The discharge characteristics of low-pressure capacitively coupled argon plasma with Langmuir probe

Abstract

The discharge characteristics and electronic behavior in the low pressure capacitively coupled argon plasma is studied by the radio frequency (RF) compensated Langmuir probe based on the Druyvesteyn method. The effects of excitation frequencies (15, 50, 81.36, 100 MHz) and power (10∼80 W) at electrode on the electron energy probability function (EEPF), electron density (ne), electron temperature (Te) and plasma potential (Vp) are discussed. The experimental results indicate as the frequency increases, the EEPF evolves from a single Maxwellian distribution to a convex distribution and finally turns into a Druyvesteyn distribution. Simultaneously, the EEPF curve shows an upward trend with power increase and the low-energy electron group temperature and the high-energy electron group temperature of 81.36 MHz both are highest. The low-energy electron group temperature of 50 MHz is lowest. The electron density first decreases and then increases rapidly as the excitation frequency increases, whereas increases with power increasing. The electron temperature decrease with frequencies increase (after 50 MHz). When the frequency is 15 and 50 MHz, the effective electron temperature drops with the increase of power, and when the frequency is 81.36 and 100 MHz, it rises with the increase of power, which reflects the discharge parameters have complex influence on the electronic behavior. Additionally, the plasma potential is also greatly affected by excitation frequency and power. It rises significantly with the increase of power and first drops and then rises with the increase of frequency. The heating mechanism is discussed by the ratio of stochastic heating to ohmic heating with frequency increase.