Direct Current Magnetron Sputtering System Research Articles

Control of Cu Film Stress Deposited by Magnetron Sputtering Using Graphene Flake Layers

Residual stress of a 10 μm thick copper (Cu) film deposited using direct current (DC) magnetron sputtering system was analyzed. Graphene flake, having high toughness and strength properties, was inserted in Cu film for decreasing residual stress. Compared with the Graphene sheet transfer method, a Cu film sample with Graphene flake inserted using a simple brush deposition method could be fabricated. By using a graphene flake layer, the Cu residual stress was decreased from 25.4 MPa to 14.6 MPa. As decreasing the Graphene flake area ratios from 100% to 40%, the residual stress was reduced to 2.8 MPa. A 50×50 mm size heat sink was fabricated to confirm the thermal diffusion of Graphene flake, and the LED device was mounted on it. As a result, graphene flake was obtained the result that improved thermal diffusion of the heat sink.

Research on microstructure and shear strength of Al alloy jointed by sputtered Cu thin film deposited through HiPIMS and DCMS techniques

Transient liquid phase bonding (TLP bonding) in jointing technology is a promising method for achieving precision joining of aluminum alloys and creating low-cost products for use in the electric vehicles (EVs) industry, which can contribute to a low-carbon economy. This research is primarily focused on the jointing technology of aluminum alloys and is divided into two parts. The first part involves vacuum soldering between A6063 aluminum alloy with copper layers of 1, 3 and 5 μm thickness, and tin solder under thermal treatment. The second part is Cu-Al eutectic bonding. In this study, we used Ar ions to bombard the surface of A6063 aluminum alloy to remove the oxide layer and deposited a copper layer using direct-current magnetron sputtering (DCMS) and high-power impulse magnetron sputtering (HiPIMS). We then analyzed the joint interface of the samples using Scanning Electron Microscope (SEM), Energy-Dispersive X-ray Spectroscopy (EDS), and Scanning Acoustic Tomography (SAT) to calculate the joint ratio of the entire joint surface. Finally, we measured the shear strength to evaluate the bonding effect. The results indicate that the eutectic bonding method exhibits better bonding performance for aluminum alloys compared to the soldering method. Furthermore, the shear strength increased with increasing thickness of the sputtered copper layer. When comparing two sputtering technologies, the copper films sputtered by HiPIMS system exhibit better quality those produced by the DCMS system. As a result, aluminum alloy bonding completed with HiPIMS has higher bonding strength, demonstrating that HiPIMS is a powerful coating tool.

Particle-in-Cell Simulations for the Improvement of the Target Erosion Uniformity by the Permanent Magnet Configuration of DC Magnetron Sputtering Systems

Improving the target erosion uniformity in a commercial direct current (DC) magnetron sputtering system is a crucial issue in terms of process management as well as enhancing the properties of the deposited film. Especially, nonuniform target erosion was reported when the magnetic flux density gradient existed. A two-dimensional (2D) and a three-dimensional (3D) parallelized particle-in-cell (PIC) simulation were performed to investigate relationships between magnetic fields and the target erosion profile. The 2D PIC simulation presents the correlation between the heating mechanism and the spatial density profiles under various magnet conditions. In addition, the 3D PIC simulation shows the different plasma characteristics depending on the azimuthal asymmetry of the magnets and the mechanism of the mutual competition of the E × B drift and the grad-B drift for the change in the electron density uniformity.

Effect of Microstructure of TiN /TiCN Layer on the Structural, Mechanical and Tribological Properties of the Ti/TiN/TiCN Films

A direct current magnetron sputtering (DCMS) system at room temperature was applied to deposit the Ti/TiN/TiCN films. In order to research the effect of the microstructure of the TiN/TiCN layer on the Ti/TiN/TiCN films, the deposition time ratio of the TiN/TiCN layer ranged from 28.57 to 200%, and the whole deposition time of the films and the deposition time of Ti layer were constant. In this work, the relationship between structure and mechanical properties of films were investigated. The research results showed that the composition and structure of the films only slightly changed, while the crystalline orientation of the TiCN layer was of significant variation with the deposition time of the TiN layer. It is shown that the adhesion strength and internal stresses were 18.6 ± 1.5 N and 140 MPa when the deposition time ratio was 50%. By adjusting the deposition time ratio, the films displayed significant improvement in tribological behaviors. The coefficients of friction (COF) for the films deposited under deposition time ratio of 50% were about only 0.139 when the value of COF was stabilized. This work can provide a good wear-resisting film prepared approach at room temperature.

Sketching novel nanostructured diamond-consisted thin films on AISI 321 stainless steel: Microstructure, mechanical and tribological properties

In a reactive direct current (DC) magnetron sputtering (MS) system, converting the cathode (target) magnetic field configuration from a balanced magnetron (BM) to an unbalanced magnetron (UBM) is an impressive strategy to enforce the energetic ion bombardment, providing sufficient activation energy for deposition of high-quality nanostructured films. In the present work, the nanostructured (grain size ˂ 100 nm) BM and UBM sputtered Niobium-doped amorphous Carbon (Nb: a-Carbon) films' microstructural, mechanical, and tribological characteristics changes were thoroughly investigated and compared. From the XRD and Raman analysis outcomes both graphite-like Carbon (GLC) and Niobium carbide (NbC) phases were detected in the BM sputtered film. However, novel cubic and hexagonal crystalline Diamond (CD) phases were successfully constructed from the UBM sputtered films besides the GLC and NbC phases. Records displayed that the change over the cathode magnetic field configuration from BM to UBM is a responsible factor for the reduction of the surface roughness (from 32 nm to 25 nm) and increment of the crystallite size (from 14 nm to 15.5 nm), hardness (from 18 GPa to 27 GPa), and elastic modulus (from 210 GPa to 425 GPa) values. On the contrary, via changing BM to UBM sputtering the films' tribological properties were negatively affected, leading to the increase of the coefficient of friction (COF) from 0.09 to 0.11 and the wear rate (WR) from 5.25 × 10−5 mm3/N.m to 9 × 10−5 mm3/N.m. The achieved results confirmed that the UBM configuration could be selected as a critical facility over the MS system that gives enough energy to arrange Carbon species in the crystalline Diamond phase at a relatively low temperature. One step further, the Ar/CH4 ratio variation was assessed as an influential factor that leaves considerable changes over the UBM sputtered film characteristics. The results indicated that by doubling the Ar/CH4 ratio, the nanocrystalline Diamond phases are still observable. However, this change led to the increase in surface roughness (from 25 nm to 28 nm) and crystallite sizes (NbC, from 15.5 nm to 18.6 nm, cubic Diamond, from 25.8 nm to 36 nm, and hexagonal Diamond from 18.9 nm to 21.6 nm). While the variations adversely affected the UBM sputtered films' hardness (from 27 GPa to 21 GPa) and modulus of elasticity (from 425 GPa to 330 GPa). Simultaneously, the COF and WR endured a slight increment, from 0.11 to 0.14 and 9 × 10−5 mm3/N.m to 9.8 × 10−5 mm3/N.m, respectively.

Performance evaluation and durability studies of W/WAlSiN/SiON/SiO2 based spectrally selective solar absorber coating for high-temperature applications: A comprehensive study on thermal and solar accelerated ageing

We report a solar selective coating of W/WAlSiN/SiON/SiO2 fabricated using a Four-Cathode Reactive Unbalanced Direct Current (DC) magnetron sputtering system with high thermal stability, good durability and resistance to outdoor testing conditions. The coating also exhibits superior mechanical properties (Hardness ∼12 GPa). In addition, thermal shock tests at high temperatures and solar accelerated ageing measurements are investigated in-depth to analyze the performance of the solar absorber coating. The thermal shock tests of the samples at various temperatures in the range of 500–600 °C depict the excellent thermophysical resistance of the as-deposited samples. To test the thermal durability of the solar absorber coating, we applied 200 cycles of solar accelerated ageing on the samples using a solar accelerated ageing facility with concentrated flux density varying from 50 to 250 kW/m2. These cycles have been defined to replicate real high solar flux and temperature on the front side of the samples along with high cooling and heating rates, reproducing the abrupt variations of solar irradiation due to cloudy weather and subsequent thermal shocks for a given receiver. Overall, the durability tests of the solar absorber carried out under various conditions indicate a minimal change in the optical properties (Δα = 0.002 and Δε = 0), thus, making it a potential candidate for high-temperature solar thermal applications.

Improved pH-Sensing Characteristics by Pt Nanoparticle-Decorated ZnO Nanostructures

In this article, the znic oxide (ZnO) nanorods (NRs) and Pt-nanoparticles (NPs) decorated on ZnO (Pt@ZnO) NRs based on extended-gate field-effect-transistor (EG-FET) sensor were prepared and expolred through a simple hydrothermal method (HTM) and a direct current (DC) magnetron sputtering system (0 and 30 s). The results showed that all crystals preferentially grew in the c-axis direction. The ZnO and Pt@ZnO pH sensors are also called ps-0 and ps-30. The Pt sheet as reference electrode was used to test the sensitivity and linearity of buffer solutions with various pH values. It was found that both of them revealed good linearity and sensitivity, and ps-30 sample showed notably enhanced sensing characteristic. As a result, the average current and voltage sensitivities of the ps-0 samples were 15.50 μA pH−1 and 28.95 mV pH−1, and linearity curves were 0.990 and 0.978, whereas that of the ps-30 samples were 47.82 μA pH−1 and 49.83 mV pH−1 with a linearity of 0.985 and 0.994, respectively. Furthermore, the ps-30 samples have superior output response voltage, which demonstrated that the devices will be extremely useful in pH-sensing applications.

Study on the mechanism for the deposition of a porous zinc thin film by using a modified DC magnetron sputtering system

The mechanism for the deposition of zinc to form porous thin films is not clearly understood. In this study, a modified direct current (DC) sputtering system was used to deposit polycrystalline porous zinc thin films on an amorphous glass substrate to elucidate the mechanism. Subsequently, the properties of the thin films, such as its film thickness, the average particle size, and its porosity, were investigated under different experimental parameters, including pressure, DC discharge power, and the gas ratio between Ar and He. The plasma properties were also studied using a Langmuir probe. An increase in deposition pressure and DC discharge power was found to increase the deposition thickness and the particle size in the thin films whereas an increase in the He content increased the thickness and decreased the particle size. The investigation of the growth mechanism revealed that the zinc particles were oriented in different planes at early and later stages of deposition. Moreover, the properties of the thin films were observed to be affected by the energy loss of the zinc atoms and the bonding force between the substrate and the zinc particles. This understanding of the mechanism of thin-film formation will help to guide the optimization of experimental parameters in the fabrication of high-quality thin films.

An insight on the MoS2 tribo-film formation to determine the friction performance of Mo-S-N sputtered coatings

Amorphous Mo-S-N coatings are known to provide excellent tribological properties in diverse environments due to easy sliding under the influence of MoS 2 tribo-films. However, the role of nitrogen incorporation, the formation mechanism of MoS 2 tribo-film at the sliding interface and the changes in the friction behaviour under different environments are not fully understood. In this study, an amorphous coating with 30 at. % N was deposited in a semi-industrial reactive direct current magnetron sputtering (DCMS) system, using a single MoS 2 target in combination with a secondary plasma source. The coating was predicted to have either a Mo-S-N phase with N filling some of the S sites or a MoS 2 (N 2 ) structure where the gas molecules prevent the formation of a crystalline lamellar structure. Tribological studies performed in vacuum and ambient air resulted in steady-state COF values of 0.03 and 0.15, respectively. High-resolution transmission electron microscopy (HRTEM) analysis performed on the wear-tracks revealed that the low coefficient of friction (COF) in vacuum was attributed to the formation of a thick and continuous lamellar tribo-film with a low amount of nitrogen. Contrarily, in ambient air, the surface oxidation disturbed the formation of a continuous MoS 2 tribo-film from the amorphous coatings, leading to an increase in the COF and wear rate. This study shows through indirect measurements of the chemical composition of the as-deposited coating and wear debris that nitrogen is stored in gaseous form (N 2 ) within the amorphous matrix and is released from the contact during sliding. • Amorphous Mo-S-N coatings with 30 at. % N deposited with high adhesion to steel. • Tribo-film formation and role of N on the lubricating behaviour of Mo-S-N coatings. • COF in vacuum (10 −2 Pa) of 0.03 and in ambient air (24 °C, 20–30% RH) of 0.15. • Low friction in vacuum due to formation of a MoS 2 tribo-layer at the sliding interface. • Higher friction in ambient air due to a surface oxide formed at the interface.

Curved-boundary particle-in-cell simulation for the investigation of the target erosion effect of DC magnetron sputtering system

A two-dimensional particle-in-cell simulation with a curved-boundary field solver makes it possible to investigate the target erosion effects in a direct current magnetron sputtering system. The correlation between the ion flux deformation and the sputtering yield profile for the eroded target has been investigated, considering the ion energy and angle distributions. It was found that the sputtering yield profile does not change abruptly, although the ion flux profile changes sensitively with the increase in the erosion depth. The criteria for the judgment of the critical erosion depth are provided based on the sputtering yield profile.

Glucose Oxidase/Nano-ZnO/Thin Film Deposit FTO as an Innovative Clinical Transducer: A Sensitive Glucose Biosensor.

In the present research, a new biocompatible electrode is proposed as a rapid and direct glucose biosensing technique that improves on the deficiencies of fast clinical devices in laboratory investigations. Nano-ZnO (nanostructured zinc oxide) was sputtered by reactive direct current magnetron sputtering system on a precovered fluorinated tin oxide (FTO) conductive layer. Spin-coated polyvinyl alcohol (PVA) at optimized instrumental deposition conditions was applied to prepare the effective medium for glucose oxidase enzyme (GOx) covalent immobilization through cyanuric chloride (GOx/nano-ZnO/PVA/FTO). The electrochemical behavior of glucose on the fabricated GOx/nano-ZnO/PVA/FTO biosensor was investigated by I-V techniques. In addition, field emission scanning electron microscopy and electrochemical impedance spectroscopy were applied to assess the morphology of the modified electrode surface. The I-V results indicated good sensitivity for glucose detection (0.041 mA per mM) within 0.2–20 mM and the limit of detection was 2.0 μM. We believe that such biodevices have good potential for tracing a number of biocompounds in biological fluids along with excellent accuracy, selectivity, and precise analysis. The fast response time of the fabricated GOx/nano-ZnO/PVA/FTO biosensor (less than 3 s) could allow most types of real-time analysis.

Direct current magnetron coating chamber characterization directed toward the efficient development of broadband x-ray optic multilayer coatings

A direct current (DC) magnetron sputtering system has been developed at NASA Marshall Space Flight Center for depositing broadband x-ray optic multilayer coatings. The system has the capability to house up to four, 2-in.-diameter direct-cooled DC magnetron cathodes. The 2-in.-diameter cathodes facilitate low-cost, early stage research and development of various types of optical coatings. Despite the small target diameter, good coating uniformity on 4-in.-diameter substrates is demonstrated. Sources of both systematic and random error in the deposition of depth-graded multilayer coatings were identified and compensated for, resulting in the ability to deposit coating that required ∼7.5 h of total deposition time. Final verification of the system was concluded with the deposition of an NuSTAR W/Si depth-graded multilayer coating design (flight recipe 10).

High entropy alloy FeMnNiCoCr coatings: Enhanced hardness and damage-tolerance through a dual-phase structure and nanotwins

Three FeMnNiCoCr high entropy alloy (HEA) coatings were deposited onto M2 steel substrates using a direct current (DC) magnetron sputtering system under a range of substrate bias voltages (−20 V, −60 V and −120 V). The microstructure transformed from a fine elongated structure to coarse V-shaped columnar grains with increasing substrate bias voltage. A high density of nanotwins, together with the presence of a partial fcc-to-hcp transformation, was observed in the coating deposited at −120 V. This was attributed to the introduction of stacking faults whose presence was promoted by preferential re-sputtering effects during the deposition process. A high hardness value of ~9.1 GPa, accompanied by exceptional damage-tolerance, was achieved in the coating deposited at −120 V. Here, the formation of nanotwins and the dual-phase structure was found to contribute to this remarkable combination of hardness and resistance to plastic deformation.

Micromorphology analysis of TiO2 thin films by atomic force microscopy images: The influence of postannealing.

This work describes an analysis of titanium dioxide (TiO2 ) thin films prepared on silicon substrates by direct current (DC) planar magnetron sputtering system in O2 /Ar atmosphere in correlation with three-dimensional (3D) surface characterization using atomic force microscopy (AFM). The samples were grown at temperatures 200, 300, and 400°C on silicon substrate using the same deposition time (30 min) and were distributed into four groups: Group I (as-deposited samples), Group II (samples annealed at 200°C), Group III (samples annealed at 300°C), and Group IV (samples annealed at 400°C). AFM images with a size of 0.95 μm × 0.95 μm were recorded with a scanning resolution of 256 × 256 pixels. Stereometric analysis was carried out on the basis of AFM data, and the surface topography was described according to ISO 25178-2:2012 and American Society of Mechanical Engineers (ASME) B46.1-2009 standards. The maximum and minimum root mean square roughnesses were observed in surfaces of Group II (Sq = 7.96 ± 0.1 nm) and Group IV (Sq = 3.87 ± 0.1 nm), respectively.

Influence of N2 Gas Flow Ratio and Working Pressure on Amorphous Mo–Si–N Coating during Magnetron Sputtering

In this study, Mo–Si–N coatings were deposited on Si wafers and tungsten carbide substrates using a reactive direct current magnetron sputtering system with a MoSi powder target. The influence of sputtering parameters, such as the N2 gas flow ratio and working pressure, on the microstructure and mechanical properties (hardness (H), elastic modulus (E), and H/E ratio) of the Mo–Si–N coatings was systematically investigated using X-ray diffractometry (XRD), scanning electron microscopy (SEM), nanoindentation, and transmission electron microscopy (TEM). The gas flow rate was a significant parameter for determining the crystallinity and microstructure of the coatings. A Mo2N crystalline coating could be obtained by a high N2 gas flow ratio of more than 35% in the gas mixture, whereas an amorphous coating could be formed by a low N2 gas flow ratio of less than 25%. Furthermore, the working pressure played an important role in controlling the smooth surface and densified structure of the Mo–Si–N coating. For the amorphous Mo–Si–N coating deposited with the lowest working pressure (1 mTorr), the hardness, elastic modulus, and H/E ratio reached from 9.9 GPa, 158.8 GPa, and 0.062 up to 17.9 GPa, 216.1 GPa, and 0.083, respectively.

Structural and Mechanical Properties of AlCoCrNi High Entropy Nitride Films: Influence of Process Pressure

In the present study, novel AlCoCrNi high entropy nitride (HEN) films were deposited on Si substrate by a reactive direct current magnetron sputtering system. In order to investigate the influence of sputtering parameters on the microstructure and mechanical properties of the film, nitrogen flow ratio (RN: 25–100%) and process pressure (1.33 × 10−1–1.33 Pa) were controlled, respectively. All the films were identified as an amorphous phase with composition of near equiatomic ratios, regardless of the conditions of nitrogen flow ratios and process pressures. However, the limited mechanical properties were found for the films deposited under different nitrogen flow ratios with retaining the process pressure of 1.33 Pa. To enhance the mechanical properties of the AlCoCrNi HEN film, process pressure was adjusted. From the transmission electron microscopy (TEM) observation, the structure of the film deposited at the process pressure of 1.33 Pa is identified as a porous and open structure with a number of density-deficient boundary and nano-scale voids. On the other hand, densified morphology of the film was observed at pressure of 1.33 × 10−1 Pa. As a result, the hardness, elastic modulus, and H/E were improved up to 16.8, 243 GPa, and 0.0692, respectively.

Mechanical and tribological properties of Hf1-xMoxNy thin films as a function of Mo contents

Ternary transition metal nitrides have procured wide attention towards practical application due to their high hardness, wear resistance and thermal stability. In this study, Hf1-xMoxNy thin films are deposited by reactive direct current magnetron sputtering (R-DCMS) system in an effort to improve further the properties of their analogous binary compounds. In addition, the influence of Mo content on the structure, mechanical and tribological properties of the films are also investigated. The composition and microstructure of the as-deposited Hf1-xMoxNy films are characterized by X-ray diffraction, Raman and scanning electron microscopic techniques. Spectroscopic results show that, as-sputtered Hf1-xMoxNy films mainly consist of single solid solution phase with rock-salt structure. Ultra-micro hardness and ball-on-disc wear tests are conducted to evaluate the mechanical and tribological properties of Hf1-xMoxNy films. The toughness Hf1-xMoxNy films are enhanced, and the film with x = 0.589 shows better mechanical properties, meanwhile, the lowest wear rate of 0.57 × 10−6 mm3/Nm, which is two order magnitudes lower than corresponding binary compounds viz., δ-HfN and γ-Mo2N, and lowest friction coefficient of 0.35 are also obtained. This could be attributed to the effect of solution reinforcement and valence electron concentration. The unique wear resistance of Hf1-xMoxNy is ascribed to the outstanding oxidation resistances and higher H/E and H3/E2 values, which indicate the mechanical properties, wear resistance and anti-friction of δ-HfN and γ-Mo2N can be improved by alloying with each other.

Influence of Deposition Techniques on the Thermal Boundary Resistance of Aluminum Thin-Films

The influence of film deposition techniques on the thermal boundary resistance of an aluminum (Al)/silicon (Si) interface was investigated in this study. Al films 100 nm in thickness were deposited on Si(100) wafers using an e-beam evaporator and a direct current (DC) magnetron sputtering system. Their microstructural characteristics were inspected using scanning electron microscopy with energy dispersive spectroscopy, atomic force microscopy, and X-ray diffraction. The thermal boundary resistance values of the samples were measured using the time-domain thermoreflectance technique and numerically analyzed based on the transient Fourier heat conduction equation. A non-equilibrium molecular dynamics (MD) study was carried out to understand the effect of the atomic disorder at the film/substrate interface. Results show that the film produced by DC sputtering has a rougher surface than that of the e-beam evaporated one and a higher thermal boundary resistance. This is in agreement with the qualitative trend observed from the MD simulation that showed increases in thermal boundary resistance with the depth of atom intermixing.

Surface functionalization of Ag/polypyrrole-coated cotton fabric by in situ polymerization and magnetron sputtering

Flexible electronic devices have attracted considerable attention in recent years, and textile fabrics are usually used as the substrates because of their good moisture absorption performance and high flexibility. However, ordinary textile fabrics are electrically insulating, which limits their strain sensing sensitivity. In this study, cotton fabric endowed with high electrical conductivity was prepared by a two-step process of in situ polymerization and direct current (DC) magnetron sputtering. It was firstly modified with a continuous polypyrrole (PPy) thin film by using the in situ polymerization method and then coated with silver (Ag) thin film by using a DC magnetron sputtering system. The experimental results revealed that the resultant Ag/PPy-coated cotton deposited with a sputtering power of 200 W for 25 min has the highest electrical conductivity and its average sheet resistance is 11.7 Ω/sq. Moreover, the Ag/PPy-coated cotton exhibited the advantages of high hydrophobicity, thermal stability, electromechanical performance and washing fastness. Overall, the effective flexibility and high electrical conductivity of the Ag/PPy-coated cotton have been validated effectively and make it one of the promising candidates for preparing electromagnetic shielding and antistatic and smart wearable textile products, especially flexible electronic devices.

On the nano-glass formation of the Ni–Ti thin films and related micro-structure and mechanical properties by controlling sputtering conditions

In this research, glassy Ni–Ti thin films were sputtered on a flexible substrate (Kapton) using direct current (DC) magnetron sputtering system at ambient temperature. The influence of the sputtering pressure on the microstructure, chemical composition, thickness, mechanical properties and the ability to form nano-glass structure was investigated. Micro-structural characterizations of the thin films by x-ray diffraction, scanning and transmission electron microscopy (SEM and TEM) indicate that the sputtered thin films at a minimum pressure of 0.3 Pa have an amorphous structure consisting of nano-glassy grains. Furthermore, as the pressure increasing from 0.1 up to 0.8 Pa, the difference between the chemical composition of the thin films and the target increases. This difference is due to increasing of interatomic collisions between Ar and sputtered atoms that reduces the kinetic energy of sputtered atoms and rises to the scatter of atoms. In addition, the formation of micro-cracks in the films is also encouraged by increasing the sputtering pressure. For evaluation of the mechanical properties of the crystallized Ni–Ti/Kapton composite thin films, the tensile test was used and the results show that the partially crystallized Ni–Ti thin film sputtered at 0.3 Pa has the optimum ultimate tensile strength and toughness due to its composite (amorphous/nano-crystalline) structure.