Variations in Plasma Parameters in the Plume of a DC Plasma Source Near a Substrate.

A three-electrode dc plasma source was constructed and operated in Ar at pressures of 2 -- 10 torr. The plasma source consists of two cylindrical electrodes with dimensions in the mm range and 1 mm inter-electrode distance, and a third, biased electrode/substrate, positioned in front of the cathode or in front of the anode opening. Optical and electrical measurements show that plasma at the substrate has a higher temperature (12 -- 14 eV) on the anode side than on the cathode side (4 -- 7 eV). The biased electrode offers flexibility in controlling plasma-surface interactions by extracting electrons of various energies from the discharge. This electrode exploits the non-local electron kinetics to control plasma properties in the plume from the discharge near the surface of the electrode/substrate.