In this work we present measurements of the plasma potential of a moving ionization zone in a direct current magnetron sputtering. Measurements were recorded in a space and time resolved manner using movable emissive and floating probes. This allowed us to make a three-dimensional representation of the plasma potential and derive the related electric field, space charge and electron heating distributions. The data reveal the existence of strong electric fields parallel and perpendicular to the target surface. The largest E-fields result from a double layer structure at the leading edge of the ionization zone. Measurements imply that the double layer plays a crucial role in the energization of electrons since electrons can gain several tens of electronvolts from azimuthal E-field. As electrons drift over the magnetron there is a sustained coupling between the potential structure, electron heating, and ionization processes. The ionization zone moves in the –E×B direction from which the to-be-heated electrons arrive and into which the heating region expands. The motion of the zone is dictated by the force of the local electric field on the ions at the leading edge of the ionization zone. We postulate that electron heating caused by the potential jump and physical processes associated with the double layer also apply to high power impulse magnetron sputtering.
COBISS.SI-ID: 30248743