Plasma Generation by Resonant-Cavity Microwave Discharge and Its Applications for Material Processing

A 2.45-GHz-microwave plasma source with a resonant cavity was studied for material processing under medium to atmospheric pressures. Stable plasmas, with electron temperature and density of 1 to 5 eV and beyond the plasma cutoff density, respectively, were efficiently sustained in an ambient pressure of 10-2-10 kPa with hydrogen, helium, nitrogen, argon and a mixture of H2+2H2 (vol. rate). The operational characteristics of coupling efficiency and cavity length depended on gas species. From electric fields measured on the cavity inner wall, the electromagnetic field pattern of TM011 resonance mode was expected to be excited in the cavity over a wide range of operational conditions. In addition, operation of a plasmajet generator, into which the plasma source was modified, diamond film synthesis and surface modification due to atomic oxygen were demonstrated.