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

• Published in: Surface & coatings technology Vol. 272; no. C; pp. 309 - 321
• Main Authors: Franz, Robert, Polcik, Peter, Anders, André
• Format: Journal Article
• Language: English
• Published: Switzerland Elsevier B.V 25.06.2015; Elsevier; Elsevier Sequoia
• Subjects: AlCr; Aluminium; Aluminum; Atmospheres; Background gas; Cathodes; Cathodic arc; Chromium; CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; Coatings; Composite cathode; Energy distribution; Ion energy distribution function; MATERIALS SCIENCE; Spots; Cathodic arc; Background gas; Ion energy distribution function; AlCr; Composite cathode
• ISSN: 0257-8972; 1879-3347
• DOI: 10.1016/j.surfcoat.2015.03.047

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 3.5Pa 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. •A comprehensive overview of ion energies in arc plasmas from AlCr composite cathodes is provided.•Multiply charged aluminium and chromium ions were observed.•High-energy tails were found in the distributions of aluminium and chromium as well as atomic nitrogen and oxygen ions.•The fraction of thermalised ions increased with increasing background gas pressure.•Negatively charged oxygen ions have energies typically up to 50eV.