Ion Cleaning Research Articles

Molybdenum low-resistance thin-film resistors for cryogenic devices

Abstract We present a study of thin-film Mo resistors for NbN electronics operating at cryogenic temperatures. The key step is the 0.5–1.5 keV ion cleaning–activation of NbN before Mo deposition, which allows us to obtain a high-quality Mo/NbN interface. This, together with an additional Al bandage layer in the area of the contact pads, allows us to reduce the contact resistance below 1 Ω. The quality of the interfaces is confirmed by transmission electron microscopy and x-ray reflectometry.

Effects of ion-plasma treatment temperature of the aluminium coating on the structure and phase composition of the VT6 titanium alloy

In this study, we studied the effects of aluminum coating treatment temperature on the microstructure and phase composition when applied to a VT6 titanium alloy substrate within a low-pressure arc discharge plasma environment. The ion-plasma treatment was conducted at 450 and 500 °C, employing argon shielding, while the aluminum coating was deposited using the vacuum-arc process, resulting in a coating thickness of ~3 μm. Microstructural analysis was performed using a scanning electron microscope, and the structural and phase composition were examined using X-ray diffraction (XRD) imaging in symmetric imaging mode with CuKα radiation. Our findings demonstrate that the application of the aluminum coating initiates the formation of a near-surface α-stabilized layer, extending up to 2.5 μm in thickness due to the heat generated during the ion cleaning process. Subsequent ion-plasma treatment further results in the development of a TiAl3 intermetallide site, reaching thicknesses of up to 1.5 μm, while the α-stabilized region expands to 5.5 μm. Higher temperatures during the treatment process contribute to an increase in the thickness of these aforementioned layers and also lead to the emergence of an intermediate TiAl intermetallic layer.

The effects of air plasma and argon cluster ion cleaning on quartz and calcite surfaces – Implications for rock-water-gas wettability

Wettability is a crucial factor controlling fluid transport and distribution in reservoir rocks. A significant discrepancy of reported contact angles for air plasma cleaned calcite-water-gas systems are evident from the literature. This work focuses on finding possible explanations for these discrepancies by studying the effect of two surface cleaning methods on the surface chemistry, which was utilized by employing XPS and TOF-SIMS analysis. Observed chemical changes were then discussed in relation to wettability. The two methods are i) air plasma cleaning, and ii) argon cluster ion cleaning. Air plasma cleaning exhibits a degree of reactivity towards the surface. The two surface cleaning methods are very similar in regard to efficiency. Air plasma cleaning of calcite surfaces resulted in an accumulation of low levels of metal oxides/hydroxyls. It was found that both quartz and calcite remain intact after surface cleaning, that is, neither of the cleaning processes degrade the material. It is suggested that the discrepancies in reported contact angle values is a combined effect of several factors, such as different degrees of i) surface roughness, ii) unavoidable adventitiously adsorbed hydrocarbons on the sample surfaces, and iii) non-native bulk components such as metal oxide/hydroxyls and biomarker material.

Improved waveforms for Barrier-Bucket systems

Barrier-Bucket (BB) systems provide a method to apply a short gap to a coasting beam. This is utilized for different applications, like ion cleaning, or to compensate the medium energy loss caused by internal experiments. BB-cavities are broadband cavities, and the applied signal is commonly a short sine burst, followed by a flat section at zero voltage. Since the transfer function of the BB-system is usually neither flat nor linear, it is common to predistort the signal to obtain the desired shape at the rf gap. Nevertheless, the resulting waveform still has a ripple in the flat section. This is due to the lowpass characteristic of the amplifier and the sharp edges at the ends of the sine, which lead to an infinite number of harmonics. This paper provides better suited BB-waveforms, which are designed with a finite number of harmonics from the beginning. It is shown that a much better flatness can be achieved than for a conventional BB-waveform, without sacrificing any performance. These advanced waveforms are currently used at the hadron synchrotron COSY at Forschungszentrum Jülich, leading to improved BB-bunch shapes, in particular for electron-cooled beams.

Substrate surface processing in gas vacuum arc discharge

Problem. Preparation of the surface before the deposition of vacuum arc coatings is of great importance, as it affects not only the adhesive properties of the obtained coatings, but also the physical and mechanical properties of the substrate surface layer. The processes of ions interaction with the substrate surface during its ionic cleaning, before the deposition of coatings, have been relatively little studied and are almost not described in the literature. Goal. In this work, some of their features are considered in relation to the surface preparation of materials before the deposition of vacuum arc coatings. Methodology. The nature of the plasma interaction with the substrate material is determined by the ions energy and their flow density, other things being equal. The energy of the ions treating the substrate consists of their initial energy and the energy acquired in the Debye layer adjacent to the substrate when a negative potential is applied to it. The value of the potential at which the processes of condensation or sputtering are balanced is determined mainly by the nature of the vaporized material. When the value of the substrate potential increases, the deposited particles and its material are sputtered. At the same time, atoms on the substrate that are weakly connected to it, various impurities are removed, substrate temperature increases, especially in its surface layers. Results. The work investigates the influence of various metals and gases used to clean the surface of substrates made of cubic boron nitride PcBN and steels on the surface morphology. It was established that the use of gases (argon, nitrogen) for cleaning the surface of dielectric materials, in particular PcBN, showed the best results, which subsequently leads to an increase in the adhesion of the vacuum arc coating to the substrate. Practical value. The obtained results of investigation are of great practical importance. They can be used for the increasing of tool life and productivity of mechanical engineering.

Influence of ion cleaning of front facet of 9xx nm InGaAs/AlGaAs/GaAs diode lasers on their maximal output power

This paper reports on the study of the effect of ion cleaning of emitting cleaved facet of 9xx nm laser diodes based on InGaAs/AlGaAs/GaAs on their limiting radiation power. Measured maximal power and the percentage of laser diodes with a visual manifestation of catastrophic optical damage in the active region were analyzed. It was found that short-term (1 min) low-energy treatment with argon and hydrogen ions does not lead to changes in the parameters of laser diodes, while treatment with nitrogen ions results in a decrease in the maximal output power and an increase in the probability of catastrophic optical damage. It is also shown that the use of an ion source based on electron cyclotron resonance leads to better results compared to a End Hall source or radiofrequency source with inductively coupled plasma, due to the lower energy of the ions. Keywords: Ion cleaning, laser diode, catastrophic optical damage, maximal output power, passivation, nitridization.

АКТИВАЦІЯ ПРОЦЕСІВ МАСОПЕРЕНОСУ ПРИ ДИФУЗІЙНОМУ ЗВАРЮВАННІ У ТЛІЮЧОМУ РОЗРЯДІ

The paper examines the effect of ion treatment of contacting surfaces on the activation of mass transfer processes during diffusion welding of metals. Using the example of welding titanium alloys, stainless steel with armco-iron and steel 45, it was determined that the preliminary ion cleaning of the welded surfaces in a glow discharge in an argon environment significantly reduces the time of the incubation period associated with the diffusional absorption of oxygen layers adsorbed on the surface, and provides a reduction in time isothermal aging until the maximum strength of the connection is reached.It is also shown that to ensure the strength of the welded joint at the level of strength of the base metal, it is sufficientto form a transition layer with a thickness of 3...4 microns, which experiences the largest plastic deformations at the first stage of welding. A further increase in the thickness of the transition layer practically does not lead to an increase in strength.Ionic activation of the surfaces to be joined, which is carried out in a vacuum chamber immediately before welding, provides an increase in the diffusion coefficient in the transition zone by approximately three times compared to standard surface preparation by washing them in solvents, and by almost two orders of magnitude compared to the self-diffusion coeffi-cient of the elements. It was established that when welding stainless steel with steel 45, the efficiency of ion activation of surfaces decreases, which is due to the reductive nature of the interaction of carbon contained in the composition of steel 45 in a significant amount, with oxides in the welding zone.It is shown that the most effective application of ionic activation of surfaces during diffusion welding of metals that arehomogeneous or similar in chemical composition, when there is no such important factor of intensification of mass transfer processes as the concentration gradient of elements in the welding zone, as well as metals that contain a small amount of reducing elements, in particular, carbon

Влияние ионной очистки поверхности излучающего скола 9хх нм лазерных диодов на основе InGaAs/AlGaAs/GaAs на их предельную мощность излучения

This paper reports on the study of the effect of ion cleaning of emitting cleaved facet of 9xx nm laser diodes based on InGaAs/AlGaAs/GaAs on their limiting radiation power. Measured maximal power and the percentage of laser diodes with a visual manifestation of catastrophic optical damage in the active region were analyzed. It was found that short-term (1 min) low-energy treatment with argon and hydrogen ions does not lead to changes in the parameters of laser diodes, while treatment with nitrogen ions results in a decrease in the maximal output power and an increase in the probability of catastrophic optical damage. It is also shown that the use of an ion source based on electron cyclotron resonance leads to better results compared to a End Hall source or radiofrequency source with inductively coupled plasma, due to the lower energy of the ions.

Threshold Ion Energies and Cleaning of Etch Residues During Inductively Coupled Etching of NiO/Ga2O3 in BCl3

BCl3 is an attractive plasma etchant for oxides because it is a Lewis acid used to scavenge native oxides on many semiconductors due to the strong B–O bonding. We investigated BCl3-based dry etching of the NiO/Ga2O3 heterojunction system. BCl3/Ar Inductively Coupled Plasmas produced maximum etch rates for NiO up to 300 Å.min−1 and 800 Å.min−1 for β-Ga2O3 under moderate plasma power conditions suitable for low damage pattern transfer. The selectivity for NiO: Ga2O3 was <1 under all conditions. The ion energy threshold for initiation of etching of NiO was between 35–60 eV, depending on the condition and the etch mechanism was ion-driven, as determined by the linear dependence of etch rate on the square root of ion energy incident on the surface. By sharp contrast, the etching of Ga2O3 had a stronger chemical component, without a well-defined ion energy threshold. The as-etched NiO and Ga2O3 surfaces show chlorine residues, which can be removed on both materials by the standard 1NH4OH: 10H2O or 1HCl: 10H2O rinses used for native oxide removal. According to the location of the Cl 2p3/2 peak, the Cl is ionically bonded.

Multichannel probe measurements in a helium plasma in a hollow cathode discharge

A multichannel scheme and a technique for measuring the parameters of electrons in a discharge plasma in a hollow cathode with several Langmuir probes in different regions of the plasma simultaneously are developed. In the experimentally implemented system, the current-voltage characteristics (IVCs) of the probes are formed by combinations of noise and periodic voltage waveforms, which ensures a high dynamic range and accuracy of the measurement results. In different regions of the plasma space, the electron energy distribution functions (EEDFs), average energies <E>, plasma potentials Up, and electron concentrations Ne are determined simultaneously. The capabilities of the system are demonstrated for various probe locations. It is shown that in order to obtain consistent data, special processing (cleaning) of the probes is required, the states of which change with time. Methods of electronic and ionic cleaning and their combinations have been studied. If the probes are located in a plane equidistant from the cathode and anode at distances between them comparable to the transverse dimensions of the plasma, the EEDF shape and the Ne value are approximately preserved, but the potential value Up changes.

Dissolved metal ion removal by online hollow fiber ultrafiltration for enhanced size characterization of metal-containing nanoparticles with single-particle ICP-MS

Single particle-inductively coupled plasma mass spectrometry (SP-ICP-MS) is a powerful tool for size-characterization of metal-containing nanoparticles (MCNs) at environmentally relevant concentrations, however, coexisting dissolved metal ions greatly interfere with the accuracy of particle size analysis. The purpose of this study is to develop an online technique that couples hollow fiber ultrafiltration (HFUF) with SP-ICP-MS to improve the accuracy and size detection limit of MCNs by removing metal ions from suspensions of MCNs. Through systematic optimization of conditions including the type and concentration of surfactant and complexing agent, carrier pH, and ion cleaning time, HFUF completely removes metal ions but retains the MCNs in suspension. The optimal conditions include using a mixture of 0.05 vol.% FL-70 and 0.5 mmol/L Na2S2O3 (pH = 8.0) as the carrier and 4 min as the ion cleaning time. At these conditions, HFUF-SP-ICP-MS accurately determines the sizes of MCNs, and the results agree with the size distribution determined by transmission electron microscopy, even when metal ions also are present in the sample. In addition, reducing the ionic background through HFUF also lowers the particle size detection limit with SP-ICP-MS (e.g., from 28.3 to 14.2 nm for gold nanoparticles). This size-based ion-removal principle provided by HFUF is suitable for both cations (e.g., Ag+) and anions (e.g., AuCl4−) and thus has good versatility compared to ion exchange purification and promising prospects for the removal of salts and macromolecules before single particle analysis.

Electron emission properties of silver oxide and its impact on the secondary emission yield of air-exposed silver

Surface oxidation, contamination and adsorption are commonly considered as three leading factors of secondary electron yield (SEY) increase for metals exposed to various environments. Whereas, the influence of these three factors on SEY is different for diverse metal materials. To discover the SEY dependence on surface oxidation for silver, a group of silver oxide (Ag2O) and silver coatings are therefore prepared. Experimental results show the SEY of Ag2O is just about 0.1 higher than that of silver coating whether before or after ion cleaning, and SEY difference becomes smaller under oblique incidence, which indicates the surface oxidation may not be the major causes of SEY increase for air-exposed silver. To further verify the speculation, various surface conditions are achieved on silver surface. Microscopic analysis reveals the adsorptions and contaminations can be effectively removed by heating treatment, meanwhile, SEY is remarkably decreased. Furthermore, the treatment of ion cleaning eliminates all the surface additions and achieves a superlative cleanliness for silver sample, the SEY peak value of air-exposed silver decreases from 2.61 to 1.73 after ion cleaning for 10 min, and to 1.70 after ion cleaning for 30 min, which indicates the surface oxidation contributes little to the SEY raise of air-exposed silver. The SEY dependence on the thickness of contamination layer is also theoretically explained. This work does a systematic research on how the surface oxidation and modification influence SEY of silver, which makes significant sense for comprehending the SEE characteristics of silver with various surface conditions.

Analysis Method of Oxygen Reduction Reaction Rate in PEFC Using Pt-Sputtered Catalyst

IntroductionTo establish the generic model of the cathode catalyst layer (CCL),[1] the intrinsic oxygen reduction reaction (ORR) rate which does not include mass transfer resistance through the CCL should be formulated. Neglecting the backward reaction, the ORR rate per geometric area, r gc, is proportional to oxygen partial pressure, p O [Pa], as follows: r gc = k gc p O [mol/(m2·s)][1] (1) k gc = k gc0exp(–E/RT–E c/b c) = k gc0exp{–(E+4aFE c)/RT} (2)where k gc is the reaction rate constant per geometric area [mol/(Pa·m2·s)], E c is the cathode electromotive force [V], E is the activation energy [J/mol], T is temperature [K], b c is the Tafel slope [V] which is proportional to temperature, and 4a is the transfer coefficient.The objective of this study is to develop a measurement method of temperature, relative humidity (RH) and E c dependencies of the intrinsic ORR rate constant using platinum-sputtered catalyst.ExperimentalA Japan Automobile Research Institute (JARI) standard cell whose active area was 50 mm × 50 mm or modified to 20 mm × 20 mm was used in experiments. The membrane-anode assembly (MAA, Eiwa Corp.) was composed of a proton exchange membrane (PEM, Nafion® NR-212), an 8.3‒9.8 μm thick (0.19–0.24 mg/cm2) anode which was made of Pt/Vulcan® XC-72 catalyst (Pt/C weight ratio: 1) with a Nafion® ionomer (ionomer/carbon weight ratio: 0.74). Pt thin-layer cathode (0.054 mg/cm2) was prepared by sputtering (AOV, SPAD-4240UM, Ar atmosphere, 5 Pa, 100 ℃, for 50 minutes) on the microporous layer (MPL) on a carbon paper (SIGRACET-GDL 29 BC, 235‒238 μm thick) to eliminate mass transfer resistance through the CCL.[2] Before sputtering, MPL substrates were cleaned using argon plasma in order to eliminate the hydrophobized coatings on the MPL surface. The MAA and Pt thin-layer cathode were stacked as shown in Fig. 1. A carbon current collector had a single serpentine flow channel, the width and depth of which were 1.0 mm and the pitch of the ribs was 2.0 mm. H2 and O2 were humidified at 60–80 oC. H2 and O2 flow rates were 600 and 300 cm3/min, respectively. The cell was operated at 65–80 oC. The pressure at the cell outlet was ambient pressure (ca. 1 atm).Results and DiscussionFig. 2 shows the SEM images of the surface of MPL on a carbon paper before and after 50 min sputtering. Pt particles whose diameter is approximately 10 nm are observed. Next, Fig. 3 shows the temporal changes in the substrate weight (MPL) while ion cleaning. The slope from 25 to 135 minutes is less than a half of the slope from 0 to 25 minutes. It indicates that 30 minutes is enough to remove almost all of hydrophobized coatings on the MPL surface. In addition, Fig. 4 shows Pt loading is proportional to the sputtering time.[3] 40-minute ion cleaning and 50-minute sputtering were employed in this study.Fig. 5 shows the Tafel plot at different temperatures. The current density at a fixed E c increased with raising temperature as expected from Eq. (2). From these polarization curves, the k gc parameters, E, 4a and k gc0 were determined by using nonlinear least square method under the assumption that ORR rate is proportional to RH. As a result, E = 25 kJ/mol, 4a = 0.48 and k gc0 = 1.3 mol/(Pa m2 s) are determined. Fig. 6 shows the Arrhenius plot of recalculated results shown by dashed lines with observed values. The ORR rate dependencies on temperature, RH and E c were properly reproduced so the ORR rate parameters were appropriately determined.Conclusions Temperature, RH and E c dependencies of ORR rate constant, k gc, were measured using platinum-sputtered catalyst in order to determine ORR parameters, E, 4a and k gc0 which do not include the effect of mass transfer resistance through the CCL. From experimental results at different temperatures, ORR dependency on temperature was measured and ORR rate parameters were appropriately determined.AcknowledgementThis work was supported by the New Energy and Industrial Technology Development Organization (NEDO), Japan.References Kawase et al., AIChE J., 63(1), 249–256 (2017).Kageyama et al., 232nd ECS Meeting (National Harbor, Oct., 2017), #1387.Murase et al., 31st ISChE (Chiang Mai, Dec. 1, 2018), OC06.Hu et al., ChemElectroChem, 6(10), 2659‒2666 (2019). Figure 1

Controlling the Low-temperature Ionic Purification of a Silicon Surface by Electron Spectroscopy

A comparative study is carried out for etching a surface with negative and positive ions, and the results show completely opposite physical processes occur on a silicon surface. Irradiation with positive ions exhibits oxide removal, while irradiation with negative ions shows an intense oxidation of the sample surface. Technology for low-temperature ion cleaning and the electron-spectrometric control of silicon wafers has been developed. This technology has been shown that only irradiation with caesium ions followed by annealing at 650 °C leads to an atomically clean silicon surface for several minutes, which is dependent on the pressure of residual gases under vacuum. After cleaning in a vacuum of 10− 9 Pa, the silicon surface begins to oxidize again within 10 min.

Formation and investigation of characteristics of thermoresistive structures based on vanadium oxide films

The processes of reactive magnetron sputtering of a V target in Ar/O2 gas mixture are investigated. It was found that when using a pulsed current for sputtering and a pressure in the chamber less than 0.06 Pa, the intensities of the emission lines of vanadium at 437.922 nm, argon at 750.386 nm, and oxygen at 777.417 nm with a change in the oxygen concentration in Ar/O2 gas mixtures (ГO2) have no hysteresis and unambiguously depend on the parameters of the sputtering process, which makes it possible to stabilize the process without using feedback systems. By monitoring the sputtering process by optical emission spectroscopy and depositing films on a rotating substrate of diameter 100 mm, vanadium oxide (VOx) films with nonuniformity thickness less than ±2.4 % and surface resistance less than ±2.5 % were obtained. Studies by transmission line method of the influence of the parameters of the reactive magnetron sputtering and subsequent annealing at O2 pressure of 0.04 Pa on the characteristics of thermoresistive structures based on VOx films showed that when the contacts are deposited without ion cleaning, the current-voltage characteristics (IV) and the dependence of the resistance on the length of resistors R(L) are nonlinear, which indicates the presence of a potential barrier in the contacts. Preliminary ion cleaning can significantly improve the linearity of the IV characteristic. The most linear IV characteristics were obtained for Ti contacts. However, the specific contact resistance of the VOx/Ti contact increases with an increase in the oxidation state of the VOx films and reaches ρc = 0.1 Ohm·m2 at the specific resistance of vanadium oxide ρ = 0.1 Ohm·m. The analysis of the dependences of the temperature coefficient of resistance (TCR) and ρ of VOx films on the annealing temperature showed that, upon annealing, ρ and TCR slightly decrease, i. e. there occurs a partial deoxidation of the films. However, unlike annealing at atmospheric pressure, there are no temperature regions at which a sharp decrease in the resistivity and TCR occurs.

Practical and Economical Effects of the Use of Screen Meshes for Steel Nitriding Processes with Glow Plasma

The dynamically developing energy sector forces technologists to create new materials that meet the increasingly higher mechanical, chemical, and electrical requirements. The paper relates to the method of reducing the energy consumption of the plasma nitriding process of austenitic steels. The method proposed by the authors involves the modification of nitriding technology in glow plasma. It consists of introducing perforated screens between the anode and nitrided surface made of a material with a composition similar to the processed material and the use of an HF power supply with controlled mean current generating negative voltage peaks of about 1000 V. Nitriding is carried out in a nitrogen-hydrogen atmosphere. The processed material has a negative potential in relation to the surrounding plasma and strongly negative in relation to the vacuum chamber jacket. The actual treatment is preceded by ionic cleaning of the surface of the detail and heating it to the temperature that activates the diffusion processes. The authors analyse the dynamic distribution of electric fields generated at the surface of the nitrided material with different configurations of the cathode-sample-screen system, trying to find the correlation of treatment parameters with the parameters of the nitrided layer. A significant influence of the screening meshes on the depth of the obtained diffusion layers containing nitrogen was found. The oscilloscopic measurements of the plasma in the boundary layer allowed for the observation of voltage peaks, probably leading to an increase in the peak kinetic energy of nitrogen ions and their easier penetration into the material. The work is of a cognitive nature and is probably one of the first to look for relationships between the dynamic electrical parameters of plasma and the efficiency of nitriding.

Diffusion Bonding Performance of Copper Target for 300mm Integrated Circuit

Ultra-pure copper sputtering target is a key material widely used in large-scale integrated circuits with 90-28 nm feature size. The copper target for 300 mm integrated circuit requires a reliable diffusion bonding between the ultra-pure copper target and the copper alloy backplate. The bonding ratio and bonding strength of diffusion bonding should reach over 99% and 80 MPa respectively. In this paper, the ascendant structure of electron beam welding united diffusion bonding with high quality was designed. The ultra-pure copper target and the C18000 copper alloy backplate were machined to coordinating size, meanwhile the backplate underwent surface treatment of toothed/smooth, ion cleaning, magnetron sputtering coating, then the combination of target and the backplate was proceeded electron beam welding and diffusion bonding. Metallographic microscope, scanning electron microscope (SEM), mechanical tensile machine, C-scan flaw detector were used to analyze the bonding properties including interface microstructure, bonding strength and bonding ratio. The results show that the bonding ratio of copper target was above 99%, and the bonding strength was up to 80-160 MPa.

Optimization of Heat Treatment Cycles in Sub-atmospheric LiF-NaF-KF Based Fluoride Ion Cleaning for Removing Oxide Layers in Cracks of IN738-LC

An improved Fluoride Ion Cleaning (FIC) process required for removing all oxide layers by a molten mixture of alkaline fluoride salts under sub-atmospheric pressure was developed and applied to oxide layers on the cracks formed on the surface of Inconel 738-LC samples. This method is directly characterized by filling up the cracks with a molten mixture of alkaline fluoride salts (LiF-NaF-KF) overheated under sub-atmospheric pressure and subsequently, by injecting hot hydrogen gas into the process chamber. The effect of cleaning time on the microstructure of the finished surface was studied in time durations up to 120 min in intervals of 30 min using cross-sectional micrographs and elemental distribution maps. In accordance with the amount of mass loss and microstructural studies during the cleaning process, the optimum cleaning time was suggested to be 90-120 min. Perquisite microstructural outcome shows that in the suggested cleaning condition, all oxide scales in the cracks would be removed without any extra damage to the gamma prime depleted layer, which is a necessary layer for preventing sample oxidation before repair. In this regard, subsequent brazing operations need an oxide-free surface.

REDISTRIBUTION OF SPUTTERED MATERIAL IN A PLANE IONPLASMA SYSTEM WITH AN ABNORMAL GLOW DISCHARGE

The redistribution of the flow of sputtered material of a target (cathode) between the collector and the target in a plane-parallel electrode system with an anomalous glow discharge is analyzed in the kinetic approximation. Sputtering is the result of bombardment of the target by gas ions accelerated in the near-cathode space charge layer and by fast neutral atoms formed as a result of resonant ion charge exchange. Sputtered atoms partially return to the target due to collisions with gas molecules. The formulas were obtained, which were confirmed in the experiment that makes it possible to correctly estimate the ratio of the sputtered material flows deposited on the collector and the target. The results of the work are used to calculate the parameters of the processes of coating deposition and ion cleaning of the target under conditions of the anomalous glow discharge.

DISCHARGE CHARACTERISTICS OF THE MAGNETRON SYSTEM FOR SPUTTERING, DEPOSITION, AND NANOTECHNOLOGY APPLICATIONS

Magnetron sputtering is known for years as a powerful tool for coating deposition of cutting tools and machine parts. However the experimental measurements of the magnetron discharge parameters are still necessary to provide a consumer of the magnetron system with the reliable characteristics. A voltage-current relation is the most applied characteristic of the discharge, and it is described as the power low of a type U = U0 + aIn, where U and I are the voltage drop and the discharge current, respectively, and U0 and n are constant. First part of the research is dedicated to the experiments conducted in the magnetron setup provided with the titanium cathode in a vacuum chamber filled with argon or argon-nitrogen mixture, and the constants are determined for the particular geometry of the magnetron sputtering system. The obtained results can be used to choose the operation modes for the traditional applications of the magnetron discharge such as ion cleaning and heating of the non-magnetic workpieces arranged on the cathode, as well as for the sputtering deposition of the titanium and titanium nitride coatings on the surfaces of the workpieces located above the magnetron cathode. In the next part of the research the novel application of the magnetron for production of carbon nanostructures is considered. For the purpose, a layer of expanded graphite is arranged on the magnetron cathode, and the discharge is initiated in oxygen atmosphere. It was found that for the time interval of a few hours the discharge is described as a superposition of the typical magnetron glow with arc spot generation, and the intensity of the arcs is not decreased with time. At that, the arc initiation was accompanied with the formation of clusters of the graphite cathode. The process is explained in terms of the cathode spot generation at the interaction of the arc plasma with the non-melting material. This process can be beneficial for the development of the plasma reactors for the large-scale production of the carbon species at the low gas pressures suitable for the magnetron discharge operation. Thus, the magnetron sputtering systems provided with the expanded graphite cathode can be considered as the tool to grow carbon nanospecies in the arc discharge cathode spots.