Spatially resolved ground state atomic oxygen density during the mode transition of inductively coupled oxygen plasmas

The ground state atomic oxygen density (nag) and its distribution were systematically studied by two-photon absorption laser induced fluorescence (TALIF) during the discharge mode transition in inductively coupled oxygen plasmas (ICP). After distinguishing discharge mode by experiments, absolute value of n(Og) under different heating powers/gas pressures were measured. Increasing the heating power in discharges with a total gas pressure of 10, 60 and 80 Pa leads to E -> H transition at 0.5, 1.1 and 1.3 kW, respectively. When pressure increased in 10-80 Pa, 0.1 and 2 kW plasmas maintained in E and H mode respectively, and 1 kW plasmas experienced H -> E transition at 60 Pa n(Og) in H-modes were one order of magnitude larger than E-mode. The power-pressure composed mode transition boundaries were obtained through measuring n(Og). Spatial distribution of n(Og) showed that spatial difference of H-mode was more obvious than E-mode. By 0.1 mm spatial resolution TALIF measurement, density gradients of rear 5 mm region in H-mode are one order of magnitude larger than E-mode. These results provide references for processing parameter selection. High spatial resolution TALIF measurement will contribute key technology for acquiring important parameters of surface reactions.