Emission spectroscopy of microplasma in Ar/N2
mixture for surface treatment applications
M. Blajan, S. Muramatsu, A. Umeda, K. Shimizu,Innovation and Joint Research Center, Shizuoka University,
3-5-1 Jyouhoku, Hamamatsu, 432-8561, Japan; E-mail：blajanmarius@yahoo.com

Introduction

N2 molecules excited argon neutrals
and reaction in argon plasma with N2
addition:

Microplasma can be found in many
applications. The technology is usedalso for surface treatment and one ofthe discharge gases is argon.
Although there is an interest for
application driven research many ofthe microplasma phenomena are notfullyunderstood.
Emission
spectroscopy is one of the methods toanalyze plasma process .
Microplasma is atmospheric pressure
nonthermal plasma. The aim of thispaper is to analyze the emission
spectrum of the microplasma in argon
gas and in Ar/N2 mixture.

Experimental Setup(1)Microplasma Electrodes
The electrodes consist in perforated
metallic plates covered with adielectric layer.

Ar*+ N2(X1Σg+)v=0 → N2(C3πu)v’=0 + Ar
Spontaneous radiation of formed
excited state of nitrogen:N2(C3πu)v’=0 → N2(B3πg)v’’=0 + hνExperimental setup
Gas flow rate: Ar with purity 99.999%
and Ar/N2 mixture and in N2 at 10L/min.

(4) Electrical Characteristics
Very small discharge gaps andrelatively low discharge voltages(about 1 kV)⇨A high intensity electric field (107108 V/m) assures the formation of
microplasma and a corresponding
discharge current.

(a)Waveforms of the discharge voltage,discharge current and emission signalof microplasma discharge (337.1 nm) inN2 and N2/Ar mixture.
Lifetime emission signal of N2 SPS
peak at 337.1 nm increased at from40 ns to 260 ns when 1% N2 wasadded in Ar.
Emission spectrum in Ar for violet
and red region shows intensity peaksof Ar I.

Microplasma electrodes
Electrode size was 20 mm versus 40mm. Discharge gap was set at 50 μm
in this study.
Emission spectra of microplasma
discharge was observed from the side
part of electrodes.

(a)
(b)

(2) Marx Generator
Capacitors are charged in parallel
connection at voltage V.
⇨ When the MOSFET are turned on
the capacitors are discharge in seriesconnection with an output voltage Vmultiplied with the number ofcapacitors.

Waveforms of the discharge voltage,corresponding discharge current andgate signal for ICCD camera; (a) for
negative pulse; (b) for positive pulse.

Emission Spectroscopy
Emission spectrum of microplasma
discharge in pure N2 shown N2
second positive system band peaks
and N2+ first negative system bandpeaks.

(a)

(b)

Emission spectrum of dry Argon at 1 kV(a), violet region (b), red region.
LIFBASE software was used for thecalculationoftherotationaltemperature.
Tgas = Trot = 300 KN2 SPS

N2 SPS⇨Microplasma=Nonthermal plasma

N2 SPS+VOUT

N2 SPS
N2+ FNS(b)Emission spectrum of N2 at -1.8 kV-VIN

Experimental and simulated spectrum
corresponding to OH peaks emitted bymicroplasma discharge in Ar.

N2 SPS

Positive pulse Marx Generator (a) circuitof Marx Generator, (b) photo of MarxGenerator.
Marx
Generators
with
MOSFET
switches:•Output Voltage: -1.8 kV negative; 1.4
kV positive•Rise time: 80 ns for negative, 100 nsfor positive•Pulse width: 500 ns•Frequency: 1-24 kHz(3) Experimental setup
Emission spectrum was measured bya spectrometer, an ICCD camera and aphotomultiplier
tube.
TheICCD
camera was triggered by a pulse
generator.

N2 SPSN2 SPSOH

N2 SPSN2 SPS

Emission spectrum of 0.1%N2 in Ar at 1.1 kVEmission spectrum in 0.1% N2 in Ar
for UV and Violet region shows:•Intensity peaks between 305 nm and310 nm attributed to OH•N2 second positive band peaks•Small peaks of Ar I at 415.74 nm, 419nm, 420.06 nm, 425.29 nm, 426 nm
and 426.75 nm.

ConclusionsEmission spectrum of microplasma
in Ar/N2 mixture shown intensity
peaks of N2 SPS, Ar I and OH.
•Lifetime emission signal of the 337.1
nm N2 SPS peak for microplasma inAr/N2 shown an increase due to theAr metastable.
•Microplasma discharge in Ar/N2 issuitable forsurface treatment
processes due to the presence ofactivespeciesandlowgas
temperature.