The Effect of Secondary Electron Emissions and Bias Voltage on Electron Heating in RF Hollow Cathode Capacitive Discharges

The change in electron heating by the secondary electron (SE) emission and the DC bias on the RF hollow cathode (HC) capacitive discharge was investigated using a 2D PIC simulation. Without SE emissions, a positive DC bias enhances the plasma density more than a negative DC bias because the electron heating near the ground electrode is dominant. However, with an asymmetric SE only from the HC, the ion-induced SE emission from the HC is the most prevalent source for electron heating. Thus, the ionization collision rate increases near the HC electrode where the SE emission occurs and forms a narrow plasma sheath. The plasma can penetrate more quickly into the hole, and the ionization collision rate also increases in the hole. With a positive bias voltage and the SE emission from the HC, the SE causes the plasma to penetrate more into the hole, resulting in an overall increase in plasma density. With a negative bias and a SE emission, differently from the no SE emission case, the plasma density inside the HC dramatically increases. Therefore, the HC effect is dominant with the ion-induced SE emission.