Effect of O2(a1Δg) on plasma structures in oxygen radio frequency discharges

Oxygen rf glow discharges between parallel plates were numerically analyzed by using the relaxation continuum model. The result at a frequency of 13.56 MHz, sustaining voltage of 150–350 sin ωt V, pressure of 0.15–1.0 Torr, and stainless steel surface, shows that O2(a1Δg) has a number density that is an order of magnitude larger than that of atomic oxygen. The plasma density as a function of pressure has a maximum at about 0.2 Torr, and decreases with increasing pressure due to the increase in the net rate of associative detachment from O− by O2(a1Δg). The comparison between the discharges in two surface materials, stainless steel and copper, indicates that the number densities of O2(a1Δg) and atomic oxygen strongly depend on the surface loss probability, and that consequently the plasma density is also changed by replacing the surface material.