Determination of the equilibrium steady ion sheath in drifting plasma

Summary form only given, as follows. A sequence of high voltage negative pulses is applied to the sample in the PIII process. It is shown that in most applications of high voltage implantation, an equilibrium steady ion sheath can not be sustained in a partially ionized plasma such as that generated by RF discharge. In order to maintain sufficient plasma, either the applied voltage is reduced or the pulse duration is shortened. The consequence is a reduction in implantation energy or an incorporation of a larger proportion of low energy ions respectively. However, it has been predicted that an equilibrium steady ion sheath can be sustained in a drifting plasma such as that created by a Cathodic Arc In this paper, the equilibrium steady ion sheath width in the drifting plasma is determined by several methods; the analytical Child-Langmuir Law, numerical simulation by Particle-In-Cell method, and by experimental measurement using a Langmuir Probe. It is shown that the analytical Child-Langmuir Law and the numerical simulation provide consistent predictions in simple plasma consisting of one element, In the case of mixed plasma of several elements, the numerical method provides better results. We also investigate the influence of a Langmuir Probe at the sheath boundary by comparing probe measurements with the numerical results. The deviation of the measured equilibrium steady sheath width from the numerical prediction is discussed.