Effect of negative-ion flux on ion distribution around a spherical probe in electronegative plasmas

Abstract

The electric potential and the electron- and ion-density profiles near a spherical probe in electronegative plasmas containing negative as well as positive ions are studied. It is shown that for relatively large probe radius and neutral-gas pressure, and/or small electron-to-ion temperature ratio, the density profile of the negative ions can differ from that of Boltzmann if their flux near the probe is outwards. The existence of stationary states is considered and the corresponding maximum negative-ion flux is obtained.