Electrical and Optical Characteristics of Wide Pressure-Range Capacitive Coupled RF Discharge

A homemade RF capacitive coupled discharge system operating in wide range of pressures (from low pressure up to atmospheric pressure) was constructed. Electrical and optical characteristics of the constructed system were measured for argon discharge operated at wide range of pressure (from low pressure up to atmospheric pressure) and RF power up to 150 Watt. The discharge was operated using two bare metallic copper electrodes with separation distance of 5 mm and it was kept constant in all discharge conditions. Discharge current and discharge voltage were measured for various power and argon gas pressure conditions. The electrical characteristics of the discharge revealed that the discharge is operated in glow mode for all the discharge conditions of the current work. Asymmetric effect was not observed in moderate and high-pressure conditions. Consumed power, phase angle, and plasma impedance were deduced. Optical emission spectra were acquired, and they were used to estimate electron excitation temperature (Texc) using Boltzmann plot method. Rotational (Trot) and vibrational (Tvib) temperatures were evaluated by comparing the experimental observation of nitrogen second positive system (N2[C3Πu] → N2[B3Πg]) with simulated spectra. Evaluated values of Texc, Trot and Tvib proved that the discharge of the current work is nonthermal discharge which is good candidate to deposit different materials from gas phase of discharge operated with different gases.