Electron heating mode transition induced by mixing radio frequency and ultrahigh frequency dual frequency powers in capacitive discharges
Electron heating mode transitions induced by mixing the low and high frequency power in dual frequency nitrogen discharges at 400 mTorr pressure are presented. As the low frequency (13.56 MHz) power decreases and high frequency (320 MHz) power increases for the fixed power of 200 W, there is a transition of electron energy distribution function (EEDF) from Druyvesteyn to bi Maxwellian type characterized by a distinguished warm electron population. It is shown that this EEDF evolution is attributed to the transition from collisional to collisionless stochastic heating of the low energy electrons.