Alumina is a material used in many applications mainly due to its chemical inertness and wear resistance at high temperatures. Despite this, the understanding of alumina thin films is not satisfactory, as can be concluded from the diverging material properties reported in the literature. The objective of this study is to contribute towards a fundamental understanding of the correlation between synthesis conditions, thin film composition and microstructure. A detailed description of the plasma chemistry including ion charge states is essential to achieve this task. The growth technique under investigation is pulsed cathodic arc, and cathodic arc plasma under varying process conditions have been characterized.

The temporal development of the plasma chemistry has been investigated. Pulse-to­ pulse fluctuations of the plasma chemistry in the presence of magnetic fields, for an aluminium arc in an oxygen environment, were found to increase as the magnetic field strength increased. These results are explained by a varying energy input during plasma production, as seen through a measured fluctuating cathode potential.

Further investigations dealt with temporal development of the plasma chemistry and average charge state within the pulse, for a zirconium and chromium arc in a nitrogen environment. A large non-metal fraction was observed in the beginning of the plasma pulse, which can be explained by the formation and erosion of a compound layer at the cathode surface. As the pressure increased, the concentration of these ions was found to increase, both in amplitude as well as in width out in the pulse. The average charge state also showed a time and pressure dependence, the former most pronounced at lower pressures with higher charge state in the beginning of the pulse. With increasing pressure, the charge state decreased towards a steady state value, which is proposed to be due to a higher probability of collisions in the plasma with possible charge exchanges.