Element- and charge-state-resolved ion energies in the cathodic arc plasma from composite AlCr cathodes in argon, nitrogen and oxygen atmospheres

Abstract

The energy distribution functions of ions in the cathodic arc plasma using composite AlCr cathodes were measured as a function of the background gas pressure in the range 0.5 to 3.5 Pa for different cathode compositions and gas atmospheres. The most abundant aluminium ions were Al+ regardless of the background gas species, whereas Cr2+ ions were dominating in Ar and N2 and Cr+ in O2 atmospheres. The energy distributions of the aluminium and chromium ions typically consisted of a high-energy fraction due to acceleration in the expanding plasma plume from the cathode spot and thermalised ions that were subjected to collisions in the plasma cloud. The fraction of the latter increased with increasing background gas pressure. Atomic nitrogen and oxygen ions showed similar energy distributions as the aluminium and chromium ions, whereas the argon and molecular nitrogen and oxygen ions were formed at greater distance from the cathode spot and thus less subject to accelerating gradients. In addition to the positively charged metal and gas ions, negatively charged oxygen and oxygen-containing ions were observed in O2 atmosphere. The obtained results are intended to provide a comprehensive overview of the ion energies and charge states in the arc plasma of AlCr composite cathodes in different gas atmospheres as such plasmas are frequently used to deposit thin films and coatings.

Erosion behavior of composite Al-Cr cathodes in cathodic arc plasmas in inert and reactive atmospheres

“…7 there are modified layers noticeable similar to the ones observed on the cathodes exposed to Ar atmosphere. Prior to the O 2 pressure reported in the present work, the cathodes were operated at lower O 2 pressures as reported in [16]. Most likely, the oxide layer formed at lower O 2 pressures was not stable enough to prevent the ignition of cathode spots completely and, therefore, a modified layer with intermixed Al and Cr was formed.…”

“…As described in ref. [16], the gas pressure during the experiments was varied between 0.5 and 3.5 Pa. The pressure applied before removing the individual cathodes from the source was 0.5 Pa in the case of Ar used as background gas and 3 Pa in the case of the reactive gases N Subsequent to the exposure to the arc plasma, crosssections of the cathodes were prepared by grinding and polishing to a finish of 1 µm.…”

“…Most of the studies measured the ion charge states or ion energies in vacuum conditions. The influence of an inert or reactive background gas on the cathodic arc plasma from Ti-Al [14] and Al-Cr cathodes [15,16] has been evaluated by measuring the ion charge states and energies as a function of the background gas pressure.…”

Time-resolved ion energy and charge state distributions in pulsed cathodic arc plasmas of Nb−Al cathodes in high vacuum

“…For multi-element cathodes, the available literature does not specifically take into account time dependencies and their consequences to ion properties, e.g. in [9,[15][16][17][18][19][20].…”

The Effect of Cathodic Arc Guiding Magnetic Field on the Growth of (Ti0.36Al0.64)N Coatings

“…Electron-impact ionization is the predominant source of gas phase ionization [57], and N 2 ionization is known to occur at a significant distance from the cathode [58]. In Mode II, the loss of electrons to the annular anode causes a reduction in the probability of electron-impact ionization events.…”