Optical emission diagnostics of permanent and pulsed microwave discharges in H-2-CH4-N-2 for diamond deposition

A microwave plasma of H-2-CH4-N-2 gas mixture used for diamond film deposit ion has been characterized by optical emission spectroscopy in the continuo us and in the pulsed modes. In the continuous mode? a dynamic form of actin ometric optical emission spectroscopy was used to determine temporal trends in the concentrations of H, CH and CN species following the cut-off of eit her the CH, or Nz flows. These data show that the gas-phase reactions play a major role in the production of the above-mentioned species, but also the plasma-diamond surface reactions contribute significantly to the productio n of the CN radical. In the pulsed-discharge mode, time-resolved optical em ission spectroscopy was used to determine the evolution of the relative con centrations of reactive species H, CH, CN and Ar with time. This evolution during the discharge, post-discharge and transient stages gives information on the processes leading to the population of excited states. (C) 1999 Els evier Science S.A. All rights reserved.