Effect of driving frequency on electron heating in capacitively coupled RF argon glow discharges at low pressure

A one-dimensional (1D) fluid model on capacitively coupled radio frequency (RF) argon glow discharge between parallel-plates electrodes at low pressure is established to test the effect of the driving frequency on electron heating. The model is solved numerically by a finite difference method. The numerical results show that the discharge process may be divided into three stages: the growing rapidly stage, the growing slowly stage, and the steady stage. In the steady stage, the maximal electron density increases as the driving frequency increases. The results show that the discharge region has three parts: the powered electrode sheath region, the bulk plasma region and the grounded electrode sheath region. In the growing rapidly stage (at 18 mu s), the results of the cycle-averaged electric field, electron temperature, electron density, and electric potentials for the driving frequencies of 3.39, 6.78, 13.56, and 27.12 MHz are compared, respectively. Furthermore, the results of cycle-averaged electron pressure cooling, electron ohmic heating, electron heating, and electron energy loss for the driving frequencies of 3.39, 6.78, 13.56, and 27.12 MHz are discussed, respectively. It is also found that the effect of the cycle-averaged electron pressure cooling on the electrons is to "cool" the electrons; the effect of the electron ohmic heating on the electrons is always to "heat" the electrons; the effect of the cycle-averaged electron ohmic heating on the electrons is stronger than the effect of the cycle-averaged electron pressure cooling on the electrons in the discharge region except in the regions near the electrodes. Therefore, the effect of the cycle-averaged electron heating on the electrons is to "heat" the electrons in the discharge region except in the regions near the electrodes. However, in the regions near the electrodes, the effect of the cycle-averaged electron heating on the electron is to "cool" the electrons. Finally, the space distributions of the electron pressure cooling the electron ohmic heating and the electron heating at 1/4T, 2/4T, 3/4T, and 4/4T in one RF-cycle are presented and compared.