Sheath Reversal During Transient Radio-Frequency Bias

Optical imaging is performed with temporal and spatial resolution in a capacitively coupled plasma. The region imaged is in front of an RF biased planar probe embedded in the center of the ground electrode of a standard Gaseous Electronics Conference (GEC) reference cell. Two main periods of interest stand out. The local sheath induced by the biasing and the main plasma bulk are affected. The first interesting period is at the onset of the RF burst on the planar probe. The voltage applied to the surface can locally reverse the sheath in front of this surface. A second interesting period is after the build up of self bias and before the extinction of the RF burst. During the steady self-bias phase, the local perturbation of optical emission amounts to less than 10%, whereas in the sheath reversal phase it reaches 70%.