A dc glow discharge source with controlled plasma potential was developed for application in plasma immersion ion implantation processing of materials surfaces. This type of ion implantation system allows cost effective surface modification of workpieces with complex shapes. The effects of the nitrogen plasma etching during the plasma immersion ion implantation process was studied using Si wafers as monitors, as we varied the externally controlled plasma potential between 0 and 350 V. When the plasma potential is controlled below 70 V, the ion implantation is dominant, otherwise the etching overtakes. The nitrogen implanted silicon wafers were analyzed by high resolution x-ray diffraction and Auger electron spectroscopy which revealed successful implantation of ions with accumulated nitrogen dose of ${\text{1.5×10}}^{17} {\mathrm{cm}}^{\text{−2}},$ for the low potential case.