We produced a nonequilibrium atmospheric pressure plasma by applying an alternative current between two electrodes. The gas temperature and electron density were evaluated using optical emission spectroscopy. It was found that the plasma had gas temperatures from 1800to2150K and ultrahigh electron densities in the order of 1016cm−3. A remarkably high oxygen radical concentration of 1.6×1015cm−3 was obtained at a 1% O2∕Ar gas flow rate of 15slm (standard liters per minute). Contact angles below 10° were obtained in the process of glass cleaning with a plasma exposure time of 23ms.

A non-equilibrium atmospheric pressure plasma jet excited by 60-Hz ac power was diagnosed by laser Thomson and laser Raman scattering. We obtained the spatial distributions of the electron density, electron temperature, and gas temperature. The results show that the plasma can generate an electron density of up to 1021 m-3, an electron temperature of approximately 1 eV, and a gas temperature as low as approximately 700 K, indicating that the plasma is in the non-equilibrium state. The laser scattering diagnostic method and the obtained data are useful in the application of the non-equilibrium atmospheric pressure plasma jet.

A 60 Hz alternating current excited atmospheric-pressure plasma with an ultrahigh electron density of over 1016 cm-3 employing H2/Ar [ p(H2)/p(H2+Ar) 1–3%] gases was used to reduce copper oxides on copper. The remote plasma reduced CuO and Cu2O at room temperature. The ground-state hydrogen (H) radical density in the atmospheric-pressure plasma was measured by vacuum ultraviolet absorption spectroscopy using a micro hollow cathode lamp. The ratio of reduction of amount of CuO flux to the H radical flux was determined from the measured H radical density and gas temperature.

A hydrophobic organics surface selectively against glass was realized by employing nonequilibrium atmospheric-pressure pulsed plasmas with a mixture of CF 4 and N 2 gases. The organic surface was drastically altered to have a high hydrophobicity, while the glass surface itself remained hydrophilic after the plasma treatment with the addition of a small amount of CF 4 to the N 2 gas. After 100 CF 4 / N 2 plasma treatments, no thin film deposition was observed on the organic material. To investigate the characteristics of the CF 4 / N 2 plasma, the exhaust gas from the plasma was measured by using ion attachment mass spectroscopy ͑IAMS͒. The IAMS spectrum indicated that the amounts of CF 3 and F radicals were increased drastically with increasing addition of CF 4 . A mechanism of the selective surface modification was clarified on a result of surface chemical bonding with the gas phase.

A surface modification process on the contact lens using a nonequilibrium atmospheric pressure remote plasma excited by three-phase AC power source has been investigated. Two dimensional spatial distributions of optical emissions of Ar and OH were measured, and gas temperature and electron density were estimated using the optical emission spectroscopy. It has been found that the gas temperature in the upstream region of the remote plasma is lower than that in the downstream region due to the interfusion of ambient air. The heat-sensitive material such as plastic could be processed without thermal damage by the nonequilibrium atmospheric pressure remote plasma in the proper low-temperature region.