Magnetron Sputtering System Research Articles

Fatigue and tensile behaviour of Ti+TiN+Ti+TiVN multilayer nitride films coated on AZ91 magnesium alloy by closed field unbalanced magnetron sputtering

Despite their extensive use in the automotive and aerospace industries, Mg and Mg alloys, which are light metals, exhibit low fatigue and tensile strength. In this study, transition metal-nitride (TMN) multilayer coatings (Ti+TiN+Ti+TiVN) were coated twice on AZ91 Mg alloy using a Confined Field Unbalanced Magnetron Sputtering (CFUBMS) system to increase fatigue and tensile strength. The structural properties of the films were analyzed by using X-ray diffraction (XRD), scanning electron microscope (SEM), and energy dispersive spectrometry (EDS) methods, and the mechanical properties were analyzed by rotating bending fatigue and tensile testing machines. Ti+TiN+Ti+TiVN multilayer nitride surface coatings on AZ91 Mg alloys showed a dense and columnar microstructure and according to XRD results (111) was the preferred orientation with the dominant peak. The fatigue limit value of the AZ91 base material was fixed at 60.46 MPa, while it increased to 68.48 MPa after being coated with multilayer nitride. Along with the multilayer nitride coating, the tensile strength increased from 169.98 MPa to 175.43 MPa. As a result, the multilayer hard nitride coating with low surface roughness, which fills the defects, notches, and voids on the surface of the AZ91 base material, increased the fatigue and tensile strength in parallel. Based on the outcomes of the research, the literature has been enriched with an innovative approach through the enhancement of fatigue and tensile strengths by applying a CFUBMS coating to lightweight metals and alloys, such as AZ91, especially in the transportation industry where lightness and dynamic load resistance are essential.

High pH stability and detection of α-synuclein using an EGFET biosensor with an HfO2 gate deposited by high-power pulsed magnetron sputtering

In this research, hafnium oxide (HfO2) was first fabricated in an in-house-developed high-power pulsed magnetron sputtering system (HiPIMS) functionalized for application as a high-performance extended gate field-effect transistor (EGFET) for the detection of pH and proteins associated with Parkinson's disease (PD). PD is the second most common neurodegenerative disease in elderly people after Alzheimer's disease. The α-synuclein protein in patients’ blood may be a potential biomarker in the early stage of PD. Detection of α-synuclein with high sensitivity and nonspecific binding through HfO2-EGFET biosensors has the advantages of low cost and simple fabrication from disposable EGs. Among the duty cycle conditions tested, HfO2 deposited at a 25% duty cycle in HiPIMS exhibited superior pH sensitivity and linearity, with values of 56.4 mV/pH and 99.7%, respectively. The hysteresis width and drift coefficient are −3 mV and 0.3 mV/h, respectively. To overcome the Debye length limitation, 100-fold diluted phosphate buffer solution and the PMOS configuration were used to determine the α-synuclein for which the isoelectric point was 4.67. The negative gate bias in the PMOS configuration successfully causes α-synuclein to approach the surface of HfO2 EG to achieve a sensitivity of 12.1 mV/dec and a linearity of 99.5% in the range of 0.1–1000 pg/mL. The limit of detection is 0.198 pg/mL, and the immobilized surface ultimately binds specifically, resulting in low interference signals from other related biomarkers. This promising study shows that detecting various proteins involved in different diseases and performing clinical tests can be accomplished in the future.

Tribology performance of diamond-like carbon films on polyether-ether-ketone surfaces

Diamond-like carbon films were deposited on the polymer PEEK surface using a magnetron sputtering system. Experiments were conducted under varying rotational friction speed conditions. Special attention was devoted to assessing the surface condition of spherical spots post-friction experiments. Optical microscopy, friction tester, Raman spectroscopy, XPS analysis, and atomic force microscopy were employed to examine film surface morphology, atomic bonding structure, and surface roughness. The results indicate that thin film wear trace exhibits a graphitization trend that increases and then decreases, peaking around 350 rpm (0.11 m/s). Conversely, for spherical spots, the graphitization pattern is the opposite, suggesting a higher degree of disorder in the transferred film on these spots. XPS analysis reveals multiple chemical bonding structures between carbon and oxygen elements on the spherical spots. Notably, under the optical microscope, spherical spots exhibit clear directional alignment, which is absent on the film surface. This study introduces an innovative approach for producing diamond-like carbon films with lubricating and anti-wear properties. It also provides guidance for designing high-performance polymer tribo-systems in industrial applications.

Investigation of hardness, tribological and adhesion properties of TiAlNiVN HEA films heat treated at different temperatures

TiAlNiVN high entropy alloy (HEA) films were firstly produced in the literature using the magnetron sputtering system. These films were subjected to heat treatments at different temperatures between 750 °C and 900 °C. Strong TiN and VN crystal structures were observed in all the annealed films. The composition of each element constituting TiAlNiVN HEA films was within a concentration range of 5–35 %. The presence of TiAlNiVN HEA films was confirmed by X-ray photoelectron spectroscopy (XPS) analysis. D-850 film had the highest hardness of 25.7 GPa and exhibited the lowest wear rate at 2.45 × 10−5 mm3/(N.m), attributable to its lowest surface roughness (0.22) and friction coefficient (0.44). Subsequent to the heat treatment, there was a substantial enhancement in the adhesion performance of the films, culminating in a high critical load value of 80 N. This study revealed that nitride-based TiAlNiVN HEA films could be enhanced in terms of hardness, tribological, and adhesion properties after heat treatment. Considering the adhesion performance, it is anticipated that the films we have produced will be a promising alternative to traditional nitride-based coatings in challenging and complex service conditions.

Study on Microstructure and Tribological Mechanism of Mo Incorporated (AlCrTiZr)N High-Entropy Ceramics Coatings Prepared by Magnetron Sputtering.

(AlCrTiZrMox)N coatings with varying Mo content were successfully prepared using a multi-target co-deposition magnetron sputtering system. The results reveal that the Mo content significantly affects the microstructure, hardness, fracture toughness, and tribological behavior of the coatings. As the Mo content in the coatings increases gradually, the preferred orientation changes from (200) to (111). The coatings consistently exhibit a distinct columnar structure. Additionally, the hardness of the coatings increases from 24.39 to 30.24 GPa, along with an increase in fracture toughness. The friction coefficient is reduced from 0.72 to 0.26, and the wear rate is reduced by 10 times. During the friction process, the inter-column regions of the coatings are initially damaged, causing the wear track to exhibit a wavy pattern. Greater frictional heat is generated at the crest of the wave, resulting in the formation of a MoO2 lubricating layer. The friction reaction helps to reduce the shear force during friction, demonstrating the lower friction coefficient of the (AlCrTiZrMox)N coatings. Both the hardness and fracture toughness work together to reduce the wear rate, and the (AlCrTiZrMox)N coatings show excellent wear resistance. Most notably, although the columnar structure plays a negative role in the hardness, it contributes greatly to the wear resistance.

Overall aspect for designing magnetron sputtering plasma sources and their applications in the deposition of ITO films

This work reports a systematic review of the studies of magnetron sputtering (MS) discharges and their utilities for the deposition of transparent coating oxide thin films like indium tin oxides (ITOs). It collates the overall information of plasma science, diagnostics, and chemistry and their usefulness in controlling the plasma process, film growth, and properties. It discusses studies on various MS systems and their capabilities and reports scientific aspects like the formation of instability and plasma flares to understand the various discharge phenomena. The study also discusses various issues, progress, and challenges in ITO films for industrial applications. In addition, this work highlights the importance of plasma parameters and energy flux on thin film growth and film properties.

Large area MoSe2 and MoSe2/Bi2Se3 films on sapphire (0001) for near-infrared photodetection

The fabrication of heterojunction-based photodetectors (PDs) is well known for the enhancement of PDs performances, tunable nature of photoconductivity, and broadband application. Herein, the PDs based on MoSe2 and MoSe2/Bi2Se3 heterojunction on sapphire (0001) substrates were deposited using a r.f. magnetron sputtering system. The high-resolution x-ray diffraction and Raman spectroscopy characterizations disclosed the growth of the 2-H phase of MoSe2 and the rhombohedral phase of Bi2Se3 thin films on sapphire (0001). The chemical and electronic states of deposited films were studied using x-ray photoelectron spectroscopy and revealed the stoichiometry growth of MoSe2. We have fabricated metal-semiconductor–metal type PD devices on MoSe2 and MoSe2/Bi2Se3 heterojunction and the photo-response measurements were performed at external voltages of 0.1–5 V under near-infrared (1064 nm) light illumination. The bare MoSe2 PD device shows positive photoconductivity behavior whereas MoSe2/Bi2Se3 heterojunction PD exhibits negative photoconductivity. It was found that the responsivity of MoSe2 and MoSe2/Bi2Se3 heterojunction PDs is ~ 1.39 A W−1 and ~ 5.7 A W−1, respectively. The enhancement of photoresponse of MoSe2/Bi2Se3 PD nearly four-fold compared to bare MoSe2 PD shows the importance of heterojunction structures for futuristics optoelectronic applications.

Influence of silicon content on high temperature tribology performance of TiAlCrSiN coatings

A series of TiAlCrSiXN coatings with various silicon contents were fabricated on Si(100) and 304 stainless steel substrates using a radiofrequency magnetron sputtering system, aiming to examine the effects of various Si content on wear behaviors at room temperature and 700 °C. The addition of silicon notably increased the coatings' hardness from 21 GPa to 29 GPa, attributed to significant compressive residual stress (−3.4 GPa) that inhibited dislocation movement. Room temperature wear tests revealed that wear rates varied between 0.6 and 3.7 (10−6mm3N−1 m−1) with increasing silicon content. The lowest wear rate is observed at a silicon content of 3.1 at.%, which is associated with an ideal residual stress of −1.2 GPa. This stress level played a crucial role in preventing crack propagation and delamination, thus enhancing wear protection. At 700 °C, the coatings' wear resistance was mainly governed by their oxidation resistance, with the most resistant coatings exhibiting wear rates from 1.6 to 4.4 (10−6mm3N−1 m−1). The silicon addition promoted the formation of an amorphous Si3N4 phase, serving as an oxygen diffusion barrier, thus enhancing resistance to oxidation at elevated temperatures. The findings suggest that TiAlCrSiN coatings offer a promising solution for advanced tribological applications, demonstrating improved performance at temperatures up to 700 °C.

Microstructure and mechanical properties of Cr films with different orientations before and after plasma nitriding

In this paper, the Cr films with preferred orientation evolution from (110) to (200) were deposited on the surface of austenitic stainless steel. These films were driven by a pulsed bias with different duty cycles from 20% to 80%, followed by a postnitriding process for 1 h using a hot wire plasma-enhanced magnetron sputtering system. XRD result showed Cr film had a body-centered cubic lattice structure, and the orientation transformed from (110) to (200) with the increase in the duty cycle. SEM and EDS measurements revealed that Cr film structured with columnar crystals could contribute to the continuous diffusion of nitrogen into austenite lattice. N atoms tended to diffuse along the (200) orientation of Cr films than the close-packed (110) orientation. As a result, the best wear resistance and adhesion strength were obtained when Cr film deposited at 80% duty cycle was nitrided, and the wear volume decreased by 95.7% compared with that before nitriding.

Fabrication of (TiZrNbSiMo)1-xNx high entropy alloy coatings using a high power impulse magnetron sputtering technique: Effects of nitrogen addition

Due to the outstanding mechanical and physical properties of high entropy alloy (HEA) coatings, the global academic and industrial communities have made significant research efforts in recent years, aiming to expand their industrial applications. In this study, TiZrNbSiMo and (TiZrNbSiMo)1-xNx HEA nitride coatings with different nitrogen contents were fabricated using a high power impulse magnetron sputtering (HiPIMS) system. By varying the nitrogen flow rates, the nitrogen contents of coatings increased from 0 to 48.8 at. %. The deposition rate decreased with increasing nitrogen content due to the target poisoning effect. Very fine and dense microstructure can be seen for each coating. The amorphous structure was obtained as the nitrogen content was lower than 19.1 at.%, whereas a nanocrystalline FCC structure was formed when the nitrogen content reached 34.9 at. %. Furthermore, the corrosion resistance of TiZrNbSiMo and four TiZrNbSiMoN HEA coatings in 0.5 M H2SO4 aqueous solution were superior to uncoated 304 stainless steel. We can conclude that the nanocrystalline TiZrNbSiMoN HEA coatings with a nitrogen content of 34.9 at. % exhibited a high hardness of 15.6 GPa, an electrical resistivity of 766.5 μΩ·cm, and an excellent corrosion polarization resistance of 9.71 × 105 Ω·cm2, 610.7 times higher than 304SS. This study provides valuable insights for future promising applications of (TiZrNbSiMo)1-xNx HEA nitride coatings in severely corrosive environments, such as the protective coatings on stainless steel bipolar plates in proton exchange membrane fuel cells.

Application of honeycomb pattern to Ti2AlN MAX phase films by plasma etching

The honeycomb pattern possesses a distinctive hexagonal structure capable of seamless repetition on a flat surface, leaving no gaps. Moreover, all arm thicknesses and angles are equal to one another. This remarkable configuration is deemed biomimetic, with numerous examples found in nature. Notably, it exhibits remarkably low density and exceptional mechanical strength. MAX phase films have gathered significant attention due to their exceptional capacity to amalgamate the essential properties of both metals and ceramics. Additionally, they possess the unique ability to effectively mend surface cracks that may arise as a result of friction-wear, restoring the material to a certain degree of integrity. In this study, Ti2AlN MAX phase thin films were deposited on M2 steel substrates by a closed field unbalanced magnetron sputtering system (CFUBMS). 750 °C heat treatment was applied to obtain the produced films in crystalline form. In addition, plasma etching parameters suitable for the phase structure of the deposited film were determined. With the inductive coupling plasma etching (ICP) process, the honeycomb pattern was given to the Ti2AlN MAX phase films with a continuous and smooth geometry at a depth of 2 μm. This study gives ideas for the development of multi-coating systems in which patterns of different geometries are included in a single layer.

Study on the process of hydrogen-doped indium oxide for silicon heterojunction solar cell mass production

In this work, we conducted a comparative study on water vapor (H2O) process and hydrogen gas (H2) process to prepare the IMO:H films based on industrialized DC magnetron sputtering system. To dynamically control the residual H2O pressure, we installed a set of polycold coil and kept it turned on during the sputtering process. The film characteristics of Hall mobility, carrier density, sheet resistance, and transparency was investigated. The results revealed that the silicon heterojunction (SHJ) solar cell with H2 process had a higher Hall mobility and greater transparency in the 400–600 nm wavelength range resulting in a lower contact resistivity and a slight increase current density compared to the H2O process. The median efficiency (Eff) achieved with the H2 process improved by 0.09% absolute to 25.43%, mainly because of the increased Jsc and FF. And the IMO:H films with H2 process had a large basal spacing with (400) and (222) crystal planes resulting in maintaining a more stable and reliable structure at temperatures below 200 °C. After the optimization of TCO layer process, we manufactured the industrial-grade SHJ cells with max efficiency (Eff), Voc, Jsc, and fill factor (FF) values as high as 26.27%, 753 mV, 41 mA/cm2, and 86%, respectively. The IMO:H films with H2 process can thus be considered more suitable for large-scale production.

Effect of substrate bias on the formation of nanotwin and properties in Cu thin films for advanced packaging technology

Materials with nanotwinned structures have drawn much attention due to their unique properties. The high-density nanotwinned Cu films are generally deposited at room temperature with high deposition rate. In this study, we report nanotwins can be formed in the Cu films at 150 °C with the aid of the ion bombardment effect caused by applied substrate bias. Cu thin films were deposited on Si (100) substrate by the unbalanced magnetron sputtering system using different applied substrate biases ranging from 0 V to −160 V. The results show that, with a suitable applied substrate bias of −120 V, the twinning density of the Cu films can reach over 80 % and exhibit a high hardness of 3.1 GPa. This study provides a concept to tailor the microstructure of the sputtered Cu films by tuning applied substrate biases and realizing the mechanism of substrate bias on the twin formation during deposition.

Adhesive properties of deposited Cu films on colorless polyimide using high power impulse magnetron sputtering system

This study explores the deposition of copper (Cu) films onto colorless polyimides (PIs) using the High Power Impulse Magnetron Sputtering (HiPIMS) technique. The impact of varying operating duty cycles and frequencies on sheet resistance, the deposition rate of Cu films, and the adhesion strength between Cu and PI is examined. Adjusting the HiPIMS parameters aims to achieve superior film quality with reduced sheet resistance. Furthermore, post-thermal treatment significantly improves the adhesion of the Cu layer to the PI substrate due to the mechanical interlocking mechanism created by the surface roughness of the PI and the chemical bonding between the two components.

Performance Improvement of a ZnGa2O4 Extended-Gate Field-Effect Transistor pH Sensor.

ZnGa2O4 sensing films were prepared using an RF magnetron sputtering system and connected to a commercial metal oxide semiconductor field-effect transistor (MOSFET) as the extended-gate field-effect transistor (EGFET) to detect pH values. Experimental parameters were adjusted by varying the oxygen flow rate in the process chamber to produce ZnGa2O4 sensing films with different oxygen ratios. These films were then treated in a furnace tube at an annealing temperature of 700 °C. The sensitivity and linearity of the constant current mode and the constant voltage mode were measured and analyzed in the pH range of 2-12. Under the deposition conditions with an oxygen ratio of 6%, the sensitivity reached 23.14 mV/pH and 33.49 μA/pH, with corresponding linearity values of 92.1 and 96.15%, respectively. Finally, the sensing performance of the ZnGa2O4 EGFET pH sensor with and without annealing processes was analyzed and compared.

New approach to produce cubic-WC at low temperature for hydrogen evolution reaction

A novel catalyst, a nanostructured cubic-WC (c-WC) flat film, is introduced for the hydrogen evolution reaction (HER) using a specialized magnetron sputtering system. This method results in over 94% crystalline c-WC0.95 formation at room temperature, featuring high-density stacking faults and twin defects. The catalytic performance of the c-WC film for HER is investigated through theoretical simulations and experimental studies. Density-functional theory (DFT) suggests that the c-WC (100) surface exhibits faster reaction kinetics than c-WC (111) surface, approaching the efficiency of Pt (111) surfaces. Experimentally, the c-WC0.95 film exhibits a high electrochemical surface area and increased active sites due to surface defects. Differential electrochemical mass spectrometry (DEMS) confirms an onset potential for HER of −50.0 mV for c-WC0.95 films and establishes electrodesorption as the rate-determining step. Overall, the c-WC film emerges as a cost-effective and efficient catalyst for green hydrogen production, showcasing excellent reproducibility and electrochemical stability.

A study of the tribological properties of Mo-S-Ti composite films prepared by magnetron sputtering

Pure MoS2 films exhibit disadvantages such as low densities, poor mechanical properties, and weak wear resistance under atmospheric environments. For this reason, Ti was chosen as the doping element in this work. Mo-S-Ti composite films with different Ti contents were deposited using the magnetron sputtering system, and the effects of Ti content on the chemical composition, mechanical and tribological properties of these films were analyzed by numerous characterization methods to determine the doping content of Ti elements. The results show that the tribological performance of Mo-S-Ti composite film under atmospheric environments reaches the best when the Ti content is 13.48 at%. In addition, the present work also found that longitudinal load and reciprocating frequency have a significant effect on the tribological properties of this film. It is easier to form high quality transfer film on GCr15 balls under higher longitudinal load and lower reciprocating frequency, thus transforming the friction between film and GCr15 ball into the friction between film and transfer film, resulting in excellent tribological performance.

Enhancement of photodetection performance of Ga2O3/Si heterojunction solar-blind photodetector using high resistance homogeneous interlayer

Creating homojunctions using Ga2O3 material presents a significant challenge, primarily because of the inherent difficulty in achieving stable p-type Ga2O3. The pn heterojunctions based on n-Ga2O3 materials offer a promising alternative for developing solar-blind photodetectors. In this work, our strategy is to fabricate a n-Ga2O3/p-Si heterojunction solar-blind photodetector with interface layers of high resistance and low resistance through using a magnetron sputtering system. The results indicate that a Ga2O3 layer with high resistance as an interface layer contributes to broadening the width of space charge region of this pn heterojunction, resulting in the enhancement of photodetection responsivity (61.7 mA/W @-5 V). Furthermore, the pn heterojunction photodetector exhibits a photo-response to 254 nm UV light at zero bias voltage, showcasing robust stability. This suggests significant potential for applications in the challenging environments. The synergistic blend of the enhanced photodetector performance and the well-established technology of Si integrated circuits is generating considerable enthusiasm.

Pulsed-dc bias magnetron sputtered TiB2 ceramic coating

Titanium diboride, TiB2, is well known as a ceramic material with a hexagonal structure which presents various attractive properties, such as high hardness and excellent corrosion, thermal oxidation, and wear resistance. However, one drawback of TiB2 coatings is their poor adhesion to substrate materials due to high compressive residual stress after deposition. The present study aimed to assess whether a PVD-TiB2 coating with both high hardness and sufficiently good adhesion to the substrate and good wear properties can be developed by a closed-field unbalanced magnetron sputtering system using pulsed-dc biasing. The TiB2 coating deposited on AISI M2 steel substrates was characterized in terms of the structural, mechanical and tribological property. From the experimental results, it can be concluded that a closed-field unbalanced magnetron sputtering system using pulsed-dc biasing can be used to produce a TiB2 coating with sufficiently good adhesion (82 N), and high hardness (2300 HK0.01), and low friction (0.34) under given deposition conditions. The deposition conditions, particularly substrate biasing and rotation, which inhibited the formation of (001) orientation, played a role in the coating's lack of superhardness.

On Numerical Modelling and an Experimental Approach to Heterojunction Tandem Solar Cells Based on Si and Cu2O/ZnO—Results and Perspectives

A comparative analysis of three advanced architectures for tandem solar cells (SCs) is discussed, respectively: metal oxide, thin film, and perovskite. Plasmonic solar cells could further increase solar cell efficiency. Using this development, an innovative PV technology (an SHTSC based on metal oxides) represented by a four-terminal Cu2O/c-Si tandem heterojunction solar cell is investigated. The experimental and numerical modelling study defines the main aim of this paper. The experimental approach to SHTSCs is analysed: (1) a Cu2O layer is deposited using a magnetron sputtering system; (2) the morphological and optical characterization of Cu2O thin films is studied. The electrical modelling of silicon heterojunction tandem solar cells (SHTSCs) is discussed based on five simulation tools for the optimized performance evaluation of solar devices. The main novelty of this paper is represented by the following results: (1) the analysis suggests that the incorporation of a buffer layer can improve the performance of a tandem heterojunction solar cell; (2) the effect of interface defects on the electrical characteristics of the AZO/Cu2O heterojunction is discussed; (3) the stability of SHTSCs based on metal oxides is studied to highlight the degradation rate in order to define a reliable solar device. Perspectives on SHTSCs based on metal oxides, as well as Si perovskite tandem solar cells with metal oxides as carrier-selective contacts, are commented on.