ELECTRON-DENSITIES AND TEMPERATURES IN A DIAMOND-DEPOSITING DIRECT-CURRENT ARCJET PLASMA

Langmuir probe measurements of electron density and temperature are ma de in the plume of a de arcjet reactor. A de are is struck in an argon or argon/hydrogen mixture at 6 atm pressure and expands through a con verging/diverging nozzle into the reactor with a pressure of 25 Ton. M ethane and methane/nitric oxide are added in the diverging nozzle, and diamond film grows on a substrate in the gas plume. Electron temperat ures of 1-2 eV are significantly hotter than the neutral gas temperatu re in the plume. Electron densities range from 10(10) to 10(13) cm(-3) , well above the Saha equilibrium for the gas temperature and pressure and well below the equilibrium for the electron temperature. (C) 1997 American Institute of Physics.