A one-dimensional Monte Carlo collision‐particle-in-cell plasma computer code was used to simulate plasma immersion ion implantation by applying a negative voltage pulse to the substrate while the reactor wall is grounded. The results presented here show the effect of short rise time pulses: for rise times shorter than the electron plasma period stypically 5 ns/ kVd, an electron shock wave is observed where a rapidly expanding sheath heats the electrons up to high energies. Many of these fast electrons are expelled from the plasma leading to a high plasma potential and thus to a high surface electric field on the earthed electrode which could give rise to non-negligible electron field emission. © 2005 American Institute of Physics . fDOI: 10.1063/1.1872894g