22P007-O
Analysis of Atmospheric Pressure Plasma Reaction Process
大気圧プラズマの反応プロセスの解析
Katsuhiro Amano, Akihiro Fukae, Masanori Shinohara and Hiroshi Fujiyama
天野勝裕 深江陽大 篠原正典 藤山 寛
Graduate School of Engineering., Nagasaki Univ.
1-14, Bunkyo-machi, Nagasaki 852-8521, Japan.
長崎大学大学院工学研究科〒852-8521

長崎市文教町1-14

It has been investigated that the reaction processes of atmospheric pressure plasma on the surface of the Si
substrate, with the infrared spectroscopy in multiple internal reflection geometry (MIR-IRAS). The infrared
spectra indicated that the quantity of OH-group on the surface of Si substrate was increased with the plasma
exposure.

1. Introduction
The atmospheric pressure plasma has advantages
that the plasma can be generated without vacuum
system at low costs. The atmospheric pressureplasma is used in various fields such as medical
field, environment field and so on. This is because
the atmospheric pressure plasma has abilities of theantiseptic effect, the surface reformation andetc…However, it has not been understood that what
has happened in process of the reaction. In order toextend application of the atmospheric pressureplasma, an understanding of the mechanism of thereaction is required.
2. Experiment
Figure 1 is the image of experimental set up usedin this study. This set up contains Dielectric Barrier
Discharge type atmospheric plasma source .The
atmospheric plasma was generated in the air, using
10kHz high voltage power source.
Changes in the chemical states during the plasma
exposure
weremonitored
withinfrared
spectroscopy in multiple internal reflection
geometry (MIR-IRAS).
Si prisms for MIR-IRAS were used as thesubstrate of this study. The substrate was set
downward the electrode of DBD.
The Si prisms were made of n-type Si (100)wafers. The prisms had a dimension of
0.5×10×40mm, with mirror-polished 45° bevels oneach of the short edges. The prism was treated withconventional RCA cleaning to remove surface
contamination.
In order to investigate the plasma exposure
process due to the surface condition, the two typesof surface conditions were prepared. One is thechemical oxide covered surface, produced in boiled
H2SO4/H2O2 solution. The other is hydrogenterminated surface lined with HF solution.

Fig.1 Experimental equipment

Fig.2 Dimension of Si substrate3. Result and Discussions
Figure 3 shows the infrared spectra of thechemical oxide covered Si substrate, exposed to theatomspheric plasma at different exposure times. The
infrared spectra have broad peak located between
3000 and 3600cm-1. This peak is assigned to O-H
stretching mode. The results showed that theamount of OH-group on the substrate surface wasincreased with the plasma exposure time.
Figure 4 shows the infrared spectra of theHF-treated Si substrate, exposed to the atomsphericplasma at different exposure times. In this graphOH peak was also observed, but the intenstiy wasweak, compared with the oxide-covered surface.
The adsorption of OH species generated in theatmospheric plasma was seppressed on theHF-treated Si surface. which indicates hydrophobic
property.
Thereby, it is suggested that H2O was generated
in DBD-type atmopheric plasma in the air.

Fig.3 Infrared absorption spectra of the Si
substrate covered chemical oxides

4. Conclusion
The chemical species on Si substrate during
DBD-type atmospheric plasma exposure wasobserved with infrared spectroscopy in multiple
internal reflection geometry (MIR-IRAS).
OH-group was observed on Si surface during
plasma exposure. The amount of OH-group on thesurface of the Si substrate was increased as timeadvances. Thereby, it is suggested that H2O wasgenerated in DBD-type atmopheric plasma in theair.
Acknowledgments
This research was partially supported by aGrant-in-Aid for challenging Exploratory Research
No. 2365403 (2011.4-2013.3) from Japan Society
for the Promotion of Science (JSPS).

Fig.4 Infrared absorption spectra of the Si
substrate covered with hydrogen