INFLUENCE OF GAS-PRESSURE AND CATHODE COMPOSITION ON ION ENERGY-DISTRIBUTIONS IN FILTERED CATHODIC VACUUM ARCS

We report measurements of ion energy distributions of ionized species in titanium and aluminium filtered cathodic vacuum arcs operating in o xygen and nitrogen gas atmospheres. The ion energy distributions were recorded using a Hiden mass selected ion energy analyzer. The results show that a significant reduction in ion energies and a change in the shape of ion energy distributions occurs as the gas pressure is increa sed, The degree of the energy reduction depends on both the type of ga s and the metal ions making up the are plasma. This has important impl ications for the deposition of thin films, such as titanium nitride, c ommonly produced using vacuum arcs in reactive gas atmospheres. The io n energy distributions of the cathode ion species in the absence of ba ckground gas and at low gas pressures are well fitted by shifted Maxwe llian distributions. As the gas pressure rises the distributions consi st of a progressively increasing thermalized Maxwellian component and a decreasing shifted Maxwellian. An investigation of energy distributi ons of species in arcs triggered on alloyed cathodes showed that the r elative abundance of ions of different charge states and their energy distributions varied as alloy metals were introduced. This indicates t hat the electron temperature in the cathode spot and hence the cathode spot dynamics is affected by the presence of the alloy metal, (C) 199 8 American Institute of Physics.