Spatially resolved optical emission spectroscopy investigation of E and H modes in cylindrical inductively coupled plasmas

Spatially resolved optical emission spectroscopy and Langmuir probe measurement are used to investigate the characteristics of a cylindrical inductively coupled plasma in both E and H modes for Ar/N2 discharges. Axial profiles of optical emission intensities are obtained and the results indicate that the electron density becomes non-uniform in the discharge region when the operating mode is changed from the E to the H mode. In the downstream region, electron density in the H mode is lower than that in the E mode, signifying a more lossy nature for the charged species in the E mode than in the H mode. The emission intensities of three argon lines show different behaviours during E to H transition in the downstream region. It is believed that they are due to the difference in contribution to the emission intensity by the metastables in the downstream region in these two modes