A Study on the measurement of individual ion density using floating harmonics probe in two ion species plasmas

Abstract

A method is devised to measure the individual ion density in a plasma in which two types of gas species are mixed. The electron temperature, electron density, and ion saturation current were measured using the electron energy probability function and the floating harmonics probe method to obtain the individual ion density. Experiments are conducted in an argon-helium mixed inductively coupled discharge. As a result of the experiment, the relative density of argon ions increases as the ratio of argon gas increases, and the relative density of argon ions is higher than that of helium in most regions. Compared with the simulation results, each ion appears to enter the sheath at a common velocity. Additionally, the radial distribution of individual ion densities at various pressures and gas ratios is measured. As a result, helium ions have a relatively uniform spatial distribution in all conditions, whereas argon ions are affected by antenna position at high pressure or high argon gas ratio. These results are interpreted as the diffusion of each gas and the change in the maximum ionization region.