On the energy balance of substrate surfaces during plasma cleaning of lubricants

During dc oxygen plasma cleaning of hydocarbon-containing light lubricants deposited on aluminum the energy fluxes towards the substrates have been determined by temperature measurements. The contributions to the total energy influx are due to exothermic combustion reactions of the petroleum-like lubricants by the plasma generated oxygen atoms and due to kinetic ion energy transfer. By variation of the discharge mode and substrate voltage the effect of the two contributions could be separated. In the anomalous glow discharge mode, where the ion energy influx was of importance, the treated substrates were at cathode potential (- 500 to - 1200 V) and vice versa, in the hollow cathode discharge mode the substrates were at floating potential where only the chemical component contributes to substrate heating. A comparison of the measurements with calculations based on simple model assumptions is given.