HIGH-ENERGY NEGATIVE-IONS IN A RADIOFREQUENCY DISCHARGE

We measured energy distributions of negative ions at the grounded elec trode of an oxygen parallel-plate rf discharge. Negative ions are gene rated in the plasma sheath in front of the rf electrode, are accelerat ed away from the driven electrode, and can be detected at the grounded electrode. The maximum energy of the negative ions corresponds to the negative self-bias voltage of the rf electrode. Structures in the ene rgy distribution reflect sheath properties and characteristics of the ion generation processes. (C) 1996 American Institute of Physics.