LAUSR

The electron characteristics are investigated in 2 MHz and 13.56 MHz inductively coupled hydrogen discharges with an expansion region. The influence of the gas pressure and radio-frequency of the power source on the electron energy probability functions (EEPFs), electron density, and electron temperature at high deposition power has been presented. The measured EEPFs in the driver region of the discharge evolve from a three-temperature Maxwellian distribution to a Maxwellian distribution as the pressure increases. Different characteristic frequencies calculated based on the measured plasma parameters show that stochastic heating of electrons dominates at pressures lower than 0.3 Pa and it has to be considered for pressures lower than 1.0 Pa, while Ohmic heating dominates at higher pressure. Furthermore, the EEPFs as a function of the total energy evolve from the identical shape to discrete shapes with axial position and pressure, indicating a transition of electron kinetics from nonlocal to local regimes....