Use of an ion energy analyser-mass spectrometer to measure ion kinetic-energy distributions from RF discharges in argon-helium gas mixtures

A mass spectrometer equipped with an electrostatic ion energy analyser has been used to measure the kinetic-energy distributions of ions sampled through an orifice in the grounded electrode of a parallel-plate radio-frequency (RF) discharge cell. Kinetic-energy distributions are presented for Ar⁺, Ar₂⁺ , Ar⁺⁺, He⁺, and ArHe⁺ sampled from argon-helium plasmas with helium concentrations ranging from 0-95 mole percent, applied peak-to-peak RF voltages of 200 V, and gas pressures of 13.3 Pa. Variations in the ion kinetic-energy distributions and ion fluxes observed for different gas mixtures demonstrate the ability of this diagnostic technique to monitor plasma conditions and to investigate the ion kinetic processes occurring in the system