Characteristics of a pin-to-plate dielectric barrier discharge in helium

In this study, the characteristics of a modified dielectric barrier discharge (DBD) (that is, a pin-to-plate DBD) in He have been studied as a function of the applied AC voltage, the air gap between the electrodes, and the pin density of the powered electrode. The pin-to-plate DBD showed typical current-voltage characteristics similar to those of a corona discharge. The optimum air gap between the electrodes at a given applied voltage was 4 mm, for which the consumed power was a maximum. When the air gap was larger than 4 mm, the discharge changed from a glow discharge to a filamentary discharge. An increase in the pin density from 4 to 16 pins/cm ² also increased the consumed power at a given voltage and at a fixed air gap. When the optical emission intensities from He metastable and oxygen atoms from the feed He gas and from the residual air, respectively were investigated by using an optical emission spectrometer, the highest optical emission intensities from He metastable and oxygen atoms was obtained for a pin density of 16 pins/cm ² at a given voltage and a fixed air gap. The photoresist ashing rate using the residual oxygen in He was also the highest when the pin density was 16 pins/cm ² and when the air gap was 4 mm, possibly because the dissociated oxygen atomic density in the plasma and the power consumption were highest.