Plasma Sputtering Research Articles

A field programmable gate array based Langmuir probe system for measurement of plasma parameters at 500kHz in a high-power impulse magnetron sputtering plasma.

By utilizing Field Programmable Gate Arrays in a configuration similar to that of the Mirror Langmuir Probe, it is possible to bias a single probe at three precise voltages in sequence. These voltages can be dynamically adjusted in real-time based on the measured plasma electron temperature to ensure the transition region is always sampled. The first results have been obtained by employing this method and have generated real-time outputs of electron temperature, ion saturation current, and floating potential on a low temperature pulsed-DC magnetron at 500kHz. These results are in good agreement with the analysis of a conventionally swept Langmuir probe. This probe is designed with the intention of being implemented on MAST-U to aid in the study of exhaust physics and enable further investigation into filamentary behavior.

Realizing High Reversible Zinc Metal Anode by Modulating Surface Chemistry and Crystal Structure

AbstractThe uncontrollable dendrite growth on the Zn metal anode severely deteriorates the capacity and cycling stability of aqueous zinc–ion batteries (AZIBs), thereby retarding their practical application. In this work, through the combination of surface chemistry and crystal structure regulation, a duplex route of plasma sputtering and mechanical stretching is proposed to remove surface passivation layer and increase surface crystal defect (dislocations and textures) of Zn metal anode itself. Plasma sputtering can almost completely remove the surface passivation layer, ensuring a uniform Zn2+ flux at the interface, which is conducive to uniform nucleation. Mechanical stretching can increase the surface dislocation density and (002) texture, the former can reduce Zn2+ nucleation barrier, while the latter can guide Zn to grow parallel to the surface, inhibiting the growth of dendrites. Consequently, the as‐fabricated symmetrical cells exhibit stable and long lifespan (3560 h at 0.5 mA cm−2 for 0.5 mA h cm−2). The assembled full cells with α‐MnO2 cathode deliver a nearly 100% average coulombic efficiency even after 1000 cycles at 5 A g−1. Coupling a surface chemistry regulation with crystal structure control will be enlightening for solve the issues of metallic anodes in advanced metallic‐based batteries.

Improved corrosion resistance and cytotoxicity of nickel‐based alloy using novel plasma processing technique

AbstractIn this study, we address challenges in the biocompatibility of nickel‐based (NiCr) alloys, prevalent in the dental industry, due to toxic metal ion release impacting corrosion resistance and cytotoxicity. Employing magnetron sputtering and cathodic cage plasma nitriding (CCPN), a duplex plasma treatment (DPT) is introduced to the NiCr alloy. The novel approach enhances surface morphology, notably reducing ion leakage compared with untreated samples. Specifically, the CCPN‐TiN‐treated sample significantly improves corrosion resistance and minimizes metal ion leakage. This transformative DPT emerges as a promising solution for surface modification, particularly mitigating toxic ion leaching in aggressive electrolytes. This research demonstrates a major stride in enhancing NiCr alloy biocompatibility, emphasizing the vital role of innovative surface modification techniques for biomedical applications and challenges.

Measurement of Hydrogen Permeation Fluxes Through Tungsten Deposition Layer Growing by Hydrogen Plasma Sputtering and Observation of Microstructure

Hydrogen isotope behavior, especially permeation and retention, at the first wall is important for the safety and fuel sufficiency of fusion reactors. This study focuses on the deposition layer formed on the first wall by sputtered particles. Hydrogen permeation flux was measured under the co-deposition environment of hydrogen and tungsten, and the microstructure of the deposition layer was observed by a transmission electron microscope. Then the relationship between the observed hydrogen permeation behavior and the formation of the deposition layer was evaluated. The results showed that the deposited layers had three different microstructures and that the permeation flux decreased with its formation. However, it was concluded that the permeation behavior could be evaluated simply by the increase in the thickness of the deposited layer and that there was no clear effect of the different structures on the permeation behavior.

High temperature oxidation behaviors of Al/Cr composite coating on Ti2AlNb alloy

The Al/Cr coatings were deposited on Ti2AlNb alloy by magnetron sputtering and double glow plasma alloying technology to improve the oxidation resistance. The morphology of the protective coating was investigated by scanning electron microcopy and the phase composition of the coating was analyzed using x-ray diffraction. The results suggested that the protective coating with multilayer structure was dense and homogeneous. The formation of Cr inner diffusion layer was beneficial to the bonding strength between the coating and substrate, which was attributable to the double glow technology. The oxidation behaviors of Al/Cr coating were investigated by the isothermal oxidation tests for 100 h at 700 °C, 800 °C and 900 °C, respectively. The results indicated that the protective coating showed a lower oxidation rate. At 700 °C, the Al2O3 oxidation products were formed on the surface of coating at high temperature, which were dense and homogeneous against oxygen diffusion. With the increase of oxidation temperature, the external diffusion of Cr element reacted with oxygen to form Cr2O3, which provided the further protection. As for 900 °C, the volatile CrO3 was formed by the reaction of the external diffusion of Cr and Cr2O3, and the oxidation products Al2O3 and Cr2O3 continued to provide protection for Ti2AlNb alloy.

Effect of carbon black supports on the hydrogen evolution reaction activity of Pd nanoparticle electrocatalysts synthesized via solution plasma sputtering.

The hydrogen evolution reaction (HER) is a pivotal electrochemical process in water electrolysis, essential for hydrogen production. The efficiency and kinetics of HER are significantly influenced by the choice of catalyst and its support material. In this study, we investigated the effect of carbon supports on palladium (Pd) nanoparticle electrocatalysts synthesized via the solution plasma sputtering process for HER. Pd nanoparticles were loaded onto three hierarchically porous carbon black (CB) supports: Vulcan XC-72R, Ketjen Black EC-300J, and Black Pearls 2000. Well-crystalline Pd nanoparticles, ranging in size from approximately 2-6 nm, were distributed on the surface of CB supports with Pd loading contents ranging between 21 and 29 wt%. The catalysts exhibited lower specific surface areas compared to bare CB supports due to a significant decrease in exposed micropores, which were blocked by the Pd nanoparticles at their entrances. Among the CB supports investigated, Pd nanoparticles loaded on Black Pearls 2000 demonstrated the highest HER activity, as evidenced by the lowest overpotential, largest electrochemical surface area, and highest mass activity. This superior activity can be attributed to the unique characteristics of Black Pearls 2000, including its high surface area and abundant micropores. Furthermore, it demonstrated greater HER stability than commercial platinum (Pt)-based catalysts. Our finding suggests that Black Pearls 2000 could serve as a promising CB support for further developing highly efficient and stable HER electrocatalysts.

Analysis of a second peak of electron density observed in high-power impulse magnetron sputtering plasma using a Langmuir probe

Plasma characteristics of a high-power impulse magnetron sputtering (HIPIMS) for copper deposition were investigated using a time-resolved Langmuir probe to explore HIPIMS discharge physics. Various discharge frequencies and pulse widths were employed while operating the HIPIMS in a constant current mode. Waveforms of the HIPIMS cathode current remained constant throughout the HIPIMS voltage pulse. It was found that electrons exhibited a bi-Maxwellian energy distribution both during and after the HIPIMS pulse. After the HIPIMS pulse, plasma density built up to a second peak while the bulk electron temperature quickly decreased. By examining the effect of pulse width and discharge frequency on the temperature of hot electrons through Langmuir I–V curves, it is suggested that the hot electron ionization contributed to the occurrence of the second peak.

Surface Modification of NiTi Alloy with Sputtered Tantalum Coatings to Improve its Hardness, Corrosion Resistance and Biocompatibility

In this research, titanium alloys including smart nitinol (NiTi) were studied. The (NiTi) alloy tends to emitting (Ni) toxic ions due to its low resistance to corrosion within the body conditions over time. For (NiTi) coating process, the magnetron plasma sputtering (DC) technique was used with Aragon gas ratio of (90%) and Oxygen of (10%) in order to coat the alloy with Tantalum and its Oxide (Ta2O[Formula: see text] thin films. This is one of the methods used to improve the biocompatibility and better adhesion stability of the membrane on the (NiTi) surface, since Tantalum and its oxides are biocompatible and are not affected by the body fluids. Hardness, corrosion and biocompatibility were tested. The results showed improvement in the nominated properties using this coating technique. The hardness for the non-coated sample was (630 Kgf/mm[Formula: see text], meanwhile, the coated sample recorded (762 Kgf/mm[Formula: see text] using sputtering power of (25 W) with a thickness of (226 nm). Tantalum and its precipitated oxides on a pillar of thickness (90.4–226 nm) also exhibited a biocorrosion enhancement, when it was immersed in a Simulated Body Fluid (SBF). The corrosion rate for the non-coated sample was (1.204 × 10[Formula: see text], meanwhile for the coated sample, its value was (3.453 × 10[Formula: see text] at sputtering power of (15 W), considered as the lower corrosion rate. The scanning electron micrographs also showed an increase in the biocompatibility for the coated nitinol alloys (NiTi) in comparison with the non-coated, ones since it showed a clear formation of Hydroxyapatite (HA) on the sample surface after immersion in the SBF. This behavior was confirmed by the XRD measurements, which presented higher HA peaks on the coated samples surface in comparison with the non-coated samples.

Development of Antibacterial Cotton Textiles by Deposition of Fe2O3 Nanoparticles Using Low-Temperature Plasma Sputtering.

Antibacterial textiles can help prevent infections from antimicrobial-resistant pathogens without using antibiotics. This work aimed to enhance the cotton fabric's antimicrobial properties by depositing Fe2O3 nanoparticles on both sides of its surface. The nanoparticles were deposited using low-temperature plasma technology in a pure oxygen atmosphere, which is environmentally friendly. The Fe2O3 nanoparticles formed clusters on the fabric surface, rather than thin films that could reduce the airflow of the textile. The optimal conditions for the nanoparticle deposition were 200 W of plasma power, 120 min of immersion time, and 5 cm of Fe cathode-textile sample distance. The received antimicrobial textile was tested and the high efficiency of developed materials were successfully demonstrated against 16 microbial strains (Gram-positive and Gram-negative bacteria and fungi).

Fine-line formation of cobalt thin films via cyclic etching using two-step process

Co thin films were etched via cyclic etching using a two-step process of Cl2 plasma and Ar sputtering. In the first step, the Co surface was chlorinated by exposing the Co film to Cl2 plasma to form a CoCl2 layer, and the chlorinated Co film was removed via Ar sputtering in the second step. The saturation point of chlorination in the first step provided a 2 nm-thick CoCl2 layer. In the second step, the dc bias voltage and Ar sputtering time were varied to optimize the removal of the CoCl2 layer. A close relationship between the thickness of the CoCl2 layer and the sputtering conditions was revealed, which was responsible for the etch profiles of the Co films. Finally, 300 nm patterns of the Co films were successfully etched via cyclic etching without redeposition on the sidewall.

Reactive remote plasma sputtering of TiOx thin films and controlled growth of textured single-phase rutile using rf substrate biasing

Titanium oxide (TiOx) thin films were deposited by remote plasma sputtering (RPS) with the use of rf substrate bias onto unheated and water-cooled glass, Si, and Kapton substrates. The rf remote plasma power was kept constant (2.0 kW) and the properties of the films were studied as a function of deposition rate and substrate bias voltage. Four different reactive processes at four different deposition rates were developed under zero bias conditions by altering the target bias voltage and the flow of oxygen to give highly transparent TiOx films. These processes were studied with varying substrate bias voltage and the film structural, optical, and surface properties were investigated by GI-XRD, SEM, transmission, and sessile drop measurements. The changes in film structure and properties observed were related to the plasma conditions of the RPS system, investigated by dc electrical probe and OES measurements, and compared with other observations for films deposited under energetic conditions in the literature. All films deposited under zero bias conditions exhibited amorphous structures in GI-XRD and SEM images. Sufficient application of substrate bias was seen to promote columnar growth in cross-sectional SEM images and to crystallise phase pure rutile with no detection of the anatase phase in GI-XRD. Rutile bearing films were noted for their change in optical properties. Further increase of the substrate bias voltage caused a change in the texture of the rutile films from a low-energy [110] preferred orientation to a high-energy [101] and [002] preferred orientation. Contact angles of water with deposited films were found to increase with increasing substrate bias voltage and decreasing deposition rate. Film stress was also found to be influenced mainly by the substrate bias voltage process parameter.

A retarding field thermal probe for combined plasma diagnostics

The wide variety and ever-growing applications of plasma processes in research and industry require an equally growing diversity and accessibility of suitable plasma diagnostics. The plasma parameters and the tailoring thereof strongly influence the outcome of thin film deposition, plasma etching, or surface treatments, to name only a few. To further enhance the determination of different fluxes of species, their energies, and behaviour influencing a surface process, a custom-built combination of two commonly used diagnostics was developed. With a retarding field energy analyzer, one can obtain the ion energy distribution in a plasma by measuring the current at the collector depending on the applied voltage at the scan grid. A passive thermal probe determines the energy flux density coming from a process plasma by measuring the temperature change of a dummy substrate. In this study, we present a retarding field energy analyzer where a passive thermal probe substitutes the collector. By doing so, we can determine the energy distribution of the charged ions, their energy flux density at a certain potential, and the power deposited onto a substrate. Another advantage is that the thermal probe can even measure the power deposited by incoming (fast) neutrals and of the background gas when the grids keep away the ions. Hence, combining these two powerful diagnostics yields information neither can deliver on their own. The probe has been tested in three different plasma environments: ion beam source, magnetron sputtering and radio frequency discharge plasma.

Dual low pressure plasma process for SiCN:H thin films deposition: A comparative study

SiCN:H thin films have large possibilities of applications due to their versatile chemical and physical properties. Plasma Assisted Chemical Vapor Deposition (PACVD) process is widely used for SiCN:H deposition. Here we discuss on the potentialities of dual Electron Cyclotron Resonance (ECR) and Radio Frequency Magnetron Sputtering (rf MS) plasmas coupling for SiCN:H deposition in Ar/N2/Si(CH3)4 gas mixture. The study is carried out by varying the autopolarisation voltage Vbias of the silicon target. ECR plasma gives low deposition growth rate about 50 nm/h. The films are transparent. SiCN nanopillars with high aspect ratio are obtained. Rf MS plasma gives high deposition growth rate up to 2200 nm/h. The films are opaque in the near UV and transparent in the visible depending on their thickness. The optical index at 630 nm is 1.95, the Tauc's band gap is 3.0 eV and do not change with Vbias. Dual ECR/rf MS plasma gives high deposition growth rate up to 2300 nm/h. The films are transparent. The optical index varies between 1.7 and 2.05 at 630 nm and the Tauc's band gap decreases linearly between 4.75 and 3.4 eV with Vbias. Dual ECR/rf MS plasma coupling is a very promising PACVD process for thin films deposition.

Prediction by a hybrid machine learning model for high-mobility amorphous In2O3: Sn films fabricated by RF plasma sputtering deposition using a nitrogen-mediated amorphization method

In this study, we developed a hybrid machine learning technique by combining appropriate classification and regression models to address challenges in producing high-mobility amorphous In2O3:Sn (a-ITO) films, which were fabricated by radio-frequency magnetron sputtering with a nitrogen-mediated amorphization method. To overcome this challenge, this hybrid model that was consisted of a support vector machine as a classification model and a gradient boosting regression tree as a regression model predicted the boundary conditions of crystallinity and experimental conditions with high mobility for a-ITO films. Based on this model, we were able to identify the boundary conditions between amorphous and crystalline crystallinity and thin film deposition conditions that resulted in a-ITO films with 27% higher mobility near the boundary than previous research results. Thus, this prediction model identified key parameters and optimal sputtering conditions necessary for producing high-mobility a-ITO films. The identification of such boundary conditions through machine learning is crucial in the exploration of thin film properties and enables the development of high-throughput experimental designs.

Azimuthal ion movement in HiPIMS plasmas—part I: velocity distribution function

Magnetron sputtering discharges feature complex magnetic field configurations to confine the electrons close to the cathode surface. This magnetic field configuration gives rise to a strong electron drift in azimuthal direction, with typical drift velocities on the order of 100 km s−1. In high power impulse magnetron sputtering plasmas, the ions have also been observed to follow the movement of electrons with velocities of a few km s−1, despite being not magnetized. In this work, we report on measurements of the azimuthal ion velocity using spatially resolved optical emission spectroscopy, allowing for a more direct measurement compared to experiments performed using mass spectrometry. The azimuthal ion velocities increase with target distance, peaking at about 1.55 km s−1 for argon ions and 1.25 km s−1 for titanium ions. Titanium neutrals are also found to follow the azimuthal ion movement which is explained with resonant charge exchange collisions. The experiments are then compared to a simple test-particle simulation of the titanium ion movement, yielding good agreement to the experiments when only considering the momentum transfer from electrons to ions via Coulomb collisions as the only source of acceleration in azimuthal direction. Based on these results, we propose this momentum transfer as the primary source for ion acceleration in azimuthal direction.

Assessment of thermomechanical stability of DLC films deposited by Ne-HiPIMS technology for high-temperature applications

Enhancement of the thermomechanical stability of diamond-like carbon (DLC) coatings is highly demanded by the automotive industry due to graphitization at higher temperatures. This work is devoted to the assessment of the thermomechanical stability of annealed DLC films deposited by increasing Ne up to 50% in high-power impulse magnetron sputtering (HiPIMS) plasma, followed by the evaluation of their tribomechanical properties. The tribological performance of the films was assessed by room-temperature tribological tests after annealing the films, and by high-temperature tribological test at 300 °C in ambient atmosphere. The microstructure and chemical compositions of the films were analyzed, and the hybridization state of the annealed films was determined by x-ray absorption near-edge spectroscopy (XANES). The wear mechanism involved in both high-temperature and annealed films tribological tests with the steel counterpart was the combination of abrasion and adhesion. It was observed that all the films demonstrated stable tribomechanical performance by annealing up to 500 °C, while from 600 °C, the film deposited in pure Ar plasma demonstrated poor tribomechanical performance. In contrast, increasing Ne to 50% in plasma led to an increase in the thermomechanical stability of DLC films to more than 700 °C, and resisting graphitization up to 800 °C.

Effects of power on tribological and mechanical properties of diamond-like carbon-film-modified rubber

This study aims to improve the wear resistance of nitrile butadiene rubber (NBR) by depositing diamond-like carbon (DLC) films using direct-current magnetron sputtering (DC-MS), a simple and cost-effective technique. DC-MS is a coating process that uses a direct current to generate an electric field and sputter conductive materials from a target to a substrate. A magnetic field enhances the plasma density and sputtering rate. This study examines the bonding force, surface morphology, tribological properties and mechanical strength of DLC. Scanning electron microscopy, Raman spectroscopy and X-ray photoelectron spectroscopy are used to characterize the cross-sectional morphology, structural features and chemical bonding species of DLC films and NBR substrates. The nanoindentation results show that varying the power has no significant effect on hardness and Young’s modulus. Tribological tests are conducted under ambient conditions using a ball-and-disk tribometer, with a fixed load of 0.3 N. The results indicate that the power of DLC films influences their tribological properties. Specifically, DLC films prepared at 120 W exhibit superior tribological properties, maintaining a stable coefficient of friction below 0.2 for the test duration. These findings have promising implications for application of DLC films.

Single-step fabrication of fibrous Si/Sn composite nanowire anodes by high-pressure He plasma sputtering for high-capacity Li-ion batteries

To realize high-capacity Si anodes for next-generation Li-ion batteries, Si/Sn nanowires were fabricated in a single-step procedure using He plasma sputtering at a high pressure of 100–500 mTorr without substrate heating. The Si/Sn nanowires consisted of an amorphous Si core and a crystalline Sn shell. Si/Sn composite nanowire films formed a spider-web-like network structure, a rod-like structure, or an aggregated structure of nanowires and nanoparticles depending on the conditions used in the plasma process. Anodes prepared with Si/Sn nanowire films with the spider-web-like network structure and the aggregated structure of nanowires and nanoparticles showed a high Li-storage capacity of 1219 and 977 mAh/g, respectively, for the initial 54 cycles at a C-rate of 0.01, and a capacity of 644 and 580 mAh/g, respectively, after 135 cycles at a C-rate of 0.1. The developed plasma sputtering process enabled us to form a binder-free high-capacity Si/Sn-nanowire anode via a simple single-step procedure.

Plasma sputtering of biased electrodes in an oblique magnetic field

The surface erosion of biased electrodes immersed in a radio frequency (RF) plasma was investigated in oblique magnetic fields ranging from 0.1 T to 3.5 T. The plasma potential and density in the vicinity of the biased electrode have been measured using an RF-compensated cylindrical Langmuir probe moved by a three-dimensional motorised arm in the ALINE facility at 0.1 T. The erosion profiles were determined for different gases (argon and helium), magnetic field strength and plasma volume for the same electrode surface area at an angle of 5∘ with the magnetic field in three different experimental geometries. The radial electric field (perpendicular to the magnetic field) in the plasma column has been deduced from plasma potential measurements. This radial field makes the ions converge to the core of the plasma column at grazing angles (30∘) and is reversed at larger angles. The ion flux on the sample increases with the magnetic field magnitude leading to a strong erosion inhomogeneity. At lower plasma volume, the erosion rate is sensitively enhanced. Local redeposition was identified using x-ray photoelectron spectroscopy on the surfaces exhibiting preferential deposition directions. Finally, the asymmetric erosion patterns obtained from a molybdenum layer etching are explained by the similar asymmetric density maps obtained with the probe and by the drift and the local sheath acceleration.

Tribology of Coated 316L SS by Various Nanoparticles.

Nanocoating of biomedical materials may be considered the most essential developing field recently, primarily directed at improving their tribological behaviors that enhance their performance and durability. In orthodontics, as in many medical fields, friction reduction (by nanocoatings) among different orthodontic components is considered a substantial milestone in the development of biomedical technology that reduces orthodontic treatment time. The objective of the current research was to explore the tribological behavior, namely, friction of nanocoated thin layer by tantalum (Ta), niobium (Nb), and vanadium (V) manufactured using plasma sputtering at 1, 2, and 3 hours on substrates made of 316L stainless steel (SS), which is thought to be one of the most popular alloys for stainless steel orthodontic archwires. The friction of coated 316L SS archwires coated with Ta, Nb, and V plasma sputtering is hardly mentioned in the literature as of yet. An oscillating pin-on-plate tribological test using a computerized tribometer was performed by applying a load of 1 N for 20 minutes under the dry condition at room temperature (25°C) to understand their role in the tribological behavior of the bulk material. Ta and Nb were found to reduce the friction of their SS substrate significantly (45 and 55%, respectively), while V was found to deteriorate the friction of its substrate. Moreover, sputtering time had no substantial role in the friction reduction of coatings. Nanocoating of 316L SS bulk material by Nb and Ta with a 1-hour plasma sputtering time can enhance dramatically its tribological behavior. Higher coating hardness, smaller nanoparticle size, intermediate surface coating roughness, and lower surface binding energy of the coatings may play a vital role in friction reduction of the coated 316L SS corresponding to SS orthodontic archwires, predicting to enhance orthodontic treatment.