Plasma Deposition System Research Articles

Microstructural and micromechanical characteristics of composite osteoconductive coatings deposited by the atmospheric pressure plasma technique.

Long-term placement of facial implants requires avoiding the formation of fibrous tissue capsules around the artificial material by creating osteoconductive properties of the surface. Most promising approach is the deposition coatings made of materials very similar to bone mineral components, that is, calcium phosphates such as hydroxyapatite (HAp). As part of the research work, an innovative, cost-effective atmospheric pressure plasma deposition (APPD) system was used as a low-temperature coating technology for generating the HAp coatings deposition. Full microstructural characterisation of the coatings using SEM and TEM techniques was carried out in the work. It has been shown that the fully crystalline HAp powder undergoes a transformation during the coatings deposition and the material had a quasi-sintered structure after deposition. The crystalline phase content increased at the coating/substrate interface, while the surface of the HAp was amorphous. This is a very beneficial phenomenon due to the process of bioresorption. The amorphous phase undergoes much faster biodegradation than the crystalline one. In order to increase the bioactivity of the HAp, Zn particles were introduced on the surface of the coating. The TEM microstructural analysis in conjunction with the qualitative analysis of the EDS chemical composition showed that the binding of the Zn particles within the HAp matrix had diffusive character, which is very favourable from the point of view of the quality of the adhesion and the bioactivity of the coating. In the case of such a complex structure and due to its very porous nature, micromechanical analysis was carried out in situ in SEM, that is, by microhardness measurements of both the HAp matrix and the Zn particle. It was shown that the average value of HAp microhardness was 4.395GPa ± 0.08, while the average value of Zn microhardness was 1.142GPa ± 0.02.

Improved wear resistance of AISI-4340 steel by Ti–Nb–C–N and MoS2 composite coating by cathodic cage plasma deposition

A cathodic cage plasma deposition (CCPD) system was used to deposit titanium-niobium-carbon-nitrogen (Ti–Nb–C–N) and molybdenum-disulfide (MoS2) composite coating with a modification in the lid of the cathodic cage by inserting composite material rings in the holes. For this purpose, the combination of mixed material rings made up of (80 % TiO2+10 % graphite and 10 % Nb2O5) and 100 % MoS2 were uniformly inserted into the cage lid holes. The nano-hardness of untreated steel (2.7 GPa) was upgraded to 9.3, 11, and 12.4 GPa by composite coating at 300, 350, and 400 °C, respectively. The coating comprised TiN, Ti2N, NbN, NbC, and MoS2 phases, irrespective of the processing temperature. The thickness of the composite coating was 10.5, 13.8, and 18.6 μm. The wear volume (245 × 10−6 mm3) was reduced significantly in each condition, specifically at 400 °C temperature (∼0.1 × 10−6 mm3). The friction coefficient was smoother and lower by coating deposition, whereas the machining temperature during the wear test was reduced. The novelty of this work is that besides improving hardness, wear resistance is also improved due to the self-lubrication performance of the composite coating. In addition, the coating deposition by this system is a single-step process; less treatment time is required, and treatment is relatively low-cost.

Giant auxetic behavior in remote-plasma synthesized few-layer tungsten semicarbide.

Auxetic crystals exhibiting highly positive lateral expansivity when stretched are an experimentally elusive class of two-dimensional (2D) materials with tremendous potential, for example in the direct transduction of electric signals and the compensation of thermal expansion at the nanoscale. 2D tungsten semi-carbide (W2C) was theoretically predicted to exhibit giant auxetic behavior, but has yet to be synthesized, as the corresponding full carbide (WC) is energetically favored under thermodynamic equilibrium synthesis processes such as furnace-based chemical vapor deposition. Here, we report on an ad hoc designed dual-zone remote plasma deposition system specially conceived to grow tungsten carbides out of thermodynamic equilibrium with well-tuned ratios of W and C precursors. We report on the specific conditions under which this system allowed for the synthesis of flakes of few-layer tungsten semicarbide (FL-W2C) which are 2D in nature due to retained periodicity at the mesoscopic level in a Stranski-Krastanov growth process. Under applied strain, FL-W2C 2D crystals exhibit the strongest auxetic behavior observed to date. This result suggests that the theoretically predicted high negative Poisson's ratio of single-layer W2C, also extends to thicker FL-W2C flakes that are retaining the periodicity of the 2D crystal at the mesoscopic level.

Improved mechanical and wear properties of AISI-420 steel by cathodic cage plasma vanadium nitride deposition

In this study, a cathodic cage plasma deposition (CCPD) system equipped with a vanadium cathodic cage is used to deposit vanadium nitride coating on AISI-420 steel. This study aims to improve the tribological and mechanical properties. Specifically, this system is used because it can deposit not only a hard coating but also form a nitrogen diffusion layer that can enhance the load-bearing capacity of the sample and coating adhesion with the substrate. The XRD shows that vanadium nitride (VN) coating is polycrystalline, with a favored orientation along the (200) plane. The SEM results depict that at 673 K, the surface consists of uniformly disseminated spherical nanoparticles agglomerate to form coralloid granular nitrides. At 723 K, polygonal particles are uniformly distributed over the entire surface. The thickness of vanadium nitride films is 0.6 and 1.1 μm for 673 K and 723 K temperatures. The hardness of the sample increased up to 3 times over the untreated sample, whereas mechanical properties, including elastic modulus, and hardness-elastic modulus ratios are upgraded, specifically at 723 K. Remarkably, the wear rates are reduced more than ten times, and a significant decrease in friction coefficient due to the deposition of VN coating. After the ball-on-disc wear analysis, the wear track is smooth and narrow for coated samples and still covered with vanadium and nitrogen elements, which indicates deposited coating is not detached from the substrate. It shows that VN coating can be deposited effectively to enhance the mechanical and tribological properties of AISI-420 steel.

Structure and Dielectric Properties of Poly(vinylidenefluoride-co-trifluoroethylene) Copolymer Thin Films Using Atmospheric Pressure Plasma Deposition for Piezoelectric Nanogenerator.

This study investigates the structural phase and dielectric properties of poly(vinylidenefluoride-co-trifluoroethylene) (P[VDF-TrFE]) thin films grown via atmospheric pressure (AP) plasma deposition using a mixed polymer solution comprising P[VDF-TrFE] polymer nano powder and dimethylformamide (DMF) liquid solvent. The length of the glass guide tube of the AP plasma deposition system is an important parameter in producing intense cloud-like plasma from the vaporization of DMF liquid solvent containing polymer nano powder. This intense cloud-like plasma for polymer deposition is observed in a glass guide tube of length 80 mm greater than the conventional case, thus uniformly depositing the P[VDF-TrFE] thin film with a thickness of 3 μm. The P[VDF-TrFE] thin films with excellent β-phase structural properties were coated under the optimum conditions at room temperature for 1 h. However, the P[VDF-TrFE] thin film had a very high DMF solvent component. The post-heating treatment was then performed on a hotplate in air for 3 h at post-heating temperatures of 140 °C, 160 °C, and 180 °C to remove DMF solvent and obtain pure piezoelectric P[VDF-TrFE] thin films. The optimal conditions for removing the DMF solvent while maintaining the β phases were also examined. The post-heated P[VDF-TrFE] thin films at 160 °C had a smooth surface with nanoparticles and crystalline peaks of β phases, as confirmed by the Fourier transform infrared spectroscopy and XRD analysis. The dielectric constant of the post-heated P[VDF-TrFE] thin film was measured to be 30 using an impedance analyzer at 10 kHz and is expected to be applied to electronic devices such as low-frequency piezoelectric nanogenerators.

Development of thin film coatings with polypyrrole (ppy) by physical plasma deposition technique (PAPVD) for electrochemical capacitor

In this study, new polypyrrole films (ppy) were synthesized using a physical plasma deposition (PAPVD) system; where the equipment design and methodology for plasma-assisted pyrrole polymerization were improvement. The morphology, functional groups, and thermal stability of the polymer network films were characterized by X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) techniques, respectively. The electrochemical properties of the films as capacitor were evaluated by cyclic voltammetry and electrochemical impedance spectroscopy. The results observed by SEM showed that the ppy 100W-1 and ppy 100W-2 films present uniformity in their structure. The analyses of TGA and DSC confirmed the improvement in stability; meanwhile for 100W-1 film, the presence of ppy bonds was corroborated by XPS. Plasma-activated ppy 100W-1 film exhibited higher capacitance and minor Rct resistance than that obtained for ppy 100W-2 film. The specific capacitances values of ppy 100W-1 and ppy 100w-2 films are 196 and 150 F/g in 1 M KCl. After charging and discharging tests of 1000 cycles at 5 mA cm−2 current density of ppy 100W-1 film retains 89% of its initial capacitance. Therefore, ppy 100W-1 film showed to be a promising material for use as an electrochemical capacitor.

Stable Indium Tin Oxide with High Mobility.

Indium tin oxide (ITO) is widely used in a variety of optoelectronic devices, occupying a huge market share of $1.7 billion. However, traditional preparation methods such as magnetron sputtering limit the further development of ITO in terms of high preparation temperature (>350 °C) and low mobility (∼30 cm2 V-1 s-1). Herein, we develop an adjustable process to obtain high-mobility ITO with both appropriate conductivity and infrared transparency at room temperature by a reactive plasma deposition (RPD) system, which has many significant advantages including low-ion damage, low deposition temperature, large-area deposition, and high throughput. By optimizing the oxygen flow during the RPD process, ITO films with a high mobility of 62.1 cm2 V-1 s-1 and a high average transparency of 89.7% at 800-2500 nm are achieved. Furthermore, the deposited ITO films present a smooth surface with a small roughness of 0.3 nm. The stability of ITO films to heat, humidity, radiation, and alkali environments is also investigated with carrier mobility average changes of 19.3, 4.4, and 4.7%, showcasing strong environmental adaptability. We believe that stable ITO films with high mobility prepared by a low-damage deposition method will be widely used in full spectral optoelectronic applications, such as tandem solar cells, infrared photodetectors, light-emitting diodes, etc.

Large area, rapid, and protein-harmless protein–plasma-polymerized-ethylene coating with aerosol-assisted remote atmospheric-pressure plasma deposition

Our goal is to establish a remote-plasma-based aerosol-assisted atmospheric-pressure plasma deposition (RAAPD) system for depositing protein–plasma-polymerized-ethylene coatings. The method of RAAPD is using plasma to polymerize ethylene and add protein aerosol at downstream region to coat protein–plasma-polymerized-ethylene on substrate. We investigated effects of different mixing, mesh, deposition distance, gas flow, voltage, and frequency. Results showed that downstream-mixing method reduced heat effects on protein. The optimal coating was achieved when using mesh, at a close deposition distance, with high flow rate of protein aerosol, and under high voltage. Compared with current methods, impacts of RAAPD include reducing effects of plasma generated heat, reactive species, and UV on protein, and deposition will not be limited by electrode area and substrate material.

Measurement of the Surface Electrical Resistance of SnO2:F Thin Films

In this work, thin films of tin oxide doped with fluorine and of nominal surface resistance between 30 Ω and 40 Ω were deposited by RF sputtering in a plasma deposition system and their surface electrical resistances were evaluated for different conditions. To measure the resistivity of the fluorine-doped tin oxide film using an aluminum PAD with the same thickness and the same width as the film, a Minipa digital multimeter acting as an ammeter, a DC voltage source, and wires with banana-alligator connectors were used at six intervals (between the aluminum measuring tips and the PADs). Thus, a linear approximation and verification of the resistance value for each measured distance were undertaken. Resistances ranging from 44.10 Ω/ to 88.10 Ω/ for separations of 6 and 1 cm, respectively, were found. With the values obtained, the respective graphs were plotted for the six separations. The four-point method was employed to obtain four measurements (M1 to M4), and the curves of voltage as a function of the current were obtained. Values of resistance ranged from 11.4 Ω (M4) to 29.1 Ω (M3).

Synthesis of polyvinylidene fluoride film using novel atmospheric pressure plasma deposition with direct-injection nozzle

This paper proposes a new atmospheric pressure plasma (APP) deposition system with direct-injection nozzle (modified-APPDS) for depositing the polyvinylidene fluoride (PVDF) thin film. In the modified-APPDS, the key parameters such as length of guide-tube, distance of bluff-body, gas composition, and gas flow rates are examined for generating glow-like intense plasma. As a result, the intense glow-like plasma generated broadly by the modified-APPDS can uniformly deposit the PVDF thin film, which is confirmed by field emission-scanning electron microscopy (FE-SEM) and Fourier transforms-infrared spectroscopy (FT-IR).

Influence of Ag/Ca ratio on the osteoblast growth and antibacterial activity of TiN coatings on Ti-6Al-4V by Ag and Ca ion implantation

Titanium nitride (TiN) coating has many prominent properties such as chemical stability, high hardness, excellent wear properties, biocompatibility and so on, which make it as a potential candidate for inhibiting the release of toxic ions and improving mechanical properties of dental and orthopedic implants made by titanium‑aluminum‑vanadium (Ti-6Al-4V). Of course, the biologically inert and poor antibacterial property of TiN limits its application. In this work, TiN coating was firstly deposited on the surface of Ti-6Al-4V substrate to inhibit its toxic ions release. Then, silver (Ag) and calcium (Ca) with different ratios were implanted into TiN coatings by plasma immersion ion implantation and deposition (PIII&D) system to enhance both osteoblast growth and antibacterial activity on the surfaces of TiN coatings. The results show that TiN coating inhibits the release of toxic ions such as Al and V. X-ray photoelectron spectrometer (XPS) and X-ray diffraction (XRD) analyses proved the presence of Ag, Ca on the surface of Ag and Ca implanted TiN (Ag/Ca-TiN). Scanning electron microscopy (SEM) was used to observe the surfaces' morphologies of samples, which takes advantage of distinct detectors to visualize secondary and back-scattering electrons. The protein adsorption experiment showed that the protein adsorption capacities increased with the increase of Ca ratio. When the results of antibacterial and cell adhesion tests were combined, Ag/Ca(2:1)-TiN indicated the best osteoblast adhesion and antibacterial activity in vitro due to the synergistic effect of Ag and Ca. The improved inhibiting ability in releasing toxic ions, osteoblast adhesion and antibacterial activity of the Ag/Ca(2:1)-TiN suggest that it might be a potential choice for surface medication of orthopedic implants clinically.

Plasma‐based VAD process for multiply doped glass powders and high‐performance fiber preforms with outstanding homogeneity

AbstractAn innovative approach using the vapor axial deposition (VAD), for the preparation of silica‐based high‐power fiber laser preforms, is described in this study. The VAD uses a plasma deposition system operating at atmospheric pressure, fed by a single, chemically adapted solution containing precursors of laser‐active dopants (e.g., Yb2O3), glass‐modifier species (e.g., Al2O3), and the silica matrix. The approach enables simultaneous doping with multiple optically active species and overcomes some of the current technological limitations encountered with well‐established fiber preform technologies in terms of dopant distribution, doping levels, and achievable active core diameter. The deposition of co‐doped silica with outstanding homogeneity is proven by Raman spectroscopy and electron probe microanalysis. Yb2O3 concentrations are realized up to 0.3 mol% in SiO2, with simultaneous doping of 3 mol% of Al2O3.

Glass-like carbon films grown by pulsed hollow cathode via plasma immersion ion implantation and deposition

Plasma Immersion Ion Implantation and Deposition (PIII&D) systems based on pulsed metal tubes are a very promising technique to deposit diamond-like carbon and correlated thin films. A hollow cathode plasma can be appropriately used to locally deposit glass-like carbon films on small substrates by means of PIII&D. The morphology, microstructure, roughness as well as the investigation of the chemical structure of the as-deposited graphitic films outside the pulsed tube are reported. By the described PIII&D setup, the power of the discharge plasma can be properly adjusted to produce a range of disordered carbon films. But their structures are not so extensively changed since high temperatures (around 900 °C) are inherent in these conditions. Furthermore, there is a minimum power required to sustain the hollow cathode discharge when small tubes are used. Moreover, an additional effect caused by the intense bombardment of secondary electrons outside the tube can account for the growing of more ordered and rougher graphitic carbon coatings. We have then found that those nanostructured glass-like carbon films are strongly dependent on the power of the produced plasma that impinges on the substrate surface increasing its temperature.

Carbon films deposition as protective coating of titanium alloy tube using PIII&D system

The purpose of this work is to deposit carbon films inside titanium alloy tube of small diameter, in order to increase the corrosion resistance of its inner surface. The use of carbon films as protective coating can increase the lifetime of the tubes used in propulsion and thermal control systems of satellites. They can also inhibit the permeation of corrosive species, originated from the fuels and the cooling fluids, between the film-metal interface. Titanium alloy tube with 11 mm diameter and 150 mm length, with one side closed configuration was placed inside a vacuum chamber and pulsed to a high energy voltage. Carbon film deposition was performed by using a Plasma Immersion Ion Implantation and Deposition (PIII&D) system. The hollow cathode discharges (HCD) were produced with pulses of 2 kV, 15 A, 20 μs, and 500 Hz of repetition rate, using a RUP-6 pulser. The maximum temperature measured at the surface of tubes was about 1000 °C. The as-deposited carbon films were analyzed in terms of their microstructure, chemical composition, surface morphology and thickness. The surface characterization of the carbon films were carried out by means of Raman Spectroscopy, Field Emission Gun Scanning Electron Microscopy (FEG-SEM), Atomic Force Microscopy (AFM) and Potenciodynamic Polarization tests. The experimental results show an interesting change on the chemical structure of the as-deposited carbon films, when the deposition time varied from 30 min to 240 min, resulting in thicker and quite adhered films on the inner surface of tubes. In addition, the changes on the microstructure, seen by SEM analysis, as well as the ID/IG variation indicate that nanocrystalline graphite (NC-G) films can be deposited on the inner surface of titanium tubes by using this type of PIII&D system.

Improved Adhesion of TiAlSiN Nanocomposite Coatings on Cemented Carbide Substrate by Pre-Implantation

TiAlSiN coatings were deposited on YT 15 cemented carbide substrate by reactive direct current magnetron sputtering (DCMS) in a Plasma Immersion Ion Implantation and Deposition (PIII&D) system. The pre-implantation step and the coating deposition were carried out in the same experimental facility. In this article the effects of pre-implantation of several different elements (N, C, and O) were investigated. The adhesion strength, hardness, micro-structure, element concentration, depth profile, and the formation of coatings after the PIII experiments were characterized by a wide variety of techniques such as Rockwell indentation, scratch test, nano-indentation measurement, X-ray diffraction, energy dispersive spectroscopy, and Auger electron spectroscopy. The results showed that the adhesive strength of TiAlSiN coatings was significantly improved on samples pre-implanted with N and O whereas only slightly improved with pre-implantation of C. Additionally, the microstructure and mechanical properties of the TiAlSiN coatings were also altered through pre-implantation. The improved adhesion could be explained by the grain refinement and surface energy enhancement of the substrate by pre-implantation.

Arc Plasma Deposited Copper and Gold Nanoparticles on FTO Substrate for Electrochemical Reduction of CO2

A composite of copper and gold nanoparticles was deposited using arc plasma deposition on the conductive FTO substrate for the electrochemical reduction of CO2 . The use of arc plasma deposition system allows the nanoparticles to be implanted onto the substrate as opposed to the commonly used methods of vacuum deposition or electro deposition. This unique structure reduced the CO2 to produce formic acid with up to 60% faradaic efficiency. Copper and gold nanoparticles have never previously been reported to produce formic acid with such high efficiency, suggesting that the co-deposition technique of implanted nanoparticles can provide an interesting future avenue in the field of electrochemical reduction of CO2 . The surface analysis of the electrodes is presented here along with potential dependent faradaic efficiency of the electro catalysis.

Influences of post-heating treatment on crystalline phases of PVDF thin films prepared by atmospheric pressure plasma deposition

This paper systematically investigates the effects of the post-heating treatment on the structural characteristics of the polyvinylidene fluoride (PVDF) thin film that is deposited as the high-density thin films with nanoparticles by improving the sufficient nucleation of PVDF solution by atmospheric pressure plasma (APP) deposition system. The surface morphology of PVDF thin film was measured by using scanning electron microscopy (SEM), and structural characteristic of PVDF thin film was systematically investigated by X-ray diffraction (XRD) and Fourier transforms-infrared spectroscopy (FT-IR) with respect to different post-heating conditions in order to reduce the N,N-dimethylformamide (DMF) element and enhancing the crystalline phase of PVDF thin film. As the post-heating temperature was increased, the amount of bubble and bubble size were decreased. This means that the DMF solution is almost removed from the post-heated PVDF thin film, and the PVDF nanoparticles are clearly observed on the surface of PVDF thin film synthesized by APP deposition method. In FT-IR spectra, the peak intensity at 1669 cm−1 for -C = O by DMF solution highly decreases after post-heating treatment, and the crystalline phases of the PVDF thin film have mainly two phases (α and β phases), which indicates the peaks at 975 and 1402 cm−1 for α-phase and the peak at 1072 cm−1 for β-phase, respectively.

Fabrication of DLC nanoparticle clusters by μ-wave oven based plasma reactor with acetylene diluted in air precursor

This work developed a microwave oven based plasma reactor operated under vacuum pressure. This microwave plasma deposition system used to deposit diamond-like carbon (DLC) thin film on silicon substrate. System is custom-made and economically provides a very inexpensive way to conduct film deposition experiments by using a household microwave oven as a microwave source to get plasma discharge. DLC thin films were successfully deposited on silicon substrates by pure acetylene (C2H2) plasma. Plasma species composed of; CN, N2, CO, C2, and H are presented revealed by Optical Emission Spectroscopy. Energy Dispersive X-ray analysis indicated that the deposited film composed of carbon atoms 46.25% and silicon atoms 53.75%. Raman analysis showed D-band, G-band and nanocrystalline diamond band with sp3-hybridization contained in the films in the range of 48.75–64.08% that composed of chemical bonding; CC, CO, CN, CN, CO, CNH, NO, OH and HOH, analyzed by XPS technique. XRD indicated that the grown films are cubic diamond (1 1 1) crystallography and formed in coral-like clusters from nanoparticles of a mixture between sp2 and sp3 hybridization with high porosity in surface texture that introducing the hydrophobic property on the grown DLC surface by changing the hydrophilic property of smooth silicon substrate surface.

Effects of helium concentration on microcrystalline silicon thin film solar cells deposited by atmospheric-pressure plasma deposition at 13.3 kPa

An atmospheric-pressure plasma deposition system was developed and used to deposit intrinsic hydrogenated microcrystalline silicon (μc-Si:H) thin films for μc-Si:H thin film solar cells. The helium (He) gas concentration in plasma increased Raman crystallinity (Xc) of μc-Si:H, which was a critical parameter to determine photovoltaic performance. In addition, dependence of Xc on the He concentration is shown to be closely related to the atomic hydrogen flux during film growth, which is evidenced by plasma diagnostics derived from in situ optical emission spectroscopy measurements. Those analysis contributed to achieve impressive photovoltaic performance – namely, a power conversion efficiency of 4.60%, an open-circuit voltage of 0.52 V, a short-circuit current density of 13.62 mA/cm2, and a fill factor of 0.65, which is the first experimental demonstration of μc-Si:H thin film solar cells fabricated with the atmospheric-pressure plasma deposition under very high working-pressure regime at 13.3 kPa.

Carbon Thin Film on Silicon by Microwave Plasma

This work aims to develop a low pressure microwave plasma deposition system to coat carbon thin film on silicon substrate. The system use a commercial microwave oven as a microwave source to get plasma discharge. The vacuum pressure was achieved by two stage rotary vane vacuum pump which is capable to reach ultimate pressure at 2×10-1 Pa under borosilicate chamber glass. The carbon thin films was successfully deposited on silicon substrate by pure acetylene plasma with gas flow rate 30 ml/min at total operating pressure of -70 cmHg reading by analog dial vacuum gauge, using microwave power at 1,200 Watts and deposit time at 150 seconds. Raman analysis showed peak at around 1336.20 cm-1 (D-peak) and 1611.87 cm-1 (G-peak), by utilizing ID and IG can be determined that there are 43.22% of sp3 contained in deposited film. Energy Dispersive X-Ray analysis indicated that the deposited thin film compose of carbon atoms 82.00 at% and silicon atoms 18.00 at%. The morphology and the thickness of the film was investigated by scanning electron microscope and atomic force microscope, respectively.