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.

Atmospheric pressure plasma treatments have attracted attention for various application processes. The effect of O2 additions below 0.2% to N2 was investigated for the efficiency of removing organic contaminants on a glass surface using nonequilibrium atmospheric-pressure pulsed plasma. A remarkably high efficiency of cleaning was obtained by a plasma treatment with ca. 0.03% O2 additions to N2. The concentration of ozone (O3) and the ground-state oxygen radical [O(P32)] were measured using ultraviolet absorption spectroscopy and vacuum ultraviolet laser absorption spectroscopy, respectively. It was found that the key factors for surface cleaning were the scission of carbon bonds due to ultraviolet irradiation and subsequent oxidation due to O(P3), and that the surface cleaning proceeded in broad areas due to the photodissociation of O3.