Measured radial dependence of the peak sheath voltages present in very high frequency capacitive discharges

The radial distribution of the measured voltage drop across a sheath formed between a 300mm electrode and an argon plasma discharge is shown to depend on the excitation radio frequency, under constant power and pressure conditions. At a lower frequency of 13.56MHz, the voltage drop across the sheath is uniform across the 300mm electrode, while at higher frequencies of 60 and 162MHz the voltage drop becomes radially nonuniform. The magnitude and spatial extent of the nonuniformity become greater with increasing frequency.

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