide is most presumably self-limited by the size of the crystal in thermodynamic terms. This behavior develops a distortion in the structure of the crystal compared to the metal oxide cubic structure and it also effectuates the arrangement in nanocrystalline/amorphous phase. In addition to this, spectroscopic ellipsometry denotes that the semiconducting yttrium oxide has the dominant, mostly amorphous, formation character over crystalline Y2O3. Our purpose, by means of the current findings, is to advance the understanding of formation kinetics/conditions of yttrium with an unusual valency (2+).

Dry Friction Performances of MoNx Coatings Deposited by High–Power Pulsed Magnetron Sputtering

A MoNx coating serves as an effective wear protection layer and is crucial for the investigation of its tribological characteristics at various temperatures. This study examined the tribological characteristics of MoNx coatings that were deposited through high-power pulsed magnetron sputtering (HiPIMS) in an Ar/N2 environment with varying N2 partial pressures. The microstructures and mechanical properties of the coatings were elucidated using scanning electron microscopy, grazing-incidence-angle X-ray diffraction, energy-dispersive spectroscopy, and nanoindentation. The dry friction performances of the coatings at different heating temperatures were studied using a ball-on-disk tribometer. The MoNx coating produced by HiPIMS was composed primarily of fcc−Mo2N and featured a fine, dense column crystal with a maximum hardness of 28.8 GPa. The MoNx coatings exhibited excellent lubrication and wear reduction properties at room temperature (RT). The dry friction performances of the MoNx coatings at elevated temperatures were expected to depend on the growth of the MoO3 tribolayer. At relatively low temperatures (300 °C and 400 °C), the MoO3 tribolayer grew slowly and was not enough to provide good lubrication, causing increases in the dry friction of the coatings. However, the δ−MoN phase formed in the MoNx coating deposited at a high N2 partial pressure could facilitate the formation of MoO3 and thus decreased the friction coefficient at 400 °C. At the relatively high heating temperature of 500 °C, however, the MoO3 tribolayer grew so rapidly that the oxide layer became thick, resulting in an increase in the wear rate. It is believed that tuning the growth rate of MoO3 via optimizing the composition and structure of the MoNx coatings might be a useful way to improve the dry friction at various elevated temperatures.

High temperature steam oxidation behavior of textured Cr coatings with different grain structures

In order to improve the oxidation resistance of Zr-4 alloy in high temperature steam environment, Cr coatings with the 〈001〉 fiber texture were prepared on Zr-4 substrates by the high-power pulsed magnetron sputtering (HIPPMS) and direct current magnetron sputtering (DCMS) methods, and their structure and high temperature steam oxidation behavior at 1200 and 1300 °C were systematically investigated. The results showed that the fine grains of Cr coatings combined together to form large grains while the texture of the coatings was not changed during oxidation. Furthermore, cracks or defects formed during the combination of grain boundaries in the grain growth of DCMS Cr coating, providing paths for short-circuit diffusion of the oxidizing medium, which accelerated the oxidation of the Cr coating.

Advances in Preparation Technology of Tool Coatings

With the continuous development of modern industry and the difficult-to-machine materials gradually increases, the machining requirements of cutting tools continue to improve and the cutting environment is increasingly harsh. As the coating applies, the efficiency and precision of machining have been effectively improved. Coating on the tool surface can not only extend the service life of the cutting tool, greatly reduce the processing cost, but also reduce the environmental pollution in the process of processing. Excellent coating preparation technology is an important factor for its effective performance. According to different processing requirements, processing costs and processing environment, researchers have been working hard on the road of coating preparation technology. In this work, it summarizes the principle of physical vapor deposition, chemical vapor deposition and the corresponding advantages and disadvantages, and briefly introduces the pulsed DC magnetron sputtering, high power pulsed magnetron sputtering, arc ion plating and a variety of composite magnetron sputtering technologies.

Advances and Challenges in Pulsed Laser Deposition for Complex Material Applications

Various physical vapor deposition (PVD) techniques, such as molecular beam epitaxy, electron beam physical vapor deposition, pulsed laser deposition (PLD), arc discharge, magnetron sputtering and/or ion beam sputtering, are currently used for coating or growing thin films on solid substrates [...]

Properties of Multilayered CrN/VN Films Prepared Using a Hybrid System of High-Power Impulse Magnetron Sputtering and Pulsed Magnetron Sputtering

Nanomultilayered chromium nitride (CrN)/ vanadium nitride (VN) films with different layer thicknesses were synthesized on Si substrates using a hybrid system of reactive high-power impulse magnetron sputtering (HiPIMS) and pulsed magnetron sputtering. The microstructure and properties of the nanomultilayered CrN/VN films were investigated using X-ray diffraction (XRD), transmission electron microscopy (TEM), the nanoindentation method, and the friction wear test. The XRD results showed that the multilayered films exhibited nanocrystallite structure with a (200) preferred orientation, and the estimated crystallite size was not highly dependent on the CrN and VN layer thicknesses. Inserting the VN layers decreased the compressive stress slightly compared to that of the CrN monolayer film and increased the hardness by 4-5 GPa compared to that of the CrN and VN monolayer films. The friction coefficient of the multilayered films strongly depended on the CrN layer thickness rather than on the VN layer thickness.

Properties of CrN/TiN Multilayer Films With Nanoscale Layer Thickness

Chromium nitride (CrN)/titanium nitride (TiN) multilayer films at nanoscale layer thickness were prepared using a combination of reactive high-power impulse magnetron sputtering (HiPIMS) and pulsed magnetron sputtering. Each layer thickness was adjusted by controlling each deposition time. The hardness and Young’s modulus of the multilayer films, which were measured using nanoindentation technique, did not vary significantly with layer thickness. The film hardness ranged between 22 and 24.5 GPa, and the Young modulus was between 300 and 330 GPa. On the contrary, the compressive stress of the multilayer films gradually decreased with the increase in the TiN layer thickness. The friction coefficient of the multilayer film did not depend on the CrN layer thickness, but it reduced drastically to 0.2–0.3 with the increase in the TiN layer thickness in the range of the TiN layer thickness less than about 2 nm.

Microstructure and Mechanical Properties of TiN/Ti2AlN Multilayers

Titanium nitride (TiN) thin films deposited by high-power pulsed magnetron sputtering usually have a high compressive residual stress, which is not conducive for the adherence of TiN thin films. This study investigated the potential of Ti2AlN for releasing the compressive residual stress of HPPMS-deposited TiN thin films and evaluated the adherence strength and hardness of TiN/Ti2AlN multilayers by introducing the Ti2AlN MAX phase to form TiN/Ti2AlN multilayers. The results showed that smooth TiN/Ti2AlN multilayers with the TiN (111) and Ti2AlN (002) textures were successfully synthesized by HPPMS deposition and subsequent vacuum annealing. The compressive residual stress in TiN was released by Ti2AlN. The adherence strength of the TiN/Ti2AlN multilayers was improved after the release of the compressive residual stress, and the hardness of TiN/Ti2AlN multilayers was close to the annealed TiN. This study provides a novel approach for releasing the residual stress of hard ceramic thin films using the MAX phase.

Multilayer thin films of aluminum oxide and tantalum oxide deposited by pulsed direct current magnetron sputtering for dielectric applications

This research describes the synthesis of multilayer thin films of aluminum oxide and tantalum oxide for dielectric applications. The multilayer thin films are made of two, four, or eight oxide layers produced by physical vapor deposition (PVD), specifically mid-frequency pulsed direct current magnetron sputtering. The oxide layers are stoichiometric Al2O3 and Ta2O5 with two specific morphologies observed from cross-section images obtained by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The Al2O3 layers exhibit a columnar structure whereas the Ta2O5 layers are uniform and dense. However, the morphology of the Ta2O5 layers changes progressively in the four-layer and eight-layer systems under the influence of the morphology of the Al2O3 layer below. This behavior is induced by the morphological continuity of the interface between two oxide layers. X-ray diffraction (XRD) shows the low crystallinity of these oxide layers due to the experimental conditions used during the magnetron sputtering process, particularly the low deposition temperature. The dielectric behavior of the multilayer thin films is studied by dielectric strength measurements. The results are compared to the values obtained for single layers of Al2O3 and Ta2O5 produced under the same experimental conditions. The two-layer system shows an intermediate value compared to the single layers, higher than Al2O3 and lower than Ta2O5. The dielectric strengths of the four-layer and the eight-layer systems are higher than those measured for the single layers of Al2O3 and Ta2O5. Finally, the morphology and the crystallinity of the multilayer thin films are changed by thermal annealing of these samples at 850 °C under vacuum. The thermal annealing induces crystallization of the Ta2O5 layers and the loss of morphological continuity at the interface between the oxide layers. These modifications result however in a lower dielectric strength for all the multilayer thin films.

Epitaxial growth of high-quality yttria-stabilized zirconia films with uniform thickness on silicon by the combination of PLD and RF sputtering

High-quality (100)-oriented yttria-stabilized zirconia (YSZ) films with uniform thickness were epitaxially grown on silicon substrates by a two-step process of pulsed laser deposition (PLD) and radio-frequency magnetron sputtering (RFS). First, we fabricated a YSZ-seed layer on (001)-oriented silicon substrates using a PLD apparatus, and then transferred the YSZ-seed substrate to an RFS equipment to complete the growth of a thicker YSZ film. The dependence of YSZ crystal quality on RFS-growth temperature was investigated in the range of 200 to 850 °C. All the resulting YSZ films exhibited pure (100) orientation, and the full width at half maximum of the YSZ (200) X-ray rocking curve was as low as 0.64° for the YSZ film grown at 850 °C, and increased to 1.02° with the RFS-growth temperature declining to 200 °C. The results evidenced that the YSZ film can be epitaxially grown at 200 °C in the presence of a YSZ-seed layer. However, the splitting of the YSZ (200) X-ray diffraction peak appeared at 500 °C and 200 °C, which may be attributed to a transformation of the intrinsic stress in the YSZ films from compressive to tensile stress with decreasing temperature. In addition, the YSZ film had a uniform thickness distribution with an inhomogeneity of less than 5 % and a very flat and dense surface with root-mean-square surface roughness below 1 nm.