Electric Probe Measurements in Pulsed Magnetron Plasmas

Abstract

The temporal and spatial evolution of the plasma potential V_p in a pulsed magnetron discharge was determined using time resolved emissive probing techniques. Spatial maps of V_p in plasma were constructed and, at all positions, V_p followed the large changes in the cathode voltage V_d. Downstream, the potential always remained at least several volts above the most positive surface in the discharge. In the driven ‘on’ phase, the results showed an axial electric field generated in the bulk, with a potential drop ΔV_p of ∼30 V over a distance of 4 cm from plasma to sheath edge, consistent with that observed in the dc magnetron. During the stable ‘reverse’ period of the discharge, the electric fields in the bulk were found to collapse. The temporal evolution of V_p confirms a simple picture of the behaviour of the pulsed magnetron, predicted from previous mass spectroscopic measurements of high energy ions in the plasma. Some implications of these results for the pulsed deposition process are suggested. SE/515