23G09
Three dimensional investigation of activated species
in O2/Ar nonequilibrium atmospheric pressure plasma
O2/Ar非平衡大気圧プラズマにおける活性種の3次元気相反応解析
Masanori Kato, Keigo Takeda, Kenji Ishikawa Makoto Sekine and Masaru Hori et al.
加藤 正規, 竹田 圭吾，石川 健治，関根 誠，堀 勝 他
Dept. of Electrical Engineering and Computer Science, School of Engineering Nagoya Univ.
Furo-cho, Chikusa-ku, Nagoya 464-8603, Japan
名古屋大学 大学院工学研究科 電子情報システム専攻〒464-8603 名古屋市千種区不老町
In this research, three-dimensional gase phase diagnosis of the atmospheric pressure plasma that generated in nitrogen
atmosphere was performed. Atomic oxygen radical density and ozone density were measured. Oxygen density wasmeasured by Vacuum Ultra Violet Absorption Spectroscopy (VUVAS) and ozone density was measured by Ultra Violet
Absorption Spectroscopy (UVAS). For three-dimensional measurement, the plasma source was moved in the directionof the gas stream (Z) and the direction of the diameter from the gas stream center (R).

1 Background
Nonequilibrium atmospheric pressure plasma, canachieve extremely high plasma density comparedwith low pressure plasma. Therefore, it has apotential for higher speed processing than low
pressure plasma. Moreover, plasma-exposure liquid
or living processes which are impossible at low
pressure condition become possible because it isenable us to generate under the condition of
atmospheric pressure. The activated species such as
atomic or molecular radicals, excited molecules andso on are deeply related to the performance of theseplasma processes. So it is necessary to understandand control the behavior of radical in the plasma
process for realizing the more high performance.
But the density distributions of activated species
in atmospheric pressure plasma are localized,
because the recombination and quenching effects
are more higher compared with those at low
pressure. Moreover, the atmospheric pressureplasma processes are generally carried out in theremote plasma region. Therefore, for understanding
the spatial distributions of radicals in atmosphericpressure plasma process, we have to consider about
the recombination and transportation of radicals
with gas stream. In this study, it was considered
about the transportation of activated species by gas
flow and a chemical reaction in gas phase based on
the quantitatively-measured results.
2. Experimental
In this study, atmospheric pressure plasma wasgenerated by introducing the gas from the gas
nozzle of 1 mm in the inside diameter between theopposite electrode that were impressed 60 Hz

high voltage. Atomic O radical and O3 distribution

in the nonequilibrium atmospheric pressure plasma
was examined by various gas flow rates. Atomic O
radical density was measured by using vacuum
ultra-vioret absorption spectroscopy(VUVAS)[1,2],
and O3 density was measured by using ultra-vioret
absorption spectroscopy(UVAS)[3]. The xenon
lamp and micro hollow cathode lamp were used as
UV source and VUV source. For the three
dimensional measurement the plasma source wasable to be move to the probes. The plasma source
was moved in the direction of the gas stream (Z)and the direction of the diameter from the gas
stream center (R).
3.Result
Figure 1 shows the O radical density as afunction of the distance from electrode to probe
center. The O radical density has been 4.1×1014 cm-3
at the gas flow rate of 1.0 slm and the distance fromelectrode to probe center of 10 mm. The O radicaldensity was decreased with increasing of thedistance from electrode to probe center (Z). And theamount of a decrease of the radical to the distance
grows when flow rate is small.
Figure 2 shows the O3 density as a function of thedistance from electrode to probe center. The O3
density has been 1.6×1014 cm-3 at the gas flow rateof 1.0 slm and the distance from electrode to probe
center of 37 mm. The O3 density was increased withthe value of Z.
The chemical reason for reduction of atomic
oxygen radical is considered because the atomic
oxygen radicals became ozone or oxygen molecules
by a reaction with the oxygen molecules or ozone inReference

O + O2 → O3
O3 + O → 2O2
However, the activated species in oxygen plasma
exist besides atomic O radical and ozone, and thesespecies are related also to a reaction with an atomic
O radical and ozone. More detailed plasma
diagnosis is required to get to know the details ofoxygen plasma. Moreover, it is necessary to take
into consideration density change of the particles
resulting from diffusion. At the presentation I willtalk about this topics.

[1] Hisao Nagai, Mineo Hiramatsu, Masaru Hori, andToshio Goto: Rev. Sci. Instrum., 74(7) (2003)[2] Hirotoshi Inui, Keigo Takeda, Hiroki Kondo, KenjiIshikawa, Makoto Sekine, Hiroyuki Kano, Naofumi
Yoshida, and Masaru Hori: J. Appl. Phys. Express 3126101(2010)[3] L. T. Molina and M. J. Molina: F. Geophys. Res.
91(D13), 14,501-14,508 (1986)

10151014

1013-3O Radical Density (cm )gas as follow.

1.0slm2.0slm3.0slm4.0slm5.0slm7101316Z (mm)-3ozone density (cm )Fig. 1 atomic O radical density as a function of
the distance from electrode to probe center

141013

1 slm
2 slm
3 slm
4 slm
5 slm

10121002040

60Z (mm)80

Fig. 1 Ozone density as a function of
the distance from electrode to probe center100