An apparatus and method for the creation of negative ion beams is disclosed. The apparatus includes an RF ion source, having an extraction aperture. An antenna disposed proximate a dielectric window is energized by a pulsed RF power supply. While the RF power supply is actuated, a plasma containing primarily positive ions and electrons is created. When the RF power supply is deactivated, the plasma transforms into an ion-ion plasma. Negative ions may be extracted from the RF ion source while the RF power supply is deactivated. These negative ions, in the form of a negative ribbon ion beam, may be directed toward a workpiece at a specific incident angle. Further, both a positive ion beam and a negative ion beam may be extracted from the same ion source by pulsing the bias power supply multiple times each period.