We present the effects of the application of a nonthermal plasma jet to a liquid surface on H2O2 and NO2− generation in the liquid. Two distinct plasma irradiation conditions, with plasma contact and with no observable plasma contact with the liquid surface, were precisely compared. When the plasma was made to touch the liquid surface, the H2O2 concentration of the plasma-treated water was much higher than the NO2− concentration. In contrast, when no observable contact of the plasma with the liquid surface occurred, the ratio of the NO2− to H2O2 concentration became over 1 and NO2− became more dominant than H2O2 in the plasma-treated water. Our experiments clearly show that reactive oxygen and nitrogen species can be selectively produced in liquid using appropriate plasma-irradiation conditions of the liquid surface. The ratio of NO2− to H2O2 was controlled within a wide range of 0.02–1.2 simply by changing the plasma-irradiation distance from the liquid surface.

We present the development of a low-frequency nonthermal plasma-jet system, where the surrounding-gas condition of the plasma jet is precisely controlled in open air. By restricting the mixing of the ambient air into the plasma jet, the plasma jet can be selectively changed from a N2 main discharge to an O2 main discharge even in open air. In the plasma-jet system with the controlled surrounding gas, the production of reactive oxygen and nitrogen species is successfully controlled in deionized water: the concentration ratio of NO2 − to H2O2 is tuned from 0 to 0.18, and a high NO2 − concentration ratio is obtained at a N2 gas ratio of 0.80 relative to the total N2/O2 gas mixture in the main discharge gas. We also find that the NO2 − concentration is much higher in the plasma-activated medium than in the plasma-activated deionized water, which is mainly explained by the contribution of amino acids to NO2 − generation in the medium.

Plasma technologies for meters‐scale flat‐panel‐display (FPD) processing have been developed using multiple low‐inductance antenna (LIA) modules to drive inductively coupled plasmas (ICPs), in which RF‐power‐deposition profiles can be controlled in plasma reactors with a scale as large as meters. The LIA module consisted of a U‐shaped internal antenna with dielectric isolation, each of which was coupled to an RF power system for independent power control of driving ICP. Our new proposal of the unique source configuration is based on the principle of multiple operation and integrated control of LIA modules, which allow low‐voltage high‐density plasma production with active control of power deposition profiles. Multiple LIA modules mounted on the wall of a discharge chamber were independently controlled to attain the desired plasma profiles. Experiments with a meter‐scale rectangular reactor resulted in stable source operation to attain high densities >1011 cm−3. Plasma‐enhanced chemical vapor deposition of amorphous hydrogenated carbon films showed an excellent control capability of film‐thickness distributions to achieve the film‐thickness uniformity of 8.6%, which was defined as the value of (maximum thickness − minimum thickness) divided by the average thickness over the substrate area of 410 mm × 520 mm. The obtained results indicate that the plasma production and/or control technologies with the LIA modules are quite attractive as a high‐density low‐potential plasma source for a variety of FPD processes.

We have developed a cylindrical RF plasma source by the inductive coupling of multiple low-inductance antenna (LIA) units and analyzed the plasma density profile of this source using fluid simulation. Experiments using four LIA units showed a stable source operation even at 2000 W RF power, attaining plasma densities as high as 1011–1012 cm-3 in an argon pressure range of 0.67–2.6 Pa. The amplitude of antenna RF voltage was measured to be less than 600 V, which is considerably smaller than those obtained using conventional ICP antennas. The radial distribution of plasma density sustained using four LIA units showed excellent agreement with profiles numerically predicted using a fluid-simulation code.

We present here analysis of oxidation reaction in liquid by a plasma-jet irradiation under various gas flow patterns such as laminar and turbulence flows. To estimate the total amount of oxidation reaction induced by reactive oxygen species (ROS) in liquid, we employ a KI-starch solution system, where the absorbance of the KI-starch solution near 600 nm behaves linear to the total amount of oxidation reaction in liquid. The laminar flow with higher gas velocity induces an increase in the ROS distribution area on the liquid surface, which results in a large amount of oxidation reaction in liquid. However, a much faster gas flow conversely results in a reduction in the total amount of oxidation reaction in liquid under the following two conditions: first condition is that the turbulence flow is triggered in a gas flow channel at a high Reynolds number of gas flow, which leads to a marked change of the spatial distribution of the ROS concentration in gas phase. Second condition is that the dimpled liquid surface is formed by strong gas flow, which prevents the ROS from being transported in radial direction along the liquid surface.