The study of influence of working pressure on mode conversion of argon radio-frequency inductively coupled plasma

•The effect of working pressure on mode conversion is studied systematically.•OES and Langmuir probe are effective means to study the parameters of plasma.•ICP discharge mode can appear E-H-E phenomenon with pressure.

Electron temperature and plasma density was measured with change of working air pressure by Langmuir probe at a given power. Radio-frequency (rf) inductively coupled plasma (ICP) discharge mode conversion is determined by optical emission spectrum (OES) with the increase of gas pressure at different power. The results indicate that plasma discharge mode can change from E mode to H mode and spectral intensity appears inverse hysteresis phenomenon with the change of air pressure. The hysteresis width decreases with the increase of power and the hysteresis is no longer present when the power is 420 W and 435 W. Moreover, the jump pressure of E-H transition is gradually reduced with the corresponding increase of discharge power. ICP discharge mode appears E-H-E phenomenon with the increase of air pressure.