Paradoxical electron temperature spatial distribution in a low pressure RF discharge

Summary form only given. Spatially resolved probe measurements of the EEDF (electron energy distribution function) were made along the axial electric field in a capacitively coupled RF discharge at gas pressures between 0.01 and 1.0 Torr in argon. From these measurements the plasma potential, the EEDF and its integrals, such as plasma density and mean electron energy, were found as functions of the axial position x. Essentially divergent trends in the spatial distributions of the effective electron temperature were found at low gas pressures (p <0.1 torr) and at high (p >0.1 Torr) pressures. At low pressures, the effective electron temperature rose at the plasma periphery where the RF electric field was stronger, while at high pressures an opposite effect was found (the electron temperature decreased at the plasma periphery), although electron collisional heating was higher. These patterns of the electron temperature space distribution contradict those expected in the limiting case of high electron thermal conductivity at low pressure, where T/sub e(x)/ is expected to be constant, and in the case of the low thermal conductivity at high pressure, where T/sub e(x)/ should be a local rising function of E/sub (x)/. The paradoxical T/sub e/ distributions found here are due to both the nonlocality effect and a significant departure in the EEDFs from Maxwellian distribution.