Igor Zhirkov

Effect of Ti-Al cathode composition on plasma generation and plasma transport in direct current vacuum arc

DC arc plasma from Ti, Al, and Ti1-xAlx (x = 0.16, 0.25, 0.50, and 0.70) compound cathodes was characterized with respect to plasma chemistry and charge-state-resolved ion energy. Scanning electron microscopy, X-ray diffraction, and Energy-dispersive X-ray spectroscopy of the deposited films and the cathode surfaces were used for exploring the correlation between cathode-, plasma-, and film composition. Experimental work was performed at a base pressure of 10−6 Torr, to exclude plasma-gas interaction. The plasma ion composition showed a reduction of Al of approximately 5 at. % compared to the cathode composition, while deposited films were in accordance with the cathode stoichiometry. This may be explained by presence of neutrals in the plasma/vapour phase. The average ion charge states (Ti = 2.2, Al = 1.65) were consistent with reference data for elemental cathodes, and approximately independent on the cathode composition. On the contrary, the width of the ion energy distributions (IEDs) were drastically...

Ion velocities in direct current arc plasma generated from compound cathodes

Arc plasma from Ti-C, Ti-Al, and Ti-Si cathodes was characterized with respect to charge-state-resolved ion energy. The evaluated peak velocities of different ion species in plasma generated from a compound cathode were found to be equal and independent on ion mass. Therefore, measured difference in kinetic energies can be inferred from the difference in ion mass, with no dependence on ion charge state. The latter is consistent with previous work. These findings can be explained by plasma quasineutrality, ion acceleration by pressure gradients, and electron-ion coupling. Increasing the C concentration in Ti-C cathodes resulted in increasing average and peak ion energies for all ion species. This effect can be explained by the “cohesive energy rule,” where material and phases of higher cohesive energy generally result in increasing energies (velocities). This is also consistent with the here obtained peak velocities around 1.37, 1.42, and 1.55 (104 m/s) for ions from Ti0.84Al0.16, Ti0.90Si0.10, and Ti0.90C...

Characterization of plasma chemistry and ion energy in cathodic arc plasma from Ti-Si cathodes of different compositions

Arc plasma from Ti-Si compound cathodes with up to 25 at. % Si was characterized in a DC arc system with respect to chemistry and charge-state-resolved ion energy. The plasma ion composition showed a lower Si content, diverging up to 12 at. % compared to the cathode composition, yet concurrently deposited films were in accordance with the cathode stoichiometry. Significant contribution to film growth from neutrals is inferred besides ions, since the contribution from macroparticles, estimated by scanning electron microscopy, cannot alone account for the compositional difference between cathode, plasma, and film. The average ion charge states for Ti and Si were higher than reference data for elemental cathodes. This result is likely related to TiSix phases of higher cohesive energies in the compound cathodes and higher effective electron temperature in plasma formation. The ion energy distributions extended up to ∼200 and ∼130 eV for Ti and Si, respectively, with corresponding average energies of ∼60 and ∼...

Generation of super-size macroparticles in a direct current vacuum arc discharge from a Mo-Cu cathode

An inherent property of cathodic arc is the generation of macroparticles, of a typical size ranging from submicrometer up to a few tens of μm. In this work, we have studied macroparticle generation from a Mo0.78Cu0.22 cathode used in a dc vacuum arc discharge, and we present evidence for super-size macroparticles of up to 0.7 mm in diameter. All analyzed particles are found to be rich in Mo (≥98 at. %). The particle generation is studied by visual observation of the cathode surface during arcing, by analysis of composition and geometrical features of the used cathode surface, and by examination of the generated macroparticles with respect to shape and composition. A mechanism for super-size macroparticle generation is suggested based on observed segregated layers of Mo and Cu identified in the topmost part of the cathode surface, likely due to the discrepancy in melting and evaporation temperatures of Mo and Cu. The results are of importance for increasing the fundamental understanding of macroparticle ge...

Experimentally established correlation between ion charge state distributions and kinetic ion energy distributions in a direct current vacuum arc discharge

DC arc plasmas from Al, Ti, Cu, Mo, and W cathodes have been characterized with respect to plasma chemistry and charge-state-resolved ion energy. The evaluated average ionization energies in the plasmas were found to be linearly correlated with the kinetic ion energies. This was further supported by evaluation of previously published data for 42 elements. A comparison of the total ion kinetic energy distribution and the corresponding ion charge state distribution, as defined by the ionization energies of the constituent ions, showed close to equivalent shapes and widths, for all cathodes analyzed. This suggests that the energy provided for ionization and acceleration varies simultaneously during plasma generation in the arc spot. The presented results provide a link between the ionization and acceleration processes, and may provide further insight into the fundamentals of cathode spot evolution and plasma generation.

Effect of N2 and Ar gas on DC arc plasma generation and film composition from Ti-Al compound cathodes

DC arc plasma from Ti, Al, and Ti1−xAlx (x = 0.16, 0.25, 0.50, and 0.70) compound cathodes has been characterized with respect to plasma chemistry (charged particles) and charge-state-resolved ion energy for Ar and N2 pressures in the range 10−6 to 3 × 10−2 Torr. Scanning electron microscopy was used for exploring the correlation between the cathode and film composition, which in turn was correlated with the plasma properties. In an Ar atmosphere, the plasma ion composition showed a reduction of Al of approximately 5 at. % compared to the cathode composition, while deposited films were in accordance with the cathode stoichiometry. Introducing N2 above ∼5 × 10−3 Torr, lead to a reduced Al content in the plasma as well as in the film, and hence a 1:1 correlation between the cathode and film composition cannot be expected in a reactive environment. This may be explained by an influence of the reactive gas on the arc mode and type of erosion of Ti and Al rich contaminations, as well as on the plasma transport...

Titanium oxide thin film deposition by pulsed arc vacuum plasma

The experimental study of effects of deposition conditions and plasma parameters on the structure of titanium oxide films is presented. The films are deposited by reactive deposition from a plasma generated by a pulsed cathodic vacuum arc source. The effects of deposition time and substrate bias voltage are studied, the films being deposited at different substrate temperatures. Bragg-Brentano X-ray diffraction and electron microscopy were used to investigate the structure of deposited films. Correlation between plasma parameters, deposition conditions and structure of synthesized films are established.

Simple filtered repetitively pulsed vacuum arc plasma source

A very simple design of cathodic filtered vacuum arc plasma source is proposed. The source without filter has only four components and none of them require precise machining. The source operates in a repetitively pulsed regime, and for laboratory experiments it can be used without water cooling. Despite the simple construction, the source provides high ion current at the filter outlet reaching 2.5% of 400 A arc current, revealing stable operation in a wide pressure range from high vacuum to oxygen pressure up to more than 10(-2) mbar. There is no need in complicated power supply system for this plasma source, only one power supply can be used to ignite the arc, to provide the current for the arc itself, to generate the magnetic field in the filter, and provide its positive electric biasing without any additional high power resistance.

Gas rarefaction effects during high power pulsed magnetron sputtering of groups IVb and VIb transition metals in Ar

The authors use energy- and time-dependent mass spectrometry to analyze the evolution of metal- and gas-ion fluxes incident at the substrate during high-power pulsed magnetron sputtering (HiPIMS) of groups IVb and VIb transition-metal (TM) targets in Ar. For all TMs, the time-and energy-integrated metal/gas-ion ratio at the substrate plane NMe+/NAr+ increases with increasing peak target current density JT,peak due to rarefaction. In addition, NMe+/NAr+ exhibits a strong dependence on metal/gas-atom mass ratio mMe/mg and varies from ∼1 for Ti ( mTi/mAr = 1.20) to ∼100 for W ( mW/mAr = 4.60), with JT,peak maintained constant at 1 A/cm2. Time-resolved ion-energy distribution functions confirm that the degree of rarefaction scales with mMe/mg: for heavier TMs, the original sputtered-atom Sigmund-Thompson energy distributions are preserved long after the HiPIMS pulse, which is in distinct contrast to lighter metals for which the energy distributions collapse into a narrow thermalized peak. Hence, precise timin...

Controlling the boron-to-titanium ratio in magnetron-sputter-deposited TiBx thin films

Magnetron sputter-deposited TiBx films grown from TiB2 targets are typically highly overstoichiometric with x ranging from 3.5 to 2.4 due to differences in Ti and B preferential ejection angles and gas-phase scattering during transport between the target and the substrate. The authors show that the use of highly magnetically unbalanced magnetron sputtering leads to selective ionization of sputter-ejected Ti atoms which are steered via an external magnetic field to the film, thus establishing control of the B/Ti ratio with the ability to obtain stoichiometric TiB2 films over a wide range in Ar sputtering pressures.