title: Strong ionization asymmetry in a geometrically symmetric radio frequency capacitively coupled plasma induced by sawtooth voltage waveforms.
abstract: The ionization dynamics in geometrically symmetric parallel plate capacitively coupled plasmas driven by radio frequency tailored voltage waveforms is investigated using phase resolved optical emission spectroscopy (PROES) and particle-in-cell (PIC) simulations. Temporally asymmetric waveforms induce spatial asymmetries and offer control of the spatiotemporal dynamics of electron heating and associated ionization structures. Sawtooth waveforms with different rise and fall rates are employed using truncated Fourier series approximations of an ideal sawtooth. Experimental PROES results obtained in argon plasmas are compared with PIC simulations, showing excellent agreement. With waveforms comprising a fast voltage drop followed by a slower rise, the faster sheath expansion in front of the powered electrode causes strongly enhanced ionization in this region. The complementary waveform causes an analogous effect in front of the grounded electrode.
authors: LPICM-CNRS, Ecole Polytechnique, route de Saclay, 91120 Palaiseau, France.
authors: Bastien
authors: B
authors: Bruneau
authors: York Plasma Institute, Department of Physics, University of York, Heslington, YO10 5DD York, United Kingdom.
authors: Timo
authors: T
authors: Gans
authors: York Plasma Institute, Department of Physics, University of York, Heslington, YO10 5DD York, United Kingdom.
authors: Deborah
authors: D
authors: O'Connell
authors: York Plasma Institute, Department of Physics, University of York, Heslington, YO10 5DD York, United Kingdom.
authors: Arthur
authors: A
authors: Greb
authors: LPICM-CNRS, Ecole Polytechnique, route de Saclay, 91120 Palaiseau, France.
authors: Erik V
authors: EV
authors: Johnson
authors: LPP-CNRS, Ecole Polytechnique, route de Saclay, 91120 Palaiseau, France.
authors: Jean-Paul
authors: JP
authors: Booth