Alexander V. Tumarkin

A systematic experimental study of ion fluxes extracted from a DC magnetron discharge is presented for the development of ion sources for implantation applications. A planar circular magnetron with a closed anode configuration was operated with aluminum and boron targets in Ar and Ar/N₂ gas mixtures. Ion composition, discharge characteristics, and current densities were measured as functions of gas flow, discharge power, and nitrogen admixture.Stable generation of Al⁺, Ar⁺, N⁺, and B⁺ ion fluxes was demonstrated. In argon discharge with an aluminum target, Al⁺ current densities up to ~3 mA/cm² were achieved. The ion composition is shown to be strongly influenced by charge-exchange processes during transport. The addition of nitrogen enabled efficient generation of N⁺ ions with fractions exceeding 50% while maintaining stable discharge at limited N₂/Ar ratios. For boron targets, B⁺ ion generation was achieved with current densities up to ~0.5 mA/cm².The closed anode configuration significantly enhances ion flux compared to conventional geometries due to improved plasma confinement. The results indicate that magnetron-based ion sources provide a simple, stable, and versatile approach for generating metal and gaseous ion beams without toxic precursors, making them promising for ion implantation systems.

Direct current (DC) reactive magnetron discharge in Ar + O₂ mixtures with an aluminum (Al) target was investigated. Electrical measurements of the discharge voltage and current along with the deposition rate trends observed with varying the oxygen flow rate indicated the presence of hysteresis, typical to when using a DC power supply. The transition between metallic and oxide (compound) modes was analyzed in more detail by measuring the mass-resolved fluxes of positively and negatively charged ions together with the optical emission spectra of plasma. The dependence of constituent ion fluxes (Ar⁺, Ar²⁺, Al⁺, O⁺, O₂⁺, O⁻, and O₂⁻) on the reactive oxygen gas flow rate was revealed, indicating the transition (in 1.2–1.8 sccm O₂ flow range) from a metallic regime to a poisoned regime. The optical diagnostics indicated a nonlinear hysteresis loop pattern of dependence for various constituents (ions and neutrals) of the magnetron discharge plasma. The comparison between the particle and optical measurements, though exhibiting a pronounced correlation, demonstrated individual features of both methods, which need to be taken into account when interpreting the results. The hysteresis patterns were further discussed by comparing the experimental data with the calculation results from the Berg model. An approach of adapting the model results to the case of a power-regulated magnetron power supply is expressed.

Tungsten fuzz layers formed on the plasma-facing material surfaces of thermonuclear facilities due to helium ion irradiation are known to promote the initiation of electrical discharges on the first wall. Previous studies have indicated increased arcing probability under helium ion irradiation in steady plasmas with increasing ion energy to several hundred eV. Here, we experimentally consider the growth of nanostructures on tungsten surfaces in an RF He plasma and the spontaneous initiation of arcs when applying the pulsed bias voltage to the sample, up to several keV. The arc current and voltage waveforms were obtained, and the scanning electron images of the arc traces were analyzed. The behavior of the arc at the smooth/fuzzy surface boundary directly demonstrated the beneficial arcing conditions of the nanostructured layer. The proposed approach of pulsed biasing enables controlling the amount and duration of arcs for better analysis of their dimensions and dynamics. From the experimental results, the total arc trace length and arc velocity were calculated and compared with literature data, giving a good agreement both between experiments and theoretical data and between experiments in different arc initiation conditions.

We report the implementation of a method for non-destructive remote diagnostics of the content of gas impurities retained in a material surface layer. The technique is based on the laser-induced heating of a surface layer and associated desorption of gas species in the presence of background inductively coupled plasma (ICP). The analysis of released gas species is made by optical emission spectroscopy (OES). The procedure of optimizing the signal efficiency by changing the spectrometer observation path with respect to the laser beam and the delay of spectrum acquisition is discussed. The applicability of laser-induced desorption spectroscopy (LIDS) was examined by studying the release of hydrogen from a Ti-V test sample exposed to Nd:glass laser pulses (λ = 1064 nm, duration 0.5 ms, energy 1–14 J), in a background argon plasma, by measuring the intensity of Balmer spectral lines. The demonstrated dependence of H_α intensity on the laser pulse energy enables implementing the LIDS technique for diagnostics of retained hydrogen. The lower limit of the laser pulse energy range suitable for diagnostics is associated with spectrometer sensitivity. The higher limit is governed by distortion of plasma conditions, which is detected as a deviation in argon emission intensity from constant value when the laser pulse energy exceeds 6 J.

This paper aims to investigate the quality of thin alumina films deposited on glass samples using magnetron sputtering in the reactive modulated pulsed power mode (MPPMS) and evaluate the process productivity. The aluminum target was sputtered in Ar/O₂ gas mixtures with different fractions of oxygen in the total gas flow, in the fixed pulsed voltage mode. The pulse-on duration was varied between 5 and 10 ms, while the pulse-off time was 100 or 200 ms. The dependences of mass deposition rate and discharge current on the oxygen flow were measured, and the specific deposition rate values were calculated. Prepared coatings had a thicknesses of 100–400 nm. Their quality was assessed by scratch testing and by measuring density, refractory index, and extinction coefficient for different power management strategies. The strong influence of pulse parameters on the coating properties was observed, resulting in a maximum density of 3.6 g/cm³ and a refractive index of 1.68 for deposition modes with higher duty cycle values. Therefore, adjusting the pulse-on and pulse-off periods in MPPMS can be used not only to optimize the deposition rate but also as a tool to tune the optical characteristics of the films. The performance of the studied deposition method was evaluated by comparing the specific growth rates of alumina coatings with the relevant data for other magnetron discharge modes. In MPPMS, a specific deposition rate of 200 nm/min/kW was obtained for highly transparent Al₂O₃, without using any dedicated feedback loop system for oxygen pressure stabilization, which makes MPPMS superior to short-pulse high-power impulse magnetron sputtering (HiPIMS) modes.