A one-dimensional self-consistent particle in cell/Monte Carlo method is used to study the local (at the laser impact region) and fast relaxation phenomena after laser-induced photodetachment in a strongly electronegative ${\mathrm{SiH}}_4/{\mathrm{H}}_2$ rf discharge. The relaxation process of the local densities of the charged plasma species has been studied in association with the time evolution of the local electric field. The phenomena predicted theoretically about the relaxation processes, such as the potential well, the electrostatic oscillation, the long lasting potential structure, the distortion of the early potential perturbation on the measurement of negative ion temperature, and the depression in the positive ion density profile at the edges of the laser impact region, have been confirmed by our simulation results. Compared to the relaxation in weakly electronegative discharges, the local and even the global electric field in strongly electronegative discharges, has been weakened strongly after photodetachment. The relaxation of the local electric field lasts 100 rf cycles with the recovery of the local electron density and the local electron energy. The electrostatic oscillation exhibited as the deviation in quasineutrality, is very strong and continues over several rf cycles in our case. The large dip in the center of the positive ion density profile, observed in the experiment, is also reproduced by our model.

• Received 12 April 2001

DOI:https://doi.org/10.1103/PhysRevE.65.016408