Experimental observation of the effect of electron attachment and detachment reactions on the electron energy distribution in an inductive oxygen discharge

Abstract

Electron energy distribution functions (EEDFs) are measured with varying radio-frequency (RF) power in an oxygen inductive discharge. At a pressure of 10 mTorr, the EEDF has a Maxwellian distribution, and the low-energy (1–5 eV) electron temperature, Te,low, monotonically decreases with RF power. However, at a pressure of 100 mTorr, Te,low increases at low RF power (80–150 W) and decreases at high RF power (150–300 W), and the EEDF has a Druyvesteyn-like distribution. These changes in Te,low are attributed to electron attachment and detachment reactions, which are the main creation and loss reactions of negative ions. To investigate this relationship between Te,low and collisional reactions, the reaction coefficients of several reactions are calculated, and the electronegativity (α) is measured with varying RF power. The EEDF is modified by electron attachment and detachment reactions, which lead to a change in Te,low; this modification of EEDF is supported by calculated reaction coefficients and measured α.