Energy-resolved mass spectroscopy of Ar–C2H2–N2 plasma, performed during ion plating of TiC and TiN hard coatings

Energy-resolved mass spectroscopy studies during discharge in Ar+N2 and Ar+C2H2 gas mixtures in a triode ion-plating apparatus (Balzers BAI 730) revealed a high degree of acetylene (C2H2) decomposition under typical conditions suitable for titanium evaporation. In the case of the Ar+C2H2 gas mixture, the most abundant neutral species besides argon is hydrogen, and not acetylene as would be expected. On the other hand, the 12C+ ion is the most abundant carbon-containing species. The ratio between C+, CH3+ and C2H2+ ions and titanium ions (Ti+, T2+) decreases with increasing arc current. By careful adjustment of the discharge parameters, either a plasma rich in CxHy radicals with a low metal evaporation rate or plasma with a high evaporation rate but with almost completely decomposed acetylene, i.e. with C+ and Hn=1–3+ only, can be obtained.