Spatiotemporal analysis of the double layer formation in hydrogen radio frequency discharges

RF discharges at 13.56 MHz in pure H\+v\2\-v\ and CH\+v\4\-v\-SiH\+v\4\-v\ mixtures highly diluted in H\+v\2\-v\ were investigated by spatially and spatiotemporally resolved emission spectroscopy. Spatial emission profiles of the excited species exhibit double layers near the electrodes. Spatiotemporal analyses show that the emitting layers occur at different times in the RF cycle. The mechanisms involved in the double layer formation are interpreted by simplified numerical models based on both a fluid model and a particle-in-cell-Monte Carlo model. The results of the models are in good agreement with the experiment. Formation of the double layers is analysed as resulting from the high drift velocity of the hydrogen ions. (Original abstract-amended)