E‐ and H‐mode transition in a low pressure inductively coupled ammonia plasma

Abstract

Characteristics of ammonia plasma sustained by inductively coupled radiofrequency discharge has been studied in the range of powers between 50 and 1000 W and pressures between 10 and 90 Pa. In such an experimental setup pronounced differences between the E‐ and H‐mode were observed and explained to some details. Plasma was characterized by optical emission spectroscopy (OES) and residual gas spectrometry (RGA). The plasma luminosity changed for four orders of magnitude and the NH2 band vanished at higher powers (H‐mode). The RGA results indicated high density of NH2 radicals in the E‐mode while in the H‐mode the ammonia molecules almost entirely dissociated to H and N atoms. The N and H atoms created in the plasma recombined to the nitrogen and hydrogen molecules rather than to parent ammonia molecules on the way to the RGA.