| AVS 63rd International Symposium & Exhibition | |
| Plasma Science and Technology | Thursday Sessions |
| Session PS1-ThM |
| Session: | Modeling of Plasmas and Plasma-Surface Interactions |
| Presenter: | Jon Gudmundsson, University of Iceland |
| Authors: | J.T. Gudmundsson, University of Iceland H. Hannesdottir, University of Iceland |
| Correspondent: | Click to Email |
We explore the effects of including the singlet metastable molecules O2(a1Δg) and O2(b1Δg+) in the discharge model of a capacitively coupled rf driven oxygen discharge. We furthermore examine the addition of energy-dependent secondary electron emission yields from the electrodes to the discharge model. The one-dimensional object-oriented particle-in-cell Monte Carlo collision code oopd1 is used for this purpose [1], with the oxygen discharge model considering the species O2(X3Σg-), O2(a1Δg), O2(b1Σg+), O(3P), O(1D), O2+, O+, O-, and electrons. The effects on particle density profiles, the electron heating rate profile, the electron energy probability function and the sheath width are explored including and excluding the metastable oxygen molecules and secondary electron emission. We have demonstrated that adding the metastable O2(a1Δg) to the discharge model changes the electron heating from having contributions from both bulk and sheath heating to being dominated by sheath heating for pressures above 50 mTorr [2,3]. However, at a low pressure (10 mTorr), Ohmic heating in the bulk plasma (the electronegative core) dominates, and detachment by O2(a1Δg), has only a small influence on the heating process. Thus at low pressure, the electron energy probability function (EEPF) is convex and as the pressure is increased the number of low energy electrons increases and the number of higher energy electrons (>10 eV) decreases, and the EEPF develops a concave shape or becomes bi-Maxwellian [3]. We find that including the metastable O2(b1Σg+) further decreases the Ohmic heating and the effective electron temperature in the bulk region. The effective electron temperature in the electronegative core is found to be less than 1 eV in the pressure range 50 - 200 mTorr which agrees with recent experimental findings. Furthermore, we find that including an energy-dependent secondary electron emission yield for O2+-ions has a significant influence on the discharge properties, including decreased sheath width.
[1] J. T. Gudmundsson, E. Kawamura and M. A. Lieberman, Plasma Sources Sci. Technol., 22(3) (2013) 035011
[2] J. T. Gudmundsson and M. A. Lieberman, Plasma Sources Sci. Technol., 24(3) (2015) 035016
[3] J. T. Gudmundsson and B. Ventéjou, J. Appl. Phys., 118(15) (2015) 153302