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CrAlN coatings were synthesized on pre-plasma nitrided M2 high speed steels using different ion current densities. The effect of plasma nitriding pretreatment on the microstructures and tribological properties of composite CrAlN coatings had been studied. The results showed that the nitriding efficiency could be significantly enhanced by higher ion current density. The thickness of nitrided layer increased from 43 μm to 63 μm with the increase of ion current density. The nitrided layers without either compound layer or grain boundary precipitation were produced with all experimental ion current densities. Radial cracks also appeared at the Rockwell-C indentation edge of the composite CrAlN coating due to the conformal effect. Moreover, radial cracks of the composite coatings originated from the hard and brittle nitrided layer. The highest interfacial adhesion of the composite CrAlN coating reached 105 N. Furthermore, the wear resistance of CrAlN coating was improved by combining nitriding pretreatment with coating deposition, and the composite coating (PN 4 /CrAlN) possessed the superior wear resistant. [ABSTRACT FROM AUTHOR]

The micro Hall thruster μHT-1 is designed for space gravitational wave detection missions, and the beam characteristics of the thruster are studied by experiments. A Faraday probe mounted on a three-dimensional moving platform is designed for diagnosing to obtain the beam current density distribution, and the operating conditions of the discharge voltage and the mass flow rate are adjusted in the range of 700∼1200 V and 0.1–0.5 sccm, respectively. In addition, the study further analyze the variation trends of total beam current, discharge current, utilization rate, divergence angle and others. The test results indicate that the μHT-1 thruster can work stably in a wide range of operating conditions, and the beam current expresses a good axisymmetric distribution. Meanwhile, the beam current density gradually decreases along the axial direction and spreads along the radial direction. The current utilization efficiency fluctuates from 53.4 % to 67.7 % when the power is adjusted in the range of 1.45–5.76 W, and the divergence angle increases from 41.3 ° to 56.7 °. The total beam current of the thruster shows a linear increase characteristics with the enhancing of the anode flow and the discharge voltage. • A new design, the outer diameter is 20 mm and the inner diameter is 15 mm • Work stably in a wide range of operating conditions. [ABSTRACT FROM AUTHOR]

The paper focuses on measurements of the total energy flux and normalized energy flux onto the substrate during high power impulse magnetron sputtering (HiPIMS) in a wide range of the pulse duration and discharge current. Al, Cr and Ti targets with a diameter 76 mm are used for sputtering. HiPIMS parameters include 1 kW discharge power, 15 to 150 А discharge current, 0.4–10 kHz pulse frequency, and 5–100 μs pulse duration. It is shown that the use of short pulses leads to ∼40 and 70% growth in the total energy flux onto floating and biased (−100 V) substrates, respectively. The energy per unit volume of the deposited coating increases by several times, if the pulse duration and the duty cycle are reduced. The paper examines reasons for the increased total and normalized energy fluxes onto the substrate observed after the pulse parameter modulation in the sputtering process. • Total and normalized energy fluxes onto the substrate are measured during HiPIMS. • Energy fluxes are measured depending on pulse's duration and duty cycle. • Influence of target material on energy fluxes onto the substrate is studied. • Use of short pulses leads to growth in the total energy flux onto substrate. • Normalized energy flux increases if the pulse duration and the duty cycle are reduced. [ABSTRACT FROM AUTHOR]

This paper deals with the electric and hydrodynamic confinement of negative ions in a point-to-plane corona discharge gap. Radial ion current density profiles have been measured on the earthed planar electrode, drilled in the axis of the point. The experimental setup is first validated by comparison with the Warburg's law without injected gas flow rate. The gas injected in the gap and blown from the discharge gap through the hole located at the centre of the plane affects neither the electric field close to the point nor the subsequent electric wind. However, it leads to the confinement of ions flux towards the central symmetry axis in the low electric field region up to a critical gas velocity, which for no more effect is measurable. Hence, electro hydro-dynamics confinement of ions can be achieved by limiting the outward radial expansion of ions to increase ion current densities on specific locations close to the low field planar electrode. [ABSTRACT FROM AUTHOR]

The paper studies a new method in vacuum-arc deposition technology that can be called short pulse-enhanced vacuum arc evaporation (s-PEVAE). This deposition technique combines sub-microsecond high-current pulsed and direct current operation of the arc-discharge source with the pulse frequency of several kilohertz. The high pulse voltage provides a high growth rate and amplitude of discharge current pulses, i.e., over 109 А/s and 1 kА, respectively. During the s-PEVAE process, the arc discharge power can achieve several hundreds of kilowatts. According to optical and probe measurements performed during the titanium evaporation in argon gas, ionization provided by s-PEVAE is higher than that provided by direct current vacuum arc evaporation (DCVAE). In s-PEVAE, the increase in the average discharge power is accompanied by the growth in the average density of the substrate ion current. At the same time, the deposition rate of the titanium coating decreases. All this leads to a significant change in the ratio between the ions bombarding the substrate and metal atoms forming the coating. Along with the substrate bias voltage, this ratio exerts a strong effect on the structure and properties of the deposited coating and can be controlled by the pulse parameters such as amplitude, time, and frequency. • Short pulse-enhanced vacuum arc evaporation (s-PEVAE) process was studied. • High growth rate (109 А/s) and amplitude (1 kА) of discharge current were obtained. • s-PEVAE process was compared with direct current vacuum arc evaporation (DCVAE). • s-PEVAE provided the higher ionization and ion-to-atom ratio than the DCVAE. [ABSTRACT FROM AUTHOR]

Abstract: SiOx thin films synthesized on polycarbonate substrates by low temperature plasma processes are electronically meta-stable because the process temperature (<70 °C) needed to prevent deterioration of the polymer substrate is too low to allow the formation of a thermodynamically stable structure with stoichiometric electronic bonding. Therefore, the surfaces are very active and react chemically with the environment after scratching and pressure. This paper reports a coating method for producing dense structures with high hardness and good optical properties by controlling the ion current density (ion flux). The ion current density (ion flux) on the substrate was controlled by the RF power and additional bias with a bipolar pulsed dc frequency. [Copyright &y& Elsevier]

Abstract: Silicon oxide gas barrier films were deposited on polyethylene terephthalate (PET) substrates by plasma enhanced chemical vapor deposition (PE-CVD) for applications to transparent barrier packaging. The barrier properties of the silicon oxide coated film were optimized by varying the bias conditions and input power in the radio frequency plasma. The plasma diagnostics, ion current density and substrate temperature were characterized by optical emission spectrometry (OES), an oscilloscope and thermometer, respectively. The coating properties were examined by Fourier transform infrared (FT-IR) spectroscopy and the water vapor transmission rate (WVTR). A high intensity of O and H ions and a high ion current density (ion flux) with a low temperature plasma process were found to be suitable for improving the barrier properties of the silicon oxide film coatings. The Si–O cage-like structure adversely affected the gas barrier properties of the deposited coating. The energy provided by ion bombardment (ion flux) can induce changes in the film density and composition similar to those that may occur by the increase in deposition temperature through rf bias. In addition, the film properties depend not only on a high ion current density (ion flux) and input power, but are also related to a silicon oxide film with a widely distributed planar ring size. [ABSTRACT FROM AUTHOR]

Abstract: The combination of microbeam implantation and in-situ micro RBS/channeling analysis in the Rossendorf nuclear microprobe facility enables crystal damage studies with high current densities not achievable in standard ion implantation experiments. Si(100) samples were implanted with 600keV Si+ ions and a fluence of 1×1016 cm−2. Using a beam spot of 200μm×200μm current densities from 4 to 120μA/cm2 were obtained. The substrate temperature was varied between RT and 265°C. The implanted regions were subsequently analysed by micro RBS/channeling with a 3MeV He+ beam having a spot size of 50μm×50μm. Crystal damage up to amorphisation was observed in dependence on the substrate temperature. Above a critical temperature T C no amorphisation occurs. T C was determined for each series of samples implanted with the same ion current density j. It was found that the empirical Arrhenius relation j ∼exp(−E a/kT C), known from standard implantation experiments, is also valid at high current densities. The observed Arrhenius law can be derived from a model of epitaxial crystallisation stimulated by defect diffusion. [Copyright &y& Elsevier]

As shown in previous publications concerning cathodic arc deposition, the vacuum arc as a technological tool can be very complexly influenced by variation of the electrical arc parameters. The pulsed arc current and the resulting ion current influence the formation of the coating. To determine optimised parameters for the deposition process, the dependence on the frequency, on the rate of current rise and on the maximum pulse current in particular were investigated. Using the variation of the output parameters of a pulsed arc power supply, the ion current was steered in its shape and its absolute values. Therefore, the shape of arc current pulses was varied, especially in the phase of rise and fall (triangle, sine, rectangle). Among other things, it was noted that at the beginning of the pulse an excessive increase in ion current is measurable. In order to use this increase for a more effective coating process, experiments were carried out using pulses with controlled slopes and current levels or double pulses of rectangular shape. The examinations have shown that an increase in the ion current ratio in the arc current can be reached by a suitable choice of the electrical parameters. The plasma can be controlled by the electrical parameters of the current source. [Copyright &y& Elsevier]

Abstract: Silicon oxide thin films are transparent protective coatings with anti-scratch, chemical resistant, barrier properties that have recently emerged as one of the prime coating technologies for depositing a range of functional optical coatings on polymer substrates in mobile electronics, digital cameras and other digital applications. Many optically transparent and protective coating materials as well as low temperature plasma processes have been developed for these applications. In this study, amorphous silicon oxide (a-SiO2) thin films were deposited on polycarbonate (PC) substrates by plasma enhanced chemical vapor deposition (PE-CVD) for applications as protective coatings. The coating layer deposited by low temperature plasma processes was electronically meta-stable because the process temperature was too low and the substrate temperature was always<100°C for the formation of a thermodynamically stable structure with a stoichiometric electronic bonding that can prevent the deterioration of the polymer substrate. This paper reports a coating technique for producing a denser structure with high hardness by controlling the rf bias (ion current density). The ion current density on the substrate was controlled by the rf power and an additional bias through the rf power. [ABSTRACT FROM AUTHOR]