Spectroscopic study and modelling of a reactive magnetron discharge in Ar/O-2 and in air

The Optical Emission Spectroscopy technique was used to monitor a magnetron discharge working in an Ar/O-2 mixture and in air. Hysteresis effects and instability, which are frequently observed when working with reactive gases , were clearly seen in the optical spectra. When the discharge power was in creased, the atomic oxygen line intensity increased, saturated and then dis appeared whilst, at the transition, sputtered material line intensities sud denly increased. In air, nitrogen lines were found to be less sensitive to this transition. The transition between the two regimes of the discharge is due to a change in the composition of surfaces from oxidised to metallic, as confirmed by the analysis of deposited films. In parallel with the exper iment, a plasma model was developed for the magnetised region of the discha rge which predicts the variations of the various plasma species in the Ar/O -2 mixture. This model explains the behaviour of line intensities on the tw o sides of the transition. (C) 1998 Elsevier Science Ltd. All rights reserv ed.