Optical characterization of glow and afterglow regions of Ar/O₂ microwave plasma: effect of applied power and gas flow

In this work, the effect of microwave power and gas flow on formation of atomic oxygen (O) was investigated by actinometry method in the two different regions of Ar/O₂ microwave plasma: the glow and afterglow regions. The experiments were performed keeping constant the Ar/O₂ gas flow ratio at proportion of 3/2 and varying the microwave power from 200 to 1100 W and the total gas flow from 50 to 300 sccm. The results showed that the production of O depends on both discharge parameters investigated and that the microwave power has the greater influence in the production of O. At afterglow region the production of O tends to be uniform and not dependent on the gas flow and microwave power. This may be due to homogenization of the processes of recombination and loss in the gas phase and to the walls along the afterglow region.