Capacitive discharge mode transition in moderate and atmospheric pressure

Current-voltage characteristics of α- and γ-modes were investigated in moderate and atmospheric pressure capacitive discharges. The α- and γ-modes, the co-existence of both modes, and the α- to γ- and γ- to α-mode transitions were observed with the changes in voltage, current, and plasma volume. Changing of gas pressure, (100-760) Torr, the α to γ and the γ to α transition occurred with respect to input power increasing and decreasing, respectively. The hysteresis in current and voltage curve was observed and became more evident at higher pressure. Using a simple electrical circuit model, the relation between the gas pressure and the α-sheath thickness before mode transition was described.