Observation of sheath characteristics on a sample undergoing plasma ion implantation

The authors recently added a microwave isolator and a new tuner to the UTK Microwave Plasma Facility (MPF), an approximately 200 liter steady-state, uniform plasma generated by 2 kW of 2.45 GHz microwave power. Plasma ion implantation is accomplished by pulsed biasing of the sample to negative potentials greater than 15 kV, which accelerates ions and implants them to depths which provide beneficial effects for wear and corrosion resistance. Obtaining the best results from plasma ion implantation (PII) requires that the sheath between the plasma and sample be smaller than the characteristic radius of curvature of the sample surface. They have investigated the visual appearance of the sheath observed in the MPF plasma as well as the electron number density and kinetic temperature of the ambient plasma. Also studied were the effects of longer periods between implantation pulses for PII, and the effect of varying the operating gas pressure. They will present data on the plasma parameters and observed characteristics of the sheath during PII. They also expect to report the functional dependence of the sheath thickness on plasma parameters. Investigations will carried out to determine the sheath thickness and the incident ion fluxes on the sample undergoing plasma ion implantation, and these data will be compared to the predictions of various sheath theories