Pulsed Power Microplasma Diagnostics for
Glass’Surface Treatment
Marius Blajan, Akira Umeda and Kazuo Shimizu
Innovation and Joint Research Center, Shizuoka University,
3-5-1 Jyouhoku, Hamamatsu, 432-8561, JAPAN; E-mail：blajanmarius@yahoo.com

Introduction
Microplasma
canbefoundinmanyapplications. In the last years, the technology
was used in applications such as NOx removal,
surfacetreatment
andsterilization
orinactivation
ofbacteria.
Emission
spectroscopy is one of the methods to analyze
plasma process and will allow the calculationof microplasma’s electron, vibrational androtational temperatures.
The aim of this research is to analyze
microplasma by emission spectroscopy for theprocess of glass surface treatment. Other
research groups investigated nonthermal
plasma for surface treatment with similar
characteristics such as high electron, and low
rotational temperatures which recommends
that this technology could be applied for thesurface modification due to its low gas
temperature and molecular excitation ability.
Our microplasma has this characteristics
obtained at relatively low discharge voltages
around 1 kV which can be advantageous infurthermore implementing the technology inindustry. Moreover the surface potential after
the microplasma treatment is low (about 20V) comparing with plasma jet that charges thesurface at more than 200 V.

N2 molecules excited argon neutrals andreaction in argon plasma with N2 addition:
Ar*+ N2(X1Σg+)v=0 → N2(C3πu)v’=0 + Ar
Spontaneous radiation of formed excitedstate of nitrogen:N2(C3πu)v’=0 → N2(B3πg)v’’=0 + hν(a)(b)

Experimental setup: (a) emission spectroscopy;(b) surface treatment.

(4) Electrical Characteristics

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

Very small discharge gaps and relatively low
discharge voltages (about 1 kV)⇨A high intensity electric field (107-108 V/m)assures the formation of microplasma and acorresponding discharge current.

(a)Waveform of the discharge voltage, discharge
current and emission signal of microplasma
discharge in 1% N2 in Ar and in N2.
Lifetime emission signal of N2 SPS peak at337.1 nm increased from 60 ns to about 500
ns when 1% N2 was added in Ar.
Vibrational temperature was Tvib=3160 K.
Electron temperature was Te = 23000 K.
Rotational temperature Tgas = Trot = 300 K.
⇨Microplasma=Nonthermal plasma(b)

Surface Treatment of Glass

Waveforms of the discharge voltage, corresponding
discharge current and gate signal for ICCD camera:(a) Marx Generator; (b) Neon transformer.

A neon transformer was used to energize theelectrodes at 1.3 kV. With the increase oftreatment
time
thecontact
angle
isdecreasing from 41.5°without treatment to8.5°after 30 seconds.
45Emission Spectroscopy

Microplasma electrodes
Electrode size was 20 mm versus 40 mm foremission spectroscopy analysis. Discharge gap
was set at 50 μm in this study.
Microplasma electrodes for surface treatment
have 40 mm diameter .

Emission spectrum was measured
camera shutter opened for 1 µs.

18000

Intensity (a.u.)Marx Generator with MOSFET switches:•Output Voltage: -2 kV negative•Rise time: 100 ns•Pulse width: 1 µs
•Frequency: 1-24 kHz
Neon transformer•Output voltage: up to 2 kV AC•Frequency 24 kHz

0.5% N2 in Ar at 1.3 kV3530252015105(a)

16000
14000

(2) Power Supplies

withContact angle (deg.)

40Ar I

0Ar I

01200010000

5101520253035Treatment time (sec.)

Ar I

8000
6000

Ar I

Contact angle of a water droplet at the surface ofglass versus treatment time by microplasma
discharge in 0.5 % N2 in Ar.

Ar I

4000
2000

Before treatment

0410

415

420

425

430

435

After treatment

440

Wavelength (nm)

18000
16000

+V
Intensity (a.u.)

14000

Trigger

Ar
0.5% N2 in Ar(b) N SPS
2N SPS
212000N2 SPS

10000
8000
6000
4000

N2 SPSOHN2 SPS

2000

Vout

0280 300 320 340 360 380 400 420 440 460 480 500

Photo of negative pulse Marx Generator.

Wavelength (nm)Emission spectrum of microplasma in: (a) Ar;(b) N2/Ar at -1.2 kV.

(3) Experimental setup
Emission spectrum wasspectrometer, an ICCD
photomultiplier tube.

measured bycamera andaa

A microplasma enclosed reactor was used forsurface treatment of glass. A contact angle
meter was used to measure the contact angleof a water droplet at the surface of glass.
Gas flow rate: Ar and N2/Ar at 10 L/min.

Contact angle of a water droplet at the surface ofglass before and after microplasma treatment..

Emission spectrum in Ar and Ar/N2 shows:•N2 second positive band system peaks at
315.9, 337.1, 357.7, 380.4, 400 and 405 nm.
•N2+ first negative band system peak at
391.4 nm.
•OH peaks at 306.4, 307.8 and 308.9 nm.
•Ar I peaks were measured at 415.8, 419.1,419.8, 420.1, 426.6, 427.2, 425.9, 433.3,696.5, 706.7, 727.3, 738.3; 703.2, 750.4 and772.4 nm.

Conclusions•Emission spectrum of microplasma shown
intensity peaks of N2 SPS and N2+ FNS, OHand ArI.
•Lifetime emission signal peak of the 337.1
nm N2 SPS peak for microplasma in N2 was
60 ns and about 500 ns when 1% N2 wasadded in Ar.
•Temperatures of microplasma: Trot = 300 K;
Tvib = 3160 K; Te = 23000 K  thistechnology could be applied for the surface
modification due to its low gas temperatureand molecular excitation ability obtained atabout 1 kV.
•The contact angle of a water droplet at asurface of the glass panel decreased aftermicroplasma
treatment
from
41.5°to8.5°after 30 seconds. This recommends
microplasma as a solution for the surface
treatment of glass panels used in electronic
industry.