Effect of neutral gas temperature on low-pressure RF argon discharges: A fluid simulation

Based on plasma fluid theory, using the drift-diffusion approximation, a one-dimensional fluid model is established for the plasmas in low-pressure RF argon discharge between parallel-plate electrodes. The model is numerically solved using a finite difference method to obtain its self-consistent results. The effect of neutral gas temperature from 300 to 600 K on the plasma characteristics is analyzed and discussed. The results show that the dynamic evolutions of the sheaths exhibit a significant periodic correlation with the electron heating. As the neutral gas temperature increases, the widths of both the sheaths increase, the electric field strengths of both the sheaths decrease, and the electron heating is reduced. The cycle-averaged electron heating has one peak near the powered sheath and another peak near the grounded sheath, and the two peaks show a distinct asymmetry. With increasing neutral gas temperature, both peaks shift toward the plasma bulk, the two peaks decrease gradually, and the asymmetry also weakens. The cycle-averaged electron heating takes negative values adjacent to the electrodes, and the magnitude of these negative values decreases with increasing neutral gas temperature. The ionization rate also decreases gradually as the neutral gas temperature increases. It is found that the peak asymmetry of the cycle-averaged electron heating and its negative values adjacent to the electrodes are both dominated by the electron pressure gradient electric field.