Ar Gas Research Articles

Effect of pulse width on deposition of diamond-like carbon on high-power pulsed magnetron sputtering

A diamond-like carbon (DLC) film was deposited using high-power pulsed magnetron sputtering. The effect of pulse width on the deposition of DLC film was investigated under constant peak power density or average power density to clarify the densification mechanism of DLC film. The maximum hardness of 25 GPa analyzed by nanoindentation was obtained using Ar gas without negative substrate bias voltage at pulse width 30 μs and a peak power density of 1.5 kW cm−2. The flux and energy of C+ and Ar+ incident to the DLC film was evaluated by using energy-resolved and time-resolved mass spectrometry to clarify the relation between the input power to the target and the behavior of produced ions. The change in hardness is well correlated with the ion flux ratio C+/Ar+. This result indicates that a flux and energy of Ar+ as well as C+ is a key parameter to characterize the microstructure of DLC film.

Process gas dependence of spin–orbit torque in Pt/NiO/Co structures

Recently, to enlarge spin-current-induced phenomena, such as spin–orbit torque (SOT) in a ferromagnet (FM)/heavy-metal (HM) bilayer, enhancement of spin-current transmittance by inserting an antiferromagnetic insulator at the FM/HM interface has been extensively studied. In this study, we have investigated the SOT modulation in a Pt/NiO/Co structure in which the NiO layer was deposited using Ar and Xe process gases. Consequently, the quality of the NiO layer could be regulated. An increase in the damping-like SOT efficiency was observed by inserting the 1 nm NiO layer in the Ar type while it monotonically decreased with an increase in the NiO thickness in the Xe type. Significant temperature dependence of the SOT efficiency in the Ar type indicates that thermal magnon largely contributes to the spin-current propagation. X-ray diffraction measurement result suggests that the difference in crystallinity of the NiO layer between the Ar and Xe types attributes to the different SOT modulations.

Surface tension and viscosity of binary ionic liquid mixtures from high vacuum up to pressures of 10 MPa

In the present study, we investigated the surface tension and viscosity of binary ionic liquid (IL) mixtures at or close to saturation conditions from high vacuum conditions up to elevated pressures. We studied four different mixtures of 1,3-bis(2-(2-methoxyethoxy)ethyl)imida-zolium iodide ([(mPEG2)2Im]I) and 1-methyl-3-octylimidazolium hexafluorophosphate ([C8C1Im][PF6]) with [C8C1Im][PF6] mole contents between (4.6 and 49.8) mol%. Argon (Ar) gas of relatively low solubility was used to vary the applied pressure between (0.1 and 10) MPa. For temperatures from (303 to 363) K, the surface tension obtained by the pendant-drop (PD) method was used to determine the saturated liquid viscosity from surface light scattering (SLS). These studies are complemented by additional PD measurements under ultraclean high vacuum (HV) conditions in a second setup. At about 0.1 MPa, the surface tension and viscosity of the IL mixtures show negative deviations from a linear mixing rule based on the molar bulk composition, which is more pronounced at lower temperatures. The surface tension values at 0.1 MPa and under HV agree with each other and lie closer to the values of [C8C1Im][PF6] that has a distinctly lower surface tension than [(mPEG2)2Im]I and is surface-active. For the equimolar IL mixture at 303 K, an increase in the pressure up to 10 MPa has a negligible influence on the viscosity, while it causes a distinct reduction in the surface tension compared to the value at 0.1 MPa. The pressure-dependent relative change for the viscosity of the ternary mixtures of the two ILs and Ar corresponds well to the mean values of the positive and negative relative changes observed for the two binary [(mPEG2)2Im]I-Ar and [C8C1Im][PF6]-Ar subsystems, respectively. For the surface tension, the absolute changes at a given pressure are very similar regardless of the IL bulk composition, suggesting a similar weak Ar enrichment at the gas–liquid interface.

Characteristics of a pulsed hollow cathode discharge operated in an Ar+O[formula omitted] gas mixture and deposition of copper nickel oxide thin films

A hollow cathode discharge with a CuNi (Cu50Ni50) cathode is operated inside a vacuum chamber with Ar gas flowing through its nozzle. O2 gas is admitted to the vaccum chamber. Typical Ar+O2 gas pressures are in the range of 2–50 Pa. The energy distribution of plasma ions is investigated with the help of energy-resolved mass spectrometry. Singly charged Ar+ and molecular O2+ ions are the most abundant ionic species. Deposition rate and heat flux to a substrate increase as function of discharge current. At high pressures, the deposition rate is further increased by the directional gas flow, which becomes more focused onto the substrate. Deposited and annealed thin films are analysed by X-ray diffraction and Raman spectroscopy. As-deposited films are composed of a mixed CuxNi1−xO cubic phase with a preferred (111) orientation. Upon annealing at 600 oC, the mixed CuxNi1−xO phase separates into two sub-phases composed of NiO and CuO. Annealed films display a photoelectrochemical (PEC) activity as a photocathode. The PEC activity deteriorates with time, however. This behaviour is related to the reduction of CuO to Cu2O.

Development of gas-injected pulsed plasma CVD method using Ar/C2H2 mixed gas for ultra-high-rate diamond-like carbon deposition

A diamond-like carbon (DLC) fabrication method with a greater deposition rate and simple equipment configuration facilitates to introduce DLC coating technology to industrial processes. In this study, a gas-injected pulsed plasma CVD method using a single plasma source is proposed as an ultra-high-rate deposition method for DLC films. A gas mixture of Ar and C2H2 was injected into a vacuum chamber through a gas nozzle, and plasma in the chamber was generated by applying a negative pulse voltage to the substrate stage. The gas velocity in the chamber was calculated using computational fluid dynamics simulations. DLC films with a nanoindentation hardness of 17.5 GPa were fabricated on a limited area of a Si substrate at a deposition rate of 2480 nm min−1. The deposition rate of the DLC films can be further improved by optimizing the conditions of the Ar partial pressure ratio, gas velocity, and stage applied voltage.

Raman scattering studies of Si/B4C periodic multilayer mirrors with an operating wavelength of 13.5 nm

In order to obtain mirrors with a minimum value of residual stress, periodic multilayer mirrors composed of Si/B4C were deposited by magnetron sputtering with change in pressure of sputtering Ar gas. The microstructure and phase of Si and B4C was manipulated by the pressure of Ar gas which overall affected the stress in the mirrors. The minimum stress was obtained at higher pressure of sputter Ar gas, which showed the formation of amorphous boron, amorphous B4C, free carbon atoms and amorphous carbon structure in the B4C layers, investigated by Raman scattering spectroscopy. In Raman spectroscopy, a transverse optical (TO) mode of amorphous Si was shifted to lower frequency with increase in Ar gas pressure, which indicated relaxation of stress, also confirmed by the curvature measurement of mirrors. However, in the case of high residual stress, the amorphous B4C was a prominent phase in this layer and the frequency of the TO mode of amorphous Si was blue-shifted. Microstructure and stress affected the interfaces and modulation of the periodicity of the Si/B4C mirrors, investigated by secondary ion mass spectroscopy, which influenced the reflectivity of the mirrors.

Mechanical milling/alloying, characterization and phase formation prediction of Al0.1–0.5(Mn)CoCrCuFeNi-HEA powder feedstocks for cold spray deposition processing

In the present work the synthesis of multicomponent nanocrystalline Al0.1- 0.5(Mn)CoCrFeNi HEA powder feedstocks by mechanical alloying (MA) through high energy ball milling to produce HEA coatings with cold spraying were studied. Pure (>99.5) elemental powders of Al (Mn), Co, Cr, Cu, Fe & Ni were mixed in predetermined ratios and mechanically alloyed under Ar gas in a Planetary Ball Mill. MA HEA powder feedstocks were characterized by optical microscopy, SEM+EDAX, XRD & XPS to determine powder particle size, shape & distribution, particle surface condition, chemical composition, crystal & phase structures & microstructures. MA-processed Al-HEA powder feedstocks exhibited tri-modal particle size distribution (PSD) while Mn-HEA had four distinct PSD modes. Fine size fraction of the MA- HEA powders contained A2/B2 (BCC) harder phases with lattice parameters of 2.8831 and .2.8690 Å, respectively and coarse size fraction contained (ductile) softer A1 phase/Cu-rich regions combined (FCC) having a lattice parameter of 3.6181 Å. The ratio of the phases varied depending on the Al and Mn contents in the powder. For higher aluminium contents, there was more disordered A2/B2 phases and less disordered A1 phase in Al0.1–0.5 HEA powder feedstocks. A1 phase contained Fe, Cr, Co and Ni; A2 phase contained Fe, Cr; and B2 phase contained Al, Ni elements in Al0.1–0.5 HEA powder feedstocks. There were passive surface oxide films on the rough surfaces of MA HEA powder feedstocks consisting of a main mixture of surface oxides such as Al2O3, MnO, Cr2O3, Mn2O3, and minor oxides such as CuO, Fe2O3, NiO, Fe3O4, and a few CoCr2O4 spinel oxide. Dual FCC-dual BCC phase prediction of thermodynamic stable phase formation criteria reported in the literature on MA-HEA powder feedstocks were consistent with the experimental results of the present study.

Surrogate-based Shape Optimization of Immersion Nozzle in Continuous Casting

In continuous casting, molten steel is fed from the tundish into the mold through the immersion nozzle. In the immersion nozzle, inclusions mainly composed of alumina present in the molten steel adhere and accumulate, it causes limitation of continuous castings. To prevent the nozzle clogging, Ar gas is blown into the immersion nozzle. However, Ar bubbles flow into the mold along with the molten steel and become trapped in the solidifying shell, causing bubbling defects of the slab. To suppress bubbling defects, it is effective to keep Ar bubbles away from the solidification interface or to use molten steel to wash away Ar bubbles that have adhered to the solidification interface. The molten steel flow in the mold is greatly affected by the shape of the immersion nozzle. In this paper, we consider the optimization of the shape of the immersion nozzle to reduce Ar bubbles trapped in the solidifying shell. A numerical model of molten steel flow and heat transfer solidification in the mold is combined with an optimization method. In the optimization process, Ar bubbles trapped in the solidifying shell are evaluated by a neural network to improve the calculation speed. The application of this method to the search for immersion nozzle shape is also reported, and the effectiveness of the obtained nozzle shape in reducing Ar bubbles is discussed.

Analytical modelling to study the magnetic field-assisted growth of graphene in the reactive plasma

A theoretical model has been developed to study the impact of a magnetic field on the growth of vertically aligned graphene sheets using plasma deposition techniques. The present model incorporates the dynamics of negatively charged electrons and positively charged ions and active neutral radicals of reactive gases in the complex plasma comprising Ar, C2H2, and H2 gases and deposition of these gaseous phase plasma species in the form of vertically aligned graphene sheets. The dynamics and deposition of the plasma particles can be controlled or enhanced by various process parameters and use of external magnetic field is one of the most promising way to enhance the deposition of species. In the present work, the growth of vertical graphene in a plasma environment has been studied with and without external magnetic field. The analytical simulations of the developed model revealed the significant enhancement in the growth of vertically aligned graphene sheets when magnetic field is applied in the plasma reactor. Our findings of the analytical simulations are in line with existing experimental observations.

YÜKSEK FREKANSLI RF PLAZMALAR İLE PMMA FİLMLERİNİN ISILABİLİRLİĞİNİN İYİLEŞTİRİLMESİ

Poly(methyl methacrylate) (PMMA) has a wide variety of applications due to its attractive physical and optical properties. Due to its hydrophobic (water-repellent) character, the surface of PMMA should be modified before being used in applications. In this study, the surface of PMMA films were modified by 40.68 MHz high frequency CCP (capacitive-coupled plasma) RF system with nitrogen (N) and argon (Ar) gases. The experiments carried out under various plasma powers while the pressure and treatment time were kept constant. The wettability of the plasma treated surfaces was analyzed with contact angle and surface free energy (SFE) measurements. Also, the change in the chemical structure of the surfaces was investigated with X-ray photoelectron spectroscopy (XPS). The results showed that all plasma treatments enhanced the hydrophilicity of the surfaces and the lowest contact angle values obtained at high plasma power. The total SFE of the treated surfaces increased with power and the main contribution to total SFE came from polar components. The polar groups formation on the surface after plasma treatment was proved with XPS results. Hence, it was found that high frequency CCP RF plasmas can be used effectively to obtain hydrophilic polymer surfaces.

Enhancing the efficiency and short-circuit current of silicon solar cells using MoO3 as emitter layers

Molybdenum trioxide (MoO3) is an interesting material for optoelectronic applications due to their low-cost, simple processing and thickness-dependent band gap tunability. So far, however, few have been reported to date the impact of post-synthesis annealing on the electrical characteristics of the MoO3 in silicon heterojunctions solar cells. Here, we show that Ar annealing treatment can promote the crystallization of MoO3 nano structures (NSs) and enlarge the MoO3 NSs crystalline size. In this work, thermal evaporation technique is used to prepare MoO3 NSs to be used as emitter layers in silicon heterojunctions solar cell. Then, the as-synthesized sample is annealed under Ar gas flow at 600 °C to improve structural and optical properties of the sample. It is noted that by Ar treatment at 600 °C, we found its quantum efficiency (QE) enhances from 8.41 % to 10.74 %, showing a 27.70 % increase due to a significant enhancement of short circuit-current (ISC). Furthermore, EQE of Ag/Ar treatment MoO3/n-type Si/Ag showed significant enhancement entire spectra range especially in visible region respect to the bare cell.

Relationship between Osteoblast Proliferation and the Surface Properties of Polymer-like Carbon Films Deposited at Different Ar/CH4 Mixed-Gas Ratios in the Radio-Frequency Plasma CVD Process

In the deposition of polymer-like carbon (PLC) films on Si substrates via radio-frequency plasma CVD (RF-PCVD), the effect of the Ar/CH4 gas mixture ratio on the bio-interface of the PLC films remains unclear and the effectiveness of introducing Ar gas must be proven. In this study, five types of PLC films are prepared on Si substrates via RF-PCVD with an Ar/CH4 gas mixture. The effects of the Ar/CH4 gas ratio on the structure, surface properties, and osteoblast proliferation of the PLC films are investigated. The PLC film structure is graphitized as the hydrogen content in the PLC film decreases with the increasing Ar gas ratio. Based on in vitro cell culture tests, a PLC film with a higher Ar gas ratio promotes the osteoblast proliferative potential after 72 h compared with a PLC film with a relatively low Ar gas ratio. Moreover, the surface roughness and hydrophilicity of the PLC film increase with the Ar gas ratio. Accordingly, we demonstrate the effectiveness of Ar gas incorporation into the RF-PCVD process to promote the biological responsiveness of PLC films. PLC coatings are expected to be widely applied for surface modification to improve the mechanical characteristics and biological responses of orthopedic implant devices.

Measuring Temporal Variation of Concentration of ALD Precursor TEMAZ in Process Chamber Using UV Absorption Method

The UV light densitometer was developed to measure concentration of gases having absorption in the ultraviolet region using UV absorption method. The developed densitometer was applied to monitor temporal variation of concentration of ALD precursor TEMAZ introduced into a chamber, where TEMAZ was introduced alternately with purge Ar gas to simulate ALD process. We could successfully capture temporal variation of gas concentration such as time delay in arrival of gas in the chamber due to presence of gas flow. Such phenomenon cannot be measured by the pressure gauge.

Tritium release behavior from neutron-irradiated FLiNaK mixed with Ti powder

• FLiNaK mixed with Ti powder was irradiated by mainly thermal neutrons. • Amounts of TF, T2 and T2O released from the FLiNaK by heating were investigated. • Chemical form ratio of released tritium was approximately TF:T2:T2O = 5:70:25. • Approximately 70% of tritium was released as T2O from the FLiNaK exposed to air. • Ti powder mixed to the FLiNaK contributed to the suppression of tritium release. FLiNaK is used as a simulant of FLiBe and FLiNaBe which are promising candidates of liquid blanket material in fusion reactors. In this study, to obtain useful knowledge for tritium release behavior from molten salts such as FLiBe and FLiNaBe, tritium release experiments were carried out for neutron-irradiated FLiNaK containing Ti powder. The solid-state samples were irradiated by mainly thermal neutrons at Kyoto University Research Reactor, and tritium release behavior as TF and T 2 by heating in Ar gas flow was observed and additionally total amount of released T 2 O was obtained. Most of the tritium generated inside the FLiNaK was released to the gas phase even when the FLiNaK was in a solid state at a temperature below its melting point. From the molten FLiNaK unintentionally exposed to air, approximately 70% of tritium was released as tritiated water vapor. The amount of TF released from the molten FLiNaK was considerably less than that of T 2 . This result is consistent with the tendency of tritium release from neutron-irradiated FLiNaBe in our previous study. The ratio of chemical form was approximately TF:T 2 :T 2 O = 5:70:25. It was experimentally confirmed that the Ti powder added to the salt contributes to the suppression of tritium release from the molten salt.

Numerical strategy for solving the Boltzmann equation with variable E/N using physics-informed neural networks

A novel strategy to solve the Boltzmann equation with variable reduced electric field by using an artificial neural network (ANN) is introduced, where is the electric field and is the gas number density. In this method, the ANN learns the electron velocity distribution function (EVDF) for arbitrary in the Boltzmann equation. Thus, the ANN can calculate the EVDFs in the training range of without additional training. For validation of the ANN, the EVDFs in each Ar and SF6 gas were calculated with the trained ANN. The electron energy distribution function and electron transport coefficients calculated from the EVDF quantitatively agree with those from another ANN for a single and those from a Monte Carlo simulation, proving the validity of the present method.

ON THE COMPARISON OF REACTIVE-ION ETCHING MECHANISMS FOR SiO2 AND Si3N4 IN HBr + Ar PLASMA

This work investigated the influence of component ratio in the HBr + Ar gas mixture on electro-physical plasma parameters, steady-state densities of active species and reactive-ion etching (RIE) kinetics for SiO2 and Si3N4 under conditions of inductive RF (13.56 MHz) discharge. The combination of plasma diagnostics by Langmuir probes and plasma modeling indicated that an increase in Ar content at constant gas pressure and input power a) caused an increase in electron temperature and densities of charged species; b) results in increasing ion bombardment intensity; and c) leads to the nearly proportional decrease in Br atoms density and flux. It was found that variations of SiO2 and Si3N4 etching rates vs. mixture composition are qualitatively similar while the maximum difference in corresponding absolute values takes place in pure HBr plasma. The analysis of RIE mechanisms was carried out using model-predicted data on fluxes of ions and bromine atoms. It was found that the dominant SiO2 etching mechanism is the ion-assisted chemical reaction which is characterized by the nearly-constant rate in the range of 0–80% Ar due to an increase in the effective reaction probability. That is why the noticeable intensification of physical sputtering with increasing Ar fraction in a feed gas causes the only weak growth of obtained SiO2 RIE rate. Oppositely, the Si3N4 etching process is mainly contributed by the physical sputtering while the efficiency of ion-stimulated chemical reaction is limited by the low reaction probability. This provides both slower etching process (especially in Ar-poor plasmas) and stronger sensitivity of etching rate to the change in mixture composition. For citation: Efremov A.M., Betelin V.B., Kwon K.-H. On the comparison of reactive-ion etching mechanisms for SiO2 and Si3N4 in HBr + Ar plasma. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2023. V. 66. N 6. P. 37-45. DOI: 10.6060/ivkkt.20236606.6786.

The cracking growth behavior of a sensitized Alloy 800H in supercritical water

The cracking growth behavior of a sensitized Alloy 800H in supercritical water (SCW) was studied at temperatures between 450 °C and 550 °C. Crack growth rates (CGRs) were measured in SCW environments with various dissolved gasses and in inert argon environment to separate the effects of corrosion and creep on the overall cracking susceptibility. Creep cavities were widely observed at the grain boundaries ahead of the crack tip in both SCW and Ar gas environments. Results show that both corrosion and creep contribute to the cracking behavior of sensitized Alloy 800H, and the corrosion contribution depends on the corrosion potential of the SCW environment. The stress corrosion cracking and creep CGRs increase with temperature, and their apparent activation energies are similar. The data support the conclusion that cracking was mostly controlled by creep and oxidization at the crack tip.

Study of Atmospheric Pressure Plasma Temperature Based on Silicon Carbide Etching.

In order to further understand the excitation process of inductively coupled plasma (ICP) and improve the etching efficiency of silicon carbide (SiC), the effect of temperature and atmospheric pressure on plasma etching of silicon carbide was investigated. Based on the infrared temperature measurement method, the temperature of the plasma reaction region was measured. The single factor method was used to study the effect of the working gas flow rate and the RF power on the plasma region temperature. Fixed-point processing of SiC wafers analyzes the effect of plasma region temperature on the etching rate. The experimental results showed that the plasma temperature increased with increasing Ar gas until it reached the maximum value at 15 slm and decreased with increasing flow rate; the plasma temperature increased with a CF4 flow rate from 0 to 45 sccm until the temperature stabilized when the flow rate reached 45 sccm. The higher the RF power, the higher the plasma region's temperature. The higher the plasma region temperature, the faster the etching rate and the more pronounced the effect on the non-linear effect of the removal function. Therefore, it can be determined that for ICP processing-based chemical reactions, the increase in plasma reaction region temperature leads to a faster SiC etching rate. By processing the dwell time in sections, the nonlinear effect caused by the heat accumulation on the component surface is effectively improved.

Thin film deposition of tungsten nitride on SS 316 L surface using DC-Sputtering technique

316L stainless steel (SS) is an alloy steel that is not easily corroded, so it is widely used for biomaterial applications. In addition to being resistant to corrosion, 316L SS is also inexpensive when compared to other medical metals. However, 316L SS has relatively low hardness and wear resistance, thus this weakness must be improved. By heat treatment, it is impossible to improve the SS alloy, so other techniques must be applied. In this study, improvement of surface hardness of 316L SS by coating tungsten nitride (WN) using DC-sputtering method has been conducted. The sputtering process was implemented by varying the sputtering pressure of 1.8×10-2, 2.3×10-2 and 2.8×10-2 Torr. Furthermore, the composition ratio of Ar and N2 gases were varied i.e 70:30, 80:20 and 90:10 with a voltage of 4 kV and deposition time of 120 minutes. After the coating process, hardness testing was carried out using the Vickers hardness test with a load of 25 gf. The formation of tungsten nitride was also analyzed using XRD. The highest hardness in order of 938.64 VHN is achieved at a pressure of 2.8×10−2 Torr and the ratio of Ar:N2 gas was 90:10. From the XRD analysis, the layer formed is a W+WN layer which is shown at the peaks at a scattering angle of 2Ɵ is 43.55º; 2Ɵ is 39,530º; 2Ɵ is 56,880º; and 2Ɵ is 71,550º.

High-temperature compression tests of Ti(C, N)–70 wt% W cermet and isothermal forging of Inconel 718 alloys using cermet molds

In this study, TiC0·5N0.5–70 wt% W cermet specimens consisting of a core–rim grain structure with coherent interfaces and the binder phase were prepared by blending TiC0·5N0.5 and W powders with particle sizes of less than 1 μm and then spark plasma sintering the blended powders. The compression tests of the cermet specimens were conducted in the temperature range of 1873 K–2073 K in a vacuum and under Ar gas flow conditions. At all testing temperatures, this cermet exhibited much higher yield stress than MoSiBTiC and MoNbTaVW high-entropy alloys, which are some of the structural materials showing the highest strength at temperatures exceeding 1873 K. After isothermal upset forging of commercially available solid-solution heat-treated Inconel 718 alloy specimens with a diameter of 5 mm and a height of 5 mm using cermet molds at loads of 40 kN and 10 kN at 1273 K and 1373 K in a vacuum, respectively, their average grain size (2 μm) was found to be much smaller than that before forging. Such fine microstructures were assumed to be formed by dynamic recrystallization during forging.